JP2009146995A - Magnetic memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic memory device capable of performing a high-reliability writing operation. <P>SOLUTION: Each of write lines WT has a portion in which a planar shape extends along a write line center axis CWT, with the write line center axis CWT as a center line. each of bit lines BL has a portion in which a planar shape extends along a bit line center axis CBL, with the bit line center axis CBL crossing the write line center axis CWT as a center line. A recording layer 3 has a planar shape asymmetric with respect to a magnetization-easy axis. The distance between the barycenter GP of the planar shape of the recording layer 3 and a crosspoint AP of the write line center axis CWT, and the bit line center axis CBL is smaller than the distance between the rectangular barycenter DP circumscribing the planar shape of the recording layer 3 and the crosspoint AP. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic memory device, and more particularly to a magnetic memory device using a magnetoresistive effect element.

  The magnetoresistive (MR) effect is a phenomenon in which electric resistance changes when a magnetic field is applied to a magnetic material, and is used in magnetic field sensors, magnetic heads, and the like. In particular, Non-Patent Documents 1 and 2 introduce artificial lattice films such as Fe / Cr and Co / Cu as giant magnetoresistance (GMR) effect materials that exhibit a very large magnetoresistance effect.

  In addition, a magnetoresistive effect element using a laminated structure composed of a ferromagnetic layer / nonmagnetic layer / ferromagnetic layer / antiferromagnetic layer having a nonmagnetic metal layer thick enough to eliminate exchange coupling action between ferromagnetic layers has been proposed. ing. In this element, the ferromagnetic layer and the antiferromagnetic layer are exchange-coupled, the magnetic moment of the ferromagnetic layer is fixed, and only the spin of the other ferromagnetic layer can be easily reversed by an external magnetic field. Yes. This is an element known as a so-called spin valve film. In this element, since the exchange coupling between the two ferromagnetic layers is weak, the spin can be reversed with a small magnetic field. Therefore, the spin valve film can provide a magnetoresistive element having higher sensitivity than the exchange coupling film. As the antiferromagnetic material, FeMn, IrMn, PtMn, or the like is used. This spin valve film is used in a reproducing head for high-density magnetic recording, and when used, a current flows in the in-plane direction of the film.

  On the other hand, Non-Patent Document 3 shows that a larger magnetoresistive effect can be obtained by using the perpendicular magnetoresistive effect in which current flows in a direction perpendicular to the film surface.

  Further, Non-Patent Document 4 also shows a tunneling magneto-resistive (TMR) effect due to a ferromagnetic tunnel junction. This tunneling magnetoresistance is achieved by making the spins of the two ferromagnetic layers parallel or antiparallel to each other in a tunnel layer in the direction perpendicular to the film surface by an external magnetic field in a three-layer film comprising a ferromagnetic layer / insulating layer / ferromagnetic layer. This is based on the fact that the magnitude of the current is different.

  In recent years, researches using GMR and TMR elements in nonvolatile magnetic memory semiconductor devices (MRAM: magnetic random access memory) have been shown, for example, in Non-Patent Documents 5-7.

  In this case, a pseudo spin valve element or a ferromagnetic tunnel effect element in which a nonmagnetic metal layer is sandwiched between two ferromagnetic layers having different coercive forces has been studied. When used in an MRAM, these elements are arranged in a matrix, and a magnetic field is applied by passing a current through a separately provided wiring. The two magnetic layers constituting each element are parallel and antiparallel to each other. By controlling this, “1” and “0” are recorded. Reading is performed using the GMR or TMR effect.

  Since the power consumption is lower when the TMR effect is used than when the GMR effect is used, the use of the TMR element is mainly studied in the MRAM. In the MRAM using the TMR element, the MR change rate is as large as 20% or more at room temperature and the resistance at the tunnel junction is large, so that a larger output voltage can be obtained. In addition, in an MRAM using a TMR element, it is not necessary to perform spin inversion at the time of reading, and reading can be performed with a small current. Therefore, the MRAM using the TMR element is expected as a low power consumption type nonvolatile semiconductor memory device capable of high-speed writing / reading.

  In the write operation of the MRAM, it is desired that the magnetic characteristics of the ferromagnetic layer in the TMR element be controlled. Specifically, a technique for controlling the relative magnetization directions of two ferromagnetic layers sandwiching a nonmagnetic layer to be parallel and antiparallel, and magnetization reversal of one magnetic layer in a desired cell reliably and efficiently Technology is desired. A technique for controlling the relative magnetization directions of two ferromagnetic layers sandwiching a nonmagnetic layer to be parallel and antiparallel uniformly in the film plane using two intersecting wirings is disclosed in, for example, Patent Documents 1, 3, 4 Is shown in

  According to Patent Document 3, an MRAM memory cell requires two wiring layers that intersect, a magnetic memory element, a transistor element, and a connection member that electrically connects the magnetic memory element and the transistor element. The The magnetic memory element has a recording layer which is a ferromagnetic material, a pinned layer, and a nonmagnetic layer sandwiched between the recording layer and the pinned layer.

  In the MRAM, when the cell is miniaturized for high integration, the reversal magnetic field increases due to the demagnetizing field depending on the size of the magnetic layer in the film surface direction. This requires a large magnetic field at the time of writing and increases power consumption. For this reason, as shown in Patent Documents 2, 5, and 6, techniques for optimizing the shape of the ferromagnetic layer and facilitating magnetization reversal have been proposed.

This magnetization reversal is selectively performed on the recording layer of a specific magnetic memory element by a combined magnetic field generated by current flowing through both of the two intersecting wiring layers selected. At this time, if the shape of the recording layer in the magnetic memory element is symmetric with respect to the hard axis and asymmetric with respect to the easy axis, the magnetic field range that can be used for rewriting can be expanded. It is disclosed in Patent Documents 5 and 6.
DH Mosca et al., "Oscillatory comprising coupling and giant magnetoresistance in Co / Cu multilayers", Journal of Magnetism and Magnetic Materials 94 (1991) pp.L1-L5 SSP Parkin et al., "Oscillatory Magnetic Exchange Coupling through Thin Copper Layers", Physical Review Letters, vol.66, No.16, 22 April 1991, pp.2152-2155 WP Pratt et al., "Perpendicular Giant Magnetoresistances of Ag / Co Multilayers", Physical Review Letters, vol.66, No.23, 10 June 1991, pp.3060-3063 T. Miyazaki et al., "Giant magnetic tunneling effect in Fe / Al2O3 / Fe junction", Journal of Magnetism and Magnetic Materials 139 (1995), pp.L231-L234 S. Tehrani et al., "High density submicron magnetoresistive random access memory (invited)", Journal of Applied Physics, vol.85, No.8, 15 April 1999, pp.5822-5827 SSP Parkin et al., "Exchange-biased magnetic tunnel junctions and application to nonvolatile magnetic random access memory (invited)", Journal of Applied Physics, vol.85, No.8, 15 April 1999, pp.5828-5833 ISSCC 2001 Dig of Tech. Papers, p.122 Japanese Patent Laid-Open No. 11-273337 JP 2002-280637 A JP 2000-353791 A US Pat. No. 6,005,800 JP 2004-296858 A US Pat. No. 6,570,783 Japanese Patent Laying-Open No. 2005-310971

  Consider a case where a large number of magnetic memory elements are arranged in a matrix. At this time, in the conventional MRAM, the vicinity of the center of the intersecting portion of the two wiring layers intersecting each other and the position of the center of gravity of the rectangular shape circumscribing the planar shape of the recording layer of the magnetic memory element substantially coincide in plan view. Are arranged as follows.

  When the recording layer is arranged in this way, there is a problem that the wiring current required for magnetization reversal greatly fluctuates when the recording layer is displaced due to manufacturing process variations or the like. As a result, the magnetic field range in which the selective writing operation can be surely performed on a specific magnetic memory element is narrowed, so that the reliability of the writing operation is lowered.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic storage device capable of performing a highly reliable write operation.

  The magnetic memory device in the present embodiment has a substrate, first and second wirings, and a magnetic memory element. The first wiring is provided on the substrate and has a planar shape extending along the first axis with the first axis as the central axis. The second wiring is provided on the substrate and has a portion extending along the second axis with the second axis having a planar shape intersecting the first axis as a central axis, and is spaced from the substrate in the thickness direction. Crosses the first wiring. The magnetic memory element includes a recording layer and a pinned layer, and at least a portion is sandwiched between the first and second wirings in a region where the first and second wirings cross each other with a space therebetween. The recording layer has an easy magnetization axis, and the planar shape is asymmetric with respect to the easy magnetization axis. The pinned layer has a fixed magnetization direction. The distance between the center of gravity of the planar shape of the recording layer and the intersection is smaller than the distance between the center of gravity of the rectangle circumscribing the planar shape of the recording layer and the intersection of the first and second axes.

