JP7718948B2 - Cathode unit for magnetron sputtering device and magnetron sputtering device - Google Patents

Description

The present invention relates to a cathode unit for a magnetron sputtering apparatus used to form a predetermined thin film on a substrate to be processed using the magnetron sputtering method, and to the magnetron sputtering apparatus.

A magnetron sputtering device has a cathode unit, which generally has a magnet unit located below the sputtering surface of the target, which is placed facing the vacuum chamber containing the substrate to be processed. A rare gas such as argon gas is introduced into the vacuum chamber, which is filled with a vacuum atmosphere. When a negative DC or AC voltage is applied to the target to sputter the target's sputtering surface, ionized electrons and secondary electrons generated by sputtering are captured in the space above the sputtering surface, increasing the electron density and the probability of collisions between electrons and rare gas molecules, thereby increasing plasma density.

When forming a film on a rectangular substrate such as a glass substrate, a target with the same contour as the substrate is typically used. The magnet unit typically used in this case includes a central magnet arranged linearly on one side of a rectangular support plate (yoke) parallel to the target, and peripheral magnets with equally spaced, parallel straight sections on both sides of the central magnet and bridging sections that bridge the free ends of the straight sections, surrounding the central magnet, with the polarity of the upper (target side) side reversed (see Patent Document 1). As a result, if the longitudinal direction of the central magnet is the X-axis direction and the Y-axis direction perpendicular to the X-axis direction, a leakage magnetic field acts in the space above the sputtering surface such that a line passing through the position where the vertical component of the magnetic field is zero extends in the X-axis direction and closes in a racetrack shape, generating a racetrack-shaped plasma in the space between the sputtering surface and the substrate (the space above the sputtering surface).

Electrons in the plasma (including secondary electrons) are bent and reoriented by the electromagnetic field at both ends of the magnet unit in the X-axis direction, and move in a clockwise or counterclockwise circular orbit along the racetrack depending on the magnetic properties of the central magnet and the upper side of the peripheral magnets. It is known that as electrons in the plasma are bent and reoriented by the electromagnetic field, some inertial motion remains. In such cases, the plasma tends to spread (in the Y-axis direction) in the corner regions of the target located diagonally, where inertial motion remains, resulting in a problem of greater erosion than in other corner regions where inertial motion does not remain. For this reason, if electrons in the plasma are forced to move in a fixed clockwise or counterclockwise circular orbit along the racetrack, the sputtering surface of the target will be worn away unevenly, resulting in poor target utilization efficiency.

Japanese Patent Application Laid-Open No. 2008-127601

In view of the above, the present invention aims to provide a cathode unit for a magnetron sputtering device and a magnetron sputtering device that can more uniformly erode the target area as sputtering progresses, thereby increasing the target utilization efficiency.

To solve the above problems, the present invention provides a cathode unit for a magnetron sputtering apparatus that includes a magnet unit installed below and facing away from the sputtering surface of a target placed facing the inside of a vacuum chamber. The magnet unit has a linearly arranged central magnet and peripheral magnets surrounding the central magnet with their upper polarities reversed, and a line passing through the position where the vertical component of the magnetic field is zero extends along the longitudinal direction of the central magnet, creating a racetrack-like leakage magnetic field that acts on the space above the sputtering surface. When racetrack-shaped plasma is generated in the space above the sputtering surface, the direction of electrons in the plasma moving in a clockwise or counterclockwise orbit along the racetrack can be freely reversed depending on the magnetic properties of the upper sides of the central magnet and peripheral magnets.

This invention employs a configuration that allows the direction of electrons in the plasma to be freely reversed and the direction in which the electrons' inertial motion remains to be reversed around the X-axis. For example, by initially moving the electrons in the plasma in a clockwise orbit, when a wide area of the corner region of the target located diagonally opposite the target, where the electrons' inertial motion remains, is eroded, the direction of the electrons in the plasma is reversed to move in a counterclockwise orbit. This allows the corner region of the target located diagonally opposite the target to be eroded over a wide area. As a result, compared to the conventional example described above, uneven wear of the target is suppressed and the erosion area of the target as sputtering progresses can be made more uniform. In this case, it is more effective to reciprocate the magnet unit in the Y-axis direction with a predetermined stroke length. The direction of electrons in the plasma can be reversed as needed, for example, after film formation on one or a predetermined number of substrates is completed, or when the integrated power to the target reaches a predetermined value.

