TWI768001B - Charged particle beam apparatus and sample processing method - Google Patents

Abstract

The present invention provides a charged particle beam apparatus and a sample processing method which can uniformly irradiate a charged particle beam to the entire small sample piece having a reduced thickness of the sample and can clearly grasp the processing end point during processing. The charged particle beam device irradiates the charged particle beam toward the sample to make a tiny sample piece, and is characterized in that the charged particle beam device has: a charged particle beam lens barrel, which can irradiate the charged particle beam toward the sample; A sample chamber that accommodates the charged particle beam column; and a sample piece holder capable of holding the sample while forming a minute sample with a reduced thickness of a partial region of the sample by the charged particle beam. At the time of swatching, the portion adjacent to the thinned portion of the micro sample piece forms an inclined portion inclined with respect to the thinned portion.

Description

Charged particle beam apparatus and sample processing method

The present invention relates to a charged particle beam apparatus for processing a sample using a charged particle beam, and a sample processing method using the charged particle beam.

For example, as one of the methods for analyzing the internal structure of a sample such as a semiconductor element or performing stereoscopic observation, a cross-sectional observation method is known that uses a lens tube mounted with a charged particle beam (Focused Ion Beam: FIB) and an electron beam. A charged particle beam composite device of a beam (Electron Beam; EB) column is used to perform cross-sectional formation processing by FIB and observation of the cross-section with a scanning electron microscope (Scanning Electron Microscope: SEM) (for example, refer to Patent Document 1).

There is known a method of constructing a three-dimensional image by repeating cross-section forming processing by FIB and cross-sectional observation by SEM. In this method, the three-dimensional form of the object sample can be analyzed in detail from various directions based on the reconstructed three-dimensional image. In addition, there is an advantage that other methods can reproduce an arbitrary cross-section of an object sample.

On the other hand, in principle, SEM has a limit in observation at high magnification (high resolution), and the information obtained is also limited to the vicinity of the sample surface. Therefore, in order to perform high-resolution observation at a higher magnification, a transmission electron microscope (Transmission Electron Microscopy: TEM) which transmits electrons to a sample processed into a thin film is also known. The above-described cross-sectional formation process by FIB is also effective in the production of thin-filmed fine samples (hereinafter, sometimes referred to as micro-samples) used for such TEM observation.

Conventionally, when producing a micro sample piece used for observation by TEM, a charged particle beam is irradiated to the tip portion of the sample in the thickness direction of the sample, for example, the thickness of the sample is reduced and the thickness of the sample is reduced. to make tiny samples.

For example, when thinning a sample in which a plurality of elements are stacked on a semiconductor substrate in the thickness direction, an SEM image of a machined cross section is observed while irradiating a charged particle beam, and the number of elements exposed in the machined cross section is counted. , thereby grasping the desired machining end point.

On the other hand, in order to reduce the processing fringe pattern (curtain effect) along the irradiation direction of the charged particle beam generated by the processing using the charged particle beam, it is also possible to incline from the thickness direction with respect to the sample. It is carried out by irradiating a charged particle beam in the direction of (for example, refer to Patent Document 2).

Patent Document 1: Japanese Patent Laid-Open No. 2008-270073

Patent Document 2: Japanese Patent Application Laid-Open No. 9-186210

However, in the above-described sample processing method (thin film forming method), since the thinned portion of the sample is etched, and the portion adjacent to this portion is not etched, a 90° buckling occurs. Step difference. and, When the charged particle beam is irradiated from a direction inclined with respect to the processed surface of the flaked portion in order to cope with the above-mentioned curtain effect, since the charged particle beam is shielded by the adjacent portion, shadows that cannot be irradiated by the charged particle beam are generated. area. Therefore, it is necessary to determine the processing width in consideration of the shadow area that is not irradiated by the charged particle beam, and therefore, it is necessary to irradiate the charged particle beam in a processing range larger than the desired processing width. Therefore, the processing time of the sample becomes long, and there is a possibility that a micro sample piece of a desired shape cannot be produced.

In addition, when thinning a sample in which a plurality of elements are stacked in the thickness direction on a semiconductor substrate, when counting the number of elements exposed by processing in order to grasp the processing end point, the above-mentioned hatching may occur. Under the influence of the area, the contrast of the processing surface is reduced, and the number of components cannot be accurately counted, so that the processing end point cannot be accurately grasped.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a charged particle beam apparatus capable of uniformly irradiating the entire micro sample piece with a reduced thickness of the sample, and a method for processing a sample with charged particles and can clearly grasp the machining end point during machining.

In order to solve the above-mentioned problems, in the aspect of the present embodiment, the following charged particle beam apparatus and sample processing method are provided.

