3c-sic epitaxial layer and method for producing the same

Abstract

The application provides a 3C-SiC epitaxial layer and a preparation method thereof, and the preparation method comprises the following steps: firstly, placing a 4H-SiC substrate in a reaction chamber, and growing a 4H-SiC buffer layer on the surface of the 4H-SiC substrate by homoepitaxy; secondly, growing a sacrificial layer made of C or Si on the surface of the 4H-SiC buffer layer by heteroepitaxy; thirdly, completely converting the sacrificial layer into a 3C-SiC buffer layer by adjusting the process parameters of the reaction chamber; and finally, growing a 3C-SiC epitaxial layer on the surface of the 3C-SiC buffer layer by homoepitaxy. The application introduces a sacrificial layer made of C or Si on the surface of the 4H-SiC substrate, and utilizes the key role of the sacrificial layer in passivating the atomic step activity of the 4H-SiC surface, so that the polymorphic hybridization phenomenon is reduced from the root, and the growth quality and yield of the 3C-SiC epitaxial layer are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, and in particular to a 3C-SiC epitaxial layer and its preparation method. Background Technology

[0002] The core advantages of 3C-SiC (cubic silicon carbide) over 4H-SiC (hexagonal silicon carbide) lie in its physical properties and application potential. In terms of electron mobility, 3C-SiC exhibits significantly higher carrier mobility (its electron mobility can reach approximately 1000 cm⁻¹). 2 / V·s, superior to 950cm⁻¹ of 4H-SiC. 2 With a bandgap of approximately 2.3 eV, 3C-SiC is particularly suitable for low- to medium-voltage, high-frequency power devices, reducing on-resistance and switching losses. Regarding bandgap characteristics, 3C-SiC's smaller bandgap facilitates the development of devices with lower threshold voltages. Its isotropic nature ensures uniform electrical performance across any crystal orientation, simplifying device design and process integration. In particular, regarding heteroepitaxial compatibility, 3C-SiC can be grown directly on silicon substrates (at a growth temperature of approximately 1300°C), significantly reducing costs and driving the development of "3C-SiC-on-Si" technology, providing cost-effective solutions for consumer electronics and the Internet of Things (IoT).

[0003] However, "3C-SiC-on-Si" generates significant internal stress and defect density, greatly reducing device reliability and making it unsuitable for automotive-grade applications. 4H-SiC, however, has almost identical coefficients of thermal expansion and lattice coefficients to 3C-SiC, allowing for the growth of perfect 3C-SiC on 4H-SiC substrates. Current epitaxial growth of 3C-SiC on 4H-SiC substrates relies on a "step control" mechanism: annealing or surface treatment techniques are used to extend the mesa length of the atomic steps on the 4H-SiC surface, enabling silicon-carbon atom clusters to nucleate on the mesa during growth. Silicon-carbon atoms nucleated on the mesa are more likely to form the 3C-SiC phase. However, this method cannot completely prevent 4H-SiC nucleation, resulting in low yields of hybridized products.

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

[0005] The purpose of this invention is to provide a 3C-SiC epitaxial layer and its preparation method, so as to overcome the technical problem of low growth quality of existing 3C-SiC epitaxial layers.

[0006] To address the aforementioned technical problems, this invention first provides a method for preparing a 3C-SiC epitaxial layer, comprising 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 a 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 a 3C-SiC buffer layer.

[0007] In particular, because semiconductor processes are extremely sensitive to additional impurity elements, only C or Si layers can be used as sacrificial layers. Using other elements would greatly degrade the physical properties of silicon carbide.

[0008] Preferably, 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 carbon-silicon ratio of carbon source to silicon source of 0.8-1.2.

[0009] Preferably, 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.

[0010] Preferably, the conversion conditions of 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 carbon-silicon ratio of carbon source to silicon source of 0.7-0.9.

[0011] Preferably, 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.

[0012] Preferably, the conversion conditions of 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 carbon-silicon ratio of carbon source to silicon source of 1.1-1.3.

