Selective nickel etching solution

Abstract

The invention provides a selective nickel etching solution which comprises the following components in percentage by mass: 10-30% of nitric acid, 10-20% of acetic acid, 0.01-0.1% of organic acid, 0.1-1% of an etching inhibitor, 0.01-0.5% of a surfactant and the balance of water. In the nickel etching process, the stable etching rate can be kept, and the selection ratio of aluminum and copper is high. According to the etching solution, aluminum can be passivated by adjusting the content of nitric acid, and then part of organic matters with organic groups can be adsorbed on the surfaces of aluminum and copper to prevent the aluminum and copper from being further etched; and the surfactant can adjust the interfacial tension between the etching solution and the nickel surface, improve the wettability of the solution and avoid the pitting effect. The etching solution disclosed by the invention can etch metal nickel at a relatively high rate, and has a relatively high selection ratio for aluminum and copper.

Description

Technical Field

[0001] The invention belongs to the etching technology of the semiconductor industry, and specifically relates to an etching liquid which can quickly etch nickel but has a relatively high selectivity for aluminum and copper. Background Art

[0002] With the development of information technology, the semiconductor industry is changing with each passing day. Tens of thousands of wafers can be produced every day. Hundreds of processes are required in the process of making wafers into semiconductors. Among them, one of the most important processes is etching, which is to engrave fine circuit patterns on wafers. Wet etching can change the formula of the liquid to have a higher selectivity for specific thin film materials. In the metal wiring process, a layer of nickel film is plated, and the unnecessary parts need to be removed by wet etching, and it will not affect other metals such as aluminum and copper.

[0003] There are two main types of existing nickel etching liquid systems. One is a system based on iron sulfate and copper sulfate. This system can meet the nickel / copper selectivity ratio, but this system cannot eliminate the influence of the galvanic cell effect, which will lead to problems such as uncontrollable etching liquid rate and uneven etching in the later stage of etching. The other is an acidic system based on nitric acid and phosphoric acid. Although this system is relatively stable, this acidic system will also cause certain etching to aluminum and copper. Therefore, a nickel etching liquid with high efficiency and stability in etching rate and good selectivity to aluminum and copper is needed. Summary of the invention

[0004] The invention aims to provide a nickel etching solution which can have a high etching rate for nickel and a high selectivity for aluminum and copper.

[0005] To achieve the above purpose, the technical solution of the present invention provides a nickel etching solution, which is composed of nitric acid, acetic acid, an organic acid, an etching inhibitor, a surfactant and water; wherein the mass fraction of nitric acid is 10-30%, the mass fraction of acetic acid is 10-20%, the mass fraction of organic acid is 0.01-0.1%, the mass fraction of etching inhibitor is 0.1%-1%, the mass fraction of surfactant is 0.01%-0.5%, and the balance is water.

[0006] The organic acid is an organic acid containing a hydroxyl group and a carboxyl group, and is one or more of citric acid, tartaric acid, gallic acid, salicylic acid or malic acid.

[0007] The etching inhibitor is one or more of tea polyphenols, eugenol, xanthone, 1-naphthol or 1-amino-2-naphthol-4-sulfonic acid.

[0008] The surfactant is one or more of betaine, sodium oleate, octadecylamine, sodium laurate, coconut amine, sodium stearate, sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

[0009] A nickel etching method is provided, wherein an etching solution is brought into contact with a substrate comprising Ni, Cu and Al films.

[0010] The contacting is to immerse the substrate containing Ni, Cu and Al films in the etching solution, the contacting time is 5-10 minutes, the contacting temperature is 25° C.-50° C., and the stirring rate during the contacting is 300 r / min-500 r / min.

[0011] In the technical solution of the present invention, nitric acid and acetic acid provide the H required for etching. + The addition of surfactants enhances the wettability of the solution, while the added organic acids and etching inhibitors can be adsorbed on the surfaces of aluminum and copper to prevent further etching.

[0012] The beneficial effects of the present invention are as follows: in the present invention, organic acid and etching inhibitor are adsorbed layer by layer on the surface of aluminum and copper due to their special structure, preventing them from being further etched, and at the same time, almost no effect is caused on the etching of nickel, thereby improving the selectivity of aluminum and copper; at the same time, the etching solution can effectively solve the problems of unstable etching rate of the etching solution and nickel etching residue. DETAILED DESCRIPTION

[0013] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0014] The etching solution of each embodiment and comparative example is prepared by mixing the components described in Table 1, with the remainder being water.

[0015] Table 1 shows the components and contents of the etching solutions in the examples and comparative examples.

[0016] Cut the nickel, copper and aluminum test pieces into 1.6*1.6cm 2 The large and small fragments were immersed in the etching solution described in the embodiment and the comparative example, respectively, the etching temperature was 25°C, the etching time was 5min, the stirring rate was 300r / min, rinsed with ultrapure water, blown dry with nitrogen, and then the thickness before and after etching was measured with a four-probe to obtain the etching rate and selectivity. The results of the embodiment and the comparative example are summarized in Table 2.

[0017] Table 2 is the etching data of the embodiment and the comparative example

[0018] According to the experimental results of the above embodiments, it can be seen that since aluminum and nickel both have passivation under certain conditions, increasing the nitric acid content within a certain range is beneficial to etching nickel, but excessive nitric acid will also cause nickel to passivate, resulting in a decrease in etching rate. The addition of organic acid and additives can form a protective film on the surface of aluminum and copper to prevent further etching of aluminum and copper, thereby improving the selectivity to a certain extent. The addition of surfactants can reduce surface tension and improve the wettability of the etching solution.

Claims

1. A selective nickel etching solution, characterized in that: The composition comprises the following components by mass fraction: 10-30% nitric acid, 10-20% acetic acid, 0.01-0.1% organic acid, 0.1%-1% etching inhibitor, 0.01%-0.5% surfactant, and the balance is water.

2. A selective nickel etching solution according to claim 1, characterized in that: The organic acid is an organic acid containing a hydroxyl group and a carboxyl group, and is one or more of citric acid, tartaric acid, gallic acid, salicylic acid or malic acid.

3. A selective nickel etching solution according to claim 1, characterized in that: The etching inhibitor is one or more of tea polyphenols, eugenol, xanthone, 1-naphthol or 1-amino-2-naphthol-4-sulfonic acid.

4. A selective nickel etching solution according to claim 1, characterized in that: The surfactant is one or more of betaine, sodium oleate, octadecylamine, sodium laurate, coconut amine, sodium stearate, sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

5. A method for etching nickel, characterized in that: The etching solution according to any one of claims 1 to 4 is brought into contact with a substrate comprising Ni, Cu and Al thin films.

6. The etching method according to claim 5, characterized in that: The contacting is to immerse the substrate containing Ni, Cu and Al films in the etching solution, the contacting time is 5-10 minutes, the contacting temperature is 25° C.-50° C., and the stirring rate during the contacting is 300 r / min-500 r / min.

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