Method for manufacturing heteroepitaxial wafers

Abstract

The present invention is a method for producing a heteroepitaxial wafer by heteroepitaxially growing a 3C-SiC single crystal film on a single crystal silicon substrate, the method comprising a first step for removing a native oxide film on the surface of the single crystal silicon substrate by hydrogen baking using a reduced-pressure CVD device, and a second step for supplying a source gas containing carbon and silicon into the reduced-pressure CVD device to form the 3C-SiC single crystal film having such wettability that the contact angle of a liquid on the surface becomes 50° or less. According to this configuration, a method for producing a heteroepitaxial wafer is provided, which makes it possible to produce a wafer in which a good-quality GaN or the like can be heteroepitaxially grown on a 3C-SiC single crystal film formed on a single crystal silicon substrate.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a heteroepitaxial wafer by heteroepitaxially growing a 3C-SiC single crystal film on a single crystal silicon substrate. [Background technology]

[0002] Due to its excellent thermal conductivity, chemical stability in high-temperature environments, and wider bandgap compared to silicon, 3C-SiC is highly effective as a device substrate for power devices, high-frequency devices, and devices used in radiation environments. For this reason, heteroepitaxial growth on silicon substrates has been widely studied (Non-Patent Document 1).

[0003] A common method for heteroepitaxial growth employs a two-stage process. This method involves silicon carbide followed by SiC growth. CVD uses gases such as SiH4 or chlorosilane as the silicon source and gases such as C3H8 or CH4 as the carbon source. These gases are typically reacted at temperatures above 1200°C. However, the high temperatures used for growth present a problem: tensile stress is generated due to the difference in lattice constants between Si and SiC.

[0004] Therefore, in order to avoid this problem as much as possible, low-temperature growth using a reduced-pressure CVD apparatus has been developed (Non-Patent Literature 2). This method involves using a vacuum CVD apparatus for silicon carbide treatment and subsequent SiC growth, growing at low temperatures below 1000°C by diluting trimethylsilane or monomethylsilane gas with hydrogen. This method is said to enable high-quality, low-stress 3C-SiC epitaxial growth by reducing the temperature during CVD growth, which is typically exposed to high temperatures for extended periods.

[0005] Furthermore, a method has been proposed that does not require the carbonization treatment of silicon, which is necessary at high temperatures (Non-Patent Document 3). This method involves placing a silicon substrate under high vacuum (7 × 10-5 Pa(5×10 -7 This method involves heating to 900-1000°C at a temperature (less than Torr) and growing the film using disilabutane as the raw material gas. It does not include a carbonization process and allows for film formation in a relatively low-temperature environment.

[0006] Furthermore, substrates in which GaN is grown after SiC is grown on silicon have been reported. GaN possesses excellent high-frequency characteristics and Johnson exponents, an indicator of high-power devices. Due to these superior characteristics, it has recently attracted attention as a high-frequency device substrate with 5G in mind. However, freestanding GaN substrates have not yet been realized in large diameters, posing a problem in terms of mass production. Therefore, numerous studies have shown that heteroepitaxial growth on inexpensive substrates such as Si is possible. In this heteroepitaxial growth on silicon, it has been reported that SiC is grown between silicon and GaN (Non-Patent Literature 4).

[0007] This report suggests that cracking in the GaN layer can be prevented by forming a SiC layer as an intermediate layer between silicon and GaN. This is because the cracking occurs not during epitaxial growth, but during the cooling process after epitaxial growth. Specifically, the coefficient of thermal expansion of 3C-SiC is 4.6 × 10⁻⁶. -6 K -1 In contrast, Si is 4.2 × 10 -6 K -1 GaN is 5.59 × 10⁻⁶ -6 K -1 Therefore, it is thought that 3C-SiC has intermediate values ​​between Si and GaN, which helps to mitigate thermal shrinkage during substrate cooling after epitaxial growth.

