JP2019153660A - Group III nitride semiconductor device manufacturing method and power device - Google Patents

Abstract

To provide a Group III nitride semiconductor device manufacturing method capable of forming a Group III nitride semiconductor layer with excellent crystallinity by relieving stress during production and to provide a power device.SOLUTION: In the manufacturing method, a substrate 110 having a first surface 110a having a root mean square roughness (RMS) of 2 nm or more and 10 nm or less is used. By converting a nitrogen gas into plasma and supplying it to the substrate 110 and supplying an organometallic gas containing In without converting it into plasma to the substrate 110, an InN layer A1 is formed on the first surface 110a of the substrate 110. A first buffer layer 120 is grown on the InN layer A1.SELECTED DRAWING: Figure 3

Description

  The technical field of the present specification relates to a method for manufacturing a group III nitride semiconductor device and a power device.

  In a group III nitride semiconductor typified by GaN, the band gap changes from 0.6 eV to 6 eV by changing its composition. Therefore, group III nitride semiconductors are applied to light-emitting elements, laser diodes, light-receiving elements and the like corresponding to a wide range of wavelengths from near infrared to deep ultraviolet.

  Further, the group III nitride semiconductor has a high breakdown electric field strength and a high melting point. Therefore, the group III nitride semiconductor is expected as a material for a semiconductor device for high output, high frequency, and high temperature that replaces a GaAs semiconductor. For this reason, HEMT elements and the like have been researched and developed.

  As a method for epitaxially growing a group III nitride semiconductor, for example, there is a metal organic chemical vapor deposition method (MOCVD method). In the MOCVD method, a large amount of ammonia gas is used. Therefore, it is necessary to provide an abatement apparatus for excluding ammonia in the MOCVD furnace. In addition, the running cost of ammonia is high. Then, a semiconductor layer is formed by a reaction between the organometallic gas and ammonia. In order to cause this reaction, it is necessary to raise the substrate temperature. When the substrate temperature is high, it is difficult to grow an InGaN layer having a high In concentration with high quality. Also, warpage is likely to occur due to the difference in thermal expansion between the growth substrate and the semiconductor layer.

  Moreover, as a method for epitaxially growing a group III nitride semiconductor, for example, a molecular beam epitaxy method (MBE method) can be mentioned. In the MBE method, a group III nitride semiconductor can be grown at a low growth temperature. However, the growth rate is slow in the RF-MBE method using a radical source. That is, the RF-MBE method is not suitable for mass production. In the MBE method using ammonia gas, since a large amount of ammonia gas is used, the manufacturing cost is high.

Japanese Patent Laying-Open No. 2015-099866

  Accordingly, the present inventors have developed a REMOCVD (Radial Enhanced Metal Organic Vapor Deposition) method (see Patent Document 1). When forming a group III nitride semiconductor layer mainly composed of Al or Ga, the film is formed at a relatively high temperature. For this reason, a stress is generated due to a difference in thermal expansion coefficient between the substrate and the semiconductor layer. Thus, since the group III nitride semiconductor layer receives stress from the substrate during manufacture, it is not easy to grow a high-quality crystal.

  The technique of this specification has been made to solve the problems of the conventional techniques described above. The problem is to provide a method for producing a group III nitride semiconductor element and a power device capable of forming a group III nitride semiconductor layer having excellent crystallinity by relaxing stress during production.

  In the method for manufacturing a group III nitride semiconductor device according to the first aspect, a substrate having a first surface having a root mean square roughness (RMS) of 2 nm to 10 nm is used. The InN layer is formed on the first surface of the substrate by supplying nitrogen gas into the plasma and supplying it to the substrate and supplying the organometallic gas containing In to the substrate without converting it into plasma. A group III nitride semiconductor layer is grown on the InN layer.

  In this method for manufacturing a group III nitride semiconductor device, an InN layer that easily grows in an island shape is preferably grown on a growth substrate. Therefore, the crystallinity of the group III nitride semiconductor layer grown on the InN layer is excellent.

