TW202536216A - Dc sputtering apparatus - Google Patents

Abstract

This invention provides a DC sputtering technique that reduces metal contamination while using gallium targets. The DC sputtering apparatus includes: a substrate holding part that holds a substrate; a target container that holds a gallium-containing target in a first direction facing the main surface of the substrate; a DC power supply that applies DC power to the gallium target; and a conductor, one end of which is connected to the negative side of the DC power supply, and the other end of which contacts the gallium target in the target container, and is formed of a gallium-resistant metal. In addition, the DC sputtering apparatus includes: a sputtering gas supply unit having a gas supply port for supplying sputtering gas between the target container and the substrate holding unit; and a magnet unit located opposite the target container to the substrate holding unit, and having a ring-shaped high-density plasma region on the surface of the gallium target on one side in a first direction, wherein the density of the plasmad sputtering gas is higher than that of the periphery.

Description

DC Splashing Equipment

This invention relates to a DC sputtering apparatus.

Gallium nitride (GaN) used in power devices or LEDs (light-emitting diodes) is often deposited using vacuum deposition methods, such as MOCVD (metal-organic chemical vapor deposition). However, MOCVD GaN films utilize flammable or toxic gases like triethylgallium (TEG) and ammonia ( _NH3 ), resulting in a significant environmental impact. Furthermore, over 90% of these gases are emitted, leading to 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 uses metal or solid compounds on the target material. Therefore, the film formation cost and environmental impact are relatively low.

As sputtering targets, gallium nitride (GaN) sintered targets or metal gallium can be used. GaN sintered targets, due to their insulating properties, require sputtering with a high-frequency RF power supply, resulting in a lower film formation rate and lower productivity. On the other hand, when using metal gallium as a sputtering target, its conductivity allows for direct current (DC) sputtering, thus improving productivity. Therefore, from a productivity standpoint, metal gallium is superior to GaN sintered targets as sputtering targets.

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

Patent Document 1: Japanese Patent Application Publication No. 2015-229782

(Problem to be solved by the invention) However, liquid gallium is highly corrosive to other metals. Therefore, as described in Patent 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. Therefore, their presence may lead to film degradation, and further cause the device performance to deteriorate.

The purpose of this invention is to provide a technique for DC sputtering of gallium targets while reducing metal contamination. (Technical means to solve the problem)

To solve the above problems, the first aspect of this invention is a DC sputtering apparatus, comprising: a substrate holding portion 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; and a conductor, one end of which is connected to the negative terminal of the DC power supply, and the other end of which contacts the gallium target inside the target container, and is... Formed by 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 opposite the target container to the substrate holding section, and having a plasma-plated high-density plasma region formed on the surface of the gallium target on one side of the first direction, wherein the density of the sputtering gas is higher than that of the periphery.

The second state of the present invention is in the DC sputtering apparatus of the first state, wherein the main component of the conductor system is molybdenum, copper or stainless steel.

The third state of the present invention is in the DC sputtering apparatus of the first or second state, wherein the target container is formed by ceramic material.

The fourth embodiment of the present invention is based on the DC sputtering apparatus of the third embodiment, wherein the target container is formed by a ceramic material whose main components are gallium nitride, aluminum nitride, or boron nitride.

The fifth aspect of the present invention is a DC sputtering apparatus in any of the first to fourth aspects, wherein the conductor is disposed separately from the high-density plasma region in a second direction intersecting the first direction.

The sixth embodiment of the present invention is a DC sputtering apparatus in any one of the first to fifth embodiments, wherein the magnetic part includes a ring-shaped first permanent magnet, and the conductor is arranged separately from the first permanent magnet in a second direction intersecting the first direction.

The seventh embodiment of the present invention 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.

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

The ninth state of the present invention is a DC sputtering apparatus in any one of the first to eighth states, wherein the sputtering gas comprises argon.

The tenth aspect of the present invention is a DC sputtering apparatus of any one of the first to ninth aspects, further comprising: a reactive gas supply unit that supplies reactive gas; the reactive gas supply unit supplies the reactive gas so that the gallium deposited on the main surface of the substrate reacts with the plasma-plated reactive gas.

The 11th state of the present invention is in the DC sputtering apparatus of the 10th state, wherein the reactive gas contains nitrogen.