  According to the magnetic memory device of the present embodiment, the variation of the magnetization reversal current due to the displacement of the relative position between the recording layer and the wiring layer is suppressed, so that the magnetic memory element to be written can be selected more. Since it is performed reliably, a highly reliable writing operation can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Circuit and structure of memory cell)
First, a circuit of a memory cell of a magnetic storage device will be described with respect to the magnetic storage device in the embodiment of the present invention.

  FIG. 1 is a circuit diagram of a memory cell of a magnetic memory device according to an embodiment of the present invention. Referring to FIG. 1, in the magnetic memory device, one memory cell MC (within a dotted frame) is composed of an element selection transistor TR and a magnetic memory element (ferromagnetic tunnel junction element) MM. A plurality of memory cells MC are formed in a matrix.

  A write line WT and a bit line BL for rewriting and reading information intersect the magnetic memory element MM. The write line WT extends along the magnetic memory elements MM arranged in one direction (for example, a column), but is not electrically connected to the magnetic memory elements MM. The bit line BL is electrically connected to one end side of each of the magnetic memory elements MM arranged in the other direction (for example, a row).

  The other end side of the magnetic memory element MM is electrically connected to the drain side of the element selection transistor TR. The gates of the plurality of element selection transistors TR arranged side by side in one direction are electrically connected to each other by a word line WD. The source sides of the plurality of element selection transistors TR arranged side by side in the other direction are electrically connected by the source line SL.

Next, the structure of the magnetic memory device in this embodiment will be described.
FIG. 2 is a schematic cross-sectional view showing the configuration of the magnetic memory device according to one embodiment of the present invention. Referring to FIG. 2, in memory cell region MR in semiconductor substrate 11, element selection transistor TR is formed on the surface of the element formation region partitioned by element isolation insulating film 12 (the surface of semiconductor substrate 11). The element selection transistor TR mainly has a drain region D, a source region S, and a gate electrode body G. The drain region D and the source region S are formed on the surface of the semiconductor substrate 11 at a predetermined distance from each other. The drain region D and the source region S are formed from impurity regions having a predetermined conductivity type. The gate electrode body G is formed on a region sandwiched between the drain region D and the source region S with a gate insulating film GI interposed therebetween. The side wall of the gate electrode body G is covered with a sidewall-like side wall insulating film SI.

  An interlayer insulating film 13 is formed so as to cover the element selection transistor TR. The interlayer insulating film 13 is provided with a hole reaching the drain region D from its upper surface. A connecting member 14 is formed in the hole. An interlayer insulating film 15 is formed on the interlayer insulating film 13. In the interlayer insulating film 15, a hole reaching the connection member 14 from the upper surface and a hole reaching the interlayer insulating film 13 are formed. A light line WT and a connection member 16 are formed in each of these holes. The connecting member 16 is electrically connected to the drain region D by the connecting member 14.

  An interlayer insulating film 17 is formed on the interlayer insulating film 13 so as to cover the write line WT and the connection member 16. The interlayer insulating film 17 is provided with a hole reaching the connecting member 16 from the upper surface thereof. A connecting member 18 is formed in the hole. A conductive layer 19 and a magnetic memory element MM are formed on the interlayer insulating film 17. The conductive layer 19 is electrically connected to the drain region D by connection members 18, 16, and 14.

  The magnetic memory element MM is a magnetoresistive element, and includes a pinned layer 1, a tunnel insulating layer 2 that is a nonmagnetic layer, and a recording layer 3, which are stacked in order from the bottom. The fixing layer 1 is formed in contact with the conductive layer 19.

  A protective film 20 is formed so as to cover the magnetic memory element MM, and an interlayer insulating film 21 is formed on the protective film 20. The protective film 20 and the interlayer insulating film 21 are provided with holes reaching the recording layer 3 through the films 20 and 21. A connecting member 23 is formed in the hole. A bit line BL is formed on the interlayer insulating film 21. The bit line BL is electrically connected to the magnetic memory element MM by the connection member 23.

  An interlayer insulating film 26 is formed so as to cover the bit line BL. A predetermined wiring layer 29 and insulating layer 28 are formed on the interlayer insulating film 21.

  On the other hand, in the peripheral (logic) circuit region RR in the semiconductor substrate 11, a transistor TRA that forms a logic circuit is formed. The transistor TRA includes a pair of source / drain regions S / D formed on the surface of the semiconductor substrate 11 at a predetermined distance from each other, and a region sandwiched between the pair of source / drain regions S / D. And a gate electrode G formed through the gate insulating film GI. The sidewall of the gate electrode G is covered with a sidewall-like sidewall insulating film SI.

  On this transistor TRA, predetermined wiring layers 16, 25, 29, connection members 14, 23, 27 for electrically connecting the respective wiring layers 16, 25, 29, interlayer insulating film 13, 15, 17, 21, 24, 26, and 28 are formed.

Next, the structure of the memory cell will be described in more detail.
FIG. 3 is a perspective view schematically showing a configuration in the vicinity of the magnetic memory element MM. Referring to FIG. 3, magnetic storage element MM that is magnetized as information is sandwiched between write line WT and bit line BL from above and below in a region where write line WT and bit line BL intersect. Has been placed. The magnetic memory element MM has a laminated structure of a fixed layer 1, a tunnel insulating layer 2, and a recording layer 3, for example. In the pinned layer 1, the magnetization direction is fixed. In the recording layer 3, the magnetization direction is changed by injection of a magnetic field generated by a current flowing through a predetermined wiring (for example, the bit line BL) or spin-polarized electrons.

  As shown in FIG. 2, the pinned layer 1 of the magnetic memory element MM is electrically connected to the drain region D of the element selection transistor TR via the conductive layer 19 and the connection members 18, 16, and 14. On the other hand, the recording layer 3 side of the magnetic memory element MM is electrically connected to the bit line BL via the connection member 23.

  FIG. 4 is a cross-sectional view schematically showing the configuration of the magnetic memory element in one embodiment of the present invention. Referring to FIG. 4, in the present embodiment, recording layer 3 is configured such that the area in plan view increases toward the fixed layer 1 side. That is, the cross-sectional shape of the recording layer 3 in the film thickness direction has such a shape that the area in the direction perpendicular to the film thickness direction of the recording layer 3 increases toward the fixed layer 1 side. For this reason, the position of the center of gravity Ga of the magnetization distribution in the film thickness direction of the recording layer 3 is closer to the fixed layer 1 in the film thickness direction of the recording layer 3, specifically, 1 of the film thickness of the recording layer 3. It exists on the fixed layer 1 side from the position of / 2 (position indicated by the alternate long and short dash line AA in the figure). The “centroid of magnetization in the film thickness direction” refers to a position that is perpendicular to the film thickness direction and included in a plane that bisects the magnetic moment of the recording layer 3 into equal values.

  The cross-sectional shape in the film thickness direction of the recording layer 3 in FIG. 4 can be approximated by a trapezoid, for example. The angle θ formed by the bottom surface (the surface on the tunnel insulating layer 2 side) and the side surface in the trapezoidal cross-sectional shape is preferably less than 90 degrees, and more preferably 80 degrees or less. Further, when the angle θ is reduced while maintaining the magnetic moment of the recording layer 3, the planar shape of the recording layer 3, that is, the planar shape of the bottom surface of the recording layer 3 is expanded. As a result, the area of the magnetic memory element MM portion in plan view increases, and consequently the chip size increases. For this reason, the angle θ is preferably 45 degrees or more.

  The recording layer 3 whose magnetization direction is changed by a magnetic field applied from the outside generally has a direction in which it is easily magnetized depending on the crystal structure or shape. This direction is a state in which energy is low, and the direction in which magnetization is easy is called an easy magnetization axis (Ea: Easy-axis). On the other hand, the direction hard to be magnetized is called a hard-axis (Ha).

  FIG. 5 is a schematic plan view for explaining the planar shape of the recording layer and the directions of the easy magnetization axis and the hard magnetization axis in one embodiment of the present invention. Referring to FIG. 5, in the present embodiment, the direction parallel to the direction indicated by arrow 91 is the direction of easy magnetization axis 63. The direction perpendicular to the easy magnetization axis 63 is the direction of the hard magnetization axis 64.

  The rectangle RC has a shape circumscribing the planar shape of the recording layer 3, and is a figure in which two sides are parallel to the easy magnetization axis 63. The shape of the recording layer 3 has a shape in which two of the four vertical corners of the rectangle RC are replaced with curves. Hereinafter, the shape of the recording layer 3 will be described in detail.

  The planar shape of the recording layer 3 includes linear portions 702 and 703 parallel to the easy magnetization axis 63 direction, and linear portions 704a and 704b parallel to the hard magnetization axis 64 direction (axial direction perpendicular to the easy magnetization axis 63). is doing. The straight portion 703 forms a vertical corner by being directly connected to each of the straight portions 704a and 704b. On the other hand, the straight portion 702 is connected to each of the straight portions 704a and 704b via each of the curved portions 701a and 701b. In the present embodiment, the curved portion 701a and the curved portion 701b are each formed to be an arc. Thereby, the planar shape of the recording layer 3 is formed so as to be asymmetric with respect to the easy magnetization axis 63 and axisymmetric with respect to the hard magnetization axis 64 (axis perpendicular to the easy magnetization axis 63).

