Cathode unit for magnetron sputtering device and magnetron sputtering device

Abstract

To provide a magnetron sputtering apparatus cathode unit CU1 capable of further equalizing the erosion area of a target with the progress of sputtering to enhance the utilization efficiency of the target.SOLUTION: A magnetron sputtering apparatus cathode unit includes a magnet unit 51- 55 facing in a direction opposite to the sputtering surfaces 41 of targets 41-44 arranged at a posture facing the inside of a vacuum chamber 1 and provided on the lower side. The magnet unit including a central magnet 52 linearly arranged and a peripheral magnet 53 surrounding the periphery of the center magnet so as to change polarities on the upper sides acts a stray magnetic field Mf having lines passing through a position having zero of the vertical component of a magnetic field, extended in the longitudinal direction of the central magnet and closed in a race track shape on a space above the sputtering surface. When generating race track shaped plasma Pm in the space above the sputtering surface, electrons in the plasma travelling on a clockwise or counter clockwise orbit along a race track according to the upper side magnetisms of the central and peripheral magnets form reversible directions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cathode unit for a magnetron sputtering apparatus for forming a predetermined thin film on a substrate to be processed by magnetron sputtering, and to the magnetron sputtering apparatus. [Background technology]

[0002] A magnetron sputtering apparatus has a cathode unit, which generally has a magnet unit on the lower side facing away from the sputtering surface of a target placed in a position facing the inside of a vacuum chamber containing a substrate to be processed. When a rare gas such as argon gas is introduced into the vacuum chamber and a negative DC or AC voltage is applied to the target to sputter the sputtering surface of the target, 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 the electrons and rare gas molecules, thereby increasing the plasma density.

[0003] 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 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 linear segments on both sides of the central magnet and bridging segments connecting the free ends of the linear segments, 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 and the Y-axis perpendicular to the X-axis is the Y-axis, 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. This generates a racetrack-shaped plasma in the space between the sputtering surface and the substrate (the space above the sputtering surface).

[0004] 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 magnet. It is known that electrons in the plasma retain some inertial motion when they are bent and reoriented by the electromagnetic field. In such cases, the plasma tends to spread (in the Y-axis direction) in the corner regions of the target located diagonally opposite the magnet, where inertial motion remains, resulting in a problem of greater erosion compared to other corner regions where inertial motion does not remain. Therefore, if electrons in the plasma are forced to move in a constant clockwise or counterclockwise circular orbit along the racetrack, the sputtering surface of the target will be worn unevenly, resulting in poor target utilization efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-127601 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, an object of the present invention is to provide a cathode unit for a magnetron sputtering apparatus and a magnetron sputtering apparatus that can make the erosion area of the target more uniform as sputtering progresses, thereby increasing the utilization efficiency of the target. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a cathode unit for a magnetron sputtering apparatus, which comprises a magnet unit provided below and facing away from the sputtering surface of a target placed in a position facing the inside of a vacuum chamber, the magnet unit having a central magnet arranged linearly and peripheral magnets surrounding the central magnet with their upper polarities reversed, and a leakage magnetic field acting on the 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, the cathode unit being characterized in that 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.

[0008] According to the present invention, the electron direction in the plasma can be freely reversed, and the direction of the remaining electron inertial motion can be reversed around the X-axis. For example, the electrons in the plasma can initially move in a clockwise orbit. When the target corners, where the electrons' inertial motion remains, are extensively eroded, the electrons in the plasma are reversed to move in a counterclockwise orbit. This allows for extensive erosion of the other diagonally opposite corners of the target. As a result, compared to the conventional example, uneven wear of the target is suppressed, and the target erosion area as sputtering progresses is more uniform. This is even more effective if the magnet unit is reciprocated along the Y-axis with a predetermined stroke length. The electron direction 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.