That is, the charged particle beam apparatus of the present invention irradiates the sample with charged particles A sub-beam, a charged particle beam apparatus for producing a tiny sample piece, characterized in that the charged particle beam apparatus includes: a charged particle beam column capable of irradiating the sample with a charged particle beam; and a sample chamber that accommodates the charged particle beam column; and a sample piece holder capable of holding the sample, and when the charged particle beam is used to form a minute sample piece having a reduced thickness of a part of the region of the sample, A portion adjacent to the thinned portion of the micro sample piece forms an inclined portion inclined with respect to the thinned portion.

According to the charged particle beam apparatus of the present invention, the portion adjacent to the thinned portion of the micro sample piece forms the inclined portion inclined with respect to the thinned portion, and the cross-sectional shape of the element exposed in the inclined portion is proportional to the extending direction of the element The cross-sectional shape of the right-angled section is larger and more clearly seen, so that the number of elements can be counted accurately. Thereby, the processing end point of the sample with the charged particle beam can be determined easily and reliably.

In addition, the present invention is characterized in that the charged particle beam apparatus irradiates the argon ion beam so as to be parallel to the inclined portion.

The sample processing method of the present invention is a sample processing method for irradiating a sample with a charged particle beam to form a micro sample piece having a reduced thickness in a part of the sample, and the sample processing method is characterized in that There is an inclined portion forming process in which a plurality of removal regions are formed overlappingly in the thickness direction of the sample by irradiation of the charged particle beam, and the removal regions have a predetermined rule in the thickness direction. The processing thickness and the processing width in the width direction perpendicular to the thickness direction, the processing width is gradually reduced each time the removal area is overlapped, whereby the thinned portion of the micro sample piece is The adjacent portion is formed with respect to the thinned portion sloping slope.

According to the sample processing method of the present invention, since it is possible to form the inclined portion inclined with respect to the thinned portion in the portion adjacent to the thinned portion of the micro sample piece, in the subsequent process, the irradiation and the processing of the sample are performed. When using a reprocessing beam with a different irradiation angle of the charged particle beam, it is possible to eliminate the shadow area where the root portion of the micro sample piece is not irradiated with the argon ion beam, so that the entire area of the micro sample piece can be reliably irradiated with argon ion beam. As a result, it is possible to form a micro-sample in which the processing fringe pattern is reduced over the entire region of the micro-sample, and a clear observation image can be obtained.

In addition, the present invention is characterized in that the processed thickness and the processed width of each removal region in the inclined portion forming process are determined with reference to an SEM image of the inclined portion obtained by a scanning electron microscope.

In addition, the present invention is characterized in that the sample is formed by overlapping a plurality of embedded layers in the thickness direction inside the base material. In the inclined portion forming process, the number of the buried layers exposed in the inclined portion is counted using the SEM image to determine a processing end point.

The sample processing method is characterized in that, in the inclined portion forming process, the thinned portion and the inclined portion, which is a portion adjacent to the thinned portion, are set to be 10° or more and less than 90° from each other. tilt within the range.

In addition, the present invention is characterized in that the sample processing method further includes an argon beam irradiation step in which argon ions are irradiated toward the small sample piece so as to be parallel to the inclined portion bundle.

According to the present invention, it is possible to uniformly irradiate a charged particle beam to the entire micro sample piece having a reduced thickness of the sample and to clearly grasp the A charged particle beam apparatus and a sample processing method at the processing end point during processing.

10: Charged Particle Beam Device

11: Sample room

12: stage (sample stage)

13: Carrier drive mechanism

14: Converging ion beam irradiation optical system (charged particle beam irradiation optical system)

15: Electron beam irradiation optical system (charged particle beam irradiation optical system)

16: Detector

17: Gas Supply Department

18: Gas ion beam irradiation optical system (charged particle beam irradiation optical system)

19a: Needle

19b: Needle drive mechanism

20: Sink current detector

21: Display device

22: Computer

23: Input device

33: Sample stage

34: Columnar part

C: inclined part

P: Specimen holder

Q: Tiny sample piece

R: Secondary charged particle

S: sample piece

V: sample

12a: Bracket fixing table

13a: Moving Mechanisms

13b: Tilt mechanism

13c: Rotary Mechanism

14a: Ion source

14b: Ion optics

15a: Electron source

15b: Electron Optical Systems

17a: Nozzle

19: Specimen Displacement Unit

31: Components

G: gas

T: thickness direction

D: machining direction

En: remove area

Wn: Processing width

△W: reduce the width

Ene: end

Qs: Thinning part

FIG. 1 is a configuration diagram of a charged particle beam apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a sample processing method in stages.

