Direct current sputtering device

Abstract

Provided is a technique capable of reducing metal contamination while performing direct-current sputtering using a gallium target. A direct-current sputtering device has: a substrate holding portion that holds a substrate; a target container that holds a gallium target containing gallium in a manner facing a main surface of the substrate in a first direction; a direct-current power source that applies direct-current electric power to the gallium target; and a conductor that is connected at one end to a negative side of the direct-current power source and at the other end to the gallium target inside the target container and is formed of a gallium corrosion-resistant metal. Further, the direct-current sputtering device has: a sputtering gas supply portion that has a gas supply port that supplies a sputtering gas between the target container and the substrate holding portion; and a magnet portion that is located on the side opposite the substrate holding portion with respect to the target container and has a ring-shaped high-density plasma region in which the density of plasmaized sputtering gas is higher than the surrounding on a surface on one side of the gallium target in the first direction.

Description

Technical Field

[0001] The subject matter disclosed in this specification relates to a DC sputtering apparatus. Background Technology

[0002] Gallium nitride (GaN) used in power devices or LEDs (light-emitting diodes) is sometimes deposited using vacuum deposition methods, such as MOCVD (metal-organic chemical vapor deposition). However, GaN deposition using MOCVD has a high environmental impact due to the use of flammable or toxic gases such as triethylgallium (TEG) and ammonia (NH3). Furthermore, sometimes more than 90% of these gases are emitted, resulting in low gas utilization efficiency. In contrast, sputtering, a vacuum deposition method, involves bombarding a solid sputtering target with cations and using the sputtered particles to form a film. Sputtering typically uses non-flammable and inexpensive gases such as argon (Ar) and nitrogen (N2), and the target material can be a metal or solid compound, resulting in lower deposition costs and a lower environmental impact.

[0003] Gallium nitride (GaN) sintered targets or metallic gallium can be used as sputtering targets. GaN sintered targets, due to their insulating properties, require sputtering with high-frequency RF power supplies, resulting in low film deposition rates and low productivity. On the other hand, when metallic gallium is used as the sputtering target, its conductivity allows for direct current (DC) sputtering, thereby improving productivity. Therefore, from a productivity standpoint, metallic gallium is more preferable as the sputtering target than GaN sintered targets.

[0004] Since gallium has a melting point of 29.76°C, it melts due to the heat generated during sputtering. Therefore, a target container capable of storing liquid gallium is needed. Patent Document 1 discloses the use of a conductive container such as copper (Cu). Because a conductive container is used, if the target container is energized, the metallic gallium is also energized, thus enabling sputtering.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2015-229782 Summary of the Invention The problem the invention aims to solve However, liquid gallium is highly corrosive to other metals. Therefore, as described in Patent Document 1, when using a metal container, the container itself may become embrittled, or the container material may melt into the gallium. When other metals melt into the gallium target, they become impurities and are doped into the gallium film, which may lead to film degradation and consequently, device performance degradation.

[0006] The purpose of this invention is to provide a technique for DC sputtering using gallium targets while reducing metal contamination.

[0007] means for solving problems To address the aforementioned issues, a first embodiment is a DC sputtering apparatus comprising: a substrate holding section for holding a substrate; a target container for holding a gallium target facing the main surface of the substrate in a first direction; a DC power supply for applying DC power to the gallium target; a conductor, one end of which is connected to the negative terminal of the DC power supply and the other end of which is in contact with the gallium target within the target container, wherein the conductor is formed of a gallium-resistant metal; a sputtering gas supply section having a gas supply port for supplying sputtering gas between the target container and the substrate holding section; and a magnet section located on the side opposite to the substrate holding section relative to the target container, wherein a ring-shaped high-density plasma region is formed on one side of the gallium target in the first direction, wherein the density of the plasma-plasmized sputtering gas is higher than that of the surrounding area.

[0008] The second form is that, in the DC sputtering apparatus of the first form, the conductor contains molybdenum, copper, or stainless steel as the main component.

[0009] The third form is that, in the DC sputtering apparatus of the first or second form, the target container is formed of ceramic material.

[0010] The fourth form is that, in the DC sputtering apparatus of the third form, the target container is formed of a ceramic material with gallium nitride, aluminum nitride, or boron nitride as the main components.

[0011] The fifth configuration is, in any of the first to fourth configurations of the DC sputtering apparatus, wherein the conductor is arranged in a second direction intersecting the first direction in a manner that separates it from the high-density plasma region.

[0012] The sixth embodiment is a DC sputtering apparatus in any of the first to fifth embodiments, wherein the magnet portion includes a ring-shaped first permanent magnet, and the conductor is arranged in a second direction intersecting the first direction in a manner separate from the first permanent magnet.

[0013] The seventh embodiment is a DC sputtering apparatus in any one of the first to sixth embodiments, wherein the target container has: a container body portion that houses the gallium target; and a passage portion that communicates with the container body portion and is formed as a concave shape extending in a second direction intersecting the first direction; the other end of the conductor is disposed in the passage portion.

[0014] The eighth embodiment is that, in the DC sputtering apparatus of the seventh embodiment, the target container further comprises: a cover portion that covers the opening of the passage portion on one side in the first direction; the other end of the conductor is disposed in the portion of the passage portion covered by the cover portion.

[0015] The ninth configuration is a DC sputtering apparatus in any of the first to eighth configurations in which the sputtering gas contains argon.

[0016] The tenth embodiment is that, in any one of the first to ninth embodiments of the DC sputtering apparatus, a reactive gas supply unit is further provided, which supplies reactive gas in such a way that the gallium deposited on the main surface of the substrate reacts with the plasma-plated reactive gas.

[0017] The eleventh form is that, in the DC sputtering apparatus of the tenth form, the reactive gas contains nitrogen.

