Method for improving quality of silicon carbide epitaxial layer
The carrot-like defects in the silicon carbide epitaxial layer were removed by chemical mechanical polishing (CMP) thinning treatment, which solved the problem of difficulty in completely removing defects in the existing technology and achieved the effect of uniform thickness and zero defects in high-quality epitaxial layers.
Patent Information
- Application Number
- CN202511798647.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-02-24
AI Technical Summary
Existing technologies cannot completely remove the carrot defect in the silicon carbide epitaxy process, which affects device performance and reliability.
Chemical mechanical polishing was performed on the surface of the epitaxial layer to remove carrot defects. The polishing solution temperature was 40~44℃, the flow rate was 120~150mL/min, the polishing head pressure was 8~12psi, and the thinning amount was 0.2~100μm.
The epitaxial product with zero carrot defects was achieved, ensuring the thickness uniformity and quality of the epitaxial layer and meeting the requirements of high-performance power electronic devices.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor material epitaxial growth and processing technology, and particularly relates to a method for improving the quality of silicon carbide epitaxial layers. Background Technology
[0002] SiC epitaxy involves growing a single-crystal thin film with a specific crystal orientation on a SiC substrate. This epitaxial layer is fundamental for manufacturing high-performance power electronic devices such as Schottky diodes, MOSFETs, and IGBTs. Its quality directly affects the performance and reliability of the devices, thus imposing stringent requirements on growth techniques and process control. Consequently, various defects inevitably occur during SiC epitaxy, posing challenges to the performance and reliability of SiC power devices.
[0003] Although the quality of 6 / 8-inch silicon carbide substrates is currently very high, carrot defects are always generated during epitaxy due to partial dislocations in the substrate. Existing technologies usually use hydrogen to etch the substrate surface before epitaxy to repair the sub-damaged layer. Although this can reduce defects in epitaxy, it is difficult to completely control them to a very low level, and a small number of carrot defects will still exist. Summary of the Invention
[0004] The purpose of this invention is to provide a method for improving the quality of silicon carbide epitaxial layers, which can produce epitaxial products with zero carrot defects.
[0005] A method for improving the quality of silicon carbide epitaxial layers includes the following steps:
[0006] A) Growing a buffer layer and an epitaxial layer on the surface of a silicon carbide substrate;
[0007] B) Thin the outer surface of the epitaxial layer by chemical mechanical polishing to remove carrot defects;
[0008] The thinning amount of the chemical mechanical polishing is 0.2~100μm, the pressure of the polishing head is 8~12psi, the temperature of the polishing slurry is 40~44℃, and the flow rate of the polishing slurry is 120~150mL / min.
[0009] Preferably, during the growth of the buffer layer, carbon source gas, silicon source gas and hydrogen are introduced, with the hydrogen flow rate in the central path being 50~200 SLM, the hydrogen flow rate in the bypass path being 30~100 SLM, the growth temperature being 1580~1650℃, the C / Si ratio being 0.5~0.9, and the growth rate being 6~10 μm / h.
[0010] Preferably, the carrier concentration of the buffer layer is ≥1E18, and the thickness of the buffer layer is 0.5~2μm.
[0011] Preferably, during the growth of the epitaxial layer, carbon source gas, silicon source gas, and hydrogen are introduced, with a central hydrogen flow rate of 50~200 SLM, a bypass hydrogen flow rate of 30~100 SLM, a C / Si ratio of 0.85~1.2, a growth temperature of 1580~1650℃, and a growth rate of 50~70 μm / h.
[0012] Preferably, the carrier concentration of the epitaxial layer is ≤1E17 and the thickness is ≥5μm.
[0013] Preferably, the carbon source gas includes C2H2 or C3H8; the silicon source gas includes SiHCl3 or SiH4.
[0014] Preferably, the polishing head of the chemical mechanical polishing process rotates at 100-120 rpm, and the polishing disc rotates at 80-100 rpm.
[0015] Preferably, the thinning amount of the chemical mechanical polishing is 0.5~50μm.
