PVT device for preparing SiC coating and preparation method

Abstract

The invention provides a PVT device for preparing a SiC coating and a preparation method. The PVT device for preparing the SiC coating comprises a shell with a PVT cavity, a fixed bottom support installed on a bottom plate of the shell, a rotating material table rotationally arranged at the upper end of the PVT cavity through a rotating shaft and a graphite electrode vertically arranged in the PVT cavity, and the upper surface, extending into the PVT cavity, of the fixed bottom support is provided with a heating device and a silicon carbide powder material table. The graphite electrode is located on the outer side of the rotary material table and the outer side of the silicon carbide powder material table, and the upper end of the graphite electrode is lower than the lower surface of the rotary material table. At least two exhaust pipes are arranged on a top plate of the shell and located between the rotary material table and the graphite electrode. The upper end of the graphite electrode is lower than the lower surface of the rotary material table, a certain distance exists between the graphite electrode and the rotary material table, temperature difference is formed, and silicon carbide is concentrated on the rotary material table to be deposited.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of semiconductor coating materials, and in particular to a PVT device and a preparation method for preparing a SiC coating. Background Art

[0002] With the rapid development of the semiconductor industry, the third-generation semiconductor SiC material has demonstrated disruptive advantages in high-voltage, high-temperature, and high-frequency scenarios due to its unique wide bandgap characteristics, high thermal conductivity and electronic performance, low on-resistance, and high power density. It has become the core material in the fields of new energy revolution (such as electric vehicles, photovoltaic inverters), ultra-high voltage power grids, industrial motors, etc., and has been widely used in more stringent usage scenarios such as new energy and power systems, high frequency and high power.

[0003] The third-generation semiconductor SiC materials are divided into two major applications in semiconductors. One is SiC crystal growth (both single crystal and crystal growth are crystal growth), which is used as the core substrate material for manufacturing third-generation semiconductor products such as power devices and radio frequency devices; the other is SiC coating, which is prepared on the substrate surface by physical or chemical vapor deposition, spraying and other methods.

[0004] As the semiconductor industry continues to advance, the requirements for semiconductor devices are becoming increasingly stringent. High-quality, uniform semiconductor devices are in widespread demand. For SiC-coated semiconductor devices, the substrate material is typically graphite, which has a similar thermal expansion coefficient. Most SiC-coated semiconductor devices are fabricated and produced using chemical vapor deposition (CVD), while a few utilize physical vapor deposition (PVD). However, both methods currently have their advantages and disadvantages in the fabrication of SiC-coated semiconductor devices.

[0005] There are two existing methods for preparing SiC-coated semiconductor devices:

[0006] (1) CVD has the following advantages and disadvantages:

[0007] Advantages: CVD is currently the mainstream process for preparing SiC coatings on graphite. This method can be used for SiC coatings on semiconductor devices with a thickness between 30 and 300 μm. The resulting SiC coating has good uniformity, generally with a deviation of about ±10%. For example, if the target thickness is 100 μm, a SiC coating with a thickness between 90 and 110 μm can be prepared by CVD.

[0008] Disadvantages: The process flow is complex and process control is difficult.

[0009] (2) PVT has the following advantages and disadvantages:

[0010] Advantages: PVT (physical vapor transport) is the current mainstream method for SiC crystal growth (single crystal, crystal growth is both crystal growth) or other single crystals. PVT does not involve chemical reactions and has the characteristics of mature technology and strong process controllability. It is widely used in the large-scale production of silicon carbide substrates.

[0011] Disadvantages: The SiC coating prepared by the existing PVT method has poor uniformity.