[0018] The twelfth embodiment is a DC sputtering apparatus in any of the first to eleventh embodiments, wherein the target container has a bottom surface and a side surface that hold the gallium target inside, and the conductor passes through the target container in the bottom surface or the side surface.

[0019] The effects of the invention According to the DC sputtering apparatuses of the first to twelfth embodiments, DC power can be applied directly to the gallium target via a conductor formed of a gallium-corrosion-resistant metal without passing through a target container. Therefore, DC sputtering using gallium targets can be performed while reducing metal contamination.

[0020] According to the third type of DC sputtering apparatus, since the target container is formed by ceramic material, metal contamination generated by the target container can be reduced.

[0021] According to the fifth form of the DC sputtering device, since the sputtering of the conductor can be reduced, the metal contamination generated by the conductor can be reduced.

[0022] According to the DC sputtering device of the sixth form, since the sputtering of the conductor can be reduced, the metal contamination generated by the conductor can be reduced.

[0023] According to the seventh type of DC sputtering device, since the conductor can be removed from the high-density plasma region, the sputtering of the conductor can be reduced.

[0024] According to the DC sputtering device of the eighth form, since the conductor can be avoided from being exposed to high-density plasma, the sputtering of the conductor can be reduced. Attached Figure Description

[0025] Figure 1 This is a side view that schematically illustrates an example of the structure of the DC sputtering apparatus of the first embodiment.

[0026] Figure 2 It is shown in a general way. Figure 1 The diagram shows a top view of an example of the structure of a DC sputtering apparatus.

[0027] Figure 3 It is shown in a general way. Figure 1 A perspective view of an example of the structure of the substrate holding part and the heater shown.

[0028] Figure 4 It is shown Figure 1 A schematic cross-sectional view of the target container for the sputtering section is shown.

[0029] Figure 5 Viewed from the vertical top Figure 1 A top view of the target container for the sputtering section.

[0030] Figure 6 It is shown Figure 1 The diagram shows the hardware structure of the control unit.

[0031] Figure 7 This is a flowchart illustrating an example of the operation of a DC sputtering apparatus.

[0032] Figure 8 This is a flowchart illustrating the process performed on a substrate by the operation of a DC sputtering apparatus.

[0033] Figure 9 This is a schematic cross-sectional view showing the target container of the second embodiment.

[0034] Figure 10 This is a top view of the target container of the second embodiment as viewed from the vertical top.

[0035] Figure 11 This is a diagram showing the target container of the third embodiment. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the structural elements described in these embodiments are merely illustrative and are not intended to limit the scope of the present invention to these structural elements. In the accompanying drawings, for ease of understanding, the dimensions or quantities of various parts are sometimes exaggerated or simplified as needed.

[0037] <1. First Implementation Method> Figure 1 This is a side view that schematically shows an example of the structure of the DC sputtering apparatus 100 of the first embodiment. Figure 2 It is shown in a general way. Figure 1 A top view of an example of the structure of the DC sputtering apparatus 100 shown. Figure 1 It is shown in a general way along Figure 2 A cross-sectional view of the DC sputtering device 100 cut by the curved AA line shown.

[0038] The DC sputtering apparatus 100 is a film deposition apparatus for performing reactive sputtering-based film deposition on a substrate W. Specifically, the DC sputtering apparatus 100 forms a thin film containing a first element and a second element on the main surface Wa of the substrate W. The first element is specifically gallium (Ga). The second element is, for example, oxygen (O) or nitrogen (N). When the first element is gallium and the second element is nitrogen, the DC sputtering apparatus 100 forms a gallium nitride film on the main surface Wa of the substrate W. The substrate W is, for example, a substrate made of sapphire, silicon (Si), or silicon carbide (SiC). The substrate W may have, for example, a circular plate shape. Furthermore, the material and shape of the substrate W are not limited thereto and may be appropriately modified.

[0039] The DC sputtering apparatus 100 includes: a chamber 1, a sputtering unit 2, a plasma unit 3, a substrate holding unit 4, a suction mechanism 5, and a control unit 6. The chamber 1 has a box-shaped, hollow structure. The internal space of the chamber 1 corresponds to the processing space for film deposition on the substrate W. The chamber 1 is a vacuum chamber, a container capable of being sealed in a vacuum state. A transfer-in / extraction mechanism (not shown) is provided in the chamber 1. This mechanism can switch the internal state of the chamber 1—that is, the state of the internal space—between a connected state connected to the external space and a sealed state isolated from the external space. In the connected state, the substrate transport unit (not shown) transports the untreated substrate W into the chamber 1. The DC sputtering apparatus 100 performs film deposition on the substrate W in the sealed state. Then, the transfer-in / extraction mechanism connects the chamber 1 to the outside, and the substrate transport unit, in this connected state, removes the film-deposited substrate W from the chamber 1.

[0040] The suction mechanism 5 has a suction port 5a. The suction port 5a is an opening in the processing space. The suction mechanism 5 is controlled by the control unit 6. The suction mechanism 5 reduces the pressure inside the chamber 1 by drawing gas from the suction port 5a and adjusts the pressure to a specified decompression range. For example, a vacuum pump can be used as the suction mechanism 5; more specifically, a turbomolecular pump can be used.

[0041] The processing space within chamber 1 includes a sputtering space 1a and a plasma space 1b. The sputtering space 1a and plasma space 1b are arranged circumferentially along a predetermined orbital axis Q1. The orbital axis Q1 is an axis along the vertical direction. Furthermore, physical structures (e.g., partitions) may be provided within chamber 1 to separate the sputtering space 1a and the plasma space 1b.

[0042] A gallium target 21 is disposed in sputtering space 1a. The gallium target 21 is sputtered in sputtering space 1a. The gallium target 21 contains gallium as a first element. A reactive gas is supplied to plasma space 1b via plasma section 3. The reactive gas contains a second element (e.g., nitrogen). Plasma section 3 plasma-entrains the reactive gas.

