3C-SiC epitaxial layer and preparation method thereof

Abstract

The invention provides a 3C-SiC epitaxial layer and a preparation method thereof, and the preparation method comprises the steps: firstly, placing a 4H-SiC substrate in a reaction chamber, and carrying out the homoepitaxial growth on the surface of the 4H-SiC substrate to obtain a 4H-SiC buffer layer; secondly, performing heteroepitaxial growth on the surface of the 4H-SiC buffer layer to obtain a sacrificial layer made of a C or Si material; thirdly, completely converting the sacrificial layer into a 3C-SiC buffer layer by adjusting process parameters of the reaction chamber; and finally, carrying out homoepitaxial growth on the surface of the 3C-SiC buffer layer to obtain a 3C-SiC epitaxial layer. The sacrificial layer made of C or Si is introduced to the surface of the 4H-SiC substrate, the key effect that the sacrificial layer passivates the activity of atomic steps on the surface of 4H-SiC is utilized, the multi-type mixing phenomenon is reduced fundamentally, and therefore the growth quality and the yield of the 3C-SiC epitaxial layer are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor materials, and particularly relates to a 3C-SiC epitaxial layer and a preparation method thereof. BACKGROUND

[0002] The core advantage of 3C-SiC (cubic silicon carbide) over 4H-SiC (hexagonal silicon carbide) lies in its physical properties and application potential. In terms of electron mobility, the carrier mobility of 3C-SiC is significantly higher (its electron mobility can reach about 1000 cm 2 / V·s, which is better than 950 cm 2 / V·s of 4H-SiC), and is particularly suitable for medium and low voltage high frequency power devices, which can reduce the on-resistance and switching loss. In terms of band gap characteristics, the smaller band gap (about 2.3 eV) of 3C-SiC is conducive to realizing devices with lower threshold voltage. The material isotropy enables it to have uniform electrical performance in any crystal direction, simplifying device design and process integration. In particular, in terms of heteroepitaxy compatibility, 3C-SiC can be directly grown on a silicon substrate (growth temperature about 1300℃), which greatly reduces the cost and promotes the development of "3C-SiC-on-Si" technology, providing a cost-effective solution for consumer electronics and the Internet of Things.

[0003] However, "3C-SiC-on-Si" can generate a large internal stress and defect density, which greatly reduces the reliability of the device, so that "3C-SiC-on-Si" technology cannot be applied to the vehicle level field. However, 4H-SiC and 3C-SiC have almost the same expansion coefficient and lattice coefficient, and perfect 3C-SiC can be grown on a 4H-SiC substrate. At present, the epitaxial growth of 3C-SiC on a 4H-SiC substrate relies on the "step regulation" mechanism: the mesa length of the atomic step on the 4H-SiC surface is expanded through annealing or surface treatment technology, so that the silicon-carbon atomic clusters in the growth process nucleate on the mesa, and the silicon-carbon atoms nucleated on the mesa are more likely to form 3C-SiC phase. However, this method cannot completely avoid the nucleation of 4H-SiC, resulting in a low mixed product yield.

[0004] Therefore, there is an urgent need for a 3C-SiC epitaxial layer and a preparation method thereof to solve the technical problems. SUMMARY

[0005] The purpose of the present application is to provide a 3C-SiC epitaxial layer and a preparation method thereof to overcome the technical problem of low growth quality of the existing 3C-SiC epitaxial layer.

[0006] To solve the above technical problems, the present application first provides a preparation method of a 3C-SiC epitaxial layer, comprising the following steps: S10, placing a 4H-SiC substrate into a reaction chamber and growing a 4H-SiC buffer layer on the surface of the 4H-SiC substrate by homoepitaxy; S20, growing a sacrificial layer of C or Si on the surface of the 4H-SiC buffer layer by heteroepitaxy; S30, converting the sacrificial layer into a 3C-SiC buffer layer by adjusting the process parameters of the reaction chamber; S40, growing a 3C-SiC epitaxial layer on the surface of the 3C-SiC buffer layer by homoepitaxy.

[0007] In particular, since semiconductor processes are extremely sensitive to additional impurity elements, only C or Si layers can be used as the sacrificial layer, and the use of other elements will greatly deteriorate the physical properties of silicon carbide.

[0008] Preferably, the growth conditions of the 4H-SiC buffer layer in the S10 step are as follows: the growth pressure is 50-200 mbar, the growth temperature is 1500-1650°C, the growth time is 30-60 min, the dilute hydrogen gas is 50-100 slm, the carbon source flow rate is 20-100 sccm, the silicon source flow rate is 50-200 sccm, and the carbon-to-silicon ratio of the carbon source and the silicon source is 0.8-1.2.

[0009] Preferably, when the material of the sacrificial layer is C, the growth conditions of the sacrificial layer in the S20 step are as follows: the growth pressure is 20-50 mbar, the growth temperature is 1400-1600°C, the growth time is 30-60 min, the dilute hydrogen gas is 20-50 slm, the dilute argon gas is 20-40 slm, and the carbon source flow rate is 10-40 sccm.

[0010] Preferably, the conversion conditions of the 3C-SiC buffer layer in the S30 step are as follows: the growth pressure is 50-200 mbar, the growth temperature is 1500-1650°C, the growth time is 2-5 min, the dilute hydrogen gas is 50-100 slm, the carbon source flow rate is 20-100 sccm, the silicon source flow rate is 50-200 sccm, and the carbon-to-silicon ratio of the carbon source and the silicon source is 0.7-0.9.

