JP2017130539A - Nitride semiconductor device, and manufacturing method and manufacturing apparatus of nitride semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grow a flat GaN epitaxial layer by using a Si(001) substrate.SOLUTION: A nitride semiconductor device comprises: a Si(001) single crystal substrate 1; an AlN buffer layer 2 laminated on a surface of the single crystal substrate; a GaInN(0.01≤x≤0.3) buffer layer 3 laminated on the AlN buffer layer 2 on a surface on the side opposite to the substrate; and a GaN epitaxial layer 4 laminated on a the GaInN buffer layer 3 on a surface on the side opposite to the substrate. It is preferable that a film thickness of the AlN buffer layer 2 is 13.5-54 times greater than a film thickness of the GaInN buffer layer 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a nitride semiconductor device, a method of manufacturing a nitride semiconductor device, and a manufacturing apparatus. For example, a nitride semiconductor device having a flat surface and a nitride manufactured on a silicon substrate having a lattice constant different from that of a nitride semiconductor. The present invention relates to a method for manufacturing a semiconductor device and a manufacturing apparatus.

  GaN (Gallium Nitride) -based nitride semiconductors have flourished since successful application to semiconductor devices such as high-frequency and high-power HEMTs (High Electron Mobility Transistors), LEDs (Light Emitting Diodes), and LDs (Laser Diodes) It has been studied. These semiconductor devices usually have a laminated structure in which a nitride-based semiconductor is grown on the surface of sapphire, silicon, or silicon carbide substrate. In particular, silicon substrates have many attractive features such as the existence of large-area substrates, high quality, high thermal conductivity, ease of dicing and thinning, completeness of process technology, existence of factory lines around the world, and low price. It has features.

  In recent years, therefore, many research institutions have been conducting research on growing nitride semiconductors on the surface of silicon substrates. However, normally, the crystal structure of a nitride semiconductor that can be grown is a hexagonal hexagonal close-packed structure, and the crystal structure of silicon is a cubic diamond structure. Therefore, a nitride semiconductor having a hexagonal close-packed structure is grown in the c-axis direction using a silicon substrate having a (111) plane orientation.

  Non-Patent Document 1 discloses a technique of using an inclined substrate as a silicon (001) substrate, aligning the directions of domains, and growing flatly in forming an AlGaN / AlN multilayer structure buffer layer.

  Patent Document 1 discloses a technique in which a (001) plane silicon substrate having a porous layer (porous Si portion) is used, and a Si thin film having a (111) plane is bonded to the porous Si portion. Yes.

Japanese Patent No. 5546133 (paragraphs 0010, 0020, 0032)

Epitaxy of GaNon silicone-impact of symmetry and surface reconstruction, New Journal of Physics, 9 (2007), p.389

By the way, a silicon substrate generally used for manufacturing LSI (Large Scale Integration) is a substrate having a (001) plane orientation in which the interface state density of Si—SiO ₂ is small and wet etching is easy. For this reason, if a nitride semiconductor can be grown on a silicon (001) substrate, a hybrid device of LSI and nitride semiconductor on a single substrate becomes possible.

  However, the combination of a nitride semiconductor and a silicon substrate has a problem that a lattice constant and a thermal expansion coefficient are greatly different and cracks are easily generated. In particular, a nitride semiconductor grown on a silicon (001) substrate without using a silicon (111) substrate has a problem of double domain growth in which 30 degree rotation domains are mixed and a problem that flat growth is difficult. It will be held at the same time.

  The problem of the double domain growth can be suppressed by flowing a current mainly in the c-axis direction. However, if the nitride semiconductor does not grow flat, device fabrication itself becomes almost impossible.

FIG. 13 is a surface photograph when a GaN epitaxial layer is grown on the surface of a Si (001) substrate via an AlN buffer layer, and is shown as a comparative example.
Since GaN / AlN deposited on the surface of the silicon (001) substrate has a low crystal growth nucleus density, it has a large uneven surface without covering the entire substrate. As described above, when flat growth is not performed, a device such as photolithography cannot be performed, so that the device cannot be manufactured. Note that when an AlN buffer layer is formed on the surface of a silicon (111) substrate and the GaN layer is subsequently epitaxially grown, it is single domain and flat and mirror-growth.

  Here, there is a technique described in Non-Patent Document 1 as a technique for aligning the domain directions and performing flat growth. However, since the technology disclosed in Non-Patent Document 1 uses a substrate in which silicon (001) is tilted by 4 °, a nitride semiconductor is grown on a substrate different from a silicon substrate used for normal LSI manufacturing. There is a need to. For this reason, it is difficult to hybridize LSI and nitride semiconductor using a single substrate, and LSI and nitride semiconductor must be individually manufactured and mixed in a package.

  If hybrid formation with LSI is abandoned, there are more reported examples than the technology using a substrate in which silicon (001) is inclined by 4 °, single domain growth, and flat growth of a GaN layer is easy. It is sufficient to use a silicon (111) substrate.

  Next, as a method for avoiding the problem, it is conceivable to stack GaN on the surface of a Si thin film having a (111) plane through a buffer layer using the technique described in Patent Document 1. However, an LSI is manufactured separately from the nitride semiconductor device manufactured using the technique described in Patent Document 1, and is mixed in the package. Hybridization in the package is advantageous in terms of cost and technical difficulty.

