An etching solution for selectively etching silicon nitride and silicon oxide and titanium nitride
By using an etchant containing phosphoric acid, an oxidant, and an etching inhibitor, the problem of unstable silicon nitride etching in the prior art has been solved, achieving a high selectivity etching effect, improving the yield of semiconductor products, and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI SINOPHORUS ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2024-11-25
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to effectively suppress the etching of silicon oxide and titanium nitride while etching silicon nitride, resulting in etching instability and a low selectivity, which affects the yield and production cost of semiconductor products.
A selective etching solution is used, which consists of phosphoric acid, oxidant, etching inhibitor and ultrapure water. By adding etching inhibitor, a thin film is formed on the surface of titanium nitride to reduce its etching rate, and by using surfactant to improve the solubility of etching products, the etching selectivity is improved.
This technology enables rapid etching of silicon nitride while significantly suppressing the etching of silicon oxide and titanium nitride, improving etching stability and uniformity, increasing semiconductor product yield, and saving production costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic chemicals, and specifically relates to a 3D DRAM etching solution. Background Technology
[0002] Titanium nitride is widely used in the semiconductor industry as a hard mask, metal barrier layer, conductive electrode, and metal gate due to its excellent metal diffusion barrier properties and low resistivity after annealing. Furthermore, some advanced process chips utilize titanium nitride to improve transistor performance.
[0003] Silicon nitride (SiN) possesses excellent thermal, mechanical, and chemical stability, making it widely used in high-temperature, high-power, and high-frequency electronic devices. Its wide bandgap allows for tuning of its conductivity through doping, thus making it a crucial semiconductor material.
[0004] In recent years, DRAM (Dynamic Random Access Memory) has become a widely used memory technology in various fields of computing. However, with the shrinking of transistor size, the evolution of DRAM capacity faces challenges. First, leakage current problems are becoming increasingly serious due to the shrinking factor of transistor size. Second, as the capacitance of memory cells becomes smaller, read and write operations become more difficult, which also increases the bit error rate. The densely packed transistors in traditional DRAM cause problems such as current leakage and interference in a two-dimensional plane. 3D DRAM, by stacking transistors in layers, effectively increases the spacing between transistors, significantly reducing the risk of leakage and crosstalk, and providing an innovative approach to solving these problems.
[0005] With the continuous miniaturization of semiconductor devices and feature sizes, the electronic chemicals industry is developing rapidly. Etching technology, as the most stable, efficient, and widely used technique for semiconductor materials, has been employed by the industry for a long time. However, as the semiconductor industry's requirements for product yield become increasingly stringent, how to improve the etching rate of silicon nitride while simultaneously suppressing the etching of the barrier layer titanium nitride has become a pressing problem in this field. Under the premise of ensuring etching stability and uniformity, an etchant with a higher selectivity ratio for silicon nitride, titanium nitride, and silicon oxide can better control etching time, shorten production cycles, improve product yield, and thus save on semiconductor production costs. Therefore, developing a high-selectivity etchant with excellent performance is particularly urgent. The etching solution and etching conditions described in this paper provide high etching selectivity for silicon nitride and titanium nitride materials, capable of partially or completely removing the silicon nitride structure without significantly damaging the titanium nitride structure. Summary of the Invention
[0006] The purpose of this invention is to provide an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride. This etching solution not only ensures etching stability and uniformity, but also has a high etching selectivity for silicon nitride, silicon oxide, and titanium nitride. It can partially or completely remove the silicon nitride structure without significantly damaging the silicon oxide and titanium nitride structures, thereby improving the yield of semiconductor products and saving production costs.
[0007] To achieve the above objectives, a method for producing an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride is provided, comprising the following steps:
[0008] An etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, wherein the etching solution is composed of phosphoric acid, an oxidant, an etching inhibitor, and ultrapure water.
[0009] The composition includes 10-45% acidic substances; 0.01-1.8% oxidant; 0.1-7% titanium etching inhibitor; 0.5-2.5% metal complexing agent; the balance is deionized water; and the remainder is ultrapure water.
