Film forming apparatus and film forming method

Abstract

To provide a film deposition apparatus capable of depositing a GaN film at a high productivity, and a film deposition method.SOLUTION: A film deposition apparatus 1 according to an embodiment has a chamber 20 of which internal space can be evacuated, a turntable 31 that is arranged in the chamber 20, holds a work 10, and circularly transports the work 10 in a periphery trajectory, a target 42 composed of a film deposition material containing GaN, and a plasma generator for generating a plasma with a sputtering gas that is introduced between the target and the turntable. The film deposition apparatus has a GaN deposition treatment part 40A that deposits a particle of a film deposition material containing GaN and Ga on the work 10 circularly transported by the turntable 31 by sputtering, and a nitriding treatment part 50 that nitrides the particle of the film deposition material deposited in the GaN deposition treatment part 40A on the work 10 circularly transported by the turntable 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film forming apparatus and a film forming method. [Background technology]

[0002] GaN (Gallium Nitride) is attracting attention as a next-generation device material. For example, devices using GaN include light-emitting devices, power devices, and high-frequency communication devices. Such GaN devices are manufactured by forming GaN films on silicon (Si) wafers, silicon carbide (SiC) wafers, sapphire substrates, and glass substrates. Conventionally, GaN films have been formed using the MO-CVD (metal organic chemical vapor deposition) method. The MO-CVD method is a film formation method in which a material gas containing organic metals is transported by a carrier gas onto a heated substrate, and the material is decomposed and chemically reacted at high temperature, resulting in the deposition of a film through chemical vapor deposition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-103652 Summary of the Invention [Problem to be solved by the invention]

[0004] However, MO-CVD GaN deposition poses several productivity problems. First, gallium (Ga) is liquid at room temperature and pressure. However, a large amount of NH3 gas is required for processing to prevent Ga evaporation and to react Ga with nitrogen (N). This results in inefficient material utilization. Furthermore, handling the source gas is difficult, and maintaining stable equipment conditions is challenging, resulting in low yields. The MO-CVD method requires high-temperature processing at temperatures of around 1,000°C to completely decompose NH3 gas, which necessitates high-power heating equipment and increases costs. Furthermore, hydrogen (H) contained in the processing gas is incorporated into the deposited GaN film during processing, necessitating an extra step called dehydrogenation.

[0005] The present invention has been proposed to solve the above-mentioned problems, and has an object to provide a film formation apparatus and a film formation method that can form a GaN film with high productivity. [Means for solving the problem]

[0006] In order to achieve the above object, the film formation apparatus of this embodiment includes a chamber capable of evacuating the interior thereof, a rotary table provided within the chamber for holding a workpiece and circulating and transporting the workpiece along a circular trajectory, a target made of a film formation material containing GaN, and a plasma generator for generating plasma from a sputtering gas introduced between the target and the rotary table, the GaN film formation processing section depositing particles of the film formation material containing GaN by sputtering on the workpiece circulated and transported by the rotary table, and a nitriding processing section nitriding the particles of the film formation material deposited in the GaN film formation processing section on the workpiece circulated and transported by the rotary table. a target made of a film formation material containing p-type impurities or n-type impurities; a plasma generator that generates plasma from a sputtering gas introduced between the target made of the film formation material containing the p-type impurities or n-type impurities and the turntable; and an impurity addition processing unit that adds n-type impurities or p-type impurities by sputtering to particles of the film formation material containing GaN deposited on the workpiece in the GaN film formation processing unit, wherein the GaN film formation processing unit, the nitriding processing unit, and the impurity addition processing unit are arranged on the circulation transport path, and the turntable transports the workpiece so that GaN film formation, nitriding, and impurity addition are repeated by repeatedly passing the workpiece through the GaN film formation processing unit, the nitriding processing unit, and the impurity addition processing unit in this order, thereby forming a GaN film containing the n-type impurities or the p-type impurities on the workpiece with a predetermined number of layers. do.

[0007] The film formation method of this embodiment is a film formation method in which a workpiece is held by a rotary table and circulated and transported along a circular trajectory in a chamber capable of being evacuated, while the workpiece is formed on the rotary table. The method includes the following steps: a GaN film formation process in which a GaN film formation processing unit having a target made of a film formation material containing GaN and a plasma generator that converts a sputtering gas introduced between the target and the rotary table into plasma deposits particles of the film formation material containing GaN on the workpiece that is circulated and transported by the rotary table; and a nitriding processing unit that nitrides the particles of the film formation material deposited in the GaN film formation processing unit on the workpiece that is circulated and transported by the rotary table. and an impurity addition process in which n-type impurities or p-type impurities are added by sputtering to particles of the GaN-containing film material deposited on the workpiece in the GaN film formation processing section, and the GaN film formation process, the nitriding process, and the impurity addition process are repeated in this order by circulating and transporting the workpiece, thereby forming a GaN film containing the n-type impurity or the p-type impurity with a predetermined number of layers on the workpiece. . [Effects of the Invention]

[0008] According to the embodiments of the present invention, it is possible to provide a film formation apparatus and a film formation method that can form a GaN film with high productivity. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective plan view schematically illustrating a configuration of a film forming apparatus according to an embodiment. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1, showing in detail the internal configuration of the film forming apparatus according to the embodiment of FIG. 1 as viewed from the side. [Figure 3] 3 is a flowchart of a process performed by the film forming apparatus according to the embodiment. [Figure 4] FIG. 10 is a perspective plan view schematically showing a modified example of the embodiment. [Figure 5] FIG. 10 is a perspective plan view schematically showing a modified example of the embodiment. [Figure 6] 1A is a cross-sectional view showing an example of the layer structure of an LED, and FIG. 1B is an enlarged cross-sectional view of a buffer layer. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a film forming apparatus will be described in detail with reference to the drawings. [overview] 1 is an apparatus for forming a GaN (Gallium Nitride) film or an AlN (Aluminum Nitride) film by sputtering on a workpiece 10, which is a film formation target. The workpiece 10 is, for example, a silicon (Si) wafer, a silicon carbide (SiC) wafer, a sapphire substrate, or a glass substrate.

[0011] The film forming apparatus 1 has a chamber 20, a transport unit 30, a film forming processing unit 40, a nitriding processing unit 50, a heating unit 60, a transfer chamber 70, a preheating chamber 80, a cooling chamber 90, and a control device 100. The chamber 20 is a container that can be evacuated. The chamber 20 is cylindrical, and its interior is divided into multiple compartments. The film forming processing unit 40 is separated by a partition unit 22 and is arranged in two fan-shaped compartments. The nitriding processing unit 50 and the heating unit 60 are arranged in the compartments other than the compartment where the film forming processing unit 40 is arranged.