  Accordingly, an object of the present invention is to provide a nitride semiconductor device, a method for manufacturing a nitride semiconductor, and a manufacturing apparatus capable of flatly growing a GaN epitaxial layer using a Si (001) substrate.

In order to solve the above problems, a nitride semiconductor device according to the present invention includes a Si (001) single crystal substrate and an AlN buffer layer stacked on the surface of the Si (001) single crystal substrate in order to achieve the above object. And a Ga _1-x In _x N (0.01 ≦ x ≦ 0.3) buffer layer laminated on the substrate opposite surface of the AlN layer, and a Ga _1-x In _x N layer laminated on the substrate opposite surface. And a GaN epitaxial layer.

The method for manufacturing a nitride semiconductor device according to the present invention is a method for manufacturing a nitride semiconductor device using a Si (001) single crystal substrate, which is obtained by introducing an Al raw material (for example, TMA) and ammonia gas. An AlN film forming step in which an AlN buffer layer is formed on the surface of the Si (001) single crystal substrate, and the temperature of the Si (001) single crystal substrate is grown with GaInN in a state where the ammonia gas is introduced. A step of lowering the temperature to a temperature (eg, 700 ° C.) higher than a temperature (eg, 600 ° C.) and lower than a temperature of GaN growth (eg, 800 ° C.), a source of In (eg, TMI), a source of Ga ( for example, TMG), and the introduction of ammonia _{gas, Ga 1-x in x N} (0.01 ≦ x ≦ 0.3) buffer layer on the surface of the AlN buffer layer of Si (001) single crystal substrate is the temperature lowers the And further comprising a GaInN film forming process is caused to film.

The nitride semiconductor device manufacturing apparatus of the present invention is a manufacturing apparatus for manufacturing a nitride semiconductor device using a Si (001) single crystal substrate, and is a heating unit for heating the Si (001) single crystal substrate. (22), a reaction tube (24) through which the organometallic material, carrier gas, and ammonia gas flow on the surface of the Si (001) single crystal substrate, the amount of the organometallic material, the flow rate of the ammonia gas, And a control unit (40) for controlling the heating unit,
A substrate heating control unit for controlling the heating unit until the Si (001) single crystal substrate reaches a temperature (for example, 1200 degrees) higher than a growth temperature (for example, 800 degrees) of GaN; A raw material (for example, TMA) and an AlN film formation control unit that allows ammonia gas to flow therethrough, and the Si (001) single crystal substrate is grown at a GaInN growth temperature (for example, 600 degrees) while the ammonia gas is flowing therethrough. A substrate cooling controller that lowers the temperature to a temperature (700 degrees) lower than the growth temperature of GaN (e.g., 800 degrees), and an In source (e.g., TMI), Ga source (e.g., , TMG), and a GaInN film formation control unit that allows ammonia gas to flow therethrough. In addition, the temperature, material, and code | symbol in () are illustration.

  According to the present invention, a GaN epitaxial layer can be grown flat using a Si (001) substrate. Thereby, processes such as photolithography can be performed. Even if a double domain is formed, current can flow in the c-axis direction.

It is sectional drawing which shows the laminated structure of the nitride semiconductor device which is 1st Embodiment of this invention. 1 is a configuration diagram of a manufacturing apparatus for manufacturing a nitride semiconductor device according to a first embodiment of the present invention. It is a block diagram of a control part. 3 is a flowchart illustrating a manufacturing method for manufacturing a nitride semiconductor device. 6 is a flowchart when a nitride semiconductor layer is stacked after forming a GaN epitaxial layer. 3 is a surface photograph of a GaN epitaxial layer of the nitride semiconductor device according to the first embodiment of the present invention. 5 is a surface photograph when the growth time of the GaInN buffer layer in the nitride semiconductor device of the first embodiment of the present invention is changed. 6 is a surface photograph of the nitride semiconductor device according to the first embodiment of the present invention when the film thickness of the GaN epitaxial layer is changed. It is sectional drawing of the nitride semiconductor device which is 2nd Embodiment of this invention. It is a flowchart explaining the preparation method which produces the nitride semiconductor device of 2nd Embodiment. 2 is a surface photograph of the uppermost GaN epitaxial layer of a sample of a nitride semiconductor device according to an embodiment of the present invention. It is explanatory drawing explaining a domain when GaN accumulates on Si (001) board | substrate. It is a surface photograph when a GaN epitaxial layer is grown on the surface of a Si (001) substrate via an AlN buffer layer.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. Each figure is only schematically shown so that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated example. Moreover, in each figure, the same code | symbol is attached | subjected about the common component and the same component, and those overlapping description is abbreviate | omitted.