The 12th embodiment of the present invention is a DC sputtering apparatus of any one of the 1st to 11th 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 on the bottom surface or the side surface. (Effects compared to prior art)

According to the DC sputtering apparatus of the first to twelfth embodiments of the present invention, DC power can be applied directly to the gallium target without passing through a target container, but through a conductor formed by a gallium corrosion-resistant metal. Therefore, DC sputtering of the gallium target can be performed while reducing metal contamination.

According to the DC sputtering apparatus of the third aspect of the present invention, since the target container is formed by ceramic material, the metal contamination generated by the target container can be reduced.

According to the DC sputtering apparatus of the fifth aspect of the present invention, since it can reduce the sputtering of the conductor, it can reduce the metal contamination generated by the conductor.

According to the DC sputtering apparatus of the sixth aspect of the present invention, since it can reduce the sputtering of the conductor, it can reduce the metal contamination generated by the conductor.

According to the DC sputtering apparatus of the seventh aspect of the present invention, since it can make the conductor leave the high-density plasma region, the sputtering of the conductor can be reduced.

According to the DC sputtering apparatus of the eighth aspect of the present invention, since it can avoid the conductor being exposed to high-density plasma, the occurrence of conductor sputtering can be reduced.

Hereinafter, embodiments of the invention will be described with reference to the attached drawings. Furthermore, the constituent elements described in these embodiments are merely illustrative and are not intended to limit the scope of the invention to those constituent elements. In the drawings, for ease of understanding, the dimensions or quantities of the parts may be exaggerated or simplified as needed.

<1. First Embodiment> Figure 1 is a side view schematically showing an example of the configuration of the DC sputtering apparatus 100 of the first embodiment. Figure 2 is a top view schematically showing an example of the configuration of the DC sputtering apparatus 100 shown in Figure 1. Figure 1 is a cross-sectional view schematically showing the DC sputtering apparatus 100 cut along a plane along the zigzag A-A line shown in Figure 2.

The DC sputtering apparatus 100 is a film-forming apparatus that performs a film-forming process on a substrate W by reactive sputtering. 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 sapphire, silicon (Si), or silicon carbide (SiC) substrate. The substrate W has, for example, a circular plate shape. Furthermore, the material and shape of the substrate W are not limited thereto and can be appropriately changed.

The DC sputtering apparatus 100 includes: a chamber 1, a sputtering section 2, a plasma section 3, a substrate holding section 4, a suction mechanism 5, and a control section 6. The chamber 1 has a box-shaped, hollow structure. The internal space of the chamber 1 serves as the processing space for film deposition on the substrate W. The chamber 1 is a vacuum chamber, a sealable container maintained in a vacuum state. A transfer mechanism (not shown) is provided in the chamber 1. This mechanism can switch the internal state of the chamber 1 to: a connected state connected to the external space, and a sealed state isolated from the external space. In the connected state, the substrate transfer section (not shown) transfers the unprocessed substrate W into the chamber 1. In a closed state, the DC sputtering apparatus 100 performs film deposition on the substrate W. Then, the transfer mechanism connects the chamber 1 to the outside, and the substrate transfer unit removes the substrate W, which has undergone film deposition, from the chamber 1 while the chamber is in this connected state.

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 draws gas from the suction port 5a, thereby reducing the pressure in the chamber 1 and adjusting the pressure to a predetermined pressure reduction range. As the suction mechanism 5, a vacuum pump can be used, for example, and as a more specific example, a turbine molecular pump can be used.

The processing space within chamber 1 includes a sputtering space 1a and a plasma space 1b. The sputtering space 1a and the plasma space 1b are arranged along a circumferential direction associated with a predetermined axis of revolution Q1, which is a vertical axis. Furthermore, a physical structure (e.g., a partition plate) for separating the sputtering space 1a and the plasma space 1b may also be provided within chamber 1.

In the sputtering space 1a, a gallium target 21 is disposed. Sputtering is performed on the gallium target 21 in the sputtering space 1a. The gallium target 21 contains gallium as a first element. In the plasma space 1b, a reactive gas is supplied via a plasma section 3. The reactive gas contains a second element (e.g., nitrogen). The plasma section 3 plasma-plasmizes the reactive gas.

