Method for producing gallium nitride, vapor phase growth apparatus for gallium nitride, and gallium nitride substrate

Abstract

To provide a method for producing a gallium nitride that can improve electrical conductivity of an n-type gallium nitride substrate.SOLUTION: A method for producing a gallium nitride using a vapor phase growth method that does not use an organic metal for a gallium raw material includes the steps of: supplying a first raw material gas including gallium into a reaction vessel in which a substrate is placed; supplying a second raw material gas including nitrogen and reacting with the first raw material gas into the reaction vessel; and supplying a third raw material gas including tin into the reaction vessel, where the steps of supplying the first, second and third gases are performed while a temperature of the substrate is within the range of 700°C or more and 1100°C or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification discloses techniques relating to a gallium nitride manufacturing method, a gallium nitride vapor phase growth apparatus, and a gallium nitride substrate. [Background technology]

[0002] There is a demand for improving the electrical conductivity of n-type gallium nitride (GaN) substrates. This is because it is possible to reduce the on-resistance and, therefore, reduce energy loss. Silicon (Si), germanium (Ge), oxygen (O), etc. are generally used as donors for GaN. Related technology is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-202366 A Summary of the Invention [Problem to be solved by the invention]

[0004] When using Si or Ge as the donor, it is difficult to sufficiently increase the concentration of the donor in the GaN crystal. Since the donor concentration cannot be increased, it is difficult to increase the carrier concentration. When using O as the donor, it is possible to increase the impurity concentration more than with Si or Ge. However, since the donor activation rate of O is low at about 20%, it is difficult to increase the carrier concentration. [Means for solving the problem]

[0005] This specification discloses a method for producing gallium nitride using a vapor phase growth method that does not use an organic metal as a gallium source. The method includes a step of supplying a first source gas containing gallium into a reaction vessel in which a substrate is placed. The method includes a step of supplying a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel. The method includes a step of supplying a third source gas containing tin into the reaction vessel. The steps of supplying the first source gas, supplying the second source gas, and supplying the third source gas are performed when the substrate temperature is in the range of 700°C to 1100°C.

[0006] The present inventors have found that when tin is used as a donor, the concentration of tin incorporated into the GaN crystal can be significantly increased by using a growth temperature lower than that of a general GaN growth temperature. In addition, when a growth temperature lower than that of a general growth temperature is used, the surface becomes rough due to a large number of pits, and good GaN crystals may not be obtained. However, the present inventors have found that the surfactant effect of tin can suppress the formation of pits. As a result, the method for producing gallium nitride in this specification can achieve both high concentration doping of tin and good crystallinity. Tin can have a higher doping concentration than silicon or germanium, and can have a higher activation rate than oxygen, making it possible to form an n-type GaN substrate with a high carrier concentration and high conductivity.

[0007] The step of supplying the first source gas, the step of supplying the second source gas, and the step of supplying the third source gas may be performed at a substrate temperature in the range of 800° C. or more and 950° C. or less.

[0008] The first source gas may be a gas containing gallium chloride, the second source gas may be a gas containing ammonia, and the third source gas may be a gas containing tin chloride.

[0009] The ratio of the molar flow rate of tin chloride contained in the third source gas to the total molar flow rate of gallium chloride contained in the first source gas and tin chloride contained in the third source gas is 1×10-3 It may be more than that.

[0010] The substrate may be rotated about an axis perpendicular to the surface of the substrate.

[0011] The manufacturing method may further include a step of supplying a fourth source gas containing at least one of silicon and germanium into the reaction vessel simultaneously with the supply of the third source gas.

[0012] One aspect of the gallium nitride vapor phase growth apparatus disclosed in this specification is a gallium nitride vapor phase growth apparatus used for a vapor phase growth method that does not use an organic metal as a gallium source. The vapor phase growth apparatus includes a reaction vessel, a substrate holder disposed in the reaction vessel, a first source gas supply pipe that supplies a first source gas containing gallium into the reaction vessel, a second source gas supply pipe that supplies a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel, a third source gas supply pipe that supplies a third source gas containing tin into the reaction vessel, and a first heating unit that heats the temperature of the substrate held by the substrate holder to a range of 700°C to 1100°C.

[0013] The third source gas supply pipe may be configured to allow metallic tin to be placed on a supply path. The vapor phase growth apparatus may further include a second heating unit capable of heating the metallic tin placed in the third source gas supply pipe.

[0014] The first source gas supply pipe may be configured so that a solid part containing gallium can be arranged on the supply path. The vapor phase growth apparatus may further include a third heating part capable of heating the arranged solid part. The heating temperatures by the first heating part, the second heating part and the third heating part may be equal.

[0015] The distance between the substrate holding part and the end positions of the outlet sides of the first and third source gas supply pipes may be greater than the distance between the substrate holding part and the end position of the outlet side of the second source gas supply pipe.