(First embodiment)
(Description of configuration)
FIG. 1 is a cross-sectional view showing a laminated structure of a nitride semiconductor device according to the first embodiment of the present invention. Here, FIG. 1B is a detailed view of the nitride semiconductor layer 5a of FIG.
The nitride semiconductor device 10 is formed on the Si (001) substrate 1, the AlN buffer layer 2 formed on the surface of the Si (001) substrate 1, and on the surface of the AlN buffer layer 2 opposite to the substrate. Ga and _1-x in x N buffer layer 3, and the _{Ga 1-x} in x N GaN epitaxial layer 4 which is formed on the substrate opposite to the surface of the buffer layer 3 (4a), the substrate opposite the GaN epitaxial layer 4a And a nitride semiconductor layer 5 (5a) laminated on the side surface. Here, _x of the Ga _1-x In _x N buffer layer 3 is 0.01 to 0.3 (preferably 0.02 to 0.1), for example, x = 0.05 (In concentration 5). %). Note that the nitride semiconductor device may not include the nitride semiconductor layer 5a, and an evaluation sample is provided that does not include the nitride semiconductor layer 5a.

The Si (001) substrate 1 is a general-purpose silicon single crystal substrate whose plane orientation indicates the (001) direction, and exhibits a diamond structure. The Si (001) substrate 1 has a lattice constant of 5.43 and a thermal expansion coefficient of 3.59 × 10 ⁻⁶ / K. Note that the Si (111) substrate whose crystal plane orientation indicates the (111) direction has a lattice constant of 3.84.

The AlN buffer layer 2 is a wurtzite aluminum nitride layer having an a-axis lattice constant of about 3.11 and a c-axis lattice constant of about 4.98. The AlN buffer layer 2 has a film thickness of 460 nm. The thermal expansion coefficient of the AlN buffer layer 2 is 4.2 × 10 ⁻⁶ / K.

The Ga _1-x In _x N buffer layer 3 is a layer having a thickness of 26 nm and an In concentration of 5% (x = 0.05). That is, the AlN buffer layer 2 is 17.7 times as thick as the Ga _1-x In _x N buffer layer 3. Note that the Ga _1-x In _x N buffer layer 3 may have a thickness of 8.5 nm to 34 nm. That is, the ratio between the film thickness of the AlN buffer layer 2 and the film thickness of the Ga _1-x In _x N buffer layer 3 may be 13.5 to 54 times, preferably 15 to 20 times.

  GaInN is a mixed crystal material whose lattice constant has an intermediate value between GaN and InN. Note that InN has the same hexagonal wurtzite structure as GaN, the a-axis lattice constant is 3.545, and the c-axis lattice constant is 5.703. The Young's modulus is 11 GPa for indium and 70 GPa for aluminum. That is, GaInN is expected to have lower rigidity than AlGaN.

  The GaN epitaxial layer 4 (4a) is a GaN layer whose crystal plane is aligned with the (0001) plane (c-plane). GaN has a hexagonal Wurtzite ore-type crystal structure, and the lattice constant of the a axis is 3.189 and the lattice constant of the c axis is 5.185. In the evaluation sample for evaluating the nitride semiconductor device 10, the thickness of the GaN epitaxial layer 4a is 0.8 μm.

  The nitride semiconductor layer 5 (5a) includes, for example, an n-type cladding layer 6, a light emitting layer (active layer) 7, and a p-type cladding layer 8, and functions as an LED (Light Emitting Diode). The n-type cladding layer 6 is an n-GaN layer obtained by doping GaN with Si. The p-type cladding layer 8 is a Mg-doped p-GaN layer.

  The light emitting layer 7 is an active layer having a multiple quantum well structure having a plurality of quantum well layers, and can emit brighter and brighter light than the bulk type. The light emitting layer 7 usually has a multi quantum well (MQW) structure including a GaInN well layer and a GaN or GaInN barrier layer.

(Production method)
The nitride semiconductor device 10 is manufactured by a metal organic chemical vapor deposition (MOCVD) method. Hereinafter, a film forming apparatus (manufacturing apparatus) and a manufacturing method for manufacturing the nitride semiconductor device 10 will be described.

(Deposition system)
FIG. 2 is a configuration diagram of a manufacturing apparatus for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, and FIG. 2A is a longitudinal sectional view of a film forming apparatus as the manufacturing apparatus. 2 (b) is a plan view of the film forming apparatus.
In the metal organic chemical vapor deposition, an organic metal source 30 that is a group III, an ammonia (NH ₃ ) gas 36 that is a nitrogen (N) source that is a group V, and a carrier gas 35 that carries the organic metal source 30 are formed into thin films. This is carried out by introducing a nitride thin film on the surface of the Si (001) substrate 1 which is introduced into the reaction chamber of the film forming apparatus and placed on the heated susceptor. Here, the organometallic source 30 is trimethylgallium TMG, trimethylaluminum TMA, or trimethylindium TMI, and the carrier gas 35 is hydrogen H ₂ or nitrogen N ₂ .

  The film forming apparatus 100 is a growth apparatus that includes a chamber 21 that covers the entire apparatus, a heater 22 as a heating unit, a susceptor 23, a quartz reaction tube 24, and a control unit 40. The susceptor 23 is a wafer holder that is heated by the heater 22 or induction-heated. The gas supply side of the reaction tube 24 is separated into two upper and lower flow paths by a partition plate 28. The upper flow path 25 of the reaction tube 24 is a group III line A through which organic metal raw materials TMG, TMA, TMI, dopant raw material, carrier gas 35 and the like flow in the direction of the arrow, and the lower flow path 26 is ammonia. This is a group V line B through which the gas 36, the carrier gas 35 and the like flow in the direction of the arrow.