  The present specification provides a method for manufacturing a group III nitride semiconductor element and a power device capable of forming a group III nitride semiconductor layer having excellent crystallinity by relaxing stress during manufacturing.

It is a figure which shows schematic structure of the MIS type | mold semiconductor element in 1st Embodiment. It is a figure which shows schematic structure of the manufacturing apparatus of the group III nitride semiconductor element in 1st Embodiment. It is a figure for demonstrating the manufacturing method of the group III nitride semiconductor element in 1st Embodiment. It is a graph (three-dimensional display) which shows the intensity | strength of the X-ray diffraction of the GaN layer on a Si (111) board | substrate. It is a graph (two-dimensional display) which shows the intensity | strength of the X-ray diffraction of the GaN layer on a Si (111) board | substrate.

  Hereinafter, specific embodiments will be described with reference to the drawings, taking as an example a method for manufacturing a group III nitride semiconductor device and a power device.

(First embodiment)
1. MIS Semiconductor Device FIG. 1 is a schematic configuration diagram of a power device 100 according to the first embodiment. The power device 100 is a MIS type semiconductor element. As shown in FIG. 1, the power device 100 includes a substrate 110, a first buffer layer 120, a second buffer layer 130, a GaN layer 140, an AlGaN layer 150, an insulating film 160, a source electrode S1, It has a gate electrode G1 and a drain electrode D1.

  The substrate 110 is a Si (111) substrate. The substrate 110 has a first surface 110a. The first surface 110a is a main surface for growing a semiconductor layer. The root mean square roughness (RMS) of the first surface 110a of the substrate 110 is not less than 2 nm and not more than 10 nm. The root mean square roughness (RMS) corresponds to the surface roughness Rq of JIS. The film thickness of the first buffer layer 120 is not less than 5 nm and not more than 20 nm.

  As will be described later, the first surface 110a of the substrate 110 is relatively rough. Therefore, a GaN layer having excellent crystallinity can be grown.

  The first buffer layer 120 is a first group III nitride semiconductor layer. The first buffer layer 120 is, for example, an InGaN layer that slightly contains In. The first buffer layer 120 contains In. This is because In is slightly mixed into the first buffer layer 120 during manufacturing. The first buffer layer 120 is formed on the first surface 110 a of the substrate 110.

  The second buffer layer 130 is a second group III nitride semiconductor layer. The second buffer layer 130 is, for example, a GaN layer. The second buffer layer 130 is formed on the first buffer layer 120.

  The source electrode S1 and the drain electrode D1 are formed on the AlGaN layer 150. There is an insulating film 160 between the gate electrode G1 and the groove 151 of the AlGaN layer 150.

2. Group III Nitride Semiconductor Device Manufacturing Apparatus FIG. 2 is a schematic configuration diagram of a group III nitride semiconductor element manufacturing apparatus 1000 according to this embodiment. The manufacturing apparatus 1000 is an apparatus that converts a gas containing at least nitrogen gas into plasma and supplies a plasma product to the growth substrate, and supplies an organometallic gas containing a group III metal to the growth substrate without converting it into plasma.

  The manufacturing apparatus 1000 includes a furnace main body 1001, a shower head electrode 1100, a susceptor 1200, a heater 1210, a first gas supply pipe 1300, a gas introduction chamber 1410, a second gas supply pipe 1420, a metal A mesh 1500, an RF power source 1600, a matching box 1610, a first gas supply unit 1710, a second gas supply unit 1810, gas containers 1910, 1920, 1930, thermostats 1911, 1921, 1931, Mass flow controllers 1720, 1820, 1830, and 1840. Moreover, the manufacturing apparatus 1000 has an exhaust port (not shown).