  Since the planar shape of the recording layer 3 is asymmetric with respect to the easy magnetization axis 63 as described above, the center of gravity GP of the planar shape of the recording layer 3 is generally at a position different from the center of gravity DP of the rectangle RC. The center of gravity DP of the rectangle RC is an intersection of a pair of diagonal lines DG and DG of the rectangle RC.

  The planar shape of the recording layer 3 is formed so that the length in the direction of the easy magnetization axis 63 is longer than the length in the direction of the hard magnetization axis 64. That is, the rectangle RC has a long side along the direction of the easy magnetization axis 63. The ratio of the long side to the short side of the rectangle RC is, for example, 1.2.

  In the present embodiment, the pinned layer 1 and the tunnel insulating layer 2 also have substantially the same shape as the planar shape of the recording layer 3 shown in FIG. 5, but the present invention is not limited to this form. Only the recording layer 3 is formed to have a curved portion, and the fixed layer 1 and the tunnel insulating layer 2 are formed so that the planar shape is rectangular, and larger than the recording layer 3 when viewed in plan. It may be formed. That is, the tunnel insulating layer 2 and the fixed layer 1 may have the same planar shape as that of the recording layer 3, or an arbitrary planar shape including the planar shape of the recording layer 3 and having an area larger than that of the recording layer 3. It may be.

  FIG. 6 is an explanatory diagram showing the relative positional relationship between the recording layer, the write line, and the bit line in the magnetic storage device according to the embodiment of the present invention. Referring to FIGS. 5 and 6, the planar shape of each of write line WT and bit line BL (first and second wiring) is as follows: write line center axis CWT and bit line center axis CBL (first and second lines). Each axis is a central axis. The planar shapes of the write line WT and the bit line BL extend along the write line central axis CWT and the bit line central axis CBL, respectively. Each of the write line center axis CWT and the bit line center axis CBL has the same direction as each of the easy magnetization axis 63 and the hard magnetization axis 64. The write line center axis CWT and the bit line center axis CBL intersect each other perpendicularly to form an intersection point AP.

  In the present embodiment, the intersection point AP and the gravity center GP of the recording layer 3 coincide with each other. However, the present invention is not necessarily limited to this, and the distance between the gravity center GP and the intersection point AP is a rectangle RC. What is necessary is just to be smaller than the distance of the gravity center DP and the intersection AP. Preferably, the distance between the center of gravity GP and the intersection point AP is not more than half of the distance between the center of gravity GP and the center of gravity DP. More preferably, the center of gravity GP coincides with the intersection point AP as in the present embodiment.

(Memory cell operation)
Next, the operation of the memory cell will be described.

  Referring to FIG. 2, a read operation is performed by passing a predetermined current through magnetic storage element MM of a specific memory cell and detecting a difference in resistance value depending on the direction of magnetization. First, the selection transistor TR of a specific memory cell is turned on, and a predetermined sense signal passes through the specific magnetic memory element MM from the bit line BL via the connection members 18, 16, 14 and the selection transistor TR. To the source line SL.

  At this time, when the magnetization directions of the recording layer 3 and the pinned layer 1 in the magnetic memory element MM are the same direction (parallel), the resistance value is relatively low, and the magnetization directions of the recording layer 3 and the pinned layer 1 are opposite to each other. In the case of orientation (antiparallel), the resistance value is relatively high. The tunnel magnetoresistive element has a small resistance value when the magnetization directions of the recording layer 3 and the pinned layer 1 are parallel, and when the magnetization directions of the recording layer 3 and the pinned layer 1 are antiparallel. Has a characteristic that the resistance value increases.

  Thereby, when the magnetization direction of the magnetic memory element MM is parallel, the intensity of the sense signal flowing through the source line SL becomes larger than the signal intensity of a predetermined reference memory cell. On the other hand, when the magnetization direction of the magnetic memory element MM is antiparallel, the intensity of the sense signal is smaller than the signal intensity of a predetermined reference memory cell. Thus, whether the information written in the specific memory cell is “0” or “1” is determined depending on whether the intensity of the sense signal is larger or smaller than the signal intensity of the predetermined reference memory cell. become.

  The write (rewrite) operation is performed by flowing a predetermined current through the bit line BL and the write line WT to magnetize (magnetize inversion) the magnetic memory element MM. First, by applying a predetermined current to each of the selected bit line BL and write line WT, a magnetic field (indicated by arrows 53a and 53 in FIG. 6) is generated around the bit line BL and write line WT. 54a) occurs. The magnetic memory element MM located in the region where the selected bit line BL and the write line WT intersect each other has a combined magnetic field of a magnetic field generated by the current flowing through the bit line BL and a magnetic field generated by the current flowing through the write line WT. (Arrow 55a in FIG. 6) acts.

  At this time, the composite magnetic field causes the recording layer 3 of the magnetic memory element MM to be magnetized in the same direction as the magnetization direction of the pinned layer 1 and the direction in which the recording layer 3 is opposite to the magnetization direction of the pinned layer 1. There is a mode of being magnetized. In this way, a case where the magnetization directions of the recording layer 3 and the pinned layer 1 are the same (parallel) and opposite directions (anti-parallel) is realized, and the magnetization direction is set to “0” or “1”. It will be recorded as corresponding information.

(Method for manufacturing magnetic storage device)
Next, an example of a method for manufacturing the above-described magnetic memory element and magnetic memory device will be described.

  7 to 11 are schematic cross-sectional views showing the method of manufacturing the magnetic memory device according to the embodiment of the present invention in the order of steps. First, referring to FIG. 7, by forming element isolation insulating film 12 in a predetermined region on the main surface of semiconductor substrate 11, memory cell region MR and peripheral circuit region RR are formed. A gate electrode body G is formed on the surface of the semiconductor substrate 11 located in the memory cell region MR and the peripheral circuit region RR via a gate insulating film GI. By introducing an impurity of a predetermined conductivity type into the surface of the semiconductor substrate 11 using the gate electrode body G or the like as a mask, the drain region D and source region S made of impurity regions and a pair of source / drain regions S / D are formed. It is formed. Thus, the element selection transistor TR including the gate electrode G, the drain region D, and the source region S is formed in the memory cell region MR, and the transistor TRA constituting the logic circuit is formed in the peripheral circuit region RR.

  An interlayer insulating film 13 is formed by, for example, a CVD (Chemical Vapor Deposition) method so as to cover the element selection transistor TR and the transistor TRA. By performing predetermined photoengraving and etching on the interlayer insulating film 13, contact holes 13a and 13b exposing the surface of the semiconductor substrate 11 are formed. For example, a tungsten layer (not shown) is formed on interlayer insulating film 13 so as to fill contact holes 13a and 13b. By performing a CMP (Chemical Mechanical Polishing) process on the tungsten layer, a portion of the tungsten layer located on the upper surface of the interlayer insulating film 13 is removed.

  Referring to FIG. 8, by removing the tungsten layer, the tungsten layer remains in each of contact holes 13 a and 13 b to form connection member 14.

  Referring to FIG. 9, interlayer insulating film 15 is further formed on interlayer insulating film 13 by, eg, CVD. By performing predetermined photoengraving and etching on the interlayer insulating film 15, openings 15a and 15b for forming a write line and a predetermined wiring layer are formed in the memory cell region MR. Further, in the peripheral circuit region RR, an opening 15c for forming a predetermined wiring layer is formed in the interlayer insulating film 15. For example, a copper layer (not shown) is formed on interlayer insulating film 15 so as to fill the openings 15a, 15b, and 15c. By subjecting the copper layer to CMP treatment, the copper layer located on the upper surface of the interlayer insulating film 15 is removed, and the copper layer remains in the openings 15a, 15b, and 15c. As a result, in the memory cell region MR, the write line WT is formed in the opening 15a and the wiring layer 16 is formed in the opening 15b. In the peripheral circuit region RR, the wiring layer 16 is formed in the opening 15c.

  In the formation of the copper layer filling the openings 15a, 15b, and 15c, a reaction preventing layer for preventing the reaction between the copper layer and the interlayer insulating film may be laminated. Further, when the write line WT is formed, the copper layer may be laminated with a high permeability film in order to concentrate the wiring current magnetic field on a predetermined magnetic memory element.

  Referring to FIG. 10, an interlayer insulating film 17 is further formed on interlayer insulating film 15 by, for example, a CVD method. By performing predetermined photoengraving and etching on the interlayer insulating film 17, a contact hole 17a exposing the surface of the wiring layer 16 is formed. For example, a copper layer (not shown) is formed on interlayer insulating film 17 so as to fill the contact hole 17a. By subjecting the copper layer to, for example, CMP treatment or the like, the copper layer located on the upper surface of the interlayer insulating film 17 is removed, and the copper layer remains in the contact hole 17a to form the connection member 18.