[0012] One section of the film formation processing section 40 is a GaN film formation processing section 40A that uses a material containing GaN as the target 42 to form a GaN film, and the other section is an Al film formation processing section 40B that uses a material containing Al as the target 42 to form an Al film. The workpiece 10 makes multiple revolutions in the circumferential direction within the chamber 20, passing alternately through the GaN film formation processing section 40A and the nitriding processing section 50, and the formation of a GaN film and the nitriding of Ga are alternately repeated on the workpiece 10, thereby growing a GaN film of the desired thickness.

[0013] Furthermore, the workpiece 10 rotates around the chamber 20 in the circumferential direction multiple times, passing alternately through the Al film forming unit 40B and the nitriding unit 50, and the formation of an Al film and the nitriding of Al are alternately repeated on the workpiece 10, thereby growing an AlN film of a desired thickness. In this way, the formation of a GaN film and the formation of an AlN film are repeated, and the GaN film and the AlN film are alternately stacked.

[0014] The reason why the nitriding treatment unit 50 is provided in addition to using a material containing GaN as the target 42 is as follows: Ga has a low melting point and is in a liquid state at room temperature and normal pressure, so it is necessary to make the target 42 contain nitrogen (N) to form a solid target 42. For this reason, it is also possible to simply increase the nitrogen content of the target 42 and form a film by sputtering the target 42 alone.

[0015] Here, to improve the film formation rate, DC discharge sputtering is preferable to RF discharge. However, if the target 42 contains a large amount of nitrogen, the surface becomes an insulator. In such a target 42 with an insulator surface, DC discharge may not occur.

[0016] That is, there is a limit to the amount of nitrogen that can be contained in the GaN target 42, and the nitridation of Ga in the target 42 remains insufficient. That is, the target 42 containing GaN contains Ga atoms that are missing bonds with N (nitrogen) atoms.

[0017] Furthermore, if nitrogen gas is added to the sputtering gas introduced into the film formation processing unit 40 and sputtering is performed, the surface of the target 42 is nitrided, resulting in an insulating surface. Therefore, the GaN film formation processing unit 40A cannot add nitrogen gas to the sputtering gas to compensate for the lack of nitrogen. On the other hand, if the nitrogen content in the formed GaN film is low and nitrogen defects exist, the film's crystallinity will deteriorate and its flatness will be impaired. Therefore, in order to compensate for the lack of nitrogen in the GaN film formed by the GaN film formation processing unit 40A, nitridation is further performed in the nitriding processing unit 50 after film formation by the GaN film formation processing unit 40A.

[0018] [Chamber] 2, the chamber 20 is surrounded by a disk-shaped ceiling 20a, a disk-shaped inner bottom surface 20b, and an annular inner peripheral surface 20c. The partitions 22 are rectangular wall plates arranged radially from the center of the cylindrical shape, and extend from the ceiling 20a toward the inner bottom surface 20b, but do not reach the inner bottom surface 20b. In other words, a cylindrical space is secured on the inner bottom surface 20b side.

[0019] A turntable 31 for transporting the workpiece 10 is disposed in this cylindrical space. The lower end of the partition 22 faces the surface of the turntable 31 on which the workpiece 10 is placed, with a gap therebetween through which the workpiece 10 placed on the turntable 31 passes. The partition 22 separates a processing space 41 in which the workpiece 10 is processed by the film-forming processing unit 40. A processing space 59 is also separated by a cylindrical body 51 (described later) of the nitriding processing unit 50. That is, the film-forming processing unit 40 and the nitriding processing unit 50 each have processing spaces 41, 59 that are smaller than the chamber 20 and are separated from each other. The partition 22 can prevent the sputtering gas G1 of the film-forming processing unit 40 from diffusing into the chamber 20. The cylindrical body 51 of the nitriding processing unit 50 can also prevent the process gas G2 from diffusing into the chamber 20.

[0020] Furthermore, as will be described later, plasma is generated in the processing spaces 41, 59 in the film forming unit 40 and the nitriding unit 50, and the pressure can be easily adjusted to stabilize the plasma discharge by adjusting the pressure in the processing spaces 41, 59, which are partitioned into spaces smaller than the chamber 20. Therefore, if the above-described effect can be obtained, it is sufficient to have at least two partitions 22 sandwiching the film forming unit 40 in a plan view.

[0021] The chamber 20 is provided with an exhaust port 21. The exhaust port 21 is connected to an exhaust unit 23. The exhaust unit 23 has piping and a pump, a valve, etc. (not shown). By exhausting air through the exhaust port 21 by the exhaust unit 23, the inside of the chamber 20 can be depressurized and made into a vacuum. The exhaust unit 23 is configured to have a vacuum level of, for example, 10 to 200°C in order to keep the oxygen concentration low. -4 Evacuate until the pressure reaches Pa.

[0022] [Transport section] The transport unit 30 has a rotary table 31, a motor 32, and a holding unit 33, and circulates and transports the workpiece 10 along a transport path L, which is a circular trajectory. The rotary table 31 has a disk shape and is wide enough not to come into contact with the inner peripheral surface 20c. The motor 32 continuously rotates the rotary table 31 at a predetermined rotation speed around the center of the circle as the rotation axis. The rotary table 31 rotates at a speed of, for example, 1 to 150 rpm.

[0023] The holding units 33 are grooves, holes, protrusions, jigs, holders, etc., arranged at evenly spaced positions on the upper surface of the turntable 31, and hold a tray 34 on which the workpieces 10 are placed by a mechanical chuck or an adhesive chuck. The workpieces 10 are arranged, for example, in a matrix on the tray 34, and six holding units 33 are arranged on the turntable 31 at 60° intervals. In other words, the film forming apparatus 1 can simultaneously form films on multiple workpieces 10 held by multiple holding units 33, resulting in extremely high productivity. Note that the tray 34 may be omitted, and the workpieces 10 may be placed directly on the upper surface of the turntable 31.

[0024] [Film forming processing section] The film forming processing unit 40 generates plasma and exposes a target 42 made of a film forming material to the plasma. As a result, particles of the film forming material (hereinafter referred to as sputter particles) are knocked out by ions contained in the plasma colliding with the target 42, and the particles are deposited on the workpiece 10 to form a film. As shown in Fig. 2, the film forming processing unit 40 includes a sputtering source made up of the target 42, a backing plate 43, and an electrode 44, and a plasma generator made up of a power supply unit 46 and a sputtering gas introduction unit 49.

[0025] The target 42 is a plate-like member made of a film-forming material that will be deposited on the workpiece 10 to form a film. The film-forming material that constitutes the target 42 in the GaN film-forming processing unit 40A of this embodiment is a material containing Ga and GaN, and the target 42 serves as a supply source of sputtered particles containing Ga atoms that are deposited on the workpiece 10. Because the nitrogen content is limited as described above, the target 42 contains GaN and incomplete GaN that is deficient in nitrogen, i.e., Ga atoms that are missing bonds with N (nitrogen).