[0012] Prior art (Chinese invention patent application publication number CN119194591A) discloses a PVT-based silicon carbide coating growth apparatus and method. The apparatus employs an induction coil heater positioned outside an insulation blanket, a graphite barrel positioned inside the blanket, and a rotating platform positioned above the barrel. The upper end of the barrel covers the rotating platform, and the exhaust port is located directly above the rotating platform. The central exhaust position results in poor exhaust flow, allowing exhaust gas to accumulate within a certain height area, forming vortices. This results in inconsistent carbonization concentrations horizontally within the area, hindering the reaction and leading to uneven coating preparation, which in turn affects product quality. Summary of the Invention

[0013] The purpose of the present invention is to provide a PVT device and a preparation method for preparing SiC coatings, thereby improving the uniformity of silicon carbide coating preparation of products and ensuring product molding quality.

[0014] The technical solution of the present invention is: a PVT device for preparing SiC coating, comprising a shell having a PVT chamber, a fixed base mounted on the bottom plate of the shell, a rotating material table arranged at the upper end of the PVT chamber and rotating through a rotating shaft, and a graphite electrode vertically arranged in the PVT chamber, the upper surface of the fixed base extending into the PVT chamber is provided with a heating device and a silicon carbide powder material table, the graphite electrode is located outside the rotating material table and the silicon carbide powder material table, and the upper end of the graphite electrode is lower than the lower surface of the rotating material table; at least two exhaust pipes are provided on the top plate of the shell, and at least two of the exhaust pipes are located between the rotating material table and the graphite electrode.

[0015] In the above scheme, by lowering the upper end of the graphite electrode below the lower surface of the rotating material table, a certain distance is created between the two, forming a temperature difference, so that silicon carbide is concentrated and deposited on the rotating material table; in addition, the exhaust pipe is located between the rotating material table and the graphite electrode, so that the sublimated silicon carbide on the outside of the rotating material table is discharged, the concentration on the outside is reduced, and the silicon carbide on the inside will diffuse toward the outside, so as to achieve a consistent silicon carbide concentration in the horizontal direction within an area, ensure the uniformity of the preparation of the silicon carbide coating on the workpiece surface, and improve product quality.

[0016] Preferably, the silicon carbide powder material table is provided with a plurality of honeycomb holes for placing silicon carbide powder, and the plurality of honeycomb holes are distributed as a plurality of circular circles diverging from the center toward the outside.

[0017] Preferably, the number of honeycomb holes radiating from the circular ring gradually increases from the inner ring to the outer ring, and the aperture of a single honeycomb hole gradually decreases from the inner ring to the outer ring; the exhaust pipe corresponds vertically to the honeycomb holes in the outer ring.

[0018] Preferably, the rotating material table is located directly above the silicon carbide powder material table.

[0019] Preferably, a soft felt is provided on the inner wall of the PVT chamber formed by the shell, and a hard felt is provided on the inner surface of the soft felt.

[0020] Preferably, a pressure gauge, a first thermometer and a second thermometer are provided in the PVT chamber. The pressure gauge and the second thermometer are respectively provided between the graphite electrode and the rotating material table. The first thermometer is provided beside the silicon carbide powder material table.

[0021] Preferably, the lower end of the graphite electrode is located at the lower side of the heating device.

[0022] The present invention also provides a method for preparing a PVT device using the above-mentioned SiC coating, comprising:

[0023] Place silicon carbide powder on a silicon carbide powder table, fix the workpiece on a rotating table, start the heating device to gasify and sublime the silicon carbide powder; start the graphite electrode to heat the sublimated gas evenly and rise to the deposition surface of the rotating table for deposition; the exhaust pipe discharges the sublimated silicon carbide on the outside of the rotating table, making the silicon carbide concentration on the outside of the rotating table lower than that on the inside, causing the silicon carbide on the inside to diffuse to the outside. In this process, a uniform silicon carbide coating is obtained on the workpiece.