[0043] The substrate holding part 4 is disposed in the chamber 1. While holding the substrate W, the substrate holding part 4 causes the substrate W to revolve around the revolution axis Q1, and alternately moves the substrate W to the sputtering space 1a and the plasma space 1b.

[0044] Figure 3 It is shown in a general way. Figure 1 A perspective view of an example of the structure of the substrate holding part 4 and the heater 11 shown. Figure 3 In this example, the substrate holding part 4 holds multiple substrates W (six in this example) circumferentially arranged along the axis of revolution Q1. Furthermore, the substrate holding part 4 does not need to hold multiple substrates W simultaneously. The substrate holding part 4 can also be configured to hold only a single substrate W. The substrate holding part 4 holds the substrate W in a horizontal position. A horizontal position means that the thickness direction of the substrate W (the normal direction of its main surface Wa) is along the vertical direction. When multiple substrates W are held by the substrate holding part 4, the main surface Wa of each substrate W (in...) Figure 3 The lower surface (middle part) is exposed within chamber 1 (see reference). Figure 1 ).

[0045] The substrate holding section 4 causes the substrate W to revolve around the revolution axis Q1, thereby allowing each substrate W to alternately pass through the sputtering space 1a and the plasma space 1b. In other words, the substrate holding section 4 moves the substrate W by having the substrate W alternately pass through the sputtering space 1a and the plasma space 1b. When the substrate W passes through the sputtering space 1a, gallium particles from the gallium target 21 are deposited on the main surface Wa of the substrate W. When the substrate W passes through the plasma space 1b, active species of the second element (including at least one of ions and free radicals) generated by the plasmaification of the reactive gas react with the gallium atoms on the main surface Wa of the substrate W. As a result, a predetermined thin film containing gallium and the second element is formed on the main surface Wa of the substrate W.

[0046] Hereinafter, the direction in which the revolution axis Q1 extends is sometimes referred to as the "axial direction," the direction of rotation centered on the revolution axis Q1 is called the "circumferential direction," and the direction in which a straight line orthogonal to the axial direction extends is called the "radial direction." The axial direction is an example of the "first direction." The radial direction is an example of the "second direction."

[0047] <Substrate Holding Section> The substrate holding portion 4 includes a holding device 41 and a rotation drive portion 42. The holding device 41 holds a plurality of substrates W arranged at intervals in the circumferential direction. The holding device 41 has, for example, a circular plate shape centered on a revolution axis Q1. A plurality of through holes 41a may also be formed on the holding device 41. The plurality of through holes 41a are formed at equal intervals in the circumferential direction, for example, and penetrate the holding device 41 in the axial direction. Each through hole 41a has a stepped shape that narrows as it moves toward the vertically downward side. Then, substrates W are arranged one by one in each through hole 41a. The holding device 41 supports the periphery of each substrate W at the stepped portion of each through hole 41a.

[0048] The rotation drive unit 42 is controlled by the control unit 6. The rotation drive unit 42 causes the holding device 41 to rotate about the revolution axis Q1. As a result, the plurality of substrates W held by the holding device 41 revolve around the revolution axis Q1. The rotation drive unit 42 has, for example, a motor and a shaft. The motor is connected to the holding device 41 via the shaft. The upper end of the shaft is connected to the lower surface of the holding device 41 and extends along the revolution axis Q1. The motor causes the shaft to rotate about the revolution axis Q1, thereby enabling the holding device 41 to rotate about the revolution axis Q1.

[0049] Heater 11 heats a plurality of substrates W held by substrate holding portion 4. Heater 11 adjusts the temperature of substrate W to a temperature range suitable for film formation processing. Heater 11 is controlled by control portion 6. Heater 11 is located within chamber 1 at a position separated from substrate holding portion 4 toward the vertically upward side. Heater 11 has, for example, an annular shape centered on a revolution axis Q1. As heater 11, for example, a resistance heater including heating wires or an optical heater including a light source (e.g., infrared light) for irradiating and heating substrate W can be used.

[0050] The sputtering unit 2 includes a gallium target 21, a sputtering gas supply unit 23, and a first plasma generation unit 25. Furthermore, in Figure 2 The sputtering gas supply unit 23 and the first plasma generation unit 25 are omitted from the illustration.

[0051] A gallium target 21 is disposed within the sputtering space 1a and faces the substrate holding portion 4 in the axial direction (first direction). More specifically, the gallium target 21 is positioned axially facing a portion of the circumferential direction of the substrate W's movement path R1. Figure 1 In the example shown, the gallium target 21 is located on the vertically lower side relative to the substrate holding portion 4.

[0052] Gallium target 21, for example, has a plate-like shape, in Figure 2 In the example shown, it has a circular shape when viewed from above. Here, "viewing from above" refers to observation with the line of sight along the axial direction. The gallium target 21 has a main surface 21a facing vertically upwards. The gallium target 21 is held by a target container 22. The target container 22 holds the gallium target 21 with its main surface 21a facing the substrate holding portion 4. The main surface 21a of the target 21 is the surface on one side of the target 21 along its axial direction (first direction). When the gallium target 21 is held by the target container 22, its main surface 21a is exposed within the chamber 1.

[0053] Sputtering Gas Supply Department The sputtering gas supply unit 23 supplies sputtering gas to the sputtering space 1a. The sputtering gas is an inert gas, such as a rare gas. As a rare gas, at least one of argon and xenon can be used. Figure 1In the example shown, the sputtering gas supply unit 23 has multiple (two in this example) gas supply pipes 231, a valve 232, a flow adjustment unit 233, and a common pipe 234. The upstream end of each gas supply pipe 231 is connected to the downstream end of one common pipe 234. The upstream end of the common pipe 234 is connected to a sputtering gas supply source 235. The sputtering gas supply source 235 supplies sputtering gas to the upstream end of the common pipe 234. The gas supply pipe 231 has a first gas supply port 23a that opens into the sputtering space 1a. The sputtering gas flows within the common pipe 234 and each gas supply pipe 231, and flows out from the first gas supply port 23a into the sputtering space 1a. A portion of the sputtering gas flows into the space between the action path R1 of the substrate W and the gallium target 21.

