A selective etching solution of carbon-doped silicon nitride / silicon oxide

Abstract

This invention discloses a selective etching solution for silicon carbonitride / silicon oxide, comprising the following raw materials by mass fraction: 50-80% catalyst, 1-10% oxidizing agent; 2-10% fluorine-containing compound, 0.1-1% fluoride ion stabilizer, 0.1-1% selective additive; and the balance being deionized water. This etching solution can increase the etching rate of silicon carbonitride to a certain level while maintaining a 5:1 selectivity ratio for silicon oxide.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals technology, specifically relating to a selective etching solution doped with silicon carbide / silicon oxide. Background Technology

[0002] Silicon-carbon-nitrogen (SiCN) is a semiconductor material composed of a ternary compound of silicon, carbon, and nitrogen. It possesses the excellent optical, electrical, magnetic, thermodynamic, and mechanical properties of both silicon carbide and silicon nitride. SiCN is inexpensive to grow on silicon substrates and exhibits excellent compatibility with very large-scale integrated circuits. These characteristics make SiCN one of the preferred materials for optoelectronic devices, offering significant economic and social benefits.

[0003] As the carbon doping content increases, the corrosion resistance of SiCN gradually improves. Due to this property, it can be used as a barrier layer in semiconductor wet processing applications. After this process, it is usually removed using an etching solution. There is currently no relevant data to support the removal of SiCN. Removing SiCN also requires the use of a barrier layer to protect the remaining wafer. This is an urgent problem to be solved in future semiconductor processes. Therefore, it is crucial to have a certain etching rate for it and a certain selectivity for silicon oxide as a barrier layer.

[0004] In SiCN films, the carbon doping ratio is about 1-10%. For films with lower carbon doping, DHF solution can be used for etching. The etching rate decreases as the carbon doping increases. When the carbon content exceeds 10%, the etching rate approaches 0 infinitely and there is no obvious selectivity for silicon oxide. The selectivity ratio is about 1 / 150. Even if an oxidant is added, the above requirements cannot be met.

[0005] During the screening of etching solutions, this invention discovered that the material has excellent corrosion resistance and cannot be etched by conventional etching solutions. Commonly available etching solutions do not have fast and stable etching performance. Therefore, from principle to experiment, careful and in-depth research is required. This invention selects the relevant raw materials to control the etching rate of SiCN film with carbon doping greater than 10% at about 20A / min, with a selectivity ratio of 5:1 for silicon oxide, and the solution stability can be maintained for 12h. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a selective etching solution doped with silicon carbide / silicon oxide.

[0007] To achieve the above objectives, the present invention provides a selective etching solution for silicon carbide / silicon oxide, characterized in that: (1) the carbon content of the silicon carbide is 10-20%; (2) it comprises the following raw materials by mass percentage: 50-90% catalyst material; 1~10% oxidizing substances; 2-10% fluorine-containing compounds; 0.1~1% fluoride ion stabilizer; 0.1-1% selective additives; The remainder is deionized water.

[0008] Preferably, the carbon content of the carbon-doped silicon nitride is 10-20%, and more preferably 10%, 15% and 20%. As the carbon content increases, the etching difficulty increases exponentially, and the requirements for the etching solution are also higher. In the end, the present invention adopts SiCN with a carbon content of 20%.

[0009] Preferably, the catalyst is an aqueous solution with a mass fraction of 70-90%.

[0010] More preferably, the alkaline substance is any one of an aqueous solution of sulfuric acid, phosphoric acid, acetic acid, boric acid, citric acid, oxalic acid, or maleic acid.

[0011] The addition of a catalyst in this invention can significantly reduce the activation energy during the reaction and increase the etching rate.

[0012] Preferably, the oxidant is an aqueous solution with a mass fraction of 10-30%.

[0013] More preferably, the oxidant is any one of the aqueous solutions of sodium hypochlorite, potassium hypochlorite, potassium permanganate, hydrogen peroxide, ammonium persulfate, and nitric acid.

[0014] The addition of the oxidant in this invention can, on the one hand, increase the etching rate and accelerate the reaction process by oxidizing the film layer; on the other hand, the oxidant will not oxidize silicon oxide, which can indirectly improve the selectivity.

