A selective etching solution
By optimizing the composition of the etching solution and using a combination of electronic-grade phosphoric acid, fluoride ion source, hydroxyl-containing organic compounds and inhibitors, the problem of over-etching of the alumina layer during silicon nitride etching was solved, achieving highly selective etching and a long-life etching solution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI SINOPHORUS ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2023-09-13
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies struggle to effectively retain the alumina layer while etching silicon nitride, resulting in a mismatch in etching rates and poor etching selectivity.
A selective etching solution is used, which contains electronic-grade phosphoric acid, fluoride ion source, hydroxyl-containing organic matter and inhibitor. The composition of the etching solution is optimized to improve the etching rate of silicon nitride and reduce the etching rate of aluminum oxide. The combination of the components in the etching solution achieves selective etching.
The etching rate ratio of silicon nitride to aluminum oxide reached over 3:1, and the etching rate ratio of silicon nitride to silicon oxide reached over 100:1, which improved etching selectivity and the service life of the etching solution.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic chemicals, and specifically relates to a selective etching solution. Background Technology
[0002] In the integrated circuit manufacturing process, when fabricating specific gate MOSFET devices, aluminum oxide is often used as the Hi-k dielectric layer material and silicon nitride is used as the hard mask layer. In the MOSFET manufacturing process, it is necessary to selectively remove silicon nitride while retaining the aluminum oxide layer.
[0003] Currently, the commonly used silicon nitride etching solution is high-temperature phosphoric acid, which has an etching rate of about 65 A / min for silicon nitride and about 80 A / min for alumina. It is difficult to retain as much alumina as possible while etching silicon nitride. Summary of the Invention
[0004] This invention provides a selective etching solution that solves the problem of over-etching the aluminum oxide layer during silicon nitride etching.
[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:
[0006] A selective etching solution, characterized in that the etching solution is an electronic grade product, and its main components include 50-90% phosphoric acid, 0.01-0.5% fluoride ion source, 0.01-2% hydroxyl-containing organic matter, 0.1%-2% inhibitor, and the balance being water, accounting for 50-90% of the mass of the etching solution.
[0007] In the above scheme, the phosphoric acid is electronic grade phosphoric acid with a concentration of ≥85% and a metal ion content of ≤20ppb.
[0008] In the above scheme, the fluoride ion source is one or a mixture of several of the following: ammonium hexafluorophosphate, tetramethylammonium hexafluorophosphate, tetraethylammonium hexafluorophosphate, and tetrabutylammonium hexafluorophosphate.
[0009] In the above scheme, the hydroxyl-containing organic compound is one or a mixture of several of the following: 2,2,2-trifluoroethanol, tris(hydroxymethyl)nitromethane, 3,3,3-trifluoroprop-1-ol, 4,4,4-trifluoro-1-butanol, and 2-nitroethanol.
[0010] In the above scheme, the inhibitor is one or a mixture of several of the following: bis(tert-butoxycarbonyl)amine, N-(tert-butoxycarbonyl)-1,4-butanediamine, N,O-bis(tert-butoxycarbonyl)hydroxylamine, N-(tert-butoxycarbonyl)-N'-methylethylenediamine, and N-tert-butoxycarbonyl-1,3-propanediamine.
[0011] In the above scheme, the etching rate ratio of the silicon nitride layer to the aluminum oxide layer is above 3:1, and the silicon nitride etching rate is above 50A / min.
[0012] In the above scheme, the etching rate ratio of the etching solution for the silicon nitride layer to the silicon oxide layer is greater than 100:1.
[0013] An etching method wherein, when selectively removing the first layer from a substrate having a first layer comprising titanium nitride (TiN) and a second layer comprising aluminum oxide or silicon oxide, an etching solution containing phosphoric acid, a fluoride ion source, a hydroxyl-containing organic compound, an inhibitor, and water is applied to the second layer to slow down the treatment.
[0014] The method of applying the etching solution to the substrate includes the step of immersing the substrate in the etching solution.
[0015] A method for manufacturing a semiconductor device, wherein the etching method described above is used to remove a first layer containing titanium nitride (TiN), slow down the etching of a second layer of silicon oxide and aluminum oxide, and manufacture the semiconductor device from the remaining substrate.
[0016] Beneficial effects of the present invention
[0017] 1. The additives in the selective etching solution do not contain metal ions, so they will not introduce metal ions into the etching solution and will not have a negative impact on the MOSFET, a critical chip manufacturing process that the etching solution is used for.
[0018] 2. The fluorine ion source in the selective etching solution is bound by weak covalent bonds. It is continuously and stably released in the solution as the etching process proceeds, thereby steadily increasing the etching rate of silicon nitride and giving the etching solution a longer service life.
[0019] 3. The hydroxyl-containing organic compounds in the selective etching solution contain trifluoromethyl or nitro groups, which are strong electron-withdrawing groups. These groups help to enhance the bonding between hydroxyl groups and silanol bonds on the surface of silicon oxide and aluminum hydroxyl bonds on the surface of aluminum oxide, thereby reducing the etching rate of silicon oxide and aluminum oxide layers.
[0020] 4. The inhibitors in the selective etching solution can work together with hydroxyl-containing organic compounds to form an adsorption layer on the surface of the alumina layer, reducing the etching rate of the alumina layer and further improving the etching selectivity ratio of silicon nitride and alumina. Detailed Implementation
[0021] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.
[0022] Examples 1-9:
[0023] The contents of each component in the embodiments and comparative examples conceived in this invention are listed in Table 1, with the remainder being water.
[0024] Table 1
[0025]
[0026]
[0027] The etching with selective etching solution is performed as follows:
[0028] The selective etching solution temperature is 140℃, and the etching method is immersion etching. The etching rate is collected on a single piece using silicon nitride, silicon oxide, and aluminum oxide. The process is as follows: etching solution etching → ultrapure water rinsing → high-purity nitrogen drying.
[0029] Etching experiments were conducted using selective etchant solutions with various combinations of configurations according to embodiments conceived in this invention, and the results are listed in Table 2.
[0030] Table 2
[0031]
[0032] Comparing the above examples and comparative examples, the data shows that the addition of a fluoride ion source can significantly increase the etching rate of silicon nitride by the etching solution, while also promoting the etching of silicon oxide and aluminum oxide. Comparing the data from Comparative Examples 2, 3, and 4, it can be seen that hydroxyl-containing organic compounds inhibit the etching rates of both silicon oxide and aluminum oxide, while inhibitors primarily inhibit the etching rate of aluminum oxide. Comparing the experimental data from the examples and comparative examples, it can be seen that hydroxyl-containing organic compounds and inhibitors can protect silicon oxide and aluminum oxide in the presence of a fluoride ion source. The interaction of the three additives can reduce the etching rate of silicon oxide and aluminum oxide by the etching solution while increasing the etching rate of silicon nitride, resulting in an etching rate ratio of silicon nitride to aluminum oxide of 3:1 or higher, a silicon nitride etching rate of 50 A / min or higher, and an etching rate ratio of silicon nitride to silicon oxide of 100:1 or higher.
[0033] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A selective etching solution, characterized in that, The etching solution is an electronic-grade product. Its main components include 50-90% phosphoric acid, 0.01-0.5% fluoride ion source, 0.01-2% hydroxyl-containing organic compound, and 0.1%-2% inhibitor, with the balance being water. The fluoride ion source is one or a mixture of several of the following: ammonium hexafluorophosphate, tetramethylammonium hexafluorophosphate, tetraethylammonium hexafluorophosphate, and tetrabutylammonium hexafluorophosphate. The hydroxyl-containing organic compound is 2,2,2-trifluoroacetylene. The inhibitor is one or a mixture of several of the following: alcohol, tris(hydroxymethyl)nitromethane, 3,3,3-trifluoroprop-1-ol, 4,4,4-trifluoro-1-butanol, and 2-nitroethanol; and the inhibitor is one or a mixture of several of the following: bis(tert-butoxycarbonyl)amine, N-(tert-butoxycarbonyl)-1,4-butanediamine, N,O-bis(tert-butoxycarbonyl)hydroxylamine, N-(tert-butoxycarbonyl)-N'-methylethylenediamine, and N-tert-butoxycarbonyl-1,3-propanediamine.
2. The selective etching solution according to claim 1, characterized in that, The phosphoric acid is electronic grade phosphoric acid with a concentration ≥ 85% and a metal ion content ≤ 20 ppb.
3. The selective etching solution according to claim 1, characterized in that, The etching rate ratio of the silicon nitride layer to the aluminum oxide layer in the etching solution is greater than 5:1, and the silicon nitride etching rate is greater than 50A / min.
4. The selective etching solution according to claim 1, characterized in that, The etching rate ratio of the silicon nitride layer to the silicon oxide layer in the etching solution is above 100:1.