[0054] Valve 232 is provided in common pipe 234 and opens and closes common pipe 234. Flow regulating unit 233 is provided in common pipe 234 and regulates the flow rate of the sputtering gas flowing in common pipe 234. Flow regulating unit 233 is, for example, a mass flow controller. Valve 232 and flow regulating unit 233 are controlled by control unit 6.

[0055] <First Plasma Generation Unit> The first plasma generating unit 25 plasmaizes the sputtering gas within the sputtering space 1a, and causes ions (e.g., argon ions) in the plasma to collide with the main surface 21a of the gallium target 21. Through this collision, sputtered particles (here, gallium particles) are ejected from the main surface 21a of the gallium target 21. The sputtered particles move vertically upward toward the substrate holding unit 4.

[0056] exist Figure 1 In the example shown, the first plasma generation unit 25 has a DC power supply, namely a first power supply 251. The first power supply 251 is controlled by the control unit 6. The first power supply 251 supplies DC power for sputtering to the gallium target 21. The first power supply 251 outputs a DC voltage, for example, between the gallium target 21 and the chamber 1. More specifically, the first power supply 251, for example, has a switching power supply circuit (not shown) that applies DC power to the gallium target 21 by applying a negative potential. Figure 1 As shown, chamber 1 can also be grounded. In addition, substrate holding part 4 can also be electrically connected to chamber 1.

[0057] When the first power source 251 supplies DC power to the gallium target 21, an electric field for plasma generation is generated around the gallium target 21. This electric field then acts on the sputtering gas, ionizing and plasmaizing it. Ions in the plasma (e.g., argon ions) collide with the main surface 21a of the gallium target 21, sputtering the gallium target 21. That is, gallium particles fly out of the gallium target 21 and move towards the operating path R1 of the substrate W. When the gallium particles reach the main surface Wa of the substrate W in the sputtering space 1a, they are deposited on the main surface Wa. Thus, a gallium film (hereinafter referred to as "gallium film") is formed on the main surface Wa of the substrate W.

[0058] <Chimney> exist Figure 1 In the example shown, the sputtering section 2 has a confinement shield 27. The confinement shield 27 is disposed within the sputtering space 1a. The confinement shield 27 has a box-shaped hollow shape and surrounds the gallium target 21. The upper plate portion 271 in the confinement shield 27 has an opening 27a facing the gallium target 21 in the axial direction. The opening 27a extends through the upper plate portion 271 in the axial direction. Gallium particles ejected from the main surface 21a of the gallium target 21 move toward the substrate holding portion 4 through the opening 27a.

[0059] Figure 4 It is shown Figure 1 A schematic cross-sectional view of the target container 22 of the sputtering section 2 shown. Figure 5 Viewed from the vertical top Figure 1 A top view of the target container 22 of the sputtering section 2 shown. Figure 4 As shown, the target container 22 has a shallow, bottomed cylindrical shape. In other words, the target container 22 has a bottom surface for holding the gallium target 21 and an annular side surface that extends vertically upward from the periphery of the bottom surface. Since gallium has a melting point of 29.76°C, the gallium target 21 may melt due to heat during the sputtering process, or even at room temperature, a portion of it may liquefy. Therefore, the target container 22 has a shape that allows it to store liquid gallium target 21 on its inner side.

[0060] The target container 22 is preferably formed of a ceramic material. Specifically, the target container 22 can be formed of a ceramic material whose main components are gallium nitride, aluminum nitride, or boron nitride. As long as it is a III-V group aluminum or borate nitride, the impact on the gallium nitride film device can be reduced compared to using other metal nitrides.

[0061] When a conductive container is used as the target container 22, the container itself may become embrittled and the container material may melt into the gallium target 21 due to the high corrosiveness of liquid gallium to other metals. When other metals melt into the gallium target 21, they are doped into the gallium film as impurities, which may lead to deterioration of the film quality and device performance. Although the possibility of melting can be reduced by using metals such as molybdenum, which are resistant to gallium corrosion, they are rare, expensive, and have high hardness, resulting in poor machinability.

[0062] When molybdenum is used to fabricate the target container 22, as the gallium target 21 inside the container decreases due to continuous film deposition, the liquid gallium sloshes and exposes the bottom of the container, causing molybdenum from the container material to be sputtered, potentially contaminating the gallium film. Furthermore, since the same potential as the gallium target 21 is applied to the molybdenum, it is possible for molybdenum to be doped into the gallium film due to sputtering caused by argon ions.

[0063] The sputtering section 2 has a magnet section 28. The magnet section 28 is located on the opposite side of the substrate holding section 4 relative to the target container 22. The magnet section 28 has a ring-shaped (here, circular ring-shaped) first permanent magnet 281 and a second permanent magnet 282 disposed radially inside the first permanent magnet 281. The positive pole of the first permanent magnet 281 faces vertically upward, and the positive pole of the second permanent magnet 282 faces vertically downward. The magnet section 28 forms magnetic field lines on the main surface 21a of the gallium target 21, extending from the first permanent magnet 281 toward the second permanent magnet 282. Electrons in the plasma generated by the first plasma generation section 25 are retained near the main surface 21a of the gallium target 21 by passing through the magnetic field lines and are accelerated (EB drift). The high-energy electrons due to drift collide with the sputtering gas, i.e., argon, producing electrons and argon ions. As a result, a ring-shaped high-density plasma region PA1 with a high concentration of argon plasma is formed on the main surface 21a of the gallium target 21.