[0008] There are various reports on GaN growth on SiC, but it is generally believed that high-quality GaN growth is possible by performing surface modification (pretreatment) by flowing a gas such as trimethylaluminum before GaN growth (Non-Patent Document 5). Non-patent document 5 states that the surface of SiC is "the poor wetting" because the surface is modified by pre-treating it with a gas such as trimethylaluminum before GaN growth. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] J. Crystal. Growth, 154, 303 (1995) [Non-Patent Document 2] J. Electrochem. Soc, 139, 3565 (1992) [Non-Patent Document 3] J. Crystal. Growth, 179, 153 (1997) [Non-Patent Document 4] Appl. Phys. Lett., 88, 091901(2006) [Non-Patent Document 5] Jpn. J. Appl. Phys., 55, 05FB06 (2016) [Overview of the project] [Problems that the invention aims to solve]

[0010] Thus, heteroepitaxial substrates, in which SiC is grown on a silicon substrate followed by GaN growth, are very attractive because they can be made into large diameters, such as 300 mm. However, SiC epitaxial growth can be high-temperature, and pretreatment is particularly necessary for GaN growth. Furthermore, even with pretreatment, GaN cannot always be grown on SiC, and finding the optimal growth process conditions has required considerable effort.

[0011] The present invention has been made to solve the above problems, and an object thereof is to provide a method for manufacturing a heteroepitaxial wafer capable of obtaining a wafer on which high-quality GaN or the like can be heteroepitaxially grown on a 3C-SiC single crystal film formed on a single crystal silicon substrate.

Means for Solving the Problems

[0012] In order to achieve the above object, the present invention is a method for manufacturing a heteroepitaxial wafer in which a 3C-SiC single crystal film is heteroepitaxially grown on a single crystal silicon substrate, using a reduced-pressure CVD apparatus, a first step of removing the natural oxide film on the surface of the single crystal silicon substrate by hydrogen baking, a second step of supplying a source gas containing carbon and silicon into the reduced-pressure CVD apparatus and forming the 3C-SiC single crystal film having a wettability such that the contact angle with the liquid on the surface is 50° or less, and provides a method for manufacturing a heteroepitaxial wafer, characterized by including the above steps.

[0013] Thus, by removing the natural oxide film on the surface of the single crystal silicon substrate in the first step, it becomes possible to form a 3C-SiC single crystal film (nucleation stage, film formation stage) in the second step. Also, as the film formation conditions in the second step, by newly using the wettability (contact angle) of the surface of the 3C-SiC single crystal film as an index, it is possible to more easily and surely perform heteroepitaxial growth on the subsequent 3C-SiC single crystal film, and a heteroepitaxial wafer can be obtained. In particular, even without performing the pretreatment that has been carried out by the conventional method, a heteroepitaxial wafer capable of heteroepitaxially growing high-quality GaN can be more surely obtained. Therefore, labor and costs can be reduced.

[0014] At this time, the contact angle as an index of the wettability of the 3C-SiC single crystal film can be the contact angle when H2O is used as the liquid.

[0015] If the contact angle when using H2O is used as an index, for example, it is convenient when measuring the contact angle for confirmation after film formation.

[0016] Further, as the second step, it includes a nucleation step of forming nuclei of SiC on the single crystal silicon substrate, and a film formation step of growing a SiC single crystal to form the 3C-SiC single crystal film. The nucleation step can be carried out under the condition of isothermal holding in the range where the pressure is 13332 Pa or less and the temperature is 300 °C or more and 950 °C or less.

[0017] In this way, the nucleation of SiC can be carried out more efficiently. Also, a heteroepitaxial wafer with a contact angle of 50° or less as described above can be obtained more reliably.

[0018] Further, the film formation step can be carried out under the conditions where the pressure is 6666 Pa or less and the temperature is 800 °C or more and 1200 °C or less.