  The susceptor 23 and the heater 22 are disposed downstream of each flow path, and the heater 22 heats the Si (001) substrate 1 placed on the susceptor 23. A GaN-based nitride semiconductor is manufactured by supplying gas from two flow paths and crystal-growing the heated Si (001) substrate 1. The supplied gas is exhausted from the exhaust flow path 27 of the reaction tube 24 in the direction of the arrow as the exhaust line C.

FIG. 3 is a configuration diagram of the control unit.
The control unit 40 is configured by a CPU (Central Processing Unit), and when the CPU executes a program, the substrate heating control unit (first substrate heating control unit 41, second substrate heating control unit). And the substrate cooling control unit 43 and the film formation control unit (AlN film formation control unit 45, GaInN film formation control unit 46, GaN epi layer film formation control unit 47, and nitride semiconductor layer film formation control unit 48). With these functions, the control unit 40 controls the organometallic raw material, the type of gas, the flow rate, and the heater 22.

  The first substrate heating control unit 41 controls the heater 22 to heat the Si (001) substrate 1 to a temperature (for example, 1200 degrees) higher than the GaN growth temperature (about 800 degrees). The second substrate heating control unit controls the heater 22 to heat the Si (001) substrate 1 until heating to a temperature (for example, 1140 degrees) higher than the GaN growth temperature (800 degrees).

  The substrate cooling control unit 43 stops the heater 22 and cools the Si (001) substrate 1 to a temperature (for example, 700 degrees) lower than the GaN growth temperature (800 degrees). The substrate cooling control unit 43 preferably stops heating the heater 22 and cools the Si (001) substrate 1 by a cooling means (not shown).

The AlN film formation control unit 45 controls trimethylaluminum, which is an Al raw material, to 20 μmol / min, and introduces an organic metal gas: 12 SLM (organometallic push line 1 SLM (1.69 Pam ³ / s) + H ₂ carrier gas 11 SLM (18.59 Pam ³ / s), ammonia gas introduction line: 12 SLM (ammonia 6 SLM (10.14 Pam ³ / s) + H ₂ carrier gas 6 SLM (10.14 Pam ³ / s)).

The GaInN film formation control unit 46 controls trimethylindium TMI, which is a raw material of In, to 2.3 μmol / min, and controls trimethylgallium TMG, which is a raw material of Ga, to 100 μmol / min. (Organic metal push line 1 SLM (1.69 Pam ³ / s) + H ₂ carrier gas 11 SLM (18.59 Pam ³ / s)), ammonia gas introduction line: 12 SLM (ammonia 6 SLM (10.14 Pam ³ / s) + H ₂ carrier The gas is controlled to 6 SLM (10.14 Pam ³ / s).

The GaN epilayer deposition control unit 47 controls trimethylgallium TMG to 100 μmol / min, and introduces an organometallic gas: 12 SLM (organometallic push line 1 SLM (1.69 Pam ³ / s) + H ₂ carrier gas 11 SLM ( 18.59 Pam ³ / s)), ammonia gas introduction line: set to 12 SLM (ammonia 6 SLM + H ₂ carrier gas 6 SLM (10.14 Pam ³ / s)).

In addition to the conditions of the GaN epilayer film formation control unit 47, the nitride semiconductor layer film formation control unit 48 flows SiH ₄ : silane gas as an n-type dopant material and biscyclopentadienylmagnesium: Cp as a p-type dopant material. ₂ Flow Mg.

(Description of manufacturing method)
FIG. 4 is a flowchart for explaining a manufacturing method for manufacturing a nitride semiconductor device.
The manufacturing apparatus or the worker places the Si (001) substrate 1 on the susceptor 23 (FIG. 2) (S10). The Si (001) substrate 1 is assumed to have an oxide film removed beforehand by hydrofluoric acid.

The first substrate heating control unit 41 depressurizes the inside of the growth apparatus to a range from normal pressure to 50 to 200 Torr (6.665 to 26.66 kPa), preferably 100 Torr (13.33 kPa), and then supplies hydrogen to 30 SLM ( The Si (001) substrate 1 is heated at 1000 ° C. for 5 minutes while flowing at about 50.7 Pam ³ / s) to clean the substrate surface (S11). From here, the 1st board | substrate heating control part 41 heats Si (001) board | substrate 1 to 1200 degreeC over 3 minutes (S12).

The AlN film formation control unit 45 grows an AlN film in a reduced-pressure atmosphere 100 Torr (13.33 kPa) (S14). Specifically, the AlN film formation control unit 45 sets trimethylaluminum, which is an Al raw material, to 20 μmol / min, and sets the carrier gas flow rate condition to an organometallic gas introduction line: 12 SLM (organometallic push line 1 SLM (1 .69 Pam ³ / s) + H ₂ carrier gas 11 SLM (18.59 Pam ³ / s)), ammonia gas introduction line: 12 SLM (ammonia 6 SLM (10.14 Pam ³ / s) + H ₂ carrier gas 6 SLM (10. 14Pam ³ / s)).