[0016] One embodiment of the gallium nitride substrate disclosed in the present specification is a gallium nitride substrate that functions as an n-type semiconductor. 19 The tin concentration distribution in the direction perpendicular to the surface of the gallium nitride substrate is approximately constant in the depth direction.

[0017] The activation rate of the doped tin may be 70% or more.

[0018] The tin concentration may vary periodically in the depth direction.

[0019] Satellite peaks reflecting the periodicity of the tin concentration in the depth direction may be present around the reflection peaks obtained in 2θ-ω scanning by X-ray diffraction.

[0020] The gallium nitride substrate has a tin concentration of 1×10 19 Resistivity is 1×10 or more. -3 It may be Ω·cm or less.

[0021] The lattice constant calculated based on the main peak angle obtained in 2θ-ω scanning by X-ray diffraction may be 0.05% or more larger than the lattice constant of a gallium nitride crystal that is not doped with tin. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a schematic cross-sectional side view of the vapor phase growth apparatus. [Diagram 2] 1 is a graph showing the correspondence relationship between tin concentration and carrier (electron) concentration. [Diagram 3] 1 is a graph showing the correspondence relationship between tin concentration and resistivity. [Figure 4] 1 is a graph showing the growth temperature dependence of tin concentration. [Diagram 5] 1 is a graph showing the correspondence relationship between tin concentration and the supply ratio of tin chloride. [Figure 6] SIMS analysis results and a schematic cross-sectional view of gallium nitride. [Figure 7] FIG. 1 shows the results of 2θ-ω scanning of the GaN (0002) surface. [Figure 8] 1 is a graph showing the correspondence relationship between tin concentration and lattice constant c. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] <Configuration of vapor phase growth apparatus> FIG. 1 shows a schematic cross-sectional view of a vapor phase growth apparatus 1 according to the present embodiment, as viewed from the side. The vapor phase growth apparatus 1 is an example of an apparatus configuration for implementing the HVPE (Halide Vapor Phase Epitaxy) method. The HVPE method is a method for growing crystals from gaseous chloride gas at high temperatures. In other words, the HVPE method is a vapor phase growth method for compound semiconductors that does not use organic metals as the gallium raw material. The HVPE method can suppress carbon contamination in the grown crystals. In addition, the HVPE method has a faster growth rate than other growth methods such as the MOVPE method, so it can grow thick GaN films. Therefore, it is possible to manufacture a GaN free-standing substrate.

[0024] The vapor phase growth apparatus 1 includes a reaction vessel 10, a raw material gas supply pipe section 20, and a gas exhaust pipe 71. The reaction vessel 10 has a cylindrical shape. The reaction vessel 10 may be made of quartz. A wafer holder 11 is disposed inside the reaction vessel 10. A wafer 13 is held on a wafer holding surface of the wafer holder 11. A rotation shaft 14 is connected to a surface of the wafer holder 11 opposite to the wafer holding surface. An end of the rotation shaft 14 is connected to a drive mechanism 15. This allows the wafer holder 11 to rotate the wafer 13 around an axis RA perpendicular to the surface of the wafer 13. The wafer holder 11 can also move the wafer 13 in the left-right direction (±x direction) within the reaction vessel 10.

[0025] The raw gas supply pipe section 20 is connected to the reaction vessel 10. The raw gas supply pipe section 20 includes a first raw gas supply pipe 21, a second raw gas supply pipe 22, a third raw gas supply pipe 23, and specific gas supply pipes 24 and 25. The raw gas supply pipe section 20 has a cylindrical shape. The specific gas supply pipe 25 has a structure in which the second raw gas supply pipe 22, the specific gas supply pipe 24, the first raw gas supply pipe 21, and the third raw gas supply pipe 23 are arranged in this order inside the specific gas supply pipe 25. The supply path of the specific gas supply pipe 25 is formed by a gap between the inner wall of the specific gas supply pipe 25 and the outer wall of the second raw gas supply pipe 22. Similarly, the supply paths of the second raw gas supply pipe 22 and the specific gas supply pipe 24 are also formed by a gap between the inner wall and the outer wall. The supply paths of the first raw gas supply pipe 21 and the third raw gas supply pipe 23 are formed by dividing the inside of the cylinder into upper and lower parts by a partition wall 27.

[0026] The first raw material gas supply pipe 21 is a pipe that supplies the first raw material gas G1 containing gallium into the reaction vessel 10. The first raw material gas supply pipe 21 supplies the first raw material gas G1 so that the flow direction is approximately perpendicular to the surface of the wafer 13. Hydrogen chloride (HCl) gas and nitrogen (N2) gas are supplied to the inlet of the first raw material gas supply pipe 21. A quartz boat 41 containing metal gallium 43 is arranged on the path of the first raw material gas supply pipe 21. A heater 32 is arranged outside the raw material gas supply pipe section 20 so as to surround the metal gallium 43. The heater 32 can heat the metal gallium 43 to a temperature range of 700°C to 1200°C. This generates gallium chloride, which can be supplied into the reaction vessel 10 from the outlet (gas supply port) as the first raw material gas G1.

