Method for processing micropores in gas distribution plate

Abstract

The invention provides a method for machining micropores in a gas distribution plate, which comprises the following steps of: (1) sequentially performing rough turning and finish turning on a raw material blank to form a gas distribution plate primary machining product; and (2) drilling the surface of the gas distribution disc primary processing product to obtain a plurality of second-order combined holes. According to the machining method, rough turning and fine turning are sequentially conducted on a raw material blank, efficient machining of the raw material blank is achieved, it is guaranteed that an obtained gas distribution disc primary machining product has good planeness and parallelism, then drilling treatment is conducted on the surface of the gas distribution disc primary machining product, machining of a plurality of second-order combined holes with high density and high precision is achieved, and the machining precision of the gas distribution disc primary machining product is improved. Therefore, the performance of a semiconductor device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas distribution plate preparation, and relates to a processing method for micro-holes in a gas distribution plate. Background Art

[0002] In semiconductor manufacturing processes, a gas showerhead is a key component that is used to evenly distribute reaction gases onto the surface of a wafer to ensure the uniformity of thin film deposition or etching. As semiconductor process nodes continue to shrink, for example, they have advanced to more advanced processes such as 5nm and 3nm. Under these advanced process nodes, higher requirements are imposed on the uniformity of gas distribution.

[0003] However, existing gas showerheads have some obvious deficiencies. Traditional gas showerheads have a relatively low hole density, which makes it easy for gases to form turbulence during distribution. The emergence of turbulence will lead to non-uniform gas distribution, and thus cause a significant difference in the reaction rate between the edge and the center of the wafer. This difference will directly affect the quality and uniformity of thin film deposition or etching, thereby limiting the further improvement of semiconductor device performance.

[0004] To meet the strict requirements of advanced semiconductor processes for gas distribution uniformity, it is particularly important to develop a gas showerhead that can effectively improve gas distribution uniformity. Therefore, high-density micro-hole gas showerheads, as a potential solution, are gradually becoming a research hotspot.

[0005] In summary, providing a preparation method for a high-density micro-hole gas showerhead with high processing accuracy is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a processing method for micro-holes in a gas distribution plate. Through the process cooperation of rough turning, finish turning and drilling, combined with the control of specific parameters, the processing of second-order combined holes with high density and high precision is realized to manufacture a high-density micro-hole gas distribution plate, thereby improving the performance of semiconductor devices.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] The present invention provides a processing method for micro-holes in a gas distribution plate, and the processing method includes the following steps:

[0009] (1) Rough turning and finish turning are sequentially performed on a raw material blank to form a preliminary processed product of the gas distribution plate;

[0010] (2) Drilling treatment is performed on the surface of the preliminary processed product of the gas distribution plate to obtain a number of second-order combined holes.

[0011] The processing method provided by the present invention realizes the efficient processing of the raw material blank by successively performing rough turning and finish turning on the raw material blank, ensuring that the initially processed product of the gas distribution plate has good flatness and parallelism. Then, drilling treatment is performed on the surface of the initially processed product of the gas distribution plate to realize the processing of a number of second-order combined holes with high density and high precision, so as to manufacture a high-density microporous gas distribution plate, thereby improving the performance of semiconductor devices.

[0012] It should be noted that the aperture size, height, and position of the obtained number of second-order combined holes are consistent, enabling the high-density microporous gas distribution plate to achieve uniform diffusion of gas in a laminar flow form, improving the uniformity of thin film deposition or etching, and thus promoting the development of semiconductor manufacturing processes towards smaller process nodes.

[0013] As a preferred technical solution of the present invention, the material of the raw material blank in step (1) includes 6061 aluminum.

