Silicon dioxide and amorphous indium tin oxide selective etching solution
By adding ITO etching inhibitors and surfactants to the silica etching solution and using alcohol solvents to reduce HF dissociation and form a protective layer, the corrosion problem of amorphous indium tin oxide was solved, achieving highly selective etching and ensuring the electrical performance and yield of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUBEI SINOPHORUS ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2025-12-12
- Publication Date
- 2026-04-24
AI Technical Summary
Existing silicon dioxide etching solutions are highly corrosive to amorphous indium tin oxide, causing pinholes, edge corrosion, or film peeling on electrode lines, which affects the conductivity and yield of devices.
By adding ITO etching inhibitors and surfactants, and using alcohols as solvents, the dissociation of HF is reduced, which assists the etching reaction of F- on SiO2, forming a stable chelate compound protective layer, inhibiting the etching of amorphous ITO, and the alcohol molecules form a weak interaction with the SiO2 surface, maintaining the etching efficiency of silicon dioxide.
Highly selective etching of silicon dioxide and amorphous indium tin oxide was achieved, with etching rates controlled at 0.03 nm/min and below, significantly improving etching selectivity, reducing the corrosion rate of amorphous ITO, and ensuring the electrical performance and yield of the device.
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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 for silicon dioxide and amorphous indium tin oxide. Background Technology
[0002] In the manufacturing of precision electronic devices such as display panels, semiconductor chips, and touch modules, silicon dioxide (SiO2) and amorphous indium tin oxide (ITO) often form a composite structure of "insulating layer-electrode layer". Silicon dioxide, as the insulating dielectric layer, requires etching to form specific patterns for circuit isolation. Amorphous indium tin oxide possesses many excellent physical properties, including low resistivity, high visible light transmittance, high infrared reflectance, good adhesion to substrates, and scratch resistance, making it easy to fabricate electrode patterns. It has been widely used as a transparent electrode in flat panel displays such as LCDs, PDPs, FEDs, and OLEDs / PLEDs. However, amorphous ITO, as a transparent conductive electrode, has a high degree of crystal structure disorder and defect density, resulting in significantly higher chemical activity than silicon dioxide and making it more susceptible to corrosion by etching solutions. Therefore, developing a highly selective etching solution for silicon dioxide / amorphous indium tin oxide (ITO) has become an urgent problem to be solved.
[0003] Existing silica etching solutions use hydrofluoric acid (HF) as the core component. While they can efficiently etch silica, HF is also highly corrosive to amorphous ITO, which is prone to defects and has high reactivity. During the etching process, the surface of amorphous ITO is easily attacked by HF, leading to pinholes, edge corrosion, or film peeling in the electrode lines. This directly causes a decrease in device conductivity and a sharp drop in yield. Summary of the Invention The purpose of this invention is to overcome the shortcomings of existing technologies and provide a selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO). By adding ITO etching inhibitors and surfactants, the etching ability of ITO is weakened. Simultaneously, an alcohol is used as a solvent. Alcohols, with their lower polarity than water, reduce the dissociation degree of HF, slowing down the corrosion rate of amorphous ITO by HF. Furthermore, alcohol molecules can form weak interactions with the hydroxyl groups on the silicon dioxide surface, assisting the etching process. - The etching reaction of SiO2, while suppressing the etching of amorphous ITO, has virtually no impact on the etching efficiency of silicon dioxide, significantly improving selectivity. Under the premise of ensuring an etching rate of amorphous indium tin oxide (ITO) ≤0.03 nm / min, silicon dioxide material is rapidly removed, achieving a high selectivity ratio of silicon dioxide / amorphous indium tin oxide (ITO).
[0004] The technical solution of this invention: A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) comprises, by mass percentage, 85%-93% alcohol, 0.3%-3% fluorine-containing substances, 0.1%-3% etching inhibitor, 0.1%-1% surfactant, and the remainder being deionized water.
[0005] Furthermore, the alcohol is one or more combinations of ethylene glycol, polyethylene glycol, glycerol, isooctanol, or isopropanol.