[0027] The second source gas supply pipe 22 is a pipe that supplies a second source gas G2, which contains nitrogen and reacts with the first source gas G1, into the reaction vessel 10. The second source gas supply pipe 22 supplies the second source gas G2 so that the second source gas G2 flows in a direction substantially perpendicular to the surface of the wafer 13. Specifically, the second source gas G2 is a gas that contains ammonia (NH3) and nitrogen.

[0028] The third source gas supply pipe 23 is a pipe that supplies the third source gas G3 containing tin (Sn) into the reaction vessel 10. The third source gas supply pipe 23 supplies the third source gas G3 so that the flow direction is approximately perpendicular to the surface of the wafer 13. Hydrogen chloride gas and nitrogen gas are supplied to the inlet of the third source gas supply pipe 23. A quartz boat 45 containing metal tin 47 is arranged on the path of the third source gas supply pipe 23. A heater 31 is arranged outside the source gas supply pipe section 20 so as to surround the metal tin 47. The heater 31 can heat the metal tin 47 to a temperature range of 300°C to 1200°C. This generates tin chloride, which can be supplied into the reaction vessel 10 from the outlet (gas supply port) as the third source gas G3. The tin chloride may be tin(II) chloride (SnCl2) or tin(IV) chloride (SnCl4). Metallic tin 47 may be placed in the same region as metallic gallium 43 and heated simultaneously by heater 32 .

[0029] The amount of tin supplied from the third source gas supply pipe 23 can be controlled by various parameters. For example, in order to increase the amount of tin supplied, the heating temperature of the metal tin 47 may be increased, the amount of the metal tin 47 placed on the quartz boat 45 may be increased, or the distance between the outlet of the third source gas supply pipe 23 and the wafer 13 may be shortened.

[0030] The end position of the outlet side (-x direction side) of the partition between the first raw material gas supply pipe 21 and the third raw material gas supply pipe 23 is defined as end E1. The end position of the outlet side of the second raw material gas supply pipe 22 is defined as end E2. End E1 is located farther from the wafer 13 than end E2. This allows the first raw material gas G1 and the third raw material gas G3 to be mixed, and then the second raw material gas G2 to be mixed. That is, gallium chloride and tin chloride can be reacted with ammonia in a state where they are mixed first. The tin concentration distribution in the surface of the wafer 13 can be made more uniform.

[0031] The first raw material gas supply pipe 21 and the third raw material gas supply pipe 23 are configured as separate lines. This allows the flow rate ratio of the first raw material gas G1 and the third raw material gas G3 to be freely set. This makes it possible to freely adjust the amount of tin doped into the gallium nitride crystal.

[0032] The specific gas supply pipes 24 and 25 are pipes for supplying a specific gas into the reaction vessel 10. The specific gas is a gas that does not contain oxygen and does not react with the first raw material gas G1 and the second raw material gas G2. Specific examples of the specific gas include gases that contain at least one of hydrogen, nitrogen, helium, neon, argon, and krypton. In this embodiment, a mixed gas of hydrogen and nitrogen is supplied from the specific gas supply pipe 24. Also, nitrogen gas is supplied from the specific gas supply pipe 25.

[0033] A heater 30 is disposed around the outer periphery of the reaction vessel 10 so as to surround the wafer holder 11. The heater 30 is a device that heats the wafer 13 by a hot wall method. This allows the wafer 13 to be maintained at a temperature (700° C. or higher and 1100° C. or lower) sufficient for gallium nitride crystal growth. The source gas used for the vapor phase growth of gallium nitride is exhausted to a vent line via a gas exhaust pipe 71. The temperatures of the wafer 13 and the wafer holder 11 may be measured by a pyrometer or a thermocouple (not shown), and the heater may be feedback-controlled based on the measured temperatures.

[0034] <Vapor phase growth method> A method for vapor-phase growth of gallium nitride crystals on a wafer 13 by HVPE using a vapor-phase growth apparatus 1 will be described. Vapor-phase growth conditions are listed below. The heating temperature of the wafer 13 must be in the range of 700°C to 1100°C. A more preferable temperature range is 800°C to 950°C. In this embodiment, it is set to 890°C. In addition, the "ratio of the molar flow rate of tin chloride contained in the third source gas to the total molar flow rate of gallium chloride contained in the first source gas G1 and tin chloride contained in the third source gas G3" is defined as the "tin chloride supply ratio." The tin chloride supply ratio is 1×10-3 In this embodiment, the supply ratio of tin chloride is preferably 3.6×10 -3 It was decided.