[0019] Under these growth conditions, it is possible to make the epitaxial growth rate-limiting by the transport of the supply gas, enable layer-by-layer epitaxial growth, and reliably control the surface free energy to a state particularly suitable for GaN growth. Also, the generation of slip dislocations can be prevented. Also, while growing the 3C-SiC single crystal film, voids can be formed in the silicon layer (single crystal silicon substrate) directly under this 3C-SiC single crystal film. The presence of these voids can not only relax the lattice mismatch between 3C-SiC and silicon, but also relax the stress of the entire epitaxial layer, so that it is also possible to more reliably form a 3C-SiC single crystal film without crystal defects even for a thick 3C-SiC single crystal film.

[0020] Further, the first step can be carried out under the condition where the temperature is 1000 °C or more and 1200 °C or less.

[0021] This method allows for more efficient removal of the native oxide film on the surface of a single-crystal silicon substrate and prevents the occurrence of slip dislocations.

[0022] Monomethylsilane or trimethylsilane can be used as the source gas.

[0023] With such a raw material gas, both Si and C can be supplied by a single gas, eliminating the need for a carbonization process before 3C-SiC single crystal film growth, which involves nucleating carbon atoms on the surface of a single-crystal silicon substrate using a gas containing a carbon source precursor. This allows for the formation of 3C-SiC single crystal films under very simple conditions. Furthermore, compared to a method in which carbon atoms are first deposited onto the surface of a single-crystal silicon substrate using a gas containing a carbon source precursor to form a nucleation, and then a 3C-SiC single crystal film is formed using a gas containing both a carbon source precursor and a silicon source precursor, this method makes it easier to control the reactive species in the gas phase, making heteroepitaxial growth more reliable, and facilitating the formation of thick 3C-SiC single crystal films without stopping the growth of the 3C-SiC single crystal.

[0024] Furthermore, a GaN layer can be formed by growing GaN on the surface of the deposited 3C-SiC single crystal film.

[0025] This invention is particularly effective when forming a GaN layer on a single-crystal silicon substrate using a 3C-SiC single-crystal film as an intermediate layer, and it allows for obtaining a GaN layer with better film quality more easily and reliably than conventional methods. [Effects of the Invention]

[0026] The present invention provides a heteroepitaxial wafer manufacturing method that has a 3C-SiC single crystal film on a single crystal silicon substrate and is suitable for heteroepitaxial growth of high-quality GaN or the like on the 3C-SiC single crystal film. Furthermore, it is possible to provide a heteroepitaxial wafer in which a GaN layer is further formed on the 3C-SiC single crystal film. [Brief explanation of the drawing]

[0027] [Figure 1] This graph shows an example of the 3C-SiC growth sequence in the heteroepitaxial wafer manufacturing method of the present invention. It also shows the 3C-SiC growth sequence in Example 1. [Figure 2] This graph shows the results of in-plane XRD analysis of 3C-SiC on Si(111) grown using the 3C-SiC growth sequence of Example 1. [Figure 3] This is a cross-sectional TEM image of GaN on 3C-SiC on Si(111) grown on a 3C-SiC single crystal film of Example 1. [Figure 4] This graph shows the XRD rocking curve of GaN grown on a 3C-SiC single crystal film in Example 1. [Figure 5] This graph shows the 3C-SiC growth sequence in a comparative example. [Figure 6] This graph shows the results of in-plane XRD analysis of 3C-SiC on Si(111) grown using the comparative 3C-SiC growth sequence. [Figure 7] This is a cross-sectional TEM image of GaN on 3C-SiC on Si(111) grown on a comparative 3C-SiC single crystal film. [Figure 8] This graph shows the XRD rocking curve of GaN grown on a 3C-SiC single crystal film in a comparative example. [Figure 9] This is an explanatory diagram of the contact angle. [Figure 10] This is a schematic diagram of the gas phase growth (BCF) model. [Best Mode for Carrying Out the Invention]

[0028] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. There has been a demand for a method for manufacturing a heteroepitaxial wafer capable of forming a 3C-SiC single crystal film on a single crystal silicon substrate and further forming a high-quality GaN or the like on the 3C-SiC single crystal film. As a result of intensive research by the present inventors, in order to manufacture a heteroepitaxial wafer that meets the above requirements, it is necessary to use the wettability (contact angle) of the surface as an index in the formation of the 3C-SiC single crystal film. Furthermore, it has been found that the contact angle as the wettability needs to be 50° or less, and the present invention has been completed.

