Method for producing nitride

Abstract

To provide a manufacturing method and a manufacturing apparatus of a nitride film including a nitride of a group III element including aluminum nitride and gallium nitride, and various element techniques used in relation to the manufacturing method.SOLUTION: Provided is a manufacturing method of a nitride film includes the steps of: arranging a substrate composed of a predetermined material in an apparatus capable of a physical phase growth; depositing a flux metal or alloy composed of a predetermined material including a metal or a semiconductor element that constitutes an objective nitride film on the substrate; generating a nitrogen radical in an atmosphere to which the substrate with a deposition is exposed; and keeping the substrate with deposition to a predetermined temperature range. Also provided is an apparatus for implementing the manufacturing method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a manufacturing method and manufacturing apparatus for a nitride film containing a nitride of a Group III (or Group 13) element such as aluminum nitride or gallium nitride, and in particular to a manufacturing method and manufacturing apparatus for efficiently producing a nitride film with good crystallinity, as well as various elemental technologies used in association with the manufacturing method. [Background technology]

[0002] Nitrides such as aluminum nitride and gallium nitride have favorable thermal and electrical properties. In particular, aluminum nitride has properties such as excellent heat resistance, thermal conductivity, a wide band gap, high electrical insulation, high piezoelectricity, and thermal expansion similar to that of silicon, and is expected to be used in various electronic material applications. Such aluminum nitride is often manufactured as a film, and for example, a technology for growing the film by a radical enhanced metal organic chemical vapor deposition (REMOCVD) method without using ammonia gas has been disclosed (Patent Document 1). On the other hand, in an example of a high film formation rate, a film manufacturing method for forming a dense aluminum nitride film using a detonation spraying method has been disclosed (Patent Document 2). Epitaxy is generally known as a method with high crystallinity, but the growth rate is slow from the gas phase and the film formation conditions are limited from the liquid phase. In addition, a film formation method for an aluminum nitride film is disclosed, which is characterized by performing sputtering using a target containing at least two elements other than aluminum in an atmosphere containing nitrogen gas (Patent Document 3). The properties of the aluminum nitride film obtained in this way are affected by its crystallinity and orientation.

[0003] Meanwhile, a method has been disclosed in which nitrogen is dissolved in a gallium melt, and the melt containing nitrogen as a solute is cooled to form a gallium nitride film (for example, Non-Patent Document 1). In this method, the gallium melt is exposed to nitrogen plasma to form a gallium nitride film on a sapphire substrate. Also, aluminum metal and tin are mixed, heated and melted in a boron nitride crucible, and exposed to high-pressure nitrogen to create a nitrogen-containing melt, which is then cooled to produce an aluminum nitride single crystal (Non-Patent Document 2). Also disclosed is a method for producing a single crystal of a Group III element nitride, which comprises heating a mixed solution of at least one metal element selected from the group consisting of alkali metals and alkaline earth metals, and at least one Group III element selected from the group consisting of gallium (Ga), aluminum (Al), and indium (In) to form a flux of the metal elements, introducing a nitrogen-containing gas into a reaction chamber to react the Group III element in the flux with nitrogen to grow a single crystal of a Group III element nitride, and dropping the flux onto a base substrate from above while rotating the base substrate horizontally in the reaction chamber to grow the single crystal (Patent Document 4). Furthermore, a GaN single crystal growth method is disclosed, which includes a step of immersing a GaN substrate in a Ga-Na melt in which Ga is dissolved without rotating and pulling it up to attach the Ga-Na melt to the surface of the GaN substrate, and a step of growing a GaN single crystal on the surface of the GaN substrate by heating the GaN substrate with the Ga-Na melt attached to its surface under a nitrogen atmosphere, and is characterized in that the Ga-Na melt contains Ca or Sr as a group 2 element at a ratio of 0.05 to 2.0 mol% (the ratio of the group 2 element to the total amount of Na and the group 2 element) (Patent Document 5). Although such a melt method is considered to have high production efficiency of nitrides, there are restrictions on the substrate, etc., and there is still room for improvement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-132613 A [Patent Document 2] JP 2017-71835 A [Patent Document 3] JP 2015-54986 A [Patent Document 4] International Publication No. 2017-111000 [Patent Document 5] JP 2019-19040 A [Non-patent literature]

[0005] [Non-Patent Document 1] Jeffrey S. Dyck et al., “Growth of Oriented Thick Films of Gallium Nitride,” MRS Internet J. Nitride Semicond. Res. 4S1, G3.23 (1999) [Non-Patent Document 2] Yelim Song et al., “Conditions for growth of AlN single crystals in Al-Sn flux” J. Am. Ceram. Soc., 2018; 101: 4876-4879 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned various methods still have room for improvement in terms of a method or apparatus for producing a nitride film such as aluminum nitride, which has high productivity, desired crystallinity, and good formability, and there is a demand for the development of related technologies applicable to the production of such nitride films. [Means for solving the problem]