[0035] The wafer 13 serving as the support substrate was prepared by growing undoped gallium nitride to a thickness of 4.5 μm on the surface of a sapphire substrate. The surface of the undoped gallium nitride was the c-plane (Ga-plane). The following conditions were used: growth time: 30 minutes, growth rate: 20 to 500 μm / h, heating temperature of metal gallium 43: 850° C., heating temperature of metal tin 47: 850° C., hydrogen chloride flow rate of first raw material gas supply pipe 21: 40 sccm, hydrogen chloride flow rate of third raw material gas supply pipe 23: 1 sccm, V / III ratio: 100, H2 / (N2+H2) ratio: 0.23.

[0036] The heater 30 is turned on to heat the wafer 13 to 890°C. The heaters 31 and 32 are also turned on to heat the metal tin 47 and metal gallium 43 to 850°C. Then, the supply of the first source gas G1, the second source gas G2, and the specific gas is started. This makes it possible to grow an Sn-doped GaN layer (a gallium nitride crystal layer doped with tin) on the wafer 13.

[0037] <Relationship between tin concentration, carrier concentration, and resistivity> Figure 2 shows the relationship between the tin concentration and the carrier (electron) concentration in the Sn-doped GaN layer. The horizontal axis is the tin concentration [cm -3 The vertical axis is the carrier concentration [cm -3 As shown in FIG. 2, it can be seen that the tin concentration and the carrier concentration are almost the same. In other words, when tin is used as a donor, it can be seen that almost 100% of the doped tin becomes an active donor. In other words, the activation rate of tin doped in GaN is about 100%.

[0038] FIG. 3 shows the relationship between the tin concentration and the resistivity of the Sn-doped GaN layer. The horizontal axis is the tin concentration [cm -3The vertical axis is resistivity [Ω·cm]. As shown in Fig. 3, the resistivity decreases as the tin concentration increases. Here, the resistivity is 1×10 -2 [Ω·cm] is defined as the guideline value for generating n-type GaN with sufficient conductivity. From Figure 3, the tin concentration is 1×10 19 [cm -3 ] or higher, it can be seen that the target value can be achieved.

[0039] Also, as shown in region R1, the tin concentration is 1×10 20 If so, increase the resistivity to 1×10 -3 It can be seen that the resistivity can be reduced to below Ω·cm. The technique described herein makes it possible to produce a Sn-doped GaN layer with such an extremely low resistivity.

[0040] <Control of tin concentration> The main parameters for controlling the tin concentration in the Sn-doped GaN layer are the growth temperature and the supply ratio of tin chloride. Figure 4 shows the growth temperature dependence of the tin concentration in the Sn-doped GaN layer. The horizontal axis is the growth temperature. The vertical axis is the tin concentration [cm -3 The supply rate of tin chloride is 3.56×10 -3 As shown in Figure 4, it is clear that tin can be incorporated into the GaN crystal if the substrate temperature during growth is within the range of 700°C to 1100°C.

[0041] As mentioned above, the resistivity is 1×10 -2 The guideline for the tin concentration to achieve [Ω cm] is 1×10 19 [cm -3That is. As shown in Fig. 4, it can be seen that by using a growth temperature of 950°C or lower, the tin concentration can be made equal to or higher than the reference value. That is, the inventors of the present invention have found that by setting the growth temperature of Sn-doped GaN by the HVPE method in the range of 800°C or higher and 950°C or lower, the incorporation concentration of tin into the GaN crystal can be significantly increased. In other words, the growth temperature of Sn-doped GaN by the HVPE method is preferably about 100°C to 250°C lower than the growth temperature of normal GaN (e.g., undoped GaN, Si-doped GaN, Ge-doped GaN, etc.).

[0042] Fig. 5 also shows the correspondence between the tin concentration and the supply ratio of tin chloride. The horizontal axis is the supply ratio of tin chloride defined above. The vertical axis is the tin concentration [cm -3 . The growth temperature was kept constant at 905°C. As shown in Fig. 5, it can be seen that by increasing the supply ratio of tin chloride, the tin concentration of the Sn-doped GaN layer can be increased.

[0043] <SIMS analysis results> Fig. 6 shows the measurement results of gallium nitride crystals by secondary ion mass spectrometry (SIMS). The growth temperature at the time of sample preparation was 890 [°C], and the supply ratio of tin chloride was 3.6×10 -3 . Other conditions were the same as the above conditions. Fig. 6(A) shows the concentration profile of tin in the depth direction using the SIMS method. Fig. 6(B) is an illustration of the structure corresponding to Fig. 6(A). The vertical axis in Fig. 6(A) is the concentration of tin [atoms / cm 3 . The horizontal axis is the depth [μm] from the surface 13s of the Sn-doped GaN layer.