[0029] Actually, even when the SiC surface is treated using hydrofluoric acid, hydrofluoric nitric acid, aqua regia, or high-temperature annealing at 1150°C with H2 (annealing at 1150°C because the substrate is a silicon substrate), the wettability of the SiC surface does not change, and it was impossible to control the wettability of the surface like silicon in the post-treatment after film formation.

[0030] Here, the contact angle will be explained. As shown in FIG. 9, the contact angle refers to the angle on the side containing the liquid among the angles formed by the tangent drawn to the liquid at the contact point of the three phases of solid, liquid, and gas when there is a liquid on the solid surface in the air. And this contact angle is determined by the surface tension of the liquid (for example, H2O in this case) and the surface tension of the solid surface (in the case of the present invention, the 3C-SiC surface) and the interfacial tension between the solid and the liquid, as shown by Young's equation represented by the following (Equation 1). Here, the surface tension of the solid and the liquid is generated by the intermolecular force (van der waals force) in the bulk emerging at the surface that is the interface (surface free energy). From this, it can also be understood that the growth conditions of the epitaxial layer (bulk) affect the contact angle. γ S =γ L ·cosθ+γ SL …(Equation 1) Here, Contact angle: θ Surface tension of the solid: γ S Surface tension of the liquid: γ L Interfacial tension between the solid and the liquid: γ SL

[0031] Because the 3C-SiC single crystal film grown in this manner has a controlled contact angle, i.e., surface free energy, it serves as a suitable substrate for heteroepitaxial growth (especially GaN growth) on which it is grown.

[0032] In fact, Figure 10 shows the generally accepted epitaxial growth model, the gas phase growth (BCF) model (Phil. Trans. Royal Soc. London, 243, 299-358 (1951)), in which epitaxial growth is represented by the following equation (Equation 2).

number

[0033] Here, the surface concentration of the active species can be written as follows, in such a way that surface tension is influencing it.

number

[0034] As shown in (Equation 3), it is clear that surface tension affects epitaxial growth.

[0035] The following describes a method for manufacturing heteroepitaxial wafers with specific examples, but the present invention is not limited thereto. Figure 1 shows an example of a 3C-SiC growth sequence. The sequence consists of the first step, hydrogen baking (hereinafter also called H2 annealing), and the second step of the 3C-SiC single crystal film deposition process (nucleation stage where SiC nuclei are formed, and film deposition stage where SiC single crystals are grown to form a 3C-SiC single crystal film). Each step is described below. <First step> First, a single-crystal silicon substrate is placed in a reduced-pressure CVD apparatus (hereinafter also referred to as an RP-CVD apparatus), hydrogen gas is introduced, and the native oxide film on the surface is removed by H2 annealing. If the oxide film remains, SiC nucleation on the single-crystal silicon substrate will not be possible. At this time, it is preferable to perform the H2 annealing under conditions such as a temperature of 1000°C to 1200°C. Setting the temperature above 1000°C prevents the processing time required to prevent the residue of the native oxide film from becoming long, making it efficient. Also, setting the temperature below 1200°C effectively prevents the generation of slip dislocations due to high temperatures. However, there are no particular restrictions on the pressure or time of the H2 annealing at this time, as long as the native oxide film is removed. In the example shown in Figure 1, H2 annealing is performed at 1080°C for 1 minute. Furthermore, hydrogen gas introduction can continue after this first step, as well as in the second step (carrier gas).