[0007] In view of the above circumstances, the present inventors have reexamined the characteristics of various methods and succeeded in finding the following method for producing a nitride film. For example, in a method or apparatus for producing a nitride film of a Group III metal such as aluminum, gallium, or indium, which has a relatively low melting point, an apparatus including a physical vapor deposition apparatus can be used to produce a metal nitride having a melting point higher than that of these metals. In addition, related technologies have been developed for such a production method or apparatus.

[0008] More specifically, it may include the following: (1) A method for producing a nitride film, comprising the steps of: placing a substrate made of a predetermined material in an apparatus capable of physical vapor deposition; depositing a flux metal or alloy made of a predetermined material containing a metal or semiconductor element that will form a target nitride film onto the substrate; generating nitrogen radicals in an atmosphere to which the substrate with the flux metal or alloy deposited thereon is exposed; and maintaining the substrate with the flux metal or alloy deposited thereon within a predetermined temperature range. The method according to any one of the above, wherein the metal element constituting the nitride film includes a Group III metal. Any of the above methods, characterized in that the flux metal or alloy consists solely of the metal or semiconductor elements that make up the nitride film. (2) Any of the above methods, wherein the apparatus includes an apparatus capable of producing a metal thin film. (3) Any of the above methods, characterized in that the flux metal or alloy contains at least one or more elements selected from the group consisting of aluminum, gallium, tin, bismuth, indium, and lead. (4) Any of the above methods, wherein the flux metal or alloy contains at least tin. (5) Any of the above methods, wherein the substrate material is a single crystal capable of epitaxially growing the desired nitride. (6) Any of the above methods, wherein the step of generating nitrogen radicals includes performing sputtering in a nitrogen atmosphere, and the target material is resistant to the sputtering. (7) Any of the above methods, wherein the predetermined temperature range is above the melting point of the flux metal or alloy and below the boiling point of the same metal or alloy. (8) Any of the above methods, wherein the Group III metal of the Group III metal nitride film contains aluminum and / or gallium. (9) Any of the above methods further comprising a chemical treatment step to remove the flux metal or alloy. (10) An apparatus for producing a nitride film, comprising: a substrate made of a predetermined material and arranged at a predetermined position; a metal or other material source containing a metal or semiconductor to be attached to the substrate by physical vapor deposition; a resistant target resistant to sputtering in a nitrogen gas atmosphere; an energy source for causing metal vapor or particles to escape from the metal or other material source usable for physical vapor deposition; a control device for turning the energy source on and off; a chamber for isolating an internal atmosphere from the outside; a gas supply unit for supplying a predetermined type of gas to the internal atmosphere; a vacuum system for evacuating the chamber; and a heater for heating the substrate, wherein the substrate comprises oriented crystals having a surface on which the nitride film can be grown, and the metal or semiconductor to be attached by physical vapor deposition contains a metal element that functions as a flux in addition to the metal or semiconductor element constituting the nitride film to be produced, and the resistant target is exposed to high frequency sputtering in a nitrogen gas atmosphere, 11. An apparatus for producing a nitride film, comprising: a heater capable of maintaining a substrate having a metal or semiconductor deposited thereon facing the resistive target at a predetermined temperature during the RF sputtering. (11) A method for producing a nitride film, comprising the steps of: maintaining a substrate having attached thereto a flux metal or alloy made of a predetermined material containing a metal or semiconductor element that constitutes a target nitride film, at a predetermined temperature at which at least a portion of the flux metal or alloy melts; and contacting nitrogen radicals with the at least a portion of the melted flux metal or alloy. (12) A method for generating nitrogen radicals, comprising: a step of supplying nitrogen in a predetermined pressure range to form a nitrogen atmosphere; and a step of applying a high frequency wave across the nitrogen atmosphere, wherein the application of the high frequency wave corresponds to sputtering with a target made of a resistant material on the cathode side.