The substrate holding part 4 is disposed in the chamber 1. The substrate holding part 4 holds the substrate W while causing the substrate W to revolve around the axis of revolution Q1, and causes the substrate W to move alternately to the sputtering space 1a and the plasma space 1b.

Figure 3 is a perspective view schematically showing an example of the configuration of the substrate holding part 4 and the heater 11 shown in Figure 1. In the example of Figure 3, the substrate holding part 4 holds a plurality of substrates W (six in this example) arranged in a circumferential direction related to the axis of revolution Q1. Furthermore, the substrate holding part 4 does not need to hold a plurality of substrates W simultaneously. The substrate holding part 4 may also be configured to hold only a single substrate W. The substrate holding part 4 holds the substrate W in a horizontal position. The horizontal position means that the thickness direction of the substrate W (the normal direction of the main surface Wa) is in a vertical direction. When the plurality of substrates W are held by the substrate holding part 4, the main surface Wa (bottom in Figure 3) of each substrate W is exposed in the chamber 1 (see Figure 1).

The substrate holding section 4 causes the substrates W to revolve around the axis of revolution 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 substrates W by having them 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, the active species of the second element (including at least one of ions and free radicals) generated by the plasmaification of the reactive gas reacts with the gallium atoms on the main surface Wa of the substrate W. This forms a predetermined thin film containing gallium and the second element on the main surface Wa of the substrate W.

The following are examples where the direction in which the revolution axis Q1 extends is called 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."

<Substrate Holding Section> The substrate holding section 4 includes a holding device 41 and a rotation drive 42. The holding device 41 holds a plurality of substrates W in a circumferentially spaced arrangement. 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 in the holding device 41. The plurality of through holes 41a are formed, for example, at equal intervals along the circumferential direction and pass through the holding device 41 axially. Each through hole 41a has a stepped shape that narrows towards 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 by means of the stepped portion of each through hole 41a.

The rotary drive unit 42 is controlled by the control unit 6. The rotary drive unit 42 causes the holding device 41 to rotate around the revolution axis Q1. Thus, the plurality of substrates W held by the holding device 41 revolve around the revolution axis Q1. The rotary drive unit 42, for example, has a motor and a rod shaft. The motor is connected to the holding device 41 via the rod shaft. The upper end of the rod shaft is connected to the lower end of the holding device 41 and extends along the revolution axis Q1. The motor causes the rod shaft to rotate around the revolution axis Q1, thereby causing the holding device 41 to rotate around the revolution axis Q1.

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

The sputtering section 2 includes a gallium target 21, a sputtering gas supply section 23, and a first plasma generation section 25. Furthermore, the sputtering gas supply section 23 and the first plasma generation section 25 are omitted from the figure in FIG2.

The 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 opposite a portion of the circumferential direction of the moving path R1 of the substrate W. In the example shown in FIG1, the gallium target 21 is located vertically lower than the substrate holding portion 4.

The gallium target 21 has, for example, a plate-like shape, and in the example shown in Figure 2, it has a circular shape when viewed from above. Here, "viewed from above" refers to observation along the axial direction. The gallium target 21 has a main surface 21a facing the vertically upward side. 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 the 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.

<Sputtering Gas Supply Unit> 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. In the example shown in FIG1, the sputtering gas supply unit 23 has a plurality of (two in this example) gas supply pipes 231, valves 232, flow regulating units 233, and a common pipe 234. The upstream end of each gas supply pipe 231 is connected to the downstream end of a common pipe 234. The upstream end of the common pipe 234 is connected to the sputtering gas supply source 235. Sputtering gas supply source 235 supplies sputtering gas to the upstream end of common pipe 234. Gas supply pipe 231 has a first gas supply port 23a that is open in the sputtering space 1a. The sputtering gas flows within 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 movement path R1 of the substrate W and the gallium target 21.

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 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.

<First Plasma Generation Unit> The first plasma generation unit 25 plasmaizes the sputtering gas within the sputtering space 1a, causing 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. These sputtered particles move toward the substrate holding part 4 to the vertically upper side.