[0036] <Second stage (nucleation stage)> Next, the single-crystal silicon substrate is set to a predetermined pressure and temperature, and a source gas containing carbon and silicon is introduced into the RP-CVD apparatus as a raw material gas for SiC to form SiC nucleation. For example, monomethylsilane or trimethylsilane (TMS) can be introduced as the source gas. This method is simpler and easier to control than using multiple types of gases, and allows for more reliable formation of 3C-SiC single-crystal films. Compared to Si, carbon atoms are smaller and more easily vaporized, so trimethylsilane makes it even easier to set the conditions when considering raw material efficiency. The introduction of such source gases takes place during the nucleation stage of this second step and the subsequent membrane formation stage.

[0037] Furthermore, this SiC nucleation can be efficiently carried out on the surface of a single-crystal silicon substrate under conditions such as a pressure of 13332 Pa (100 Torr) or less and a constant temperature range of 300°C to 950°C. By setting the SiC nucleation stage to a temperature of 950°C or lower, it is possible to more reliably prevent the reaction between the single-crystal silicon substrate and the source gas from proceeding too quickly due to excessively high temperatures, which would prevent SiC nucleation on the single-crystal silicon substrate surface. Furthermore, it is possible to more reliably obtain wettability such that the contact angle with the liquid is 50° or less on the surface of the 3C-SiC single-crystal film after deposition. In particular, by setting the temperature to 900°C or lower, it is possible to easily obtain wettability with a contact angle of 40° or less. The above liquid is not particularly limited, but generally H2O can be used. If H2O is used, it can be easily prepared and measured when checking the contact angle after film formation. Furthermore, by setting the temperature above 300°C, it is possible to more reliably prevent the nucleation of SiC from becoming inefficient due to temperatures being too low.

[0038] Furthermore, considering the film formation stage described next, setting the temperature to 800°C or higher during the film formation stage allows for efficient heteroepitaxial growth of SiC. Therefore, for example, the temperature for SiC nucleation can be set from the nucleation stage to preferably 800°C to 950°C, more preferably 850°C to 900°C. By setting the temperature for the nucleation stage to 800°C to 950°C in this way, the preferred temperature ranges for the SiC nucleation stage and the subsequent film formation stage (3C-SiC single crystal film formation) can overlap, and in particular, these nucleation and film formation stages can be performed under the same temperature conditions.

[0039] Furthermore, by keeping the pressure below 13332 Pa (100 Torr), it is possible to prevent secondary or higher-order reactions, such as the reaction of reactive species with the source gas in the gas phase, thus making the process efficient. More preferably, the pressure can be set to 133 Pa (1 Torr) or less, which is even more efficient. The lower limit of the pressure is not particularly limited, but for example, it can be set to 13.3 Pa (0.1 Torr). Note that, similar to temperature, the same pressure conditions can be maintained for both the nucleation stage and the film formation stage. In the example shown in Figure 1, the nucleation stage and the subsequent membrane formation stage are under identical conditions, with the same pressure and the same holding temperature (900°C).

[0040] <Second step (film formation stage)> Furthermore, the film formation stage, in which a 3C-SiC single crystal film is grown, can be carried out under conditions such as a pressure of 13332 Pa (100 Torr), or even 6666 Pa (50 Torr) or less, and a temperature of 800°C or higher but less than 1200°C. Under these conditions, SiC single crystals can be grown efficiently to form a 3C-SiC single crystal film. Furthermore, by setting the growth pressure to 13332 Pa (or even 6666 Pa) or less, it is possible to more reliably prevent the formation of polycrystalline 3C-SiC. If the pressure is 6666 Pa (50 Torr) or less, as mentioned above, secondary or even higher-order reactions in the gas phase can be suppressed, preventing polycrystalline formation of 3C-SiC and enabling the reliable and efficient formation of a 3C-SiC single crystal film. Preferably, the pressure can be 1333 Pa (10 Torr) or less, and even more preferably 133 Pa (1 Torr) or less. Under these conditions, vacancies are formed directly beneath the 3C-SiC single crystal film, providing the effect of relaxing the stress on the entire heteroepitaxial layer. The lower limit of the pressure is not particularly limited, but for example, it can be 13.3 Pa (0.1 Torr). Regarding temperature, setting it above 800°C allows for efficient growth of SiC single crystals, as mentioned earlier, while setting it below 1200°C effectively prevents the occurrence of slip dislocations. In the example shown in Figure 1, as mentioned above, the nucleation stage and the film formation stage are under the same conditions, and SiC nucleation and the formation of a 3C-SiC single crystal film occur sequentially.