[0009] Here, physical vapor deposition is one of the deposition methods for forming a thin film on the surface of a substance, and is a method for depositing a thin film of a target substance on the surface of a substance in a gas phase by a physical method, and the apparatus may be an apparatus capable of depositing such a film. The substrate may be made of a predetermined material. The predetermined material may include an element or compound having a crystal face on which a nitride film can be grown. For example, it may include alumina, silicon carbide, silicon, etc. The nitride film may mean a film made of a nitride of a metal or a semiconductor. The metal may include a metal element, and the metal element may include an alkali metal (group I element), an alkaline earth metal (group II element), or a transition element (group III to XII element). The group III element may also be called a boron group element. The group III metal constituting the above-mentioned group III metal nitride film may include at least one selected from aluminum, gallium, and indium. A semiconductor is a material having an intermediate resistivity between a conductor (good conductor) such as a metal with good electrical conductivity and an insulator (non-conductor) with high electrical resistivity. For example, it may include elemental semiconductors such as silicon (Si) and germanium (Ge). The above-mentioned metal and other material sources may include metals, alloys, semiconductors, etc. such as these. The flux metal or alloy may include a metal or alloy that functions like a solvent or solvent when melted. Here, nitrogen and metals or semiconductors that constitute the nitride may be dissolved. When the flux metal or alloy is composed only of a metal or semiconductor element that constitutes the nitride film, it may not include other metals that do not constitute the nitride film. The apparatus capable of producing a metal thin film may include so-called PVD (Physical Vapor Deposition) apparatus such as an MBE (Molecular Beam Epitaxy) apparatus, an ALD (Atomic Layer Deposition) apparatus, or a sputtering apparatus. It may also include a radical gun or the like. The energy source that ejects the above-mentioned metal vapor or particles may include an energy source such as a power supply that is appropriately applied to various apparatuses. In the case of including a sputtering apparatus, a part or assembly capable of sputtering may be incorporated. It may include various apparatuses such as a high-frequency sputtering apparatus, a magnetron sputtering apparatus, etc. It is not necessary to exclude other apparatuses capable of physical vapor deposition.The predetermined position where the substrate is placed may be a position where the metal or semiconductor film or nitride film to be attached to the substrate can be easily deposited. For example, a position exposed to the gas phase when the constituent elements of these films are present in the gas phase is preferable. The material source such as metal may be a solid containing the metal or semiconductor to be used as the material. It may be solidified by various methods such as sintering and powder pressing. The substrate material may include a single crystal having a desired crystal face on the surface. For example, it may be at least one selected from alumina, SiC, Si, GaN, and ZnO. The flux metal or alloy may include at least one selected from Sn, Bi, Ga, In, and Pb in addition to the Group III metal that constitutes the Group III metal nitride film. The step of attaching the flux metal or alloy may include a sputtering method using the flux metal or alloy as a target. When multiple targets are used, they can be appropriately covered with a shield. Also, a substrate shutter that covers the substrate may be included as an option. The shutter may be controlled to cover (close) the substrate when no film is desired to be formed on the substrate, and to uncover (open) the substrate when film may be formed. The atmosphere to which the deposited substrate is exposed may contain nitrogen, which may be plasmatized. The step of generating nitrogen radicals may use nitrogen plasma. In the step of holding the deposited substrate within a predetermined temperature range, the predetermined temperature range may be a range in which nitrogen is readily dissolved in the flux metal or alloy. The chemical treatment step may include dissolution with an acid or alkali.

[0010] By using the above-mentioned manufacturing method and manufacturing apparatus, it is possible to deposit a preferable Group III metal nitride film on a predetermined substrate, and the film has excellent orientation and crystallinity, and is therefore expected to be used as an electronic material. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an apparatus for producing a Group III metal nitride film in an embodiment of the present invention. [Diagram 2] 1A to 1C are diagrams illustrating a process for producing an aluminum nitride film in an embodiment of the present invention. [Diagram 3] In an embodiment of the present invention, (a) shows a schematic diagram of the target configuration, (b) shows the metal composition deposited during production using this device and the X-ray analysis results of the aluminum nitride film obtained, and (c) shows the temperature of the nitriding process performed with the optimal deposited metal composition and the X-ray analysis results of the aluminum nitride film obtained. [Figure 4] This figure shows the results of measuring nitrogen plasma with an optical measurement device in the apparatus used in the examples shown in Figure 1. [Diagram 5] 1A is a cross-sectional view of an aluminum nitride film manufactured in an embodiment of the present invention before removal of flux metal and the like, and FIG. 1B is a cross-sectional view of an aluminum nitride film manufactured in an embodiment of the present invention after removal of flux metal and the like. [Figure 6] 1 is a graph in which the half-width is plotted against the growth time for aluminum nitride films produced in the examples of the present invention and aluminum nitride films produced in the comparative examples. [Figure 7] 1 is a graph showing the results of component analysis in the depth direction by SIMS for (a) an aluminum nitride film produced in a comparative example and (b) an aluminum nitride film produced in an example of the present invention. [Figure 8] FIG. 13 is a diagram showing an X-ray diffraction pattern of GaN grown by a flux film-coated sputtering method in another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, in which like elements are given like reference numerals and their description will be omitted.

