Method for manufacturing GaN multilayer substrate

Abstract

The present invention is a method for manufacturing a GaN stacked substrate, which comprises: a step of performing a high-temperature nitridation treatment at 800 to 1000°C on a C-plane sapphire substrate (11) with a deviation angle of 0.5 to 5 degrees to perform surface treatment on the C-plane sapphire substrate; a step of epitaxially growing GaN on the surface of the surface-treated C-plane sapphire substrate (11) to produce a GaN film carrier having an N-polar surface on the surface; and a step of ion implanting the GaN film (13) to form an ion implantation region (13). 离子 ) step; the step of bonding and joining the GaN film side surface of the GaN film support body after ion implantation to the supporting substrate (12); and the ion implantation region (13) in the GaN film (13) 离子 ) is peeled off to transfer the GaN film (13a) onto a supporting substrate (12) to obtain a GaN stacked substrate (10) having a GaN film (13a) whose surface includes a Ga polar surface on the supporting substrate (12). A GaN stacked substrate with good crystallinity and a Ga surface as the surface is obtained through a single transfer process.

Description

Technical Field

[0001] The present invention relates to a method for producing a GaN multilayer substrate having a Ga polar plane (Ga plane) on its surface. Background Art

[0002] Crystalline GaN has a wider band gap than Si and GaAs and is expected to be used in high-speed and high-power devices. However, bulk GaN substrates with good crystallinity are small in diameter and very expensive, which is a major factor hindering their popularization.

[0003] By using the hydride vapor phase epitaxy method (HVPE method) and the metal organic vapor phase epitaxy method (MOCVD method) to heteroepitaxially grow GaN on AlN substrates and Al2O3 (sapphire) substrates, larger-diameter GaN films have been obtained, but GaN films with very high properties have not yet been obtained.

[0004] In addition, a stacked substrate in which a GaN thin film is formed on a Si substrate, which is generally a widely used semiconductor material, can obtain the excellent basic properties of GaN while being able to apply advanced processing technology of Si semiconductor devices, and is therefore highly anticipated as a substrate for high-performance devices.

[0005] Among them, as a method for forming a GaN thin film on a Si substrate, a method for forming a GaN thin film on a Si substrate has been developed. <111> The method of directly growing GaN films on the surface by heteroepitaxial growth has been put into practical use on large-diameter substrates with a diameter of 200 mm.

[0006] However, for this method, a thick buffer layer between the Si substrate and the GaN film is indispensable for obtaining GaN with good crystallinity. The reason is that due to the large difference in thermal expansion coefficients between the GaN film and the Si substrate, the stacked substrate warps. The thicker the GaN film, the greater the warping, which causes various defects. That is, if the warping of the stacked substrate increases, there is a problem of the stacked substrate eventually breaking. Even if it does not break, various problems will occur in the semiconductor device process. This is a major problem in the micro-fabrication exposure process. Therefore, in order to alleviate the warping, a thick buffer layer with a linear expansion coefficient intermediate between these two materials must be inserted between the Si substrate and the GaN film. In addition, in this method, it is difficult to thicken the GaN layer with good characteristics on the stacked substrate.

[0007] As a method for solving such a problem, a method for manufacturing a GaN multilayer substrate using transfer using the following steps is conceivable.

[0008] That is, first, a first substrate is prepared, and a GaN film with a certain thickness or more is epitaxially grown on the surface. Next, ion implantation is performed on the substrate to form a brittle layer (ion implantation region) from the surface to a certain depth. After the substrate is bonded to a second substrate, the brittle layer is peeled off, and the GaN thin film is transferred to the second substrate to obtain a GaN stacked substrate.

[0009] Among them, for the general epitaxial growth of GaN (that is, the GaN epitaxial growth film formed on the above-mentioned first substrate), the growth surface (surface) side becomes a Ga polar surface (hereinafter referred to as the Ga surface). Therefore, the ion implantation surface side becomes the Ga surface, and the surface after peeling off and transferring on the second substrate becomes the N polar surface (N surface). Among them, as an electronic component use, the device manufacturing surface needs to be a Ga surface, so the GaN thin film transferred to the second substrate must be bonded to the third substrate again and transferred so that the surface becomes the Ga surface. Therefore, various attempts to peel off and transfer the surface on the second substrate to become the Ga surface (that is, to make the epitaxial growth surface on the first substrate become the N surface) have been widely studied so far. Generally, for epitaxial growth on the N surface, the crystallinity of the GaN film is poor, and it is difficult to use it for device purposes.