[0014] Preferably, the diameter of the raw material blank in step (1) is 500 - 600 mm, for example, it can be 510 mm, 520 mm, 530 mm, 540 mm, 550 mm, 560 mm, 570 mm, 580 mm, or 590 mm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] As a preferred technical solution of the present invention, the spindle speed of the rough turning in step (1) is 2000 - 6000 r / min, for example, it can be 2200 r / min, 2500 r / min, 2800 r / min, 3000 r / min, 3200 r / min, 3500 r / min, 3800 r / min, 4000 r / min, 4200 r / min, 4500 r / min, 4800 r / min, 5000 r / min, 5200 r / min, 5500 r / min, or 5800 r / min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the depth of cut of the rough turning in step (1) is 0.5 - 1 mm, for example, it can be 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, or 0.95 mm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the feed rate of the rough turning in step (1) is 0.3 - 1 mm / r. For example, it can be 0.35 mm / r, 0.4 mm / r, 0.45 mm / r, 0.5 mm / r, 0.55 mm / r, 0.6 mm / r, 0.65 mm / r, 0.7 mm / r, 0.75 mm / r, 0.8 mm / r, 0.85 mm / r, 0.9 mm / r or 0.95 mm / r, etc. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] As a preferred technical solution of the present invention, the spindle speed of the finish turning in step (1) is 2000 - 6000 r / min. For example, it can be 2200 r / min, 2500 r / min, 2800 r / min, 3000 r / min, 3200 r / min, 3500 r / min, 3800 r / min, 4000 r / min, 4200 r / min, 4500 r / min, 4800 r / min, 5000 r / min, 5200 r / min, 5500 r / min or 5800 r / min, etc. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the depth of cut of the finish turning in step (1) is 0.01 - 0.2 mm. For example, it can be 0.02 mm, 0.04 mm, 0.05 mm, 0.07 mm, 0.09 mm, 0.1 mm, 0.12 mm, 0.15 mm, 0.16 mm or 0.18 mm, etc. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the feed rate of the finish turning in step (1) is 0.01 - 0.1 mm / r. For example, it can be 0.02 mm / r, 0.03 mm / r, 0.04 mm / r, 0.05 mm / r, 0.06 mm / r, 0.07 mm / r, 0.08 mm / r or 0.09 mm / r, etc. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0021] It should be noted that by utilizing the synergistic effect between rough turning and finish turning and combining specific processing parameters, the preliminary processed product of the gas distribution plate obtained after processing the raw material blank has a good processing effect, and the preliminary processed product of the gas distribution plate has excellent flatness and parallelism, thereby ensuring the subsequent processing performance.

[0022] As a preferred technical solution of the present invention, the drilling treatment in step (2) is carried out using a step drill.

[0023] In the present invention, a step drill is used for drilling, which can avoid the problem of eccentricity compared with a flat-bottom drill and ensure the concentricity of the combined holes.

[0024] As a preferred technical solution of the present invention, the spindle speed of the drilling process in step (2) is 10,000 - 20,000 r / min. For example, it can be 11,000 r / min, 12,000 r / min, 13,000 r / min, 14,000 r / min, 15,000 r / min, 16,000 r / min, 17,000 r / min, 18,000 r / min or 19,000 r / min, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the feed rate of the drilling process in step (2) is 0.01 - 0.1 mm / r. For example, it can be 0.02 mm / r, 0.03 mm / r, 0.04 mm / r, 0.05 mm / r, 0.06 mm / r, 0.07 mm / r, 0.08 mm / r or 0.09 mm / r, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] It should be noted that by controlling the spindle speed and feed rate range of the drilling process, it is ensured that the aperture sizes, positions and heights of a number of second-order combined holes are consistent, achieving high-precision machining of micro-holes, and thus significantly enhancing the uniformity of gas distribution.

[0027] As a preferred technical solution of the present invention, after the drilling process in step (2), physical polishing, alcohol washing, chemical polishing and water washing are sequentially carried out.

[0028] In the present invention, the alcohol washing includes washing with ethanol.

[0029] Preferably, the surface roughness of the gas distribution plate after physical polishing is 0.1 - 0.4 μm. For example, it can be 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.22 μm, 0.25 μm, 0.28 μm, 0.3 μm, 0.32 μm, 0.35 μm, 0.36 μm or 0.38 μm, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the chemical polishing includes acid pickling for 30 - 120 s. For example, it can be 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s or 110 s, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the acid solution includes any one or a combination of at least two of phosphoric acid, nitric acid or nitric acid.

[0032] In the present invention, the mass concentrations and proportions of phosphoric acid, sulfuric acid and nitric acid are not specifically limited, as long as the surface defects can be removed, and those skilled in the art can determine according to the actual situation.

[0033] As a preferred technical solution of the present invention, in step (2), several of the second-order combined holes are evenly diffusely distributed outward from the center of the gas distribution plate.

[0034] Preferably, the density of the second-order combined holes on the gas distribution plate is 38-43 holes / cm 2 , for example, it can be 39 holes / cm 2 , 40 holes / cm 2 , 41 holes / cm 2 or 42 holes / cm 2 etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] In the present invention, the micropore density in the gas distribution plate is high, and the gas diffuses uniformly in a laminar flow form, thereby improving the uniformity of thin film deposition or etching.

[0036] As a preferred technical solution of the present invention, in step (2), the second-order combined holes are first-order holes and second-order holes that are sequentially connected along the direction from the upper end face to the lower end face of the gas distribution plate.