[0013] [Example 1] [Aluminum nitride film manufacturing equipment] FIG. 1 illustrates an apparatus that can be used in an embodiment of the present invention. It is a schematic diagram of an apparatus 10 for producing an aluminum nitride film using an RF sputtering apparatus. At the center upper part is a sapphire (alumina) substrate 12, which has the same configuration as a sputtering apparatus. The substrate 12 is attached to a substrate holder (not shown), and the substrate holder is equipped with a heater 14 shown above the sapphire substrate. The heater 14 is usually a resistive heater, and the temperature can be controlled by a thermocouple (not shown), but it mainly heats the substrate 12. At the lower left corner, a radiant heater 16 is provided, but this is optional, and the substrate holder heater 14 described above may be the only heater. At the upper left corner, a vacuum system 18 is depicted, which means a vacuum pump or the like that can evacuate the chamber 20 in which the substrate 12 is placed. Below the sapphire substrate 12 in the figure, an aluminum target 22, a tin target 24, and a zirconia target 26 are respectively placed on independent cathodes 23, 25, and 27. The Al and Sn compositions to be deposited are controlled by the RF power applied to the respective targets 22, 24, 26 (see RF power source 28 and control device 30). A gas source 32 is illustrated diagrammatically on the right side, and introduces a gas of a necessary atmosphere into the chamber 20. Argon is mainly used when depositing Sn and Al onto the substrate 12. A RF power source 28, diagrammatically illustrated in the upper right corner, applies a high frequency between the target and the substrate via a power cable 34, as necessary. In this figure, an Al-Sn-based metal film is shown to have been formed on the substrate 12 (the lower side in terms of the vertical relationship of the overall figure), and a molten phase is diagrammatically illustrated as molten growth at the interface with the substrate. This is deposited on the substrate 12 as a result of sputtering the Al target 22 and the Sn target 24 immediately after the substrate 12 is attached to the present apparatus 10. At this time, Ar may be introduced into the chamber 20, and the Al target and the Sn target are exposed to the plasma-like Ar. Thereafter, heating is performed with a heater to melt the Al--Sn based metal on the sapphire substrate 12. The melting point of Al is about 660°C, and the melting point of Sn is about 230°C.According to the phase diagram of the Al-Sn system, although there is a eutectic at around 99 wt% Sn, Sn and Al form a homogeneous alloy melt.

[0014] Next, nitrogen gas is introduced into the chamber 20. Nitrogen is usually in the form of molecules, but when high frequency waves are applied, the nitrogen in the chamber is radicalized. At this time, the zirconia target 26 faces the substrate 12 (or the film attached on the substrate). In addition, sputtering is prevented by controlling so that RF power is not applied to the Al target 22 and the Sn target 24. Zirconia has a high melting point, and Zr and O atoms are not ejected even by sputtering with nitrogen atoms or molecules that have been plasmaized by high frequency waves. Nevertheless, since high frequency waves are applied, most of the plasma nitrogen that collides with the target is probably radicalized. Therefore, it is in a different state from nitrogen that has been plasmaized by microwaves, and it is considered that the nitrogen that has been radicalized by this method dissolves in the Al-Sn-based molten liquid. The dissolution rate and / or dissolution amount at this time are considered to be greater than that of plasma molecular nitrogen. In addition, since the Al-Sn-based molten liquid has a low surface tension and is easily wetted with sapphire, it can maintain a state of adhering to the substrate surface against gravity. In this state, if the temperature is appropriately controlled, it is considered that, due to thermodynamic stability, aluminum nitride nuclei are formed on the surface of the substrate, which grow to form an aluminum nitride film covering the entire surface. Since tin nitride is not necessarily thermodynamically stable, it is considered that liquid tin does not form nitrides, but diffuses nitrogen from the gas phase surface to the substrate side, promoting a reaction with aluminum. In addition, the substrate surface is usually placed downward to prevent unnecessary foreign matter from falling onto the substrate surface, but in the embodiment of the present application, the substrate surface can also be placed upward if inconveniences can be avoided. Alternatively, the substrate can be placed vertically or obliquely at an angle, but since the viscosity of the Al-Sn melt is usually low, the melt is likely to accumulate at one end of the substrate, which is not preferable.

[0015] Once a certain amount of aluminum nitride film has formed, the formation rate slows down, so the temperature is lowered below the melting point of tin to terminate the reaction. Unnecessary tin and unreacted aluminum are dissolved from the substrate, which is placed under room temperature and pressure, using an acid such as hydrochloric acid to refine the aluminum nitride film.