[0010] Due to the characteristics of GaN epitaxial growth, the growth surface (surface) of the final GaN stacked substrate needs to be a Ga surface, so the GaN thin film must be transferred twice. As a result, the process becomes complicated, which is the main factor of low yield and high cost.

[0011] In addition, as a prior art related to the present invention, Japanese Unexamined Patent Application Publication No. 2016-511934 (Patent Document 1) can be cited.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application No. 2016-511934 Summary of the invention

[0015] Problems to be solved by the invention

[0016] The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide a method for manufacturing a GaN multilayer substrate in which a GaN multilayer substrate having a Ga-face as a surface and good crystallinity is obtained by a single transfer process.

[0017] Means for solving problems

[0018] In order to achieve the above-mentioned object, the present invention provides the following method for manufacturing a GaN multilayer substrate.

[0019] 1. A method for manufacturing a GaN stacked substrate, comprising:

[0020] A step of performing a high-temperature nitridation treatment at 800 to 1000° C. on a C-plane sapphire substrate having an off angle (off angle) of 0.5 to 5 degrees and / or a deposition treatment of crystalline AlN on the C-plane sapphire substrate to perform surface treatment on the C-plane sapphire substrate;

[0021] A step of epitaxially growing GaN on the surface of the surface-treated C-plane sapphire substrate to produce a GaN film support having an N-polar surface on the surface;

[0022] A step of performing ion implantation on the GaN film to form an ion implantation region;

[0023] The step of attaching and bonding the GaN film side surface of the ion-implanted GaN film support to a supporting substrate; and

[0024] The ion implanted region in the GaN film is peeled off to transfer the GaN thin film onto a supporting substrate, thereby obtaining a GaN multilayer substrate having a GaN thin film having a Ga polar surface on the supporting substrate.

[0025] 2. The method for manufacturing a GaN multilayer substrate according to 1, wherein the GaN epitaxial growth is performed at a temperature higher than that of the high-temperature nitridation treatment.

[0026] 3. The method for manufacturing a GaN multilayer substrate according to 1 or 2, wherein the epitaxial growth of GaN is performed by MOCVD.

[0027] 4. The method for manufacturing a GaN multilayer substrate according to any one of 1 to 3, wherein after the C-plane sapphire substrate is surface treated, a GaN buffer layer is formed at 700° C. or less, and then the GaN epitaxial growth is performed on the GaN buffer layer.

[0028] 5. The method for manufacturing a GaN multilayer substrate according to 4, wherein the thickness of the GaN buffer layer is 15 to 30 nm.

[0029] 6. The method for producing a GaN multilayer substrate according to any one of 1 to 5, wherein after a GaN film is formed by the epitaxial growth, a silicon oxide film is further formed on the GaN film to produce the GaN film support.

[0030] 7. The method for producing a GaN multilayer substrate according to any one of 1 to 6, wherein the ion implantation surface of the GaN film support is further smoothed to an arithmetic mean roughness Ra of 0.3 nm or less before the ion implantation.

[0031] 8. The method for manufacturing a GaN multilayer substrate according to any one of 1 to 7, wherein the ion implantation is performed using hydrogen ions (H + ) and / or hydrogen molecular ions (H2 + ), implantation energy 100~160keV, dose 1.0×10 17 ~3.0×10 17 Atom / cm 2 processing.

[0032] 9. The method for producing a GaN multilayer substrate according to any one of 1 to 8, wherein the support substrate comprises Si, Al2O3, SiC, AlN or SiO2.

[0033] 10. The method for manufacturing a GaN stacked substrate according to 9, wherein the support substrate is a product in which a silicon oxide film is formed on the bonding surface with the GaN film support body, but does not include the case where the support substrate is composed of SiO2.

[0034] Effects of the Invention

[0035] According to the present invention, by performing a prescribed surface treatment on a C-plane sapphire substrate having a prescribed deviation angle, GaN is epitaxially grown on the substrate, thereby forming a GaN film with good crystallinity whose surface is composed of an N polar surface, so that a GaN stacked substrate whose surface is composed of a Ga polar surface can be obtained by a single transfer. Compared with the past, the number of transfers is reduced, thereby making it possible to reduce process costs. Furthermore, it is possible to reduce the GaN film that disappears due to transfer, making it possible to reduce material costs. In addition, the in-plane fluctuation of the film thickness and the surface roughness increase according to the number of transfers, and as a result, the number of transfers is reduced compared with the past, so it is possible to suppress them.