[0006] Furthermore, the fluorinated substance is one or more combinations of hydrofluoric acid, ammonium fluoride, or ammonium bifluoride.
[0007] Furthermore, the etching inhibitor is one or more combinations of N,N-diisopropylethylamine, 2-hexylbenzimidazole, hydroxyethylidene diphosphate, 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxynitrile, or 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine.
[0008] Furthermore, the surfactant is one or more combinations of polyethylene glycol mono-p-tert-octylphenyl ether, polyethylene glycol-propylene glycol monobutyl ether, or coconut oil fatty acid diethanolamide.
[0009] Furthermore, the concentration of surfactants, hydrofluoric acid, and water content can regulate the etching rate of silicon dioxide and improve the surface roughness after silicon dioxide etching.
[0010] Furthermore, indium tin oxide (ITO) etching inhibitors and alcohol solvents can suppress the etching rate of amorphous indium tin oxide, making the etching rate of indium tin oxide (ITO) ≤0.03 nm / min.
[0011] Furthermore, the preferred operating temperature range of the etching solution is 0°C-60°C, more preferably 25°C-45°C, and most preferably 30°C.
[0012] The present invention has the following beneficial effects: The etching solution of this invention exhibits excellent selectivity for etching silicon dioxide. Using alcohols as solvents reduces the dissociation degree of HF, slowing down the corrosion rate of HF on amorphous ITO. Alcohol molecules can form weak interactions with the hydroxyl groups on the silicon dioxide surface, assisting the etching process. - The etching reaction of SiO2, while suppressing the corrosion of amorphous ITO, has virtually no impact on the etching efficiency of silicon dioxide, thus significantly improving selectivity.
[0013] The present invention incorporates an indium tin oxide (ITO) etching inhibitor that can form a stable chelate compound with indium tin oxide (ITO), forming a protective layer on the surface of indium tin oxide (ITO), slowing down the etching rate of indium tin oxide (ITO), and ultimately making the etching rate of indium tin oxide (ITO) ≤0.03nm / min. Detailed Implementation The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0014] Example 1 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0015] Example 2 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% polyethylene glycol (analytical grade, MW=400), 1.2% electronic-grade hydrofluoric acid (mass concentration 49.45%), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0016] Example 3 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% glycerol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0017] Example 4 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% isooctanol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0018] Example 5 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% isopropanol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0019] Example 6 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% benzyl alcohol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0020] Example 7 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% 2-hexylbenzimidazole (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0021] Example 8 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% hydroxyethylidene diphosphate (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0022] Example 9 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxynitrile (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), with the remainder being deionized water.
[0023] Example 10 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), with the remainder being deionized water.
[0024] Example 11 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% dodecyl mercaptan (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0025] Example 12 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol-propylene glycol monoether (analytical grade), and the remainder being deionized water.
[0026] Example 13 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% coconut oil fatty acid diethanolamide (analytical grade), and the remainder being deionized water.
[0027] Example 14 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 92% ethylene glycol (analytical grade), 1.2% electronic grade hydrofluoric acid (mass concentration 49.45%), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% hexadecyltrimethylammonium bromide (analytical grade), and the remainder is deionized water.
[0028] Comparative Example 1 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) is formulated the same as in Example 1, except that no alcohols are added.
[0029] Comparative Example 2 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) is formulated the same as in Example 1, except that electronic-grade hydrofluoric acid is not added.
[0030] Comparative Example 3 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) is formulated the same as in Example 1, except that the etching inhibitor N,N-diisopropylethylamine is not added.
[0031] Comparative Example 4 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) is formulated the same as in Example 1, except that the surfactant polyethylene glycol mono-p-tert-octylphenyl ether is not added.
[0032] Comparative Example 5 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 60% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0033] Comparative Example 6 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 80% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0034] Comparative Example 7 A selective etching solution for silicon dioxide and amorphous indium tin oxide (ITO) has the following formulation: 96% ethylene glycol (analytical grade), 1.2% electronic-grade hydrofluoric acid (49.45% by mass), 0.85% N,N-diisopropylethylamine (analytical grade), 0.1% polyethylene glycol mono-p-tert-octylphenyl ether (analytical grade), and the remainder being deionized water.