[0064] Furthermore, the first permanent magnet 281 does not need to be formed in a circular shape; it can be formed in a shape different from a circular shape. That is, the first permanent magnet 281 only needs to be shaped to form a closed ring-shaped high-density plasma region. For example, the first permanent magnet 281 can be formed in a racetrack shape (elliptical, or a rounded rectangular shape composed of two parallel lines of equal length (straight sections) and two semicircles (corner sections)).

[0065] A cooling container 29 is disposed on the vertically lower side of the target container 22. The cooling container 29 cools the gallium target 21 by cooling the target container 22. Cooling water 291 is stored in the cooling container 29. A first permanent magnet 281 and a second permanent magnet 282 are disposed within the cooling container 29. The cooling water 291 within the cooling container 29 can be replaced by a pump (not shown).

[0066] like Figure 4 As shown, the first plasma generating unit 25 has a conductor 253. The conductor 253 has a metal wire. One end of the conductor 253 is connected to the negative side of the DC power supply, i.e., the first power supply 251, and the other end of the conductor 253 is connected to the gallium target 21. That is, the other end of the conductor 253 is immersed in the liquefied gallium of the gallium target 21.

[0067] The metallic wire of conductor 253 is formed of a gallium-resistant metal. Molybdenum, copper, or stainless steel can be used as the gallium-resistant metal. Alternatively, titanium or nickel alloys can also be used. By using a gallium-resistant metal, corrosion of the conductor 253 by the gallium target 21 can be avoided. Furthermore, conductor 253 is preferably coated with an insulating material such as resin. This reduces the likelihood of sputtering of conductor 253.

[0068] like Figure 4 As shown, the other end of conductor 253 is radially positioned outside the annular high-density plasma region PA1. The high-density plasma region PA1 is a region where cations of the sputtering gas (argon) exist at a high density. Therefore, by positioning conductor 253 outside the high-density plasma region PA1, sputtering of conductor 253 can be reduced. Consequently, metal contamination of the gallium film by conductor 253 can be reduced.

[0069] like Figure 5 As shown, the other end of the conductor 253 is radially positioned outside the outer periphery of the annular first permanent magnet 281. Magnetic lines of force are generated from the first permanent magnet 281 toward the inner side of the second permanent magnet 282. Therefore, positioning the conductor 253 outside the first permanent magnet 281 further reduces the likelihood of the conductor 253 being sputtered.

[0070] Plasma Department return Figure 1 The plasma unit 3 has a second gas supply port 31a that opens into the plasma space 1b. The plasma unit 3 supplies reactive gas to the plasma space 1b through the second gas supply port 31a. Furthermore, the plasma unit 3 plasmaizes the reactive gas within the plasma space 1b. Specifically, the plasma unit 3 has a reactive gas supply unit 31 and a second plasma generation unit 33.

[0071] <Reactive Gas Supply Department> exist Figure 1In the example shown, the reactive gas supply unit 31 has multiple (two in this example) gas supply pipes 311, valves 312, flow adjustment units 313, and a common pipe 314. The upstream end of each gas supply pipe 311 is connected to the downstream end of one common pipe 314. The upstream end of the common pipe 314 is connected to a reactive gas supply source 315. The reactive gas supply source 315 supplies reactive gas to the upstream end of the common pipe 314. Each gas supply pipe 311 has a second gas supply port 31a. Figure 1 In the example shown, the opening direction of the second air supply port 31a in the air supply pipe 311 is parallel to the axial direction and faces the substrate holding portion 4. Figure 1 In the example shown, the downstream end of each gas supply pipe 311 corresponds to the second gas supply port 31a. Figure 1 In the example shown, the two second air inlets 31a are configured to be radially spaced apart.

[0072] As the reactive gas, a gas containing a second element in the thin film formed on the main surface Wa of the substrate W can be used. The second element is, for example, nitrogen. As a specific example, the reactive gas includes at least one of nitrogen (N2) and ammonia (NH3). For example, when the reactive gas is nitrogen, a gallium nitride film is formed on the main surface Wa of the substrate W. Alternatively, the reactive gas can be oxygen (O2). When the reactive gas is oxygen, a gallium oxide film can be formed on the main surface Wa of the substrate W. Furthermore, the following description primarily focuses on the case where nitrogen is used as the reactive gas.

[0073] Valve 312 is provided in common pipe 314 to open and close common pipe 314. Flow adjustment unit 313 is provided in common pipe 314 to adjust the flow rate of the reactive gas flowing in common pipe 314. Flow adjustment unit 313 is, for example, a mass flow controller. Valve 312 and flow adjustment unit 313 are controlled by control unit 6.

[0074] <Second Plasma Generation Unit> The second plasma generating unit 33 plasma-generates the nitrogen gas supplied from the second gas supply port 31a into the chamber 1. The highly reactive nitrogen species generated by plasma-generating moves toward the substrate holding unit 4, and when it reaches the main surface Wa of the substrate W moving in the plasma space 1b, it nitrids the gallium film on the main surface Wa.

[0075] exist Figure 1 In the example shown, the second plasma generating unit 33 includes an inductively coupled antenna 331 and a second power supply 332. The inductively coupled antenna 331 is located in the plasma space 1b on the vertically lower side of the operating path R1 of the substrate W, which is separated from the operating path R1 of the substrate W. The inductively coupled antenna 331 has a generally U-shaped conductive member 3311 that convexes towards the vertically upper side.

[0076] The conductive member 3311 is disposed within the chamber 1 with its two ends positioned vertically downwards. The conductive member 3311 is mounted at the bottom of the chamber 1. Figure 2 In the example shown, the conductive member 3311 is arranged with its two ends aligned circumferentially. The two ends of the conductive member 3311 extend, for example, through the bottom of the chamber 1, and are electrically connected to the second power supply 332. The conductive member 3311 functions as an electrode (antenna) for plasma generation.