  Next, the conductive layer 19 and the magnetic memory element MM are formed on the interlayer insulating film 17 in the memory cell region MR. The magnetic memory element MM is composed of a laminated film of a pinned layer 1, a tunnel insulating layer 2, and a recording layer 3. First, for example, a platinum manganese film (antiferromagnetic layer) having a film thickness of about 20 nm and a cobalt alloy film (ferromagnetic layer) having a film thickness of about 3 nm are sequentially formed as a film to become the pinned layer 1. Next, an aluminum oxide film having a film thickness of, for example, about 1 nm is formed as a film to be the tunnel insulating layer 2. Then, as the recording layer 3, for example, a nickel alloy film having a film thickness of about 3 nm is formed (both not shown). The platinum manganese film, cobalt alloy film, aluminum oxide film, and nickel alloy film are formed by, for example, sputtering.

  Thereafter, the nickel alloy film, the aluminum oxide film, the cobalt alloy film, and the platinum manganese film are subjected to predetermined photoengraving and etching to thereby form a magnetic memory having a predetermined shape including the fixed layer 1, the tunnel insulating layer 2, and the recording layer 3. An element MM is formed. Generally, when a dry process (ashing) is used for removing a resist pattern after etching, a gas containing oxygen as a main component is used. Preferably, a gas that is not oxidizing with respect to the constituent materials of the fixed layer 1 and the recording layer 3, such as hydrogen, nitrogen, ammonia, and a mixed gas thereof is used to suppress the oxidation of the fixed layer 1 and the recording layer 3.

  As a method for changing the cross-sectional shape of the recording layer 3 to a tapered shape such as a trapezoidal shape, the recording layer 3 may be patterned by dry etching, for example. More specifically, for example, there is a method using ion beam etching. In this method, an ion beam of an inert gas such as Ar (argon) is incident at an angle inclined with respect to the normal of the substrate surface of the semiconductor substrate 11. At this time, the semiconductor substrate 11 is rotated while maintaining the normal direction of the substrate surface. As another method, there is a method by RIE (Reactive Ion Etching) using a reactive gas containing Cl (chlorine) -based or CO (carbon monoxide) -based gas. In the case of this method, a mask for etching (for example, a resist mask or a hard mask made of metal / oxide) is tapered in advance or retracted during etching.

  The pinned layer 1 may have a laminated structure of antiferromagnetic layer / ferromagnetic layer / nonmagnetic layer / ferromagnetic layer. Further, the recording layer 3 has no problem with a laminated structure of ferromagnetic films having different magnetic characteristics or a laminated structure of ferromagnetic layer / nonmagnetic layer / ferromagnetic layer.

  Referring to FIG. 11, protective film 20 is formed to cover magnetic memory element MM so that magnetic memory element MM is not damaged by subsequent processes. An interlayer insulating film 21 is further formed on the interlayer insulating film 17 so as to cover the protective film 20 by, for example, a CVD method. In the memory cell region MR, a contact hole 21a exposing the surface of the recording layer 3 is formed by subjecting the interlayer insulating film 21 and the protective film 20 to predetermined photolithography and etching. In the peripheral circuit region RR, contact holes 21b reaching the surface of the wiring layer 16 are formed by subjecting the interlayer insulating film 21 and the interlayer insulating film 17 to predetermined photolithography and etching. For example, a copper layer (not shown) is formed on the interlayer insulating film 21 so as to fill the contact holes 21a and 21b. For example, by subjecting the copper layer to a CMP process or the like, the copper layer located on the upper surface of the interlayer insulating film 21 is removed, and the copper layer is left in each of the contact holes 21a and 21b to form the connection member 23. .

  An interlayer insulating film 24 is further formed on interlayer insulating film 21 by CVD, for example, so as to cover interlayer insulating film 21. By performing predetermined photoengraving and etching on the interlayer insulating film 24, an opening for forming a bit line is formed in the interlayer insulating film 24 in the memory cell region MR, and the interlayer insulating film 24 is formed in the peripheral circuit region RR. An opening 24a is formed. For example, a copper layer (not shown) is formed on interlayer insulating film 24 so as to fill the openings. By subjecting the copper layer to, for example, a CMP process or the like, the copper layer located on the upper surface of the interlayer insulating film 24 is removed, and the copper layer is left in the opening for the bit line to form the bit line BL. The wiring layer 25 is formed by leaving the copper layer in the 24a.

  Although the single damascene method has been described above, an interlayer insulating film 24 is further formed after the interlayer insulating film 21 is formed, and a predetermined connecting member is connected to the interlayer insulating films 21 and 24 by the dual damascene method. A wiring layer may be formed. In this case, first, predetermined photoengraving and etching are performed on the interlayer insulating film 24 to form an opening (not shown) for forming a bit line in the memory cell region MR. In the peripheral circuit region RR, an opening 24a for forming a wiring layer is formed. Next, by performing predetermined photoengraving and etching on the interlayer insulating film 21, a contact hole 21a reaching the surface of the recording layer 3 of the magnetic memory element MM is formed in the memory cell region MR. In the peripheral circuit region RR, a contact hole 21b reaching the surface of the wiring layer 16 is formed. Note that the opening 24 a and the like may be formed in the interlayer insulating film 24 after the contact holes are formed in the interlayer insulating films 21 and 24.

  Next, for example, a copper layer (not shown) is formed on interlayer insulating film 24 so as to fill the insides of contact holes 21a, 21b, opening 24a and the like. For example, a portion of the copper layer located on the upper surface of the interlayer insulating film 24 is removed by performing a CMP process or the like on the copper layer. As a result, in the memory cell region MR, a connection member 23 is formed that fills the contact hole 21a and is electrically connected to the recording layer 3, and is electrically connected to the connection member 23 in the opening. Bit line BL is formed. Even if the connecting member 23 is not used, there is no problem as long as the bit line BL and the recording layer 3 can be electrically connected. On the other hand, in the peripheral circuit region RR, a connection member 23 electrically connected to the wiring layer 16 is formed in the contact hole 21b, and a wiring layer electrically connected to the connection member 23 in the opening 24a. 25 is formed.

  Referring to FIG. 2, an interlayer insulating film 26 is further formed on interlayer insulating film 24 so as to cover bit line BL and wiring layer 25 formed as described above. In the peripheral circuit region RR, a hole is formed in the interlayer insulating film 26, and a connection member 27 is formed in the hole. An interlayer insulating film 28 is further formed on the interlayer insulating film 26. An opening is formed in the interlayer insulating film 28, and a wiring layer 29 is formed in the opening.

  Although the single damascene method has been described above, an interlayer insulating film 28 is further formed after the interlayer insulating film 26 is formed, and the interlayer insulating films 26 and 28 are connected to each other by the dual damascene method in the same manner as described above. The member 27 and the wiring layer 29 may be formed.

As described above, the magnetic storage device of the present embodiment is manufactured.
In the above-described method for manufacturing a magnetic memory device, a tungsten layer has been described as an example of the connection member 14 or the like. However, for example, silicon may be applied. Further, a metal such as copper, titanium or tantalum may be applied. Further, such metal alloys and nitrides of such metals can also be applied. Further, although the CMP method or the RIE method has been described as an example of the method for forming the connection member 14 or the like, for example, a plating method, a sputtering method, a CVD method, or the like may be applied. When copper is applied as the metal, a so-called damascene method can be applied, and a wiring layer can be formed in parallel with the connection member 14.

  Further, the single damascene method has been described as an example of the method for forming the write line WT. However, when the write line WT is formed at the same time as the connecting member 14, the dual damascene method can be applied. Furthermore, by using a metal such as silicon, tungsten, aluminum, or titanium, an alloy of such a metal, or a compound of such a metal as a wiring material, wiring can be formed by dry etching.

  The film thickness of the interlayer insulating film interposed between the wiring layers differs depending on the applied device. In this magnetic memory device, the film thickness is, for example, about 40 nm.

  The tunnel insulating layer 2 of the magnetic memory element MM has been described by taking aluminum oxide as an example, but the tunnel insulating layer 2 is preferably a nonmagnetic material. For example, an oxide of a metal such as aluminum, silicon, tantalum, or magnesium, a nitride of the metal, an alloy oxide of the metal typified by silicate, or a nitride of the alloy is preferable as the tunnel insulating layer 2. The tunnel insulating layer 2 is preferably formed as a relatively thin film having a thickness of about 0.3 to 5 nm. When a nonmagnetic metal material is used instead of the tunnel insulating layer 2, a so-called giant magnetoresistance effect perpendicular to the film surface can be used.