  The shower head electrode 1100 is a first electrode to which a periodic potential is applied. The shower head electrode 1100 is made of, for example, stainless steel. Of course, other metals may be used. The shower head electrode 1100 is a flat electrode. The shower head electrode 1100 is provided with a plurality of through holes (not shown) penetrating from the front surface to the back surface. The plurality of through holes communicate with the gas introduction chamber 1410 and the second gas supply pipe 1420. For this reason, the second gas supplied from the gas introduction chamber 1410 to the inside of the furnace main body 1001 is preferably converted into plasma. The RF power source 1600 is a potential applying unit that applies a high-frequency potential to the shower head electrode 1100.

  The susceptor 1200 is a substrate support unit for supporting the substrate 110. The material of the susceptor 1200 is, for example, graphite. Other conductors may be used. Here, the substrate 110 is a growth substrate for growing a group III nitride semiconductor.

  The first gas supply pipe 1300 is for supplying the first gas to the susceptor 1200. Actually, the first gas is supplied to the substrate 110 supported by the susceptor 1200. Here, the first gas is an organometallic gas containing a group III metal. Moreover, the other carrier gas may be included. The first gas supply pipe 1300 has a ring-shaped ring portion 1310. The ring portion 1310 of the first gas supply pipe 1300 is provided with twelve through holes (not shown) inside the ring portion 1310. These through holes are jet outlets from which the first gas is jetted. Therefore, the first gas is ejected toward the inside of the ring portion 1310. As will be described later, the first gas supply pipe 1300 is located at a position away from the plasma generation region.

  The second gas supply pipe 1420 is for supplying the second gas to the susceptor 1200. Actually, the second gas is introduced into the gas introduction chamber 1410 and the furnace main body 1001 and the second gas is supplied to the substrate 110 supported by the susceptor 1200. The second gas supply pipe 1420 supplies the second gas into the furnace body 1001. Here, the second gas supply pipe 1420 supplies a mixed gas of nitrogen gas and hydrogen gas as the second gas. The second gas may be only nitrogen gas. The gas introduction chamber 1410 is for temporarily storing a mixed gas of nitrogen gas and hydrogen gas and supplying the mixed gas to the through hole of the showerhead electrode 1100.

  The metal mesh 1500 is for capturing charged particles. The metal mesh 1500 is made of stainless steel, for example. Of course, other metals may be used. The metal mesh 1500 is disposed at a position between the shower head electrode 1100 and the susceptor 1200. Therefore, as described later, charged particles generated in the plasma generation region can be prevented from moving toward the substrate 110 supported by the susceptor 1200. In addition, the metal mesh 1500 is disposed at a position between the shower head electrode and the ring part 1310 of the first gas supply pipe 1300. Therefore, it is possible to suppress the charged particles from colliding with the organometallic molecules including the group III metal ejected from the first gas supply pipe 1300. The metal mesh 1500 is arranged by shifting a large number of sheets. That is, the linear part of the second mesh is arranged at the position of the opening of the first mesh. Therefore, light that travels linearly cannot pass through the metal mesh 1500. That is, the metal mesh 1500 does not pass electrons, ions, and light, but allows neutral radicals to pass.

  The furnace body 1001 accommodates at least a shower head electrode 1100, a susceptor 1200, a ring portion 1310 of the first gas supply pipe 1300, and a metal mesh 1500. The furnace body 1001 is made of stainless steel, for example. The furnace body 1001 may be a conductor other than the above.

  The furnace body 1001, the metal mesh 1500, and the first gas supply pipe 1300 are conductive members, and all are grounded. Therefore, when a potential is applied to the showerhead electrode 1100, a voltage is applied between the showerhead electrode 1100, the furnace body 1001, the metal mesh 1500, and the first gas supply pipe 1300. Then, it is considered that electric discharge occurs between at least one of the furnace body 1001, the metal mesh 1500, and the first gas supply pipe 1300 and the shower head electrode 1100. A high-frequency and high-intensity electric field is formed immediately below the showerhead electrode 1100. Therefore, the position immediately below the shower head electrode 1100 is a plasma generation region.