[0041] Since the film thickness at this stage depends on pressure and temperature, the deposition time can be appropriately set based on the pressure and temperature conditions that are set to achieve the desired film thickness. In this case, the thickness of the 3C-SiC single crystal film can range from a thin film of about 2 nm to a thick film of several μm, and the surface contact angle is 50° or less, resulting in a surface free energy suitable for GaN growth, enabling layered growth in a two-dimensional growth mode.

[0042] Note that the layered growth shown in Figure 1 in the two-dimensional growth mode is Layer by Layer epitaxial growth.

[0043] A heteroepitaxial wafer formed with a 3C-SiC single crystal film grown in this manner, having a wettability of 50° or less (greater than 0°) contact angle with the surface liquid (H2O), is suitable for further forming a heteroepitaxial layer such as GaN on top of it. In other words, by growing GaN in particular on top of the 3C-SiC single crystal film, it becomes possible to obtain a heteroepitaxial wafer with a high-quality GaN layer. In this case, GaN growth was carried out by MOCVD using organometallic materials such as trimethylgallium and trimethylammonium to grow GaN to a thickness of approximately 3 μm. It is also possible to grow materials such as silicon heteroepitaxially instead of GaN. The smaller the contact angle, the more suitable the surface free energy becomes for GaN growth, allowing for the more reliable formation of a heteroepitaxial layer with superior film quality on a 3C-SiC single crystal film.

[0044] The contact angle can be measured using commercially available measuring devices, for example. An example is the PCA-11 from Kyowa Interface Science Co., Ltd. The measurement involves dropping 2.0 μL of pure water droplets at five locations on the surface of a 3C-SiC single crystal film, determining the contact angle from image analysis, and taking the average value. However, the measurement method is not limited to this.

[0045] As described above, although the growth sequence shown in Figure 1 has been explained, the conditions for film formation in the heteroepitaxial wafer manufacturing method of the present invention are not limited to the pressure and temperature ranges mentioned above. Any film formation conditions that result in a contact angle of 50° or less on the surface of the 3C-SiC single crystal film after formation are acceptable, and various condition patterns for heteroepitaxial growth of the 3C-SiC single crystal film can be considered and determined as appropriate. For example, the correlation between the pressure and temperature conditions during 3C-SiC single-crystal film deposition and the contact angle on the surface of the 3C-SiC single-crystal film after deposition can be determined in advance through tests conducted with varying pressure and temperature conditions. When actually manufacturing the product, the pressure and temperature conditions for 3C-SiC single-crystal film deposition can be set based on this correlation to ensure that the contact angle after deposition is 50° or less. The inventors' discovery that using the contact angle as an indicator for heteroepitaxial growth of 3C-SiC single crystal films is extremely effective for further forming heteroepitaxial layers such as GaN on top of them is itself of great significance. Since the manufacturing process only requires adjusting the conditions during film formation of the 3C-SiC single crystal film to satisfy the above-mentioned contact angle condition, there is no need for pretreatment as in the conventional method after film formation and before forming heteroepitaxial layers such as GaN, making the process easy and ensuring the reliable acquisition of high-quality heteroepitaxial films such as GaN. [Examples]