[0011] Preferably, when the material of the sacrificial layer is Si, the growth conditions of the sacrificial layer in the S20 step are as follows: the growth pressure is 50-100 mbar, the growth temperature is 1000-1200°C, the growth time is 30-60 min, the dilute hydrogen gas is 50-100 slm, and the silicon source flow rate is 10-30 sccm.

[0012] Preferably, the conversion conditions of the 3C-SiC buffer layer in the step S30 are as follows: the growth pressure is 50-100 mbar, the growth temperature is 1300-1400 ℃, the growth time is 5-10 min, the dilute hydrogen is 50-100 slm, the carbon source flow is 20-100 sccm, the silicon source flow is 50-200 sccm, and the carbon-silicon ratio of the carbon source and the silicon source is 1.1-1.3.

[0013] Preferably, the growth conditions of the 3C-SiC epitaxial layer in the step S40 are as follows: the growth pressure is 50-200 mbar, the growth temperature is 1400-1650 ℃, the growth time is 30-60 min, the dilute hydrogen is 50-100 slm, the carbon source flow is 20-80 sccm, the silicon source flow is 50-150 sccm, and the carbon-silicon ratio of the carbon source and the silicon source is 0.6-0.9.

[0014] Preferably, the carbon source includes any one of methane, ethane, propane and ethylene, and the silicon source includes any one of silicon tetrachloride, trichlorosilane, dichlorosilane and silane.

[0015] Preferably, the thickness of the 4H-SiC buffer layer is 6-12 μm, the thickness of the sacrificial layer is 10-30 nm when the material of the sacrificial layer is C, the thickness of the sacrificial layer is 0.2-0.5 μm when the material of the sacrificial layer is Si, and the thickness of the 3C-SiC epitaxial layer is 5-12 μm.

[0016] Correspondingly, the application further provides a 3C-SiC epitaxial layer prepared by any one of the above preparation methods of the 3C-SiC epitaxial layer.

[0017] The beneficial effects of the present application are: different from the prior art, the present application provides a 3C-SiC epitaxial layer and a preparation method thereof, comprising the following steps: firstly, placing a 4H-SiC substrate in a reaction chamber, and homoepitaxially growing a 4H-SiC buffer layer on the surface of the 4H-SiC substrate; secondly, heteroepitaxially growing a sacrificial layer of C or Si material on the surface of the 4H-SiC buffer layer; thirdly, completely converting the sacrificial layer into a 3C-SiC buffer layer by adjusting the process parameters of the reaction chamber; and finally, homoepitaxially growing a 3C-SiC epitaxial layer on the surface of the 3C-SiC buffer layer. The present application introduces a sacrificial layer of C or Si material on the surface of the 4H-SiC substrate, and uses the key role of the sacrificial layer in passivating the atomic step activity of the 4H-SiC surface to directly block the nucleation path of the silicon-carbon atomic cluster in the prior art, which replicates the 4H structure of the substrate, solves the problem of polymorphic hybridization caused by the difficulty of 4H-SiC nucleation due to the inability to eliminate active sites on the 4H-SiC surface in the prior art, after the sacrificial layer completely covers and passivates the substrate surface atoms, the silicon-carbon atomic cluster loses the condition to replicate the 4H structure and can only preferentially form 3C-SiC with lower energy, creating a uniform and single nucleation environment for 3C-SiC, reducing polymorphic hybridization from the root, and after the sacrificial layer is converted into a 3C-SiC buffer layer, subsequent homoepitaxial growth can continue relying on the stable 3C structure, ensuring the consistency of the phase during epitaxy, further reducing the probability of structure defects, thereby improving the purity and crystalline quality of the 3C-SiC epitaxial layer, and finally, the core defect of polymorphic hybridization is overcome, and the yield is effectively improved compared with the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A flow chart of the preparation method of the 3C-SiC epitaxial layer provided by the present application is provided. Figures 2A-2D A structure schematic diagram of each step in the preparation method of the 3C-SiC epitaxial layer provided by the present application is provided. Figure 3 A Raman spectrum of the sacrificial layer of C material in the preparation method of the 3C-SiC epitaxial layer provided by the present application is provided. Figure 4 An AFM graph of the sacrificial layer of C material in the preparation method of the 3C-SiC epitaxial layer provided by the present application is provided. Figure 5 An XRD spectrum of the 3C-SiC epitaxial layer on the 4H-SiC substrate in the preparation method of the 3C-SiC epitaxial layer provided by the present application is provided. Figure 6 A Raman spectrum of the 4H-SiC epitaxial layer prepared without using a sacrificial layer of C or Si material in Comparative Example 1 is provided. In the accompanying drawings: 10—4H-SiC substrate; 20—4H-SiC buffer layer; 30—sacrificial layer; 40—3C-SiC buffer layer; 50—3C-SiC epitaxial layer. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] To address the aforementioned technical problems, this invention first provides a method for preparing a 3C-SiC epitaxial layer. Please refer to [link / reference]. Figures 1 to 2D , Figure 1 A flowchart illustrating the fabrication process of the 3C-SiC epitaxial layer 50 provided by this invention; Figures 2A-2D This is a schematic diagram of the structure of the method for preparing the 3C-SiC epitaxial layer 50 provided by the present invention.

[0021] The preparation of the above-mentioned 3C-SiC epitaxial layer 50 includes the following steps: S10, a 4H-SiC substrate 10 is placed in the reaction chamber, and a 4H-SiC buffer layer 20 is homoepitaxially grown on the surface of the 4H-SiC substrate 10, as shown. Figure 2A As shown.