In this invention, the first magnet unit applies the leakage magnetic field to the space above the sputtering surface, the second magnet unit is the magnetized portion of the central and peripheral magnets of the first magnet unit, and a swapping means is provided to swap the leakage magnetic field acting on the space above the sputtering surface between the first and second magnet units, thereby freely reversing the direction of electrons in the plasma. This allows for a configuration in which the direction of electrons in the plasma moving in a clockwise or counterclockwise orbit along a racetrack can be periodically reversed. In this case, the swapping means can be configured by arranging the first and second magnet units side by side in the same plane and providing a drive unit that moves the first and second magnet units together in one direction within the same plane. Alternatively, the swapping means can be configured by arranging the first and second magnet units on both the front and back sides of a support plate and providing a rotation unit that rotates the support plate. On the other hand, it is also possible to use a configuration in which the central magnet and peripheral magnets of the magnet unit are made up of electromagnets, and the direction of electrons in the plasma can be freely reversed by changing the direction of the current flowing through each electromagnet.

To solve the above problems, the magnetron sputtering device of the present invention comprises a cathode unit for the magnetron sputtering device, a vacuum chamber in which the target of the cathode unit is installed facing the interior of the vacuum chamber and the substrate to be processed is placed facing the vacuum chamber in the space in front of the sputtering surface, a sputtering power supply that supplies power to the target, and a gas introduction means that allows the introduction of sputtering gas into the vacuum chamber in a vacuum atmosphere, and is configured to reverse the direction of electrons in the plasma depending on the integrated power supplied to the target.

1 is a schematic cross-sectional view of a magnetron sputtering apparatus including a cathode unit according to a first embodiment. FIG. 2 is a plan view showing a main part of the cathode unit shown in FIG. 1 . FIG. 3 is an enlarged plan view of a portion of the cathode unit shown in FIG. 2 . FIG. 10 is a schematic cross-sectional view of a magnetron sputtering apparatus including a cathode unit according to a second embodiment. 1A to 1D are diagrams illustrating the procedure for reversing the direction of electrons in plasma.

The following describes, with reference to the drawings, an embodiment of a cathode unit for a magnetron sputtering apparatus and a magnetron sputtering apparatus of the present invention, using as an example a so-called multi-target magnetron sputtering apparatus in which the substrate to be processed is a large-area glass substrate (hereinafter referred to as "substrate Sw") used in the manufacture of flat panel displays, and in which multiple targets with rectangular contours in one direction are arranged side by side at equal intervals. In the following, terms indicating directions such as up and down are based on Figure 1, which shows the installation position of the magnetron sputtering apparatus SM, and the vertical direction from the sputtering surface of the target toward the substrate Sw is the Z-axis direction, the longitudinal direction of the central magnet described below is the X-axis direction, and the Y-axis direction is perpendicular to the X-axis direction.

1 and 2, the magnetron sputtering apparatus SM of this embodiment includes a vacuum chamber 1 defining a film formation chamber 11. An exhaust port 12 is provided in the wall of the vacuum chamber 1, and an exhaust pipe 13 extending from a vacuum exhaust unit Pu, which may be configured as a rotary pump, a dry pump, a turbomolecular pump, or the like, is connected to the exhaust port 12, thereby evacuating the film formation chamber 11 and maintaining a predetermined pressure (e.g., 1×10 ⁻⁵ Pa). Gas supply ports 21 a and 21 b are also provided in the wall of the vacuum chamber 1, and gas pipes 23 a and 23 b, each having a mass flow controller 22 a and 22 b, are connected to the gas supply ports 21 a and 21 b, respectively, allowing a rare gas such as argon gas, and a reactive gas such as oxygen gas, at a controlled flow rate, to be introduced into the film formation chamber 11. These gas supply ports constitute the gas introduction means of this embodiment.