[0026] The film forming material constituting the target 42 in the Al film forming unit 40B is a material containing Al, and the target 42 serves as a supply source of sputtering particles containing Al atoms to be deposited on the workpiece 10. Note that the sputtering target 42 may contain elements other than Ga, Al, and N (nitrogen) as long as it is capable of supplying sputtering particles containing Ga atoms and sputtering particles containing Al atoms.

[0027] The target 42 is provided at a distance on the transport path L of the workpiece 10 placed on the turntable 31. The surface of the target 42 is supported on the ceiling 20a of the chamber 20 so as to face the workpiece 10 placed on the turntable 31. For example, three targets 42 are provided. The three targets 42 are provided at positions aligned on the vertices of a triangle in a plan view.

[0028] The backing plate 43 is a support member that holds the targets 42. This backing plate 43 holds each target 42 individually. The electrode 44 is a conductive member that applies power to each target 42 individually from outside the chamber 20, and is electrically connected to the targets 42. The power applied to each target 42 can be changed individually. In addition, the sputtering source is appropriately equipped with a magnet, a cooling mechanism, etc. as needed.

[0029] The power supply unit 46 is, for example, a DC power supply that applies a high voltage, and is electrically connected to the electrode 44. The power supply unit 46 applies power to the target 42 through the electrode 44. The rotary table 31 has the same potential as the grounded chamber 20, and applying a high voltage to the target 42 generates a potential difference.

[0030] 2, sputtering gas introduction unit 49 introduces sputtering gas G1 into chamber 20. Sputtering gas introduction unit 49 has a supply source of sputtering gas G1 such as a cylinder (not shown), piping 48, and gas introduction port 47. Pipe 48 is connected to the supply source of sputtering gas G1, airtightly penetrates chamber 20, and extends into the interior of chamber 20, with its end opening as gas introduction port 47. Sputtering gas introduction unit 49 of this embodiment introduces sputtering gas G1 into processing space 41 so that the pressure in processing space 41 is 0.3 Pa or less and 0.1 Pa or more.

[0031] Gas inlet 47 opens between turntable 31 and target 42, and introduces sputtering gas G1 for film formation into processing space 41 formed between turntable 31 and target 42. A rare gas can be used as sputtering gas G1, and argon (Ar) gas is preferable. Sputtering gas G1 is a gas that does not contain nitrogen (N), and can be argon (Ar) gas alone.

[0032] In this film formation processing unit 40, sputtering gas G1 is introduced from sputtering gas inlet 49, and when power supply 46 applies a high voltage to target 42 via electrode 44, sputtering gas G1 introduced into processing space 41 formed between turntable 31 and target 42 is converted into plasma, generating active species such as ions. The ions in the plasma collide with target 42, thereby ejecting sputtered particles. In GaN film formation processing unit 40A, sputtering particles collide with target 42 made of a material containing Ga and GaN, thereby ejecting sputtered particles containing Ga atoms. In Al film formation processing unit 40B, sputtering particles collide with target 42 made of a material containing Al, thereby ejecting sputtered particles containing Al atoms.

[0033] Furthermore, the workpiece 10, which is circulated and transported by the rotary table 31, passes through this processing space 41. The ejected sputtered particles are deposited on the workpiece 10 as the workpiece 10 passes through the processing space 41, and a film containing Ga atoms and a film containing Al atoms are formed on the workpiece 10. The workpiece 10 is circulated and transported by the rotary table 31, and is subjected to film formation processing by repeatedly passing through this processing space 41. Note that the formation of a GaN film containing Ga and the formation of an AlN film containing Al are not performed in parallel, but are performed by forming one film and then forming the other film.

[0034] [Nitriding processing section] The nitriding unit 50 generates an inductively coupled plasma in a processing space 59 into which a process gas G2 containing nitrogen gas has been introduced. That is, the nitriding unit 50 converts nitrogen gas into plasma to generate chemical species. The nitrogen atoms contained in the generated chemical species collide with the film containing Ga atoms and the film containing Al atoms formed on the workpiece 10 by the film forming unit 40, and bond with Ga atoms that are missing bonds with nitrogen in the film containing Ga atoms and Al atoms in the film containing Al atoms. This allows for the production of GaN films and AlN films that are free of nitrogen defects.

[0035] As shown in FIG. 2, the nitriding treatment unit 50 has a plasma generator that is composed of a cylindrical body 51, a window member 52, an antenna 53, an RF power supply 54, a matching box 55, and a process gas introduction unit 58.

[0036] The cylindrical body 51 is a member that covers the periphery of the processing space 59. As shown in Figures 1 and 2, the cylindrical body 51 is a tube with a rounded rectangular cross section and has an opening. The cylindrical body 51 is fitted into the ceiling 20a of the chamber 20 so that the opening faces away from the turntable 31 and protrudes into the internal space of the chamber 20. The cylindrical body 51 is made of the same material as the turntable 31.

[0037] The window member 52 is a flat plate made of a dielectric material such as quartz, having a shape similar to the horizontal cross section of the cylindrical body 51. The window member 52 is provided to close the opening of the cylindrical body 51, and separates the inside of the cylindrical body 51 from a processing space 59 into which a process gas G2 containing nitrogen gas is introduced in the chamber 20. The window member 52 is required to suppress oxidation caused by oxygen flowing into the processing space 59. For example, the required oxygen concentration is 10 19 (atom / cm 3 ) or less, which is very low. To address this, a protective coating is applied to the surface of the window member 52. For example, by coating the surface of the window member 52 with Y2O3 (yttrium oxide), it is possible to suppress wear of the window member 52 by plasma while also suppressing oxygen release from the surface of the window member 52, thereby maintaining a low oxygen concentration.

[0038] In the nitriding treatment unit 50, a treatment space 59 is formed between the turntable 31 and the inside of the cylindrical body 51. The workpieces 10, which are circulated and transported by the turntable 31, pass through this treatment space 59 repeatedly, thereby performing the nitriding treatment. The window member 52 may be made of a dielectric material such as alumina, or a semiconductor material such as silicon.

[0039] The antenna 53 is a conductor wound into a coil and is disposed in the internal space of the cylindrical body 51, which is isolated from the processing space 59 in the chamber 20 by the window member 52. An electric field is generated by passing an alternating current through the antenna 53. The antenna 53 is preferably disposed near the window member 52 so that the electric field generated by the antenna 53 is efficiently introduced into the processing space 59 through the window member 52. An RF power supply 54 that applies a high-frequency voltage is connected to the antenna 53. A matching box 55, which is a matching circuit, is connected in series to the output side of the RF power supply 54. The matching box 55 stabilizes the plasma discharge by matching the impedances on the input and output sides.