[0015] Preferably, the fluorinated compound is an aqueous solution with a mass fraction of 15-35%.

[0016] More preferably, the fluorinated compound is any one of ammonium fluoride, ammonium hydrogen fluoride, hydrofluoric acid, and tetrabutylammonium fluoride aqueous solution.

[0017] The addition of fluorinated compounds in this invention can significantly improve the etching rate, reduce the etching rate of silicon-containing compounds, and react with subsequent selectants to increase the selectivity ratio.

[0018] Preferably, the fluoride ion stabilizer is any one of sodium borate, niobium chloride, and titanium oxalate.

[0019] The present invention uses high-temperature etching conditions, which accelerates the escape of fluoride ions. With the addition of fluoride ion stabilizers, complex structures can be formed with fluoride ions, reducing the escape rate of fluoride ions and greatly extending the solution life.

[0020] Preferably, the selective additive is any one of ureapropyltriethoxysilane, mercaptopropyltriethoxysilane, aminopropyltriethoxysilane, aminoethylaminoisobutylmethyldimethoxysilane, and N-[3-(trimethoxysilyl)propyl]but-1-amine.

[0021] This invention employs a corresponding silane, which has a significant inhibitory effect on the etching rate of silicon oxide and can react with fluoride ions to improve the selectivity.

[0022] The beneficial effects of this invention are as follows: 1. In this experiment, silicon carbonitride was etched. This material has excellent etching resistance. This invention can etch this material and has a certain etching rate that can be controlled.

[0023] 2. While ensuring the etching rate, adding a silicon oxide film layer as a barrier layer provides a certain basis for its application.

[0024] 3. The addition of fluoride ion stabilizers to the etching solution gives it a longer lifespan and increases its stability. Detailed Implementation

[0025] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0026] Note: To verify the selectivity ratio of 1.0%~10% carbon doping and 10~20% carbon doping of silicon carbide in DMF and DHF oxidant solutions mentioned in the background of this invention, we etched silicon oxide simultaneously with 5% carbon doping SiCN and 20% carbon doping SiCN used in this invention in Example 1 and Comparative Examples 6, 7 and 8.

[0027] Example 1 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 10% carbon doping is selected. The formulation is as follows: 55% phosphoric acid aqueous solution (mass fraction of 89%), 4% sodium hypochlorite solution (mass fraction of 20%), 6% ammonium fluoride aqueous solution (mass fraction of 25%), 0.5% sodium borate, 0.2% ureapropyltriethoxysilane, and the remainder is deionized water.

[0028] Example 2 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 15% carbon doping is selected. The formulation is as follows: 65% aqueous acetic acid solution (mass fraction 85%), 5% aqueous potassium hypochlorite solution (mass fraction 10%), 1.2% aqueous ammonium bifluoride solution (mass fraction 35%), 0.7% sodium borate, 0.01% mercaptopropyltriethoxysilane, and the remainder is deionized water.

[0029] Example 3 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 20% carbon doping is selected. The formulation is as follows: 75% sulfuric acid aqueous solution (mass fraction 78%), 7% potassium permanganate aqueous solution (mass fraction 15%), 1.5% tetrabutylammonium fluoride aqueous solution (mass fraction 23%), 0.7% niobium chloride, 0.01% N-[3-(trimethoxysilyl)propyl]but-1-amine, and the remainder is deionized water.

[0030] Example 4 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 10% carbon doping is selected. The formulation is as follows: 70% boric acid aqueous solution (mass fraction of 80%), 5% hydrogen peroxide aqueous solution (mass fraction of 12%), 2% hydrofluoric acid aqueous solution (mass fraction of 15%), 0.8% titanium oxalate, 0.01% aminopropyltriethoxysilane, and the remainder is deionized water.

[0031] Example 5 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 15% carbon doping is selected. The formulation is as follows: 60% citric acid solution (18% by mass), 7% nitric acid aqueous solution (14% by mass), 3.5% hydrofluoric acid aqueous solution (25% by mass), 0.7% niobium chloride, 0.02% aminoethylaminoisobutylmethyldimethoxysilane, and the remainder is deionized water.