[0046] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited thereto. (Example 1) A 300 mm diameter, (111) orientation, boron-doped, high-resistivity single-crystal silicon substrate was prepared. The wafer was placed on a susceptor in the reactor of the RP-CVD apparatus, and H2 annealing was performed at 1080°C for 1 minute as shown in the growth sequence in Figure 1 (first step). Subsequently, trimethylsilane gas was introduced at a growth temperature of 900°C and a growth pressure of 6666 Pa (50 Torr) to perform SiC nucleation and growth of a 3C-SiC single crystal film (nucleation and film formation stages of the second step). After 5 minutes of growth, the film thickness was 13 nm.

[0047] Subsequently, when the XRD (X-ray diffraction) spectrum was examined in a plane configuration, a 3C-SiC(220) peak parallel to Si(220) was observed, as shown in the graph of the XRD analysis results in Figure 2, confirming that a single-crystal 3C-SiC film was growing. The contact angle of the deposited 3C-SiC single crystal film was 19.7°. This contact angle was measured using the PCA-11 from Kyowa Interface Science Co., Ltd. The measurement was performed by dropping 2.0 μL of pure water droplets at five locations on the surface of the 3C-SiC single crystal film, determining the contact angle from image analysis, and then taking the average value.

[0048] Furthermore, we attempted to grow GaN on a 3C-SiC single crystal film. More specifically, this growth substrate (single-crystal silicon substrate + 3C-SiC single-crystal film) was placed in an MOCVD reactor, and epitaxial growth of group 3 nitride semiconductor thin films such as AlN, AlGaN, and GaN was performed on the growth substrate. The growth substrate was placed in a wafer pocket called a satellite. During epitaxial growth, TMAl was used as the Al source, TMGa as the Ga source, and NH3 as the N source.

[0049] Furthermore, both N2 and H2 were used as carrier gases. The process temperature was set to approximately 900-1200°C. When epitaxial growth was performed with the growth substrate placed on the satellite, the epitaxial layer was deposited by sequentially depositing AlN and AlGaN from the substrate side toward the growth direction, followed by epitaxial growth of GaN.

[0050] Figure 3 shows a cross-sectional TEM image of the grown GaN, and Figure 4 shows the XRD rocking curve. As shown in Figure 3, no three-dimensional island-like growth was observed, unlike in the comparative example described later. Also, in Figure 4, the full width at half maximum (FWHM) of the peak value of the rocking curve (when omega = 17.35°) was 774 seconds, which was significantly narrower than the FWHM in the comparative example. Thus, a GaN film with good crystalline properties was successfully grown.

[0051] (Comparative example) A 300 mm diameter, (111) orientation, boron-doped, high-resistivity single-crystal silicon substrate was prepared. The wafer was placed on a susceptor in the reactor of the RP-CVD apparatus, and H2 annealing was performed at 1080°C for 1 minute as shown in the growth sequence in Figure 5. Subsequently, the furnace temperature was lowered to 300°C, and then trimethylsilane gas was introduced while increasing the temperature to 1130°C at a rate of 1°C / sec to induce SiC nucleation and subsequent formation of a 3C-SiC single crystal film. The growth pressure at this time was uniformly set to 133 Pa (1 Torr). After reaching 1130°C, the temperature was held for 10 minutes to grow the 3C-SiC single crystal film, resulting in a film thickness of approximately 100 nm.

[0052] After film deposition, the XRD spectrum was examined in an in-plane configuration. As shown in the graph of the XRD analysis results in Figure 6, a 3C-SiC(220) peak parallel to Si(220) was observed, confirming that a single-crystal 3C-SiC film had grown. The contact angle of the deposited 3C-SiC film surface was measured in the same manner as in Example 1, and the contact angle was found to be 66.8°.