Here, the second gas, that is, the mixed gas of nitrogen gas and hydrogen gas is converted into plasma in this plasma generation region. A plasma product is generated in the plasma generation region. The plasma products in this case are nitrogen radicals, hydrogen radicals, hydrogen nitride compounds, electrons, and other ions. Here, the hydrogen nitride-based compound includes NH, NH ₂ , NH ₃ , their excited states, and others.

  Moreover, the shower head electrode 1100 and the susceptor 1200 are sufficiently separated. The distance between the showerhead electrode 1100 and the susceptor 1200 is 40 mm or more and 200 mm or less. More preferably, it is 40 mm or more and 150 mm or less. If the distance between the showerhead electrode 1100 and the susceptor 1200 is short, the plasma generation region may spread to the susceptor 1200. If the distance between the showerhead electrode 1100 and the susceptor 1200 is 40 mm or more, there is almost no possibility that the plasma generation region extends to the susceptor 1200. Therefore, it is possible to suppress the charged particles from reaching the substrate 110. Further, when the distance between the showerhead electrode 1100 and the susceptor 1200 is large, nitrogen radicals, hydrogen nitride-based compounds, and the like are difficult to reach the substrate 110 held by the susceptor 1200. These distances depend on the size of the plasma generation region and other plasma conditions.

  The shower head electrode 1100 is disposed at a position farther from the through hole of the ring portion 1310 of the first gas supply pipe 1300 when viewed from the susceptor 1200. The distance between the showerhead electrode 1100 and the through hole of the ring portion 1310 of the first gas supply pipe 1300 is 30 mm or more and 190 mm or less. More preferably, it is 30 mm or more and 140 mm or less. This is because charged particles are prevented from being mixed into the first gas, and nitrogen radicals, hydrogen nitride-based compounds, and the like can easily reach the substrate 110. Therefore, the semiconductor layer is stacked on the substrate 110 by the second gas that has been converted to plasma and the first gas that has not been converted to plasma. These distances depend on the size of the plasma generation region and other plasma conditions.

  The heater 1210 is for heating the substrate 110 supported by the susceptor 1200 via the susceptor 1200.

  The mass flow controllers 1720, 1820, 1830, and 1840 are for controlling the flow rate of each gas. The thermostats 1911, 1921, and 1931 are filled with antifreeze liquids 1912, 1922, and 1932. Further, the gas containers 1910, 1920, and 1930 are containers for storing an organometallic gas containing a group III metal. The gas containers 1910, 1920, and 1930 contain trimethyl gallium, trimethyl indium, and trimethyl aluminum, respectively. Of course, organic metal gas containing other group III metals such as triethylgallium may be used.

3. Manufacturing conditions of manufacturing apparatus Table 1 shows manufacturing conditions in the manufacturing apparatus 1000. The numerical ranges given in Table 1 are only a guide and are not necessarily limited to these numerical ranges. The RF power is in the range of 100 W to 1000 W. The frequency of the periodic potential applied to the shower head electrode 1100 by the RF power source 1600 is in the range of 30 MHz to 300 MHz. The substrate temperature is in the range of 0 ° C. or higher and 1000 ° C. or lower. The substrate temperature may be room temperature or higher. The internal pressure of the manufacturing apparatus 1000 is in the range of 10 Pa to 1000 Pa.

[Table 1]
RF power 100W or more and 1000W or less Frequency 30MHz or more 300MHz or less Substrate temperature 0 ℃ or more 1000 ℃ or less Internal pressure 10Pa or more 1000Pa or less

4). Semiconductor Device Manufacturing Method The semiconductor device manufacturing method according to the present embodiment grows a semiconductor layer by a REMOCVD (Radial Enhanced Metal Organic Vapor Deposition) method. That is, a semiconductor layer is grown using the manufacturing apparatus 1000 of this embodiment. In the REMOCVD method, a first gas containing a Group III metal is supplied to a growth substrate without being converted to plasma, and a second gas containing at least nitrogen gas is converted to plasma and supplied to the growth substrate to grow a semiconductor layer. Is the method.