[0024] Compared with the related art, the present invention has the following beneficial effects:

[0025] 1. The present invention places the upper end of the graphite electrode below the lower surface of the rotating material table, with a certain distance between the two, to form a temperature difference, so that silicon carbide is concentrated and deposited on the rotating material table, thereby ensuring the molding quality;

[0026] 2. The present invention arranges the exhaust pipe between the rotating material table and the graphite electrode, so that the sublimated silicon carbide on the outside of the rotating material table is discharged, the concentration on the outside is reduced, and the silicon carbide on the inside will diffuse toward the outside, so as to achieve a consistent silicon carbide concentration in the horizontal direction within an area, ensure the uniformity of the silicon carbide coating preparation on the workpiece surface, and improve product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic structural diagram of a PVT device for preparing a SiC coating provided by the present invention;

[0028] Figure 2 It is a structural diagram of the silicon carbide powder material platform;

[0029] Figure 3 Schematic diagram of the arrangement structure of the exhaust pipe on the top plate of the shell;

[0030] Figure 4 Schematic diagram of XRD results of sample No. 3 in parameter table;

[0031] Figure 5 This is a schematic diagram of the SEM surface results of the sample No. 3 in the parameter table;

[0032] Figure 6 This is a schematic diagram of the SEM cross-sectional results of the sample No. 3 in the parameter table;

[0033] Figure 7 Schematic diagram of the point arrangement for measuring the thickness of SiC coating.

[0034] In the accompanying drawings: 1. PVT chamber; 2. soft felt; 3. hard felt; 4. graphite electrode; 5. fixed base; 6. heating device; 7. silicon carbide powder material table; 8. first thermometer; 9. second thermometer; 10. rotating material table; 11. exhaust pipe; 12. rotating shaft; 13. pressure gauge; 14. outer casing. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments and features of the embodiments may be combined unless they conflict. For ease of description, the words "upper," "lower," "left," and "right" appear below merely to indicate the directions of upper, lower, left, and right in the accompanying drawings and do not limit the structure.

[0036] like Figure 1 As shown, a PVT device for preparing SiC coating provided in this embodiment includes a PVT chamber 1, a soft felt 2, a hard felt 3, a graphite electrode 4, a fixed base 5, a heating device 6, a silicon carbide powder material table 7, a first thermometer 8, a second thermometer 9, a rotating material table 10, an exhaust pipe 11, a rotating shaft 12, a pressure gauge 13 and a housing 14.

[0037] The outer shell 14 is a stainless steel shell that encloses the sealed PVT chamber 1. The inner wall of the PVT chamber 1 formed by the outer shell 14 is provided with a soft felt 2, and the inner surface of the soft felt 2 is provided with a hard felt 3. The soft felt 2 is a carbon fiber soft felt that, in conjunction with the hard felt 3, completely covers the exterior of the hard felt 3 and has a certain thickness to achieve the thermal insulation effect of the PVT chamber 1. The hard felt 3 has a certain hardness and thickness to provide structural support, and in conjunction with the soft felt 2, it achieves the thermal insulation effect of the PVT chamber 1.

[0038] The fixed base 5 is mounted on the bottom plate of the housing 14. A rotating shaft 12 is rotatably mounted on the top plate of the housing 14. A rotating table 10 is rotatably mounted on the upper end of the PVT chamber 1 via the rotating shaft 12. The fixed base 5 extends into the upper surface of the PVT chamber 1 and is provided with a heating device 6 and a silicon carbide powder feed table 7. At least two exhaust pipes 11 are mounted on the top plate of the housing 14, and are located between the rotating table 10 and the graphite electrode 4.

[0039] The graphite electrode 4 is vertically positioned within the PVT chamber 1, outside the rotating stage 10 and the silicon carbide powder stage 7. The graphite electrode 4 utilizes resistance heating, primarily to uniformly heat and elevate the sublimated silicon carbide powder. The upper end of the graphite electrode 4 is lower than the lower surface of the rotating stage 10. This height difference creates a temperature difference between the trailing end (upper end) of the graphite electrode 4 and the rotating stage 10, facilitating SiC deposition on the rotating stage 10.

[0040] The fixed base 5 is made of graphite and has a cylindrical structure. Its function is to support the heating device 6 and the silicon carbide powder material platform 7.