[0044] As shown in Fig. 6(A), the average concentration of tin in the direction perpendicular to the surface 13s of the wafer 13 (i.e., the depth direction) is 5.1×10 19 [cm -3It can be seen that it is substantially constant. This is due to doping tin by the crystal growth method. For example, when doping tin by the ion implantation method, a Gaussian-type concentration distribution is obtained, so it is difficult to make the concentration constant in the depth direction. By making the tin concentration substantially constant in the depth direction, the conductivity in the depth direction can be made substantially constant. Thereby, when constructing a vertical device in which current flows in the depth direction, it becomes possible to reduce the on-resistance.

[0045] Also, it can be seen that the tin concentration varies periodically with a period T1 in the depth direction. The reason will be explained. The in-plane distribution of the doping concentration of tin can be biased with respect to the axis RA. This can be realized, for example, by eccentrically displacing the outlet position of the third raw material gas supply pipe 23 with respect to the axis RA in FIG. 1. Then, crystal growth is performed while rotating the wafer 13 around the axis RA. Therefore, the tin concentration can be varied periodically according to the rotation speed. The period T1 can be appropriately adjusted by the growth rate and the rotation speed. For example, when the growth rate is 27 [μm / h] and the rotation speed is 5 [rpm], the period T1 is 90 [nm]. By varying the tin concentration distribution in the depth direction with a desired period T1, various conduction characteristics can be designed.

[0046] <XRD analysis results> In order to evaluate the orientation of the grown GaN crystal, analysis by X-ray diffraction (XRD) was performed. FIG. 7 shows the 2θ-ω scanning results of the GaN (0002) plane. Profile P0 is the measurement result of undoped GaN. Each of Profiles P1 - P3 is the measurement result of Sn-doped GaN. The doping concentration of tin on the GaN substrate is the lowest for Profile P1 and the highest for Profile P3. The carrier concentrations of Profiles P1 - P3 are 1.5×10 19 [cm -3 、7.8×10 19 [cm -3 、2.5×10 20 [cm -3 , respectively.

[0047] In profile P0, the main peak angle was detected near 34.56° (see region R10). On the other hand, in profile P2, the main peak angle was detected near 34.54°. And in profile P3, the main peak angle was detected near 34.47°. This shows that the higher the carrier concentration (i.e., the higher the tin doping concentration), the lower the main peak angle (see arrow A1). This is because the tin ionic radius (0.69 [pm]) is larger than the gallium ionic radius (0.61 [pm]). And the higher the tin doping concentration and the more gallium is replaced by tin, the larger the lattice constant becomes.

[0048] In addition, in profiles P2 and P3, satellite peaks SP are present around the main peak angle. The satellite peaks SP reflect the periodicity of the tin concentration in the depth direction. The satellite peaks SP also appear at equal intervals due to the periodicity of the tin concentration distribution. In other words, by checking whether or not satellite peaks SP are present in the profile obtained by 2θ-ω scanning, it is possible to identify whether or not the tin concentration distribution in the depth direction varies periodically.

[0049] FIG. 8 shows the relationship between the tin concentration and the lattice constant c. The horizontal axis is the tin concentration [cm -3 The vertical axis is the lattice constant c [angstroms] calculated based on the main peak angle obtained in 2θ-ω scanning. In Sn-undoped GaN, the lattice constant c is about 5.187 [angstroms] (see region R20). In addition, when the tin concentration is 1×10 -19 In the above region, it can be seen that the lattice constant c increases as the tin concentration increases (see region R21). 20 [cm -3 In the region R22, the lattice constant c increases to about 5.1905 angstroms. In other words, when the tin concentration is 1×10 20 [cm -3It can be seen that the lattice constant c of the gallium nitride crystal of [

[0050] <Substrate surface morphology> When tin is not doped, if a low growth temperature of 950°C or less is used, the surface becomes rough with many pits, and good GaN crystals may not be obtained. However, the present inventors have found that even when a growth temperature of 950°C or less is used, the generation of pits can be suppressed by supplying tin. This is due to the surfactant effect of tin. That is, the surface roughness caused by lowering the growth temperature can be complementarily suppressed by the tin that is doped at a high concentration by lowering the growth temperature. This makes it possible to achieve both high concentration doping of tin and good crystallinity. Therefore, it is possible to form an n-type GaN substrate with a high carrier concentration and high conductivity.

[0051] Moreover, the higher the supply ratio of tin chloride described above is, the more likely Sn droplets are generated on the surface of the wafer 13. Sn droplets are formed when excess Sn atoms condense on the substrate surface. However, since the Sn droplets are generated only on the substrate surface, they can be removed by cleaning or polishing. Therefore, it is possible to form Sn-doped GaN with good crystallinity.

