Wafer zinc displacement plating solution and process thereof

Abstract

The application discloses a wafer zinc displacement plating solution and a process thereof, and comprises the following component mass concentrations: zinc salt 5-15 g / L, sodium hydroxide 50-150 g / L, uniforming agent 10-20 g / L, composite complexing agent 40-80 g / L, stabilizing agent 0.5-1 g / L, wetting agent 1-2 g / L, and the rest is deionized water. The application can be applied to wafer nickel plating pretreatment process, and a layer of zinc is displaced by realizing displacement with an aluminum base material, thereby being favorable for wafer nickel. The zinc displacement plating solution provided by the application not only has a high plating layer flatness and compactness, but also has excellent plating solution stability.

Description

Technical Field

[0001] This invention relates to the field of chemical plating technology, and more particularly to a wafer zinc displacement plating solution and its process. Background Technology

[0002] Currently, zinc-displacement immersion solutions used in the pretreatment of wafer surface treatments exhibit relatively stable performance, but the coating density is not ideal. Some zinc-displacement solutions also suffer from similar problems, and some have poor stability. Furthermore, as the aluminum ion concentration increases, it contaminates the zinc displacement process, ultimately reducing its effectiveness. For example, patent CN106987830B discloses a zinc immersion solution comprising 30-50 g / L zinc sulfate, 20-50 g / L nickel sulfate, 10-30 g / L ammonium acetate, and 10-30 g / L DTPMP. This formulation results in a zinc immersion solution with poor stability; precipitation occurs with increasing aluminum ion concentration, and the zinc coating speed is slow. Additionally, CN101831641A discloses a magnesium-lithium alloy acidic zinc immersion solution using zinc chloride as the zinc salt. However, chloride ions are aggressive towards equipment and easily cause corrosion, making it unsuitable for the high-end market. Therefore, this application aims to solve the problem of zinc ion stability, reduce the impact of aluminum ions on zinc plating, and improve the smoothness of the zinc coating, so as to better achieve nickel-palladium-gold surface treatment.

[0003] To address the above issues and achieve independent development of nickel-palladium-gold surface treatment technology for chips, this application provides a wafer zinc replacement plating solution and its process. Summary of the Invention

[0004] To address the shortcomings of the aforementioned technologies, this invention provides a wafer zinc replacement plating solution and its process. This invention can be applied to the wafer nickel plating pretreatment process. By replacing a layer of zinc with an aluminum substrate, it facilitates nickel plating on the wafer. The zinc replacement plating solution provided by this invention not only produces a smooth and dense plating layer, but also exhibits excellent stability.

[0005] To achieve the above objectives, the present invention provides a wafer zinc replacement plating solution, comprising the following components in mass concentrations: zinc salt 5-15 g / L, sodium hydroxide 50-150 g / L, homogenizer 10-20 g / L, complexing agent 40-80 g / L, stabilizer 0.5-1 g / L, wetting agent 1-2 g / L, with the balance being deionized water;

[0006] Operating temperature 25-35℃

[0007] The zinc salt is zinc oxide, and the particle size of the zinc oxide powder is 50-150 nm. Since large size will lead to agglomeration, thereby reducing the stability of the plating solution, this application adopts a particle size at the nanometer level, which can improve the stability of the solution.

[0008] The homogenizer is o-dithiopyridine-PEG-o-dithiopyridine, which can refine the grains, increase the smoothness of the zinc layer, and improve the subsequent nickel plating effect, resulting in a finer zinc coating compared to the zinc replacement plating solution obtained by existing Shangcun.

[0009] The composite complexing agent is a combination of maleic acid and tetrasodium iminodisuccinate, with a mass concentration ratio of 1:1 during use. The composite complexing agent can improve the stability of the plating solution and prevent precipitation. Since zinc will form zinc hydroxide precipitate under high concentration alkaline conditions, a complexing agent is necessary to improve stability. However, the complexing effect of the complexing agents on the market is not obvious. Some flocculent precipitates will still precipitate after a week. In contrast, the stability effect of this application can last up to one month.

[0010] The stabilizer is aminopyrazine, which can solve the problem of uneven zinc coating caused by the replaced aluminum ions, resulting in whitening of the coating.

[0011] The wetting agent is 8-aminooctanoic acid, which plays an auxiliary role in ensuring the uniformity of the coating.

[0012] The concentration ratio of the composite complexing agent to the homogenizing agent during use is 4:1. The optimal ratio of the complexing agent to the homogenizing agent during use is 4:1. If the ratio is too high or too low, it will lead to uneven control over the growth of zinc particles and uneven coating thickness.

[0013] The concentration ratio of stabilizer to wetting agent during use is 1:2. The stabilizer mainly addresses the impact of aluminum ion plating solution and coating quality, while the wetting agent plays an auxiliary role in coating uniformity. Experiments have shown that excessively high or low stabilizer concentrations can also lead to poor uniformity.

[0014] One wafer replacement plating process includes the following specific steps:

[0015] A. Alkaline micro-etching: The aluminum oxide film is removed by alkaline micro-etching, and the aluminum substrate is micro-roughened, followed by washing with pure water.

[0016] B. Degreasing: Remove easily adsorbed grease, alkaline micro-etching agent residues and other impurities from the surface, and then rinse with pure water.

[0017] C. Zinc plating: This involves one alkaline zinc replacement for 30-60 seconds, one zinc stripping with 30% volume concentration nitric acid for 10-15 seconds, and another alkaline zinc replacement for 60-120 seconds. After that, the product is placed in a nickel plating bath for nickel plating. Each replacement and zinc stripping process requires rinsing with pure water. All steps are performed at room temperature.

[0018] The specific conditions for step A are as follows: the alkaline micro-etching solution consists of 1-5 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 1-5 g / L p-nitrobenzoic acid, and 0.1-0.5 g / L o-dithiopyridine-PEG-o-dithiopyridine. The operating temperature is 25-35℃, and the time is 1-2 min. The roughness difference of this alkaline micro-etching solution does not exceed 0.2 micrometers, which can greatly improve the smoothness. Compared with commercial micro-etching agents, the smoothness is improved by 30%.

[0019] The specific conditions for step B are as follows: the degreasing agent consists of 0.01-0.05 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 0.2-0.5 g / L ethylene oxide and propylene oxide block copolymer, 10-30 ppm / LOP-10, 0.5-1.5 ml / L 1,4-dioxane, and 30-60 ppm / L sodium dodecylbenzenesulfonate. The operating temperature is 45-55℃, and the time is 1-2 minutes. This degreasing agent can clean micro-etching agent residues and dust adsorbents, improve cleanliness, and has a slight etching effect on the coating. Under the action of surfactants, it can play an auxiliary role in improving smoothness.

[0020] The beneficial effects of this invention are as follows: Compared with the prior art, the wafer zinc replacement plating process provided by this invention has the following advantages:

[0021] 1) The zinc replacement solution provided by this invention uses o-dithiopyridine-PEG-o-dithiopyridine as a homogenizer. This homogenizer can refine the grains, increase the smoothness of the zinc layer, and improve the subsequent nickel plating effect. Compared with the zinc replacement plating solution of existing Shangcun, the zinc plating layer is finer.

[0022] 2) The zinc replacement plating solution provided by this invention uses a composite complexing agent composed of maleic acid and tetrasodium iminosuccinate, with a mass concentration ratio of 1:1 during use. The composite complexing agent can improve the stability of the plating solution and prevent precipitation. Since zinc will generate zinc hydroxide precipitate under high-concentration alkaline conditions, a complexing agent is necessary to improve stability. However, the complexing effect of the complexing agents currently on the market is not obvious, and some flocculent precipitates will still precipitate after a week. In contrast, the stability effect of this application can last up to one month.

[0023] 3) The zinc replacement plating solution provided by the present invention uses aminopyrazine as a stabilizer. The stabilizer can solve the problem of uneven zinc coating caused by the replaced aluminum ions, which leads to whitening of the coating.

[0024] 4) In this invention, the concentration ratio of the complexing agent to the homogenizing agent is 4:1. This ratio is optimal; ratios that are too high or too low will result in uneven control over zinc particle growth and uneven coating thickness. The ratio of the stabilizer to the wetting agent is 1:2. The stabilizer primarily addresses the impact of the aluminum ion plating solution and the coating quality, while the wetting agent plays an auxiliary role in coating uniformity. Experiments have shown that excessively high or low stabilizer concentrations can also lead to poor uniformity. Attached Figure Description

[0025] Figure 1 The figures show the experimental test results of the zinc replacement examples and comparative examples in this invention. Detailed Implementation

[0026] To more clearly illustrate the present invention, the invention will be further described below with reference to the text and accompanying drawings.

[0027] To achieve the above objectives, the present invention addresses the shortcomings of the aforementioned technologies by providing a wafer zinc replacement plating solution comprising the following components at the following mass concentrations: zinc salt 5-15 g / L, sodium hydroxide 50-150 g / L, homogenizer 10-20 g / L, complexing agent 40-80 g / L, stabilizer 0.5-1 g / L, wetting agent 1-2 g / L, with the balance being deionized water.

[0028] Operating temperature 25-35℃

[0029] The zinc salt is zinc oxide, and the particle size of the zinc oxide powder is 50-150 nm.

[0030] The homogenizer is o-dithiopyridine-PEG-o-dithiopyridine.

[0031] In this embodiment, the composite complexing agent is a composition of maleic acid and tetrasodium iminodisuccinate, with a mass concentration ratio of 1:1 during use.

[0032] In this embodiment, the stabilizer is aminopyrazine.

[0033] In this embodiment, the wetting agent is 8-aminooctanoic acid.

[0034] In this embodiment, the concentration ratio of the complexing agent to the homogenizing agent during use is 4:1.

[0035] In this embodiment, the concentration ratio of the stabilizer to the wetting agent during use is 1:2.

[0036] In this embodiment, a wafer replacement plating process includes the following specific steps:

[0037] A. Alkaline micro-etching: The aluminum oxide film is removed by alkaline micro-etching, and the aluminum substrate is micro-roughened, followed by washing with pure water.

[0038] B. Degreasing: Remove easily adsorbed grease, alkaline micro-etching agent residues and other impurities from the surface, and then rinse with pure water.

[0039] C. Zinc plating: This involves one alkaline zinc replacement for 30-60 seconds, one zinc stripping with 30% volume concentration nitric acid for 10-15 seconds, and another alkaline zinc replacement for 60-120 seconds. After that, the product is placed in a nickel plating bath for nickel plating. Each replacement and zinc stripping process requires rinsing with pure water. All steps are performed at room temperature.

[0040] The specific conditions for step A are as follows: the alkaline micro-etching solution consists of 1-5 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 1-5 g / L p-nitrobenzoic acid, and 0.1-0.5 g / L o-dithiopyridine-PEG-o-dithiopyridine, with an operating temperature of 25-35℃ and a time of 1-2 min.

[0041] The specific conditions for step B are as follows: the degreasing agent consists of 0.01-0.05 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 0.2-0.5 g / L ethylene oxide and propylene oxide block copolymer, 10-30 ppm / LOP-10, 0.5-1.5 ml / L 1,4-dioxane, and 30-60 ppm / L sodium dodecylbenzenesulfonate, and is used at a temperature of 45-55℃ for 1-2 minutes.

[0042] The beneficial effects of this invention are as follows: Compared with the prior art, the wafer zinc replacement plating solution and its process provided by this invention have the following advantages:

[0043] 1) The zinc replacement solution provided by this invention uses o-dithiopyridine-PEG-o-dithiopyridine as a homogenizer. This homogenizer can refine the grains, increase the smoothness of the zinc layer, and improve the subsequent nickel plating effect. Compared with the zinc replacement plating solution of existing Shangcun, the zinc plating layer is finer.

[0044] 2) The zinc replacement plating solution provided by this invention uses a composite complexing agent composed of maleic acid and tetrasodium iminodisuccinate, with a mass concentration ratio of 1:1 during use. The composite complexing agent can improve the stability of the plating solution and prevent precipitation. Since zinc will generate zinc hydroxide precipitate under high concentration alkaline conditions, a complexing agent is necessary to improve stability. However, the complexing effect of the complexing agents currently on the market is not obvious, and some flocculent precipitates will still precipitate after a week. In contrast, the stability effect of this application can last up to one month.

[0045] 3) The zinc replacement plating solution provided by the present invention uses aminopyrazine as a stabilizer. The stabilizer can solve the problem of uneven zinc coating caused by the replaced aluminum ions, which leads to whitening of the coating.

[0046] 4) In this invention, the concentration ratio of the complexing agent to the homogenizing agent is 4:1. This ratio is optimal; ratios that are too high or too low will result in uneven control over zinc particle growth and uneven coating thickness. The ratio of the stabilizer to the wetting agent is 1:2. The stabilizer primarily addresses the impact of the aluminum ion plating solution and the coating quality, while the wetting agent plays an auxiliary role in coating uniformity. Experiments have shown that excessively high or low stabilizer concentrations can also lead to poor uniformity.

[0047] The following are several specific embodiments of the present invention.

[0048] The evaluation criteria for the experimental tests are as follows:

[0049] 1. The indicators include: 1. Stability index: Excellent means no flocculent precipitate is produced after standing for 30 days; Good means no flocculent precipitate is produced after 20-30 days (excluding 20 days); Poor means no flocculent precipitate is produced after 10-20 days (excluding 10 days); Poor means flocculent precipitate is produced in less than 10 days; 2. Uniformity index: Excellent means the thickness difference is less than 10% compared with the average thickness; Good means the thickness difference is 10-20% compared with the average thickness; Poor means the thickness difference is 20-30% compared with the average thickness; Poor means the thickness difference is more than 30% compared with the average thickness.

[0050] Example

[0051] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 1 g / L, with the remainder being deionized water;

[0052] Operating temperature 30℃

[0053] Time: 2 min

[0054] in accordance with Figure 1 The experimental results of the example are as follows: the stability index is excellent and the uniformity index is excellent.

[0055] Comparative Example 1

[0056] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 1 g / L, balance deionized water;

[0057] Operating temperature 30℃

[0058] Time: 2 min

[0059] Comparative Example 1 lacks a complexing agent compared to the Examples, based on Figure 1 The experimental results show that the stability index is poor and the uniformity index is relatively poor.

[0060] Comparative Example 2

[0061] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 1 g / L, the balance being deionized water;

[0062] Operating temperature 30℃

[0063] Time: 2 min

[0064] Comparative Example 2 lacks a homogenizer compared to the Example, based on Figure 1 The experimental results show that the stability index is excellent, while the uniformity index is poor.

[0065] Comparative Example 3

[0066] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, 8-aminooctanoic acid 1 g / L, the balance being deionized water;

[0067] Operating temperature 30℃

[0068] Time: 2 min

[0069] Comparative Example 3 lacks a stabilizer compared to the Examples, based on Figure 1 The experimental results show that the stability index is good and the uniformity index is excellent.

[0070] Comparative Example 4

[0071] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 0.5 g / L, with the remainder being deionized water;

[0072] Operating temperature 30℃

[0073] Time: 2 min

[0074] Comparative Example 4 lacks a wetting agent compared to the Examples, based on Figure 1 The experimental results show that the stability index is excellent and the uniformity index is good.

[0075] Comparative Example 5

[0076] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 25 g / L, tetrasodium iminodisuccinate 25 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 1 g / L, with the remainder being deionized water;

[0077] Operating temperature 30℃

[0078] Time: 2 min

[0079] Compared with the examples, the ratio of complexing agent to homogenizing agent in Comparative Example 5 was increased to 5:1, based on Figure 1 The experimental results show that the stability index is excellent and the uniformity index is good.

[0080] Comparative Example 6

[0081] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 20 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 1 g / L, with the remainder being deionized water;

[0082] Operating temperature 30℃

[0083] Time: 2 min

[0084] Compared with the examples, the ratio of complexing agent to homogenizing agent in Comparative Example 6 was reduced to 2:1, based on Figure 1 The experimental results show that the stability index is excellent and the uniformity index is good.

[0085] Comparative Example 7

[0086] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 1 g / L, 8-aminooctanoic acid 1 g / L, the balance being deionized water;

[0087] Operating temperature 30℃

[0088] Time: 2 min

[0089] Compared with the examples, the stabilizer to wetting agent ratio in Comparative Example 7 was increased to 1:1, based on Figure 1 The experimental results show that the stability index is excellent and the uniformity index is good.

[0090] Comparative Example 8

[0091] Zinc oxide 10 g / L, sodium hydroxide 100 g / L, o-dithiopyridine-PEG-o-dithiopyridine 10 g / L, maleic acid 20 g / L, tetrasodium iminodisuccinate 20 g / L, aminopyrazine 0.5 g / L, 8-aminooctanoic acid 2 g / L, with the remainder being deionized water;

[0092] Operating temperature 30℃

[0093] Time: 2 min

[0094] Compared with the exemplary examples, the stabilizer to wetting agent ratio in Comparative Example 8 was reduced to 1:4, based on Figure 1 The experimental results show that the stability index is excellent and the uniformity index is good.

Claims

1. A zinc displacement plating solution for wafers, characterized in that, The product contains the following components at the following mass concentrations: zinc salt 5-15 g / L, sodium hydroxide 50-150 g / L, homogenizer 10-20 g / L, complexing agent 40-80 g / L, stabilizer 0.5-1 g / L, wetting agent 1-2 g / L, and the balance is deionized water. Operating temperature 25-35℃ The zinc salt is zinc oxide, and the particle size of the zinc oxide powder is 50-150 nm. The homogenizer is o-dithiopyridine-PEG-o-dithiopyridine; The composite complexing agent is a composition of maleic acid and tetrasodium iminodisuccinate, with a mass concentration ratio of 1:1 during use; the stabilizer is aminopyrazine; the wetting agent is 8-aminooctanoic acid; the concentration ratio of the composite complexing agent to the homogenizing agent during use is 4:1; and the concentration ratio of the stabilizer to the wetting agent during use is 1:

2. A wafer zinc replacement process obtained from the above zinc replacement plating solution includes the following specific steps: A. Alkaline micro-etching: The aluminum oxide film is removed by alkaline micro-etching, and the aluminum substrate is micro-roughened, followed by washing with pure water. B. Degreasing: Remove easily adsorbed grease, alkaline micro-etching agent residues and other impurities from the surface, and then rinse with pure water. C. Zinc plating: This involves one alkaline zinc replacement for 30-60 seconds, one zinc stripping with 30% volume concentration nitric acid for 10-15 seconds, and another alkaline zinc replacement for 60-120 seconds. After that, the zinc is placed in a nickel plating bath for nickel plating. Each replacement and zinc stripping process requires rinsing with pure water. All operations in this step are carried out at room temperature. The specific conditions for step A are as follows: the alkaline micro-etching solution consists of 1-5 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 1-5 g / L p-nitrobenzoic acid, and 0.1-0.5 g / L o-dithiopyridine-PEG-o-dithiopyridine, with an operating temperature of 25-35℃ and a time of 1-2 min. The specific conditions for step B are as follows: the degreasing agent consists of 0.01-0.05 g / L sodium hydroxide, 2 g / L tetrasodium iminodisuccinate, 0.2-0.5 g / L ethylene oxide and propylene oxide block copolymer, 10-30 ppm / LOP-10, 0.5-1.5 ml / L 1,4-dioxane, and 30-60 ppm / L sodium dodecylbenzenesulfonate, and is used at a temperature of 45-55℃ for 1-2 minutes.

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