FIG. 3 is an explanatory diagram showing a sample processing method in stages.

FIG. 4 is an explanatory diagram showing another example of a sample processing method.

Hereinafter, a charged particle beam apparatus as one embodiment of the present invention and a sample processing method using the charged particle beam apparatus will be described with reference to the accompanying drawings. In addition, each embodiment shown below is demonstrated concretely in order to understand the summary of invention better, and does not limit this invention unless otherwise specified. In addition, in order to facilitate the understanding of the features of the present invention, the drawings used in the following description may be enlarged for the sake of convenience, and the dimensional ratios and the like of the respective components are not necessarily the same as the actual ones.

FIG. 1 is a schematic configuration diagram showing a charged particle beam apparatus according to an embodiment of the present invention.

As shown in FIG. 1 , the charged particle beam apparatus 10 according to the embodiment of the present invention includes a sample chamber 11 capable of maintaining the inside in a vacuum state, and a stage 12 capable of placing a bulk sample V and a A sample piece holder P for holding the sample piece S is fixed inside the sample chamber 11; and a stage drive mechanism 13, which drives the stage 12.

The charged particle beam apparatus 10 includes a focused ion beam irradiation optical system 14 that irradiates a charged particle beam, eg, a focused ion beam (FIB), to an irradiation target within a predetermined irradiation area (ie, a scanning range) inside the sample chamber 11 . The charged particle beam apparatus 10 includes an electron beam irradiation optical system 15 for irradiating an electron beam (EB) to an irradiation target in a predetermined irradiation area inside the sample chamber 11 . The charged particle beam apparatus 10 includes a detector 16 that detects secondary charged particles (secondary electrons, secondary ions) R generated from the irradiation target by irradiation with a charged particle beam or an electron beam.

The charged particle beam apparatus 10 includes a gas ion beam optical system 18 for irradiating a gas ion beam (GB) to an irradiation target in a predetermined irradiation area inside the sample chamber 11 .

These convergent ion beam irradiation optical system 14 , electron beam irradiation optical system 15 , and gas ion beam optical system 18 are arranged so that their beam irradiation axes can intersect at substantially one point on stage 12 . That is, when the sample chamber 11 is viewed from the side, the condensing ion beam optical system 14 is arranged in the vertical direction, and the electron beam irradiation optical system 15 and the gas ion beam optical system 18 are respectively inclined by, for example, 45° with respect to the vertical direction. Orientation configuration. With such an arrangement, when the sample chamber 11 is viewed from the side, the beam irradiation axis of the gas ion beam (GB) is, for example, perpendicular to the beam irradiation axis of the electron beam (EB) irradiated from the electron beam irradiation optical system 15 . direction of intersection.

The charged particle beam apparatus 10 has a gas supply unit 17 that supplies the gas G to the surface of the irradiation target. Specifically, the gas supply part 17 is a nozzle 17a or the like having an outer diameter of about 200 μm.

The charged particle beam apparatus 10 includes a sample piece transfer unit 19 that takes out the sample piece S from the sample V fixed on the stage 12, holds the sample piece S, and transfers the sample piece S to the sample piece holder The needle 19a on the P and the needle drive mechanism 19b that drives the needle 19a to convey the sample S are constituted; The incoming current signal is sent to a computer for visualization.

The charged particle beam apparatus 10 includes a display device 21 , a computer 22 , and an input device 23 for displaying image data and the like based on the secondary charged particles R detected by the detector 16 .

In addition, the irradiation objects of the convergent ion beam irradiation optical system 14 and the electron beam irradiation optical system 15 are the sample V fixed on the stage 12, the sample piece S, the needle 19a and the sample piece holder existing in the irradiation area. P et al.

The charged particle beam apparatus 10 can perform imaging of an irradiated portion, various processes by sputtering (excavation, trimming, etc.), deposition of a film ( deposited film), etc. The charged particle beam apparatus 10 is capable of cutting out a sample piece S from the sample V, and forming a minute sample piece Q used for TEM observation from the cut out sample piece S (see FIG. 3 : for example, a thin sample, Needle-shaped samples, etc.), processing of analysis sample pieces by electron beam.

The charged particle beam apparatus 10 can obtain observation by thinning, for example, the leading end portion of the sample piece S placed on the sample piece holder P to a desired thickness (for example, 5 to 100 nm, etc.) suitable for transmission observation by a transmission electron microscope. Small sample piece Q used. The charged particle beam apparatus 10 can scan a charged particle beam or an electron beam by irradiating the surface of the object such as the sample piece S, the needle 19a, and the like. Observation of the surface of the irradiated object is performed while irradiating.