[0077] exist Figure 1 and Figure 2 In the example shown, multiple (two in this case) inductively coupled antennas 331 are provided, and each inductively coupled antenna 331 is located near each second air supply port 31a. Figure 1 and Figure 2 In the example shown, the inductively coupled antenna 331 is configured to face the second air supply port 31a of the air supply pipe 311 in the axial direction. In other words, the second air supply port 31a is located radially between the two ends of the inductively coupled antenna 331 (conductive member 3311).

[0078] The second power supply 332 supplies high-frequency power to the inductively coupled antenna 331. The second power supply 332, for example, includes a converter circuit and a matching circuit, and is controlled by the control unit 6. The second power supply 332 applies a high-frequency voltage across the terminals of the inductively coupled antenna 331, thereby generating a high-frequency induced magnetic field for plasma generation around the antenna 331. This magnetic field acts on the reactive gas, ionizing and plasmaifying it. This inductively coupled plasma has an electron spatial density of 3 × 10⁻⁶. 10 pcs / cm 3 The above high-density plasma.

[0079] <Control Department> Figure 6 It is shown Figure 1 The diagram shows a block diagram of the hardware structure of the control unit 6. The control unit 6 is an electronic circuit device that controls the operation of various parts within the DC sputtering apparatus 100. The control unit 6 includes a processor 61 and a memory 62. The memory 62 is electrically connected to the processor 61 via a bus wiring (not shown).

[0080] The processor 61 may include, for example, a CPU (Central Processing Unit). The memory 62 includes ROM (Read Only Memory), a dedicated memory for storing basic programs, and RAM (Random Access Memory), a memory that can be freely read and written to store various types of information. Furthermore, the memory 62 may also include storage units such as hard disk drives (HDDs) or solid-state drives (SSDs).

[0081] The memory 62 stores the computer program P and setting data. The computer program P is provided to the control unit 6 via a recording medium or via a network line such as the Internet. The setting data is recipe data indicating the processing conditions performed by the DC sputtering apparatus 100. The processor 61 performs processing according to the computer program P and the setting data, and the control unit 6 controls the DC sputtering apparatus 100. As a result, a film deposition process is performed on the substrate W.

[0082] The control unit 6 is electrically connected to the display 661 and the input device 662. The display 661 is a device for displaying various information, such as a liquid crystal display. The input device 662 is a device for inputting user commands to the control unit 6, such as a mouse and keyboard. Alternatively, a touch panel may be provided on the display 661, thereby enabling the display 661 to function as an input device 662.

[0083] The control unit 6 is electrically connected to the heater 11, valve 232, flow adjustment unit 233, first power supply 251, valve 312, flow adjustment unit 313, second power supply 332, rotary drive unit 42 and suction mechanism 5, and controls the operation of these components.

[0084] <Example of Sputtering Device Operation> Figure 7 This is a flowchart illustrating an example of the operation of the DC sputtering apparatus 100. Figure 8 This is a flowchart illustrating the process performed on a substrate W by the operation of a DC sputtering apparatus 100. The DC sputtering apparatus 100 follows... Figure 7 The flowchart is used to perform the actions, thereby repeatedly processing each substrate W. Figure 8 Step S11 (sputtering process) and step S12 (reaction process).

[0085] First, a substrate transport unit (not shown) transports multiple unprocessed substrates W into chamber 1 (step S1). The substrate holding unit 4 then holds the multiple substrates W. Next, a suction mechanism 5 begins to suction gas from chamber 1 (step S2), and a heater 11 begins to heat the substrates W (step S3). The suction mechanism 5 adjusts the pressure within chamber 1 to a pressure reduction range suitable for the film formation process. The heater 11 adjusts the temperature of the substrates W to a temperature range suitable for the film formation process.

[0086] Next, the sputtering gas supply unit 23 supplies sputtering gas, and the reactive gas supply unit 31 begins supplying reactive gas. Furthermore, the first plasma generation unit 25 and the second plasma generation unit 33 plasmaize the gas (step S4). Specifically, the control unit 6 opens valves 232 and 312. Thus, the sputtering gas and reactive gas are supplied to the chamber 1 in parallel. Furthermore, the control unit 6 outputs voltage from the first power supply 251 and the second power supply 332. Additionally, the rotation drive unit 42 rotates the holding device 41 around the revolution axis Q1 (step S5). As a result, the plurality of substrates W revolve around the revolution axis Q1.

[0087] Here, in the film formation process (step S5), the sputtering gas supply unit 23 continuously supplies sputtering gas, the reactive gas supply unit 31 continuously supplies reactive gas, and the first power supply 251 and the second power supply 332 continuously output voltage. In addition, the substrate holding unit 4 causes the substrate W to continuously rotate.

[0088] The substrate W revolves around the revolution axis Q1, thereby alternately passing through the sputtering space 1a and the plasma space 1b. That is, the step S11 (sputtering process) in which the substrate holding part 4 moves the substrate W through the sputtering space 1a and the step S12 (reaction process) in which the substrate holding part 4 moves the substrate W through the plasma space 1b are performed alternately.

[0089] In step S11 (sputtering process), the DC sputtering apparatus 100 deposits gallium particles from the gallium target 21 onto the main surface Wa of the substrate W. Specifically, by sputtering the gallium target 21, gallium particles ejected from the gallium target 21 move toward the substrate W, and the gallium particles adhere to the moving main surface Wa of the substrate W. Thus, a gallium film is formed on the main surface Wa of the substrate W.

[0090] In the next step S12 (reaction process), the DC sputtering apparatus 100 reacts the second element with the gallium film on the main surface Wa of the substrate W formed in step S11 (sputtering process). Specifically, the active species of the second element in the plasma in the plasma space 1b reacts with the gallium film on the main surface Wa of the substrate W, causing the second element to enter the gallium film. Here, since the reactive gas is nitrogen, the gallium film on the main surface Wa of the substrate W is nitrided.