In the example shown in Figure 1, the first plasma generating unit 25 has a DC power supply, namely the 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 between the gallium target 21 and the chamber 1, for example. More specifically, the first power supply 251 has, for example, an alternating power circuit (not shown), which applies DC power by applying a negative potential to the gallium target 21. As shown in Figure 1, the chamber 1 can also be grounded. In addition, the substrate holding unit 4 can also be electrically connected to the chamber 1.

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

<Chimney> In the example shown in FIG1, the sputtering section 2 has a chimney 27. The chimney 27 is provided within the sputtering space 1a. The chimney 27 has a box-shaped hollow shape and surrounds the gallium target 21. The upper plate portion 271 of the chimney 27 has an opening 27a facing the gallium target 21 in the axial direction. The opening 27a passes 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.

Figure 4 is a schematic cross-sectional view of the target container 22 of the sputtering section 2 shown in Figure 1. Figure 5 is a top view of the target container 22 of the sputtering section 2 shown in Figure 1, viewed from the vertical top. As shown in Figure 4, 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 rises vertically from the periphery of the bottom surface towards the vertical top. Since the melting point of gallium is 29.76°C, the gallium target 21 may melt due to the 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 can store the liquid gallium target 21 inside.

The target container 22 is preferably formed of a ceramic material. Specifically, the target container 22 can be formed of a ceramic material with gallium nitride, aluminum nitride, or boron nitride as the main component. As long as it is a III-V group aluminum or boron nitride, it can reduce the impact on the gallium nitride film element compared to using other metal nitrides.

When a conductive container is used as the target container 22, the high corrosivity of liquid gallium to other metals can lead to embrittlement of the container itself and melting of the container material onto the gallium target 21. When other metals melt onto the gallium target 21, they are incorporated into the gallium film as impurities, potentially causing degradation of the film and component performance. Although molybdenum, a metal resistant to gallium corrosion, can reduce the possibility of melting, its high hardness and high price make it difficult to process.

When molybdenum is used to fabricate the target container 22, if the amount of gallium target 21 inside the container decreases due to continuous film deposition, there is a possibility that liquid gallium may slosh, exposing the bottom of the container and causing the molybdenum in the container material to be sputtered and contaminate the gallium film. Furthermore, since the same potential is applied to molybdenum as to the gallium target 21, there is a possibility that molybdenum may be doped into the gallium film due to sputtering caused by argon ions.

The sputtering portion 2 has a magnet portion 28. The magnet portion 28 is located on the opposite side of the substrate holding portion 4 from the target container 22. The magnet portion 28 has a first permanent magnet 281 in the shape of a ring (here, a circular ring) 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 portion 28 forms magnetic lines of force from the first permanent magnet 281 to the second permanent magnet 282 on the main surface 21a of the gallium target 21. Electrons in the plasma generated by the first plasma generation unit 25 are accelerated (EB drift) while being retained near the main surface 21a of the gallium target 21 by magnetic field lines. These drifting, high-energy electrons collide with the sputtering gas, argon, producing electrons and argon ions. As a result, a high-density, annular plasma region PA1 with a high concentration of argon plasma is formed on the main surface 21a of the gallium target 21.

Furthermore, the first permanent magnet 281 does not need to be formed into a circular ring shape; it can also be formed into a ring shape different from a circular ring shape. That is, the first permanent magnet 281 only needs to be in the shape of a high-density plasma region that can form a closed ring shape. For example, the first permanent magnet 281 can be formed into a racetrack shape (ellipse, or a rounded rectangle composed of two parallel lines of equal length (straight lines) and two semicircles (corners)).

A cooling container 29 is disposed on the vertically lower side of the target container 22. The cooling container 29 cools the target container 22, thereby cooling the gallium target 21. 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).

As shown in Figure 4, the first plasma generating unit 25 has a conductor 253. The conductor 253 has metal wires. One end of the conductor 253 is connected to the negative side of the DC power supply, i.e., the first power supply 251, while 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.

The metal wires of conductor 253 are formed using 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 caused 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.

As shown in Figure 4, the other end of the conductor 253 is radially disposed on the outer side of the annular high-density plasma region PA1. The high-density plasma region PA1 is a region where sputtering gas (argon) cations exist at a high density. Therefore, by disposing the conductor 253 on the outer side of the high-density plasma region PA1, the sputtering of the conductor 253 can be reduced. Consequently, metal contamination of the gallium film caused by the conductor 253 can be reduced.