[0016] Preferably, the thinning amount of the chemical mechanical polishing is 1~2 μm.
[0017] Preferably, the polishing solution comprises 15-30% alumina and 3-20% sodium permanganate by mass.
[0018] This invention provides a method for improving the quality of silicon carbide epitaxial layers, comprising the following steps: A) growing a buffer layer and an epitaxial layer on the surface of a silicon carbide substrate; B) performing chemical mechanical polishing (CMP) to thin the outer surface of the epitaxial layer to remove carrot defects; the thinning amount of CMP is 0.2~100μm, the pressure of the polishing head is 8~12psi, the temperature of the polishing solution is 40~44℃, and the flow rate of the polishing solution is 120~150mL / min. This invention, by performing CMP thinning treatment on the epitaxial surface after epitaxy, can obtain an epitaxial product with zero carrot defects, and is not limited by the number of epitaxial layers. Only the outermost layer needs to be thinned by CMP to obtain an epitaxial surface with zero carrot defects. Furthermore, this application improves the CMP process to ensure the uniformity of the epitaxial layer thickness while removing carrot defects. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0020] Figure 1This is a schematic diagram of the silicon carbide epitaxial layer growth process of the present invention. Figure 1 In the diagram, 1 is the induction coil, 2 is the temperature field material, 3 is the mixed process gas, and 4 is the silicon carbide substrate.
[0021] Figure 2 This is a flowchart of the method for improving the quality of silicon carbide epitaxial layers according to the present invention;
[0022] Figure 3 This is a schematic diagram of the structure of the silicon carbide epitaxial product in this invention. A is the silicon carbide substrate, B is the buffer layer, C is the epitaxial layer, and D is the thinning layer.
[0023] Figure 4 This is a schematic diagram of carrot defects before (left) and after (right) thinning of the epitaxial product in Embodiment 1 of the present invention. Detailed Implementation
[0024] This invention provides a method for improving the quality of silicon carbide epitaxial layers, comprising the following steps:
[0025] A) Growing a buffer layer and an epitaxial layer on the surface of a silicon carbide substrate;
[0026] B) Thin the outer surface of the epitaxial layer by chemical mechanical polishing to remove carrot defects;
[0027] The thinning amount of the chemical mechanical polishing is 0.2~100μm, the pressure of the polishing head is 8~12psi, the temperature of the polishing fluid is 40~44℃, and the flow rate of the polishing fluid is 120~130mL / min.
[0028] In this invention, the production process of the buffer layer and the epitaxial layer is as follows: Figure 1 As shown.
[0029] This invention places a silicon carbide substrate in a reaction chamber, introduces process gases, and sequentially grows a buffer layer and an epitaxial layer. The process gases preferably include a carbon source gas, a silicon source gas, and hydrogen. The carbon source gas preferably includes C2H2 or C3H8; the silicon source gas includes SiHCl3 or SiH4. The carbon source gas and silicon source gas used during the growth of the buffer layer can be the same or different.
[0030] In this invention, during the growth of the buffer layer, the central hydrogen flow rate is preferably 50-200 SLM, more preferably 100-150 SLM, such as 50 SLM, 80 SLM, 100 SLM, 120 SLM, 150 SLM, 180 SLM, 200 SLM, and preferably a range of values with any of the above values as the upper or lower limit; the bypass hydrogen flow rate is preferably 30-100 SLM, more preferably 50-80 SLM, such as 30 SLM, 40 SLM, 50 SLM, 60 SLM, 70 SLM, 80 SLM, 90 SLM, 10 ... The SLM is preferably a range of values with any of the above values as the upper or lower limit; the C / Si ratio is preferably 0.5~0.9, such as 0.5, 0.6, 0.7, 0.8, 0.9, preferably a range of values with any of the above values as the upper or lower limit; the growth temperature of the buffer layer is preferably 1580~1650℃, more preferably 1600~1620℃; and the growth rate of the buffer layer is preferably 6~10μm / h, more preferably 7~8μm / h.