[0010] Preferably, the acidic substance includes one or more of phosphoric acid, acetic acid, nitric acid, and sulfuric acid.
[0011] The phosphoric acid in the etching solution is electronic-grade phosphoric acid with a mass concentration of 70-95%.
[0012] Preferably, the oxidant in the etching solution is one or a combination of hydrogen peroxide, sodium hypochlorite, and potassium permanganate.
[0013] Preferably, the etching inhibitor in the etching solution is one or more of the following: teflumiazole, flubendiazole, imidazogrel, fenflurazole, 1-(3-fluorophenyl)imidazole, N-pentafluorophenoxyimidazole, 5,6-dibromobenzotriazole and 4-phenyl-1,2,3-triazole.
[0014] Preferably, the metal complexing agent is one or a combination of several of glycylglycine, triethylenetetraminehexaacetic acid, glycine tert-butyl ester, and choline bitartrate.
[0015] Furthermore, the etching solution should first be prepared by mixing phosphoric acid and ultrapure water in a certain proportion, and then slowly adding etching inhibitor and surfactant in sequence while continuously stirring, stirring evenly, sealing and storing at 30°C for 4 hours.
[0016] Another technical solution of the present invention is the application of the selective etching solution of silicon nitride, silicon oxide, and titanium nitride in etching semiconductor materials containing silicon nitride, titanium nitride, and silicon oxide.
[0017] The selective etching solution is used for selective etching of silicon nitride in etching silicon nitride-silicon oxide semiconductor materials and silicon nitride-titanium nitride semiconductor materials.
[0018] In some preferred embodiments, the etched silicon nitride-silicon oxide semiconductor material has a selectivity greater than 100, more preferably greater than 200, more preferably greater than 300, and even more preferably greater than 400.
[0019] In some preferred embodiments, the etched silicon nitride-titanium nitride semiconductor material has a selectivity greater than 20, more preferably a selectivity greater than 30, and even more preferably a selectivity greater than 100.
[0020] Furthermore, all experimental procedures involved in this invention require strict control of contamination factors in the experimental environment.
[0021] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0022] 1. Compared with existing etching processes, the present invention provides an etching solution for selectively etching silicon nitride, silicon oxide and titanium nitride. While rapidly etching silicon nitride, it greatly inhibits the etching effect of the etching solution on silicon oxide and titanium nitride, and can ensure the stability and uniformity of etching.
[0023] 2. The surfactant in the etching solution of this invention can improve the solubility of the etching products in the system, reduce the tension of the solid-liquid interface in the solution, and promote the transfer rate of interphase materials.
[0024] 3. The etching inhibitor in the etching solution of the present invention can form a thin film on the surface of titanium nitride in the form of coordination bonds with the metal, which greatly reduces the etching rate of titanium nitride by the etching solution and ensures that silicon nitride and titanium nitride have a high selectivity ratio.
[0025] This invention belongs to the field of selective etching solution technology in the semiconductor industry, specifically relating to an etching solution for selectively etching silicon nitride and titanium nitride. The etching solution described in this invention can efficiently etch silicon nitride while maintaining low etching rates for titanium nitride and silicon oxide, minimizing etching of both. During the etching process, the oxidant can significantly increase the etching rate of silicon nitride, reduce etching residue, and extend the etching solution's lifespan; the inhibitor can reduce the etching rate of titanium nitride. This reduces etching residue and extends the etching solution's lifespan. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.
[0027] Comparative Example 1
[0028] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0029] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, and the remainder is ultrapure water.
[0030] The etching temperature was 55℃ and the etching time was 10 minutes.