As shown in Figure 5, the other end of the conductor 253 is radially positioned further outward than 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 second permanent magnet 282. Therefore, positioning the conductor 253 further outward than the first permanent magnet 281 further reduces the likelihood of sputtering on the conductor 253.

<Plasma Section> Returning to Figure 1, the plasma section 3 has a second gas supply port 31a that is open in the plasma space 1b. The plasma section 3 supplies reactive gas to the plasma space 1b through the second gas supply port 31a. Furthermore, the plasma section 3 plasmaifies the reactive gas within the plasma space 1b. Specifically, the plasma section 3 has a reactive gas supply section 31 and a second plasma generation section 33.

<Reactive Gas Supply Unit> In the example shown in FIG1, the reactive gas supply unit 31 has a plurality of (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 a 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. In the example shown in FIG1, the opening direction of the second gas supply port 31a in the gas supply pipe 311 is parallel to the axial direction and faces the substrate holding part 4. In the example in FIG1, the downstream end of each gas supply pipe 311 corresponds to the second gas supply port 31a. In the example shown in Figure 1, the two second air inlets 31a are arranged to be radially spaced apart.

As a 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. Furthermore, the reactive gas can also 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 mainly describes the case where nitrogen is used as the reactive gas.

Valve 312 is provided in common pipe 314 and opens and closes common pipe 314. Flow regulating unit 313 is provided in common pipe 314 and regulates the flow rate of the reactive gas flowing in common pipe 314. Flow regulating unit 313 is, for example, a mass flow controller. Valve 312 and flow regulating unit 313 are controlled by control unit 6.

<Second Plasma Generation Unit> The second plasma generation unit 33 plasma-generates nitrogen gas supplied to the chamber 1 from the second gas supply port 31a. The nitrogen-active species with higher reactivity generated by plasma-generation 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, the gallium film on the main surface Wa is nitrided.

In the example shown in Figure 1, 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 at a position that is further vertically downward than the moving path R1 of the substrate W. The inductively coupled antenna 331 has a conductive member 3311 that is convex, or approximately U-shaped, toward the vertically upward side.

The conductive component 3311 is disposed within the chamber 1 with its two ends positioned vertically downwards. The conductive component 3311 is mounted at the bottom of the chamber 1. In the example shown in Figure 2, the conductive component 3311 is arranged with its two ends aligned circumferentially. The two ends of the conductive component 3311 may, for example, penetrate the bottom of the chamber 1, and these two ends are electrically connected to the second power source 332. The conductive component 3311 functions as an electrode (antenna) for plasma generation.

In the example shown in Figures 1 and 2, a plurality of (two in this case) inductively coupled antennas 331 are provided, and each inductively coupled antenna 331 is located near each of the second air supply ports 31a. In the example shown in Figures 1 and 2, the inductively coupled antenna 331 is positioned axially opposite to the second air supply port 31a of the air supply pipe 311. In other words, the second air supply port 31a is located radially between the two ends of the inductively coupled antenna 331 (conductive component 3311).

The second power supply 332 supplies high-frequency power to the inductively coupled antenna 331. The second power supply 332 includes, for example, an inverter circuit and a matching circuit, and is controlled by the control unit 6. The second power supply 332 applies a high-frequency voltage to both ends of the inductively coupled antenna 331, thereby generating a high-frequency induced magnetic field for plasma generation around the inductively coupled antenna 331. This field acts on the reactive gas, ionizing and plasmaizing it. The inductively coupled plasma is a high-density plasma with an electron space density of 3 × ^10¹⁰ electrons/cm³ or ^higher .

<Control Unit> Figure 6 is a block diagram showing the hardware configuration of the control unit 6 shown in Figure 1. The control unit 6 is an electronic circuit machine 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 bus wiring (not shown).

The processor 61 may include, for example, a CPU (Central Processing Unit). The memory 62 may include ROM (Read Only Memory), which is dedicated to reading basic programs, and RAM (Random Access Memory), which can freely read and write various types of information. In addition, the memory 62 may also include storage devices such as hard disk drives (HDDs) or solid-state drives (SSDs).