[0032] Example 6 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 20% carbon doping is selected. The formulation is as follows: 75% oxalic acid aqueous solution (mass fraction of 19%), 4% ammonium persulfate aqueous solution (mass fraction of 12%), 1% tetrabutylammonium fluoride aqueous solution (mass fraction of 15%), 0.6% titanium oxalate, 0.02% ureapropyltriethoxysilane, and the remainder is deionized water.

[0033] Example 7 A selective etching solution for silicon carbide / silicon oxide is provided. In this embodiment, a silicon carbide wafer with 10% carbon doping is selected. The formulation is as follows: 80% maleic acid aqueous solution (mass fraction 20%), 8% ammonium persulfate aqueous solution (mass fraction 20%), 1% tetrabutylammonium fluoride aqueous solution (mass fraction 30%), 1% sodium borate, 0.02% ureapropyltriethoxysilane, and the remainder is deionized water.

[0034] Comparative Example 1 A selective etching solution doped with silicon carbonitride / silicon oxide has the same formulation as in Example 6, except that it does not contain an aqueous solution of oxalic acid.

[0035] Comparative Example 2 A selective etching solution doped with silicon carbonitride / silicon oxide has the same formulation as in Example 6, except that it does not contain an aqueous solution of ammonium persulfate.

[0036] Comparative Example 3 A selective etching solution doped with silicon carbonitride / silicon oxide has the same formulation as in Example 6, except that it does not contain an aqueous solution of tetrabutylammonium fluoride.

[0037] Comparative Example 4 A selective etching solution doped with silicon carbonitride / silicon oxide, with the same formulation as in Example 6, except that sodium borate is not added.

[0038] Comparative Example 5 A selective etching solution doped with silicon carbonitride / silicon oxide, with the same formulation as in Example 6, except that ureapropyltriethoxysilane is not added.

[0039] Comparative Example 6 A 2% HF aqueous solution was used to simultaneously etch SiCN with 5% carbon doping, silicon oxide, and SiCN with 20% carbon doping.

[0040] Comparative Example 7 A 2% HF and 0.5% HNO3 aqueous solution was used to simultaneously etch SiCN with 5% carbon doping, silicon oxide, and SiCN with 20% carbon doping.

[0041] Comparative Example 8 A 2% HF, 0.5% HNO3 and 0.2% ureapropyltriethoxysilane aqueous solution were used to simultaneously etch SiCN with 5% carbon doping, silicon oxide and SiCN with 20% carbon doping.

[0042] Results testing: Silicon carbide and silicon oxide wafers purchased from Hynix were cut into 10mm × 10mm pieces and etched using the following method: Etching rate test: Polycrystalline silicon wafers were cleaned in a 200:1 hydrofluoric acid solution at 80℃ for 40 seconds to remove the hydrolyzed oxide layer on the surface. Ellipsometry was used to measure the carbonitride and silicon oxide wafers. The initial thickness of the carbonitride and silicon oxide wafers was calculated using model fitting. The average value of four measurements on each wafer was taken. The carbonitride wafers were then immersed in etching solution for 5-10 minutes, cleaned, and dried with nitrogen. The spectra of the carbonitride and silicon oxide wafers were measured using an ellipsometry (keeping the test points consistent with the time points before the etching). The thickness of the carbonitride and silicon oxide wafers was calculated by fitting and averaging the results. The etching rate of the carbonitride and silicon oxide wafers was then calculated. The etching rates of the carbonitride and silicon oxide wafers using the selective etching solutions prepared in the above examples and comparative examples are shown in Table 1.