4-1. Substrate Preparation Step A substrate 110 having a first surface 110a having a root mean square roughness (RMS) of 2 nm to 10 nm is prepared. As the substrate 110, for example, a Si (111) substrate can be used. Other substrates may also be used. In order to use the roughened substrate 110, for example, the polishing of the first surface 110a of the substrate 110 may be stopped halfway in the final finishing stage of the substrate 110. Alternatively, after polishing, irregularities may be formed by etching or the like.

4-2. Substrate Cleaning The substrate 110 is placed inside the manufacturing apparatus 1000, and the substrate temperature is raised to about 900 ° C. while supplying hydrogen gas. As a result, the surface of the substrate 110 is reduced and the surface of the substrate 110 is cleaned. The substrate temperature may be higher than this. Note that the substrate 110 may be cleaned with acetone, isopropyl alcohol, pure water, HF, or the like before the substrate 110 is placed inside the manufacturing apparatus 1000.

4-3. Next, the RF power source 1610 is turned on. Then, a mixed gas of nitrogen gas and hydrogen gas is supplied from the second gas supply pipe 1420. The mixed gas supplied into the furnace main body 1001 from the through hole of the shower head electrode 1100 is converted into plasma immediately below the shower head electrode 1100. Therefore, a plasma generation region is generated immediately below the showerhead electrode 1100. At this time, nitrogen radicals and hydrogen radicals are generated. Then, it is considered that a nitrogen radical and a hydrogen radical react to produce a hydrogen nitride compound. Electrons and other charged particles are also generated.

  The radical mixed gas containing these nitrogen radicals, hydrogen radicals, hydrogen nitride-based compounds, electrons, and other charged particles is sent toward the substrate 110. The generation location of this radical mixed gas is directly under the shower head electrode 1100. Since the distance from the showerhead electrode 1100 to the substrate 110 is sufficiently wide, charged particles such as electrons and ions in the radical mixed gas hardly reach the substrate 110. In addition, charged particles are easily captured by the metal mesh 1500. Therefore, it is considered that what is supplied toward the substrate 110 is a hydrogen nitride-based compound in addition to nitrogen radicals and hydrogen radicals. Compared with normal ammonia, the reactivity of these nitrogen radicals and hydrogen nitride compounds is high. Therefore, the semiconductor layer can be epitaxially grown at a lower temperature than conventional.

  On the other hand, a group III metal organometallic gas is supplied from the ring portion 1310 of the first gas supply pipe 1300. For example, trimethylgallium, trimethylindium, and trimethylaluminum are listed. These gases are entrained in the radical mixed gas toward the substrate 110 and supplied to the substrate 110. The organometallic gas of Group III metal is supplied to the substrate 110 without being converted into plasma.

4-3-1. InN layer forming step The substrate temperature is set in the range of 0 ° C to 100 ° C. For example, it may be room temperature. TMI (trimethylindium) is caused to flow from the ring portion 1310 of the first gas supply pipe 1300. On the other hand, nitrogen gas is allowed to flow from the showerhead electrode 1100 and the nitrogen gas is turned into plasma. Hydrogen gas is not flowed. Thereby, the InN layer A1 is formed on the first surface 110a of the substrate 110 (see FIG. 3). The thickness of the InN layer A1 is not less than 0.2 nm and not more than 1 nm. That is, a few atomic layers.

4-3-2. First buffer layer forming step (first group III nitride semiconductor layer forming step)
As shown in FIG. 3, the first buffer layer 120 is formed on the InN layer A1 without decomposing the InN layer A1. The first buffer layer 120 is, for example, an InGaN layer slightly containing In. The substrate temperature is 300 ° C. or higher and 500 ° C. or lower. TMG (trimethyl gallium) is caused to flow from the ring portion 1310 of the first gas supply pipe 1300. On the other hand, nitrogen gas is allowed to flow from the showerhead electrode 1100 and the nitrogen gas is turned into plasma. As a result, the first buffer layer 120 is formed on the InN layer A1 (see FIG. 3). The first buffer layer 120 substantially fills the unevenness of the first surface 110 a of the substrate 110. The film thickness of the first buffer layer 120 is not less than 5 nm and not more than 20 nm.