Memory 62 stores computer program P and setting data. Computer program P is provided to control unit 6 via recording media or network lines such as the Internet. Setting data is formula data displaying the processing conditions performed by DC sputtering apparatus 100. Processor 61 performs processing according to computer program P and setting data, while control unit 6 controls DC sputtering apparatus 100. Thereby, it performs film formation processing on substrate W.

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 an LCD display. The input device 662 is a device for inputting user commands into the control unit 6, such as a mouse and keyboard. Furthermore, a touch panel can also be provided on the display 661, thereby enabling the display 661 to function as the input device 662.

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.

<Example of Sputtering Apparatus Operation> Figure 7 is a flowchart showing an example of the operation of the DC sputtering apparatus 100. Figure 8 is a flowchart showing the steps performed on a substrate W by the operation of the DC sputtering apparatus 100. The DC sputtering apparatus 100 operates according to the flowchart in Figure 7, thereby repeatedly performing steps S11 (sputtering step) and S12 (reaction step) of Figure 8 on each substrate W.

First, a substrate transport unit (not shown) transports a plurality of unprocessed substrates W into chamber 1 (step S1). Thereby, substrate holding unit 4 holds the plurality of substrates W. Next, suction mechanism 5 begins to suction gas from chamber 1 (step S2), and heater 11 begins to heat the substrates W (step S3). Suction mechanism 5 adjusts the pressure within chamber 1 to a depressurization range suitable for film formation. Heater 11 adjusts the temperature of substrates W to a temperature range suitable for film formation.

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 plasma-encapsulate the gas (step S4). Specifically, the control unit 6 opens valves 232 and 312. This allows it to supply the sputtering gas and reactive gas in parallel into the chamber 1. Additionally, the control unit 6 outputs voltage from the first power supply 251 and the second power supply 332. Furthermore, the rotary drive unit 42 causes the holding device 41 to rotate around the revolution axis Q1 (step S5). This causes the plurality of substrates W to revolve around the revolution axis Q1.

Here, in the film formation process (step S5), the sputtering gas supply unit 23 continuously supplies sputtering gas, while 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.

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

In step S11 (sputtering step), 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.

In the next step S12 (reaction step), the DC sputtering apparatus 100 pairs the gallium film on the main surface Wa of the substrate W formed in step S11 (sputtering step) to react with the second element. 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.

Next, the control unit 6 determines whether to end the process (step S13). For example, the control unit 6 can also determine whether the number of times a set of steps S11 and S12 has been executed has not reached a predetermined number. When the number of executions has not reached the predetermined number, the control unit 6 executes step S11 again. In this way, 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 depositing a gallium nitride film on the main surface Wa of the substrate W, and its film thickness increases. The predetermined number of times is a value set to the degree to which the thickness of the gallium nitride film can reach the target value, for example, it can be set to about several tens of times.

When the number of executions exceeds a predetermined number, the control unit 6 terminates the film formation process. Specifically, the supply of sputtering gas by the sputtering gas supply unit 23, the supply of reactive gas by the reactive gas supply unit 31, the output of electricity 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 suction of gas by the suction mechanism 5 are all stopped (step S6). Then, the substrate transport unit removes the substrate W, which has completed the film formation process, from the chamber 1 (step S7).

As described above, the DC sputtering apparatus 100 repeatedly performs a set of steps S11 (sputtering step) and S12 (reaction step) on the substrate W. In this way, the DC sputtering apparatus 100 can form a thin film, namely a gallium nitride film, on the main surface Wa of the substrate W.

As described above, the DC sputtering apparatus 100 includes: a substrate holding section 4 that holds a substrate W; a target container 22 that holds 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) that applies DC power to the gallium target 21; and a conductor 253, one end of which is connected to the negative side of the DC power supply, and the other end of which contacts the gallium target 21 inside the target container 22, and which is resistant to gallium corrosion. Formed by corrosive metal; sputtering gas supply section 23, which has 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, which is located opposite to the target container 22 and the substrate holding section 4, and forms a high-density annular plasma region PA1 on the surface (main surface 21a) of the gallium target 21 in the first direction, where the density of the aforementioned sputtering gas is higher than that of the periphery.