[0022] Specifically, step S10 also includes: First, the 4H-SiC substrate 10 is placed in a transfer chamber filled with argon gas. At this time, the reaction chamber is heated at a rate of 90°C / min. When the reaction chamber reaches the target temperature of 900°C, the 4H-SiC substrate 10 is placed into the reaction chamber using a transfer robot.

[0023] Specifically, the purpose of preheating the reaction chamber to the target temperature of 900℃ is to create a stable and suitable initial temperature environment for the homogeneous epitaxial growth of the 4H-SiC substrate 10 after it enters the reaction chamber. On the one hand, this avoids thermal stress caused by a sudden temperature rise after the 4H-SiC substrate 10 enters the reaction chamber, preventing cracking or structural defects and ensuring the integrity of the 4H-SiC substrate 10 itself. On the other hand, preheating the reaction chamber to the set temperature ensures that the 4H-SiC substrate 10 can immediately be in the temperature conditions required for epitaxial growth after it enters the chamber, reducing the impact of temperature fluctuations on the initial nucleation stage. This is conducive to the uniform and stable growth of the 4H-SiC buffer layer 20 on the surface of the 4H-SiC substrate 10, laying a high-quality underlying foundation for the subsequent preparation of the sacrificial layer and the growth of the 3C-SiC epitaxial layer 50, and indirectly improving the controllability of the entire epitaxial process and the quality of the final product.

[0024] Secondly, the growth process conditions of the 4H-SiC buffer layer 20 are set as follows: the growth pressure is 50-200 mbar, the growth temperature is 1500-1650℃, the growth time is 30-60 min, the dilute hydrogen flow is 50-100 slm, the carbon source flow is 20-100 sccm, the silicon source flow is 50-200 sccm, the carbon-silicon ratio of the carbon source and the silicon source is 0.8-1.2, and the thickness of the finally grown 4H-SiC buffer layer 20 is 6-12 μm.

[0025] Specifically, since the 4H-SiC substrate 10 contains a large number of dislocations, stacking faults and surface topography defects, growing the 4H-SiC buffer layer 20 can reduce the number of these defects and improve the quality of the finally obtained 3C-SiC epitaxial layer 50.

[0026] Further, the suitable growth pressure and the dilute hydrogen flow can optimize the stability of the gas atmosphere in the reaction chamber, avoiding uneven growth caused by turbulent gas flow; the high temperature of 1500-1650℃ can provide sufficient energy for the decomposition and migration of the silicon source and the carbon source, promoting the ordered arrangement of atoms on the substrate surface; the carbon-silicon ratio of 0.8-1.2 can balance the supply ratio of silicon and carbon atoms, reducing defects (such as vacancies, interstitial atoms, etc.) caused by component deviation; the growth time of 30-60 min and the thickness of 6-12 μm can not only ensure that the 4H-SiC buffer layer 20 fully covers the surface of the 4H-SiC substrate 10 and fills potential micro-defects, but also avoid the stress accumulation problem caused by over-thickness growth; the synergistic effect of these parameters can ensure that the 4H-SiC buffer layer 20 has uniform thickness, low defect density and good crystalline quality, providing a flat and stable substrate for the growth of the subsequent sacrificial layer, and further creating reliable preliminary conditions for the sacrificial layer to passivate the substrate surface activity and block the 4H-SiC nucleation, indirectly ensuring the growth quality of the subsequent 3C-SiC epitaxial layer 50.

[0027] In this step, the carbon source can be methane, ethane, propane or ethylene, etc., and the silicon source can be silicon tetrachloride, trichlorosilane, dichlorosilane or silane, etc.

[0028] S20, heteroepitaxially growing a sacrificial layer 30 made of C or Si on the surface of the 4H-SiC buffer layer 20, as shown in FIG. 2. Figure 2B

[0029] Specifically, the S20 step further includes: ​After the 4H-SiC homoepitaxial layer is grown, the process parameters are immediately changed to grow the carbon or silicon sacrificial layer 30. The growth conditions of the carbon and silicon sacrificial layer 30 are different and need to be described separately. It needs to be particularly emphasized that the material type of the sacrificial layer 30 can only be carbon or silicon. If other element sacrificial layers 30 are used, a large amount of impurity elements will be introduced into the 3C-SiC, which will deteriorate the final performance.

[0030] In this step, the core purpose of preparing the carbon or silicon sacrificial layer 30 is to create key conditions for the subsequent high-quality growth of 3C-SiC: on the one hand, the carbon or silicon sacrificial layer 30 can tightly cover the surface of the 4H-SiC buffer layer 20 and passivate the activity of the 4H-SiC surface atomic steps through its material properties—these active sites are the root cause of the difficulty in 4H-SiC nucleation in the prior art. The sacrificial layer 30 can block the path of silicon-carbon atomic clusters directly replicating the 4H structure of the substrate, eliminating the "basis" of 4H-SiC nucleation from the source; on the other hand, as a constituent element of 3C-SiC, the carbon or silicon sacrificial layer 30 can form a uniform interface during the covering process, providing a single and stable environment for 3C-SiC nucleation. Because it only contains carbon or silicon, it will not introduce impurities when it is converted into a 3C-SiC buffer layer in the subsequent process, avoiding the performance deterioration problem caused by other element sacrificial layers 30; at the same time, this uniform coverage can also ensure the consistency of the phase during the subsequent 3C-SiC homoepitaxial growth, reducing the mixing of multiple types, and ultimately laying a decisive foundation for the preparation of high-quality 3C-SiC epitaxial layer 50.

[0031] When the material of the sacrificial layer 30 is C, the growth conditions of the sacrificial layer 30 in step S20 are as follows: the growth pressure is 20-50 mbar, the growth temperature is 1400-1600°C, the growth time is 30-60 min, the dilute hydrogen gas is 20-50 slm, the dilute argon gas is 20-40 slm, and the carbon source flow is 10-40 sccm; the finally grown carbon material sacrificial layer 30 has a thickness of about 10-30 nm.

[0032] Specifically, the suitable growth pressure and hydrogen argon mixed dilution gas flow can optimize the diffusion and distribution of the carbon source in the reaction chamber, ensuring uniform deposition of carbon atoms on the surface of the 4H-SiC buffer layer 20; the high temperature of 1400-1600 ℃ provides energy for the decomposition of the carbon source and the dense growth of the carbon layer, promoting the ordered arrangement of carbon atoms to form a continuous and covered carbon sacrificial layer 30; the growth time of 30-60 min and the carbon source flow of 10-40 sccm work together to precisely control the thickness of 10-30 nm, which can fully cover the surface of the 4H-SiC buffer layer 20, completely passivate the activity of atomic steps, effectively block the 4H-SiC nucleation path, and will not cause stress problems due to excessive thickness when subsequently converted into a 3C-SiC buffer layer; at the same time, only the carbon source is introduced without other impurity elements, which can ensure the purity of the carbon sacrificial layer 30, create an impurity-free interface for the subsequent conversion into a 3C-SiC buffer layer, and ultimately provide a uniform environment for 3C-SiC nucleation, reduce polymorphism, and lay a reliable foundation for the growth of high-quality 3C-SiC epitaxial layer 50.

[0033] When the material of the sacrificial layer 30 is Si, the growth conditions of the sacrificial layer 30 in step S20 are as follows: the growth pressure is 50-100 mbar, the growth temperature is 1000-1200 ℃, the growth time is 30-60 min, the dilution hydrogen flow is 50-100 slm, and the silicon source flow is 10-30 sccm; the thickness of the Si material sacrificial layer 30 grown finally is about 0.2-0.5 μm. It should be noted that the Si material sacrificial layer 30 should not be too thick, otherwise it cannot be completely converted into silicon carbide.

[0034] Specifically, the suitable growth pressure and dilution hydrogen flow can optimize the diffusion and distribution of the silicon source in the reaction chamber, ensuring uniform deposition of silicon atoms on the surface of the 4H-SiC buffer layer 20; the temperature of 1000-1200 ℃ provides suitable energy for the decomposition of the silicon source and the stable growth of the silicon layer, promoting the ordered arrangement of silicon atoms to form a continuous and covered silicon material sacrificial layer 30; the growth time of 30-60 min and the silicon source flow of 10-30 sccm work together to precisely control the thickness of 0.2-0.5 μm, which can fully cover the surface of the 4H-SiC buffer layer 20, effectively passivate the activity of atomic steps, and block the 4H-SiC nucleation path; due to the limitation within this range, it can avoid being too thick, which can ensure that it can be completely converted into silicon carbide (if it is too thick, it cannot be completely converted); at the same time, only the silicon source is introduced without other impurity elements, which ensures the purity of the silicon sacrificial layer 30, creates an impurity-free interface for the subsequent conversion into a 3C-SiC buffer layer, and ultimately provides a uniform environment for 3C-SiC nucleation, reduces polymorphism, and lays a reliable foundation for the growth of high-quality 3C-SiC epitaxial layer 50.

[0035] S30, by adjusting the process parameters of the reaction chamber, to completely convert the sacrificial layer 30 into a 3C-SiC buffer layer 40.

[0036] Specifically, the S30 step further comprises: After the growth of the sacrificial layer 30 of carbon or silicon material is completed, the process parameters are immediately changed to convert the sacrificial layer 30 into a 3C-SiC buffer layer 40. The conversion conditions are slightly different and need to be described separately. The 3C-SiC buffer layer 40 can passivate the surface atoms of the 4H-SiC, so that the subsequent silicon-carbon atomic clusters cannot replicate the atomic template of the 4H-SiC substrate 10, and can only generate 3C-SiC with lower formation energy, as shown in the following figure. Figure 2C

[0037] Specifically, the core purpose of completely converting the sacrificial layer 30 into a 3C-SiC buffer layer 40 is to realize interface regulation and phase guidance through phase transformation, and to lay a foundation for the subsequent homoepitaxial growth of the 3C-SiC epitaxial layer 50: on the one hand, the conversion process can convert the material form of the sacrificial layer 30 of carbon or silicon material into a 3C-SiC structure, and further passivate the atomic activity on the surface of the 4H-SiC substrate 10 by using the 3C-SiC buffer layer 40. Compared with the original sacrificial layer 30 (C or Si), the 3C-SiC buffer layer 40, as the same phase structure as the target 3C-SiC epitaxial layer 50, can more stably block the nucleation path of 4H-SiC, avoid the silicon-carbon atomic clusters from replicating the 4H structure of the substrate, and force them to only generate 3C-SiC with lower formation energy; on the other hand, complete conversion can eliminate the phase difference between the sacrificial layer 30 and the subsequent epitaxial layer, form a continuous 3C-SiC structure transition, and ensure that there is no residual sacrificial layer 30 at the interface (if there is residual, it may cause impurities or structural defects), thereby providing a uniform and single phase template for the subsequent homoepitaxial growth of the 3C-SiC epitaxial layer 50, reducing the risk of polymorphism mixing, and ultimately ensuring the high-quality growth of the 3C-SiC epitaxial layer 50.

[0038] When the material of the sacrificial layer 30 is C, the conversion conditions of the 3C-SiC buffer layer 40 in the S30 step are as follows: the growth pressure is 50-200 mbar, the growth temperature is 1500-1650°C, the growth time is 2-5 min, the dilute hydrogen gas is 50-100 slm, the carbon source flow is 20-100 sccm, and the silicon source flow is 50-200 sccm; at this time, there is a carbon material sacrificial layer 30 on the 4H-SiC substrate 10, so more silicon source should be supplied in the supply of the precursor, and finally the carbon-silicon ratio is set to 0.7-0.9.

[0039] ​Specifically, suitable growth pressure and diluted hydrogen flow rate provide a stable gaseous environment for the reaction between the carbon sacrificial layer 30 and the silicon source, ensuring the uniformity of material diffusion and reaction; the high temperature of 1500–1650℃ provides sufficient energy for the recombination of carbon and silicon atoms and the formation of the 3C-SiC structure, promoting the orderly arrangement of atoms to form a stable 3C-SiC lattice; the growth time of 2–5 minutes ensures that the transformation is completed in a short time and avoids defect accumulation caused by overgrowth; and for the case of the sacrificial layer 30 of C material, by supplying more silicon sources and controlling the carbon-silicon ratio at 0.7–0.9, the carbon-silicon atomic ratio can be precisely balanced. The excess carbon in the sacrificial layer 30 is compensated to ensure that carbon and silicon react fully to generate 3C-SiC with a suitable stoichiometric ratio, avoiding structural defects caused by carbon residue. The synergistic effect of these parameters enables the complete transformation of the carbon sacrificial layer 30 into the 3C-SiC buffer layer 40, forming a uniform 3C-SiC buffer layer 40 without impurity residue. This effectively passivates the surface atoms of 4H-SiC, blocks the nucleation path of 4H-SiC, and provides a single and stable phase template for the homogeneous growth of the subsequent 3C-SiC epitaxial layer 50, reducing the risk of polymorphic mixing and ensuring the high-quality growth of the final 3C-SiC epitaxial layer 50.

[0040] When the sacrificial layer 30 is made of Si, the conversion conditions for the 3C-SiC buffer layer 40 in step S30 are as follows: growth pressure of 50–100 mbar, growth temperature of 1300–1400 °C, growth time of 5–10 min, dilution hydrogen of 50–100 slm, carbon source flow rate of 20–100 sccm, and silicon source flow rate of 50–200 sccm. At this time, a silicon sacrificial layer 30 exists on the 4H-SiC substrate 10. Therefore, in the supply of the precursor, more carbon source should be supplied, and the final carbon-to-silicon ratio should be set to 1.1–1.3. Because the melting point of silicon is 1414 °C, the growth temperature in the conversion conditions of the silicon sacrificial layer 30 should be lower than 1400 °C.

[0041] Specifically, appropriate growth pressure and diluted hydrogen flow rate create a stable gaseous atmosphere for the reaction between the silicon sacrificial layer 30 and the carbon source, which is conducive to uniform diffusion and full reaction of the materials. Considering that the melting point of silicon is 1414℃, controlling the growth temperature at 1300-1400℃ provides sufficient energy for the recombination of silicon-carbon atoms and the formation of the 3C-SiC structure, while preventing the silicon sacrificial layer 30 from melting due to excessive temperature, thus ensuring the stable progress of the conversion process. A growth time of 5-10 minutes ensures that the silicon sacrificial layer 30 is fully converted into the 3C-SiC buffer layer 40, while preventing over-reaction and defects. Due to the presence of the silicon sacrificial layer 30... By supplying multiple carbon sources and setting the carbon-silicon ratio to 1.1~1.3, the excess silicon element can be balanced, allowing carbon and silicon to fully react and generate 3C-SiC with a suitable stoichiometric ratio, thus avoiding structural defects caused by silicon residue. These parameters work together to achieve the complete transformation of the silicon sacrificial layer 30 into the 3C-SiC buffer layer 40, forming a uniform 3C-SiC buffer layer 40 without impurity residue. This effectively passivates the surface atoms of 4H-SiC, blocks the nucleation path of 4H-SiC, and provides a single and stable phase template for the homogeneous growth of the subsequent 3C-SiC epitaxial layer 50, reducing the risk of polymorphic mixing and ensuring the high-quality growth of the final 3C-SiC epitaxial layer 50.

[0042] S40, a 3C-SiC epitaxial layer 50 is obtained by homogeneous epitaxial growth on the surface of the 3C-SiC buffer layer 40, such as Figure 2D As shown.

[0043] Specifically, step S40 also includes: The sacrificial layer 30 made of carbon or silicon will generate defects during the conversion to 3C-SiC. Therefore, after the conversion is completed, a third 3C-SiC epitaxial layer 50 needs to be grown to reduce the defects in the final 3C-SiC epitaxial layer 50. The growth conditions of the 3C-SiC epitaxial layer 50 are as follows: growth pressure of 50-200 mbar, growth temperature of 1400-1650℃, growth time of 30-60 min, dilution hydrogen of 50-100 slm, carbon source flow rate of 20-80 sccm, silicon source flow rate of 50-150 sccm, carbon-silicon ratio of carbon source to silicon source of 0.6-0.9, and the thickness of the final 3C-SiC epitaxial layer 50 is 5-12 μm.