[0036] In addition, according to the present invention, as a donor substrate for GaN thin film transfer, a substrate that is easy to enlarge in diameter by epitaxial film formation is used, so that a low-cost and large-diameter GaN stacked substrate is obtained compared with the case of using an expensive, small-diameter bulk GaN substrate as a donor substrate. The GaN stacked substrate whose surface is composed of Ga polar planes obtained in the present invention is further epitaxially formed into GaN by using it as a GaN template substrate, thereby obtaining a GaN substrate with high withstand voltage and high characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The figures are diagrams showing the manufacturing process in one embodiment of the manufacturing method of the GaN stacked substrate involved in the present invention, (a) is the preparation of the C-plane sapphire substrate and the supporting substrate, (b) is the surface treatment of the C-plane sapphire substrate, (c) is the GaN epitaxial growth, (d) is the ion implantation treatment, (e) is the bonding, and (f) is the peeling transfer of the GaN thin film. DETAILED DESCRIPTION

[0038] The following is a description of a method for producing a GaN multilayer substrate according to the present invention. It should be noted that the numerical range "A to B" includes both numerical values, and means A or more and B or less.

[0039] The manufacturing method of the GaN stacked substrate involved in the present invention is characterized in that it has: a process of surface treating the C-face sapphire substrate by performing a high-temperature nitridation treatment at 800 to 1000°C on a C-face sapphire substrate with a deviation angle of 0.5 to 5 degrees and / or a deposition treatment of crystalline AlN on the C-face sapphire substrate; a process of epitaxially growing GaN on the surface of the surface-treated C-face sapphire substrate to produce a GaN film carrier whose surface is composed of an N-polar surface; a process of ion implanting the GaN film to form an ion implantation region; a process of laminating and bonding the GaN film side surface of the ion-implanted GaN film carrier to a supporting substrate; and a process of peeling off the ion implantation region in the GaN film to transfer the GaN thin film to the supporting substrate to obtain a GaN stacked substrate having a GaN thin film whose surface is composed of a Ga-polar surface on the supporting substrate.

[0040] The following is based on Figure 1 A method for producing a GaN multilayer substrate according to the present invention will be described in detail.

[0041] The manufacturing method of the GaN stacked substrate according to the present invention is as follows Figure 1 As shown in the figure, the processes are carried out in the order of (a) preparation process of C-plane sapphire substrate and supporting substrate (process 1), (b) surface treatment process of C-plane sapphire substrate (process 2), (c) GaN epitaxial growth process (process 3), (d) ion implantation process (process 4), (e) bonding process (process 5), and (f) stripping and transfer process of GaN thin film (process 6).

[0042] (Step 1: Preparation of C-plane sapphire substrate and support substrate)

[0043] First, prepare a C-plane sapphire substrate 11 and a support substrate 12 ( Figure 1 (a)).

[0044] Among them, the C-plane sapphire substrate 11 is a substrate made of sapphire (α-Al2O3) with the C-plane ((0001) plane) as the substrate surface. In addition, the c-axis deviation angle (hereinafter referred to as deviation angle) of the C-plane sapphire substrate 11 is 0.5 to 5 degrees, preferably 2 to 3 degrees. By making the deviation angle within this range, the surface of the GaN film 13 formed on the C-plane sapphire substrate 11 becomes an N-polar surface (hereinafter referred to as N-plane), and at the same time becomes an epitaxial growth film with good smoothness and good crystallinity. When a part of it is peeled off by ion implantation and transferred to the support substrate 12, the GaN film 13a as its transfer film has excellent smoothness. It should be noted that the deviation angle is the angle when the substrate surface (the surface to be crystallized) is slightly tilted in a specific direction from the densest surface, and the c-axis deviation angle refers to the size of the inclination of the c-axis (normal axis of the C-plane) of the C-plane sapphire substrate 11 in the a-axis direction.

[0045] The C-plane sapphire substrate 11 preferably has an arithmetic mean roughness Ra (JIS B0601:2013, hereinafter the same) of 0.5 nm or less. This makes the surface of the epitaxially formed GaN film 13 smoother, allowing for stronger bonding with the support substrate 12.