  Further, as the pinned layer 1 of the magnetic memory element MM, a laminated structure of a platinum manganese alloy film and a cobalt iron alloy film is taken as an example, and as the recording layer 3, a nickel iron alloy film is taken as an example. As for 3, a ferromagnetic material mainly composed of nickel, iron and / or cobalt is preferable. Furthermore, additives such as boron, nitrogen, silicon, and molybdenum may be introduced into the ferromagnetic materials in order to improve the magnetic properties and thermal stability of the ferromagnetic materials. In particular, for the recording layer 3, a crystalline material thin film having a body-centered cubic type, rutile type, sodium chloride type or zinc blende type crystal structure that improves the magnetic properties of the recording layer 3 is provided on the recording layer 3. It is possible to improve and stabilize the magnetic properties by stacking and / or stacking an anti-oxidation film such as tantalum or ruthenium. Further, NiMnSb, Co2Mn (Ge, Si), Co2Fe (Al, Si), (Zn, Mn) Fe2O4, or the like called half metal can be applied. In the half metal, since there is an energy gap in one spin band, a very large magnetic effect can be obtained, and as a result, a large signal output can be obtained.

  In the pinned layer 1, the magnetization direction can be further fixed by adopting a laminated structure of an antiferromagnetic layer and a ferromagnetic layer. That is, the antiferromagnetic layer fixes the spin direction of the ferromagnetic layer, so that the magnetization direction of the ferromagnetic layer is kept constant. The antiferromagnetic layer is preferably a compound of manganese and at least one of a ferromagnetic material such as iron or a noble metal.

  In the manufacturing method described above, the case where the pinned layer 1, the tunnel insulating layer 2, and the recording layer 3 constituting the magnetic memory element are formed by sputtering is taken as an example. However, each of the fixed layer 1, the tunnel insulating layer 2 and the recording layer 3 can be formed by, for example, MBE (Molecular Beam Epitaxy) method, chemical vapor deposition method or vapor deposition method in addition to the sputtering method. is there.

  In the above-described method for manufacturing the magnetic memory device, the case where the conductive layer 19 is provided between the pinned layer 1 of the magnetic memory element MM and the connecting member 18 has been described. However, the pinned layer 1 and the connecting member 18 are directly connected. May be. Further, a structure in which the wiring layer 16 and the conductive layer 19 are directly connected without using the connection member 18 may be employed. In this case, the conductive layer 19 may be formed in the same shape as the planar shape of the fixed layer 1 so as to overlap the fixed layer 1 in plan view. As the material of the conductive layer 19, it is preferable to apply a low resistance metal such as platinum, ruthenium, copper, aluminum, tantalum or the like. The film thickness of the conductive layer 19 is preferably set to 300 nm or less, for example, so that the flatness of the fixed layer 1, the tunnel insulating layer 2 and the recording layer 3 formed on the conductive layer is not impaired. .

  When the fixing layer 1 is formed in the same size as the recording layer 3 in plan view, the conductive layer 19 is formed larger than the fixing layer 1 in plan view so that the conductive layer 19 is connected to the connection member 14. There is a need to. Thus, even if the conductive layer 19 is formed to be larger than the fixed layer 1 in a plan view, there is no problem as a magnetic memory element.

  In this manner, when the connecting member 18 is formed of, for example, copper by interposing the predetermined conductive layer 19 between the interlayer insulating film 15 and the magnetic memory element MM, when the magnetic memory element MM is patterned by etching. In addition, the copper connecting member 18 can be prevented from corroding. In addition, by applying a material having a resistance lower than the resistance of the pinned layer 1 of the magnetic memory element MM to the conductive layer 19, the resistance of the current path at the time of reading can be reduced, and the reading speed can be improved. You can also plan.

  Further, in the magnetic memory device of the present embodiment described above, the magnetic memory element MM is covered so as to prevent the magnetic memory element MM from being damaged in the process after the magnetic memory element MM is formed. The case where the protective film 20 is formed is described as an example. Damage that the magnetic memory element MM may suffer in the manufacturing process includes, for example, heat treatment when forming an interlayer insulating film. When a silicon oxide film is formed as an interlayer insulating film, the silicon oxide film is formed under an oxidizing atmosphere of about 400 ° C.

  At this time, the magnetic film may be oxidized under an oxidizing atmosphere, which may degrade the magnetic characteristics of the magnetic memory element MM. By covering the magnetic memory element MM with a protective film 20 such as a silicon nitride film or an aluminum oxide film, the protective film 20 can function as a barrier for this oxidation to protect the magnetic memory element MM.

  In order to prevent such oxidation, the interlayer insulating film may have a two-layer structure of a thin film that can be formed under a non-oxidizing atmosphere such as a silicon nitride film and an oxidizing insulating film. In this case, of the two-layered interlayer insulating film, the silicon nitride film serves as a protective film for the magnetic memory element MM.

  Furthermore, the protective film 20 is preferably a film containing at least one material of an insulating metal nitride, an insulating metal carbide, and a metal oxide formed by oxidation of a metal having a lower free energy of oxide generation than Fe. . By using such a material, at least the oxidation of the magnetic memory element MM during the oxidation process in the manufacturing process of the magnetic memory device using the magnetic material thin film containing Fe can be suppressed. As a result, a magnetic memory device that is easy to manufacture and has stable operating characteristics can be obtained.

(Function and effect)
The main operational effects of the magnetic storage device according to the present embodiment will be described below.

  FIG. 12 is a graph for explaining the correlation between the position of the center of gravity of the recording layer and the asteroid curve in one embodiment of the present invention. 6 and 12, when the intersection point AP and the center of gravity GP of the recording layer 3 coincide with each other as shown in FIG. 6, an asteroid curve 35 including the points shown in FIG. It was. Each of the asteroid curves 36 and 37 shows a calculated asteroid curve when the intersection AP and the gravity center GP of the recording layer 3 are shifted by a distance X> 0 and by a distance 2X. In this calculation, the ferromagnetic material of the recording layer 3 and the thickness of the portion made of this ferromagnetic material were made the same. The horizontal axis of the graph of FIG. 12 shows the current IWT that flows through the write line WT to generate the magnetic field Hx in the hard axis direction, and the vertical axis flows through the bit line BL to generate the magnetic field Hy in the easy axis direction. Current IBL is shown. In the figure, the bit line current IBL necessary for reversing the magnetization direction when a constant write line current IWT is applied in a state where the magnetization direction of the recording layer 3 is in the negative direction of the magnetic field Hy. The measured result is shown.

  When the recording layer 3 having the shape shown in FIG. 5 is employed, as will be described later with reference to FIG. 17, the write line current IWT has a constant value in the asteroid curve 35 (hereinafter referred to as “threshold in the hard axis direction”). The bit line current IBL required for reversal in the easy axis direction suddenly increases. That is, a large bit line current IBL is required for magnetization reversal only in a region where the write line current IWT is smaller than the hard axis threshold.

  When the position of the intersection point AP and the center of gravity AP of the recording layer 3 shifts, the current value necessary for magnetization reversal changes, and the asteroid curve changes from the asteroid curve 35 to the asteroid curves 36 and 37. As a result, the area (hatching area in the figure) 46 in which the magnetization reversal of the recording layer can be narrowed or information cannot be written.

  In the conventional example, the vicinity of the intersection AP and the center of gravity DP of the rectangle RC are arranged so as to substantially coincide with each other. If the planar shape of the recording layer 3 is asymmetric with respect to the easy magnetization axis direction, the intersection point AP and the center of gravity GP do not coincide with each other and are separated by, for example, a distance X in plan view. In this case, the asteroid curve of the recording layer is equivalent to the asteroid curve 36.

  In a highly integrated device such as an MRAM, it is difficult to uniformly form the relative arrangement of the write line WT, the bit line BL, and the recording layer 3 in all the multiple magnetic storage elements MM. Therefore, in the conventional example, when the relative positions of the write line WT, the bit line BL, and the recording layer 3 are further shifted by the distance X, the center of gravity GP is shifted from the intersection AP by X + X = 2X. As a result, the asteroid curve of the recording layer is represented by an asteroid curve 37, and the region 46 in which the magnetization reversal of the recording layer can be performed is significantly narrowed or information cannot be written.

  According to the present embodiment, as shown in FIG. 6, the variation in the wiring current necessary for the magnetization reversal is achieved by making the center of gravity GP of the recording layers 3 of the magnetic memory elements MM arranged in a matrix substantially coincide with the intersection AP. Can be suppressed. Therefore, it is preferable that the amount of deviation (distance) between the center of gravity GP and the intersection point AP is made smaller. In particular, when the distance between the center of gravity GP and the center of gravity DP is less than half of the distance, the above-described variation suppressing effect can be greatly obtained. It is done.

Next, other functions and effects of the present embodiment will be described below.
When the leakage magnetic field from the ferromagnetic layer constituting the pinned layer 1 is superimposed on the external magnetic field, the magnetization switching magnetic field changes by the leakage magnetic field component. In the present embodiment, the leakage magnetic field from the ferromagnetic layer constituting the pinned layer 1 shifts the hard axis direction threshold value. Therefore, when the hard axis direction threshold value is shifted to the high magnetic field side, When the threshold value in the hard axis direction is shifted to the low magnetic field side, it is considered that it becomes impossible to write information, and it is not selected by the magnetic field formed by passing current through the bit line BL and / or the write line WT It is conceivable that the magnetic storage element of the magnetic field inverts magnetization by mistake. In other words, if the hard axis threshold value varies from element to element, a write error may occur.