[0040] 2, the process gas introduction unit 58 introduces a process gas G2 containing nitrogen gas into the processing space 59. The process gas introduction unit 58 has a supply source of the process gas G2 such as a cylinder (not shown), a pipe 57, and a gas introduction port 56. The pipe 57 is connected to the supply source of the process gas G2, penetrates the chamber 20 while airtightly sealing it, and extends into the interior of the chamber 20, with its end opening as the gas introduction port 56.

[0041] The gas inlet 56 opens into a processing space 59 between the window member 52 and the rotary table 31, and introduces a process gas G2. A rare gas can be used as the process gas G2, and argon gas or the like is preferable.

[0042] In the nitriding treatment unit 50, a high-frequency voltage is applied to the antenna 53 from the RF power supply 54. This causes a high-frequency current to flow through the antenna 53, generating an electric field due to electromagnetic induction. The electric field is generated in the treatment space 59 through the window member 52, generating an inductively coupled plasma in the process gas G2. At this time, nitrogen chemical species containing nitrogen atoms are generated, which collide with the film containing Ga atoms and the film containing Al atoms on the workpiece 10, thereby bonding with the Ga atoms and Al atoms. As a result, the nitrogen content of the film on the workpiece 10 can be increased, and a GaN film or an AlN film without nitrogen defects can be formed.

[0043] [Heating section] The heating unit 60 heats the workpiece 10 that is circulated and transported by the turntable 31 within the chamber 20. The heating unit 60 has a heat source provided at a position facing the transport path L of the workpiece 10 on the turntable 31. The heat source is, for example, a halogen lamp. The heating temperature is preferably set to a temperature at which the workpiece 10 is heated to, for example, about 500°C.

[0044] [Transfer room] The transfer chamber 70 is a container for loading and unloading the workpieces 10 into and from the chamber 20 via a gate valve. As shown in FIG. 1 , the transfer chamber 70 has an internal space in which the workpieces 10 are accommodated before being loaded into the chamber 20. The transfer chamber 70 is connected to the chamber 20 via a gate valve GV1. Although not shown, a transport means is provided in the internal space of the transfer chamber 70 for loading and unloading trays 34 carrying the workpieces 10 to and from the chamber 20. The transfer chamber 70 is depressurized by an exhaust means such as a vacuum pump (not shown), and while the vacuum of the chamber 20 is maintained by the transport means, the trays 34 carrying unprocessed workpieces 10 are loaded into the chamber 20, and the trays 34 carrying processed workpieces 10 are unloaded from the chamber 20.

[0045] A load lock unit 71 is connected to the transfer chamber 70 via a gate valve GV2. The load lock unit 71 is a device that, while maintaining the vacuum of the transfer chamber 70, loads trays 34 carrying unprocessed workpieces 10 from the outside into the transfer chamber 70 by a transport means not shown, and unloads trays 34 carrying processed workpieces 10 from the transfer chamber 70. The load lock unit 71 switches between a vacuum state in which the pressure is reduced by an exhaust means such as a vacuum pump not shown, and an open-to-air state in which the vacuum is broken.

[0046] [Preheating chamber] The preheating chamber 80 heats the workpiece 10 before it is carried into the chamber 20. The preheating chamber 80 is equipped with a container connected to the transfer chamber 70 and has a heat source that heats the workpiece 10 before it is carried into the transfer chamber 70. The heat source may be, for example, a heater or a heat lamp. The preheating temperature is preferably a temperature at which the workpiece 10 is heated to about 300°C. The tray 34 is transported between the preheating chamber 80 and the transfer chamber 70 by a transport means (not shown).

[0047] [Cooling room] The cooling chamber 90 cools the workpieces 10 transported from the chamber 20. The cooling chamber 90 is equipped with a container connected to the transfer chamber 70 and has a cooling means for cooling the workpieces 10 loaded on the trays 34 transported from the transfer chamber 70. For example, a spraying unit for spraying cooling gas can be used as the cooling gas. For example, Ar gas from the supply source of the sputtering gas G1 can be used. The cooling temperature is preferably a temperature at which the workpieces can be transported in the atmosphere, for example, 30°C. The trays 34 loaded with the processed workpieces 10 from the transfer chamber 70 are transported into the cooling chamber 90 by a transport means (not shown).

[0048] [Control device] The control device 100 controls various elements that make up the film forming apparatus 1, such as the exhaust unit 23, the sputtering gas introduction unit 49, the process gas introduction unit 58, the power supply unit 46, the RF power supply 54, the transport unit 30, the heating unit 60, the transfer chamber 70, the load lock unit 71, the preheating chamber 80, and the cooling chamber 90. The control device 100 is a processing device that includes a PLC (Programmable Logic Controller) and a CPU (Central Processing Unit), and stores a program that describes the control contents.

[0049] Specific controlled items include the initial exhaust pressure of the film forming apparatus 1, the power applied to the target 42 and the antenna 53, the flow rates of the sputtering gas G1 and the process gas G2, the introduction time and exhaust time, the film forming time, and the rotation speed of the motor 32. This allows the control device 100 to accommodate a wide variety of film forming specifications. The control device 100 also controls the heating temperature and heating time of the heating unit 60, the heating temperature and heating time of the preheating chamber 80, the cooling temperature and cooling time of the cooling chamber 90, etc.

[0050] [Operation] Next, the operation of the film formation apparatus 1 controlled by the control device 100 will be described. Note that a film formation method using the film formation apparatus 1, as described below, is also an aspect of the present invention. FIG. 3 is a flowchart of a film formation process using the film formation apparatus 1 of this embodiment. This film formation process involves alternately stacking AlN and GaN films on a workpiece 10, followed by forming a GaN layer. Because silicon wafers and sapphire substrates have different crystal lattices from GaN, directly forming a GaN film on them can result in a problem of reduced GaN crystallinity. To resolve this crystal lattice mismatch, a buffer layer is formed by alternately stacking AlN and GaN films, and then a GaN layer is formed on this buffer layer. This method can be used, for example, to form a GaN layer on a silicon wafer via a buffer layer in the manufacture of horizontal MOSFETs and LEDs.