[0046] The support substrate 12 is a substrate that ultimately supports the GaN thin film 13a, and is preferably made of Si, Al2O3, SiC, AlN or SiO2. Its constituent material can be appropriately selected according to the application of the semiconductor device manufactured using the obtained GaN multilayer substrate.

[0047] The arithmetic mean roughness Ra of the surface of the support substrate 12 is preferably 0.5 nm or less. This allows for stronger bonding when bonding the GaN layer support with the C-plane sapphire substrate 11 and the GaN layer 13 .

[0048] In addition, a bonding film composed of silicon oxide (SiOx thin film, where 0 < x ≦ 2) may be provided on the outermost layer of the support substrate 12 (however, excluding the case where the support substrate 12 is composed of SiO2). Furthermore, when the surface roughness of the support substrate 12 itself is not small enough (for example, when the arithmetic mean roughness Ra of the surface of the support substrate 12 exceeds 0.5 nm), the bonding film may be processed by chemical mechanical polishing (CMP) or the like to smooth the surface. Thus, the bonding strength with the GaN layer support having the C-plane sapphire substrate 11 and the GaN layer 13 can be further increased.

[0049] Furthermore, the thickness of the bonding film is preferably about 300 to 1000 nm.

[0050] (Process 2: Surface treatment of C-surface sapphire substrate)

[0051] Next, the surface treatment of the C-plane sapphire substrate 11 is performed ( Figure 1 (b)).

[0052] That is, a high-temperature nitridation process at 800 to 1000° C. of the C-plane sapphire substrate 11 and / or a deposition process of crystalline AlN on the C-plane sapphire substrate 11 is performed.

[0053] Among them, as for the high-temperature nitridation treatment of the C-plane sapphire substrate 11, the C-plane sapphire substrate 11 is heated in a nitrogen-containing atmosphere to a temperature slightly lower than the film forming temperature of the subsequent GaN epitaxial growth, specifically 800 to 1000°C, and an AlN film is formed on the surface of the C-plane sapphire substrate 11 as a surface treatment layer 11a. This treatment is preferably carried out in situ in the same processing chamber of the MOCVD device that epitaxially grows the GaN film, and is carried out at a temperature (800 to 1000°C) slightly lower than the film forming temperature (1050 to 1100°C) of the GaN epitaxial growth. At this time, if the treatment temperature is less than 800°C, the N-pole growth of the GaN film does not occur, and further, if it exceeds 1000°C, the smoothness deteriorates in the subsequent epitaxial growth of GaN. In addition, pure nitrogen is used as a process gas, and ammonia can also be used. By using ammonia, more active N atoms are generated, and the surface morphology (crystal structure) of the GaN film can be improved. In addition, the high temperature nitridation treatment time can be set to about 30 seconds to 30 minutes. By extending the treatment time, the surface morphology (crystal structure) of the GaN film can be improved.

[0054] The deposition process of crystalline AlN on the C-plane sapphire substrate 11 is to form a crystalline AlN film as a surface treatment layer 11a on the C-plane sapphire substrate 11 by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method). The deposition process can be performed under formation conditions that can cover the surface of the C-plane sapphire substrate 11 with the crystalline AlN film (surface treatment layer 11a).

[0055] Furthermore, after the crystalline AlN film is deposited as the surface treatment layer 11 a on the C-plane sapphire substrate 11 as described above, it is preferable to perform a heat treatment to stabilize the crystalline AlN film before epitaxial growth of GaN.

[0056] (Step 3: GaN epitaxial growth step)

[0057] Next, GaN is epitaxially grown on the surface of the C-plane sapphire substrate 11 subjected to the surface treatment described above to form a GaN film 13 having an N-polar surface on the surface, thereby manufacturing a GaN film support.

[0058] As epitaxial growth methods for GaN films, molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), and metal organic vapor phase epitaxy (MOCVD) are known. When growing a low-defect GaN thin film directly on a sapphire substrate 11, the MOCVD method is most suitable and preferred.

[0059] At this time, the epitaxial growth of the GaN film 13 by MOCVD is preferably performed at a temperature higher than that of the high-temperature nitridation treatment in the above step 2 (i.e., more than 1000° C.), preferably more than 1000° C. and less than 1100° C. to achieve a balance between the film quality and the film formation rate of the GaN film 13. In addition, trimethylgallium (TMG) and ammonia (NH3) are used as process gases, and hydrogen can be used as a carrier gas.