The substrate cooling control unit 43 lowers the substrate temperature to 700 ° C. while introducing ammonia (S16). Then, the GaInN film formation control unit 46 grows GaInN in a reduced pressure atmosphere 100 Torr (13.33 kPa) (S18). Specifically, the GaInN film forming control unit 46 sets trimethylindium TMI, which is an In raw material, to 2.3 μmol / min, and trimethylgallium (TMG), which is a Ga raw material, to 100 μmol / min. Introduction line: 12 SLM (organometallic push line 1 SLM (1.69 Pam ³ / s) + H ₂ carrier gas 11 SLM (18.59 Pam ³ / s)), ammonia gas introduction line: 12 SLM (ammonia 6 SLM (10.14 Pam ³ / s) ) + H ₂ carrier gas 6 SLM (10.14 Pam ³ / s)). In this way, the Ga _1-x In _x N buffer layer 3 having an In concentration of 5% and a film thickness of 26 nm is obtained.

  Next, the second substrate heating control unit 42 raises the substrate temperature to 1140 ° C. with ammonia gas introduced (S20).

The GaN epilayer film formation control unit 47 forms a GaN epitaxial layer in a state where the substrate temperature is 1140 ° C. (S22). Specifically, the GaN epilayer deposition control unit 47 sets trimethylgallium TMG to 100 μmol / min, and introduces an organic metal gas: 12 SLM (organometallic push line 1 SLM (1.69 Pam ³ / s) + H _2. Carrier gas 11 SLM (18.59 Pam ³ / s)), ammonia gas introduction line: 12 SLM (ammonia 6 SLM (10.14 Pam ³ / s) + H ₂ carrier gas 6 SLM (10.14 Pam ³ / s)). Thereby, a GaN thin film having a film thickness of about 1.6 μm can be obtained in one hour. The evaluation data for evaluating the nitride semiconductor device 10 of this embodiment indicates that the GaN epitaxial layer 4a is grown by 0.8 μm.

FIG. 5 is a flowchart when a nitride semiconductor layer is stacked after forming a GaN epitaxial layer.
The manufacturing apparatus or creator continues to stack a nitride semiconductor layer on the Si (001) substrate 1 (S30) on which the GaN epitaxial layer produced in S22 (FIG. 4) is formed (S32). Specifically, the nitride semiconductor layer deposition control unit 48 flows SiH ₄ : silane gas as an n-type dopant raw material and biscyclopentadienyl magnesium as a p-type dopant raw material in addition to the GaN epitaxial layer deposition conditions: Flow Cp ₂ Mg.

  For the temperature drop after growth, the hydrogen is switched to nitrogen while introducing ammonia, the supply of ammonia is stopped at 400 ° C., and the sample is taken out at 200 ° C. or lower. With the above procedure, nitride semiconductor device 10 (FIG. 1) using a silicon (001) substrate can be manufactured.

(Sample evaluation)
FIG. 6 is a surface photograph (SEM (Scanning Electron Microscope) photograph) of the GaN epitaxial layer of the nitride semiconductor device according to the first embodiment of the present invention. That is, each surface photograph uses a nitride semiconductor device in which the nitride semiconductor layer 5a (FIG. 1) is not stacked as a sample. 6A is a surface photograph of a sample grown with a GaInN layer at 600 ° C., and FIG. 6B is a photograph of the surface of a sample grown with a GaInN layer at 700 ° C. FIG. ) Is a surface photograph of a sample grown with a GaInN layer at 800 ° C. FIG. Each sample was subjected to GaN epitaxial growth for 20 minutes (film thickness: 0.53 μm).

  The GaInN buffer layer growth temperature of 600 ° C. is slightly higher than the growth temperature for growing the low-temperature buffer layer on the sapphire substrate, and the growth temperature of 800 ° C. is difficult to incorporate In in the MQW (Multiple Quantum Well) growth of LEDs and the like. It is the temperature (approximately the growth temperature of GaN).

As can be seen from FIG. 6 (a), the sample in which the Ga _1-x In _x N buffer layer 3 (FIG. 1) is grown at 600 ° C. has a surface state that is almost cloudy. In addition, the sample of the nitride semiconductor device in which the Ga _1-x In _x N buffer layer 3 (FIG. 1) is grown at 700,800 ° C. has a macro surface state as shown in FIGS. The same. However, a sample with a GaInN growth temperature of 800 ° C., when observed microscopically, has a larger surface irregularity than growth at 700 ° C. Therefore, it can be determined that the optimum growth temperature of the Ga _1-x In _x N buffer layer 3 is 700 ° C.

FIG. 7 is a surface photograph when the growth time of the GaInN buffer layer in the nitride semiconductor device according to the first embodiment of the present invention is changed. FIG. 7A is a surface photograph of the GaN epitaxial layer 4 when the Ga _1-x In _x N buffer layer 3 is grown for 5 minutes, and FIG. 7B is a Ga _1-x In _x N buffer. FIGS. 7C and 7D are photographs of the surface of the GaN epitaxial layer 4 when the layer 3 is grown for 10 minutes, and FIGS. 7C and 7D show the case where the Ga _1-x In _x N buffer layer 3 is grown for 15 minutes and FIG. It is the surface photograph of the GaN epitaxial layer 4 when carrying out partial growth. Each sample was subjected to GaN epitaxial growth for 20 minutes (film thickness: 0.53 μm) as in FIG.