[0051] First, the chamber 20 is evacuated through the exhaust port 21 by the exhaust unit 23, and is constantly depressurized to a predetermined pressure. Furthermore, as the exhaust is initiated, the heating unit 60 begins heating, and the turntable 31 begins rotating, heating the turntable 31 as it passes through the heating unit 60. The chamber 20 is heated by radiation from the heated turntable 31. Heating along with the exhaust promotes the desorption of residual gases, such as water molecules and oxygen molecules, in the chamber 20. This reduces the likelihood of residual gases being mixed in as impurities during film formation, improving the crystallinity of the film. After a gas analyzer such as Q-Mass detects that the oxygen concentration in the chamber 20 has fallen below a predetermined value, the heating unit 60 stops heating and the rotation of the turntable 31 stops. Furthermore, in the preheating chamber 80, the workpieces 10 placed on the tray 34 are preheated to approximately 300°C (step S01).

[0052] The trays 34 carrying the preheated workpieces 10 are carried into the transfer chamber 70 by the transport means, and are sequentially carried into the chamber 20 via the gate valve GV1 (step S02). In this step S02, the turntable 31 moves the empty holders 33 sequentially to the loading position from the transfer chamber 70. The holders 33 individually hold the trays 34 carried in by the transport means. In this way, all of the trays 34 carrying the workpieces 10 are placed on the turntable 31.

[0053] The heating unit 60 starts heating again, and the turntable 31 with the workpiece 10 placed on it starts rotating, thereby heating the workpiece 10 (step S03). After a predetermined time, obtained in advance through simulation or experiment, has elapsed, the workpiece 10 is heated to about 500°C. During heating, the turntable 31 is rotated at a relatively high speed of about 100 rpm in order to heat the workpiece more uniformly.

[0054] Then, a buffer layer is formed by alternately repeating the formation of an AlN film by the Al film forming unit 40B and the nitriding unit 50 and the formation of a GaN film by the GaN film forming unit 40A and the nitriding unit 50. First, an AlN film is formed on the workpiece 10 by the Al film forming unit 40B and the nitriding unit 50 (step S04). That is, the sputtering gas inlet 49 supplies a sputtering gas G1 through the gas inlet 47. The sputtering gas G1 is supplied to the periphery of the target 42 made of Al. The power supply 46 applies a voltage to the target 42. This converts the sputtering gas G1 into plasma. Ions generated by the plasma collide with the target 42 and eject sputter particles containing Al atoms.

[0055] When the untreated workpiece 10 passes through the Al film forming unit 40B, a thin film is formed on the surface of the workpiece 10, where sputtered particles containing Al atoms are deposited. In this embodiment, each time the workpiece 10 passes through the Al film forming unit 40B, a film thickness that can contain 1 to 2 Al atoms in the thickness direction can be deposited.

[0056] In this way, the workpiece 10 that has passed through the Al film forming treatment unit 40B due to the rotation of the turntable 31 passes through the nitriding treatment unit 50, and in the process, the Al atoms of the thin film are nitrided. That is, a process gas inlet 58 supplies a process gas G2 containing nitrogen gas through a gas inlet 56. The process gas G2 containing nitrogen gas is supplied to a treatment space 59 sandwiched between a window member 52 and the turntable 31. An RF power supply 54 applies a high-frequency voltage to an antenna 53.

[0057] An electric field generated by the antenna 53 through which a high-frequency current flows due to the application of a high-frequency voltage is generated in the processing space 59 via the window member 52. This electric field excites the process gas G2 containing nitrogen gas supplied to this space, generating plasma. The nitrogen chemical species generated by the plasma collide with the thin film on the workpiece 10 and bond with Al atoms, forming a sufficiently nitrided AlN film.

[0058] The turntable 31 continues to rotate until an AlN film of a predetermined thickness is formed on the workpiece 10, that is, until a predetermined time obtained in advance through simulation, experiment, or the like has elapsed. In other words, the workpiece 10 continues to circulate between the film formation unit 40 and the nitriding unit 50 until an AlN film of a predetermined thickness is formed. Note that, since nitriding is preferably performed each time Al is deposited to an atomic-level film thickness, the rotation speed of the turntable 31 is set to a relatively slow speed of 50 to 60 rpm in order to balance film formation and nitriding.

[0059] After a predetermined time has elapsed, the operation of the Al film forming unit 40B is stopped. Specifically, the application of voltage to the target 42 by the power supply unit 46 is stopped.

[0060] Next, a GaN film is formed on the workpiece 10 in the GaN film forming unit 40A and the nitriding unit 50 (step S05). That is, the sputtering gas G1 is turned into plasma by supplying the sputtering gas G1 to the periphery of the target 42 by the sputtering gas inlet unit 49 and applying a voltage to the target 42 by the power supply unit 46. Ions generated by the plasma collide with the target 42 and eject sputtered particles containing Ga atoms.

[0061] As a result, a thin film in which sputtered particles containing Ga atoms are deposited on the surface of the AlN film. In this embodiment, a film having a thickness that can contain 1 to 2 Ga atoms can be deposited each time the film passes through the film-forming unit 40.

[0062] In this way, the workpiece 10 that has passed through the GaN film forming unit 40A due to the rotation of the turntable 31 passes through the nitriding unit 50, during which the Ga atoms in the thin film are nitrided. That is, as described above, nitrogen chemical species generated by the plasma collide with the thin film on the workpiece 10, and bond with Ga atoms that are missing bonds with nitrogen, forming a GaN film without nitrogen defects.

[0063] When the time required for a GaN film of a predetermined thickness to be formed on the workpiece 10, which is determined by simulation or experiment, has elapsed, the turntable 31 first stops the operation of the film formation processing unit 40. That is, when the predetermined time has elapsed, the operation of the GaN film formation processing unit 40A is stopped. Specifically, the application of voltage to the target 42 by the power supply unit 46 is stopped. The formation of the AlN film and the GaN film as described above is repeated until the predetermined number of layers is reached (step S06 No). When the predetermined number of layers is reached (step S06 Yes), the formation of the buffer layer is terminated.

[0064] Furthermore, a GaN layer is formed on the buffer layer (step S07). The formation of this GaN layer is performed in the same manner as the formation of the GaN film on the buffer layer. However, the film formation is performed for a time period that will allow the GaN layer to reach a predetermined thickness.

[0065] After the buffer layer and GaN layer are formed as described above, the operation of the GaN film forming unit 40A is stopped as described above, and then the operation of the nitriding unit 50 is stopped (step S09). Specifically, the supply of high-frequency power from the RF power supply 54 to the antenna 53 is stopped. Then, the rotation of the turntable 31 is stopped, and the tray 34 on which the film-formed workpieces 10 are placed is carried into the cooling chamber 90 via the transfer chamber 70 by the conveying means. After the workpieces 10 are cooled to a predetermined temperature, they are removed from the load lock unit 71 (step S09).

[0066] In the above description, the nitriding unit 50 is operated continuously during the formation of the buffer layer (steps S04 to S06), but the operation of the nitriding unit 50 may be stopped after each step S04 to S06 is completed. In this case, the operation of the nitriding unit 50 is stopped after the operation of the Al film formation unit 40B and the GaN film formation unit 40A is stopped. This allows the surface of the film formed on the workpiece 10 to be sufficiently nitrided, and AlN films and GaN films without nitrogen defects can be obtained.