[0016] [Example 2] [Production of aluminum nitride film] FIG. 2 illustrates the manufacturing method carried out in more detail. The method is carried out along the time axis by the above-mentioned apparatus (for example, magnetron sputtering apparatus). A sapphire substrate ((0001) surface) with a diameter of 2 inches (about 5 cm) was attached to a substrate holder. Targets of metallic aluminum (99.999%, Nilaco Corporation), metallic tin (99.999%, Rare Metallic Corporation), and sintered ZrO2 (Towa Kogyo Co., Ltd.) were installed independently. The chamber was once evacuated, and Ar was introduced at 0.6 Pa to carry out normal sputtering with the aluminum target and the tin target under the conditions shown in FIG. 2. The composition of the Al-Sn-based metal sputtered on the sapphire substrate was Al:Sn=12:88 (mol). Next, nitridation was carried out. Specifically, the temperature of the substrate was raised to above the melting point of the alloy by a heater, and nitrogen radicals were generated by supplying RF power to the ZrO2 target for 30 minutes to 2 hours, thereby performing nitridation. Here, 30 W of power was applied to the ZrO2 target. At this time, nitrogen plasma was performed under the conditions shown in Figure 2. The obtained nitrogen radicals were easily dissolved in Al-Sn-based metal, and an aluminum nitride film was formed on the sapphire substrate. The pressure of the nitrogen (including plasma state, etc.) atmosphere is preferably 0.1 Pa or more, 0.3 Pa or more, or 0.5 Pa or more. Due to the structure of the apparatus, a high-pressure atmosphere is not industrially preferable, and 0.1 MPa or less, 0.01 MPa or less, or 0.001 MPa or less is preferable. At this time, the temperature of the substrate was changed from 460 ° C to 610 ° C. The substrate was rotated at 6 rpm during nitridation. After the nitridation process, the substrate was dipped in a hydrochloric acid solution to remove the tin flux metal or alloy and unreacted Al. In this specification, this method for producing a nitride film is called flux film-coated sputtering (FFC-sputtering).

[0017] In the above examples, the flux composition (Al-Sn composition) and the growth temperature (temperature in the nitriding process) are considered to be particularly important for the crystallinity of the obtained aluminum nitride film. Since the flux composition is affected by the initial Al-Sn sputtering, the wall shown in FIG. 3(a) was used to change the flux composition in sequence. This can be done without rotating the substrate. The obtained Al-Sn composition was measured by EDX (Horiba, EMAX 6853-H) after peeling off the evaporated flux at five positions as shown in FIG. 3(a). The composition analysis of the metal film was not affected by the substrate because it was peeled off from the substrate. The flux composition at each substrate position is as shown in FIG. 3(b), and the optimal composition was 12:88. This is because the composition corresponds to the one with the highest crystallinity from the X-ray analysis result of AlN in FIG. 3(b) (using Rigaku, RINT-2200).

[0018] Figure 3(c) shows the results of X-ray analysis (using Rigaku Corporation's RINT-2200) of aluminum nitride films obtained with the same flux composition, comparing different processing temperatures during the nitriding process. At temperatures above 490°C, the X-ray analysis shows a peak related to AlN growth. However, it goes without saying that AlN can also grow at temperatures below that.

[0019] Figure 5(a) shows a cross-sectional view of an aluminum nitride film before the flux was removed with hydrochloric acid. Al-Sn metal was sputtered onto a sapphire substrate for 5 hours. The nitridation process involved heating at 610°C for 2 hours. Figure 5(b) shows the 0.7 μm thick AlN film after the remaining flux was removed.

[0020] [Comparative Example] [Production of aluminum nitride films by reactive sputtering] Using the same magnetron sputtering system, reactive sputtering was performed using a sapphire substrate and an aluminum target at 45 W. The reactive sputtering was optimized between room temperature and 500° C. The pressures were 0.6 Pa and 1.0 Pa, and Ar:N2=5:10 (sccm) and 10:10 (sccm).