[0060] The thickness of the GaN film 13 corresponds to the thickness of the GaN thin film 13 a to be finally obtained, and is, for example, 0.5 to 10 μm.

[0061] Furthermore, after surface treatment of the C-plane sapphire substrate 11 in step 2, a GaN buffer layer is preferably formed at a low temperature, for example, below 700° C., and then GaN epitaxial growth is performed on the GaN buffer layer using the above-mentioned MOCVD method to form a GaN film 13.

[0062] At this time, when forming the GaN buffer layer, if the film forming temperature exceeds 700°C, the GaN film 13 on the buffer layer does not grow well at the N pole, and if it is less than 400°C, the film formation itself does not proceed, so it is preferably formed at 400-700°C, more preferably 400-600°C. In addition, if the thickness of the GaN buffer layer is too thin, the buffer effect may not be obtained, and if it is too thick, the film quality may be reduced, so it is preferably 15-30nm, more preferably 20-25nm.

[0063] Through the above series of steps for forming the GaN film 13, a GaN film 13 (so far, the GaN film 13 having an N-face surface and excellent crystallinity) is formed on the C-face sapphire substrate 11. Figure 1 (c)).

[0064] Among them, the crystal surface of compound semiconductors such as GaN has polarity. For example, a single crystal GaN film composed of the constituent elements Ga and N must have: a polar surface composed of Ga atoms (as the terminal) with the unbonded ends of the Ga atoms exposed (Ga polar surface (also called Ga surface)) and a polar surface composed of N atoms (as the terminal) with the unbonded ends of the N atoms exposed (N polar surface (also called N surface)).

[0065] In addition, the crystal structure of GaN is a hexagonal system, and its polar surface appears on the densest surface of the lattice. It should be noted that the densest surface of the hexagonal compound semiconductor crystal is the {0001} surface, and the (0001) surface and the (000-1) surface are not equivalent. The former is the surface where the cation atoms are exposed, and the latter is the surface where the anion atoms are exposed. In gallium nitride (GaN), the (0001) surface is the Ga surface, and the (000-1) surface becomes the N surface.

[0066] Furthermore, after the GaN film 13 is formed by the epitaxial growth, a silicon oxide (SiOx, where 0 < x ≤ 2) film may be formed on the GaN film 13 as a bonding layer for bonding with the support substrate 12 to form the GaN film support. The thickness of the silicon oxide film is preferably 200 to 1000 nm.

[0067] (Step 4: Ion Implantation Step into GaN Film 13)

[0068] Next, ion implantation is performed from the surface of the GaN film 13 of the GaN film support to form a layered ion implantation region 13 in the GaN film 13. 离子 ( Figure 1 (d)).

[0069] At this time, it is preferable to use hydrogen ions (H + ) and / or hydrogen molecular ions (H2 + ).

[0070] In addition, the implantation energy determines the ion implantation depth (i.e., the thickness of the peeled film (GaN thin film 13a)), and is preferably 110 to 160 keV. If the implantation energy is 100 keV or more, the thickness of the GaN thin film 13a can be made 500 nm or more. On the other hand, if it exceeds 160 keV, the implantation damage becomes larger, which may cause the deterioration of the crystallinity of the peeled thin film.

[0071] In addition, the dose is preferably 1.0×10 17 ~3.0×10 17 Atom / cm 2 Thus, the ion implantation region 13 serving as a peeling layer (embrittled layer) can be formed in the GaN film 13. 离子 , and the temperature rise of the GaN film support can be suppressed. In addition, the ion implantation temperature is room temperature. If it becomes high temperature, the GaN film support may be broken, so the GaN film support can be cooled.

[0072] Among them, the above-mentioned ion implantation treatment can be carried out on the GaN film carrier in the state where the GaN film 13 is formed in step 3. If the surface of the GaN film 13 in the state where the GaN film 13 is formed is rough, the ion implantation depth becomes uneven corresponding to the surface unevenness, and the unevenness of the peeling surface (surface) of the GaN film 13a after peeling becomes larger.

[0073] Therefore, the ion implantation surface of the GaN film support may be smoothed before the above-mentioned ion implantation so that the arithmetic mean roughness is preferably 0.3 nm or less, more preferably 0.2 nm or less.

[0074] For example, the surface of the GaN film 13 formed in step 3 may be smoothed by polishing and / or etching using CMP or the like so that the arithmetic mean roughness Ra is preferably 0.3 nm or less, more preferably 0.2 nm or less.