A substrate transport means 3 is provided in the upper space within the vacuum chamber 1. The substrate transport means 3 includes a carrier 31 that holds the substrate Sw with its underside (film formation surface) open, and a drive source (not shown) that can transport the carrier 31 in the Y-axis direction. Since a known device can be used as the substrate transport means 3, a detailed description thereof will be omitted here. The cathode unit CU1 of the first embodiment is provided in the lower part of the vacuum chamber 1, facing the substrate Sw held by the carrier ₃₁ that has been transported to a predetermined position within the film formation chamber 11. The cathode unit _CU1 includes four targets ₄₁ to ₄₄ that are arranged side by side at equal intervals in the Y-axis direction so that their upper surfaces (sputtering surfaces 41) when not in use are positioned within the XY plane, and magnet units ₅₁ to ₅₅ that are at least one more than the number of targets ₄₁ to ₄₄ (five in this embodiment) and are respectively arranged in the space below the targets ₄₁ to ₄₄ (outside the vacuum chamber). The targets 4 ₁ to 4 ₄ are manufactured according to the composition of the film to be formed on the underside of the substrate Sw, and have the same approximately rectangular parallelepiped shape, and the dimensions (length in the X-axis direction and width in the Y-axis direction) of each target 4 ₁ to 4 ₄ are set so that the outline of each of the juxtaposed targets 4 ₁ to 4 ₄ is slightly larger than the substrate Sw when placed directly facing the substrate Sw. A copper backing plate 42 is bonded to the underside of each target 4 ₁ to 4 ₄ via a bonding material (not shown) such as indium, and the targets are placed in the vacuum chamber 1 in an electrically insulated and coolable state. Adjacent targets 4 ₁ , 4 ₂ and 4 ₃ , 4 ₄ are paired, and outputs 61 from an AC power supply 6 acting as a sputtering power supply are connected to each of the pairs of targets 4 ₁ to 4 ₄ , and AC power of a predetermined frequency (for example, 1 kHz to 100 kHz) can be applied between each pair of targets 4 ₁ , 4 ₂ and 4 ₃ , 4 ₄ by the AC power supply 6. Depending on the target type, DC power having a negative potential can also be applied to each of the targets 4 ₁ to 4 ₄ .

Each magnet unit ₅₁ to ₅₅ has the same configuration, is arranged parallel to the backing plate 42, and includes a support plate 51 (yoke) made of a flat plate of magnetic material. The center of the top surface of the support plate 51 includes a central magnet 52 arranged linearly in the Y-axis direction, and peripheral magnets 53 surrounding the central magnet 52, with straight sections 53a and 53b extending parallel to and equidistant from both sides of the central magnet 52 and bridging sections 53c bridging the free ends of both straight sections 53a and 53b, with their polarities on the target side reversed (e.g., the central magnet 52 has a south pole and the peripheral magnet 53 has a north pole). The central magnet 52 and peripheral magnets 53 are either integrally manufactured from neodymium magnets or the like, or are configured by arranging magnet pieces made from neodymium magnets or the like, and are designed so that the central magnet 52 and peripheral magnets 53 have approximately the same volume when converted to the same magnetization. This causes a leakage magnetic field Mf to act in the space within the film formation chamber 11 between the sputtering surface 41 of each target 4 ₁ - 4 ₄ and the underside of the substrate Sw, with a line passing through the position where the vertical component of the magnetic field is zero extending in the Y-axis direction and closing in a racetrack shape. Furthermore, a nut member 54 protrudes from the underside of the support plate 51 of each magnet unit 5 ₁ - 5 ₅ , and a feed screw Fs connected to a motor Mt is threadedly engaged with each nut member 54. During sputtering, each magnet unit 5 ₁ - 5 ₅ can be reciprocated in the Y-axis direction with a predetermined stroke length, and these motor Mt and feed screw Fs constitute the drive unit of this embodiment. Note that each magnet unit 5 ₁ - 5 ₅ may also be reciprocated in the X-axis direction with a predetermined stroke length.

When a film is formed on the underside of a substrate Sw using the magnetron sputtering apparatus SM, the substrate Sw is transported by the substrate transport means 3 to a predetermined position in the film formation chamber 11 directly facing the targets ₄₁ to ₄₄ , and the film formation chamber 11 is evacuated to a predetermined pressure. Once the predetermined pressure is reached in the film formation chamber 11, a rare gas (or a reactive gas, if necessary) is introduced while controlling the flow rate with the mass flow controllers _22a and _22b , and AC power is applied between each pair of targets 41 to 44 by the AC power source 6. This generates a racetrack-shaped plasma Pm above the sputtering surface 41 of each target ₄₁ to _44. The sputtering surface 41 is then sputtered by ions of the rare gas ionized by the plasma Pm, and sputtered particles scattered from the sputtering surface 41 according to a predetermined cosine law adhere to and deposit on the underside of the substrate Sw to form a film.

As shown in FIG. 3 , electrons (secondary electrons) in the plasma Pm are bent and reoriented by the electromagnetic fields at both ends of each magnet unit 5 ₁ - 5 ₅ in the X-axis direction, moving in a clockwise or counterclockwise orbit along a racetrack depending on the magnetic properties of the central magnet 52 and the upper side of the peripheral magnet 53. However, as the electrons in the plasma Pm are bent and reoriented by the electromagnetic fields, some inertial motion remains (note that the dashed-dotted lines in FIG. 3 schematically show the orbital motion of the electrons). In such a case, in the corner regions of the diagonally positioned targets 4 ₁ - 4 ₄ where inertial motion remains (the upper left regions in FIG. 3 ), the plasma Pm tends to spread in the Y-axis direction, resulting in a problem of greater erosion than in other corner regions where inertial motion does not remain. For this reason, it is necessary to prevent uneven wear on the sputtering surfaces 41 of the targets 4 ₁ - 4 ₄ , which would reduce the utilization efficiency of the targets 4 ₁ - 4 ₄ .