[0021] [Example 3] [Nitrogen radicalization] It is known that nitrogen radicalized in plasma is easily dissolved in the flux metal or alloy. Nitrogen radicals can be confirmed by an optical spectrometer. In Example 2, the emission spectrum during the nitriding process was measured. The results are shown in Figure 4. As shown in this figure, there are spectrum groups for the first positive and second positive, and the excitation of nitrogen molecules is observed. The nitrogen molecule is in the ground state at the bottom, and the higher the energy level is, the higher the energy level becomes, and the level has multiple discrete levels due to the vibration of electrons. For example, B 3 From the level of Πg, A 3 Σ u + The transition to B is called the first positive and is observed around 550-800 nm. 3 From the level of Πg to C 3 Π u The transition to is called a second positive. See, for example, Figure 1 in J. Appl. Phys. 114, 093704 (2013) "Electrical properties of scandium nitride epitaxial films grown on (100) magnesium oxide substrates by molecular beam epitaxy", Figure 2 in J. Appl. Phys. 98, 023522 (2005) "High nitrogen incorporation in GaAsN epilayers grown by chemical beam epitaxy using radio-frequency plasma source", and Figure 1 in Journal of Crystal Growth 189 / 190 (1998) 390D394 "Growth of cubic III-nitrides by gas source MBE using atomic nitrogen plasma: GaN, AlGaN and AlN", etc. In this way, the target can be made of a material that is solid, inert, has a high melting point, is chemically stable, and is not etched when nitrogen molecules collide with it, not limited to ZrO2 (melting point: 2715°C). For example, alumina (melting point: 2072°C), stabilized zirconia, and partially stabilized zirconia can be used. Nitrogen radicals are easily dissolved in the flux metal or alloy. When high-frequency sputtering is performed on such a target in a nitrogen atmosphere, nitrogen radicals can be generated. Here, as a method for generating nitrogen radicals, for example, a high-frequency sputtering device (which may include any existing type such as a magnetron type) can be applied. A predetermined container such as a chamber may be evacuated once, and nitrogen gas at a predetermined pressure may be introduced. A high-frequency wave is applied between a mounted substrate (which may be made of a highly stable material) and a target (preferably a material resistant to sputtering by nitrogen) to generate nitrogen plasma. The frequency at this time is preferably 100 kHz or more, 500 Hz or more, or 1 MHz or more. Also, it is preferably 500 MHz or less, 200 MHz or less, or 100 MHz or less. The nitrogen atmosphere pressure is preferably 0.1 Pa or more, 0.3 Pa or more, or 0.5 Pa or more. Also, it is preferably 100 Pa or less, 50 Pa or less, or 10 Pa or less. The output is preferably 0.1 W or more, 1 W or more, or 10 W or more. Also, 10 kW or less, 1 kW or less, or 500 W or less are preferable. All of the above values ​​are for the case where a 1-inch target is used. The target material is preferably one that has a high melting point and is inactive. For example, oxides such as ZrO2 or alumina are preferable. ZrO2 is preferable. Such nitrogen radicals may be generated in a high-frequency sputtering device or the like, in a chamber into which a nitrogen atmosphere is introduced within a predetermined pressure range, using a target made of an inactive material that has a high melting point, a radical gun, or the like.

[0022] [Comparison between Example 2 and Comparative Example] In the manufacturing method of forming a GaN film from the liquid phase of Ga, it is considered that Ga itself becomes a flux metal or alloy and forms a GaN film. In this embodiment of the present application, the AlN film was oriented in the c-axis direction and had good crystallinity. This can be confirmed from FIG. 6. FIG. 6 shows the results of crystallinity analysis using the rocking curve method for the AlN film formed in Example 2 and the AlN film formed by reactive sputtering in the comparative example, using the rocking curve method for the (0002) plane. The square plot is the half-width of the (0002) plane in Example 2, and the black dotted line is the half-width of the (0002) plane in the comparative example, and as can be seen from this, the half-width (FWHM) is smaller in Example 2 in both cases. Therefore, it can be seen that Example 2 has better crystallinity.

[0023] The impurity concentration was examined to a depth of about 200 nm in the AlN film of Example 2 and the AlN film of the comparative example using SIMS. FIG. 7(a) shows the results of the comparative example, and FIG. 7(b) shows the results of Example 2. As can be seen from these figures, the O and C concentrations are particularly high in Example 2 from the surface to 200 nm. The concentration of remaining Sn is also observed. However, as shown in FIG. 6, the crystallinity of the AlN film of Example 2 is high, and it can be said that the method of Example 2 can form an AlN film with excellent thermal and electrical properties even if the O and C concentrations are high.

[0024] [Method for producing Group III metal nitride film] As described above, the manufacturing method according to the embodiment of the present invention produces a Group III metal nitride film by preparing a predetermined substrate, attaching a metal or alloy-based flux (including a Group III metal that is a raw material for the Group III metal nitride film) to the substrate, and carrying out a nitriding treatment in a nitrogen radical atmosphere within a predetermined temperature range. Furthermore, the flux metal or alloy and unreacted Group III metal may be removed by a chemical treatment. Also, the Group III metal nitride film may be physically or chemically peeled off from the substrate.

