High-purity silicon carbide spray header and preparation method thereof

Abstract

The invention discloses a high-purity silicon carbide spray header and a preparation method thereof, and the preparation method comprises the following steps: preparing a sacrificial layer which comprises a circular sheet-shaped substrate and a plurality of cylindrical bosses formed on the substrate; a first silicon carbide layer is deposited on the sacrificial layer, the deposition thickness needs to completely cover the boss, and a first deposition body is formed; removing the sacrificial layer in the first deposition body to form a precursor with first micropores; depositing a second silicon carbide layer on the surface, far away from the first micropores, of the precursor until the overall thickness of the sample reaches the required thickness to obtain a second deposition body; the first micropores in the second deposition body are expanded to obtain second micropores, the second micropores are subjected to through machining, the machining hole diameter is smaller than the original hole diameter, and spraying holes completely penetrating through the sample are formed. The silicon carbide spray header with the thickness exceeding 10 mm can be prepared, and the problems that in a traditional technology, the material purity is difficult to reach the standard, and micropore machining is difficult are solved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor wafer processing technology, and particularly relates to a high-purity silicon carbide spray head and its preparation method. Background Technology

[0002] Silicon carbide (SiC), as a third-generation wide-bandgap semiconductor material, exhibits unique application value in semiconductor equipment due to its excellent physicochemical properties (such as high breakdown field strength, high thermal conductivity, and high electron saturation drift velocity). The porous structure of high-purity silicon carbide is widely used in semiconductor manufacturing, such as in showerheads during wafer fabrication and sieves used in ion implantation. However, silicon carbide has extremely high hardness, with a Mohs hardness of 9.5, second only to diamond, making small-hole machining difficult, especially for silicon carbide thicker than 10 mm. Currently, the commonly used machining method is direct mechanical drilling, but due to the material's high hardness, tool breakage is common, resulting in a high drilling failure rate, long processing cycles, and low production efficiency, making it difficult to meet mass production demands.

[0003] Currently, the fabrication of high-purity silicon carbide spray heads faces significant challenges, primarily including: 1. Preparation of high-purity, dense silicon carbide material: The impurity content of silicon carbide materials used in semiconductor components such as spray heads must be controlled below 5 ppm. Few manufacturers currently possess the capability to prepare high-purity bulk materials with a thickness exceeding 10 mm. 2. High difficulty in micropore processing: Silicon carbide has a Mohs hardness of 9.5, second only to diamond. The surface of the spray head needs to be processed with thousands to tens of thousands of micropores (small in diameter), requiring each pore to have smooth walls and uniform inner walls, making the processing extremely difficult.

[0004] Therefore, how to efficiently manufacture high-purity silicon carbide spray heads is a key technical challenge that component manufacturers urgently need to overcome. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-purity silicon carbide spray head and its preparation method, thereby solving the problems of difficulty in achieving the required material purity and the difficulty in micropore processing when preparing silicon carbide spray heads with a thickness exceeding 10 mm.

[0006] The objective of this invention is achieved through the following technical solution: A high-purity silicon carbide spray head includes a substrate and a plurality of spray holes that completely penetrate the substrate. Each spray hole includes a first channel and a second channel that coincide with the central axis from top to bottom. The diameter of the second channel is smaller than the diameter of the first channel.

[0007] Preferably, the thickness of the substrate is 4~13mm.

[0008] Preferably, the diameter of the first channel is 1.0~3.0 mm and the depth is 1~7 mm.

[0009] Preferably, the diameter of the second channel is 0.5~2.0 mm.

[0010] The above-mentioned method for preparing a high-purity silicon carbide spray head includes the following steps: Prepare a sacrificial layer, the sacrificial layer comprising a circular sheet-like substrate and a plurality of cylindrical bosses formed on the substrate; A first silicon carbide layer is deposited on the sacrificial layer, and the deposition thickness is sufficient to completely cover the boss, forming a first deposit. The sacrificial layer in the first deposit is removed to form a precursor with first micropores; A second silicon carbide layer is deposited on the side of the precursor away from the first micropore until the overall thickness of the sample reaches the required thickness, thus obtaining a second deposit; the second deposit is the substrate of the high-purity silicon carbide spray head. The first micropore on the second deposit is enlarged to obtain a second micropore. The second micropore is then processed to form a through-hole with a diameter smaller than the original pore diameter, thereby forming a spray hole that completely penetrates the sample.