[0091] Next, the control unit 6 determines whether to end the process (step S13). For example, the control unit 6 may also determine whether the number of times a set of steps S11 and S12 has been executed is less than a predetermined number. When the number of executions is less than the predetermined number, the control unit 6 executes step S11 again. As a result, the DC sputtering apparatus 100 continues to perform film deposition on the substrate W. The combination of steps S11 and S12 is repeated, thereby sequentially stacking gallium nitride films on the main surface Wa of the substrate W, and increasing the film thickness. The predetermined number of times is set to a value indicating the degree to which the thickness of the gallium nitride film reaches the target value, for example, it can be set to around several tens of times.

[0092] When the number of executions exceeds a predetermined number, the control unit 6 terminates the film formation process. Specifically, the sputtering gas supply by the sputtering gas supply unit 23, the reactive gas supply by the reactive gas supply unit 31, the power output by the first power supply 251 and the second power supply 332, the revolution of the substrate W by the substrate holding unit 4, the heating of the substrate W by the heater 11, and the gas suction by the suction mechanism 5 are all stopped (step S6). Then, the substrate transport unit removes the substrate W, after the film formation process is completed, from the chamber 1 (step S7).

[0093] As described above, the DC sputtering apparatus 100 repeatedly performs a set of steps S11 (sputtering process) and S12 (reaction process) on the substrate W. Thus, the DC sputtering apparatus 100 is able to form a thin film, namely a gallium nitride film, on the main surface Wa of the substrate W.

[0094] As described above, the DC sputtering apparatus 100 includes: a substrate holding section 4 for holding a substrate W; a target container 22 for holding a gallium target 21 facing the main surface Wa of the substrate W in a first direction (axial direction); a DC power supply (first power supply 251) for applying DC power to the gallium target 21; a conductor 253, one end of which is connected to the negative terminal of the DC power supply and the other end of which is in contact with the gallium target 21 in the target container 22, and the conductor 253 is formed of a gallium corrosion resistant metal; a sputtering gas supply section 23 having a gas supply port (first gas supply port 23a) for supplying sputtering gas between the target container 22 and the substrate holding section 4; and a magnet section 28 located on the side opposite to the substrate holding section 4 relative to the target container 22, forming an annular high-density plasma region PA1 on one side (main surface 21a) of the gallium target 21 in the first direction, where the density of the plasma-plasmized sputtering gas is higher than that of the surrounding area.

[0095] With this structure, DC power can be applied directly to the gallium target 21 via a conductor 253 formed of gallium-corrosion-resistant metal, without passing through the target container 22. Therefore, DC sputtering using a gallium target can be performed while reducing metal contamination.

[0096] <2. Second Implementation Method> Next, the second embodiment will be described. Furthermore, in the following description, elements having the same function as those already described may sometimes be given the same reference numerals or have additional English letter reference numerals, and detailed descriptions may be omitted.

[0097] Figure 9 This is a schematic cross-sectional view showing the target container 22a of the second embodiment. Figure 10 This is a top view of the target container 22a according to the second embodiment, viewed from a vertically upward side. The target container 22a has a container body portion 221, a passage portion 223, and a cover portion 225. The container body portion 221 is the portion that houses the gallium target 21. Except for the portion connected to the passage portion 223, the container body portion 221 also has a shallow bottomed cylindrical shape. The passage portion 223 communicates with the interior of the container body portion 221 and is formed as a concave shape extending radially from the container body portion 221.

[0098] The cover portion 225 is disposed on the upper part of the passage portion 223, covering the opening on the vertical upper side (the side in the first direction) of the passage portion 223. Although the container body portion 221 and the passage portion 223 are formed as one piece, they can also be formed separately. The container body portion 221, the passage portion 223, and the cover portion 225 are preferably formed of ceramic material, and more preferably of ceramic material with gallium nitride, aluminum nitride, or boron nitride as the main components.

[0099] The other end of the conductor 253 is disposed within the passage portion 223 covered by the cover portion 225. That is, the conductor 253 is inserted into the passage portion 223 through the upper opening of the passage portion 223 that is not covered by the cover portion 225. Then, the end of the conductor 253 is disposed directly below the cover portion 225 within the passage portion 223.

[0100] The bottom surface of the passage portion 223 is at the same height (axial position) as the bottom surface of the container body portion 221, so that the connection between the bottom surface of the passage portion 223 and the bottom surface of the container body portion 221 is formed as a single surface. When the gallium target 21 is disposed on the container body portion 221, the liquid gallium moves toward the passage portion 223. As a result, the end of the conductor 253 disposed in the passage portion 223 comes into contact with the liquid gallium. Therefore, a DC voltage can be applied to the gallium target 21 disposed on the container body portion 221.

[0101] In this way, the end of conductor 253 is positioned in the passage portion 223, thereby allowing the other end of conductor 253 to exit the high-density plasma region PA1. This reduces the likelihood of conductor 253 being sputtered. Furthermore, the other end of conductor 253 is positioned in the passage portion 223, where its vertical upper side is covered by the cover portion 225. This prevents conductor 253 from being exposed to the high-density plasma. This further reduces the likelihood of conductor 253 being sputtered.

[0102] <3. Third Implementation Method> Figure 11 This figure shows the target container 22b according to the third embodiment. The target container 22b is formed as a shallow-bottomed cylindrical shape, and a through hole 227 is provided in the side wall extending vertically upward from the bottom surface. A portion of the conductor 253a, namely a conductive bolt 255, is inserted into the through hole 227. In other words, the conductive bolt 255 penetrates the target container 22b through its side surface. The conductive bolt 255 is the portion corresponding to the other end of the conductor 253a and is formed of a gallium-resistant metal such as molybdenum, copper, or stainless steel. The conductive bolt 255 is connected to the first power source 251 via the metal wire of the conductor 253a. The metal wire of the conductor 253a does not contact the gallium target 21, so it can also be formed of a metal other than a gallium-resistant metal. Furthermore, the metal wire of the conductor 253a is preferably covered with an insulating material such as resin.