[0031] The preparation and etching method includes the following steps:
[0032] The etching solution was prepared in a clean container according to the composition given in the embodiment. The solution was stirred evenly and sealed, and stored at 30°C for 4 hours. After pretreatment and drying of the pre-cut silicon nitride, silicon oxide, and titanium nitride samples, the initial thickness of silicon nitride, silicon oxide, and titanium nitride was measured using an ellipsometry and a four-probe thickness gauge, respectively. The samples were then fixed with etching-specific supports and etched in the etching solution at 55°C for 10 minutes. After removal, the samples were rinsed with ultrapure water at 70°C for 10 seconds and then dried with nitrogen. The thickness of silicon nitride, silicon oxide, and titanium nitride after etching was tested, and the corresponding etching rate was obtained by calculating the change in sample thickness before and after etching.
[0033] Comparative Example 2
[0034] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0035] 40wt% phosphoric acid, 0.1wt% teflumiazole, and the remainder was ultrapure water.
[0036] The etching temperature was 55℃ and the etching time was 10 minutes.
[0037] The preparation of the etching solution and the etching method are the same as those in Comparative Example 1.
[0038] Comparative Example 3
[0039] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0040] 40wt% phosphoric acid, 2.5wt% glycine tert-butyl ester, and the remainder is ultrapure water.
[0041] The etching temperature was 55℃ and the etching time was 10 minutes.
[0042] The preparation of the etching solution and the etching method are the same as those in Comparative Example 1.
[0043] Example 1
[0044] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0045] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% teflumiazole, 2.5wt% glycine tert-butyl ester, and the remainder is ultrapure water.
[0046] The etching temperature was 55℃ and the etching time was 10 minutes.
[0047] The preparation of the etching solution and the etching method are the same as in Example 1.
[0048] Example 2
[0049] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0050] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% imidazodogrel, 2.5wt% glycine tert-butyl ester, and the remainder is ultrapure water.
[0051] The etching temperature was 55℃ and the etching time was 10 minutes.
[0052] The preparation of the etching solution and the etching method are the same as in Example 1.
[0053] Example 5
[0054] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0055] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% flubendiazole, 2.5wt% glycine tert-butyl ester, and the remainder is ultrapure water.
[0056] The etching temperature was 55℃ and the etching time was 10 minutes.
[0057] The preparation of the etching solution and the etching method are the same as in Example 1.
[0058] Example 6
[0059] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0060] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% fenflurazole, 2.5wt% glycyl glycine, and the remainder is ultrapure water.
[0061] The etching temperature was 55℃ and the etching time was 10 minutes.
[0062] The preparation of the etching solution and the etching method are the same as in Example 1.
[0063] Example 7
[0064] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0065] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% 1-(3-fluorophenyl)imidazole, 2.5wt% choline bitartrate, and the remainder was ultrapure water.
[0066] The etching temperature was 55℃ and the etching time was 10 minutes.
[0067] The preparation of the etching solution and the etching method are the same as in Example 1.
[0068] Example 8
[0069] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0070] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% N-pentafluorophenoxyimidazole, 2.5wt% 2-mercaptoimidazole, and the remainder is ultrapure water.
[0071] The etching temperature was 55℃ and the etching time was 10 minutes.
[0072] The preparation of the etching solution and the etching method are the same as in Example 1.
[0073] Example 9
[0074] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0075] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% 5,6-dibromobenzotriazole, 2.5wt% triethylenetetraminehexaacetic acid, and the remainder was ultrapure water.
[0076] The etching temperature was 55℃ and the etching time was 10 minutes.
[0077] The preparation of the etching solution and the etching method are the same as in Example 1.
[0078] Example 10
[0079] This invention provides a technical solution: an etching solution for selectively etching silicon nitride, silicon oxide, and titanium nitride, comprising the following:
[0080] 40wt% phosphoric acid, 0.2wt% hydrogen peroxide, 0.1wt% 4-phenyl-1,2,3-triazole, 2.5wt% triethylenetetraminehexaacetic acid, and the remainder was ultrapure water.
[0081] The etching temperature was 55℃ and the etching time was 10 minutes.
[0082] The preparation of the etching solution and the etching method are the same as in Example 1.