[0011] In this invention, the working holes on the spray head have high dimensional accuracy requirements (±0.01 mm). If the required small-diameter working holes are directly prepared in one machining operation, it is difficult to guarantee accuracy. Furthermore, since this invention employs a two-stage chemical vapor deposition process, the second deposition forms a dense silicon carbide layer, making it impossible to pre-form a through-hole structure. Therefore, the working holes must be shaped by machining after deposition. Considering that the cutting amount of hole enlargement is much less than direct drilling, significantly reducing machining difficulty and deformation risk, hole enlargement is preferred to enlarge the first micro-hole to obtain a second micro-hole with a larger diameter. Simultaneously, the working holes are primarily used for gas flow and are functionally crucial. If the entire sample area is designed as working holes, when the silicon carbide layer thickness exceeds 10 mm, deep drilling of small holes is prone to tool breakage or hole deviation, making machining difficult. Therefore, this invention adopts a step-by-step machining strategy: first, a larger-diameter second micro-hole is prepared as a guide hole, and then machining is performed on this basis to obtain a smaller-diameter working hole.

[0012] Preferably, in the step of preparing the sacrificial layer, the material of the sacrificial layer is graphite, carbon-carbon composite material, or silicon carbide ceramic preform.

[0013] Preferably, the total impurity content of the graphite is ≤5ppm, wherein the Fe ion content is ≤0.5ppm, the Cu ion content is ≤0.5ppm, and the Al ion content is ≤0.5ppm.

[0014] Preferably, the diameter of the cross-section of the boss is 0.5~2.5mm; the bosses are arranged in an array on the substrate.

[0015] Preferably, the thickness of the first deposit is 3~10 mm.

[0016] Preferably, the specific operation for removing the sacrificial layer in the first deposit is as follows: heating the first deposit at a temperature >1000°C in an oxygen-containing atmosphere to oxidize and remove the sacrificial layer.

[0017] Preferably, the thickness of the precursor with the first micropore is 2-8 mm; and the thickness of the second deposit is 4-13 mm.

[0018] Preferably, the diameter of the second micropore is 1.0~3.0 mm and the depth is 1~7 mm.

[0019] Preferably, in the step of processing the second micropore through, the diameter of the through-processed hole is 0.5~2.0mm.

[0020] Preferably, both the first silicon carbide layer and the second silicon carbide layer are prepared by chemical vapor deposition.

[0021] Preferably, both the first silicon carbide layer and the second silicon carbide layer are 3C-SiC crystal form (i.e. β-SiC), and both have a purity higher than 99.9995%.

[0022] This invention utilizes chemical vapor deposition to form a silicon carbide layer, resulting in a material with high purity, which creates favorable conditions for preparing high-quality silicon carbide spray heads. In contrast, silicon carbide prepared by sintering is difficult to meet the high purity requirements of spray heads.

[0023] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention employs a two-stage silicon carbide chemical vapor deposition method, which solves the problem that a single deposition is insufficient to achieve the required thickness. After the first deposition is completed, a second chemical vapor deposition is performed on the treated surface. Since both depositions are of the same silicon carbide material with consistent crystal form, there is no obvious boundary between the two depositions, thus meeting the requirements of silicon carbide spray heads for material thickness and structural integrity.

[0024] (2) In this invention, the surface of the sacrificial layer is provided with multiple cylindrical bosses. A first silicon carbide layer is formed on the sacrificial layer by chemical vapor deposition, which completely covers and replicates the shape of the bosses. After removing the sacrificial layer, a first microhole is formed in the first silicon carbide layer corresponding to the position of the boss. Subsequently, the first microhole is enlarged to obtain a second microhole with a larger diameter. Finally, a working hole with a smaller diameter is machined based on the second microhole. Compared with drilling deep small holes directly in a thick silicon carbide layer, this method can significantly reduce tool wear, improve machining accuracy, and reduce manufacturing costs. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural diagram of the sacrificial layer according to an embodiment of the present invention.