[0043] Table 1. Effect of etching time on the etching rate of uniform etchant formula Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 20% SiCN etching rate 25.23 23.02 35.22 45.31 28.69 19.56 17.58 5% SiCN etching rate 98.63 - - - - - - SiO2 etching rate 5.02 4.23 6.11 7.78 5.44 3.25 3.31 formula Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 20% SiCN etching rate 1.23 2.53 0.25 19.11 19.56 0.03 0.02 0.02 5% SiCN etching rate - - - - - 0.85 1.35 1.07 SiO2 etching rate 3.15 2.03 1.25 3.32 53.25 175.44 179.15 65.32 Table 2 Effect of Etching Stability Time / h Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 0 25.23 23.02 35.22 45.31 28.69 19.56 17.58 2 25.21 23.00 35.14 45.11 28.67 19.52 17.56 4 25.14 22.95 35.07 45.02 28.60 19.50 17.55 6 25.12 22.87 35.02 44.91 28.52 19.47 17.53 8 25.11 22.84 34.91 44.83 28.44 19.44 17.50 Time / h Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 0 1.23 2.53 0.25 19.11 19.56 2 1.23 2.50 0.25 11.21 19.49 4 1.22 2.49 0.24 5.43 19.44 6 1.20 2.44 0.24 2.12 19.40 8 1.18 2.43 0.22 2.03 19.37 As shown in Table 1, there is a significant difference in the etching rate between the etching solutions prepared in Examples 1-7 and those prepared in Comparative Examples 1, 2, and 3. This indicates that the addition of a catalyst is the key to the etching of polycrystalline silicon wafers, and the addition of a catalyst is more conducive to the etching of SiCN. Comparative Examples 6, 7, and 8 verified the relevant content of the present invention. Furthermore, Example 1 showed a higher selectivity for 5% carbon-doped SiCN compared to Comparative Examples 6, 7, and 8, while Comparative Examples 6, 7, and 8 were unable to etch 20% carbon-doped SiCN, with the etching rate approaching 0.

[0044] Compared with the etching solution prepared in Comparative Example 4, the addition of fluoride ion stabilizer is more beneficial to the stability of the uniform etching solution prepared in Examples 1-7.

[0045] Compared with the etching solution prepared in Comparative Example 5, the uniform etching solution prepared in Examples 1-7 shows that the addition of selective substances is more beneficial to reducing the etching rate of silicon oxide, providing a barrier layer for the next process, and laying the foundation for later applications.

Claims

1. A selective etching solution of carbon-doped silicon nitride / silicon oxide, characterized by: (1) The carbon content of the carbon-doped silicon nitride is 10~20%; (2) It includes the following raw materials by mass percentage: 50-90% catalyst material; the catalyst material, by mass percentage, is any one of the following: 70-90% aqueous solution of sulfuric acid, 70-90% aqueous solution of phosphoric acid, 70-90% aqueous solution of acetic acid, 70-90% aqueous solution of boric acid, 70-90% aqueous solution of citric acid, 70-90% aqueous solution of oxalic acid, and 70-90% aqueous solution of maleic acid; 1~10% oxidizing agent; the oxidizing agent is any one of the following: aqueous solution of sodium hypochlorite, aqueous solution of potassium hypochlorite, aqueous solution of potassium permanganate, aqueous solution of hydrogen peroxide, aqueous solution of ammonium persulfate, and aqueous solution of nitric acid; 2-10% fluorine-containing compound; the fluorine-containing compound is any one of the following: aqueous solution of ammonium fluoride, aqueous solution of ammonium hydrogen fluoride, aqueous solution of hydrofluoric acid, and aqueous solution of tetrabutylammonium fluoride; 0.1-1% fluoride ion stabilizer; the fluoride ion stabilizer is any one of sodium borate, niobium chloride, and titanium oxalate; 0.1~1% selective additive; the selective additive is any one of ureapropyltriethoxysilane, mercaptopropyltriethoxysilane, aminopropyltriethoxysilane, aminoethylaminoisobutylmethyldimethoxysilane, and N-[3-(trimethoxysilyl)propyl]but-1-amine; The remainder is deionized water.

2. The selective etching liquid of carbon-doped silicon nitride / silicon oxide according to claim 1, characterized by: The carbon doping content of the silicon carbide wafer is 15-20%.

3. The selective etching liquid of carbon-doped silicon nitride / silicon oxide according to claim 1, wherein: The oxidizing substance is an aqueous solution with a mass fraction of 10-30%.

4. The selective etching liquid of carbon-doped silicon nitride / silicon oxide according to claim 1, wherein: The fluorinated compound is an aqueous solution with a mass fraction of 15-35%.