[0025] [Example 4] [Production of gallium nitride films] Gallium nitride films were produced by the flux film-coated sputtering method described above. At this time, Sn was used as a flux material to grow GaN films on sapphire substrates. A ZrO2 target was used to generate nitrogen radicals, and a GaN target was used as a Ga source because of the low melting point of gallium. To deposit a Ga-Sn flux film, 20 W was supplied to the GaN target and Sn target, respectively, and Ar gas was flowed at 10 sccm. Then, the substrate temperature was raised to 610°C, and nitridation was performed for 30 minutes by introducing nitrogen radicals generated from nitrogen plasma. After the nitridation process, the GaN film on the sapphire substrate was immersed in a hydrochloric acid solution to dissolve the flux metal or alloy. Figure 8 shows the X-ray diffraction pattern of the GaN film obtained on the sapphire substrate. A c-axis oriented GaN film on a sapphire substrate was obtained by the flux film-coated sputtering method. X-ray diffraction pattern results indicate that the flux film coated sputtering method is a promising method for growing AlN and other nitrides.

[0026] [substrate] The substrate is preferably a single crystal. It may have the same composition as the nitride film to be produced. It may also have a different composition. Since nitridation is performed by heat treatment, a simple substance or compound having a high melting point is preferable. The melting point is preferably higher than that of the metal or alloy used as the flux. It is also preferable that it is higher than the melting point of the group III metal. Naturally, it is preferable that it has a surface that allows epitaxy of a preferred nitride. It is also preferable that it does not react with group III metals including aluminum, gallium, and indium. In particular, it is preferable that it is inhibited in reaction with aluminum and gallium. It is preferable that it does not react with tin or nitrogen under the conditions of this method. When used together with the film for a device, it is preferable that the substrate has a high thermal conductivity. It is preferable that it is inert and does not dissolve in the chemical treatment agent used to remove the flux metal or alloy. For example, it is preferable that it does not react with hydrochloric acid (including strong hydrochloric acid). For example, SiC, Si, sapphire, GaN, ZnO, etc. can be used.

[0027] [Example 5] [Flux metal or alloy adhesion] Flux metals or alloys preferably have a low melting point. Flux metals or alloys preferably have a low vapor pressure near the melting point. If the vapor pressure is high, it becomes difficult to maintain the liquid state. Examples of such metals include Bi (melting point: 272°C, vapor pressure: 1 Pa (668°C), easily dissolves in hydrochloric acid, low price), Ga (melting point: 29.7°C, vapor pressure: 1 Pa (1037°C), expensive), In (melting point: 156°C, vapor pressure: 1 Pa (923°C), post-treatment: easily dissolves in hydrochloric acid, expensive), Pb (melting point: 327°C, vapor pressure: 1 Pa (705°C), post-treatment: dissolves in nitric acid, low price), etc. Such a method of depositing a flux metal or alloy may include a gas phase method including sputtering. It may also include evaporation, but care must be taken when depositing metals with different vapor pressures. Sputtering is advantageous in that it is not necessary to be concerned about mutual reactivity or so-called vapor pressure. In addition, a method that does not require unnecessarily high or low substrate temperature is preferable, and a method with a high deposition rate is preferable. In addition, since nitrogen radicals are formed in a post-process, a method that can easily form the radicals is preferable. In this embodiment, the substrate is placed facing downward, but this is not necessary. The substrate may be facing upward.

[0028] [Nitrogen radical generation] It is preferable to dissolve nitrogen in the flux metal or alloy. For this purpose, it is preferable to form nitrogen radicals. The method may include a method of attaching a compound containing nitrogen to the attached flux metal or alloy, and dissolving nitrogen in the flux metal or alloy. In order to dissolve nitrogen atoms, nitrogen radicals, nitrogen molecules, nitrogen ions, etc. in the gas phase in the flux metal or alloy, it is possible to devise a shape that increases the area of ​​the interface. Since a certain amount of energy is required to generate nitrogen radicals, it is preferable to generate nitrogen plasma. The nitrogen plasma may include a method of forming nitrogen plasma by applying high frequency waves or electromagnetic waves such as microwaves. The above-mentioned method for converting nitrogen into radicals can be carried out.