[0035] The etching method and result testing are as follows: Following the above formula, 100g of etching solution was prepared in a 250ml beaker equipped with a stirrer. After preparation, the solution was placed in a thermostat for temperature control. The stirring speed was 400 rpm / min, and the temperature was set at 30℃. When the solution temperature stabilized at 30±0.1℃, the corresponding structural sheet was etched. Before etching, a 50nm thick silicon dioxide sheet was cut into 2*2cm pieces and etched using an immersion etching method, with the etching time recorded. After etching, the sheet was cleaned with deionized water and dried with nitrogen gas, and the thickness was measured using an ellipsometry. Amorphous indium tin oxide (ITO) sheets (8nm thick) were etched in the same manner, and the thickness of the sheets was measured using an ellipsometry. Amorphous indium oxide (~4nm thick) and amorphous tin oxide (~5nm thick) were etched in the same manner. After etching, the sheets were cleaned with deionized water and dried with nitrogen gas, and the thickness was measured using FIB sections and TEM images. The etching rates of silicon dioxide, indium tin oxide (ITO), indium oxide, and tin oxide were calculated based on the thickness difference before and after etching and the etching time, thereby determining the corresponding selectivity. Furthermore, the etching effect of the etching solution was verified by scanning electron microscopy and atomic force microscopy, observing whether any residue remained on the metal surface after etching and whether the roughness increased. This invention adjusts the etching rate by controlling the proportions of each component in the etching solution. The experimental results of the examples and comparative examples are as follows.
[0036] Table 1. Etching effect of selective etching solution composition of silica and amorphous ITO
[0037] The etching solutions prepared in Examples 1-5 used different alcohol solvents. The selected alcohol solvents in Examples 1-5 did not show significant differences in the etching rates of SiO2 and ITO. In Example 6, benzyl alcohol was used as the solvent, resulting in a significant decrease in the etching rate of SiO2 and a marked reduction in the selectivity of SiO2 to ITO. This may be because benzyl alcohol has a stronger hydroxyl polarity, making it easier to form hydrogen bonds with HF, thus significantly reducing the mass transfer rate of HF. Simultaneously, benzyl alcohol cannot cooperate with inhibitors and surfactants on the material surface. The etching solutions prepared in Examples 1 and 7-10 used different inhibitors. These inhibitors all controlled the etching rate of amorphous ITO below 0.03 nm / min, providing a good selectivity for SiO2. Example 11 used dodecyl mercaptan as an inhibitor, but its inhibitory effect on amorphous ITO was not ideal. The etching rates of both SiO2 and ITO increased, and the selectivity decreased significantly. This may be because dodecyl mercaptan lacks a significant conjugated structure and cannot be firmly adsorbed onto the material surface. Furthermore, the hydrogen bonds formed between sulfur and hydrogen are weak and cannot synergistically interact with the solvent and HF. Examples 1, 12, and 13 used different surfactants, resulting in low surface roughness Ra values for SiO2 after etching. Example 14 used hexadecyltrimethylammonium bromide as a surfactant, significantly increasing the surface roughness Ra value of SiO2 after etching, and achieving an ITO etching rate >0.03 nm / min. This surfactant failed to form good interactions with the solvent and inhibitor, resulting in low overall selectivity. A suitable interaction between alcohol solvents, etching inhibitors, and surfactants resulted in the strongest inhibition of ITO and the highest selectivity for SiO2, with the highest selectivity for indium tin oxide (ITO) reaching 95.32.
[0038] Table 2. Etching rates of amorphous indium oxide and amorphous tin oxide by the etching solution and their selectivity to SiO2.