[0052] <Modification> Although the embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0053] The vapor phase growth apparatus 1 may be configured to be capable of supplying a fourth source gas containing at least one of silicon and germanium into the reaction vessel. For example, a fourth source gas supply pipe for supplying the fourth source gas may be further provided. Also, for example, a solid portion containing silicon or germanium may be disposed together with metal tin 47 or metal gallium 43. The supply of the fourth source gas may be performed simultaneously with the supply of the third source gas G3. This allows tin to be co-doped (co-doped) with at least one of silicon and germanium. As described above, the ionic radius of tin is larger than that of gallium. On the other hand, the ionic radius of silicon (0.40 [pm]) and the ionic radius of germanium (0.53 [pm]) are smaller than that of gallium. In this way, by co-doping multiple elements having different ionic radius relationships with gallium, the ease of incorporation of multiple elements into a GaN crystal can be improved by a synergistic effect. Since the doping concentrations of both of the multiple elements can be increased, the resistance of the Sn-doped GaN layer can be further reduced.

[0054] The source of tin is not limited to metallic tin, but may be other tin compounds, or tin may be added to metallic gallium.

[0055] The heating temperatures of the heaters 30, 31, and 32 may be equal to each other. For example, the heating temperatures of the heaters 30, 31, and 32 may be set to a temperature sufficient for gallium nitride crystal growth (700°C or higher and 1100°C or lower). In this case, the heaters 30, 31, and 32 may be integrated into one or two heaters. This makes it possible to simplify the heater structure.

[0056] The flow directions of the first source gas G1, the second source gas G2, and the third source gas G3 with respect to the surface of the wafer 13 are not limited to being substantially perpendicular, and may be various. For example, the flow direction may be parallel to the surface of the wafer 13. When the flow direction is closer to parallel, it is easier to form a rate difference or a concentration difference between the upstream and downstream than when the flow direction is perpendicular. This makes it easier to control the period of variation of the tin concentration distribution in the depth direction due to the rotation (rotation and revolution) of the wafer.

[0057] The gas supplied to the inlets of the first raw material gas supply pipe 21 and the third raw material gas supply pipe 23 is not limited to hydrogen chloride (HCl) gas. For example, it may be a gas containing Cl, such as chlorine (Cl2) gas, or a gas containing other halogen elements, such as F or Br.

[0058] The scope of application of the technology described in this specification is not limited to gallium nitride. It can be applied to the crystal growth of various compound semiconductors that can use tin as an impurity. For example, it may be applied to AlGaN (aluminum gallium nitride), AlN (aluminum nitride), InN (indium nitride), InGaN (indium gallium nitride), or mixed crystals thereof.

[0059] The numbers and arrangements of the first source gas supply pipe 21 to the third source gas supply pipe 23 described in this specification are merely examples and are not limited to this embodiment. For example, the first source gas supply pipe 21 and the third source gas supply pipe 23 may be integrated.

[0060] The heating temperatures of the wafer 13, the metal gallium 43, and the metal tin 47 are merely examples.

[0061] Although the first source gas G1 is a gas containing gallium chloride, the present invention is not limited to this. The first source gas G1 may be a gas having any chemical composition as long as it contains gallium. For example, the first source gas G1 may be a gas containing gallium trichloride (GaCl3). Also, for example, the first source gas G1 may be a gas containing simple gallium.