[0083] The etching rates and selection examples for each comparative example and embodiment are shown in the table below:
[0084]
[0085] The data in the table show that in Comparative Example 1, only hydrogen peroxide was added as an oxidant, resulting in unstable etching rates for both silicon nitride and titanium nitride. The etching rate of titanium nitride gradually decreased over time, leading to a high etching rate and ultimately a low etching selectivity. In Comparative Example 2, tefluimidazole was added as a titanium etching inhibitor, effectively alleviating the problem of unstable etching rates, and the etching rate of titanium nitride did not change significantly over time. In Comparative Example 3, glycine tert-butyl ester was added as a metal complexing agent, which adjusted the surface tension between the etching solution and the solid phase, increasing the wettability of the etching solution and thus facilitating the adjustment of the selectivity ratio of silicon nitride and silicon oxide.
[0086] As shown in Example 1, adding hydrogen peroxide as an oxidant, tefluimidazole as an etching inhibitor for titanium nitride, and glycine tert-butyl ester as a metal complexing agent can significantly reduce the etching rate of titanium nitride, satisfying the high selectivity ratio of silicon nitride and silicon oxide titanium nitride. This indicates that the etching inhibitor has a significant impact on the selectivity ratio. In Examples 1-8, the selectivity ratios of silicon nitride and titanium nitride are all greater than 20, and the selectivity ratios of silicon nitride and silicon oxide are all greater than 100, all meeting the requirements for high selectivity ratios of silicon nitride and titanium nitride.
[0087] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.
Claims
1. A selective etching solution for silicon nitride, silicon oxide, and titanium nitride, characterized in that, By mass percentage, it includes 10-45 wt% acidic substances; 0.01-1.8 wt% oxidant; 0.1-7 wt% titanium etching inhibitor; 0.5-2.5 wt% metal complexing agent; the balance being deionized water. The acidic substances include one or more of phosphoric acid, acetic acid, nitric acid, and sulfuric acid; The oxidant is one or a combination of several of hydrogen peroxide, sodium hypochlorite, and potassium permanganate. The titanium etching inhibitor is one or a combination of several of the following: teflumiazole, flubendiazole, imidazogrel, fenflurazole, 1-(3-fluorophenyl)imidazole, N-pentafluorophenoxyimidazole, 5,6-dibromobenzotriazole and 4-phenyl-1,2,3-triazole. The metal complexing agent is one or a combination of several of glycyl glycine, triethylenetetramine hexaacetic acid, glycine tert-butyl ester, and choline bitartrate.
2. The selective etching solution for silicon nitride, silicon oxide, and titanium nitride according to claim 1, characterized in that: The selection ratio of silicon nitride to titanium nitride in the etching is greater than 15, and the selection ratio of silicon nitride to silicon oxide is greater than 100.
3. The application of the selective etching solution of silicon nitride, silicon oxide, and titanium nitride according to claim 1 in etching semiconductor materials containing silicon nitride, titanium nitride, and silicon oxide.
4. The application according to claim 3, characterized in that, The selective etching solution is used for selective etching of silicon nitride in etching silicon nitride-silicon oxide semiconductor materials and silicon nitride-titanium nitride semiconductor materials.
5. The application according to claim 4, characterized in that, In the etched silicon nitride-silicon oxide semiconductor material, the selectivity is greater than 100; In the etched silicon nitride-titanium nitride semiconductor material, the selectivity is greater than 20.
6. The application according to claim 5, characterized in that, In the etched silicon nitride-silicon oxide semiconductor material, the selectivity is greater than 200; In the etched silicon nitride-titanium nitride semiconductor material, the selectivity is greater than 30.
7. The application according to claim 6, characterized in that, In the etched silicon nitride-silicon oxide semiconductor material, the selectivity is greater than 300; The selectivity of the etched silicon nitride-titanium nitride semiconductor material is greater than 100.
8. The application according to claim 7, characterized in that, In the etched silicon nitride-silicon oxide semiconductor material, the selectivity is greater than 400.