[0039] Examples 1, 2, 6-8, 11, 12, and 14 simultaneously etched amorphous tin oxide and amorphous indium oxide. The results are shown in Table 2. The etching rates of amorphous indium oxide and amorphous tin oxide for several formulations were much higher than those for ITO, and their selectivity was much lower than that for amorphous ITO. This may be because the films of amorphous indium oxide and amorphous tin oxide are thinner, have a higher density of surface active sites, and have more defects, which prevents the inhibitor from being uniformly adsorbed and forming a continuous protective layer, thus significantly weakening the inhibition effect. Therefore, the etching rate is much higher than that of ITO. Among them, the surface activity of indium oxide is higher than that of tin oxide, so its etching rate is slightly higher than that of tin oxide, and the corresponding selectivity is also lower.
[0040] Table 3. Etching rates, selectivity, and surface roughness after etching for silicon dioxide and amorphous indium tin oxide.
[0041] As seen in Example 1 and Comparative Example 1, when alcohols are not used as solvents, the etching rates of silicon dioxide and indium tin oxide significantly increase, and the etch selectivity decreases to 13.09. In Comparative Example 5 (60% ethylene glycol, approximately 37.85% water), Comparative Example 6 (80% ethylene glycol, approximately 17.85% water), and Comparative Example 7 (96% ethylene glycol, approximately 1.85% water), the higher the water content, the higher the etch selectivity. - Higher dissociation leads to faster SiO2 etching rates, but amorphous ITO etching rates also increase proportionally and by a greater margin, resulting in lower selectivity. Comparative Example 5 showed the highest water content and F... - The highest concentration results in the fastest etching rate and the lowest selectivity, consistent with the principle that "the higher the water content, the higher the F content." - The more HF used, the lower the selectivity. Comparative Example 2 shows that HF is the main material used for etching silicon dioxide. Examples 1 and 3 show that the etching inhibitor has a significant etching-inhibiting effect on indium tin oxide (ITO). The ITO etching inhibitor can form a stable chelate compound with ITO, forming a protective layer on the ITO surface, effectively slowing down the ITO etching rate to ≤0.03 nm / min, thus achieving a high selectivity of silicon dioxide for ITO. Examples 1 and 4 show that surfactants can effectively improve the surface roughness of silicon dioxide after etching. Obviously, the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, there are numerous variations or combinations of the above embodiments, and the present invention cannot list all embodiments. Therefore, any changes or modifications made based on the above embodiments are still within the protection scope of the present invention.
Claims
1. A selective etching solution for silicon dioxide and amorphous indium tin oxide, characterized in that, By mass percentage, it includes 85%-93% alcohols, 0.3%-3% fluorinated substances, 0.1%-3% etching inhibitors, 0.1%-1% surfactants, and the remainder is deionized water.
2. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 1, characterized in that, The alcohols mentioned are one or more combinations of ethylene glycol, polyethylene glycol, glycerol, isooctanol, or isopropanol.
3. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 1, characterized in that, The fluorine-containing substance is one or more of hydrofluoric acid, ammonium fluoride, or ammonium bifluoride.
4. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 1, characterized in that, The etching inhibitor is one or more combinations of N,N-diisopropylethylamine, 2-hexylbenzimidazole, hydroxyethylidene diphosphate, 5-oxo-4,5-dihydropyrazolo[1,5-a]pyrimidine-3-carboxynitrile, or 5-chloro-[1,2,4]triazolo[1,5-a]pyrimidine.
5. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 1, characterized in that, The surfactant is one or more of polyethylene glycol mono-p-tert-octylphenyl ether, polyethylene glycol-propylene glycol monobutyl ether, or coconut oil fatty acid diethanolamide.
6. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to any one of claims 1-5, characterized in that, The etching rate of amorphous indium tin oxide is ≤0.03nm / min.
7. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to any one of claims 1-5, characterized in that, The etching solution can be used in a temperature range of 0℃-60℃.
8. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 7, characterized in that, The etching solution can be used in a temperature range of 25℃-45℃.
9. The selective etching solution for silicon dioxide and amorphous indium tin oxide according to claim 8, characterized in that, The etching solution can be used in a temperature range of 30°C.
10. The selective etching solution of silicon dioxide and amorphous indium tin oxide according to any one of claims 1-9 is used in semiconductor, display panel and touch module materials.