[0041] The function of the heating device 6 is to heat the silicon carbide powder in the silicon carbide powder material platform 7 to make it gasify and sublime, and to compensate for the heat loss of the graphite electrode 4 at the bottom of the PVT chamber 1 to avoid the formation of temperature difference at the bottom of the PVT chamber 1.

[0042] like Figure 2As shown, the silicon carbide powder platform 7 is circular and has multiple honeycomb holes 71 on it. The honeycomb holes 71 are arranged in a circular pattern radiating outward from the center, such as three layers: inner, middle, and outer rings. The honeycomb holes 71 in the inner ring are relatively sparse, while those in the outer ring are denser. Silicon carbide powder is placed in each honeycomb hole 71. The individual honeycomb holes 71 in the inner ring are slightly larger in diameter, fewer in number, and more sparsely distributed, with a greater distance from the middle ring. This is designed to maximize the reduction in silicon carbide concentration per unit area in the inner ring during thermal evaporation, bringing it to the same level as that in the middle ring. The individual honeycomb holes 71 in the middle ring have a medium diameter, but are more numerous and more densely distributed than those in the middle ring. The distance from the outer ring is reduced, resulting in a lower silicon carbide concentration per unit area than would be achieved under normal design. The diameter of a single honeycomb hole 71 on the outer ring is the smallest. Although the number per unit area is large, the concentration in this area is generally equal to the silicon carbide concentration in the middle ring. However, since the outer ring corresponds vertically to the exhaust pipe 11, the silicon carbide concentration in the outer ring will be slightly lower than that in the middle ring under the condition of continuous exhaust from the exhaust pipe 11, causing the silicon carbide in the middle ring to diffuse toward the outer ring. Similarly, due to the concentration difference between the inner ring and the middle ring, the inner ring diffuses toward the middle ring, achieving consistent silicon carbide concentrations in the three regions, thereby uniformly depositing the silicon carbide coating on the rotating material table 10, and finally preparing a uniform silicon carbide coated graphite product.

[0043] like Figure 1 、 Figure 3 As shown, the exhaust pipe 11 is cylindrical, and multiple exhaust pipes 11 are evenly distributed on the top plate of the outer shell 14 in a circular pattern. And multiple exhaust pipes 11 are arranged near the honeycomb holes 71 of the outer circle, so that only the outer circle can be exhausted. The diameter of the circle enclosed by the multiple exhaust pipes 11 is larger than the diameter of the rotating material table 10, and is similar to the diameter of the silicon carbide powder material table 7. This design achieves two effects: first, the diameter of the rotating material table 10 is smaller than the diameter enclosed by the exhaust pipe 11, which will not affect the exhaust at the top; second, the exhaust pipe 11 and the silicon carbide powder material table 7 are on the same diameter at different heights and are vertically facing each other. Silicon carbide evaporated and sublimated from the outer circle of the silicon carbide powder material table 7 can be discharged more smoothly from the exhaust pipe 11. The evaporated and sublimated silicon carbide in the middle and inner rings of the silicon carbide powder material table 7 will diffuse to the outer ring, reducing the silicon carbide concentration in the inner ring. Combined with the structural design that the middle honeycomb holes 71 of the silicon carbide powder material table 7 are relatively sparse and the outer ring honeycomb holes 71 are relatively dense, the overall silicon carbide concentration in the PVT chamber 1 is uniform, and finally a uniform silicon carbide coating is prepared.

[0044] The present invention also provides a method for preparing a PVT device using the above-mentioned method for preparing a SiC coating, comprising: placing silicon carbide powder on a silicon carbide powder platform 7, and securing a workpiece on a rotating platform 10 with the surface to be deposited facing downward. Activating a heating device 6 to vaporize and sublime the silicon carbide powder; and activating a graphite electrode 4 to uniformly heat the sublimated gas and cause it to rise to the deposition surface of the rotating platform 10 for deposition. An exhaust pipe 11 discharges the sublimated silicon carbide located outside the rotating platform 10, reducing the concentration of silicon carbide outside the rotating platform 10 to a lower level than that inside. This causes the silicon carbide inside to diffuse outward, resulting in a uniform silicon carbide coating on the workpiece.