[0031] In this invention, the carrier concentration of the buffer layer is ≥1E18, and the thickness of the buffer layer is 0.5~2μm, more preferably 1~1.5μm.
[0032] In this invention, during the epitaxial layer growth process, the central hydrogen flow rate is preferably 50-200 SLM, more preferably 100-150 SLM, such as 50 SLM, 80 SLM, 100 SLM, 120 SLM, 150 SLM, 180 SLM, 200 SLM, and preferably a range of values with any of the above values as the upper or lower limit; the bypass hydrogen flow rate is preferably 30-100 SLM, more preferably 50-80 SLM, such as 30 SLM, 40 SLM, 50 SLM, 60 SLM, 70 SLM, 80 SLM, 90 SLM, 10 ... The SLM is preferably a range of values with any of the above values as the upper or lower limit; the C / Si ratio is preferably 0.85~1.2, such as 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, preferably a range of values with any of the above values as the upper or lower limit; the growth temperature is preferably 1580~1650℃, more preferably 1600~1620℃, and the growth rate of the buffer layer is preferably 50~70μm / h, more preferably 55~60μm / h.
[0033] In this invention, the carrier concentration of the epitaxial layer is ≤1E17 and the thickness is ≥5μm. The epitaxial layer can be grown in multiple layers to prepare silicon carbide epitaxial products with a voltage >650V.
[0034] After obtaining the silicon carbide epitaxial product, the grown epitaxial product is subjected to infrared spectroscopy testing, followed by apparent defect testing to determine the type and distribution of defects. Then, the epitaxial layer surface is thinned by chemical mechanical polishing to remove carrot defects.
[0035] In this invention, the thinning amount achieved by chemical mechanical polishing is preferably 0.2~100 μm, more preferably 0.5~50 μm, such as 0.2 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc. μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, preferably values within the range of any of the above values as the upper or lower limit; the pressure of the polishing head for chemical mechanical polishing is preferably 8~12psi, more preferably 10~11 psi. The preferred rotational speed of the polishing head for the chemical mechanical polishing is 100-120 rpm, more preferably 110-115 rpm, such as 100 rpm, 105 rpm, 110 rpm, 115 rpm, 120 rpm, preferably within the range of any of the above values as the upper or lower limit; the preferred rotational speed of the polishing disc for the chemical mechanical polishing is 80-100 rpm, more preferably 90-95 rpm, such as 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, preferably within the range of any of the above values as the upper or lower limit.
[0036] In this invention, the polishing slurry used for chemical mechanical polishing preferably comprises alumina and permanganate. The mass fraction of the alumina is preferably 15-30%, more preferably 20-25%, such as 15%, 20%, 25%, 30%, preferably within the range of any of the above values as the upper or lower limit. The permanganate is preferably potassium permanganate or sodium permanganate, and the mass fraction of the permanganate is preferably 3-20%, more preferably 5-15%, such as 3%, 5%, 10%, 15%, 20%, preferably within the range of any of the above values as the upper or lower limit. The temperature of the polishing slurry is preferably 40-44°C, more preferably 42-43°C. The flow rate of the polishing slurry is preferably 120-150 mL / min, more preferably 140-150 mL / min, such as 120 mL / min, 125 mL / min, 130 mL / min, 135 mL / min, 140 mL / min, 145 mL / min, 150 mL / min, preferably within the range of any of the above values as the upper or lower limit.
[0037] After thinning is completed, surface cleaning is performed to remove dirt and grime from the product's surface.
[0038] This invention provides a method for improving the quality of silicon carbide epitaxial layers, comprising the following steps: A) growing a buffer layer and an epitaxial layer on the surface of a silicon carbide substrate; B) performing chemical mechanical polishing (CMP) to thin the outer surface of the epitaxial layer to remove carrot defects; the thinning amount of CMP is 0.2~100μm, the pressure of the polishing head is 8~12psi, the temperature of the polishing solution is 40~44℃, and the flow rate of the polishing solution is 120~150mL / min. This invention, by performing CMP thinning treatment on the epitaxial surface after epitaxy, can obtain an epitaxial product with zero carrot defects, and is not limited by the number of epitaxial layers. Only the outermost layer needs to be thinned by CMP to obtain an epitaxial surface with zero carrot defects. Furthermore, this application improves the CMP process to ensure the uniformity of the epitaxial layer thickness while removing carrot defects.