[0037] As a preferred technical solution of the present invention, the aperture of the first-order hole is 1.15-1.2 mm, for example, it can be 1.16 mm, 1.17 mm, 1.18 mm or 1.19 mm, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the aperture of the second-order hole is 0.68-0.72 mm, for example, it can be 0.685 mm, 0.69 mm, 0.695 mm, 0.7 mm, 0.705 mm or 0.71 mm, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the depth of the first-order hole ≥ the depth of the second-order hole.

[0040] Preferably, the first-order hole and the second-order hole are coaxially arranged.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The processing method provided by the present invention realizes the efficient processing of the raw material blank by sequentially performing rough turning and finish turning on the raw material blank, ensuring that the initially processed product of the gas distribution plate has good flatness and parallelism. Then, drilling treatment is performed on the surface of the initially processed product of the gas distribution plate to realize the processing of a number of second-order combined holes with high density and high precision, so as to manufacture a high-density microporous gas distribution plate, thereby improving the performance of semiconductor devices. Description of the Drawings

[0043] Figure 1 is a schematic diagram of the second-order combined holes obtained in Example 1 of the present invention;

[0044] Among them, 100 - second-order combined hole, 1 - first-order hole, 2 - second-order hole. Detailed Embodiments

[0045] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0046] Example 1

[0047] This example provides a processing method for micropores in a gas distribution plate. The processing method includes the following steps:

[0048] (1) Perform rough turning and finish turning on 6061 aluminum alloy with a diameter of 560 mm in sequence to form an initially processed product of the gas distribution plate;

[0049] The spindle speed of the rough turning is 3000 r / min, the depth of cut is 0.8 mm, and the feed rate is 0.6 mm / r; the spindle speed of the finish turning is 4000 r / min, the depth of cut is 0.1 mm, and the feed rate is 0.05 mm / r;

[0050] (2) Use a step drill to perform drilling treatment on the surface of the initially processed product of the gas distribution plate, and then perform physical polishing, ethanol cleaning, chemical polishing and water washing in sequence to obtain a number of second-order combined holes (as Figure 1 shown);

[0051] The spindle speed of the drilling treatment is 15000 r / min, and the feed rate is 0.05 mm / r;

[0052] The surface of the gas distribution plate is physically polished to a roughness of 0.25 μm;

[0053] The chemical polishing includes pickling with a mixed acid of nitric acid, phosphoric acid and sulfuric acid for 60 s. The mass concentration of the nitric acid is 15 wt%, the mass concentration of the phosphoric acid is 50 wt%, and the mass concentration of the sulfuric acid is 35 wt%.

[0054] A number of second-order combined holes 100 obtained in this embodiment are evenly distributed in a diffusion manner from the center of the gas distribution plate to the outside. The density of the second-order combined holes 100 on the gas distribution plate is 41 pieces / cm 2 ; The obtained second-order combined holes 100 include a first-order hole 1 and a second-order hole 2 that are sequentially connected and coaxial in the direction from the upper end surface to the lower end surface of the gas distribution plate; the aperture of the first-order hole 1 is 1.18 mm and the depth is 12.0 mm; the aperture of the second-order hole 2 is 0.7 mm and the depth is 3.0 mm.

[0055] In this embodiment, the hole shapes, hole sizes, and heights of a number of second-order combined holes on the gas distribution plate are consistent, and the position distribution of the holes is uniform.

[0056] Example 2

[0057] This embodiment provides a method for machining micropores in a gas distribution plate. The machining method includes the following steps:

[0058] (1) Perform rough turning and finish turning on 6061 aluminum alloy with a diameter of 510 mm in sequence to form a preliminary processed product of the gas distribution plate;

[0059] The spindle speed of the rough turning is 2000 r / min, the depth of cut is 0.6 mm, and the feed rate is 0.8 mm / r; the spindle speed of the finish turning is 2000 r / min, the depth of cut is 0.03 mm, and the feed rate is 0.09 mm / r;

[0060] (2) Use a step drill to drill the surface of the preliminary processed product of the gas distribution plate, and then perform physical polishing, ethanol cleaning, chemical polishing, and water washing in sequence to obtain a number of second-order combined holes;

[0061] The spindle speed of the drilling process is 18000 r / min and the feed rate is 0.02 mm / r;

[0062] The surface of the gas distribution plate is physically polished to a roughness of 0.3 μm;

[0063] The chemical polishing includes pickling with a mixed acid of phosphoric acid and sulfuric acid for 80 s. The mass concentration of the phosphoric acid is 50 wt%, and the mass concentration of the sulfuric acid is 35 wt%.