[0009] In the present invention, if a first magnet unit applies the leakage magnetic field to the space above the sputtering surface, a second magnet unit is configured by replacing the magnetism of the central and peripheral magnets of the first magnet unit with that of the upper magnets of the first magnet unit, and a swapping device is provided to swap the leakage magnetic field acting on the space above the sputtering surface between the first magnet unit and the second magnet unit, thereby freely reversing the direction of electrons in the plasma, the direction of electrons moving in a clockwise or counterclockwise orbit along a racetrack can be periodically reversed. In this case, the swapping device may be configured by arranging the first magnet unit and the second magnet unit side by side on the same plane and providing a drive unit that moves the first magnet unit and the second magnet unit together in one direction on the same plane, or by providing the first magnet unit and the second magnet unit 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 adopt 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.

[0010] In order to solve the above problems, the magnetron sputtering apparatus of the present invention comprises a cathode unit for the magnetron sputtering apparatus, a vacuum chamber in which the target of the cathode unit is installed in an orientation facing the interior of the vacuum chamber and a substrate to be processed is placed opposite the vacuum chamber in the space in front of the sputtering surface, a sputtering power supply that supplies power to the target, and gas introduction means that enables the introduction of sputtering gas into the vacuum chamber in a vacuum atmosphere, and is characterized in that the magnetron sputtering apparatus is configured to reverse the direction of electrons in the plasma depending on the integrated power supplied to the target. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view of a magnetron sputtering apparatus including a cathode unit according to a first embodiment. [Figure 2] FIG. 2 is a plan view showing a main part of the cathode unit shown in FIG. [Figure 3]FIG. 3 is an enlarged plan view of a portion of the cathode unit shown in FIG. 2. [Figure 4] FIG. 10 is a schematic cross-sectional view of a magnetron sputtering apparatus including a cathode unit according to a second embodiment. [Figure 5] (a) to (d) are diagrams explaining the procedure for reversing the direction of electrons in plasma. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, 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 will be described using as an example a so-called multi-target magnetron sputtering apparatus in which a 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 each having a rectangular outline 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 posture of the magnetron sputtering apparatus SM, and the vertical direction from the sputtering surface of the target toward the substrate Sw is defined as the Z-axis direction, the longitudinal direction of a central magnet described below is defined as the X-axis direction, and the Y-axis direction is perpendicular to the X-axis direction.

[0013] 1 and 2, the magnetron sputtering apparatus SM of this embodiment includes a vacuum chamber 1 that defines a film formation chamber 11. An exhaust port 12 is formed in the wall of the vacuum chamber 1, and an exhaust pipe 13 is connected to the exhaust port 12 from a vacuum exhaust unit Pu that is configured with a rotary pump, a dry pump, a turbo molecular pump, or the like, and the film formation chamber 11 is evacuated to a predetermined pressure (for example, 1×10 -5 The vacuum chamber 1 can be maintained at a pressure of 1000 Pa. Gas supply ports 21 a and 21 b are also formed 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 installed therein, are connected to the gas supply ports 21 a and 21 b, respectively, so that a rare gas such as argon gas, whose flow rate is controlled, and a reactive gas such as oxygen gas, if necessary, can be introduced into the film formation chamber 11, and these constitute the gas introduction means of this embodiment.

[0014] 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 41-44 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 51-55 that are at least one more than the number of the targets 41-44 (five in this embodiment), and are respectively arranged in the space below the targets 41-44 (outside the vacuum chamber). The targets 41-44 are manufactured according to the composition of the film to be deposited on the underside of the substrate Sw. Each of the targets 41-44 has 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 41-44 are set so that, when placed directly facing the substrate Sw, the outline of each of the aligned targets 41-44 is slightly larger than the substrate Sw. A copper backing plate 42 is bonded to the underside of each target 41-44 via a bonding material (not shown) such as indium, and the targets are installed in the vacuum chamber 1 in an electrically insulated and coolable state. Adjacent targets 41, 42 and 43, 44 are paired, respectively, and an output 61 from an AC power supply 6 serving as a sputtering power source is connected to each of the pairs of targets 41-44. The AC power supply 6 can apply AC power of a predetermined frequency (e.g., 1 kHz to 100 kHz) between the pairs of targets 41, 42 and 43, 44. Depending on the target species, for example, DC power having a negative potential can be applied to each of the targets 41 to 44.