As described above, in this embodiment, the number of magnet units ₅₁ to ₅₅ is one more than the number of targets ₄₁ to ₄₄ , and the polarities of the central magnet 52 and peripheral magnet 53 of the magnet units ₅₁ to ₅₅ on the target ₄₁ to ₄₄ side are different between adjacent magnet units ₅₁ to ₅₅ (see FIGS. 1 and 2). When forming a film on the substrate Sw by sputtering, the drive units Mt and Fs position the magnet units ₅₂ to ₅₅ below each target ₄₁ to ₄₄ , respectively, and one magnet unit ₅₁ is positioned outward from one side end of the target ₄₁ located at one end in the Y-axis direction (the left end in FIG. 2). In this case, each magnet unit ₅₁ to ₅₅ may also reciprocate in the X-axis direction by a predetermined stroke length, without the leakage magnetic field Mf from one magnet unit ₅₁ acting on the sputtering surface 41 of the target ₄₁ . Then, for example, when the integrated power to the targets ₄₁ to ₄₄ measured by the AC power supply 6 reaches a predetermined value, the magnet units ₅₁ to ₅₄ are positioned below each of the targets ₄₁ to ₄₄ by the driving means Mt, Fs, and one of the magnet units ₅₅ is positioned outward from the other end of the target ₄₄ located at the other end in the Y-axis direction (the right end in FIG. 2). As a result, the direction of electrons in the plasma Pm generated in the space above each of the targets ₄₁ to ₄₄ is reversed, for example, from a state in which they move in a clockwise orbit to a state in which they move in a counterclockwise orbit.

As described above, in this embodiment, the magnet unit ₅₅ located on the other side in the Y-axis direction is the first magnet unit, and the magnet unit ₅₁ located on one side in the Y-axis direction is the second magnet unit, and the drive units Mt and Fs constitute a swapping means for swapping the leakage magnetic field Mf acting on the space above the sputtering surface 41 between the first magnet unit ₅₅ and the second magnet unit ₅₁ , thereby freely reversing the direction of electrons in the plasma. As a result, by initially moving the electrons in the plasma in a clockwise orbit, when a wide area is eroded in the corner regions of each of the diagonally positioned targets ₄₁ to ₄₄ (the upper left region in FIG. 3 ), where the electrons' inertial motion remains, the direction of the electrons in the plasma is reversed so that they move in a counterclockwise orbit, and the corner regions of the other diagonally positioned targets ₄₁ to ₄₄ (the upper right region in FIG. 3 ) can be eroded over a wide area. As a result, compared to the conventional example, uneven wear of the targets 4 ₁ to 4 ₄ is suppressed, and as sputtering progresses, the erosion areas of the targets 4 ₁ to 4 ₄ can be made more uniform. Note that the reversal of the direction of electrons in the plasma Pm can be carried out as appropriate, for example, every time film formation on one or a specified number of substrates Sw is completed, or when the integrated power to each of the targets 4 ₁ to 4 ₄ reaches a predetermined value.

Although the above describes an embodiment of the present invention, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, the magnet unit ₅₅ located on the other side in the Y-axis direction is the first magnet unit, the magnet unit ₅₁ located on one side in the Y-axis direction is the second magnet unit, and the drive units Mt and Fs that move the magnet unit ₅₁ and the magnet unit ₅₅ together with the other magnet units ₅₂ to ₅₄ in the XY plane are used as swapping means that swap the leakage magnetic field Mf acting on the space above the sputtering surface 41. However, the present invention is not limited to this. For example, the magnet units ₅₁ to ₅₅ may be configured to be able to move independently in the Y-axis direction.