As can be seen from FIGS. 7A and 7B, when the growth temperature of the Ga _1-x In _x N buffer layer 3 is the same 700 ° C., the longer the growth time, the larger the crystal grain size of the GaN epitaxial layer 4. Tend to be. However, when the Ga _1-x In _x N buffer layer 3 is grown for 20 minutes (film thickness: 34 nm), the surface unevenness of the GaN epitaxial layer 4 becomes large. Therefore, the optimal growth time of the Ga _1-x In _x N buffer layer 3 is 15 minutes (film thickness: 26 nm).

FIG. 8 is a photograph of the surface of the nitride semiconductor device according to the first embodiment of the present invention when the film thickness of the GaN epitaxial layer is changed. In FIG. 8A, the Ga _1-x In _x N buffer layer 3 is grown at 700 ° C. for 15 minutes (film thickness: 26 nm), and the GaN epitaxial layer 4 is grown for 20 minutes (film thickness: 0.53 μm). 3 is a surface photograph of a sample GaN epitaxial layer 4. FIG. 8B shows that the Ga _1-x In _x N buffer layer 3 is grown at 700 ° C. for 15 minutes (film thickness: 26 nm) and the GaN epitaxial layer 4 is grown for 60 minutes (film thickness: 1.6 μm). 2 is a photograph of the surface of the GaN epitaxial layer 4 at that time. That is, the flatness of the GaN epitaxial layer 4 is better when the GaN epitaxial layer 4 is grown for 60 minutes (film thickness: 1.6 μm) than when the GaN epitaxial layer 4 is grown for 20 minutes (film thickness: 0.53 μm).

  As described above, in the nitride semiconductor device 10 of the present embodiment, the GaN epitaxial layer 4 laminated on the surface of the Si (001) substrate 1 via the buffer layer is grown flat. That is, according to the present embodiment, a nitride semiconductor having a smooth interface and good crystallinity can be produced with an arbitrary film thickness. Further, since the GaN epitaxial layer 4 is grown flat, a process such as photolithography can be performed, and an electronic device / optical device with high reliability and productivity can be provided.

  Note that the nitride semiconductor device 10 of the present embodiment can cause a current to flow at least in the c-axis direction even when the GaN epitaxial layer 4 becomes a double domain, which is problematic for applications of vertical devices such as LEDs. There is no. Further, according to the present embodiment, since Si (001 substrate) can easily form an integrated circuit, a semiconductor device in which the integrated circuit and the nitride semiconductor layer 5a are hybridized can be produced.

In the present embodiment, the growth condition of the Ga _{1 -x} In _x N buffer layer 3 and the optimum film thickness are obtained by SEM observation of the flatness of the GaN epitaxial layer 4a formed on the buffer layer. Yes.

(Second Embodiment)
In the nitride semiconductor device of the first embodiment, the GaN epitaxial layer 4a is formed on the surface of the Si (001) substrate 1 via the buffer layer. The GaN epitaxial layer 4a can be formed.

(Description of configuration)
FIG. 9 is a cross-sectional view of a nitride semiconductor device according to the second embodiment of the present invention.
The nitride semiconductor device 15 is formed on the Si (001) substrate 1, the AlN buffer layer 2 formed on the surface of the Si (001) substrate 1, and the AlN buffer layer 2 on the surface opposite to the substrate. A Ga _1-x In _x N buffer layer 3, a GaN epitaxial layer 4a formed on the surface of the Ga _1-x In _x N buffer layer 3 opposite to the substrate, and a surface of the GaN epitaxial layer 4a opposite to the substrate The formed Ga _1-x In _x N buffer layer 9, the GaN epitaxial layer 4b formed on the opposite surface of the Ga _1-x In _x N buffer layer 9, and the opposite substrate of the GaN epitaxial layer 4b A nitride semiconductor layer 5b stacked on the side surface.

The AlN buffer layer 2 has a film thickness of 460 nm, and the Ga _1-x In _x N buffer layer 3 has an In concentration of 5% and a film thickness of 26 nm. The process up to the point where the GaN epitaxial layer is formed is the same as that of the nitride semiconductor device 10 of the first embodiment. The nitride semiconductor device 15 of this embodiment is different from the nitride semiconductor device 10 of the first embodiment in that GaN / GaInN is repeatedly laminated on the surface of the GaN epitaxial layer 4a opposite to the substrate. Here, the thickness of the GaN epitaxial layer 4a is, for example, 0.53 μm, and the thickness of the GaN epitaxial layer 4b is, for example, 1.06 μm. _The thickness and the In concentration of _{Ga 1-x} In _x N buffer layer 9 is the same as _{Ga 1-x} In _x N buffer layer 3.

(Description of manufacturing method)
FIG. 10 is a flowchart for explaining a manufacturing method for manufacturing the nitride semiconductor device of the second embodiment.
In the nitride semiconductor device 15 (FIG. 9), the combination of Ga _1-x In _x N buffer layer 3 and 6 / GaN epitaxial layers 4a and 4b is stacked twice.