[0064] A number of second-order combined holes obtained in this embodiment are evenly distributed in a diffusion manner from the center of the gas distribution plate to the outside. The density of the second-order combined holes on the gas distribution plate is 43 pieces / cm 2 ; The obtained second-order combined holes include a first-order hole and a second-order hole that are sequentially connected and coaxial in the direction from the upper end surface to the lower end surface of the gas distribution plate; the aperture of the first-order hole is 1.16 mm and the depth is 11.8 mm; the aperture of the second-order hole is 0.68 mm and the depth is 3.1 mm.

[0065] In this embodiment, the hole shapes, hole sizes and heights of several second-order combined holes on the gas distribution plate are consistent, and the position distribution of the holes is uniform.

[0066] Embodiment 3

[0067] This embodiment provides a processing method for micro holes in a gas distribution plate. The processing method includes the following steps:

[0068] (1) Rough turning and finish turning are successively performed on 6061 aluminum alloy with a diameter of 530 mm to form a preliminary processed product of the gas distribution plate;

[0069] The spindle speed of the rough turning is 5000 r / min, the depth of cut is 0.8 mm, and the feed rate is 0.3 mm / r; the spindle speed of the finish turning is 4000 r / min, the depth of cut is 0.15 mm, and the feed rate is 0.02 mm / r;

[0070] (2) Drilling treatment is performed on the surface of the preliminary processed product of the gas distribution plate by using a step drill, and then physical polishing, ethanol cleaning, chemical polishing and water washing are successively performed to obtain several second-order combined holes;

[0071] The spindle speed of the drilling treatment is 11000 r / min, and the feed rate is 0.09 mm / r;

[0072] The surface roughness of the gas distribution plate after physical polishing is 0.25 μm;

[0073] The chemical polishing includes pickling with a mixed acid of phosphoric acid and sulfuric acid for 60 s. The mass concentration of the phosphoric acid is 50 wt%, and the mass concentration of the sulfuric acid is 35 wt%.

[0074] A number of second-order combined holes obtained in this embodiment are evenly diffusely distributed outward from the center of the gas distribution plate. The density of the second-order combined holes on the gas distribution plate is 43 pieces / cm 2 ; The obtained second-order combined holes include a first-order hole and a second-order hole that are connected in sequence and coaxially along the direction from the upper end face to the lower end face of the gas distribution plate; the aperture of the first-order hole is 1.16 mm and the depth is 12.1 mm; the aperture of the second-order hole is 0.68 mm and the depth is 3.0 mm.

[0075] In this embodiment, the hole shapes, hole sizes and heights of several second-order combined holes on the gas distribution plate are consistent, and the position distribution of the holes is uniform.

[0076] Embodiment 4

[0077] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the depth of cut for rough turning in step (1) is 0.2 mm, other conditions are the same as those in Embodiment 1.

[0078] In this embodiment, when the depth of cut for rough turning is too low, it affects the flatness and parallelism of the surface of the preliminary processed product of the gas distribution plate, resulting in a decrease in machining accuracy during the subsequent drilling process, and it cannot ensure that the aperture sizes and heights of several second-order combined holes are consistent, thus failing to meet the requirements for semiconductor use.

[0079] Embodiment 5

[0080] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the depth of cut for rough turning in step (1) is 1.2 mm, other conditions are the same as those in Embodiment 1.

[0081] In this embodiment, when the depth of cut for rough turning is too high, the surface of the preliminary processed product of the gas distribution plate is uneven and the parallelism is also poor, resulting in a decrease in machining accuracy during the subsequent drilling process, and it cannot ensure that the aperture sizes and heights of several second-order combined holes are consistent, thus failing to meet the requirements for semiconductor use.

[0082] Embodiment 6

[0083] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the depth of cut for finish turning in step (1) is 0.5 mm, other conditions are the same as those in Embodiment 1.

[0084] In this embodiment, when the depth of cut for finish turning is too high, although the cutting force and vibration are much smaller compared to rough turning, it will also affect the flatness and parallelism of the surface of the preliminary processed product of the gas distribution plate, resulting in a decrease in machining accuracy during the subsequent drilling process, and it cannot ensure that the aperture sizes and heights of several second-order combined holes are consistent, thus failing to meet the requirements for semiconductor use.

[0085] Embodiment 7

[0086] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the spindle speed for drilling in step (2) is 8000 r / min, other conditions are the same as those in Embodiment 1.

[0087] In this embodiment, when the spindle speed for drilling is too low, there is a large vibration generated by the step drill during the drilling process, which affects the drilling accuracy, resulting in inconsistent aperture sizes, positions, and heights of several second-order combined holes, thus failing to meet the requirements for semiconductor use.

[0088] Embodiment 8

[0089] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the spindle speed for drilling in step (2) is 25,000 r / min, other conditions are the same as those in Embodiment 1.