[0045] Comparative Example

[0046] The present invention adopts the following parameters for preparation, and the parameter list is shown in Table 1:

[0047] Table 1: Parameters

[0048]

[0049] The XRD, SEM surface and SEM cross-section results of sample No. 3 in Table 1 are as follows: Figure 4-Figure 6 As shown, and in accordance with Figure 7 The thickness of the SiC coating was measured at several points, and the measurement results showed that the average thickness of the SiC coating was 103 μm, with a uniformity of 5.91%.

[0050] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A PVT device for preparing a SiC coating, comprising a housing (14) having a PVT chamber (1), a fixed base (5) mounted on the bottom plate of the housing (14), a rotating material table (10) arranged at the upper end of the PVT chamber (1) and rotating via a rotating shaft (12), and a graphite electrode (4) vertically arranged in the PVT chamber (1), characterized in that: The fixed base (5) extends into the upper surface of the PVT chamber (1) and is provided with a heating device (6) and a silicon carbide powder material table (7); the graphite electrode (4) is located outside the rotating material table (10) and the silicon carbide powder material table (7), and the upper end of the graphite electrode (4) is lower than the lower surface of the rotating material table (10); at least two exhaust pipes (11) are provided on the top plate of the shell (14), and at least two of the exhaust pipes (11) are located between the rotating material table (10) and the graphite electrode (4).

2. The PVT device for preparing SiC coating according to claim 1, characterized in that: The silicon carbide powder material platform (7) is provided with a plurality of honeycomb holes (71) for placing silicon carbide powder, and the plurality of honeycomb holes (71) are distributed in the form of a plurality of circular circles diverging from the center toward the outside.

3. The PVT device for preparing SiC coating according to claim 2, characterized in that: The number of honeycomb holes (71) diverging from the circular circle gradually increases from the inner circle to the outer circle, and the aperture of a single honeycomb hole (71) gradually decreases from the inner circle to the outer circle; the exhaust pipe (11) corresponds vertically to the honeycomb holes (71) of the outer circle.

4. The PVT device for preparing SiC coating according to claim 1, characterized in that: The rotating material table (10) is located directly above the silicon carbide powder material table (7).

5. The PVT device for preparing SiC coating according to claim 1, characterized in that: A soft felt (2) is provided on the inner wall of the PVT chamber (1) formed by the shell (14), and a hard felt (3) is provided on the inner surface of the soft felt (2).

6. The PVT device for preparing SiC coating according to claim 1, characterized in that: A pressure gauge (13), a first thermometer (8) and a second thermometer (9) are provided in the PVT chamber (1); the pressure gauge (13) and the second thermometer (9) are respectively provided between the graphite electrode (4) and the rotating material table (10); and the first thermometer (8) is provided beside the silicon carbide powder material table (7).

7. The PVT device for preparing SiC coating according to claim 1, characterized in that: The lower end of the graphite electrode (4) is located on the lower side of the heating device (6).

8. A method for preparing a PVT device using the SiC coating according to any one of claims 1 to 7, characterized in that: include: Silicon carbide powder is placed on a silicon carbide powder material table (7), a workpiece is fixed on a rotating material table (10), and a heating device (6) is started to gasify and sublime the silicon carbide powder; a graphite electrode (4) is started to uniformly heat the sublimated gas and allow it to rise to a deposition surface of the rotating material table (10) and deposit; an exhaust pipe (11) discharges the sublimated silicon carbide located outside the rotating material table (10), so that the silicon carbide concentration outside the rotating material table (10) is lower than that inside, causing the silicon carbide inside to diffuse outward. In this process, a uniform silicon carbide coating is obtained on the workpiece.

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