  The manufacturing apparatus or creator prepares the Si (001) substrate 1 on which the GaN epitaxial layer produced in S22 (FIG. 4) is formed (S40). The substrate cooling control unit 43 (FIG. 3) cools the substrate temperature of the Si (001) substrate 1 (S42). The GaInN film formation control unit 46 forms GaInN (S44). The second substrate heating control unit 42 heats the substrate temperature of the Si (001) substrate 1 (S46). The substrate cooling control unit 43 (FIG. 3) determines whether or not the stacking has been performed N times (S50). If the stacking is not performed N times (No in S50), the process is returned to S42, and the substrate temperature is cooled. On the other hand, if the stacking has been performed N times (Yes in S50), the nitride semiconductor layer deposition control unit 48 (FIG. 3) performs the deposition (stacking) of the nitride semiconductor layer 5b (S52). After the growth of the nitride semiconductor layer 5b, the formed Si (001) substrate 1 is taken out from the growth apparatus. Thereby, a sample having the structure of the nitride semiconductor device 15 of the present embodiment is obtained.

(Sample evaluation)
FIG. 11 is a surface photograph (SEM photograph) of the uppermost GaN epitaxial layer of the sample of the nitride semiconductor device according to the embodiment of the present invention. FIG. 11A is a surface photograph of the sample (single buffer) of the nitride semiconductor device 10 of the first embodiment, which is the same as FIG. 8B (the film thickness of the GaN epitaxial layer 4 is 1.6 μm). Is shown for comparison. FIG. 11B is a surface photograph of a sample (double buffer) of the nitride semiconductor device 15 of the second embodiment.

  In the sample of the double buffer in FIG. 11B, the sum of the thickness of the GaN epitaxial layer 4a (0.53 μm) and the thickness of the GaN epitaxial layer 4b (about 1.06 μm) is 1.6 μm. That is, the sample of FIG. 11A and the sample of FIG. 11B have the same thickness, with the thickness of the GaN epitaxial layer 4 being 1.6 μm. The single buffer sample and the double buffer sample are almost the same flatness when observed with the naked eye. However, according to SEM observation, the sample (double buffer) of the second embodiment in which the GaN / GaInN layer is repeated has better surface flatness than the single buffer sample in which the growth time of the GaN epitaxial layer 4a is extended. Thus, according to the configuration of the double buffer of the present embodiment, a sample having a flatter GaN epitaxial layer 4b on a silicon (001) substrate can be produced.

  FIG. 12 is an explanatory diagram for explaining a domain when GaN is deposited on a Si (001) substrate. 12A is a plan view and a side view of GaN having crystal directions different by 30 degrees, and FIG. 12B is a side view showing a state in which GaN is deposited on a Si (001) substrate. 12 (c) is a plan view thereof.

  Since the Si (001) substrate 1 is cubic, while GaN is hexagonal, even if GaN is deposited on the Si (001) substrate, the arrangement direction of GaN is not aligned. For example, GaN (GaN-1, GaN-2) rotated 30 degrees relative to each other is deposited on the Si (001) substrate 1. In other words, the deposition of GaN on the Si (001) substrate results in a double domain in which 30-degree rotation domains are mixed. Here, when the hexagonal plane orientation of GaN is [0001], the direction parallel to one side is [11-20], and the direction perpendicular to this direction is [1-100].

  Further, as shown in FIG. 12C, in the case of a single domain in which 30-degree rotation domains are not mixed, hexagonal sides of GaN are overlapped, and electrical conductivity in the in-plane direction is high. On the other hand, in the case of a double domain in which 30-degree rotation domains are mixed, since the sides of the hexagon do not overlap, there arises a problem that electrical conductivity in the in-plane direction is poor. In this respect, even in the double domain, since the electric conductivity in the direction perpendicular to the hexagonal plane (c-axis direction) is good, if it is an element that allows current to flow in the c-axis direction, such as a vertical device such as an LED, There is no problem with double domain.

(Comparative example)
FIG. 13 is a surface photograph when a GaN epitaxial layer is grown on the surface of a Si (001) substrate via an AlN buffer layer, and is shown as a comparative example. As is clear from the figure, GaN / AlN deposited on the surface of the silicon (001) substrate has a large unevenness without covering the entire substrate because the crystal growth nucleus density is low. Thus, when the GaN layer does not grow flat, a process such as photolithography cannot be performed, and thus the device cannot be manufactured. Note that when an AlN buffer layer is formed on the surface of a silicon (111) substrate and the GaN layer is subsequently epitaxially grown, it is single domain and flat and mirror-growth.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications such as the following are possible.
(1) In each of the above embodiments, the Ga _1-x In _x N buffer layer 3 is formed on the surface of the Si (001) substrate 1 via the AlN buffer layer 2, but instead of the AlN buffer layer 2, An AlGaN / AlN multiple buffer layer can also be inserted. Thereby, it is expected that cracks generated in nitride semiconductor devices 10 and 15 are reduced. In the case of forming a device between cracks, it is not necessary to insert an AlGaN / AlN multiple buffer layer.

(2) The nitride semiconductor layer 5 of each of the embodiments described above is based on GaN, but may be an AlN, AlGaN, or GaInN thin film used for a high-frequency / high-power HEMT, a white LED, or a blue LD.