[0026] Figure 2 This is a vertical cross-sectional view of the sacrificial layer described in an embodiment of the present invention.

[0027] Figure 3 This is a vertical cross-sectional view of the first deposit in an embodiment of the present invention.

[0028] Figure 4 This is a vertical cross-sectional view of the precursor described in an embodiment of the present invention.

[0029] Figure 5 This is a vertical cross-sectional view of the second deposit in an embodiment of the present invention.

[0030] Figure 6 This is a vertical cross-sectional view of the second deposited body after pore enlargement as described in an embodiment of the present invention.

[0031] Figure 7 This is a vertical cross-sectional view of the high-purity silicon carbide spray head product described in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] refer to Figures 1-7 This invention discloses a method for preparing a high-purity silicon carbide spray head, the specific steps of which are as follows: A sacrificial layer is prepared, comprising a circular sheet-like substrate and a plurality of cylindrical protrusions formed on the substrate; the three-dimensional structural schematic diagram and vertical cross-sectional view of the sacrificial layer are shown in Figures 1 and 2, respectively. We can see that the bottom surface of the sacrificial layer is circular, and a plurality of cylindrical protrusions are evenly distributed on the bottom surface.

[0034] A first silicon carbide layer is deposited on the sacrificial layer, with a thickness sufficient to completely cover the boss, forming a first deposit; a vertical cross-sectional view of the first deposit is shown below. Figure 3 As shown, we start from Figure 3 As can be seen, the first silicon carbide layer is deposited on one side of the sacrificial layer and can completely cover the protrusions on the sacrificial layer.

[0035] The sacrificial layer in the first deposit is removed to form a precursor with first micropores; a vertical cross-sectional view of the precursor is shown below. Figure 4 As shown, from Figure 4 As can be seen, after removing the sacrificial layer, a first micropore is formed in the first silicon carbide layer at the position corresponding to the boss.

[0036] A second silicon carbide layer is deposited on the side of the precursor away from the first micropore until the overall thickness of the sample reaches the desired thickness, thus obtaining a second deposit; a vertical cross-sectional view of the second deposit is shown below. Figure 5 As shown, since the thickness of the first silicon carbide layer deposited earlier has not yet met the process requirements of the spray head, a second silicon carbide layer needs to be deposited. After the deposition is completed, the overall thickness of the sample will meet the process requirements.

[0037] The first micropore on the second deposit is enlarged to obtain a second micropore. The second micropore is then processed to create a through-hole with a diameter smaller than the original pore diameter, thus forming a spray hole that completely penetrates the sample. (See also...) Figures 6-7 , Figure 6 This is a vertical cross-sectional view of the second deposit after pore enlargement; Figure 7 The image shows a vertical cross-section of a high-purity silicon carbide spray head. We can see that by preparing micropores with smaller diameters based on the second micropore, a passage can be formed in the thickness direction of the sample, which is a necessary condition for the normal operation of the spray head.

[0038] Considering the availability and cost of materials, graphite is chosen as the material for the sacrificial layer in the step of preparing the sacrificial layer.

[0039] Furthermore, in order to avoid the introduction of impurity ions, the purity of graphite needs to be limited. Specifically, the total impurity content of graphite should be ≤5ppm, of which the Fe ion content should be ≤0.5ppm, the Cu ion content should be ≤0.5ppm, and the Al ion content should be ≤0.5ppm.

[0040] Considering the thickness requirements, processing accuracy limitations, and process complexity of the silicon carbide spray head, the diameter of the cross-section of the boss is 0.5~2.5mm, and the bosses are arranged in an array on the substrate; the thickness of the first deposit is 3~10mm; the thickness of the precursor with the first micropore is 2~8mm; and the thickness of the second deposit is 4~13mm.

[0041] In order to efficiently remove the graphite sacrificial layer, the first deposit is heated at a temperature of >1000°C in an oxygen-containing atmosphere. As a result, the graphite is gradually oxidized by heating to form carbon dioxide, and eventually the sacrificial layer disappears. Correspondingly, the first micropores are formed at the protrusions on the sacrificial layer.