The sink current detector 20 has a preamplifier, amplifies the inflow current of the needle, and sends it to the computer 22 . A needle-shaped absorption current image can be displayed on the display device 21 based on a signal synchronized with the needle inflow current detected by the absorption current detector 20 and the scanning of the charged particle beam, and the needle shape and tip position can be determined.

The sample chamber 11 can be evacuated by an evacuation device (not shown) until the inside is brought into a desired vacuum state, and the desired vacuum state can be maintained.

The stage 12 holds the sample V. The stage 12 has a holder fixing table 12a that holds the sample piece holder P. As shown in FIG. The holder fixing table 12a may have a structure capable of mounting a plurality of sample piece holders P thereon.

The stage drive mechanism 13 is housed in the sample chamber 11 in a state of being connected to the stage 12 , and displaces the stage 12 with respect to a predetermined axis according to a control signal output from the computer 22 . The stage drive mechanism 13 includes at least a moving mechanism 13a that moves the stage 12 parallel to the X-axis and the Y-axis parallel to the horizontal plane and perpendicular to each other, and the Z-axis in the vertical direction perpendicular to the X-axis and the Y-axis. The stage drive mechanism 13 includes a tilt mechanism 13b for tilting the stage 12 around the X-axis or the Y-axis, and a rotation mechanism 13c for rotating the stage 12 around the Z-axis.

The condensing ion beam irradiation optical system 14 is fixed to the sample chamber 11 in such a manner that the beam emitting part (not shown) is positioned above the vertical direction of the stage 12 in the irradiation area inside the sample chamber 11 . face the stage 12 and make the optical axis parallel to the vertical direction. As a result, it is possible to irradiate the sample V, the sample piece S, and the needle 19a existing in the irradiation area, etc., which are placed on the stage 12 . The subject is irradiated with a charged particle beam from vertically upward to downward.

In addition, the charged particle beam apparatus 10 may have another ion beam irradiation optical system instead of the above-described condensing ion beam irradiation optical system 14 . The ion beam irradiation optical system is not limited to the optical system that forms the above-described convergent beam. The ion beam irradiation optical system may be, for example, a projection-type ion beam irradiation optical system in which a shaped beam having an opening shape of a stencil mask is formed by providing a stencil mask having a shaped opening in the optical system. According to such a projection-type ion beam irradiation optical system, a shaped beam having a shape corresponding to the processing area around the sample piece S can be formed with high accuracy, and the processing time can be shortened.

The condensing ion beam irradiation optical system 14 includes an ion source 14a for generating ions and an ion optical system 14b for condensing and deflecting ions extracted from the ion source 14a. The ion source 14a and the ion optical system 14b are controlled based on a control signal output from the computer 22, and the computer 22 controls the irradiation position and irradiation conditions of the charged particle beam.

The ion source 14a is, for example, a liquid metal ion source using liquid gallium or the like, a plasma type ion source, a gas electric field ionization type ion source, or the like. The ion optical system 14b includes, for example, a first electrostatic lens such as condenser lenses, an electrostatic deflector, a second electrostatic lens such as an objective lens, and the like. When a plasma-type ion source is used as the ion source 14a, high-speed processing with a large current beam can be realized, and it is suitable for taking out the sample piece S having a large size. For example, by using argon ions as the gas electric field ionization type ion source, it is also possible to irradiate the argon ion beam from the condensing ion beam irradiation optical system 14 .

The electron beam irradiation optical system 15 is fixed to the sample chamber 11 in the following manner: Inside the sample chamber 11 , the beam emitting portion (not shown) faces the stage 12 in an inclined direction inclined by a predetermined angle (for example, 60°) with respect to the vertical direction of the stage 12 in the irradiation area. And make the optical axis parallel to the oblique direction. As a result, the electron beam can be irradiated from upward to downward in the oblique direction to the irradiation target such as the sample V fixed on the stage 12, the sample piece S, and the needle 19a existing in the irradiation area.

The electron beam irradiation optical system 15 has an electron source 15a that generates electrons, and an electron optical system 15b that converges and deflects electrons emitted from the electron source 15a. The electron source 15 a and the electron optical system 15 b are controlled based on control signals output from the computer 22 , and the computer 22 controls the irradiation position and irradiation conditions of the electron beams. The electron optical system 15b has, for example, an electromagnetic lens, a deflector, and the like.

In addition, the arrangement of the electron beam irradiation optical system 15 and the condensing ion beam irradiation optical system 14 may be reversed, and the electron beam irradiation optical system 15 may be disposed in the vertical direction, and the condensed ion beam irradiation optical system 14 may be disposed relative to the vertical direction. The vertical direction is inclined by a predetermined angle in the inclined direction.