[0062] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

[0063] Aspects of the present technology are listed below. [Aspect 1] A method for producing gallium nitride using a vapor phase growth method that does not use an organic metal as a gallium raw material, supplying a first source gas containing gallium into a reaction vessel in which a substrate is placed; supplying a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel; supplying a third source gas containing tin into the reaction vessel; Equipped with the step of supplying the first source gas, the step of supplying the second source gas, and the step of supplying the third source gas are performed at a temperature of the substrate within a range of 700° C. or more and 1100° C. or less; How gallium nitride is produced. [Aspect 2] 2. The method for producing gallium nitride according to aspect 1, wherein the step of supplying the first source gas, the step of supplying the second source gas, and the step of supplying the third source gas are performed while the temperature of the substrate is in the range of 800° C. or higher and 950° C. or lower. [Aspect 3] the first source gas is a gas containing gallium chloride, the second source gas is a gas containing ammonia, 3. The method for producing gallium nitride according to aspect 1 or 2, wherein the third source gas is a gas containing tin chloride. [Aspect 4] a ratio of a molar flow rate of the tin chloride contained in the third source gas to a total molar flow rate of the gallium chloride contained in the first source gas and the tin chloride contained in the third source gas is 1×10 -3The above is the method for producing gallium nitride according to aspect 3. [Aspect 5] The method for producing gallium nitride according to any one of aspects 1 to 4, wherein the substrate is rotated about an axis perpendicular to a surface of the substrate. [Aspect 6] The method for producing gallium nitride according to any one of aspects 1 to 5, further comprising the step of supplying a fourth source gas containing at least one of silicon and germanium into the reaction vessel simultaneously with the supply of the third source gas. [Aspect 7] A gallium nitride vapor phase growth apparatus for use in a vapor phase growth method that does not use an organic metal as a gallium source, A reaction vessel; a substrate holder disposed within the reaction vessel; a first source gas supply pipe for supplying a first source gas containing gallium into the reaction vessel; a second source gas supply pipe for supplying a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel; a third source gas supply pipe for supplying a third source gas containing tin into the reaction vessel; a first heating unit that heats the temperature of the substrate held by the substrate holder to a temperature in the range of 700° C. to 1100° C.; A gallium nitride vapor phase growth apparatus equipped with a [Aspect 8] 8. The gallium nitride vapor phase growth apparatus according to aspect 7, wherein the first heating unit heats the substrate held by the substrate holder to a temperature in the range of 800° C. to 950° C. [Aspect 9] Hydrogen chloride gas or chlorine gas is supplied to the inlets of the first source gas supply pipe and the third source gas supply pipe; The first source gas containing gallium chloride is discharged from an outlet of the first source gas supply pipe, 9. The gallium nitride vapor phase growth apparatus according to aspect 7 or 8, wherein the third source gas containing tin chloride is discharged from an outlet of the third source gas supply pipe. [Aspect 10] a ratio of a molar flow rate of the tin chloride contained in the third source gas to a total molar flow rate of the gallium chloride contained in the first source gas and the tin chloride contained in the third source gas is 1×10 -3 The above is the vapor phase growth apparatus for gallium nitride according to embodiment 9. [Aspect 11] 11. The gallium nitride vapor phase growth apparatus according to any one of aspects 7 to 10, wherein the substrate holder is configured to be capable of rotating the substrate about an axis perpendicular to a surface of the substrate. [Aspect 12] the third source gas supply pipe is configured so that metallic tin can be disposed on a supply path thereof, The gallium nitride vapor phase growth apparatus according to any one of aspects 7 to 11, further comprising a second heating unit capable of heating the metallic tin disposed in the third source gas supply pipe. [Aspect 13] the first source gas supply pipe is configured so that a solid part containing gallium can be disposed on a supply path of the first source gas supply pipe, Further comprising a third heating unit capable of heating the solid portion disposed thereon; The heating temperatures by the first heating unit, the second heating unit, and the third heating unit are equal to each other. 13. An apparatus for vapor phase growth of gallium nitride according to embodiment 12. [Aspect 14] a distance between an end position of the outlet side of the first source gas supply pipe and the third source gas supply pipe and the substrate holding part is greater than a distance between an end position of the outlet side of the second source gas supply pipe and the substrate holding part; 14. The vapor phase growth apparatus for gallium nitride according to any one of aspects 7 to 13. [Aspect 15] Tin concentration is 1×10 19 The above is a gallium nitride substrate that functions as an n-type semiconductor, The concentration distribution of tin in a direction perpendicular to the surface of the gallium nitride substrate is approximately constant in the depth direction. Gallium nitride substrate. [Aspect 16] 16. The gallium nitride substrate according to embodiment 15, wherein the activation rate of doped tin is 70% or more. [Aspect 17] 17. The gallium nitride substrate of embodiment 15 or 16, wherein the tin concentration varies periodically in the depth direction. [Aspect 18] 18. The gallium nitride substrate according to any one of aspects 15 to 17, wherein satellite peaks reflecting periodicity of tin concentration in the depth direction are present around a reflection peak obtained in 2θ-ω scanning by X-ray diffraction. [Aspect 19] Tin concentration is 1×10 19 That's all. Resistivity is 1×10 -3 19. The gallium nitride substrate of any one of aspects 15-18, having a resistivity of Ω·cm or less. [Aspect 20] 20. A gallium nitride substrate according to any one of aspects 15 to 19, wherein the lattice constant calculated based on the main peak angle obtained in 2θ-ω scanning by X-ray diffraction is 0.05% or more larger than the lattice constant of a gallium nitride crystal not doped with tin. [Explanation of symbols]

[0064] 1: Vapor phase growth apparatus 10: Reaction vessel 11: Wafer holder 13: Wafer 20: Source gas supply pipe section 21: First source gas supply pipe 22: Second source gas supply pipe 23: Third source gas supply pipe 30-32: Heater G1: First source gas G2: Second source gas G3: Third source gas

Claims

1. A method for producing gallium nitride using a vapor phase growth method that does not use an organic metal as a gallium raw material, supplying a first source gas containing gallium into a reaction vessel in which a substrate is placed; supplying a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel; supplying a third source gas containing tin into the reaction vessel; Equipped with the step of supplying the first source gas, the step of supplying the second source gas, and the step of supplying the third source gas are performed at a temperature of the substrate within a range of 700° C. or more and 1100° C. or less; How gallium nitride is produced.