As shown in Figures 4 and 5, in which the same components and elements are designated by the same reference numerals, the cathode unit _Cu2 of the second embodiment includes magnet units _50-1 to _50-4 , and each of the magnet units _50-1 to _50-4 includes a support 500. Support plates 51 are provided on both the front and back sides of the support 500, and each support plate 51 is provided with a central magnet 52 and a peripheral magnet 53, with the polarities reversed between the front and back sides of the support 500. In this case, a rotation shaft 501 extending in the X-axis direction is connected to the support 500, and the rotation shaft 501 is connected to a motor 502. These components, such as the rotation shaft ₅₀₁ and the motor 502, constitute the rotation unit of this embodiment. Although not shown in detail, the magnet units _50-1 to _50-4 are provided with a drive means for moving them up and down in the Z-axis direction so that they can be turned upside down without interfering with _other components. Then, by rotating the support 500 using the rotation units 501 and 502 according to Figures 5(a) to 5(d), the polarity of the central magnet 52 and the peripheral magnet 53 of each magnet unit ₅₀₁ to ₅₀₄ on the target ₄₁ to ₄₄ side is reversed, thereby reversing the direction of the electrons in the plasma so that they move in a clockwise or counterclockwise orbit.

In the above embodiment, the central magnet 52 and peripheral magnets 53 constituting each of the magnet units _5-1 to _5-5 are described as being permanent magnets such as neodymium magnets, but the present invention is not limited thereto. The central magnet 52 and peripheral magnets 53 can also be configured as electromagnets. In this case, simply changing the direction of current flow can swap the polarity of the central magnet 52 and peripheral magnet 53 of each of the magnet units _5-1 to _5-5 on the target _4-1 to _4-4 sides, thereby reversing the direction of electrons in the plasma so that they move in a clockwise or counterclockwise orbit. Furthermore, in the above embodiment, the present invention is described as being applied to a so-called multi-target magnetron sputtering apparatus in which multiple targets having rectangular contours are arranged side by side at equal intervals and a magnet unit is provided corresponding to each target. However, the present invention is not limited thereto. The present invention can also be applied to a so-called multi-magnet magnetron sputtering apparatus in which multiple magnet units are provided in the space below a single target.

Cu ₁ , Cu ₂ ... cathode unit, SM... magnetron sputtering apparatus, 1... vacuum chamber, 4 ₁ to 4 ₄ ... target, 41... sputtering surface, 5 ₁ to 5 ₅ , 50 ₁ to 50 ₄ ... magnet unit, Mf... leakage magnetic field, 52... central magnet, 53... peripheral magnet, Pm... plasma, 5 ₅ ... first magnet unit (component of swap means), 5 ₁ ... second magnet unit (component of swap means), Fs... feed screw (component of drive unit), Mt... motor (component of drive unit), 500... support, 501... rotating shaft (component of rotation unit), 502... motor (component of rotation unit), 6... AC power supply (sputtering power supply), 22a, 22b... mass flow controller (component of gas introduction means), 23a, 23b... gas pipe (component of gas introduction means).

Claims (2)

A cathode unit for a magnetron sputtering apparatus includes a magnet unit provided below and facing away from a sputtering surface of a target placed facing the inside of a vacuum chamber, the magnet unit having a linearly arranged central magnet and peripheral magnets surrounding the central magnet with their upper polarities reversed, and a leakage magnetic field acting on a space above the sputtering surface such that a line passing through a position where the vertical component of the magnetic field is zero extends along the longitudinal direction of the central magnet and closes in a racetrack shape,
When a racetrack-shaped plasma is generated in the space above the sputtering surface, the direction of electrons in the plasma moving in a clockwise or counterclockwise orbit along the racetrack can be freely reversed depending on the magnetic properties of the central magnet and the upper side of the peripheral magnets,
The magnet unit that applies the leakage magnetic field to the space above the sputtering surface is designated as a first magnet unit, and the magnetism of the central magnet and peripheral magnet of the first magnet unit is changed to that of the upper side thereof to designate a second magnet unit, and a swapping means is provided for swapping the leakage magnetic field that applies to the space above the sputtering surface between the first magnet unit and the second magnet unit, thereby making it possible to freely reverse the direction of electrons in the plasma,
A cathode unit for a magnetron sputtering apparatus, characterized in that the first magnet unit and the second magnet unit are provided on both the front and back sides of a support, respectively, and the swap means is configured by providing a rotation unit that rotates the support . 10. A magnetron sputtering apparatus comprising: a cathode unit for a magnetron sputtering apparatus according to claim 1 ; a vacuum chamber in which the target of the cathode unit is installed facing the interior of the vacuum chamber and in which a substrate to be processed is placed opposite the target in the space in front of the sputtering surface; a sputtering power supply for supplying power to the target; and gas introduction means for enabling the introduction of sputtering gas into the vacuum chamber in a vacuum atmosphere, wherein the magnetron sputtering apparatus is configured to reverse the direction of electrons in the plasma in accordance with the integrated power supplied to the target.