4-3-3. Second buffer layer forming step (second group III nitride semiconductor layer forming step)
Next, the second buffer layer 130 is formed on the first buffer layer 120. The second buffer layer 130 is a GaN layer, for example. The substrate temperature is 600 ° C. or higher and 900 ° C. or lower. For that purpose, TMG (trimethylgallium) is caused to flow from the ring portion 1310 of the first gas supply pipe 1300. On the other hand, a mixed gas of nitrogen gas and hydrogen gas is allowed to flow from the showerhead electrode 1100 and the mixed gas is turned into plasma. Since the substrate temperature in this step is high, the InN layer A1 is decomposed and evaporated while the second buffer layer 130 is grown. As a result, the first buffer layer 120 is formed on the substrate 110 and the second buffer layer 130 is formed on the first buffer layer 120. Further, it is considered that In is mixed into the first buffer layer 120 after the InN layer A1 is decomposed.

4-3-4. GaN Layer Formation Step A GaN layer 140 is grown on the second buffer layer 130. The substrate temperature is 600 ° C. or higher and 900 ° C. or lower. For that purpose, TMG (trimethylgallium) is caused to flow from the ring portion 1310 of the first gas supply pipe 1300. On the other hand, a mixed gas of nitrogen gas and hydrogen gas is allowed to flow from the showerhead electrode 1100 and the mixed gas is turned into plasma.

4-3-5. AlGaN layer forming step An AlGaN layer 150 is grown on the GaN layer 140. The substrate temperature is 600 ° C. or higher and 900 ° C. or lower. For this purpose, TMG (trimethylgallium) and TMA (trimethylaluminum) are allowed to flow from the ring portion 1310 of the first gas supply pipe 1300. On the other hand, a mixed gas of nitrogen gas and hydrogen gas is allowed to flow from the showerhead electrode 1100 and the mixed gas is turned into plasma.

4-4. Next, a groove 151 is formed in the AlGaN layer 150 by etching such as ICP.

4-5. Insulating Film Formation Step Next, the insulating film 160 is formed in the trench 151. The insulating film 160 is, for example, SiO ₂ . Of course, other materials may be used.

4-6. Electrode Formation Step Next, the source electrode S1 and the drain electrode D1 are formed on the AlGaN layer 150. Further, the gate electrode G1 is formed at the location of the trench 151 with the insulating film 160 interposed therebetween. Note that the source electrode S1 and the drain electrode D1 may be formed before the insulating film 160 is formed. Thus, the MIS type semiconductor element 100 is manufactured.

5. Technical significance of this embodiment In this embodiment, in order to relieve the stress between the substrate and the GaN layer above it, an InN layer of several atomic layers is formed between the substrate and the GaN layer. This atomic layer is decomposed during manufacture. The InN layer is easily decomposed under high temperature conditions. Therefore, the substrate temperature when forming the InN layer is 0 ° C. or higher and 100 ° C. or lower. This temperature is sufficiently lower than the film formation temperature of the GaN layer. Therefore, the kinetic energy of In when forming the InN layer is smaller than the kinetic energy of Ga when forming the GaN layer.

  When forming the GaN layer, the Ga particles suitably move around the surface of the substrate. This is presumably because Ga particles collide with the substrate with relatively high kinetic energy. On the other hand, In particles collide with the substrate with relatively low kinetic energy. Therefore, it is considered that In particles do not move much on the substrate. Actually, the InN layer grows in an island shape on the surface of the substrate.

  In this embodiment, the surface of the substrate is roughened in order to increase the starting point at which the InN layer grows in an island shape from the point where In was accidentally attached. Thereby, it is considered that the surface area of the substrate is effectively increased and the atomic force is also increased. Therefore, it is considered that a very thin InN layer can be formed relatively uniformly.