2. 2. The method for producing gallium nitride according to claim 1, wherein the step of supplying the first source gas, the step of supplying the second source gas, and the step of supplying the third source gas are performed while the temperature of the substrate is in the range of 800° C. or more and 950° C. or less.

3. the first source gas is a gas containing gallium chloride, the second source gas is a gas containing ammonia, 3. The method for producing gallium nitride according to claim 2, wherein the third source gas is a gas containing tin chloride.

4. a ratio of a molar flow rate of the tin chloride contained in the third source gas to a total molar flow rate of the gallium chloride contained in the first source gas and the tin chloride contained in the third source gas is 1×10 －３ The method for producing gallium nitride according to claim 3 .

5. The method for producing gallium nitride according to claim 4 , wherein the substrate is rotated about an axis perpendicular to a surface of the substrate.

6. 6. The method for producing gallium nitride according to claim 1, further comprising the step of supplying a fourth source gas containing at least one of silicon and germanium into the reaction vessel simultaneously with the supply of the third source gas.

7. A gallium nitride vapor phase growth apparatus for use in a vapor phase growth method that does not use an organic metal as a gallium source, A reaction vessel; a substrate holder disposed within the reaction vessel; a first source gas supply pipe for supplying a first source gas containing gallium into the reaction vessel; a second source gas supply pipe for supplying a second source gas containing nitrogen and reacting with the first source gas into the reaction vessel; a third source gas supply pipe for supplying a third source gas containing tin into the reaction vessel; a first heating unit that heats the substrate held by the substrate holder to a temperature in the range of 700° C. to 1100° C.; A gallium nitride vapor phase growth apparatus equipped with a

8. 8. The gallium nitride vapor phase growth apparatus according to claim 7, wherein the first heating section heats the substrate held by the substrate holder to a temperature in the range of 800° C. to 950° C.

9. Hydrogen chloride gas or chlorine gas is supplied to the inlets of the first source gas supply pipe and the third source gas supply pipe; The first source gas containing gallium chloride is discharged from an outlet of the first source gas supply pipe, 9. The gallium nitride vapor phase growth apparatus according to claim 8, wherein the third source gas containing tin chloride is discharged from an outlet of the third source gas supply pipe.

10. a ratio of a molar flow rate of the tin chloride contained in the third source gas to a total molar flow rate of the gallium chloride contained in the first source gas and the tin chloride contained in the third source gas is 1×10 －３ 10. The vapor phase growth apparatus for gallium nitride according to claim 9.

11. 11. The gallium nitride vapor phase growth apparatus according to claim 10, wherein the substrate holder is configured to be capable of rotating the substrate about an axis perpendicular to a surface of the substrate.

12. the third source gas supply pipe is configured so that metallic tin can be disposed on a supply path thereof, 12. The gallium nitride vapor phase growth apparatus according to claim 11, further comprising a second heating unit capable of heating the metallic tin disposed in the third source gas supply pipe.

13. the first source gas supply pipe is configured so that a solid portion containing gallium can be disposed on a supply path of the first source gas supply pipe, Further comprising a third heating unit capable of heating the solid portion disposed thereon; The heating temperatures by the first heating unit, the second heating unit, and the third heating unit are equal to each other. The apparatus for vapor phase growth of gallium nitride according to claim 12.

14. a distance between an end position on the outlet side of the first source gas supply pipe and the third source gas supply pipe and the substrate holding part is greater than a distance between an end position on the outlet side of the second source gas supply pipe and the substrate holding part; 8. The vapor phase growth apparatus for gallium nitride according to claim 7.

15. Tin concentration is 1×10 １９ The above is a gallium nitride substrate that functions as an n-type semiconductor, The concentration distribution of tin in a direction perpendicular to the surface of the gallium nitride substrate is approximately constant in the depth direction. Gallium nitride substrate.

16. 16. The gallium nitride substrate according to claim 15, wherein the activation rate of the doped tin is 70% or more.

17. The gallium nitride substrate according to claim 16 , wherein the tin concentration varies periodically in the depth direction.

18. 18. The gallium nitride substrate according to claim 17, wherein satellite peaks reflecting periodicity of tin concentration in the depth direction are present around a reflection peak obtained in 2θ-ω scanning by X-ray diffraction.

19. Tin concentration is 1×10 １９ That's all. Resistivity is 1 x 10 －３ The gallium nitride substrate according to claim 15 , having a resistivity of Ω·cm or less.

20. 16. The gallium nitride substrate according to claim 15, wherein the lattice constant calculated based on the main peak angle obtained in 2θ-ω scanning by X-ray diffraction is 0.05% or more larger than the lattice constant of a gallium nitride crystal not doped with tin.

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