[0042] To reduce processing difficulty and deformation risk, a hole expansion process is preferred. First, the first micropore is expanded to obtain the second micropore. Then, based on the second micropore, a micropore that penetrates the thickness of the sample is processed. The diameter of this micropore is the diameter of the gas flow channel when the spray head is working.

[0043] Specifically, in some embodiments, the diameter of the second micropore is 1.0~3.0mm and the depth is 1~7mm; the diameter of the working hole of the spray head is 0.5~2.0mm.

[0044] To prepare high-purity silicon carbide, this embodiment employs chemical vapor deposition (CVD) to prepare the first and second silicon carbide layers. CVD is a mature process for preparing silicon carbide materials, and the details of the related technical operations will not be elaborated here. Testing revealed that both the first and second silicon carbide layers prepared in this embodiment are of the 3C-SiC crystal form (i.e., β-SiC), with a purity exceeding 99.9995%, meeting the high purity requirements of the spray head.

[0045] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-purity silicon carbide spray head, characterized in that, It includes a substrate and multiple spray holes that completely penetrate the substrate. Each spray hole includes a first channel and a second channel that coincide with the central axis from top to bottom. The diameter of the second channel is smaller than the diameter of the first channel.

2. The high-purity silicon carbide spray head according to claim 1, characterized in that, The thickness of the substrate is 4~13mm; and / or The diameter of the first channel is 1.0~3.0 mm, and the depth is 1~7 mm; and / or The diameter of the second channel is 0.5~2.0mm.

3. The method for preparing the high-purity silicon carbide spray head according to any one of claims 1 to 2, characterized in that, Includes the following steps: Prepare a sacrificial layer, the sacrificial layer comprising a circular sheet-like substrate and a plurality of cylindrical bosses formed on the substrate; A first silicon carbide layer is deposited on the sacrificial layer, and the deposition thickness is sufficient to completely cover the boss, forming a first deposit. The sacrificial layer in the first deposit is removed to form a precursor with first micropores; A second silicon carbide layer is deposited on the side of the precursor away from the first micropore until the overall thickness of the sample reaches the desired thickness, thus obtaining a second deposit. The first micropore on the second deposit is enlarged to obtain a second micropore. The second micropore is then processed to form a through-hole with a diameter smaller than the original pore diameter, thereby forming a spray hole that completely penetrates the sample.

4. The method for preparing the high-purity silicon carbide spray head according to claim 3, characterized in that, In the step of preparing the sacrificial layer, the material of the sacrificial layer is graphite, carbon-carbon composite material or silicon carbide ceramic preform.

5. The method for preparing the high-purity silicon carbide spray head according to claim 4, characterized in that, The graphite has a total impurity content of ≤5ppm, of which Fe ion content is ≤0.5ppm, Cu ion content is ≤0.5ppm, and Al ion content is ≤0.5ppm.

6. The method for preparing the high-purity silicon carbide spray head according to claim 3, characterized in that, The diameter of the cross-section of the boss is 0.5~2.5mm; the bosses are arranged in an array on the substrate; and / or The thickness of the first deposit is 3~10 mm.

7. The method for preparing the high-purity silicon carbide spray head according to claim 3, characterized in that, The specific operation for removing the sacrificial layer from the first deposit is as follows: under an oxygen-containing atmosphere, the first deposit is heated at a temperature >1000°C to oxidize and remove the sacrificial layer.

8. The method for preparing the high-purity silicon carbide spray head according to claim 6, characterized in that, The thickness of the precursor with the first micropore is 2-8 mm; the thickness of the second deposit is 4-13 mm.

9. The method for preparing the high-purity silicon carbide spray head according to claim 8, characterized in that, The diameter of the second micropore is 1.0~3.0 mm, and the depth is 1~7 mm; and / or In the step of processing the second micro-hole through, the diameter of the through-processed hole is 0.5~2.0mm.

10. The method for preparing the high-purity silicon carbide spray head according to claim 3, characterized in that, Both the first silicon carbide layer and the second silicon carbide layer were prepared by chemical vapor deposition; and / or Both the first silicon carbide layer and the second silicon carbide layer are 3C-SiC crystals, and their purity is higher than 99.9995%.

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