  In order to reduce the variation in the threshold value in the hard axis direction, the leakage magnetic field component is set to zero in all the magnetic memory elements MM, or all the leakage magnetic fields from the pinned layer 1 when no external magnetic field is applied. The magnetic storage elements MM may be the same, and the magnetization gradient of the pinned layer 1 may be the same for all the magnetic storage elements MM when an external magnetic field is applied. However, in a highly integrated device such as MRAM, it is practically difficult to set the same leakage magnetic field from the pinned layer 1 for all the magnetic memory elements MM.

  In the present embodiment, a configuration is adopted in which the magnetization of the portion of the recording layer 3 that is close to the fixed layer 1 and is easily affected by the leakage magnetic field from the fixed layer 1 is increased.

  Referring to FIG. 4, in the present embodiment, recording layer 3 is configured such that the area in plan view increases toward the fixed layer 1 side. Therefore, the position of the center of gravity Ga of the magnetization distribution in the film thickness direction of the recording layer 3 is closer to the fixed layer 1 in the film thickness direction of the recording layer 3 (vertical direction in the figure), specifically, the recording layer 3. It exists in the position of the fixed layer 1 side rather than the position of 1/2 of the film thickness (dashed line AA). For this reason, since the magnetization of the recording layer 3 becomes large at a portion where the distance from the fixed layer 1 is short and the influence of the leakage magnetic field is large, the shift of the magnetization switching magnetic field of the recording layer 3 due to the leakage magnetic field component is suppressed. As a result, the hard axis threshold is stable against the leakage magnetic field. In other words, it is possible to reduce variations in the hard axis direction threshold value due to the leakage magnetic field from the pinned layer 1.

  In general, it is known that the magnetization reversal field increases as the total magnetization of the recording layer 3 increases. In the present embodiment, the total magnetization of the recording layer 3 as a whole is reduced by the amount that the area of the recording layer 3 in plan view decreases toward the upper surface of the recording layer 3 (the surface opposite to the fixed layer 1). It is suppressed. For this reason, since an increase in the magnetization reversal magnetic field is suppressed, the magnetization reversal can be performed efficiently by the external magnetic field.

  With respect to the above effect, it is only necessary that the position of the center of gravity Ga of the magnetization in the film thickness direction of the magnetization distribution of the recording layer 3 exists on the fixed layer 1 side than 1/2 of the film thickness of the recording layer 3. For this reason, when the cross-sectional shape of the recording layer 3 is approximated by a trapezoid, for example, the angle θ formed by the bottom surface portion and the side surface portion only needs to be smaller than 90 degrees, and more preferably 80 degrees or less. In addition, when the angle θ formed between the bottom surface portion and the side surface portion is small, this leads to an increase in the area of the magnetic memory element MM portion in plan view, and thus an increase in chip size. More preferably, it is not less than 80 degrees and not more than 80 degrees.

  Further, even when the angle θ formed by the bottom surface portion and the side surface portion is larger than 80 degrees, the same effects as described above can be obtained with the configurations shown in FIGS. 13 and 14. FIG. 13 is a cross-sectional view schematically showing the configuration of the magnetic memory element according to one embodiment of the present invention, and FIG. 14 shows changes in the phase content along the XIV-XIV line in the recording layer of FIG. FIG. Referring to FIG. 13, the recording layer 3 includes a first phase of a ferromagnetic material that is a main component of the recording layer 3 and a second phase of a ferromagnetic material having a saturation magnetization smaller than the saturation magnetization of the first phase. Or it has the 2nd phase which shows paramagnetism. Referring to FIG. 14, the content ratio of the second phase continuously increases from the fixed layer 1 side toward the recording layer 3 surface. Even when the recording layer 3 has this structure, the position of the center of gravity Ga of the magnetization in the thickness direction of the magnetization distribution of the recording layer 3 exists on the fixed layer 1 side with respect to 1/2 of the thickness of the recording layer 3. Therefore, the same effect as described above can be obtained.

  In order to increase the magnetization of a part of the recording layer 3 that is close to the fixed layer 1 and easily affected by the leakage magnetic field from the fixed layer 1, it is also effective to make the recording layer 3 have a laminated film structure. . FIG. 15 and FIG. 16 are schematic cross-sectional views showing configurations when the recording layer of the magnetic memory element in each of the second and third modifications of the embodiment of the present invention has a laminated film structure. . Referring to FIG. 15, the recording layer 3 has at least two layers, for example, a first ferromagnetic layer 3a having a relatively large saturation magnetization and a second ferromagnetic layer 3b having a relatively small saturation magnetization. It has a laminated film structure. Referring to FIG. 16, the recording layer 3 includes a first ferromagnetic layer 3a having a relatively large saturation magnetization, a second ferromagnetic layer 3b having a relatively small saturation magnetization, and the first and first ferromagnetic layers 3b. A laminated structure having at least three layers with a nonmagnetic layer 3c sandwiched between two ferromagnetic layers 3a and 3b may be used. As shown in FIGS. 15 and 16, the first ferromagnetic layer 3a having a relatively large saturation magnetization is positioned on the fixed layer 1 side in the recording layer 3, and the second ferromagnetic layer having a relatively small saturation magnetization. Since the layer 3b is located on the surface side of the recording layer 3, the position of the center of gravity Ga of the magnetization distribution in the film thickness direction of the recording layer 3 exists on the fixed layer 1 side with respect to 1/2 of the film thickness of the recording layer 3 Will do.

  In the three-layer structure of ferromagnetic layer 3a / nonmagnetic layer 3c / ferromagnetic layer 3b shown in FIG. 16, the case where two ferromagnetic layers 3a and 3b are ferromagnetically coupled, and the case of spin exchange interaction or magnetostatic coupling In some cases, the action causes antiferromagnetic coupling. In any case, if the structure is such that the first ferromagnetic layer 3a having a large saturation magnetization is disposed on the fixed layer 1 side, the hard axis threshold value due to the leakage magnetic field from the fixed layer 1 is set. Variations can be reduced.

  Further, in the three-layer structure of the ferromagnetic layer 3a / nonmagnetic layer 3c / ferromagnetic layer 3b, the two ferromagnetic layers 3a and 3b are composed of, for example, the same ferromagnetic material. Even when the saturation magnetizations of the two layers are the same, an effective difference in film thickness is given to the ferromagnetic layers 3a and 3b, thereby giving a difference in the magnetization amount of the two layers. This provides a structure in which the first ferromagnetic layer 3a having a large amount of magnetization is disposed on the pinned layer 1 side, so that the threshold in the hard axis direction caused by the leakage magnetic field from the pinned layer 1 is the same as described above. The value variation can be reduced.

Next, the function and effect of setting the planar shape of the recording layer to the shape shown in FIG. 5 will be described.
In describing the above-described effects, first, the rewriting operation will be described in more detail.

  FIG. 17 is a graph for explaining a difference between an asteroid curve in one embodiment of the present invention and an asteroid curve in a comparative example having a rectangular recording layer. Referring to FIG. 17, the difference between the asteroid curve 35 of the present embodiment and the asteroid curve 31 in the comparative example having the rectangular recording layer is that the ferromagnetic material of the recording layer 3 and the ferromagnetic material thereof are different. Comparison is made under the condition that the thickness of the portion is constant. The horizontal axis of the graph represents the current IWT that flows through the write line WT to generate the magnetic field Hx in the hard axis direction, and the vertical axis represents the current that flows through the bit line BL to generate the magnetic field Hy in the easy axis direction. IBL is shown. The point plotted on the asteroid curve 35 is that the magnetization direction is reversed when a constant write line current IWT is applied in a state where the magnetization direction of the recording layer 3 is negative in the magnetic field Hy. The result of measuring the bit line current IBL necessary for the measurement is shown.

  When the recording layer 3 having the shape shown in FIG. 5 is employed, as shown in the asteroid curve 35, if the write line current IWT is smaller than the hard axis threshold value, magnetization reversal in the easy axis direction is achieved. The necessary bit line current IBL increases rapidly. That is, a large magnetization reversal current with respect to the easy axis direction is required only in a region where the write line current IWT is smaller than the hard axis threshold. On the other hand, if the write line current IWT is larger than the hard axis threshold, the bit line current IBL necessary for inversion becomes smaller.

  As for the region 45 in which the magnetization reversal of the recording layer 3 (lower right hatching region in the figure) 45 can be performed, the region in which the magnetization reversal can be performed when the planar shape of the recording layer 3 is a rectangular shape (lower left in the drawing). Hatching region) 41 is larger, and in particular, the region is larger in the easy axis direction indicated by the magnetic field Hy. Therefore, it is possible to suppress the occurrence of magnetization reversal when a magnetic field is applied only in the easy axis direction. That is, the magnetization reversal of the recording layer 3 that is not intended to be reversed among the recording layers 3 of the plurality of magnetic memory elements MM arranged along the write bit line BL can be suppressed. . Thus, write errors can be reduced.

  Thus, in the magnetic memory element MM including the recording layer 3 having the planar shape shown in FIG. 5, the current required for magnetization reversal in the non-selected magnetic memory element MM is made larger than that in the conventional recording layer, In the selected magnetic memory element MM, the current required for magnetization reversal can be made smaller than before. Therefore, the reliability of selection of the magnetic memory element MM is improved.

  As shown in FIG. 17, the phenomenon in which the magnitude of the bit line current IBL necessary for the magnetization reversal is significantly different depending on the magnitude of the write line current IWT is due to the difference in the magnetization state. FIG. 18 and FIG. 19 are diagrams showing magnetization distributions when the combined magnetic field of the magnetic field in the easy magnetization direction and the magnetic field in the hard magnetization direction is smaller and larger than the reversal magnetic field. It is a top view of the recording layer of the magnetic memory element in the form. Each arrow in FIGS. 18 and 19 indicates the direction of magnetization at each position. In FIG. 18 and FIG. 19, the magnetic field is applied so that each magnetic field Hy has the same magnitude and the magnitude of the magnetic field Hx is different. The magnetic field Hx applied in FIG. 18 is smaller than the hard axis threshold value, and the magnetic field Hx applied in FIG. 19 is larger than the hard axis threshold value.

  The form of the magnetization distribution as shown in FIG. 18 is called C-type (first magnetization distribution), and since it is a stable magnetization state, the magnetization reversal magnetic field in the easy axis direction becomes large. On the other hand, the form of the magnetization distribution as shown in FIG. 19 is called S-type (second magnetization distribution), and the magnetization reversal magnetic field is abruptly reduced because it is easily subjected to torque by an external magnetic field. 20A and 20B are conceptual diagrams of the magnetization distribution states of the S type and the C type. The recording layer 3 of the present embodiment has a planar shape that can control the S-type and C-type magnetization distribution states with an external magnetic field.

  Thus, by making the planar shape of the recording layer 3 asymmetric with respect to the easy magnetization axis and symmetrical with respect to the axis perpendicular to the easy magnetization axis, the S-type and C-type as described above are used. A magnetization distribution state can be obtained. By obtaining S-type and C-type magnetization distribution states, as shown in FIG. 17, a region 45 in which the magnetization reversal of the recording layer 3 can be performed is enlarged, and magnetization generated by applying a magnetic field only in the easy axis direction. Inversion can be suppressed.

(Modification)
In the above description, the shape shown in FIG. 5 has been described as the planar shape of the recording layer 3 capable of obtaining S-type and C-type magnetization distribution states. However, the planar shape of the recording layer 3 may be other shapes. . For example, the planar shape of the recording layer 3 may be asymmetric with respect to the easy magnetization axis 63 and symmetric with respect to the hard magnetization axis 64 as shown in FIGS. FIG. 21 shows an example of a shape formed by connecting curves having different curvatures, and FIG. 22 shows an example of a shape formed by connecting a plurality of straight lines.

  Further, the shape is asymmetric with respect to the easy magnetization axis 63 and symmetric with respect to the hard magnetization axis 64, and a part of the shape has a convex portion as shown in FIG. 23 and a concave portion as shown in FIG. Even if it exists, there is no problem if the magnetization distribution of the recording layer 3 can be changed between the C type and the S type by the magnetic field generated by the bit line current IBL and the write line current IWT.

  As shown in FIGS. 25 and 26, even if the easy axis direction of magnetization of the recording layer 3 and the magnetization direction of the pinned layer 1 are in the short-side direction of the rectangular shape in contact with the planar shape of the recording layer 3, the bit line current It is only necessary that the magnetization distribution of the recording layer 3 can be changed between the C type and the S type by the magnetic field generated by the IBL and the write line current IWT.

  Further, as shown in FIG. 27, the planar shape of the recording layer 3 may be asymmetric with respect to the easy magnetization axis 63 and the hard magnetization axis 64. As shown in FIG. 28, the easy magnetization axis 63 of the recording layer 3 is inclined with respect to the wiring direction (extending direction of the write line WT) 63a that applies a magnetic field in the same direction as the easy magnetization axis 63. There may be. In the case of the shape shown in FIG. 27, the S type shown in FIG. 29 and the C type shown in FIG. 30, and in the case shown in FIG. 28, the S type shown in FIG. 31 and the C type shown in FIG. The magnetization distribution changes.

  The center of gravity GP in the in-plane direction of the recording layer 3 is not limited to the planar shape of the recording layer 3 described above, and when the recording layer 3 is given a leakage magnetic field due to the ferromagnetic layer of the pinned layer 1. The same effect can be obtained even when the position is moved in the hard axis direction from the shape center of FIG.

  In any of the shapes shown in FIGS. 21 to 26, the center of gravity GP regarding the shape in the film surface direction of the recording layer 3 of the magnetic memory element MM substantially coincides with the vicinity of the center of the intersection of the write line WT and the bit line BL in plan view. By doing so, it is possible to suppress variations in the wiring current at the time of magnetization reversal caused by the relative positional relationship shift between the write line WT, the bit line BL, and the recording layer 3.

  Further, when the recording layer 3 is given a leakage magnetic field due to the ferromagnetic layer of the pinned layer 1, the position of the center of gravity Ga of the magnetization distribution in the film thickness direction of the magnetization distribution of the recording layer 3 is 1 of the film thickness of the recording layer 3. By making it be on the side of the pinned layer 1 with respect to / 2, it is possible to reduce variations in the hard axis threshold value due to the leakage magnetic field from the pinned layer 1.

  When a large number of magnetic memory elements MM having the shape of the recording layer 3 asymmetric with respect to the easy magnetization axis 63 and symmetric with respect to the hard magnetization axis 64 are arranged in a matrix as shown in the present embodiment, the connection As an arrangement of the member 18 and the magnetic memory element MM, for example, there is an arrangement shown in FIG. 33 or FIG. In any arrangement, the magnetization distribution of the recording layer 3 can be changed between the C type and the S type by a magnetic field generated by the bit line current IBL and the write line current IWT regardless of the arrangement of the connecting member 18. In addition, when the arrangement of the magnetic memory element MM is different for each write line WT, the direction of the write line current IWT can be controlled so that the fluctuation of the magnetization reversal behavior due to the shape variation of the recording layer 3 can be suppressed. preferable. For example, in the arrangement of FIG. 35 or FIG. 36, it is preferable to use the write line current IWT in the reverse direction for adjacent write lines WT.

  Furthermore, the present embodiment is applied to a cell architecture that always reduces the difference between the read path of the selected cell and the read path of the reference cell during information read operation, and reduces the read current variation due to parasitic resistance and capacitance. When used, for example, if it is associated with the arrangement of FIG. 35, a cell arrangement as shown in FIG. 37 is also conceivable. In the arrangement according to FIG. 37, cells having the same symmetry are arranged every other bit line BL direction, and therefore, for example, a cell arrangement as shown in FIG. 38 or 39 is possible. In this example, the width of the bit line BL is substantially the same as the size of the magnetic memory element MM, but even if the bit line BL width is larger or smaller than the size of the magnetic memory element MM, There is no problem if the magnetization of the recording layer 3 can be reversed by the magnetic field generated by the line current IBL and the write line current IWT.

  When a material with a relatively high dielectric constant, such as a silicon nitride film, is used as an oxidation barrier for a mixed device that includes memory cells including a magnetic memory element and a logic circuit, the following is required. You must keep in mind. That is, for example, in a device composed of a logic circuit, the capacitance and wiring resistance between metal wiring layers are set in consideration of the operation speed and access timing of the device. Therefore, if a material with a high dielectric constant is placed in the logic circuit section, the capacitance between the metal wiring layers in the logic circuit section may fall outside the predetermined design parameter range, and the device may not perform a desired operation. . In order to avoid this, the protective film may be formed so as to cover only the magnetic memory element MM, and the protective film may not be formed in the peripheral circuit region RR where the logic circuit is formed.

  In the magnetic storage device using the above-described magnetic storage element, it is possible to read out stored information without destroying the storage state. This eliminates the need for rewriting and increases the reading speed. In addition, since the magnetization reversal speed is 1 nanosecond or less, information can be written at a very high speed. Furthermore, with respect to the magnetization reversal operation, it is generally said that a fatigue phenomenon in which the characteristics deteriorate due to repeated reversal does not occur. That is, the magnetic storage device called MRAM can provide a non-volatile memory device with virtually no limit on the number of operations.