  It is also conceivable that the thin InN layer relaxes the lattice constant mismatch between the Si (111) substrate and GaN. Therefore, even after the InN layer is decomposed, stress is not so much generated between the Si (111) substrate and GaN.

6). Modification 6-1. Kind of Device The manufacturing method of the group III nitride semiconductor device of this embodiment is not limited to the MIS type power device 100 and can be applied. Moreover, it can be applied when manufacturing other semiconductor elements other than power devices.

6-2. Through-hole of ring part In the present embodiment, the first gas supply pipe 1300 has a through-hole inside the ring part 1310. However, the position of the through-hole may be set to the inside of the ring and downward. The angle formed by the surface including the ring portion 1310 and the direction of the opening of the through hole is, for example, 45 °. For example, the angle may be changed within a range of 0 ° to 60 °. Of course, this angle also depends on the diameter of the ring portion 1310 and the distance between the ring portion 1310 and the susceptor 1200. Moreover, the number of through-holes should just be one or more. Of course, it is preferable that through holes are formed in the ring portion 1310 at equal intervals.

7). Summary of Embodiment In the method for manufacturing a group III nitride semiconductor device of this embodiment, an InN layer A1 corresponding to several atomic layers is formed, and a GaN layer is formed thereon. The InN layer A1 is easily formed in an island shape. Therefore, the first surface 110a of the substrate 110 is rougher than the surface of the conventional substrate. The root mean square roughness (RMS) of the first surface 110a of the substrate 110 is not less than 2 nm and not more than 10 nm. Therefore, the InN layer A1 is uniformly formed with a thin film thickness on the surface of the first surface 110a of the substrate 110.

1. Sample Preparation Six types of Si (111) substrates were prepared. Then, an InN layer of several atomic layers is formed on each Si (111) substrate, a first buffer layer 120 (GaN layer) is formed thereon, and a second buffer layer 130 (GaN layer) is formed thereon. Formed. Conditions other than the surface roughness of the substrate are common to all samples. Samples are summarized in Table 2. Here, in the off-angle substrate, the surface is inclined by about 1 ° from the (111) plane.

[Table 2]
Sample Substrate type Surface roughness Example 1 Si (111) 2.5 nm
Example 2 Si (111) 3.5 nm
Example 3 Si (111) 5 nm
Example 4 Si (111) 10 nm
Comparative Example 1 Si (111) Off Angle Comparative Example 2 Si (111) No Off Angle

2. Results X-ray diffraction was performed on the samples. FIG. 4 is a graph (three-dimensional display) showing the intensity of X-ray diffraction of the GaN layer on the Si (111) substrate. FIG. 5 is a graph (two-dimensional display) showing the intensity of X-ray diffraction of the GaN layer on the Si (111) substrate. The horizontal axis of FIGS. 4 and 5 is 2θ / θ (degree). The vertical axis in FIGS. 4 and 5 is intensity (cps).

  In FIGS. 4 and 5, Example 1-3 and Comparative Examples 1 and 2 are plotted. In Example 1-3, the strength is 400 cps or more. In Comparative Examples 1 and 2, the strength is 150 cps or less. Moreover, although not plotted in FIG. 4 and FIG. 5, the strength of Example 4 is about 250 cps. Therefore, the root mean square roughness (RMS) of the first surface 110a of the substrate 110 is preferably 2 nm or more and 10 nm or less.

  Thus, by laminating an InN layer of several atomic layers on a substrate having a rough surface, the upper GaN layer can be laminated with good crystallinity. In FIGS. 4 and 5, the peak of the InN layer was not observed. Since the InN layer is decomposed during film formation, the stress from the substrate is not easily transmitted to the group III nitride semiconductor. The stress is sufficiently relaxed between the first buffer layer 120 and the substrate 110.