1 Si (001) single crystal substrate 2 AlN buffer layer 3,9 Ga _1-x In x N buffer layer 4, 4a, 4b GaN epitaxial layer 5, 5a, 5b nitride semiconductor layer 6 n-type cladding layer 7 emitting layer 8 P-type cladding layer 10, 15 Nitride semiconductor device 21 Chamber 22 Heater (heating unit)
23 Susceptor 24 Reaction tube 25 Upper flow path 26 Lower flow path 27 Exhaust flow path 28 Partition plate 30 Organometallic source 35 Carrier gas 36 Ammonia gas 40 Control section 41 First substrate heating control section 42 Second substrate heating control section 43 Substrate cooling control unit 45 AlN film formation control unit 46 GaInN film formation control unit 47 GaN epi layer film formation control unit 48 Nitride semiconductor layer film formation control unit 100 Film formation apparatus (growth apparatus, manufacturing apparatus)
TMA Trimethylaluminum (Group III organometallic source)
TMG Trimethylgallium (Group III organometallic source)
TMI Trimethylindium (Group III organometallic source)

Claims (10)

A Si (001) single crystal substrate;
An AlN buffer layer laminated on the surface of the Si (001) single crystal substrate;
A Ga _1-x In _x N (0.01 ≦ x ≦ 0.3) buffer layer stacked on the surface of the AlN buffer layer opposite to the substrate;
A nitride semiconductor device comprising: a GaN epitaxial layer stacked on a surface of the Ga _1-x In _x N buffer layer opposite to the substrate. The nitride semiconductor device according to claim 1,
A nitride semiconductor device, wherein a nitride semiconductor layer is laminated on a surface of the GaN epitaxial layer opposite to the substrate. The nitride semiconductor device according to claim 1,
The nitride semiconductor device, wherein the thickness of the AlN buffer layer is 13.5 to 54 times the thickness of the Ga _1-x In _x N buffer layer. The nitride semiconductor device according to claim 1,
Another Ga _1-x In _x N (0.01 ≦ x ≦ 0.3) buffer layer;
A stacked structure in which the other GaN epitaxial layer stacked on the surface opposite to the substrate of the other Ga _1-x In _x N buffer layer is repeated one or more times is stacked on the surface opposite to the substrate of the GaN epitaxial layer. A nitride semiconductor device characterized by the above. The nitride semiconductor device according to claim 4,
A nitride semiconductor device, wherein a nitride semiconductor layer is laminated on the surface of the other GaN epitaxial layer in the final stage opposite to the substrate. The nitride semiconductor device according to claim 2 or 5, wherein
An integrated circuit formed on the Si (001) single crystal substrate;
A nitride semiconductor device, wherein the nitride semiconductor layer and the integrated circuit are hybridized. A Si (001) single crystal substrate;
An AlGaN / AlN multiple buffer layer stacked on the surface of the Si (001) single crystal substrate;
A Ga _1-x In _x N (0.01 ≦ x ≦ 0.3) buffer layer stacked on the opposite surface of the AlGaN / AlN multiple buffer layer;
A nitride semiconductor device comprising: a GaN epitaxial layer stacked on a surface of the Ga _1-x In _x N buffer layer opposite to the substrate. A method of manufacturing a nitride semiconductor device using a Si (001) single crystal substrate,
An AlN film forming step in which an AlN buffer layer is formed on the surface of the Si (001) single crystal substrate by introducing an Al raw material and ammonia gas;
A step of lowering the temperature of the Si (001) single crystal substrate to a temperature higher than the growth temperature of GaInN and lower than the growth temperature of GaN in a state where the ammonia gas is introduced;
Ga _1-x In _x N (0.01 ≦ x ≦ 0.3) is formed on the surface of the AlN buffer layer of the Si (001) single-crystal substrate whose temperature has been lowered by introducing an In raw material, a Ga raw material, and ammonia gas. A GaInN film forming step in which a buffer layer is formed;
A method for manufacturing a nitride semiconductor device, further comprising: A method for producing a nitride semiconductor device according to claim 8,
A first heating step in which the Si (001) single crystal substrate is heated to a temperature higher than the growth temperature of GaN before the AlN film forming step;
A second heating step in which the Si (001) single crystal substrate is heated to a temperature higher than the growth temperature of the GaN in a state where ammonia gas is introduced in the GaInN film forming step;
After the second heating step, a GaN epitaxial layer is formed on the surface of the Ga _1-x In _x N buffer layer of the Si (001) single crystal substrate heated by introducing Ga raw material and ammonia gas. And a GaN film forming step to be performed. A method for manufacturing a nitride semiconductor device, comprising: A manufacturing apparatus for manufacturing a nitride semiconductor device using a Si (001) single crystal substrate,
A heating unit for heating the Si (001) single crystal substrate;
A reaction tube through which an organometallic material, a carrier gas, and an ammonia gas flow on the surface of the Si (001) single crystal substrate;
A control unit (40) for controlling the amount of the organometallic material, the flow rate of the ammonia gas, and the heating unit;
The controller is
A substrate heating control unit that controls the heating unit until the Si (001) single crystal substrate reaches a temperature higher than a growth temperature of GaN;
An AlN film formation control unit for flowing Al raw material and ammonia gas through the reaction tube;
A substrate cooling controller that lowers the Si (001) single crystal substrate to a temperature higher than the GaInN growth temperature and lower than the GaN growth temperature in a state where the ammonia gas is flowing;
A GaInN film formation control unit for allowing the In raw material, the Ga raw material, and ammonia gas to flow through the reaction tube;
An apparatus for manufacturing a nitride semiconductor device, comprising: