An acid pickling treatment method for preparing a plasma-etching-resistant passivation film on the surface of an aluminum alloy

Abstract

This invention proposes an acid pickling method for preparing a plasma-etch-resistant passivation film on the surface of aluminum alloy. The method includes: ultrasonically cleaning the sample in an anhydrous ethanol solution and drying it; setting the acid pickling process into four steps, with the mass fraction of diluted nitric acid as the target variable. The first step's pickling solution contains 595-638 ml / L of phosphoric acid, 147-196 ml / L of sulfuric acid, and 25-55 ml / L of nitric acid, with the remainder being water; the second step's pickling solution contains 441-490 ml / L of sulfuric acid and 123- The first step uses 275 ml / L nitric acid, with the remainder being water; the second step uses 595-638 ml / L phosphoric acid and 245-294 ml / L sulfuric acid, with the remainder being water; the third step uses 245-550 ml / L nitric acid, with the remainder being water; the first step uses a constant temperature water bath heated to 90-110℃, and the sample is placed in the solution and agitated to clean it. The sample is then placed in the solutions of the second, third, and fourth steps and agitated to clean it at 18-20℃. The acid solution on the sample surface is then rinsed with deionized water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor etching machine parts, and particularly relates to a method for preparing a plasma etching passivation film on an aluminum alloy surface through pickling. BACKGROUND

[0002] With the rapid development of the semiconductor industry, miniaturized chips have become an indispensable trend, which promotes the application of plasma etching technology in semiconductor devices. In the etching machine, the cavity material plays a crucial role in the normal operation of the machine. During the etching process of semiconductor devices, mixed gas forms high-energy and active plasma through ionization; these plasmas not only etch semiconductor devices, but also corrode the cavity components of the plasma etching machine made of aluminum or aluminum alloy, which not only reduces the etching rate of the plasma on the semiconductor device, but also shortens the service life of the etching machine. On the other hand, the corrosion product particles formed after the etching of the cavity components fall on the surface of the semiconductor device, causing pollution and affecting the production quality and efficiency of the product. Currently, the preparation of a plasma etching-resistant layer on the surface of the internal parts of the etching machine can effectively slow down the corrosion.

[0003] The early method for preparing a plasma etching-resistant coating is to form aluminum oxide on the surface of aluminum through anodic oxidation, but microcracks and pores are easily generated during the preparation process, resulting in poor plasma etching resistance during service (Hot Spraying Technology, 2014, 6(03): 19-23). In addition, Wushanghua, Tan Yicheng, etc. prepared aluminum oxide ceramic from nano-aluminum oxide powder through high-temperature sintering (China, 201610513880.1[P]. 2019-03-12). Chen Xiaolong, Zhao Hongxu, etc. sprayed micro-nano ultrafine yttrium oxide powder on the surface of aluminum alloy to prepare a yttrium oxide coating through a suspension plasma spraying process (China, 202010796943.5[P]. 2020-12-11). The coating prepared through high-temperature sintering or spraying processes will have defects such as pores and microcracks, and the thermal expansion coefficient of the metal inorganic coating does not match that of the substrate material, which is prone to coating peeling in the plasma working environment, causing pollution to the semiconductor devices in the etching equipment. In addition, the complexity of the preparation process greatly increases the production time and cost.

[0004] In the existing pickling technology, CN104611711A "pickling solution and pickling method of high-alloy corrosion-resistant steel" puts the sample into a pickling solution composed of hydrochloric acid, sulfuric acid, phosphoric acid, corrosion inhibitor, surfactant, solution stabilizer and water for 30-40 min, rinses after pickling, then performs nitric acid passivation, and then performs water washing after passivation, and then immerses in NaOH or Na2CO3 solution. The problems of this method are that the sample pickling time is too long, and further water washing, passivation and water washing immersion and other series of complicated operations are required after pickling.