A. Supplementary Note In the method for manufacturing a group III nitride semiconductor device according to the first aspect, a substrate having a first surface having a root mean square roughness (RMS) of 2 nm or more and 10 nm or less is used. The InN layer is formed on the first surface of the substrate by supplying nitrogen gas into the plasma and supplying it to the substrate and supplying the organometallic gas containing In to the substrate without converting it into plasma. A group III nitride semiconductor layer is grown on the InN layer.

  In the method for manufacturing a group III nitride semiconductor device according to the second aspect, the InN layer is grown with a film thickness of 0.2 nm or more and 1 nm or less.

  In the method for manufacturing a group III nitride semiconductor device according to the third aspect, the InN layer is grown at a substrate temperature of 0 ° C. or higher and 100 ° C. or lower.

  In the Group III nitride semiconductor device manufacturing method according to the fourth aspect, the first Group III nitride semiconductor layer is formed on the InN layer at a substrate temperature of 300 ° C. or higher and 500 ° C. or lower. A second group III nitride semiconductor layer is formed on the first group III nitride semiconductor layer at a substrate temperature of 600 ° C. or higher and 900 ° C. or lower.

  A power device according to a fifth aspect includes a substrate having a first surface, a first group III nitride semiconductor layer on the first surface of the substrate, and a second layer on the first group III nitride semiconductor layer. And a group III nitride semiconductor layer. The root mean square roughness (RMS) of the first surface of the substrate is 2 nm or more and 10 nm or less. The first group III nitride semiconductor layer contains In. The thickness of the first group III nitride semiconductor layer is not less than 5 nm and not more than 20 nm.

DESCRIPTION OF SYMBOLS 100 ... Power device 110 ... Board | substrate 110a ... 1st surface 120 ... 1st buffer layer 130 ... 2nd buffer layer 140 ... GaN layer 150 ... AlGaN layer 160 ... Insulating film S1 ... Source electrode G1 ... Gate electrode D1 ... Drain electrode A1 ... InN layer 1000 ... manufacturing apparatus 1001 ... furnace body 1100 ... shower head electrode 1200 ... susceptor 1210 ... heater 1300 ... first gas supply pipe 1410 ... gas introduction chamber 1420 ... second gas supply pipe 1500 ... metal mesh 1600 ... RF Power supply 1610 ... Matching box

Claims (5)

In the method of manufacturing a group III nitride semiconductor device,
Using a substrate having a first surface having a root mean square roughness (RMS) of 2 nm or more and 10 nm or less,
Nitrogen gas is converted into plasma and supplied to the substrate, and an organometallic gas containing In is supplied to the substrate without being converted into plasma, thereby forming an InN layer on the first surface of the substrate,
A method of manufacturing a group III nitride semiconductor device, comprising growing a group III nitride semiconductor layer on the InN layer. In the manufacturing method of the group III nitride semiconductor device according to claim 1,
A method of manufacturing a group III nitride semiconductor device, wherein the InN layer is grown to a thickness of 0.2 nm to 1 nm. In the manufacturing method of the group III nitride semiconductor device according to claim 1 or 2,
A method for producing a group III nitride semiconductor device, comprising growing the InN layer at a substrate temperature of 0 ° C. or higher and 100 ° C. or lower. In the manufacturing method of the group III nitride semiconductor element of any one of Claim 1- Claim 3,
Forming a first group III nitride semiconductor layer on the InN layer at a substrate temperature of 300 ° C. or more and 500 ° C. or less;
A method of manufacturing a group III nitride semiconductor device, comprising forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer at a substrate temperature of 600 ° C. or higher and 900 ° C. or lower. A substrate having a first surface;
A first group III nitride semiconductor layer on the first surface of the substrate;
A second group III nitride semiconductor layer on the first group III nitride semiconductor layer;
In a power device having
The root mean square roughness (RMS) of the first surface of the substrate is 2 nm or more and 10 nm or less,
The first group III nitride semiconductor layer contains In,
A power device, wherein the first group III nitride semiconductor layer has a thickness of 5 nm to 20 nm.