  The above-described feature is useful as a single memory device, but it works even more effectively in the case of a mixed device in which the memory cell is mixed with a logic circuit. That is, in the case of an embedded device, the interactive environment for handling information in a network environment or mobile communication is improved based on high-speed operation. Furthermore, by applying the magnetic storage device to a computer, a portable terminal or the like, it is possible to greatly reduce power consumption and improve the operating environment.

  In the magnetic memory element and the magnetic memory device described above, the magnetic memory device using the semiconductor substrate has been described. However, the relationship between the magnetoresistive effect element and the wiring layer related to the write line and the bit line is limited to information storage. For example, the present invention can be widely applied to patterned magnetic elements such as a magnetic sensor, a magnetic recording head, and a magnetic recording medium.

  Further, in the above-described magnetic memory element and magnetic memory device, a memory cell in which one memory cell is provided with one magnetic memory element has been described as an example. However, two or more magnetic memories are stored in one memory cell. Elements may be provided, and those memory cells may be stacked on each other.

  The embodiments disclosed herein are merely examples in all respects, and the present invention is not limited thereto. The scope of the present invention is defined by the terms of the claims, rather than the scope described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be particularly advantageously applied to a magnetic memory device using a magnetoresistive effect element.

1 is a circuit diagram of a memory cell of a magnetic memory device according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a configuration of a magnetic memory device according to an embodiment of the present invention. 3 is a perspective view schematically showing a configuration in the vicinity of a magnetic memory element MM. FIG. 1 is a cross-sectional view schematically showing a configuration of a magnetic memory element of a magnetic memory device according to an embodiment of the present invention. 1 is a schematic plan view for explaining a planar shape of a recording layer and directions of an easy magnetization axis and a hard magnetization axis in an embodiment of the present invention. FIG. 4 is an explanatory diagram showing a relative positional relationship among a recording layer, a write line, and a bit line in the magnetic storage device according to the embodiment of the present invention. It is a schematic sectional drawing which shows the 1st process of the manufacturing method of the magnetic memory device in one embodiment of this invention. It is a schematic sectional drawing which shows the 2nd process of the manufacturing method of the magnetic memory device in one embodiment of this invention. It is a schematic sectional drawing which shows the 3rd process of the manufacturing method of the magnetic memory device in one embodiment of this invention. It is a schematic sectional drawing which shows the 4th process of the manufacturing method of the magnetic memory device in one embodiment of this invention. It is a schematic sectional drawing which shows the 5th process of the manufacturing method of the magnetic memory device in one embodiment of this invention. It is a graph for demonstrating the correlation with the position of the gravity center of the recording layer in one embodiment of this invention, and an asteroid curve. It is sectional drawing which shows roughly the structure of the magnetic memory element in the 1st modification of one embodiment of this invention. It is a figure which shows the change of the content rate of the phase in alignment with the XIV-XIV line | wire in the recording layer of FIG. It is a schematic sectional drawing which shows a structure when the recording layer of the magnetic memory element in the 2nd modification of one embodiment of this invention is made into the laminated film structure of two layers. It is a schematic sectional drawing which shows the structure at the time of making the recording layer of the magnetic memory element in the 3rd modification of one embodiment of this invention into the laminated film structure of 3 layers. It is a graph for demonstrating the difference between the asteroid curve in one embodiment of this invention, and the asteroid curve in the comparative example which has a rectangular-shaped recording layer. It is a figure which shows magnetization distribution when the synthetic magnetic field of the magnetic field of a magnetization easy axis direction and the magnetic field of a magnetization difficult axis direction is smaller than a reversal magnetic field, The plane of the recording layer of the magnetic memory element in one embodiment of this invention FIG. It is a figure which shows magnetization distribution in case the synthetic magnetic field of the magnetic field of a magnetization easy axis direction and the magnetic field of a magnetization difficult axis direction is larger than a reversal magnetic field, The plane of the recording layer of the magnetic memory element in one embodiment of this invention FIG. FIG. 4 is a conceptual diagram (a) of an S-type magnetization distribution state and a conceptual diagram (b) of a C-type magnetization distribution state. It is a figure which shows one example of the planar shape of a recording layer. It is a figure which shows the other example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows the further another example of the planar shape of a recording layer. It is a figure which shows S type magnetization distribution in the plane shape of the recording layer shown in FIG. It is a figure which shows C type magnetization distribution in the plane shape of the recording layer shown in FIG. It is a figure which shows S type magnetization distribution in the planar shape of the recording layer shown in FIG. FIG. 29 is a diagram showing a C-type magnetization distribution in the planar shape of the recording layer shown in FIG. 28. It is a figure which shows one example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the other example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the further another example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the further another example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the further another example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the further another example of arrangement | positioning of the matrix form of a memory cell. It is a figure which shows the further another example of arrangement | positioning of the matrix form of a memory cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fixed layer, 2 Tunnel insulating layer, 3 Recording layer, 3a, 3b Ferromagnetic layer, 3c Nonmagnetic layer, 11 Semiconductor substrate, 12 Element isolation insulating film, 13, 15, 17, 21, 24, 26, 28 Interlayer insulation Film, 13a, 17a, 21a, 21b contact hole, 14, 16, 18, 23, 27 connecting member, 15a, 15b, 15c, 24a opening, 16, 25, 29 wiring layer, 19 conductive layer, 20 protective film, 28 Insulating layer, AP intersection, BL bit line, D drain region, DP rectangular center of gravity, G gate electrode, GI gate insulating film, MC memory cell, MM magnetic memory element, MR memory cell region, RR peripheral circuit region, S source Region, S / D source / drain region, SL source line, TR element selection transistor, TRA transistor, WD word line, W Write line, the center of gravity of the plane shape of the GP recording layer.

Claims (13)

A substrate,
A first wiring having a portion provided on the substrate and having a planar shape extending along the first axis with the first axis as a central axis;
A planar portion having a portion extending along the second axis with a second axis intersecting the first axis as a central axis, and spaced in the thickness direction of the substrate; A second wiring crossing the first wiring;
A recording layer having an easy magnetization axis and a planar shape asymmetric with respect to the easy magnetization axis; and a fixed layer having a fixed magnetization direction, wherein the first and second wirings are spaced apart from each other. A magnetic memory element at least partially sandwiched between the first and second wirings in a region intersecting each other,
A magnetic memory in which the distance between the center of gravity of the planar shape of the recording layer and the intersection is smaller than the distance between the center of gravity of the rectangle circumscribing the planar shape of the recording layer and the intersection of the first and second axes apparatus.   2. The magnetic storage device according to claim 1, wherein the distance between the center of gravity of the planar shape of the recording layer and the intersection is not more than half of the distance between the center of gravity of the planar shape of the recording layer and the center of gravity of the rectangle.   The magnetic storage device according to claim 1, wherein the center of gravity of the planar shape of the recording layer and the intersection point coincide with each other.   The magnetic storage device according to claim 1, wherein a planar shape of the recording layer is symmetric with respect to an axis perpendicular to the easy axis of magnetization.   The magnetic storage device according to claim 1, wherein a planar shape of the recording layer is asymmetric with respect to an axis perpendicular to the easy magnetization axis.   The magnetic storage device according to claim 1, wherein the planar shape of the recording layer has a linear outer shape portion at least in an axial direction perpendicular to the easy magnetization axis.   The magnetic storage device according to claim 1, wherein each of a magnetization direction of the fixed layer and a direction of the easy axis is a short side direction in a rectangular shape circumscribing a planar shape of the recording layer.   The magnetic storage device according to claim 1, wherein at least one of the first and second axes is inclined with respect to the easy magnetization axis.   The cross-sectional shape in the film thickness direction of the recording layer has such a shape that an area in a direction perpendicular to the film thickness direction of the recording layer increases toward the fixed layer side. A magnetic storage device according to any one of the above.   10. The magnetic storage device according to claim 9, wherein a cross-sectional shape of the recording layer in a film thickness direction is a trapezoid, and an angle formed between a bottom surface and a side surface in the trapezoidal cross-sectional shape is 45 degrees or more and 80 degrees or less.   The recording layer has a first phase of a ferromagnetic material that is a main component of the recording layer, and a second phase that exhibits ferromagnetism or paramagnetism with a small saturation magnetization with respect to the first phase. The magnetic storage device according to claim 1, wherein the two phases have a structure in which a content ratio is continuously increased from the fixed layer side toward the recording layer surface.   The recording layer has a laminated film structure having at least two layers of a first ferromagnetic layer having a large saturation magnetization and a second ferromagnetic layer having a small saturation magnetization, and the first ferromagnetic layer is the first ferromagnetic layer. The magnetic storage device according to claim 1, wherein the magnetic storage device is disposed closer to the pinned layer than the two ferromagnetic layers.   The recording layer includes at least three layers of a first ferromagnetic layer having a large effective magnetization, a second ferromagnetic layer having a small effective magnetization, and a nonmagnetic layer sandwiched between the first and second ferromagnetic layers. The magnetic storage device according to claim 1, wherein the first ferromagnetic layer is arranged closer to the pinned layer than the second ferromagnetic layer.

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