[0015] Each magnet unit 51-55 has the same shape and is provided parallel to the backing plate 42. It 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. The central magnet 52 has straight sections 53a and 53b extending parallel to each other at equal intervals on both sides of the central magnet 52, and bridging sections 53c connecting the free ends of the straight sections 53a and 53b. The magnets have opposite polarities toward the target (e.g., the central magnet 52 has a south pole and the peripheral magnet 53 has a north pole). The central magnet 52 and the 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. The central magnet 52 and the peripheral magnets 53 are designed to 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 41-44 and the underside of the substrate Sw, with a line passing through the position where the vertical component of the magnetic field becomes zero extending in the Y-axis direction and closing like a racetrack. Furthermore, a nut member 54 protrudes from the underside of the support plate 51 of each magnet unit 51-55, and a feed screw Fs connected to a motor Mt is threadedly engaged with each nut member 54. During sputtering, each magnet unit 51-55 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 51-55 may also be reciprocated in the X-axis direction with a predetermined stroke length.

[0016] When forming a film 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 41-44, 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 (and 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 41-44 with the AC power source 6. This generates a racetrack-shaped plasma Pm above the sputtering surface 41 of each target 41-44. 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.

[0017] 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 51-55 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 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 this case, in the corner regions of the diagonally opposite targets 41-44 (the upper left regions in FIG. 3 ), where inertial motion remains, 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 41-44, which reduces the utilization efficiency of the targets 41-44.

[0018] In this embodiment, as described above, the number of magnet units 51-55 is one more than the number of targets 41-44, and the polarities of the central magnet 52 and peripheral magnet 53 of the magnet units 51-55 on the target 41-44 side are different between adjacent magnet units 51-55 (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 52-55 below each target 41-44, 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 51-55 may also reciprocate in the X-axis direction by a predetermined stroke length, with the leakage magnetic field Mf from one magnet unit 51 not acting on the sputtering surface 41 of the target 41. Then, for example, when the integrated power to the targets 41-44 measured by the AC power supply 6 reaches a predetermined value, the magnet units 51-54 are positioned below the targets 41-44 by the driving means Mt, Fs, respectively, 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 41-44 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.

[0019] 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. 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, the electrons erode over a wide area in the corner regions of each diagonally positioned target 41-44 (the upper left region in FIG. 3 ), where their inertial motion remains. Then, the direction of the electrons in the plasma is reversed so that they move in a counterclockwise orbit, allowing the electrons to erode over a wide area in the corner regions of the other diagonally positioned targets 41-44 (the upper right region in FIG. 3 ). As a result, compared to the conventional example, uneven wear of the targets 41 to 44 is suppressed, and as sputtering progresses, the erosion areas of the targets 41 to 44 can be made more uniform. Note that the direction of electrons in the plasma Pm can be reversed as appropriate, for example, every time film formation on one or a predetermined number of substrates Sw is completed, or when the integrated power to each target 41 to 44 reaches a predetermined value.

[0020] 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.

[0021] As shown in FIGS. 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 501-504, each of which 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 of the magnets being reversed on the front and back sides of the support 500. A rotating shaft 501 extending in the X-axis direction is coupled to the support 500, and the rotating shaft 501 is connected to a motor 502. The rotating shaft 501 and motor 502 constitute the rotating unit of this embodiment. Although not shown in detail, the magnet units 501-504 are provided with a driving means for moving the magnet units 501-504 up and down in the Z-axis direction so that the magnet units 501-504 can be turned upside down to avoid interference with other components. Then, when the support 500 is rotated by the rotation units 501, 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.

[0022] In the above embodiment, the central magnet 52 and peripheral magnets 53 constituting each of the magnet units 51-55 are described as being permanent magnets such as neodymium magnets. However, this 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 reverse the polarity of the central magnet 52 and peripheral magnet 53 of each of the magnet units 51-55 on the target 41-44 side, 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, this 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. [Explanation of symbols]

[0023] Cu1, Cu2...cathode unit, SM...magnetron sputtering apparatus, 1...vacuum chamber, 41-44...target, 41...sputtering surface, 51-55, 501-504...magnet units, Mf...leakage magnetic field, 52...central magnet, 53...peripheral magnet, Pm...plasma, 55...first magnet unit (component of swap means), 51...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

1. 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.

2. 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.

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