[0075] Alternatively, when a silicon oxide film is formed as a bonding layer on the GaN film 13 (i.e., the GaN film 13 in a film-forming state or smoothed by grinding and / or etching), the surface of the silicon oxide film may be smoothed by grinding and / or etching using CMP or the like, so that the arithmetic mean roughness Ra is preferably 0.3 nm or less, more preferably 0.2 nm or less. This is particularly effective when the GaN film 13 is thin and flattening by grinding or the like is difficult.

[0076] By smoothing the surface of the planned GaN film carrier for ion implantation (i.e., the surface of the GaN film 13 or the silicon oxide film serving as the above-mentioned bonding layer) as described above, the ion implantation depth in the subsequent ion implantation process can be made constant, and then, when it is bonded to the supporting substrate 12 and then peeled off, a peeling transfer layer (GaN film 13a) with a smooth surface (small surface roughness) can be obtained.

[0077] (Step 5: Step of bonding the GaN film support and the supporting substrate 12)

[0078] Next, the side surface of the GaN film 13 of the ion-implanted GaN film support body is bonded to the support substrate 12 ( Figure 1 (e)).

[0079] In the case of bonding the GaN film support body and the support substrate 12 without forming a bonding layer (silicon oxide film), the surface (N-face) of the GaN film 13 of the GaN film support body is bonded to the surface of the support substrate 12. That is, a stacked structure of C-face sapphire substrate 11 / surface treatment layer 11a / (GaN buffer layer) / GaN film 13 (N-face) / support substrate 12 is formed.

[0080] In addition, when a GaN film support body having a bonding layer (silicon oxide film) formed on at least one of its surfaces is bonded to a support substrate 12, the surface (N-face) of the GaN film 13 of the GaN film support body is bonded to the surface of the support substrate 12 via the bonding layer (silicon oxide film) therebetween. That is, a stacked structure of C-face sapphire substrate 11 / surface treatment layer 11a / (GaN buffer layer) / GaN film 13 (N-face) / bonding layer (silicon oxide film) / support substrate 12 is formed.

[0081] Before the bonding, it is preferable to perform plasma treatment as a surface activation treatment on both or one of the ion implantation surface of the GaN film support and the bonding surface of the support substrate 12 .

[0082] For example, a GaN film support and / or supporting substrate 12 for surface activation treatment can be installed in a general parallel plate plasma chamber, a high frequency of about 13.56 MHz and 100 W is applied, and Ar, N2, O2, etc. are introduced as process gases for treatment. The treatment time is set to 5 to 30 seconds. In this way, the surface of the target substrate is activated, and the bonding strength after bonding is increased.

[0083] Furthermore, after lamination, annealing at about 200 to 300° C. is performed to form a stronger bond.

[0084] (Step 6: Stripping and Transferring of GaN Thin Film)

[0085] Next, the ion implantation region 13 in the GaN film 13 is 离子 The GaN thin film 13a is transferred onto the supporting substrate 12 ( Figure 1 (f)).

[0086] The peeling process may be any process generally performed by ion implantation peeling, and for example, in addition to mechanical peeling such as blade insertion, optical peeling such as laser irradiation, and physical impact peeling such as water jet and ultrasonic waves may be applied.

[0087] Thus, a GaN multilayer substrate 10 is obtained, which has a GaN thin film 13 a having a surface composed of a Ga polar plane, good crystallinity, and a smooth surface, on the support substrate 12 .

[0088] Furthermore, the surface of the transferred GaN thin film 13a after peeling is sufficiently smooth, but it can be smoothed by grinding or the like depending on the required characteristics of the device using the GaN stacked substrate 10. In addition, by further epitaxially growing a GaN film on the GaN stacked substrate 10, a low-defect, thick-film GaN substrate can also be manufactured.

[0089] Furthermore, as for the method of confirming the polar surface of the GaN thin film 13a surface of the GaN stacked substrate 10, for example, it can be judged by observing the difference in etching rate generated by the KOH aqueous solution. That is, the etching rate of the N surface is greater than the etching rate of the Ga surface. For example, when immersed in a 40°C, 2 mol / L KOH aqueous solution for 45 minutes, it can be confirmed that the Ga surface is not etched but the N surface is etched.

[0090] Example

[0091] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0092] [Example 1]

[0093] A GaN multilayer substrate was produced under the following conditions.