The gas ion beam optical system 18 irradiates, for example, a gas ion beam (GB) such as an argon ion beam. The gas ion beam optical system 18 can ionize argon gas and irradiate it at a low acceleration voltage of about 1 kV. Such a gas ion beam (GB) has a lower condensing property than a converging ion beam (FIB), so the etching rate for the sample piece S and the minute sample piece Q becomes low. Therefore, it is suitable for precise finishing of the sample S and the minute sample Q.

When a charged particle beam or an electron beam is irradiated to an irradiation target such as the sample V, the sample piece S, and the needle 19a, the detector 16 detects secondary radiation emitted from the irradiation target. The intensity of the charged particles (secondary electrons, secondary ions) R (that is, the amount of the secondary charged particles), and the information of the detected amount of the secondary charged particles R is output. The detector 16 is arranged inside the sample chamber 11 at a position where the amount of the secondary charged particles R can be detected, and is fixed to the sample, for example, at a position obliquely above the irradiation target such as the sample V and the sample piece S in the irradiation area. Sample room 11.

The gas supply unit 17 is fixed to the sample chamber 11 , and is disposed in the sample chamber 11 so as to have a gas injection unit (also referred to as a nozzle) facing the stage 12 . The gas supply unit 17 can supply the sample V and the sample piece S to selectively promote the charged particle beam (converged ion beam) to the sample V and the sample piece S according to the material of the sample V and the sample piece S. Etching gas for etching, deposition gas for forming deposited films of deposits such as metals or insulators on the surfaces of sample V and sample piece S, and the like.

The needle drive mechanism 19b constituting the sample piece transfer unit 19 is housed in the sample chamber 11 in a state of being connected to the needle 19a, and displaces the needle 19a in accordance with a control signal output from the computer 22. The needle drive mechanism 19b is integrally provided with the stage 12, and moves integrally with the stage 12 when, for example, the stage 12 is rotated about the tilt axis (ie, the X axis or the Y axis) by the tilt mechanism 13b.

The needle drive mechanism 19b includes a movement mechanism (not shown) that moves the needle 19a in parallel to the three-dimensional coordinate axes, and a rotation mechanism (not shown) that rotates the needle 19a around the central axis of the needle 19a. In addition, this three-dimensional coordinate axis is independent from the orthogonal three-axis coordinate system of the sample stage, and in the orthogonal three-axis coordinate system which is a two-dimensional coordinate axis parallel to the surface of the stage 12, the surface of the stage 12 is inclined In the case of the state and rotation state, the coordinate system is tilted and rotated.

The computer 22 at least irradiates the stage drive mechanism 13 and the condensed ion beam optically The system 14, the electron beam irradiation optical system 15, the gas supply unit 17, and the needle drive mechanism 19b are controlled.

In addition, the computer 22 is disposed outside the sample chamber 11, and is connected to the display device 21 and the input device 23 such as a mouse and a keyboard that outputs a signal corresponding to an input operation by an operator. The computer 22 collectively controls the operation of the charged particle beam apparatus 10 based on a signal output from the input device 23, a signal generated by a preset automatic operation control process, or the like.

The computer 22 converts the detection amount of the secondary charged particles R detected by the detector 16 into a luminance signal corresponding to the irradiation position while scanning the irradiation position of the charged particle beam, and the two-dimensional position distribution according to the detection amount of the secondary charged particle R Generates image data representing the shape of the irradiated object. In the absorption current image mode, the computer 22 detects the absorption current flowing in the needle 19a while scanning the irradiation position of the charged particle beam, thereby generating the display needle 19a from the two-dimensional positional distribution (absorption current image) of the absorption current. The shape of the absorbed current image data.

The computer 22 displays on the display device 21 a screen for performing operations such as enlargement, reduction, movement, and rotation of each image data together with each generated image data. The computer 22 displays on the display device 21 a screen for performing various settings such as mode selection and machining setting in automatic sequence control.

The sample processing method of the present invention using the charged particle beam apparatus 10 having the above-described configuration will be described.

FIG. 2 and FIG. 3 are explanatory diagrams showing a sample processing method in stages.

In addition, in the following embodiment, as a sample processing method, the An example in which the sample piece S supported on the sample piece holder P is thinned by a charged particle beam to form a fine sample piece Q for TEM observation is shown and described. In addition, as shown in FIG. 2( a ), the sample piece S is assumed to be, for example, a sample obtained by cutting out a region where a plurality of elements 31 , 31 . . . are formed on a sample V (see FIG. 1 ) made of a semiconductor substrate. In the sheet, the direction in which the elements 31 , 31 . . . are arranged is referred to as the thickness direction T, and the extension direction of the elements 31 at right angles to the thickness direction T is referred to as the width direction W. In addition, the direction at right angles to the thickness direction T and the width direction W is referred to as the machining direction D.