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

<2. Second Embodiment> Next, the second embodiment will be explained. Furthermore, in the following explanation, there are instances where elements having the same function as the previously explained elements are given the same symbols or additional English letter symbols and their detailed explanations are omitted.

Figure 9 is a schematic cross-sectional view showing the target container 22a of the second embodiment. Figure 10 is a top view of the target container 22a of the second embodiment viewed from a vertically upper 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. The container body portion 221, except for the portion connected to the passage portion 223, has a shallow bottom and a 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.

The cover portion 225 is disposed above the passage portion 223 and covers the opening on the vertically upper side (one 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 separate. 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.

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.

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. This allows the end of the conductor 253 disposed within the passage portion 223 to contact the liquid gallium. Therefore, a DC voltage can be applied to the gallium target 21 disposed on the container body portion 221.

Thus, one end of the conductor 253 is positioned in the passage portion 223, thereby allowing the other end of the conductor 253 to be away from the high-density plasma region PA1. This reduces the likelihood of the conductor 253 being sputtered. Furthermore, the other end of the conductor 253 is positioned in the portion of the passage portion 223 that is vertically covered by the cover portion 225. This prevents the conductor 253 from being exposed to the high-density plasma. This further reduces the likelihood of the conductor 253 being sputtered.

<3. Third Embodiment> Figure 11 shows the target container 22b of the third embodiment. The target container 22b is formed as a shallow-bottomed cylindrical shape, and a through hole 227 is provided on 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 is located on the side of the target container 22b and penetrates through the target container 22b. The conductive bolt 255 is the portion corresponding to the other end of the conductor 253a, and it is formed by a gallium-resistant metal such as molybdenum, copper, or stainless steel. The conductive bolt 255 is connected to the first power supply 251 via the metal wire of the conductor 253a. Since the metal wires of conductor 253a are not in contact with the gallium target 21, they can also be formed using metals other than gallium-resistant metals. Furthermore, the metal wires of conductor 253a are preferably covered with insulating materials such as resin.

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. Thereby, the first power supply 251 is electrically connected to the gallium target 21, and thus, it can apply a DC voltage to the gallium target 21.

The conductive bolt 255 is located 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. Consequently, it reduces the sputtering of the conductor 253a, thereby reducing metal contamination of the gallium film.

A 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 radially outward on the target container 22. Therefore, interference between the metal wire of the conductor 253a and the cooling container 29 disposed below the target container 22 can be avoided.

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 still be reduced.

<4. Variations> Although the embodiments of the DC sputtering apparatus have been described above, the present invention is not limited to the above content and can be varied.

For example, in the above embodiment, although the depth of the target container 22 is formed to be uniform, it is not necessary. For example, the target container 22 may also have a shape that gradually deepens 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.

In the aforementioned DC sputtering apparatus 100, 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 can alternately pass through the sputtering space 1a and the plasma space 1b. However, the configuration of the DC sputtering apparatus 100 is not limited to this configuration. For example, the sputtering space 1a and the plasma space 1b can also be arranged in a straight line. In this case, the substrate W can also move back and forth between the sputtering space 1a and the plasma space 1b.

Although the present invention has been described in detail above, all the embodiments described above are merely illustrative, and the present invention is not limited thereto. Numerous variations not illustrated can be interpreted as not departing from the scope of the present invention. The components described in the above embodiments and variations may be appropriately combined or omitted, provided they do not contradict each other.

1: Chamber 1a: Sputtering space 1b: Plasma space 2: Sputtering section 3: Plasma section 4: Substrate holding section 5: Suction mechanism 5a: Suction port 6: Control unit 11: Heater 21: Gallium sputtering target (target) 21a: Main surface 22, 22a, 22b: Target container 23: Sputtering gas supply section 23a: First gas supply port 25: First plasma generation section 27 : Chimney-shaped duct 27a: Opening 28: Magnet section 29: Cooling container 31: Reactive gas supply section 31a: Second gas supply port 33: Second plasma generation section 41: Holding device 41a: Through hole 42: Rotary drive section 61: Processor 62: Memory 100: DC sputtering device 221: Container body section 223: Passage section 225: Cover Part 227: Through hole; 231: Air supply pipe; 232: Valve; 233: Flow adjustment part; 234: Common pipe; 235: Splashing gas supply source; 251: First power supply (DC power supply); 253, 253a: Conductor; 255: Conductive bolt (conductor); 271: Upper plate part; 281: First permanent magnet; 282: Second permanent magnet; 291: Cooling water 3 11: Gas supply pipe; 312: Valve; 313: Flow adjustment unit; 314: Common pipe; 315: Reactive gas supply source; 331: Inductively coupled antenna; 332: Second power supply; 661: Display; 662: Input device; 3311: Conductive component; P: Computer program; PA1: High-density plasma area; Q1: Revolution axis; R1: Movement path; W: Substrate; Wa: Main surface.