[0090] In this embodiment, when the spindle speed for drilling is too high, the step drill bit will cut too violently during drilling, resulting in an increase in the surface roughness of the inner walls of several second-order combined holes and inconsistent hole diameter sizes, thus failing to meet the requirements for semiconductor use.

[0091] Embodiment 9

[0092] This embodiment provides a method for machining micro-holes in a gas distribution plate. Except that the feed rate for drilling in step (2) is 0.3 mm / r, other conditions are the same as those in Embodiment 1.

[0093] In this embodiment, when the feed rate for drilling is too high, the cutting speed of the step drill bit increases during drilling, resulting in inconsistent hole diameter sizes, positions, and heights of several second-order combined holes, thus failing to meet the requirements for semiconductor use.

[0094] Comparative Example 1

[0095] This comparative example provides a method for machining micro-holes in a gas distribution plate. Except that rough turning is not performed in step (1), other conditions are the same as those in Embodiment 1.

[0096] In this comparative example, due to the absence of rough turning treatment, the flatness and parallelism of the surface of the gas distribution plate's semi-finished product are poor, resulting in a decrease in machining accuracy during subsequent drilling, and it cannot ensure that the hole diameter sizes and heights of several second-order combined holes remain consistent, thus failing to meet the requirements for semiconductor use.

[0097] Comparative Example 2

[0098] This comparative example provides a method for machining micro-holes in a gas distribution plate. Except that finish turning is not performed in step (1), other conditions are the same as those in Embodiment 1.

[0099] In this comparative example, due to the absence of finish turning treatment, the flatness of the surface of the gas distribution plate's semi-finished product is poor, resulting in a decrease in machining accuracy during subsequent drilling, and it cannot ensure that the hole diameter sizes and heights of several second-order combined holes remain consistent, thus failing to meet the requirements for semiconductor use.

[0100] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for machining micropores in a gas distribution plate, characterized in that, The processing method includes the following steps: (1) Rough turning and finish turning the raw blank in sequence to form a preliminary processed product of the gas distribution plate; (2) Drilling the surface of the preliminary processed product of the gas distribution plate to obtain a number of second-order combined holes.

2. The processing method according to claim 1, wherein The material of the raw blank in step (1) includes 6061 aluminum alloy; Preferably, the diameter of the raw blank in step (1) is 500 - 600 mm.

3. The processing method according to claim 1 or 2, characterized in that, The spindle speed of the rough turning in step (1) is 2000 - 6000 r / min; Preferably, the depth of cut of the rough turning in step (1) is 0.5 - 1 mm; Preferably, the feed rate of the rough turning in step (1) is 0.3 - 1 mm / r.

4. The processing method according to any one of claims 1 to 3, characterized in that The spindle speed of the finish turning in step (1) is 2000 - 6000 r / min; Preferably, the depth of cut of the finish turning in step (1) is 0.01 - 0.2 mm; Preferably, the feed rate of the finish turning in step (1) is 0.01 - 0.1 mm / r.

5. The processing method according to any one of claims 1-4, characterized in that, The drilling in step (2) is carried out by using a step drill.

6. The processing method according to any one of claims 1-5, characterized in that The spindle speed of the drilling in step (2) is 10000 - 20000 r / min; Preferably, the feed rate of the drilling in step (2) is 0.01 - 0.1 mm / r.

7. The processing method according to any one of claims 1-6, characterized in that, After the drilling in step (2), physical polishing, alcohol washing, chemical polishing and water washing are carried out in sequence; Preferably, the surface roughness of the gas distribution plate after physical polishing is 0.1 - 0.4 μm; Preferably, the chemical polishing is carried out by acid solution immersion for 30 - 120 s; Preferably, the acid solution includes any one or a combination of at least two of phosphoric acid, nitric acid or nitrous acid.

8. The processing method according to any one of claims 1-7, characterized in that, In step (2), a number of the second-order combined holes are evenly distributed diffusely outward from the center of the gas distribution plate; Preferably, the density of the second-order combined holes on the gas distribution plate is 38-43 holes / cm 2 .

9. The processing method according to any one of claims 1-8, characterized in that The second-order combined holes in step (2) include a first-order hole and a second-order hole which are connected in sequence along the direction from the upper end face to the lower end face of the gas distribution plate.

10. The processing method according to claim 9, wherein, The aperture of the first-order hole is 1.15 - 1.2 mm; Preferably, the aperture of the second-order hole is 0.68 - 0.72 mm; Preferably, the depth of the first-order hole ≥ the depth of the second-order hole; Preferably, the first-order hole and the second-order hole are coaxially arranged.

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