[0013] Preferably, 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 carbon-silicon ratio of carbon source to silicon source of 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; when the sacrificial layer is made of C, the thickness of the sacrificial layer is 10–30 nm; when the sacrificial layer is made of 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.

[0016] 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.

[0017] The beneficial effects of this invention are as follows: Unlike the prior art, this invention provides a 3C-SiC epitaxial layer and its preparation method, comprising the following steps: First, a 4H-SiC substrate is placed in a reaction chamber, and a 4H-SiC buffer layer is homoepitaxially grown on the surface of the 4H-SiC substrate; second, a sacrificial layer of C or Si material is heteroepitaxially grown on the surface of the 4H-SiC buffer layer; third, the sacrificial layer is completely converted into a 3C-SiC buffer layer by adjusting the process parameters of the reaction chamber; finally, a 3C-SiC epitaxial layer is homoepitaxially grown on the surface of the 3C-SiC buffer layer. This invention introduces a sacrificial layer of C or Si material onto the surface of a 4H-SiC substrate. Utilizing the key role of the sacrificial layer in passivating the activity of atomic steps on the 4H-SiC surface, it directly blocks 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 completely covers and passivates the substrate surface atoms, 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, fundamentally reducing polymorphism. Furthermore, after the sacrificial layer is transformed into a 3C-SiC buffer layer, subsequent homoepitaxial growth can continue based on the stable 3C structure, ensuring phase consistency during epitaxy and further reducing the probability of structural defects. This improves the purity and crystal quality of the 3C-SiC epitaxial layer, ultimately overcoming the core defect of polymorphism and effectively improving the yield compared to existing technologies. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the method for preparing a 3C-SiC epitaxial layer according to an embodiment of the present invention. Figures 2A-2D This is a schematic diagram of the structure of each step in the method for preparing the 3C-SiC epitaxial layer provided in the embodiments of the present invention; Figure 3 The Raman spectrum of the sacrificial layer of material C in the preparation method of 3C-SiC epitaxial layer provided in Embodiment 1 of the present invention; Figure 4 The image shows the AFM of the sacrificial layer made of C material in the method for preparing the 3C-SiC epitaxial layer provided in Embodiment 1 of the present invention. Figure 5 The XRD pattern of the 3C-SiC epitaxial layer on the 4H-SiC substrate in the preparation method of the 3C-SiC epitaxial layer provided in Embodiment 1 of the present invention; Figure 6 The Raman spectrum of the 4H-SiC epitaxial layer prepared without the use of C or Si material in Comparative Example 1 is shown. 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 to 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 for the 4H-SiC buffer layer 20 were set as follows: growth pressure of 50–200 mbar, growth temperature of 1500–1650 °C, 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, carbon-silicon ratio of carbon source to silicon source of 0.8–1.2, and the final thickness of the grown 4H-SiC buffer layer 20 was 6–12 μm.

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

[0026] Furthermore, appropriate growth pressure and diluted hydrogen flow rate can optimize the stability of the gas atmosphere in the reaction chamber, avoiding uneven growth caused by airflow turbulence; the high temperature of 1500–1650℃ can provide sufficient energy for the decomposition and migration of silicon and carbon sources, promoting the orderly arrangement of atoms on the substrate surface; a carbon-to-silicon ratio of 0.8–1.2 can balance the supply ratio of silicon and carbon atoms, reducing defects (such as vacancies and interstitial atoms) caused by compositional deviation; a growth time of 30–60 min and a thickness design of 6–12 μm can ensure that the 4H-SiC buffer layer 20 fully covers the surface of the 4H-SiC substrate 10 and fills potential micro-defects, while avoiding stress accumulation problems caused by excessively thick growth; the synergistic effect of these parameters can ensure that the 4H-SiC buffer layer 20 has uniform thickness, low defect density and good crystal quality, providing a flat and stable substrate for the subsequent growth of the sacrificial layer, thereby creating reliable early conditions for the sacrificial layer to passivate the substrate surface activity and block 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, and the silicon source can be silicon tetrachloride, trichlorosilane, dichlorosilane, or silane.

[0028] S20, a sacrificial layer 30 of C or Si material is heteroepitaxially grown on the surface of the 4H-SiC buffer layer 20, such as Figure 2B As shown.

[0029] Specifically, step S20 also includes: After the 4H-SiC homoepitaxial layer is grown, the process parameters are immediately changed to grow a carbon or silicon sacrificial layer 30. The growth conditions for carbon and silicon sacrificial layers 30 are different and need to be described separately. It is particularly important to emphasize that the sacrificial layer 30 can only be made of carbon or silicon. If a sacrificial layer 30 of other elements is used, a large number of impurity elements will be introduced into the 3C-SiC, degrading 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, passivating the activity of the atomic steps on the 4H-SiC surface through its material properties—these active sites are the root cause of 4H-SiC nucleation that is difficult to avoid in the existing technology, while the sacrificial layer 30 can block the path of silicon-carbon atom clusters directly replicating the 4H structure of the substrate, eliminating the "foundation" of 4H-SiC nucleation from the source; on the other hand, On the one 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. Moreover, since it contains only carbon or silicon, it will not introduce impurities when it is subsequently converted into a 3C-SiC buffer layer, thus avoiding the performance degradation problem caused by other element sacrificial layers 30. At the same time, this uniform covering can also ensure the consistency of the phases during the subsequent homoepitaxial growth of 3C-SiC, reduce polymorphic mixing, and ultimately lay a decisive foundation for the preparation of a 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: 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; the thickness of the finally grown carbon material sacrificial layer 30 is about 10-30 nm.

[0032] Specifically, appropriate growth pressure and hydrogen-argon mixed dilution gas flow rate can optimize the diffusion and distribution of 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 carbon source decomposition and dense carbon layer growth, promoting the orderly arrangement of carbon atoms to form a continuously covering carbon sacrificial layer 30; the synergistic effect of a growth time of 30–60 min and a carbon source flow rate of 10–40 sccm precisely controls the thickness of 10–30 nm—a thickness that can fully cover the surface of the carbon source. The 4H-SiC buffer layer 20 is covered with a layer that completely passivates the activity of atomic steps, effectively blocking the nucleation path of 4H-SiC, and avoids stress problems during the subsequent conversion to a 3C-SiC buffer layer due to excessive thickness. At the same time, the carbon sacrificial layer 30 is kept pure by introducing only carbon source without the introduction of other impurity elements, creating an impurity-free interface for the subsequent conversion to a 3C-SiC buffer layer. Ultimately, this provides a uniform environment for 3C-SiC nucleation, reduces polymorphism mixing, and lays a reliable foundation for the growth of a high-quality 3C-SiC epitaxial layer 50.

[0033] When the sacrificial layer 30 is made of Si, the growth conditions for the sacrificial layer 30 in step S20 are as follows: growth pressure of 50–100 mbar, growth temperature of 1000–1200 °C, growth time of 30–60 min, dilution hydrogen of 50–100 slm, and silicon source flow rate of 10–30 sccm; the final thickness of the Si sacrificial layer 30 is approximately 0.2–0.5 μm. It should be noted that the Si sacrificial layer 30 should not be too thick, otherwise it will not be completely converted into silicon carbide.

[0034] Specifically, suitable growth pressure and diluted hydrogen flow rate optimize the diffusion and distribution of the silicon source within the reaction chamber, ensuring uniform deposition of silicon atoms on the surface of the 4H-SiC buffer layer 20. A temperature of 1000–1200℃ provides appropriate energy for silicon source decomposition and stable silicon layer growth, promoting the orderly arrangement of silicon atoms to form a continuously covering sacrificial silicon layer 30. A growth time of 30–60 min and a silicon source flow rate of 10–30 sccm work synergistically to precisely control a thickness of 0.2–0.5 μm—a thickness sufficient to fully cover the 4H-SiC buffer layer. The surface of the SiC buffer layer 20 effectively passivates the activity of atomic steps, blocking the nucleation path of 4H-SiC. Because it is limited to this range, it avoids being too thick, ensuring 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 and no other impurity elements are introduced, ensuring the purity of the silicon sacrificial layer 30. This creates an impurity-free interface for the subsequent conversion into the 3C-SiC buffer layer, ultimately providing a uniform environment for 3C-SiC nucleation, reducing polymorphism mixing, and laying 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, the sacrificial layer 30 is completely converted into the 3C-SiC buffer layer 40.

[0036] Specifically, step S30 also includes: After the growth of the carbon or silicon sacrificial layer 30 is completed, the process parameters are immediately changed to transform the sacrificial layer 30 into a 3C-SiC buffer layer 40. The transformation conditions are slightly different and need to be explained separately. The 3C-SiC buffer layer 40 can passivate the surface atoms of 4H-SiC, preventing subsequent silicon-carbon atom clusters from replicating the atomic template of the 4H-SiC substrate 10, thus only generating 3C-SiC with lower formation energy, such as... Figure 2C As shown.

[0037] Specifically, the core purpose of completely transforming the sacrificial layer 30 into the 3C-SiC buffer layer 40 is to achieve interface control and phase guidance through phase transformation, laying the foundation for the homogeneous growth of the subsequent 3C-SiC epitaxial layer 50. On the one hand, the transformation process can convert the material form of the carbon or silicon sacrificial layer 30 into a 3C-SiC structure. The 3C-SiC buffer layer 40 is used to further passivate the atomic activity on the surface of the 4H-SiC substrate 10. Compared with the original sacrificial layer 30 (C or Si), the 3C-SiC buffer layer 40, as having the same phase structure as the target 3C-SiC epitaxial layer 50, can be more stable. By specifically blocking the nucleation path of 4H-SiC, the silicon-carbon atom clusters are prevented from replicating the 4H structure of the substrate, forcing it to preferentially 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, forming a continuous 3C-SiC structure transition. This ensures that there is no unconverted sacrificial layer 30 residue at the interface (if there is residue, it may lead to impurities or structural defects). This provides a uniform and single phase template for the homogeneous epitaxial growth of the subsequent 3C-SiC epitaxial layer 50, reduces the risk of polymorphism, and ultimately ensures the high-quality growth of the 3C-SiC epitaxial layer 50.

[0038] When the sacrificial layer 30 is made of C, the conversion conditions of the 3C-SiC buffer layer 40 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, and silicon source flow rate of 50-200 sccm. At this time, there is a carbon sacrificial layer 30 on the 4H-SiC substrate 10. Therefore, in the supply of the precursor, more silicon source should be supplied, and the final 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, while the D peak (Gr D, approximately 1350 cm⁻¹) associated with the sacrificial layer 30 of the carbon material is shown. -1This reflects defects and disorder in carbon materials, and 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 activity of these steps, directly blocking 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 substrate surface atoms, 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, fundamentally reducing polymorphism. 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; When the material of the sacrificial layer is C, the growth conditions of the sacrificial layer in step S20 are as follows: growth pressure is 20-50 mbar, growth temperature is 1400-1600℃, growth time is 30-60 min, dilution hydrogen is 20-50 slm, dilution argon is 20-40 slm, and carbon source flow rate is 10-40 sccm. When the material of the sacrificial layer is Si, the growth conditions of the sacrificial layer in step S20 are as follows: growth pressure is 50-100 mbar, growth temperature is 1000-1200℃, growth time is 30-60 min, dilution hydrogen is 50-100 slm, and silicon source flow rate is 10-30 sccm. 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.

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, 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.

4. The method for preparing a 3C-SiC epitaxial layer according to claim 1, 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.

5. 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.

6. 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.

7. 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 6.

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