First, a sample piece S as a small region including an observation object is cut out from a sample V (see FIG. 1 ) composed of a semiconductor substrate by FIB processing. Then, the sample holder P (see FIG. 1 ) supports the sample S to be processed so that the thickness direction of the semiconductor substrate is the vertical direction (processing direction D) using the needle 19a (see FIG. 1 ). Then, as shown in FIG.2(b), the irradiation area|region is set to the sample piece S, and FIB is irradiated along the process direction D from the condensing ion beam irradiation optical system 14 (refer FIG. 1). Then, a first removal region E1 having a predetermined processing thickness along the thickness direction T of the sample piece S and a processing width W1 along the width direction W is formed. Thereby, for example, the end face of one element 31 is exposed at the end E1e on the root side of the first removal region E1.

Next, as shown in FIG. 2( c ), FIB is irradiated along the thickness direction T to the position overlapping the first removal area E1, that is, the position shifted from the first removal area E1 in the thickness direction T by a predetermined processing thickness, A second removal area E2 is formed. At this time, as the processing width W2 along the width direction W, a width which is shorter than the processing width W1 by a predetermined reduced width ΔW is set. As a result, the end E2e on the root side of the second removal area E2 is located more than the root of the first removal area E1 The end E1e on the part side is close to the position shifted toward the center side in the width direction W. As shown in FIG.

Then, as shown in FIG. 3( a ), a position in the thickness direction T overlapping with the n-th removal region En previously formed, that is, a position shifted from the n-th removal region En in the thickness direction T by a predetermined processing thickness The FIB is irradiated to form the (n+1)th removal region E(n+1). At this time, as the processing width W(n+1) in the width direction W, a width shorter than the processing width Wn of the previous n-th removal region En by a predetermined reduction width ΔW is set. In this way, the sample piece S is irradiated with FIB in the processing direction D, and a plurality of removal regions whose processing width is gradually reduced in the thickness direction T are formed overlappingly in the thickness direction T, whereby the thickness direction T of the sample piece S is reduced in size. Thickness of the tiny test piece Q.

By forming such a plurality of removal regions in which the processing width is reduced in steps, a thinned portion Qs having a reduced thickness is formed on the micro-sample Q. In addition, an inclined portion (a portion adjacent to the thinned portion) C (inclined portion forming process) is formed in a portion adjacent to the thinned portion Qs, that is, a portion where the ends of the respective removal regions are connected to the root side. The inclined portion C is, for example, an inclined surface inclined within a range of 10° or more and less than 90° with respect to the thickness direction T, and the surface of the inclined portion C may be formed parallel to the irradiation angle of the argon ion beam, for example. As an example, in the present embodiment, the inclined portion C is an inclined surface inclined by 20° with respect to the thickness direction T. As shown in FIG. Here, in the range of 10° or more and less than 90°, by entering the beam at a small incident angle of less than 90°, the damage layer of the beam incident on the sample can be made shallow. As a result, since the damaged layer is made shallow, the processing end point at the time of processing can be clearly grasped even for a sample with a fine element size.

In addition, in the embodiment shown in FIG. 2 and FIG. 3 , the test is passed so that the The FIB is scanned and irradiated so that the processing width Wn in the width direction W of the sample S is gradually reduced to form the inclined portion (the portion adjacent to the thinned portion) C, but the scanning method of the FIB is not limited to this.

For example, in the example of scanning of the FIB shown in FIG. 4 , the processing width Wn of the removal region En along the width direction W of the sample piece S, which is the thinned portion Qs, is made constant. Then, the FIB is continuously scanned from the root side of each removal region En to a direction inclined within a range of 10° or more and less than 90° with respect to the thickness direction T. Thereby, the inclined portion C is formed in the area where the FIB is scanned in the direction inclined with respect to the thickness direction T. As shown in FIG. The machining width Wn along the inclined portion C is gradually increased in steps. Here, as the scanning method of the FIB, a vector scan in which the scanning direction of the FIB is changed from the width direction of the sample piece S to a direction inclined with respect to the thickness direction T is used.

Alternatively, a first rectangular irradiation area may be set in the width direction of the sample piece S, a second rectangular irradiation area may be set in a direction inclined with respect to the thickness direction T, and raster scan (raster scan) may be used in the respective irradiation areas. ) or bitmap scan.

Other than that, the scanning direction of the FIB in the trapezoidal region divided by the thinned portion Qs of the micro-sample Q and the inclined portion C, which is a portion adjacent to the thinned portion Qs, is not particularly limited, as long as it can be formed as In the inclined portion C of the portion adjacent to the thinned portion Qs, the removed region can be formed by scanning the FIB in any direction.

As described above, in the process of forming the plurality of removal regions in which the processing width is gradually reduced, the electron beam irradiation optical system 15 is irradiated at an arbitrary timing. EB was shot, and the SEM image of the inclined part C was obtained. Then, by observing the obtained SEM image and counting the number of elements 31 , 31 . . . exposed in the inclined portion C, the processing end point in the thickness direction T of the FIB can be determined. The cross-sectional shape of the elements 31 , 31 . . . exposed in the inclined portion C can be seen larger and more clearly than the sectional shape of the elements exposed in the cross-section along the thickness direction T, for example, so that it is possible to accurately identify the cross-sectional shape of the elements 31 , 31 . . . The number is counted.

Also, for example, the computer 22 can automatically count the elements 31 , 31 . . . exposed in the inclined portion C from the acquisition of the SEM image, and feed back the results to the irradiation conditions of the FIB with respect to the sample piece S, thereby enabling automation. The micro sample piece Q in which the inclined part C is connected to the root part side is formed.

As a specific example of such an automated processing end point detection method, the number of elements 31 , 31 . . . that appear on the design at the observation target position (exposed in the inclined portion C) is input to the computer 22 in advance. The predetermined number of occurrences of such elements 31 can be grasped from the design data of the integrated circuit formed in the sample V, and the like.

Then, image comparison software or the like executed by the computer 22 counts the number of elements 31 appearing in the inclined portion C by repeating the formation of the removed area by FIB irradiation and the acquisition of the irradiation SEM image. Then, when the predetermined number of appearances of the elements 31 input to the computer 22 in advance matches the number of elements 31 appearing in the inclined portion C based on the acquisition of the actual SEM image, this is recognized as the processing end point and the irradiation of the FIB is terminated.

In addition, as another specific example of the automatic processing end point detection method, when the sample piece S is cut out from the sample (semiconductor substrate) V (see FIG. 1 ) by FIB, the SEM image of the side wall of the sample piece S is obtained. picture. Then, by the computer 22 The executed image comparison software or the like counts the number of elements 31 exposed in the side wall of the sample sheet S. Alternatively, the number of elements 31 exposed in the cut end face of the sample V after the sample piece S is cut out, the cutting of the sample piece S based on the design data of the integrated circuit formed on the sample V, or the like may be determined. The number of elements 31 on the design of the out part is counted.

In this way, the actual elements 31 appearing in the inclined portion C by repeating the formation of the removed region by FIB irradiation and the acquisition of the irradiation SEM image are subtracted from the total number of elements 31 of the sample sheet S recognized by the computer 22 . When the number of elements 31 to be left in the sample sheet S, which is input to the computer 22 in advance, matches the number of elements 31 to be left in the sample sheet S, this is recognized as the processing end point, and the irradiation of the FIB is terminated.

Next, as shown in FIG. 3( b ), for example, a gas ion beam such as an argon ion beam is irradiated on the micro-sample Q at an angle parallel to the surface of the inclined portion C, thereby reducing the processing caused by processing using the FIB. Fringe pattern (curtain effect) (Argon beam irradiation engineering).

In this argon beam irradiation process, argon gas is ionized from the gas ion beam optical system 18 (see FIG. 1 ), and the entire region of the micro sample Q is irradiated with an argon ion beam at a low accelerating voltage of, for example, about 1 kV. At this time, it is preferable to irradiate the micro-sample Q with EB from the electron beam irradiation optical system 15 , and perform finishing of the micro-sample Q by an argon ion beam based on the obtained SEM image. The detection of the processing end point at this time can also be applied to the processing end point detection procedure at the time of processing the micro sample piece Q by the above-mentioned FIB. Thereby, automation of the argon beam irradiation process can be performed.

In such an argon beam irradiation process, as a The portion adjacent to the root portion is formed with an inclined portion C that is inclined within an angular range of 10° or more and less than 90° with respect to the thickness direction T, so that it is possible to reduce the thickness of the sample piece S and reduce the thickness of the micro sample. The entire area of the sheet Q was uniformly irradiated with the argon ion beam.