[0005] The existing technology CN102965675A "stainless steel pickling and passivation method" designs a pickling and passivation solution with a ratio of 20% nitric acid + 10% hydrofluoric acid + 70% pure water. The invention combines the original pickling and passivation steps into one, and the whole pickling and passivation process can be summarized as oil removal-rinse-pickling and passivation-second rinse-alkali neutralization-water washing-third rinse-air drying-drying-sealing-natural air drying-packaging. The process of the invention is simple, low in cost and low in operation intensity, but the whole process is relatively long and time-consuming, which is not conducive to industrial production. SUMMARY

[0006] The purpose of the application is to solve the above technical problems, and the application provides a pickling treatment method for preparing a plasma etching resistant passivation film on the surface of an aluminum alloy.

[0007] Technical scheme: To achieve the above purpose, the application provides a pickling treatment method for preparing a plasma etching resistant passivation film on the surface of an aluminum alloy, which comprises the following steps:

[0008] (1) The aluminum alloy substrate is processed into a sample with a predetermined shape by wire cutting, and then the aluminum alloy is ultrasonically cleaned with anhydrous ethanol and dried by blowing;

[0009] (2) Preparing the pickling solution: dilute nitric acid with water, then mix with phosphoric acid, pour sulfuric acid into the above solution and stir, set up four processes for the pickling process, and mix the pickling solution of each process according to certain combinations;

[0010] (3) Put the aluminum alloy into four processes with different temperatures in turn for swing cleaning, then clean the aluminum alloy surface with deionized water and dry, and finally vacuum preservation.

[0011] Preferably, in the step (2), the mass fraction of the diluted nitric acid is 20%-40%.

[0012] In the step (2), preferably, the combination of the four-process pickling solution is as follows: the first process contains 595-638 ml / L of phosphoric acid, 147-196 ml / L of sulfuric acid and 25-55 ml / L of nitric acid, and the rest is water; the second process contains 441-490 ml / L of sulfuric acid and 123-275 ml / L of nitric acid, and the rest is water; the third process contains 595-638 ml / L of phosphoric acid and 245-294 ml / L of sulfuric acid, and the rest is water; and the fourth process contains 245-550 ml / L of nitric acid, and the rest is water, wherein the mass fraction of nitric acid used in the first process, the second process and the fourth process is the same.

[0013] In the step (3), preferably, the temperature of the four processes is as follows: the first process is heated to 90-110°C by using a constant temperature water bath, and the second, third and fourth processes are 18-20°C.

[0014] In the step (3), preferably, the time of swing cleaning in the four processes is as follows: the first process is 40-60 s, and the second, third and fourth processes are 10-15 s.

[0015] Beneficial effects: Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0016] (1) The pickling and passivation treatment of the present application is simple to operate, low in cost and conducive to large-scale commercial production.

[0017] (2) The Al2O3 and AlN composite passivation film prepared by the present application is prepared by using a four-process pickling process, which is short in time, fast in speed and excellent in comprehensive performance.

[0018] (3) The Al2O3 and AlN composite passivation film obtained by the present application can effectively slow down the erosion of plasma, reduce the maintenance and replacement of etching machine cavity materials, thereby prolonging the service life of the plasma etching machine.

[0019] (4) The present application provides a pickling treatment method which is simple to operate, fast in speed and low in cost, and successfully prepares Al2O3 and AlN composite passivation film on the surface of aluminum alloy, has strong adhesion to the substrate, and can effectively protect the aluminum alloy parts working in the plasma environment, and has good application prospect.

[0020] Drawings of the specification

[0021] Figure 1 Figure 2 is a SEM image of the passivation film on the surface of the aluminum alloy after 20% nitric acid pickling treatment, and the magnification of (a-c) is 500x, 5kx and 10kx, respectively.

[0022] Figure 2SEM images of the passivation film on the surface of aluminum alloy after pickling with 30% nitric acid, with magnifications of 500x, 5,000x, and 10,000x respectively.

[0023] Figure 3 SEM images of the passivation film on the surface of aluminum alloy after pickling with 40% nitric acid, with magnifications of 500x, 5000x, and 10000x respectively.

[0024] Figure 4 XPS spectra of the passivation film on the surface of aluminum alloy after pickling with 20% nitric acid are shown. (ad) represents the full spectrum, Al2p, N 1s, and O 1s fine spectrum, respectively.

[0025] Figure 5 XPS spectra of the passivation film on the surface of aluminum alloy after pickling with 30% nitric acid are shown. (ad) represents the full spectrum, Al2p, N 1s, and O 1s fine spectrum, respectively.

[0026] Figure 6 XPS spectra of the passivation film on the surface of aluminum alloy after pickling with 40% nitric acid are shown. (ad) represents the full spectrum, Al2p, N 1s, and O 1s fine spectrum, respectively.

[0027] Figure 7 The XRD pattern of the passivation film on the surface of the aluminum alloy after pickling treatment;

[0028] Figure 8 This is a flowchart of the method of the present invention. Detailed Implementation

[0029] Example 1: An acid pickling method for preparing a plasma-etch-resistant passivation film on an aluminum alloy surface, comprising the following steps:

[0030] (1) Surface pretreatment of aluminum alloy: The aluminum alloy substrate is processed into a sample of 20mm×20mm×3mm by wire cutting, and then the aluminum alloy is ultrasonically cleaned in anhydrous ethanol solution and dried.

[0031] (2) Prepare nitric acid with a mass fraction of 20% and set up an acid washing process into four steps. The first step is 638 mL / L of phosphoric acid, 196 mL / L of sulfuric acid, and 25 mL / L of nitric acid, with the remainder being water. The second step is 490 mL / L of sulfuric acid and 123 mL / L of nitric acid, with the remainder being water. The third step is 638 mL / L of phosphoric acid and 294 mL / L of sulfuric acid, with the remainder being water. The fourth step is 245 mL / L of nitric acid, with the remainder being water. The mass fraction of nitric acid used in the first, second, and fourth steps is the same.

[0032] (3) The specific pickling and passivation process is carried out according to the following steps: According to the pickling solution composition of each process, a certain amount of pickling solution is measured and placed into a beaker; the sample is placed into the solutions of the first, second, third and fourth processes for cleaning in sequence; finally, the sample is placed in deionized water to clean the surface acid solution. Among them, the solution of the first process is heated to 95°C in a constant temperature water bath, and the sample is placed in the solution and swung for 50s. The solutions of the second, third and fourth processes are swung for 12s at 18°C.

[0033] Table 1 shows the test results. After being pickled with 20% nitric acid, the contact angle is 66.20° and it does not have hydrophobicity. The EDS surface scan O / Al ratio is 0.02, the elastic modulus (Er) and hardness (H) are 115.06 GPa and 3.25 GPa, respectively, and the surface roughness is 0.59 μm. Figure 1 (a) At 500x magnification, it can be seen that after pickling with 20% nitric acid, the surface of the aluminum alloy is uneven. At 5000x magnification... Figure 1 (b) and 10,000 times ( Figure 1 (c) Uneven pits were observed. XPS full spectrum ( Figure 4 (a) The results show that the passivation film on the aluminum alloy surface contains N, O, Al, C, and Cu elements, with Al 2p ( Figure 4 (b)), N 1s( Figure 4 (c)), O 1s( Figure 4 (d) Fine spectroscopy shows that Al on the sample surface is bonded by Al-Al, Al-N, and Al-O bonds, N is bonded by Al-N bonds, and O is bonded by Al-O bonds. XRD( Figure 7 The results show that the AlN phase on the surface of the aluminum alloy sample has a preferred orientation in the (200) plane.

[0034] Example 2: An acid pickling method for preparing a plasma-resistant passivation film on an aluminum alloy surface, comprising the following steps:

[0035] (1) Surface pretreatment of aluminum alloy: The aluminum alloy substrate is processed into a sample of 20mm×20mm×3mm by wire cutting, and then the aluminum alloy is ultrasonically cleaned in anhydrous ethanol solution and dried.

[0036] (2) Prepare a nitric acid solution with a mass fraction of 30%, and set up an acid washing process into four steps. The first step is 638 mL / L of phosphoric acid, 196 mL / L of sulfuric acid, 39 mL / L of nitric acid, and the remainder is water; the second step is 490 mL / L of sulfuric acid, 195 mL / L of nitric acid, and the remainder is water; the third step is 638 mL / L of phosphoric acid, 294 mL / L of sulfuric acid, and the remainder is water; the fourth step is 390 mL / L of nitric acid, and the remainder is water.

[0037] (3) The specific pickling and passivation process is carried out according to the following steps: According to the pickling solution composition of each process, a certain amount of pickling solution is measured and placed into a beaker; the sample is placed into the solutions of the first, second, third and fourth processes for cleaning in sequence; the sample is placed in deionized water to clean the surface acid solution. Among them, the solution of the first process is heated to 95°C in a constant temperature water bath, and the sample is placed in the solution and swung for 50s. The solutions of the second, third and fourth processes are swung for 12s at 18°C.

[0038] As can be seen from the test data in Table 1, after slightly increasing the concentration of nitric acid, the elastic modulus (Er) and hardness (H) of the passivation film on the aluminum alloy surface increased to 132.21 GPa and 4.52 GPa, respectively, but the roughness decreased to 0.50 μm and the contact angle decreased to 58.30°. The EDS surface scan O / Al test results were similar to those of the 20% nitric acid pickling test, indicating that the difference in Al2O3 content between the two concentrations of aluminum alloy samples was small. Figure 2 (a) The microstructure of the passivation film surface shows that after pickling with 30% nitric acid, the aluminum alloy surface is uneven and has a small number of pores, and its surface density decreases. After magnification, ( Figure 2 (b) 5,000 times Figure 2 (c) 10,000x) The holes are jagged. XPS full spectrum ( Figure 5 (a) The results show that the passivation film on the aluminum alloy surface is mainly composed of N, O, Al, C, P, S, Mn, and Fe elements, with Al2p ( Figure 5 (b)), N 1s( Figure 5 (c)), O 1s( Figure 5 (d) On the surface of the fine-spectrum sample, Al is bonded in the form of Al-Al, Al-N, and Al-O bonds, N is bonded in the form of Al-N bonds, and O is bonded in the form of Al-O bonds. XRD ( Figure 7 The results show that, compared with aluminum alloys pickled with 20% nitric acid, the AlN phase on the surface of the aluminum alloy sample after pickling with 30% nitric acid has a higher diffraction peak intensity in the (111) and (220) planes.

[0039] Example 3: An acid pickling method for preparing a plasma-etch-resistant passivation film on an aluminum alloy surface, comprising the following steps:

[0040] (1) Surface pretreatment of aluminum alloy: The aluminum alloy substrate is processed into a sample of 20mm×20mm×3mm by wire cutting, and then the aluminum alloy is ultrasonically cleaned in anhydrous ethanol solution and dried.

[0041] (2) Prepare nitric acid with a mass fraction of 40% and set up an acid washing process into four steps. The first step is 638 mL / L of phosphoric acid, 196 mL / L of sulfuric acid, and 55 mL / L of nitric acid, with the remainder being water; the second step is 490 mL / L of sulfuric acid and 275 mL / L of nitric acid, with the remainder being water; the third step is 638 mL / L of phosphoric acid and 294 mL / L of sulfuric acid, with the remainder being water; and the fourth step is 550 mL / L of nitric acid, with the remainder being water.

[0042] (3) The specific pickling and passivation process is carried out according to the following steps: According to the pickling solution composition of each process, a certain amount of pickling solution is measured and placed into a beaker; the sample is placed into the solutions of the first, second, third and fourth processes for cleaning in sequence; finally, the sample is placed in deionized water to clean the surface acid solution. Among them, the solution of the first process is heated to 95°C in a constant temperature water bath, and the sample is placed in the solution and swung for 50s. Then, the solutions of the second, third and fourth processes are swung for 12s at 18°C.