[0039] To further illustrate the present invention, the following describes in detail a method for improving the quality of silicon carbide epitaxial layers provided by the present invention with reference to embodiments, but it should not be construed as limiting the scope of protection of the present invention.
[0040] Example 1
[0041] Place the silicon carbide substrate in such a position Figure 1 In the reaction chamber shown, a mixture of C2H2 + TCS gas + H2 gas was introduced. With a hydrogen flow rate of 120 SLM in the central path and 70 SLM in the bypass path, and a process temperature of 1610℃ and a C / Si ratio of 0.8, a buffer layer with a thickness of 1 μm and a carrier concentration ≥1E18 was grown.
[0042] Then, under the conditions of a central hydrogen flow rate of 120 SLM, a bypass hydrogen flow rate of 70 SLM, a process temperature of 1610℃, and a C / Si ratio of 1.0, an epitaxial layer with a thickness of 10.5 μm and a carrier concentration ≤1E17 was grown.
[0043] The grown epitaxial product undergoes infrared spectroscopy testing, followed by appearance defect testing, to ultimately determine the type and distribution of defects, such as... Figure 4 As shown in the left figure.
[0044] The surface of the epitaxial layer was thinned by chemical mechanical polishing. The polishing slurry consisted of 20% alumina and 15% sodium permanganate. The polishing head rotated at 115 rpm, the polishing disc rotated at 95 rpm, the pressure of the polishing head was 10 psi, the flow rate of the polishing slurry was 145 ml / min, the temperature of the polishing slurry was 42℃, and the thinning amount was 1 μm.
[0045] The thinned epitaxial product underwent infrared spectroscopy testing, followed by appearance defect testing. The results are as follows: Figure 4 As shown in the right figure.
[0046] Comparative Example 1
[0047] The epitaxial layer was prepared according to the method in Example 1, except that the chemical mechanical polishing was performed with the following parameters:
[0048] The surface of the epitaxial layer was thinned by chemical mechanical polishing. The polishing slurry consisted of 15% alumina and 8% sodium permanganate. The polishing head rotated at 105 rpm, the polishing disc rotated at 80 rpm, the pressure of the polishing head was 16 psi, the flow rate of the polishing slurry was 130 ml / min, the temperature of the polishing slurry was 22℃, and the thinning amount was 1 μm.
[0049] Three samples were taken according to the methods in Example 1 and Comparative Example 1, and performance tests were conducted. The results are shown in Table 1.
[0050] Table 1 Performance parameters of the epitaxial products in Example 1 and Comparative Example 1
[0051]
[0052] As shown in Table 1, in Embodiment 1 of the present invention, zero carrot defects on the surface of the epitaxial layer were achieved by chemical mechanical polishing. Furthermore, the uniformity of the epitaxial layer after thinning was ensured by improving the chemical mechanical polishing process. In contrast, the chemical mechanical polishing process in Comparative Example 1 resulted in an epitaxial layer thickness non-uniformity that was 3 to 5 times greater than before, failing to meet the requirements of the epitaxial product.
[0053] Example 2
[0054] Place the silicon carbide substrate in such a position Figure 1 In the reaction chamber shown, a mixture of C2H2 + TCS gas + H2 gas was introduced. With a hydrogen flow rate of 120 SLM in the central path and 70 SLM in the bypass path, and a process temperature of 1610℃ and a C / Si ratio of 0.8, a buffer layer with a thickness of 1 μm and a carrier concentration ≥1E18 was grown.
[0055] Then, under the conditions of a central hydrogen flow rate of 120 SLM, a bypass hydrogen flow rate of 70 SLM, a process temperature of 1610℃, and a C / Si ratio of 1.0, an epitaxial layer with a thickness of 10.5 μm and a carrier concentration ≤1E17 was grown.