Figure 1 is a side view schematically showing an example of the configuration of a DC sputtering apparatus according to the first embodiment of the present invention. Figure 2 is a top view schematically showing an example of the configuration of the DC sputtering apparatus shown in Figure 1. Figure 3 is a perspective view schematically showing an example of the configuration of the substrate holding part and the heater shown in Figure 1. Figure 4 is a schematic cross-sectional view showing the target container of the sputtering section shown in Figure 1. Figure 5 is a top view of the target container of the sputtering section shown in Figure 1 viewed from a vertical top. Figure 6 is a block diagram showing the hardware configuration of the control unit shown in Figure 1. Figure 7 is a flowchart showing an example of the operation of the DC sputtering apparatus. Figure 8 is a flowchart showing the steps performed on a substrate by the operation of a DC sputtering apparatus. Figure 9 is a schematic cross-sectional view of the target container of the second embodiment. Figure 10 is a top view of the target container of the second embodiment viewed from a vertical top. Figure 11 is a diagram showing the target container of the third embodiment.

21: Gallium sputtering target (sputtering target)

21a: Main face

22: Target Material Container

25: First Plasma Production Department

28: Magnet Section

29: Cooling Containers

251: Power Source 1 (DC Power)

253: Conductor

281: The First Permanent Magnet

282: Second Permanent Magnet

291: Cooling Water

PA1: High-density plasma region

Claims (12)

A DC sputtering apparatus includes: a substrate holding portion 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; and a conductor, one end of which is connected to the negative terminal of the DC power supply, and the other end of which contacts the gallium target within the target container, wherein the conductor is made of gallium-resistant gold. The assembly includes 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 opposite the target container to the substrate holding section, and having a plasma-plated, high-density plasma region formed on the surface of the gallium target on one side of the first direction, where the density of the sputtering gas is higher than that of the periphery. For example, in the DC sputtering apparatus of claim 1, the aforementioned gallium-resistant metal includes molybdenum, copper, or stainless steel. As in the DC sputtering apparatus of claim 1 or 2, the aforementioned target container is formed of a ceramic material. As in the DC sputtering apparatus of claim 3, the aforementioned target container is formed by a ceramic material whose main components are gallium nitride, aluminum nitride, or boron nitride. As in the DC sputtering apparatus of claim 1 or 2, the conductor is disposed separately from the high-density plasma region in a second direction intersecting the first direction. As in the DC sputtering apparatus of claim 1 or 2, the aforementioned magnet portion includes a ring-shaped first permanent magnet, and the aforementioned conductor is disposed separately from the aforementioned first permanent magnet in a second direction intersecting the aforementioned first direction. As in the DC sputtering apparatus of claim 1 or 2, 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. As in claim 7, the DC sputtering apparatus further comprises: a cover portion that covers the opening of the passage portion on one side of the first direction; the other end of the conductor is disposed in the portion of the passage portion covered by the cover portion. The DC sputtering apparatus of claim 1 or 2, wherein the sputtering gas comprises argon. The DC sputtering apparatus of claim 1 or 2 further includes: a reactive gas supply unit that supplies reactive gas; the reactive gas supply unit supplies the reactive gas so that the gallium deposited on the main surface of the substrate reacts with the plasma-plated reactive gas. As in the DC sputtering apparatus of claim 10, the reactive gas contains nitrogen. As in claim 1 or 2, the DC sputtering apparatus wherein the target container has a bottom surface and a side surface that hold the gallium target inside, and the conductor is located on the bottom surface or the side surface and passes through the target container.