[0043] As shown in Table 1, after pickling with 40% nitric acid, the surface roughness of the aluminum alloy reached its maximum value of 1.04 μm, and the contact angle also increased to 88.20°. Furthermore, EDS surface scanning results showed that the O / Al ratio increased to 0.03, indicating an increase in the Al2O3 content in the passivation film on the aluminum alloy surface. Compared to the aluminum alloy pickled with 30% nitric acid, when the nitric acid mass fraction was 40%, the elastic modulus (Er) and hardness (H) of the passivation film on the aluminum alloy surface decreased slightly to 125.27 GPa and 3.65 GPa, respectively. Figure 3 As shown in (a), after pickling with 40% nitric acid, the surface of the aluminum alloy became uneven and a small number of holes appeared. At a magnification of 5,000 times... Figure 3 (b) and 10,000 times ( Figure 3 (c) It was observed that some pores were embedded with a passivation film. XPS full spectrum ( Figure 6 (a) The results show that the passivation film on the aluminum alloy surface is mainly composed of N, O, Al, C, P, Mg, and Zn elements, with Al 2p ( Figure 6 (b)), N 1s( Figure 6 (c)), O 1s( Figure 6 (d) Fine-spectrum sample surface: On the sample surface, Al is bonded in the form of Al-Al, Al-N, and Al-O bonds; N is bonded in the form of Al-N bonds; and O is bonded in the form of Al-O bonds. XRD results ( Figure 7 The surface of the aluminum alloy sample contains AlN phase. Compared with the other two nitric acid concentrations, the diffraction peak intensity of AlN phase on the (311) plane is higher after being pickled with 40% nitric acid.

[0044] Table 1 Characterization test data of passivation film on aluminum alloy surface after pickling treatment

[0045]

Claims

1. A pickling treatment method for preparing a plasma-etch-resistant passivation film on an aluminum alloy surface, characterized in that, The method includes the following steps: (1) The aluminum alloy substrate is processed into a sample of a preset shape by wire cutting, the aluminum alloy is ultrasonically cleaned with anhydrous ethanol, and then dried. (2) Preparation of pickling solution: dilute nitric acid with water, then add phosphoric acid and mix. Pour sulfuric acid into the above solution and stir. Set up a pickling process into four steps. Mix the pickling solution of each step according to a certain combination. (3) The aluminum alloy is placed in four processes at different temperatures for oscillating cleaning, the pickling solution on the surface of the aluminum alloy is cleaned with deionized water and dried, and then vacuum stored. In step (2), the pickling solution for the four processes is as follows: the pickling solution for the first process contains 595-638 ml / L of phosphoric acid, 147-196 ml / L of sulfuric acid, and 25-55 ml / L of nitric acid, with the remainder being water; the pickling solution for the second process contains 441-490 ml / L of sulfuric acid and 123-275 ml / L of nitric acid, with the remainder being water; the pickling solution for the third process contains 595-638 ml / L of phosphoric acid and 245-294 ml / L of sulfuric acid, with the remainder being water; and the pickling solution for the fourth process contains 245-550 ml / L of nitric acid, with the remainder being water. The nitric acid used in the first, second, and fourth processes has the same mass fraction. In step (3), the temperatures of the four processes are as follows: the first process is heated to 90-110℃ using a constant temperature water bath, and the second, third and fourth processes are heated to 18-20℃.

2. The pickling treatment method for preparing a plasma-etch-resistant passivation film on an aluminum alloy surface according to claim 1, characterized in that, In step (2), the mass fraction of the diluted nitric acid is 20%-40%.

3. The pickling treatment method for preparing a plasma-etch-resistant passivation film on an aluminum alloy surface according to claim 1 or 2, characterized in that, In step (3), the time for the four-step oscillating cleaning process is as follows: the first step is 40-60 seconds, and the second, third and fourth steps are 10-15 seconds.

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