[0029] [Nitriding] When nitrogen at a predetermined concentration or more is contained in the flux metal or alloy, a Group III metal nitride film containing aluminum nitride can be formed on the substrate. The temperature of the substrate and / or the temperature of the flux metal or alloy at that time is within a temperature range in which a Group III metal nitride can be formed. For example, it may be equal to or higher than the melting point of the flux metal or alloy. This is because it is preferable to make the metal or alloy flux liquid phase. When the flux metal or alloy contains Sn, it may be equal to or higher than the melting point of Sn. When the flux metal or alloy contains Sn and an aluminum nitride film is produced, it is preferable that the temperature is 300°C or higher. It is preferable that the temperature is 350°C or higher, 400°C or higher, or 450°C or higher. If the temperature is too high, there may be inconveniences such as evaporation of the flux metal or alloy, so it is preferable that the temperature is not too high. It may be 1300°C or lower, 1000°C or lower, or 610°C or lower. The temperature may be increased by installing any heater on the substrate holder as in Example 2, and may be heated by, for example, a resistance heater and / or a radiation heater. As the radiant heater, existing technologies such as laser light and xenon lamps can be applied. The nitriding process can be stopped by lowering the temperature and / or by stopping the supply of nitrogen. The nitriding may be followed by a post-solidification heat treatment to remove distortion. The atmosphere may contain nitrogen, if desired.

[0030] [Removal of flux metals, etc.] Flux metals or alloys and unreacted metals may be removed with a chemical treatment.

[0031] As described above, by carrying out the predetermined steps, a Group III metal nitride film having excellent crystallinity can be formed, which can provide a preferable electronic material such as a surface acoustic wave device, a power device, a light emitting diode, or a piezoelectric element. [Explanation of symbols]

[0032] 10: Apparatus for producing aluminum nitride film; 12: Substrate; 14: Heater 16 Radiation heater 18 Vacuum system 20 Chamber 22 Aluminum target 23, 25, 27 Cathode 24 Tin target 26 Zirconia target 28 High frequency power supply 30 control device 32 gas source 34 power cable

Claims

1. sputtering a film comprising a metal or semiconductor-containing material and a flux metal onto a substrate placed in a physical vapor deposition apparatus; After the film deposition step, generating nitrogen radicals by exposing the surface of the zirconia or alumina target to nitrogen plasma; forming a nitride film by nitriding the material contained in the film by exposing the film to the nitrogen radicals; and after the step of forming the nitride film, maintaining the substrate within a predetermined temperature range.

2. 2. The method of claim 1, wherein the physical vapor deposition equipment comprises an equipment for producing thin metal films.

3. 3. The method according to claim 1, wherein the film contains at least one or more elements selected from the group consisting of aluminum, gallium, tin, bismuth, indium, and lead.

4. 4. The method of claim 3, wherein said flux metal comprises at least tin.

5. 5. The method according to claim 1, wherein the material of the substrate is a single crystal on which the nitride film can be epitaxially grown.

6. 6. The method according to claim 1, wherein the predetermined temperature range is equal to or higher than the melting point of the film and equal to or lower than the boiling point of the film.

7. 7. The method according to claim 1, wherein the metal element constituting the nitride film includes a Group III metal element including aluminum and / or gallium.

8. 8. The method of claim 1, further comprising a chemical treatment step to remove the flux metal after the step of holding the substrate at a predetermined temperature range.

9. A chamber; a substrate holder disposed within the chamber and adapted to receive a substrate; a source of material, such as a metal or semiconductor, disposed within the chamber for deposition on the substrate by physical vapor deposition; a zirconia or alumina target disposed within the chamber; an energy source that causes metal vapor or particles to be ejected from the metal or other material source; A control device that turns the energy source on and off; a gas supply unit that supplies a gas into the chamber; a vacuum system for evacuating the chamber; a heater for heating the substrate; the substrate includes an oriented crystal having a surface on which a nitride film is to be grown; the metal or semiconductor deposited by physical vapor deposition contains, in addition to the metal or semiconductor elements constituting the nitride film, a metal element that functions as a flux; The target is subjected to radio frequency sputtering in a nitrogen gas atmosphere; 1. An apparatus for producing a nitride film, comprising: a heater for maintaining a substrate, on which a metal or semiconductor is deposited, facing said target at a predetermined temperature during said high frequency sputtering.

10. A step of maintaining a substrate having a flux metal or alloy attached thereto, the flux metal or alloy being made of a material containing a metal or semiconductor element that constitutes a nitride film, at a temperature at which at least a portion of the flux metal or alloy melts; generating nitrogen radicals by exposing a surface of a zirconia or alumina target to nitrogen plasma; forming a nitride film by exposing the at least partially melted flux metal or alloy to the nitrogen radicals; A method for producing a nitride film comprising:

11. A step of generating nitrogen radicals in a nitrogen atmosphere by applying high frequency power to the nitrogen atmosphere while a zirconia or alumina target placed in the nitrogen atmosphere is set on the cathode side; A method for generating nitrogen radicals comprising the steps of:

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