[0094] (Example 1-1)

[0095] A C-plane sapphire substrate with a diameter of 100 mm, a thickness of 525 μm, an arithmetic mean roughness Ra of 0.3 nm, and a C-axis deviation angle of 3 degrees was prepared. After the substrate was cleaned by RCA cleaning, a high-temperature nitridation treatment (process gas: pure nitrogen) at a substrate temperature of 900°C for 30 minutes was performed using an MOCVD device. Then, a GaN buffer layer with a thickness of 20 nm was formed at a substrate temperature of 400°C, and then epitaxial growth was performed at a substrate temperature of 1050°C using process gases: TMG and NH3 to form a 2 μm GaN film. The arithmetic mean roughness Ra of the GaN film was 8 nm.

[0096] Next, a 1 μm thick silicon oxide film was formed on the GaN film by plasma CVD, and then the silicon oxide film was polished to 200 nm by CMP. The arithmetic mean roughness Ra of the obtained GaN film support was 0.3 nm.

[0097] Secondly, hydrogen molecular ions H2 + The implantation energy was 160 keV and the dose was 3.0×10 +17 Atom / cm 2 Perform ion implantation.

[0098] Next, a Si substrate with a diameter of 100 mm and a thickness of 525 μm was prepared, and a thermal oxide film with a thickness of 300 nm was formed on the Si substrate. The arithmetic mean roughness of the Si substrate after the thermal oxide film was formed was Ra=0.5 nm.

[0099] Ar plasma treatment was applied to the thermal oxide film and silicon oxide film (ion implantation surface) of the Si substrate and the GaN film support. Then, the Ar plasma treated surfaces were bonded together and annealed at 200°C for 12 hours in a nitrogen atmosphere. After annealing, a metal blade was inserted into the ion implantation area of ​​the GaN film for peeling, and the GaN film was transferred to the Si substrate to obtain a GaN stacked substrate.

[0100] The arithmetic mean roughness Ra of the GaN thin film surface of the obtained GaN stacked substrate was 8nm. In addition, the crystallinity of the GaN thin film of the obtained GaN stacked substrate was evaluated by the X-ray rocking curve method. In detail, the tilt angle distribution (チルト distribution) (full width at half maximum) in the rocking curve (ω scan) of the GaN (0002) surface reflection of the above-mentioned GaN thin film was obtained by X-ray diffraction, and the result was 300arcsec, showing good crystallinity.

[0101] In addition, as a confirmation of the polar surface of the GaN film, the sample was immersed in a 40°C, 2 mol / L KOH aqueous solution for 45 minutes and the surface was observed. The results showed that the GaN film surface was not etched and became a Ga face.

[0102] (Example 1-2)

[0103] In Example 1-1, after epitaxially growing a GaN film with a thickness of 2 μm, the surface of the GaN film was CMP polished to a surface arithmetic mean roughness Ra of 0.2 nm and directly transferred. A GaN multilayer substrate was obtained in the same manner as in Example 1-1 except for the above.

[0104] The arithmetic mean roughness Ra of the GaN thin film surface of the obtained GaN stacked substrate was 0.3 nm. In addition, the crystallinity of the GaN thin film of the obtained GaN stacked substrate was evaluated by the X-ray rocking curve method in the same manner as in Example 1-1, and the result was FWHM 250 arcsec, showing the same crystallinity as in Example 1.

[0105] In addition, the polarity of the surface of the GaN thin film was confirmed in the same manner as in Example 1-1, and it was found to be the Ga face.

[0106] (Comparative Example 1-1)

[0107] In Example 1-1, a GaN stacked substrate was obtained in the same manner as in Example 1-1 except that the c-axis deviation angle of the C-plane sapphire substrate was set to 0.05 degrees (arithmetic mean roughness Ra 0.3 nm). The arithmetic mean roughness Ra of the GaN film after the GaN film was formed was 60 nm, and the arithmetic mean roughness Ra of the GaN film support after the silicon oxide film was CMP polished was 0.2 nm.

[0108] The arithmetic mean roughness Ra of the GaN thin film surface of the obtained GaN stacked substrate was 60 nm. In addition, the crystallinity of the GaN thin film of the obtained GaN stacked substrate was evaluated by the X-ray rocking curve method in the same manner as in Example 1-1, and the result was FWHM 600 arcsec, indicating poor crystallinity.

[0109] In addition, the polarity of the surface of the GaN thin film was confirmed in the same manner as in Example 1-1, and it was found to be the Ga face.