[0067] [effect] (1) The film forming apparatus 1 according to this embodiment includes a chamber 20 capable of evacuating the interior thereof, a rotary table 31 provided within the chamber 20, which holds the workpiece 10 and circulates the workpiece 10 along a circular path, a target 42 made of a film forming material containing GaN, a plasma generator which converts a sputtering gas G1 introduced between the target 42 and the rotary table 31 into plasma, a GaN film forming processing unit 40A which deposits particles of the film forming material containing GaN by sputtering onto the workpiece 10 which is circulated and transported by the rotary table 31, and a nitriding processing unit 50 which nitrides the particles of the film forming material deposited in the GaN film forming processing unit 40A onto the workpiece 10 which is circulated and transported by the rotary table 31.

[0068] The film formation method of this embodiment is a film formation method in which a film is formed on a workpiece 10 while the workpiece 10 is held by a turntable 31 and circulated and transported along a circular trajectory in a chamber 20 whose interior can be evacuated. The method includes a GaN film formation process in which a GaN film formation processing unit 40A having a target 42 made of a film formation material containing GaN and a plasma generator that converts a sputtering gas G1 introduced between the target 42 and the turntable 31 into plasma, deposits particles of the film formation material containing GaN by sputtering on the workpiece 10 that is circulated and transported by the turntable 31, and a nitriding process in which a nitriding processing unit 50 nitrides the particles of the film formation material deposited in the GaN film formation processing unit 40A on the workpiece 10 that is circulated and transported by the turntable 31.

[0069] In this embodiment, GaN films can be formed with high productivity by sputtering the workpiece 10 circulated by the rotary table 31 in the chamber 20. Unlike the MOCVD method, a large amount of NH3 gas is not required. Instead, sputtering gas G1 and process gas G2 are flowed into a limited area of ​​the vacuum chamber 20, depositing and nitriding the material on the target 42 to an atomic-level thickness. This results in high material utilization efficiency. Furthermore, since no reactive gas containing hydrogen (H) is used, extra processes such as dehydrogenation are unnecessary. Furthermore, since only an easily handled rare gas is introduced into the chamber 20, the equipment condition can be easily maintained stably, resulting in high yields. The heating temperature is relatively low, around 500°C, and the power required for the heating device is low. Because the entire process of forming the buffer layer and GaN layer is completed within the chamber 20, film formation can be performed in a uniform, low-oxygen environment without the need to transfer the chamber between chambers to form other layers during the process.

[0070] Furthermore, because the process involves repeatedly stacking and nitriding film-forming materials to atomic-level thicknesses, it is possible to form films with high crystallinity and minimal surface irregularities despite the shorter film-forming time compared to MO-CVD methods.

[0071] Here, the results of evaluation of films formed under the following film forming conditions are shown. Workpiece: Si(111) substrate Rotary table rotation speed: 60 rpm High frequency power applied to antenna (nitriding treatment part): 4000W DC power applied to sputtering source: GaN film forming section: 800 to 1500 W, Al film forming section: 2000 to 3500 W (for a film forming section equipped with two sputtering sources, the value of the power applied to each sputtering source) Deposition rate: GaN layer 0.28nm / sec, AlN layer 0.43nm / sec Ar gas flow rate in the deposition process section: GaN deposition process section: 80 sccm, Al deposition process section: 45 sccm Nitriding treatment N2 gas flow rate: 30sccm In the above embodiment, heating is not performed during film formation.

[0072] X-ray diffraction analysis was performed on the following films deposited on the workpieces: a 3μm AlN film (No. 1), a 3μm GaN film (No. 2), a 30-layer stack of 5nm AlN film / 5nm GaN film (No. 3), and a stack of 30 layers of 5nm AlN film / 5nm GaN film with a 3μm GaN film stacked on top (No. 4). The results showed that the half-width (°) of the rocking curve obtained by 2θ / ω scanning of the (002) plane of the film surface was 0.246 for No. 1, 0.182 for No. 2, 0.178 for No. 3, and 0.197 for No. 4.

[0073] Generally, the smaller the full width at half maximum, the less the variation in crystal orientation and the higher the crystallinity. In this embodiment, it is possible to form a highly crystalline film with a full width at half maximum (2θ / ω) of 0.2° or less. Furthermore, the thickness of a GaN buffer layer used in GaN-based devices is generally considered to be 3 to 10 μm, but the film formation rate of the MO-CVD method is said to be several μm / h. In this embodiment, the film formation rate is similar, but the hydrogen desorption step can be omitted, thereby shortening the film formation time compared to the MO-CVD method. Furthermore, a highly crystalline film can be obtained even at a low temperature compared to the MO-CVD method.

[0074] Furthermore, if the solid target 42 contains a large amount of nitrogen, the surface becomes an insulator, which prevents the target 42 from containing a large amount of nitrogen and results in the formation of Ga atoms with nitrogen-bond defects. Sputtering using such a target 42 results in the formation of a GaN film with nitrogen defects. However, in this embodiment, by providing a nitriding unit 50 separate from the GaN film-forming unit 40A, even if the target 42 contains Ga atoms with nitrogen-bond defects, the nitriding unit 50 can ultimately increase the nitrogen content and produce a GaN film without nitrogen defects. Furthermore, the GaN film-forming unit 40A does not use nitrogen gas, but instead uses argon as the sputtering gas G1, and the particles of the film-forming material deposited on the workpiece W can be nitrided in the nitriding unit 50, which is separate from the GaN film-forming unit 40A. Therefore, the surface of the target 42 does not become an insulator, and the film-forming rate can be improved using DC discharge.

[0075] (2) The film forming apparatus 1 has a target 42 made of a film forming material containing Al, and an Al film forming processing unit 40B that deposits particles of the film forming material containing Al by sputtering on the workpiece 10 that is circulated and transported by the rotary table 31, and the nitriding processing unit 50 nitrides the particles of the film forming material deposited in the Al film forming processing unit 40B on the workpiece 10 that is circulated and transported by the rotary table 31.

[0076] Therefore, for example, when using a workpiece 10 such as silicon, which has a crystal lattice different from that of GaN, a decrease in the crystallinity of GaN can be prevented by forming a buffer layer, which is a film formed by alternately stacking GaN films and AlN films, using the GaN film forming processing unit 40A, the Al film forming processing unit 40B, and the nitriding processing unit 50.

[0077] Furthermore, since the GaN layer can be formed without exposure to the atmosphere after the buffer layer is formed, deterioration of the outermost surface of the buffer layer is suppressed, and deterioration of the GaN layer further formed on the buffer layer can be prevented. Furthermore, it is no longer necessary to move the buffer layer to an environment separate from the buffer layer formation environment for the formation of the GaN layer, which reduces transportation time and eliminates the need to provide a separate space with an adjusted oxygen concentration, etc.

[0078] Furthermore, in the Al film forming unit 40B, the sputtering gas G1 is argon gas alone, without using nitrogen gas, and particles of the film forming material deposited on the workpiece W can be nitrided in a nitriding unit 50 separate from the Al film forming unit 40B. Therefore, the surface of the target 42 does not become an insulator, and the film forming rate can be improved by using DC discharge.

[0079] (3) The film forming apparatus 1 has a heating section 60 that heats the workpiece 10 that is circulated and transported by the turntable 31. This makes it possible to form a film with even better crystallinity.

[0080] (4) The film forming apparatus 1 further includes a preheating chamber 80 that heats the workpiece 10 before it is loaded into the chamber 20. By preheating the workpiece 10 in the preheating chamber 80, the heating time by the heating unit 60 can be shortened, thereby increasing productivity.

[0081] [Variations] (1) In the above embodiment, as shown in FIG. 4, an impurity addition unit may be provided to add n-type or p-type impurities (dopants) to the deposited GaN film. In this case, the GaN film formation unit, nitriding unit, and impurity addition unit are arranged in this order on the circulatory transport path. The impurity addition unit has a configuration similar to that of the film formation units 40A and 40B. More specifically, the impurity addition unit has a target made of a film formation material containing n-type or p-type impurities and a plasma generator, and can sputter the target to add particles (sputtered particles) of the film formation material containing impurity ions to the film deposited on the workpiece 10. For example, the impurity addition unit may be a Mg film formation unit 40C having a target 42 made of a film formation material containing Mg, or a Si film formation unit 40D having a target 42 made of a film formation material containing Si. The Mg film formation unit 40C and the Si film formation unit 40D have a configuration similar to that of the GaN film formation unit 40A, except for the material of the target 42. That is, the Mg film forming unit 40C and the Si film forming unit 40D are provided with a sputtering source composed of a target 42, a backing plate 43 and an electrode 44, and a plasma generator composed of a power supply unit 46 and a sputtering gas inlet unit 49.

[0082] In this embodiment, during the formation of the GaN film, a layer including a p-channel (p-type semiconductor) in which Mg ions are added to the GaN layer can be formed by operating Mg film formation processor 40C together with GaN film formation processor 40A and nitriding processor 50. Furthermore, during the formation of the GaN film, a layer including an n-channel (n-type semiconductor) in which Si ions are added to the GaN layer can be formed by operating Si film formation processor 40D together with GaN film formation processor 40A and nitriding processor 50.

[0083] Conventionally, to form n-channel and p-channel ions, Mg or Si ions are implanted into the GaN film using an ion implanter such as an ion beam implanter, followed by heat treatment. However, with this method, ions are implanted into a film that has already reached a predetermined thickness, so the implantation depth and implantation amount (dose) may differ from the designed values, making control difficult. According to this embodiment, deposition of the GaN film and the addition of Si ions or Mg ions are alternately repeated until the GaN film reaches the predetermined thickness. This makes it easy to control the implantation depth and implantation amount of Mg ions or Si ions according to the thickness of the GaN layer formed per rotation by changing the power applied to the target 42 and the rotation speed of the turntable 31.

[0084] Furthermore, a series of film formation processes for the buffer layer, GaN layer, layer including an n-channel, and layer including a p-channel can be performed within one chamber 20. This eliminates the need to move the substrate to an environment separate from the GaN layer formation environment for the formation of the n-channel and p-channel, reducing transport time and eliminating the need to provide a separate space with an adjusted oxygen concentration.

[0085] (2) In addition to the above embodiment, as shown in Fig. 5, the film forming processing unit 40 may include an InN film forming processing unit 40E having a target 42 made of a film forming material containing InN. Since indium (In) has a low melting point, an InN target is actually used to which nitrogen (N) is added in order to obtain a solid target 42. As described above, the InN target contains In atoms that are insufficiently bonded to nitrogen.

[0086] In this embodiment, an InGaN film can be formed by operating the InN film forming unit 40E together with the GaN film forming unit 40A and the nitriding unit 50 during GaN film formation. This InGaN film functions as the light-emitting layer 14 of the LED, as shown in FIG. 6(A). FIG. 6(A) shows the LED's layered structure, in which a buffer layer 11, a GaN layer 12 including an n-channel, the buffer layer 11, a GaN layer 13 including a p-channel, a light-emitting layer 14, and a transparent conductive film 15 are stacked on a silicon workpiece 10. The transparent conductive film 15 is an ITO (indium tin oxide) film. Note that electrodes are not shown. FIG. 6(B) also shows the buffer layer 11.

[0087] In this embodiment, the LED can be fabricated in a single chamber 20, including buffer layer 11, GaN layer 12 including an n-channel, buffer layer 11, GaN layer 13 including a p-channel, and light-emitting layer 14. This eliminates the need to transfer the LED to an environment separate from the GaN layer fabrication environment for light-emitting layer 14, thereby reducing transport time. It also eliminates the need to provide a separate space with an adjusted oxygen concentration, etc. Furthermore, the color of light-emitting layer 14 can be changed by its thickness. This embodiment facilitates thickness control, making it easy to fabricate light-emitting layers 14 of different colors.

[0088] (3) Different types of power supplies may be used in the film formation units for forming films of different materials. For example, one film formation unit may be a DC power supply, while the other may be a pulsed power supply with a pulse switch. In this case, when adding Mg ions, the GaN film formation unit 40A may be a DC power supply, and the Mg film formation unit 40C may be a pulsed power supply. Alternatively, when adding Si ions, the GaN film formation unit 40A may be a DC power supply, and the Si film formation unit 40D may be a pulsed power supply. In particular, when performing HiPIMS (High Power Impulse Magnetron Sputtering), setting the pulse width and power to apply a large amount of pulsed power in a short period of time generates high-density plasma, dramatically increasing the ionization rate of sputtered particles and enabling more efficient ion implantation.

[0089] Alternatively, the power supplies used in the film forming unit for forming films of the same type of material may be a combination of different types of power supplies, which may be switched at a predetermined timing. For example, a DC power supply and a pulsed power supply equipped with a pulse switch may be combined and switched at a predetermined timing. In this case, when forming a GaN film, the pulsed power supply may be used only for the initial layer in contact with the substrate or other types of film, and after a predetermined film thickness has been formed, the film may be formed using the DC power supply.

[0090] [Other embodiments] Although the embodiments and modifications of each part of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These novel embodiments described above can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and modifications are included within the scope and spirit of the invention, and are also included in the invention described in the claims.

[0091] The type and number of film-forming units 40 and the number of nitriding units 50 provided in the chamber 20 are not limited to the above. The film-forming apparatus 1 may be configured with only the GaN film-forming unit 40A as the film-forming unit 40. Furthermore, in addition to the above-described film-forming unit 40, a film-forming unit 40 using a different target material, a film-forming unit using the same target material, or a nitriding unit 50 may be added. For example, a film-forming unit 40 having a target 42 containing indium oxide and tin oxide, which are ITO film-forming materials, may be added to form an ITO film within the chamber 20. In this case, oxygen gas may be introduced into the nitriding unit 50 instead of nitrogen gas to prevent oxidation of the ITO film. Alternatively, the GaN film-forming unit 40A, the Al film-forming unit 40B, and the nitriding unit 50 may be operated simultaneously to form an AlGaN (Aluminum Gallium Nitride) film containing Ga, Al, and N.

[0092] The n-type impurities or p-type impurities added in the impurity adding unit are not limited to those in the above-described embodiment. For example, n-type impurities may also be Ge or Sn. In this case, the film forming material constituting the target provided in the impurity adding unit may be a film forming material containing Ge or Sn instead of Si. [Explanation of symbols]

[0093] 1 Film deposition equipment 10 Work 11 Buffer layer 12 GaN layers 13 GaN layer 14 Light-emitting layer 15 Transparent conductive film 20 Chamber 20a Ceiling 20b Inner bottom surface 20c Inner surface 21 Exhaust port 22 Partition 23 Exhaust section 30 Conveying section 31 Rotating Table 32 motor 33 Holding part 34 Tray 40 Film forming processing section 40A GaN film deposition processing unit 40B Al film forming processing section 40C Mg film forming processing section 40D Si film deposition processing section 40E InN film deposition processing section 41 Processing Space 42 Target 43 Backing Plate 44 electrode 46 Power supply section 47 Gas inlet 48 Piping 49 Sputtering gas inlet 50 Nitriding treatment section 51 Cylindrical body 52 Window components 53 Antenna 54 RF power supply 55 Matching Box 56 Gas inlet 57 Piping 58 Process gas inlet 59 Processing Space 60 Heating section 70 Transfer room 71 Load lock section 80 Pre-heating chamber 90 Cooling room 100 control device

Claims

1. a chamber capable of creating a vacuum inside; a rotary table provided in the chamber, which holds a workpiece and circulates the workpiece along a circular path; a GaN film formation processing section including a target made of a film formation material containing GaN and a plasma generator for generating plasma from a sputtering gas introduced between the target and the rotary table, and for depositing particles of the film formation material containing GaN by sputtering on the workpiece circulated and transported by the rotary table; a nitriding unit that nitrides particles of the film-forming material deposited in the GaN film-forming unit on the workpiece circulated and transported by the rotary table; an impurity addition processing unit including a target made of a film formation material containing p-type impurities or n-type impurities, and a plasma generator for generating plasma from a sputtering gas introduced between the target made of the film formation material containing p-type impurities or n-type impurities and the rotary table, and for adding n-type impurities or p-type impurities by sputtering to particles of the film formation material containing GaN deposited on the workpiece in the GaN film formation processing unit; and The GaN film forming unit, the nitriding unit, and the impurity addition unit are arranged on the circulating transport path, and the turntable transports the workpiece so that GaN film formation, nitriding, and impurity addition are repeated by repeatedly passing the workpiece through the GaN film forming unit, the nitriding unit, and the impurity addition unit in that order, thereby forming a GaN film containing the n-type impurity or the p-type impurity on the workpiece with a predetermined number of layers.

2. 2. The film forming apparatus according to claim 1, wherein the sputtering gas is argon gas alone.

3. an Al film forming processing unit that has a target made of a film forming material containing Al, and deposits particles of the film forming material containing Al by sputtering on the workpiece that is circulated and transported by the rotary table; 3. The film forming apparatus according to claim 1, wherein the nitriding unit nitrides particles of the film forming material deposited in the Al film forming unit onto the workpiece circulated and transported by the rotary table.

4. 4. The film forming apparatus according to claim 3, wherein the GaN film forming section, the Al film forming section, and the nitriding section form a film in which GaN films and AlN films are alternately stacked.

5. the impurity addition processing unit has a target made of a film formation material containing Mg, and is an Mg film formation processing unit that deposits particles of the film formation material containing Mg by sputtering on the workpiece that is circulated and transported by the rotary table, 2. The film forming apparatus according to claim 1, wherein the GaN film forming unit, the nitriding unit, and the Mg film forming unit form a film of GaN doped with Mg.

6. The impurity addition processing unit has a target made of a film formation material containing Si, and is a Si film formation processing unit that deposits particles of the film formation material containing Si by sputtering on the workpiece that is circulated and transported by the rotary table, 2. The film forming apparatus according to claim 1, wherein the GaN film forming section, the nitriding section, and the Si film forming section form a film of GaN doped with Si.

7. an InN film formation processing unit that has a target made of a film formation material containing InN and deposits particles of the film formation material containing InN by sputtering on the workpiece that is circulated and transported by the rotary table; 7. The film forming apparatus according to claim 1, wherein the GaN film forming section, the nitriding section, and the InN film forming section form an InGaN film.

8. 8. The film forming apparatus according to claim 1, further comprising a heating section for heating the workpieces circulated and transported by the rotary table.

9. 9. The film forming apparatus according to claim 8, further comprising a preheating chamber for heating the workpiece before it is carried into the chamber.

10. 10. The film forming apparatus according to claim 1, wherein the power applied to the impurity doping processing section is applied by a pulse power supply.

11. A film forming method for forming a film on a workpiece while holding the workpiece on a rotary table and circulating and transporting the workpiece along a circumferential path in a chamber capable of being evacuated, the method comprising: a GaN film formation process in which a GaN film formation processing unit having a target made of a film formation material containing GaN and a plasma generator that converts a sputtering gas introduced between the target and the rotary table into plasma deposits particles of the film formation material containing GaN by sputtering on the workpiece that is circulated and transported by the rotary table; a nitriding process in which particles of the film-forming material deposited in the GaN film-forming process unit are nitrided on the workpiece circulated and transported by the rotary table by a nitriding process unit; an impurity addition process of adding n-type impurities or p-type impurities by sputtering to particles of the GaN-containing film formation material deposited on the workpiece in the GaN film formation processing unit, A film formation method characterized by forming a GaN film containing the n-type impurity or the p-type impurity on the workpiece with a predetermined number of layers by repeatedly performing the GaN film formation process, the nitriding process, and the impurity addition process in this order by circulating and transporting the workpiece.

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