[0056] The grown epitaxial products are subjected to infrared spectroscopy testing, followed by appearance defect testing, to ultimately determine the types and distribution of defects.
[0057] The surface of the epitaxial layer was thinned by chemical mechanical polishing. The polishing slurry consisted of 20% alumina and 15% sodium permanganate. The polishing head rotated at 115 rpm, the polishing disc rotated at 95 rpm, the pressure of the polishing head was 10 psi, the flow rate of the polishing slurry was 145 ml / min, the temperature of the polishing slurry was 42℃, and the thinning amount was 1 μm.
[0058] The thinned epitaxial product is subjected to infrared spectroscopy testing, followed by appearance defect testing.
[0059] Example 3
[0060] The epitaxial layer was prepared according to the method in Example 2, except that the thinning amount in Example 3 was 0.5 μm.
[0061] Example 4
[0062] The epitaxial layer was prepared according to the method in Example 2, except that the thinning amount in Example 4 was 2 μm.
[0063] Three samples were taken from each of the samples according to the methods in Examples 2 to 4, and the performance was tested. The results are shown in Table 2.
[0064] Table 2 Performance data of epitaxial products in Examples 2-4
[0065]
[0066] As shown in Table 2, after removing ≥1μm of material, the carrot defects were completely removed, and the thickness non-uniformity remained within a stable range, meeting the requirements for epitaxial products.
[0067] In summary, the method of this invention not only maintains the epitaxial thickness non-uniformity at a level comparable to that before thinning, but also achieves zero carrot defects, resulting in high-quality epitaxial products.
[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for improving the quality of a silicon carbide epitaxial layer, comprising the following steps: A) Growing a buffer layer and an epitaxial layer on the surface of a silicon carbide substrate; B) Thin the outer surface of the epitaxial layer by chemical mechanical polishing to remove carrot defects; The thinning amount of the chemical mechanical polishing is 0.2~100μm, the pressure of the polishing head is 8~12psi, the temperature of the polishing slurry is 40~44℃, and the flow rate of the polishing slurry is 120~150mL / min.
2. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, During the growth of the buffer layer, carbon source gas, silicon source gas, and hydrogen are introduced. The hydrogen flow rate in the central path is 50~200 SLM, the hydrogen flow rate in the bypass path is 30~100 SLM, the growth temperature is 1580~1650℃, the C / Si ratio is 0.5~0.9, and the growth rate is 6~10 μm / h.
3. The method for improving the quality of silicon carbide epitaxial layers according to claim 2, characterized in that, The carrier concentration of the buffer layer is ≥1E18, and the thickness of the buffer layer is 0.5~2μm.
4. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, During the growth of the epitaxial layer, carbon source gas, silicon source gas, and hydrogen are introduced. The hydrogen flow rate in the central path is 50~200 SLM, the hydrogen flow rate in the bypass path is 30~100 SLM, the C / Si ratio is 0.85~1.2, the growth temperature is 1580~1650℃, and the growth rate is 50~70 μm / h.
5. The method for improving the quality of silicon carbide epitaxial layers according to claim 4, characterized in that, The carrier concentration of the epitaxial layer is ≤1E17, and the thickness is ≥5μm.
6. The method for improving the quality of silicon carbide epitaxial layers according to claim 2 or 4, characterized in that, The carbon source gas includes C2H2 or C3H8; the silicon source gas includes SiHCl3 or SiH4.
7. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, The polishing head of the chemical mechanical polishing process rotates at 100-120 rpm, and the polishing disc rotates at 80-100 rpm.
8. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, The thinning amount of the chemical mechanical polishing is 0.5~50μm.
9. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, The thinning amount of the chemical mechanical polishing is 1~2μm.
10. The method for improving the quality of silicon carbide epitaxial layers according to claim 1, characterized in that, The polishing solution comprises 15-30% alumina and 3-20% permanganate by mass.