[0044] Specifically, this homoepitaxial growth relies on the existing 3C-SiC buffer layer 40 as a stable template. Through continuous silicon-carbon source supply and orderly atomic stacking, potential defects (such as dislocations and stacking faults) in the 3C-SiC buffer layer 40 are "repaired" and covered. The newly grown 3C-SiC epitaxial layer 50 can fill the atomic vacancies in the defect region, guide atoms to align along low-defect paths, and reduce the continuation and expansion of defects. At the same time, the continuity of homoepitaxial growth can avoid the generation of new defects due to phase changes or interface mismatches, further optimizing the crystal integrity of the 3C-SiC epitaxial layer 50. This process can effectively reduce the overall defect density of the final 3C-SiC epitaxial layer 50, improve its key electrical and mechanical properties, solve the potential defect residue problem during the conversion of the sacrificial layer 30, and ensure that the final 3C-SiC epitaxial layer 50 has higher quality and stability, laying a reliable foundation for its application in related devices.

[0045] Accordingly, the present invention also provides a 3C-SiC epitaxial layer, which is prepared by any of the above methods for preparing a 3C-SiC epitaxial layer.

[0046] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0047] Example 1: The method for preparing the 3C-SiC epitaxial layer provided in this embodiment 1 specifically includes the following steps (taking the sacrificial layer 30 made of C material as an example): Step 1: First, place the 4H-SiC substrate 10 into the transfer chamber filled with argon gas. At this time, heat the reaction chamber of the CVD (Chemical Vapor Deposition) equipment at a heating rate of 90 degrees / min. When the reaction chamber reaches the target temperature of 900°C, use the transfer robot to place the 4H-SiC substrate 10 into the reaction chamber. Step 2: Set the growth process conditions in the reaction chamber to homoepitaxially grow a 4H-SiC buffer layer 20 on the surface of the 4H-SiC substrate 10. The growth process conditions for the 4H-SiC buffer layer 20 are as follows: growth pressure of 100 mbar, growth temperature of 1550℃, dilution hydrogen of 80 slm, methane flow rate of 80 sccm, silicon tetrachloride flow rate of 80 sccm, carbon-silicon ratio of the precursor of 1, and growth time of 50 min. The final thickness of the grown 4H-SiC buffer layer 20 is 10 μm. Step 3: After the 4H-SiC buffer layer 20 has grown, immediately change the process parameters of the reaction chamber to grow the carbon sacrificial layer 30. The growth conditions of the sacrificial layer 30 are as follows: growth pressure is 30 mbar, growth temperature is 1500℃, dilution hydrogen is 30 slm, dilution argon is 30 slm, methane flow rate is 30 sccm, and growth time is 50 min. The final thickness of the carbon sacrificial layer 30 is approximately 20 nm.

[0048] Step 4: After the carbon sacrificial layer 30 has grown, immediately change the process parameters of the reaction chamber to completely transform the sacrificial layer 30 into the 3C-SiC buffer layer 40. The transformation conditions of the sacrificial layer 30 are as follows: growth pressure is 100 mbar, growth temperature is 1550℃, dilution hydrogen is 80 slm, methane flow rate is 80 sccm, silicon tetrachloride flow rate is 100 sccm, the carbon-silicon ratio of the precursor needs to be maintained at 0.8, and the growth time is 5 min. The thickness of the final transformed 3C-SiC buffer layer 40 is approximately 20 nm. Step 5: After the carbon sacrificial layer 30 is converted into a 3C-SiC buffer layer 40, a 3C-SiC epitaxial layer 50 is obtained by homoepitaxial growth on the surface of the 3C-SiC buffer layer 40. The growth conditions of the 3C-SiC epitaxial layer 50 are as follows: growth pressure is 100 mbar, growth temperature is 1500℃, dilution hydrogen is 80 slm, methane flow rate is 80 sccm, silicon tetrachloride flow rate is 100 sccm, the carbon-silicon ratio of the precursor needs to be maintained at 0.8, the growth time is 50 min, and the thickness of the finally grown 3C-SiC homoepitaxial layer is 10 μm.

[0049] Please see Figure 3 , Figure 3 This is the Raman spectrum of the sacrificial layer 30 made of C material in the preparation method of the 3C-SiC epitaxial layer 50 provided in Embodiment 1 of the present invention; wherein, Figure 3 The x-axis represents the Raman shift, in cm. -1 The range is from 500 to 3000 cm. -1 , representing the frequency difference between incident and scattered light, reflects changes in molecular vibrational and rotational energy levels; Figure 3 The vertical axis represents intensity, with arbitrary units (au), indicating the strength of the Raman scattering signal. The stronger the signal, the greater the contribution of the corresponding characteristic peak.

[0050] exist Figure 3 In the Raman spectrum, the TO and LO peaks of 4H-SiC reflect information about the 4H-SiC substrate 10, while the D peak (Gr D, approximately 1350 cm⁻¹) associated with the sacrificial layer 30 of the carbon material 10 is... -1This reflects defects and disorder in carbon materials. The G peak (Gr G, approximately 1580 cm⁻¹) is also present. -1 This represents the ordered nature of carbon materials. 2 (structure) and 2D peak (Gr 2D, approximately 2700 cm⁻¹) -1 (Produced by two-phonon resonance, sensitive to carbon layer structure) coexist, combined with the G peak on sp 2 The carbon ordered structure and the D peak reflecting the degree of structural disorder can determine that the carbon sacrificial layer 30 has been successfully grown. At the same time, the 4H-SiC peak also clarifies the structural relationship of the carbon sacrificial layer 30 grown on the silicon carbide substrate, providing a spectroscopic basis for material structure analysis.