[0110] (Comparative Example 1-2)

[0111] In Example 1-1, a GaN stacked substrate was obtained in the same manner as in Example 1-1 except that the c-axis deviation angle of the C-plane sapphire substrate was 6 degrees (arithmetic mean roughness Ra 0.3 nm). The arithmetic mean roughness Ra of the GaN film after the GaN film was formed was 80 nm, and the arithmetic mean roughness Ra of the GaN film support after the silicon oxide film was CMP polished was 0.3 nm.

[0112] The arithmetic mean roughness Ra of the GaN thin film surface of the obtained GaN stacked substrate was 80 nm. In addition, the crystallinity of the GaN thin film of the obtained GaN stacked substrate was evaluated by the X-ray rocking curve method in the same manner as in Example 1-1, and the result was FWHM 800 arcsec, indicating poor crystallinity.

[0113] In addition, the polarity of the surface of the GaN thin film was confirmed in the same manner as in Example 1-1, and it was found to be the Ga face.

[0114] The above results are shown in Table 1. It is understood that according to the present invention, a GaN multilayer substrate having excellent smoothness and crystallinity is obtained. It should be noted that the surface roughness Ra in the table is the arithmetic mean roughness Ra.

[0115] [Table 1]

[0116]

[0117] *: Full width at half maximum (FWHM) in the rocking curve (ω scan) of GaN (0002) surface reflection

[0118] It should be noted that the present invention has been described using the above-mentioned embodiment so far, but the present invention is not limited to this embodiment, and other embodiments, additions, changes, deletions, etc. can be changed within the scope that can be conceived by those skilled in the art, and all methods are included in the scope of the present invention as long as the effects of the present invention are achieved.

[0119] Description of Reference Numerals

[0120] 10 GaN composite substrate

[0121] 11 C-plane sapphire substrate

[0122] 11a Surface treatment layer

[0123] 12 Support base plate

[0124] 13 GaN film

[0125] 13a GaN thin film

[0126] 13 离子 Ion implantation area

Claims

1. A method for manufacturing a GaN stacked substrate, comprising: A step of performing a high-temperature nitridation treatment at 800 to 1000° C. on a C-plane sapphire substrate with an offset angle of 0.5 to 5 degrees and / or a deposition treatment of crystalline AlN on the C-plane sapphire substrate to perform surface treatment on the C-plane sapphire substrate; The step of epitaxially growing GaN on the surface of the surface-treated C-plane sapphire substrate to form a GaN film having an N-polar surface on the surface, thereby preparing a GaN film support; A step of performing ion implantation on the GaN film of the GaN film support to form an ion implantation region; The step of laminating and bonding the GaN film side surface of the ion-implanted GaN film support to a supporting substrate; and The ion implanted region in the GaN film is peeled off to transfer the GaN thin film onto a supporting substrate, thereby obtaining a GaN multilayer substrate having a GaN thin film having a Ga polar surface on the supporting substrate.

2. The method for manufacturing a GaN multilayer substrate according to claim 1, wherein: The GaN epitaxial growth is performed at a higher temperature than the high temperature nitridation process.

3. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: The epitaxial growth of GaN is carried out by MOCVD method.

4. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: After the C-plane sapphire substrate is surface treated, a GaN buffer layer is formed at a temperature below 700° C., and then the GaN epitaxial growth is performed on the GaN buffer layer.

5. The method for manufacturing a GaN multilayer substrate according to claim 4, wherein: The thickness of the GaN buffer layer is 15-30 nm.

6. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: After a GaN film is formed by the epitaxial growth, a silicon oxide film is further formed on the GaN film to prepare the GaN film support.

7. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: Before the ion implantation, the ion implantation surface of the GaN film support is further smoothed to an arithmetic mean roughness Ra of less than 0.3 nm.

8. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: The ion implantation uses hydrogen ions (H + ) and / or hydrogen molecular ions (H2 + ), implantation energy 100~160keV, dose 1.0×10 17 ~3.0×10 17 Atom / cm 2 processing.

9. The method for manufacturing a GaN multilayer substrate according to claim 1 or 2, wherein: The supporting substrate comprises Si, Al2O3, SiC, AlN or SiO2.

10. The method for manufacturing a GaN multilayer substrate according to claim 9, wherein: The supporting substrate is a product in which a silicon oxide film is formed on the bonding surface with the GaN film support body, but does not include the case where the supporting substrate is composed of SiO2.

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