[0103] When the gallium target 21 is disposed in the target container 22, the conductive bolt 255 of the conductor 253a contacts the gallium target 21. Thus, the first power supply 251 is electrically connected to the gallium target 21, thereby enabling the application of a DC voltage to the gallium target 21.

[0104] The conductive bolt 255 is disposed on the side wall of the target container 22, thus preventing the conductive bolt 255 from being exposed to the high-density plasma of argon gas formed above the gallium target 21. Therefore, the sputtering of the conductor 253a can be reduced, thereby reducing metal contamination of the gallium film.

[0105] The conductive bolt 255 is provided on the side wall of the target container 22, so that the metal wire of the conductor 253a can be connected to the conductive bolt 255 exposed on the radially outer side of the target container 22. Therefore, interference between the metal wire of the conductor 253a and the cooling container 29 or the like disposed at the bottom of the target container 22 can be avoided.

[0106] Furthermore, the through-hole 227 of the target container 22 can be provided at the bottom of the target container 22, and the conductive bolt 255 can be disposed at the bottom of the target container 22. In other words, the conductive bolt 255 can also be disposed on the bottom surface of the target container 22 in a manner that penetrates through the target container 22. In this case, even when sputtering is performed and the gallium target 21 is reduced, the exposure of the conductive bolt 255 can be reduced.

[0107] <4. Variations> Although the implementation of the DC sputtering apparatus has been described above, the present invention is not limited to the above content and can be modified in various ways.

[0108] For example, in the above embodiment, although the target container 22 is formed with a uniform depth, this is not necessary. For example, the target container 22 may also have a shape that increases in depth towards the center of the target container 22. Furthermore, the target container 22 does not need to have a circular shape when viewed from above. For example, the target container 22 may also have a rectangular shape when viewed from above.

[0109] In the DC sputtering apparatus 100 described above, the sputtering space 1a and the plasma space 1b are alternately arranged around the revolution axis Q1. Furthermore, by causing the substrate W to revolve around the revolution axis Q1, the substrate W alternately passes through the sputtering space 1a and the plasma space 1b. However, the structure of the DC sputtering apparatus 100 is not limited to this structure. For example, the sputtering space 1a and the plasma space 1b may also be arranged in a straight line. In this case, the substrate W may also be able to move back and forth between the sputtering space 1a and the plasma space 1b.

[0110] Although the present invention has been described in detail, the above description is illustrative in all embodiments and the invention is not limited thereto. It is understood that numerous variations not illustrated can be conceived without departing from the scope of the invention. The structures described in the above embodiments and variations can be appropriately combined or omitted as long as they do not contradict each other.

[0111] Explanation of reference numerals in the attached figures 4: Substrate holding section 21: Gallium target, 22, 22a, 22b: Target material container, 23: Sputtering gas supply unit 23a: First gas supply port 28: Magnet part 31: Reactive gas supply unit 100: DC sputtering equipment 221: Container body section 223: Distribution Center 225: Cover section, 227: Through hole, 251: First power supply 253, 253a: Conductors, 255: Conductive bolt (conductor) 291: Cooling water, PA1: High-density plasma region W: substrate.

Claims

1. A DC sputtering apparatus, wherein, have: Substrate holding section, for holding the substrate; A target container holds a gallium target in a manner that faces the main surface of the substrate in a first direction; A DC power supply applies DC power to the gallium target. A conductor, one end of which is connected to the negative terminal of the DC power supply, and the other end of which is in contact with the gallium target inside the target container, and the conductor is formed of a gallium-resistant metal; The sputtering gas supply unit has a gas supply port for supplying sputtering gas between the target container and the substrate holding unit; as well as The magnet portion, located on the side opposite to the substrate holding portion relative to the target container, has an annular high-density plasma region formed on one side of the gallium target in the first direction, where the density of the plasma-plasmified sputtering gas is higher than that of the surrounding area.

2. The DC sputtering apparatus according to claim 1, wherein, The gallium-resistant metal includes molybdenum, copper, or stainless steel.

3. The DC sputtering apparatus according to claim 1 or 2, wherein, The target container is formed of ceramic material.

4. The DC sputtering apparatus according to claim 3, wherein, The target container is formed of a ceramic material with gallium nitride, aluminum nitride, or boron nitride as the main components.

5. The DC sputtering apparatus according to any one of claims 1 to 4, wherein, The conductor is configured in a second direction intersecting the first direction in a manner that separates it from the high-density plasma region.

6. The DC sputtering apparatus according to any one of claims 1 to 5, wherein, The magnet portion includes a ring-shaped first permanent magnet. The conductor is positioned in a second direction that intersects the first direction, separated from the first permanent magnet.

7. The DC sputtering apparatus according to any one of claims 1 to 6, wherein, The target container has: The main body of the container houses the gallium target, and The passageway communicates with the interior of the container body and is formed as a concave shape extending in a second direction that intersects the first direction; The other end of the conductor is disposed within the passage portion.

8. The DC sputtering apparatus according to claim 7, wherein, The target container also has: A cover portion that covers the opening of the passage portion on one side in the first direction; The other end of the conductor is disposed in the portion of the passage that is covered by the cover portion.

9. The DC sputtering apparatus according to any one of claims 1 to 8, wherein, The sputtering gas contains argon.

10. The DC sputtering apparatus according to any one of claims 1 to 9, wherein, It also has: The reactive gas supply unit supplies reactive gas. The reactive gas supply unit supplies the reactive gas in such a way that the gallium deposited on the main surface of the substrate reacts with the plasma-generated reactive gas.

11. The DC sputtering apparatus according to claim 10, wherein, The reactive gas contains nitrogen.

12. The DC sputtering apparatus according to any one of claims 1 to 11, wherein, The target container has a bottom surface and side surfaces that hold the gallium target on the inside. The conductor penetrates the target container on the bottom or side.

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