[0051] Please see Figure 4 , Figure 4 This is an AFM (Atomic Force Microscopy) image of the sacrificial layer 30 made of C material in the preparation method of the 3C-SiC epitaxial layer 50 provided in Embodiment 1 of the present invention; wherein, Figure 4 The observation area is approximately 1μm × 1μm. The color scale on the right (-11.6nm to 13.0nm) corresponds to the surface height, with warm colors being raised and cool colors being recessed. Figure 4 The structure exhibits obvious wrinkles. Due to stress release during the growth of carbon materials, such typical morphology is easily formed. Combined with the background, the presence of wrinkles proves that the sacrificial layer 30 of carbon material has been successfully grown. Its height difference and continuity can also help to evaluate the quality of the sacrificial layer 30 of carbon material. Combined with Raman spectroscopy, the existence of the sacrificial layer 30 of carbon material is verified from the perspectives of morphology and structure.

[0052] Please see Figure 5 , Figure 5 The XRD pattern of the 3C-SiC epitaxial layer 50 on the 4H-SiC substrate 10 in the preparation method of the 3C-SiC epitaxial layer 50 provided in Embodiment 1 of the present invention is shown. The horizontal axis is the diffraction angle 2θ (in degrees), and the vertical axis is the intensity (in any unit, au). The XRD pattern shows the (111) and (222) crystal plane diffraction peaks of 3C-SiC, indicating that the 3C-SiC phase has been successfully grown on the 4H-SiC substrate 10. By comparing with the diffraction data of 3C-SiC in the standard XRD card (such as the PDF card), it can be determined that these peaks belong to 3C-SiC, and thus the presence of the 3C-SiC crystal structure in the sample is confirmed. Figure 5 The peak intensity of the diffraction peak of the (111) crystal plane is higher, which reflects that the orientation of the crystal plane is prominent and the crystal quality is better.

[0053] Comparative Example 1: Comparative Example 1 provides a method for preparing a 4H-SiC epitaxial layer, specifically including the following steps: Step 1: First, place the 4H-SiC substrate 10 into the transfer chamber filled with argon gas. At this time, heat the reaction chamber of the CVD equipment at a rate of 90 degrees / min. When the reaction chamber reaches the target temperature of 900°C, use the transfer robot to place the 4H-SiC substrate 10 into the reaction chamber. Step 2: Set the growth process conditions in the reaction chamber to homoepitaxially grow a 4H-SiC buffer layer 20 on the surface of the 4H-SiC substrate 10. The growth process conditions for the 4H-SiC buffer layer 20 are as follows: growth pressure of 100 mbar, growth temperature of 1550℃, dilution hydrogen of 80 slm, methane flow rate of 80 sccm, silicon tetrachloride flow rate of 80 sccm, carbon-silicon ratio of the precursor of 1, and growth time of 50 min. The final thickness of the grown 4H-SiC buffer layer 20 is 10 μm. Step 3: After the 4H-SiC buffer layer 20 has grown, without introducing an additional sacrificial layer, immediately change the process parameters of the reaction chamber to grow a 4H-SiC epitaxial layer on the surface of the 4H-SiC buffer layer 20. The above process parameters are consistent with those in Step 5 of Example 1: growth pressure is 100 mbar, growth temperature is 1500℃, dilution hydrogen is 80 slm, methane flow rate is 80 sccm, silicon tetrachloride flow rate is 100 sccm, the carbon-silicon ratio of the precursor needs to be maintained at 0.8, and the growth time is 50 min. Finally, only a 4H-SiC epitaxial layer with a thickness of 10 μm can be obtained.

[0054] Please see Figure 6 , Figure 6 The image shows the Raman spectrum of the 4H-SiC epitaxial layer prepared in Comparative Example 1 without the use of a sacrificial layer made of C or Si material; from Figure 6 The spectrum only shows LO and TO peaks for 4H-SiC, indicating that without the introduction of a sacrificial layer, the chemical vapor deposition process will replicate the crystal information of 4H-SiC, thereby generating a 4H-SiC epitaxial layer, but will not be able to generate a 3C-SiC epitaxial layer.

[0055] This invention proposes a phase control technique assisted by a sacrificial layer 30, which involves growing a high-quality carbon or silicon layer on the 4H-SiC surface as a sacrificial layer 30 to passivate the activity of atomic steps on the 4H-SiC surface, block their nucleation, create a uniform interface for 3C-SiC nucleation, and completely passivate the atoms on the 4H-SiC surface, so that silicon-carbon atom clusters cannot replicate the substrate phase structure and instead generate 3C-SiC with low formation energy, thereby obtaining a high-quality 3C-SiC epitaxial film on the 4H-SiC substrate 10.