That is, as shown in FIG. 1 , the gas ion beam optical system 18 is arranged so that the beam irradiation axis of the gas ion beam (GB) is aligned with, for example, electrons irradiated from the electron beam irradiation optical system 15 when the sample chamber 11 is viewed from the side. The direction in which the beam irradiation axes of the beam (EB) intersect perpendicularly. Therefore, when the thickness direction T is at right angles to the width direction W of the micro-sample Q, for example, a shadow region in which the root portion of the micro-sample Q is not irradiated with the argon ion beam is generated.

However, by forming the inclined portion C inclined in the range of, for example, 10° or more and less than 90° in the micro sample piece Q in accordance with the argon ion beam irradiated at an angle inclined with respect to the thickness direction T as in the present embodiment, The shadow region where the root portion of the micro-sample Q is not irradiated with the argon ion beam can be eliminated, and the entire region of the micro-sample Q can be reliably irradiated with the argon ion beam. Thereby, it is possible to form a sample piece for TEM observation in which the processing fringe pattern is reduced in the entire region of the micro sample piece Q and a clear observation image can be obtained.

In addition, as shown in FIG. 3( c ), from the direction opposite to the machining direction in the thickness direction T described above, a plurality of removal regions in which the machining width in the width direction W is reduced in stages can be formed, thereby forming a plurality of removal regions with A small sample piece Q of the thinned portion Qs with reduced thickness on both sides.

The embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the invention described in the claims and the scope of their equivalents.

31‧‧‧Components

C‧‧‧Slope

D‧‧‧Machining direction

E1~E(n+1)‧‧‧Removal area

E1e~Ene‧‧‧End

EB‧‧‧Electron Beam

Q‧‧‧Micro sample

Qs‧‧‧Thinning part

S‧‧‧Sample

T‧‧‧Thickness direction

W‧‧‧Width direction

Wn‧‧‧Machining width

Claims (6)

A charged particle beam device, which irradiates a charged particle beam toward a sample to make a tiny sample piece, characterized in that it has: a charged particle beam lens barrel, which can irradiate the charged particle beam toward the sample; a sample chamber, which housing the charged particle beam column; and a sample holder capable of holding the sample when a minute sample piece having a reduced thickness of a part of the sample is formed by the charged particle beam An inclined inclined portion is formed at the root portion of the micro sample piece, and by providing the inclined portion to the root portion of the micro sample piece, in order to reduce the formation of the micro sample by the charged particle beam When the argon ion beam is irradiated to the micro sample piece, the argon ion beam is formed so as not to be blocked even at the root portion of the micro sample piece, and the charged The argon ion beam was irradiated to the fine sample piece in the direction in which the particle beams crossed and parallel to the inclined portion, and the processing streaks were reduced in the entire area of the fine sample piece. The charged particle beam apparatus according to claim 1, wherein the inclined portion is formed by referring to an SEM image of the inclined portion obtained by a scanning electron microscope. A method for processing a sample, which is a method for processing a sample by irradiating a charged particle beam toward a sample to form a micro sample piece having a reduced thickness in a partial region of the sample, characterized by comprising a step of forming an inclined portion In this inclined portion forming process, a plurality of removal regions are formed overlappingly in the thickness direction of the sample by irradiation of the charged particle beam, and the removal regions have a predetermined thickness along the thickness direction of the sample. The processing thickness and the processing width in the width direction perpendicular to the thickness direction are reduced in stages by reducing the processing width each time the removal area is overlapped, thereby reducing the thickness of the micro sample piece. A portion adjacent to a portion forms an inclined portion inclined with respect to the thinned portion; the sample processing method further includes an argon ion beam irradiation process in which the inclined portion is provided to the above-mentioned argon ion beam irradiation process. Therefore, when the argon ion beam is irradiated to the micro sample piece in order to reduce the processing fringes generated when the micro sample piece is formed by the charged particle beam, the argon ion beam is formed as It is not blocked even at the root portion of the micro sample piece, and the micro sample piece is irradiated with an argon ion beam from a direction intersecting the charged particle beam and parallel to the inclined portion. Machining streaks were reduced over the entire area of the aforementioned micro coupons. The sample processing method according to claim 3, wherein the processing thickness of each removed region in the inclined portion forming process is The degree and the processing width were determined with reference to an SEM image of the inclined portion obtained by a scanning electron microscope. The sample processing method according to claim 4, wherein the sample is formed by overlapping a plurality of embedded layers in the thickness direction inside the base material, and in the inclined portion forming step, The processing end point is determined by counting the number of the buried layers exposed in the inclined portion using the SEM image. The sample processing method according to any one of claims 3 to 5, wherein, in the inclined portion forming process, the thinned portion and a portion adjacent to the thinned portion are The inclined portions are inclined to each other within a range of 10° or more and less than 90°.

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