Preparation method of silicon carbide epitaxial structure
By regulating the silicon-hydrogen ratio and growth method of the silicon carbide epitaxial layer, the problem of microscopic short steps overlapping and aggregation of the surface of the silicon carbide epitaxial structure is solved, the surface roughness is reduced, and the quality of the epitaxial structure is improved.
Patent Information
- Application Number
- CN202411979576.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-18
AI Technical Summary
There is microscopic short steps overlapping and aggregation on the surface of the silicon carbide epitaxial structure, resulting in an increase in surface roughness and affecting device characteristics.
By adjusting the silicon-hydrogen ratio of the silicon carbide epitaxial layer to 2.5‰~3‰, the vertical airflow epitaxial growth method is adopted to grow the silicon carbide buffer layer and the epitaxial layer sequentially on the silicon carbide substrate to reduce the difference in growth rates between steps and reduce the overlap of steps.
It effectively improves the overlapping aggregation of microsteps on the epitaxial surface of silicon carbide, reduces the surface roughness, and improves the quality of the epitaxial structure.
Smart Images
Figure CN119843361A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a method for preparing a silicon carbide epitaxial structure. Background Art
[0002] In recent years, the application of silicon carbide wafers as substrate materials has gradually matured and entered the industrialization stage. With silicon carbide wafers as substrates, a single crystal is usually deposited on the wafer using chemical vapor deposition (CVD) to form an epitaxial structure. Among them, the silicon carbide epitaxial layer is grown on a 4H-SiC conductive silicon carbide substrate to obtain a silicon carbide epitaxial structure, which can be further prepared into power devices for use in new energy vehicles, photovoltaic power generation, rail transportation, smart grids, aerospace and other fields.
[0003] During the epitaxial growth of 4H-SiC, parallel line clusters formed by multiple atomic steps converged together and parallel to the <1-100> direction are likely to appear on the surface. Step aggregation is a morphological feature that appears on the surface of the epitaxial layer, and there are no crystal defects. In low-loss Schottky diode (SBD) devices, step aggregation leads to increased surface roughness of the epitaxial layer, which can cause increased device leakage current. Step aggregation has a negative impact on MOSFET channel mobility or oxide layer breakdown characteristics. In the silicon carbide epitaxial process, giant step aggregation is often alleviated by reducing the growth temperature and reducing C / Si, but microscopic short step overlap aggregation observed under the AFM atomic force microscope cannot be completely eliminated. These short step overlap aggregations will increase the surface roughness and affect the device characteristics. Summary of the invention
[0004] The object of the present invention is to provide a method for preparing a silicon carbide epitaxial structure. The method provided by the present invention can solve the problem of increased roughness caused by overlapping and aggregation of microscopic short steps on the surface of the silicon carbide epitaxial structure, thereby improving the quality of the silicon carbide epitaxial structure.
[0005] In order to achieve the above object, the present invention provides the following technical solutions:
[0006] The present invention provides a method for preparing a silicon carbide epitaxial structure, comprising the following steps:
[0007] Placing a silicon carbide substrate in a reaction chamber, introducing a carbon source, a silicon source and hydrogen into the reaction chamber, and sequentially growing a silicon carbide buffer layer and a silicon carbide epitaxial layer on the surface of the silicon carbide substrate in a vertical gas flow direction epitaxial growth manner to obtain the silicon carbide epitaxial structure;
[0008] When the silicon carbide epitaxial layer is grown, the silicon-to-hydrogen ratio is 2.5‰ to 3‰.
[0009] Preferably, when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio is 2.7‰ to 2.8‰.
[0010] Preferably, the carbon source includes propane; and the silicon source includes silane.
[0011] Preferably, when growing the silicon carbide buffer layer, the carbon-silicon ratio is 0.8-1.2, and the silicon-hydrogen ratio is 2.5‰-3‰.
[0012] Preferably, the conditions for growing the silicon carbide buffer layer include: a temperature of 1620-1650° C., a growth pressure of 150 mbar, and a time of 15-120 s.
[0013] Preferably, the silicon carbide buffer layer has a thickness of 0.1-1 μm.
[0014] Preferably, when growing the silicon carbide epitaxial layer, the carbon-silicon ratio is 0.8 to 1.2.
[0015] Preferably, the temperature for growing the silicon carbide epitaxial layer is 1600-1650° C., the growth pressure is 150 mbar, and the time is 300-8000 s.
[0016] Preferably, the thickness of the silicon carbide epitaxial layer is 5-100 μm.
[0017] Preferably, before the growth, the method further includes pre-treating the silicon carbide substrate;
[0018] The pretreatment includes cleaning and etching in sequence.
[0019] The present invention provides a method for preparing a silicon carbide epitaxial structure, comprising the following steps: placing a silicon carbide substrate in a reaction chamber, introducing a carbon source, a silicon source and hydrogen into the reaction chamber, and using an epitaxial growth method in a vertical gas flow direction to sequentially grow a silicon carbide buffer layer and a silicon carbide epitaxial layer on the surface of the silicon carbide substrate to obtain the silicon carbide epitaxial structure; when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio is 2.5‰ to 3‰. The present invention adjusts the silicon-hydrogen ratio during the growth of the epitaxial layer, so that during the growth of the epitaxial layer, the difference in growth rate between different steps is reduced, the step overlap is reduced, and the short step overlap aggregation on the surface is improved, thereby reducing the surface roughness and improving the quality of the silicon carbide epitaxial structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Example 1;
[0021] Figure 2 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Example 2;
[0022] Figure 3 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 1;
[0023] Figure 4 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 2;
[0024] Figure 5 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 3;
[0025] Figure 6 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Example 1;
[0026] Figure 7 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Example 2;
[0027] Figure 8 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 1;
[0028] Fig. 9 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 2;
[0029] Fig.10 This is the AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 3. DETAILED DESCRIPTION
[0030] The present invention provides a method for preparing a silicon carbide epitaxial structure, comprising the following steps:
[0031] Placing a silicon carbide substrate in a reaction chamber, introducing a carbon source, a silicon source and hydrogen into the reaction chamber, and sequentially growing a silicon carbide buffer layer and a silicon carbide epitaxial layer on the surface of the silicon carbide substrate in a vertical gas flow direction epitaxial growth manner to obtain the silicon carbide epitaxial structure;
[0032] When the silicon carbide epitaxial layer is grown, the silicon-to-hydrogen ratio is 2.5‰ to 3‰.
[0033] In the present invention, the size of the silicon carbide substrate is preferably 6 to 8 inches.
[0034] Before the growth, the present invention also preferably includes pre-treating the silicon carbide substrate; the pre-treating preferably includes cleaning and etching in sequence. The present invention has no special limitation on the cleaning process, and the process familiar to those skilled in the art can be adopted. In the present invention, the etching process is preferably: etching the silicon carbide substrate in a hydrogen atmosphere. In the present invention, the etching temperature is preferably 1600°C, the pressure is preferably 15KPa, and the time is preferably 10min; the flow rate of the hydrogen is preferably 120L / min.
[0035] In the present invention, the carbon source preferably includes propane; and the silicon source preferably includes silane.
[0036] In the present invention, when growing the silicon carbide buffer layer, the carbon-silicon ratio is preferably 0.8-1.2, specifically 0.8, 0.85, 0.9, 1.0, 1.1, 1.2; the silicon-hydrogen ratio is preferably 2.5‰-3‰, specifically 2.5‰, 2.6‰, 2.7‰, 2.8‰, 2.9‰, 3.0‰. In the present invention, the conditions for growing the silicon carbide buffer layer preferably include: a temperature of 1620-1650°C, more preferably 1630°C; a growth pressure of preferably 150mbar; a time of 15-120s, more preferably 75s.
[0037] The present invention has no special limitation on the process of growing the silicon carbide buffer layer, and any method known to those skilled in the art can be adopted. In the present invention, the thickness of the silicon carbide buffer layer is preferably 0.1 to 1 μm, and more preferably 1 μm.
[0038] In the present invention, when growing the silicon carbide epitaxial layer, the carbon-silicon ratio is preferably 0.8-1.2, specifically 0.8, 0.9, 1.0, 1.1, or 1.2.
[0039] In the present invention, when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio is 2.5‰ to 3‰, more preferably 2.7‰ to 2.8‰, and specifically can be 2.5‰, 2.6‰, 2.7‰, 2.8‰, 2.9‰, and 3.0‰. In the present invention, the temperature for growing the silicon carbide epitaxial layer is preferably 1600 to 1650°C, the growth pressure is preferably 150mbar, and the time is preferably 300 to 8000s, more preferably 660 to 7000s. The present invention has no special limitation on the process of growing the silicon carbide epitaxial layer, and it can be used as known to those skilled in the art. In the present invention, the thickness of the silicon carbide epitaxial layer is preferably 5 to 100μm.
[0040] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.
[0041] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0042] Example 1
[0043] A 6-inch silicon carbide substrate was cleaned and then placed in a reaction chamber. Hydrogen was introduced at a flow rate of 120 L / min and etched at a pressure of 150 mbar and a temperature of 1630°C for 10 minutes.
[0044] Then, silane and propane were introduced into the reaction chamber at the same time, and a silicon carbide buffer layer was grown by epitaxial growth in the vertical gas flow direction at a pressure of 150 mbar and a temperature of 1630°C. The growth was maintained for 75 seconds to obtain a silicon carbide buffer layer with a thickness of 1 μm; wherein the silicon-carbon ratio was 0.85 and the silicon-hydrogen ratio was 2.7‰;
[0045] Then, a silicon carbide epitaxial layer was grown at a pressure of 150 mbar and a temperature of 1630° C., and the growth time was maintained for 660 s to prepare a silicon carbide epitaxial layer with a thickness of 10 μm; wherein the silicon-carbon ratio was 0.85, and the silicon-hydrogen ratio was 2.7‰, to obtain the silicon carbide epitaxial structure.
[0046] Example 2
[0047] A silicon carbide epitaxial structure was prepared in the manner of Example 1, except that when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio was controlled to be 3.0‰.
[0048] Comparative Example 1
[0049] A silicon carbide epitaxial structure was prepared in the manner of Example 1, except that when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio was controlled to be 3.3‰.
[0050] Comparative Example 2
[0051] A silicon carbide epitaxial structure was prepared in the manner of Example 1, except that when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio was controlled to be 3.6‰.
[0052] Comparative Example 3
[0053] A silicon carbide epitaxial structure was prepared in the manner of Example 1, except that when growing the silicon carbide epitaxial layer, the silicon-hydrogen ratio was controlled to be 4.3‰.
[0054] Performance Testing
[0055] The surfaces of the silicon carbide epitaxial structures obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were examined by AFM atomic force microscopy, and the surface morphologies obtained were as follows: Figures 1 to 10 As shown;
[0056] in Figure 1 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Example 1 with an area of 20nm*20nm, wherein Figure 2 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Example 2 with an area of 20nm*20nm. Figure 3 A planar AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 1 with an area of 20nm*20nm, Figure 4 This is a planar AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 2 with an area of 20nm*20nm. Figure 5 A plane AFM image of the silicon carbide epitaxial structure obtained in Comparative Example 3 with an area of 20nm*20nm;
[0057] Figure 6 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Example 1 with an area of 20nm*20nm. Figure 7 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Example 2 with an area of 20nm*20nm. Figure 8 This is an AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 1 with an area of 20nm*20nm. Fig. 9 The AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 2 with an area of 20nm*20nm, Fig.10 AFM 3D image of the silicon carbide epitaxial structure obtained in Comparative Example 3 with an area of 20nm*20nm;
[0058] from Figures 1 to 10 It can be seen that the surface roughness of the silicon carbide epitaxial structure obtained in Comparative Example 1 is Ra~0.284nm, and the protrusion thickness of some step overlapping areas is as high as 3.8nm; the surface roughness of the silicon carbide epitaxial structure obtained in Comparative Example 2 is Ra~0.429nm, and the protrusion thickness of some step overlapping areas is as high as 4.2nm; the surface roughness of the silicon carbide epitaxial structure obtained in Comparative Example 3 is Ra~1.94nm, and the protrusion thickness of some step overlapping areas is as high as 6.8nm; while the surface roughness of the silicon carbide epitaxial structure obtained in Example 1 is Ra~0.0737nm, and there is no step overlapping phenomenon on the surface; and the surface roughness of the silicon carbide epitaxial structure obtained in Example 2 is Ra~0.0952nm, and there is no step overlapping phenomenon on the surface.
[0059] It can be seen from this that the preparation method provided by the present invention can improve the overlapping aggregation of microscopic steps on the silicon carbide epitaxial surface, reduce the surface roughness, and thus improve the quality of the epitaxial structure.
[0060] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for preparing a silicon carbide epitaxial structure, characterized in that: The following steps are involved: Placing a silicon carbide substrate in a reaction chamber, introducing a carbon source, a silicon source and hydrogen into the reaction chamber, and sequentially growing a silicon carbide buffer layer and a silicon carbide epitaxial layer on the surface of the silicon carbide substrate in a vertical gas flow direction epitaxial growth manner to obtain the silicon carbide epitaxial structure; When the silicon carbide epitaxial layer is grown, the silicon-to-hydrogen ratio is 2.5‰ to 3‰.
2. The preparation method according to claim 1, characterized in that: When the silicon carbide epitaxial layer is grown, the silicon-to-hydrogen ratio is 2.7‰ to 2.8‰.
3. The preparation method according to claim 1, characterized in that: The carbon source includes propane; the silicon source includes silane.
4. The preparation method according to claim 1 or 3, characterized in that: When the silicon carbide buffer layer is grown, the carbon-to-silicon ratio is 0.8-1.2, and the silicon-to-hydrogen ratio is 2.5‰-3‰.
5. The preparation method according to claim 4, characterized in that: The conditions for growing the silicon carbide buffer layer include: a temperature of 1620-1650° C., a growth pressure of 150 mbar, and a time of 15-120 seconds.
6. The preparation method according to claim 1 or 5, characterized in that: The thickness of the silicon carbide buffer layer is 0.1-1 μm.
7. The preparation method according to claim 1, characterized in that: When the silicon carbide epitaxial layer is grown, the carbon-to-silicon ratio is 0.8-1.
2.
8. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature for growing the silicon carbide epitaxial layer is 1600-1650° C., the growth pressure is 150 mbar, and the time is 300-8000 s.
9. The preparation method according to claim 8, characterized in that: The thickness of the silicon carbide epitaxial layer is 5-100 μm.
10. The preparation method according to claim 1, characterized in that: Before the growth, the silicon carbide substrate is pre-treated; The pretreatment includes cleaning and etching in sequence.