[0053] Furthermore, we attempted to grow GaN on a 3C-SiC single crystal film under the same conditions as in Example 1. Figure 7 shows a cross-sectional TEM image of the grown GaN, and Figure 8 shows the XRD rocking curve. As shown in Figure 7, the GaN grew in a three-dimensional island-like structure. Also, in Figure 8, the full width at half maximum (FWHM) of the peak value of the rocking curve (when omega = 17.32°) was 3321 seconds, which was broad. Thus, a GaN film with good crystalline properties could not be obtained.

[0054] (Example 2) A single-crystal silicon substrate similar to that in Example 1 was prepared, and the wafer was placed on the susceptor in the reactor of the RP-CVD apparatus. H2 annealing was performed at 1080°C for 1 minute (first step). Subsequently, as the nucleation step of the second step, trimethylsilane gas was introduced at a growth temperature of 900°C for 5 minutes. Next, as the film formation step of the second step, the growth temperature was raised to 1190°C and trimethylsilane gas was introduced to grow a 3C-SiC single crystal film. The growth pressure at this time was uniformly set to 133 Pa (1 Torr). After 1 minute of growth, the film thickness was approximately 50 nm.

[0055] After film deposition, XRD spectroscopy was performed in an in-plane configuration, revealing a 3C-SiC(220) peak parallel to Si(220), confirming the growth of a single-crystal 3C-SiC film. The contact angle of the deposited 3C-SiC film surface was measured in the same manner as in Example 1, and the contact angle was found to be 50°.

[0056] Furthermore, when we attempted to grow GaN on a 3C-SiC single crystal film under the same conditions as in Example 1, we were able to obtain a GaN film with good crystallinity. Although not as good as in Example 1, it had superior crystallinity compared to the comparative example.

[0057] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that has substantially the same technical idea as described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A method for manufacturing a heteroepitaxial wafer, comprising heteroepitaxially growing a 3C-SiC single crystal film on a single crystal silicon substrate, Using a vacuum CVD apparatus, A first step is to remove the native oxide film on the surface of the single-crystal silicon substrate with a surface orientation (111) by hydrogen baking, A source gas containing carbon and silicon is supplied into the vacuum CVD apparatus, and the liquid on the surface (H ２ A second step involves forming the 3C-SiC single crystal film having wettability such that the contact angle with O) is 50° or less, Includes, The second step includes a nucleation step in which SiC is nucleated on the single-crystal silicon substrate, and a film formation step in which a SiC single crystal is grown to form the 3C-SiC single crystal film. The nucleation step is carried out under conditions of constant temperature maintenance within the range of 300°C to 950°C, with a pressure of 13332 Pa or less and a temperature of 300°C to 950°C. A method for manufacturing a heteroepitaxial wafer, characterized in that the film formation step is carried out under conditions of a pressure of 6666 Pa or less and a temperature of 800°C to 1200°C, thereby forming vacancies directly beneath the 3C-SiC single crystal film.

2. The method for manufacturing a heteroepitaxial wafer according to claim 1, characterized in that the film formation step is carried out under conditions where the pressure is 1333 Pa or less.

3. The method for manufacturing a heteroepitaxial wafer according to claim 1, characterized in that the first step is carried out under conditions where the temperature is 1000°C or higher and 1200°C or lower.

4. The method for manufacturing a heteroepitaxial wafer according to claim 2, characterized in that the first step is carried out under conditions where the temperature is 1000°C or higher and 1200°C or lower.

5. A method for manufacturing a heteroepitaxial wafer according to any one of claims 1 to 4, characterized in that monomethylsilane or trimethylsilane is used as the source gas.

6. A method for manufacturing a heteroepitaxial wafer according to any one of claims 1 to 4, characterized in that a GaN layer is formed by further growing GaN on the surface of the deposited 3C-SiC single crystal film.

7. The method for manufacturing a heteroepitaxial wafer according to claim 5, characterized in that a GaN layer is formed by further growing GaN on the surface of the deposited 3C-SiC single crystal film.

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