[0056] In summary, the present invention provides a 3C-SiC epitaxial layer 50 and its preparation method, comprising the following steps: First, a 4H-SiC substrate 10 is placed in a reaction chamber, and a 4H-SiC buffer layer 20 is homoepitaxially grown on the surface of the 4H-SiC substrate 10; second, a sacrificial layer 30 of C or Si material is heteroepitaxially grown on the surface of the 4H-SiC buffer layer 20; third, the sacrificial layer 30 is completely converted into a 3C-SiC buffer layer 40 by adjusting the process parameters of the reaction chamber; finally, a 3C-SiC epitaxial layer 50 is homoepitaxially grown on the surface of the 3C-SiC buffer layer 40. This invention introduces a sacrificial layer 30 of C or Si material on the surface of a 4H-SiC substrate 10. The sacrificial layer 30 passes through the key role of the atomic steps on the 4H-SiC surface in passivating the nucleation path of silicon-carbon atom clusters replicating the 4H structure of the substrate in existing technologies. This solves the problem of polymorphism caused by the inability to eliminate active sites on the 4H-SiC surface, leading to unavoidable nucleation of 4H-SiC. After the sacrificial layer 30 completely covers and passivates the atoms on the substrate surface, the silicon-carbon atom clusters lose the conditions to replicate the 4H structure and can only preferentially generate 3C-SiC with lower formation energy. This creates a uniform and singular nucleation environment for 3C-SiC, reducing polymorphism at its source. Furthermore, after the sacrificial layer 30 is transformed into a 3C-SiC buffer layer 40, subsequent homoepitaxial growth can continue based on the stable 3C structure, ensuring the consistency of the phases during epitaxy and further reducing the probability of structural defects. This improves the purity and crystal quality of the 3C-SiC epitaxial layer 50, ultimately overcoming the core defect of polymorphism and effectively improving the yield compared to existing technologies.

[0057] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0058] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a 3C-SiC epitaxial layer, characterized in that, Includes the following steps: S10, a 4H-SiC substrate is placed in the reaction chamber, and a 4H-SiC buffer layer is homoepitaxially grown on the surface of the 4H-SiC substrate; S20, a sacrificial layer of C or Si material is obtained by heteroepitaxial growth on the surface of the 4H-SiC buffer layer; S30, by adjusting the process parameters of the reaction chamber, the sacrificial layer is completely converted into a 3C-SiC buffer layer; S40, a 3C-SiC epitaxial layer is obtained by homogeneous epitaxial growth on the surface of the 3C-SiC buffer layer.

2. The method for preparing the 3C-SiC epitaxial layer according to claim 1, characterized in that, The growth conditions of the 4H-SiC buffer layer in step S10 are as follows: growth pressure of 50-200 mbar, growth temperature of 1500-1650℃, growth time of 30-60 min, dilution hydrogen of 50-100 slm, carbon source flow rate of 20-100 sccm, silicon source flow rate of 50-200 sccm, and the carbon-silicon ratio of the carbon source to the silicon source of 0.8-1.

2.

3. The method for preparing the 3C-SiC epitaxial layer according to claim 1, characterized in that, When the material of the sacrificial layer is C, the growth conditions of the sacrificial layer in step S20 are as follows: growth pressure of 20-50 mbar, growth temperature of 1400-1600℃, growth time of 30-60 min, dilution hydrogen of 20-50 slm, dilution argon of 20-40 slm, and carbon source flow rate of 10-40 sccm.

4. The method for preparing the 3C-SiC epitaxial layer according to claim 3, characterized in that, The conversion conditions for the 3C-SiC buffer layer in step S30 are as follows: growth pressure of 50-200 mbar, growth temperature of 1500-1650℃, growth time of 2-5 min, dilution hydrogen of 50-100 slm, carbon source flow rate of 20-100 sccm, silicon source flow rate of 50-200 sccm, and the carbon-silicon ratio of the carbon source to the silicon source of 0.7-0.

9.

5. The method for preparing a 3C-SiC epitaxial layer according to claim 1, characterized in that, When the sacrificial layer is made of Si, the growth conditions of the sacrificial layer in step S20 are as follows: growth pressure of 50-100 mbar, growth temperature of 1000-1200℃, growth time of 30-60 min, dilution hydrogen of 50-100 slm, and silicon source flow rate of 10-30 sccm.

6. The method for preparing a 3C-SiC epitaxial layer according to claim 5, characterized in that, The conversion conditions for the 3C-SiC buffer layer in step S30 are as follows: growth pressure of 50-100 mbar, growth temperature of 1300-1400℃, growth time of 5-10 min, dilution hydrogen of 50-100 slm, carbon source flow rate of 20-100 sccm, silicon source flow rate of 50-200 sccm, and the carbon-silicon ratio of the carbon source to the silicon source of 1.1-1.

3.

7. The method for preparing a 3C-SiC epitaxial layer according to claim 1, characterized in that, The growth conditions of the 3C-SiC epitaxial layer in step S40 are as follows: growth pressure of 50-200 mbar, growth temperature of 1400-1650℃, growth time of 30-60 min, dilution hydrogen of 50-100 slm, carbon source flow rate of 20-80 sccm, silicon source flow rate of 50-150 sccm, and the carbon-silicon ratio of the carbon source to the silicon source of 0.6-0.

9.

8. The method for preparing a 3C-SiC epitaxial layer according to any one of claims 2 to 7, characterized in that, The carbon source includes any one of methane, ethane, propane, and ethylene, and the silicon source includes any one of silicon tetrachloride, trichlorosilane, dichlorosilane, and silane.

9. The method for preparing a 3C-SiC epitaxial layer according to claim 1, characterized in that, The thickness of the 4H-SiC buffer layer is 6–12 μm; when the material of the sacrificial layer is C, the thickness of the sacrificial layer is 10–30 nm; when the material of the sacrificial layer is Si, the thickness of the sacrificial layer is 0.2–0.5 μm; and the thickness of the 3C-SiC epitaxial layer is 5–12 μm.

10. A 3C-SiC epitaxial layer, characterized in that, It is prepared by the method for preparing the 3C-SiC epitaxial layer as described in any one of claims 1 to 9.

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