THOX and TEOS selective etching solution and application thereof

Abstract

The invention relates to the technical field of semiconductors and electronic chemicals, and particularly discloses a THOX and TEOS selective etching solution and application, the etching solution comprises the following components by mass: 80-95% of monohydric alcohol, 0.1-1.5% of polyhydric alcohol, 0.02-0.5% of hydrofluoric acid, 0.01-0.2% of organic acid, and the balance of water. According to the invention, the polyol and the organic acid are introduced as additives, so that the etching rates of THOX and TEOS can be obviously reduced, the etching rate of THOX to TEOS can be overturned, and the etching selection ratio is greater than 5. The etching liquid is stable, the contained substances are cheap and easy to obtain, the production cost can be reduced, the substance result is simple, and raw materials which are high in purity and accord with semiconductor use can be obtained on the market.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and electronic chemicals, and in particular relates to a THOX and TEOS selective etching solution and application thereof. Background Art

[0002] Silicon dioxide is an excellent insulating material that can effectively isolate the electric field between devices, prevent charge leakage and interference, and thus improve the stability and reliability of the device. 2 ) The film layer is used for semiconductor devices to protect the device surface, prevent corrosion and damage to the device by foreign substances, moisture, etc., and extend the service life of the device.

[0003] Thermal oxide film (THOX) is formed by exposing the silicon substrate to oxygen or water vapor in a high temperature environment (high temperature furnace) through oxidation reaction. A dense silicon oxide layer is formed on the surface of the thermal oxide film, which has good insulation and chemical stability. However, its thickness is usually thin and its uniformity is poor. TEOS film is formed in the process of surface chemical vapor deposition (PECVD) by introducing tetramethoxysilane (TEOS) gas or liquid mixture into the reaction chamber. TEOS is thicker than THOX and can form a thicker silicon oxide film. TEOS film has better uniformity and can be optimized by controlling process conditions, which has greater flexibility. In the process of semiconductor device manufacturing, THOX and TEOS are often required to be selectively etched. Traditional etching solutions, such as hydrofluoric acid (HF) and buffered oxide etchant (BOE), can etch thermal oxide and TEOS, but the selectivity is relatively low. Therefore, etching solutions that improve the selectivity of thermal oxide and TEOS have become an important topic in the field of semiconductor manufacturing. Summary of the invention

[0004] The invention provides a THOX and TEOS selective etching solution and application thereof, which can improve the THOX to TEOS etching selectivity ratio.

[0005] The technical solution of the present invention is to provide a THOX and TEOS selective etching solution, which contains the following components in mass percentage: 80-95% monohydric alcohol, 0.1-1.5% polyhydric alcohol, 0.02-0.5% hydrofluoric acid and 0.01-0.2% organic acid, and the balance is water.

[0006] In some embodiments, the monohydric alcohol is one or more of methanol, ethanol, propanol and isopropanol.

[0007] In some embodiments, the polyol is one or more of ethylene glycol, propylene glycol, glycerol, diethylene glycol, butylene glycol, diethylene glycol and 1,4-butanediol.

[0008] In some of the embodiments, the hydrofluoric acid is a 49 wt % hydrofluoric acid aqueous solution.

[0009] In some embodiments, the organic acid is one or more of fumaric acid, succinic acid, tartaric acid, oxalic acid, citric acid and maleic acid.

[0010] In some embodiments, the water is ultrapure water.

[0011] In some preferred embodiments, the etching solution contains 95% monohydric alcohol, 0.1-0.5% polyhydric alcohol, 0.2% hydrofluoric acid, and 0.1-0.15% organic acid.

[0012] In a more preferred embodiment, the etching solution contains 95% isopropyl alcohol, 0.1-0.5% 1,4-butanediol, 0.2% hydrofluoric acid and 0.1-0.15 tartaric acid.

[0013] The invention also relates to the application of the etching solution in improving the etching selectivity ratio of THOX and TEOS, wherein the etching ratio is greater than 5.

[0014] The present invention has the following beneficial effects: In the etching solution provided by the present invention, the proportion of alcohol is extremely high and the content of hydrofluoric acid is extremely low, which can avoid the ionization of hydrofluoric acid as much as possible. At the same time, the presence of alcoholic hydroxyl groups can also form hydrogen bonds with oxygen atoms on the surface of silicon dioxide to prevent silicon dioxide from being etched too quickly. A certain amount of polyol is added to the etching solution, which can not only provide alcoholic hydroxyl groups, but also increase the viscosity of the system to hinder the mass transfer process during etching, so that the etching rate of TEOS is lower than the etching rate of THOX, and the etching selectivity of THOX to TEOS is increased. The hydroxyl group of TEOS is usually more than that of THOX. The present invention adds organic acid additives to the etching solution, which are more combined with TEOS, and well prevents the attack of HF to avoid TEOS from being etched. This further improves the etching selectivity of the etching solution to THOX and TEOS.

[0015] The etching solution provided by the invention is stable, and the substances contained therein are cheap and easily available, so the production cost can be reduced and the etching solution is easy to popularize and apply. DETAILED DESCRIPTION

[0016] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0017] The THOX and TEOS selective etching solution provided by the invention comprises the following components by mass percentage: 80-95% of monohydric alcohol, 0.1-1.5% of polyhydric alcohol, 0.02-0.5% of hydrofluoric acid and 0.01-0.2% of organic acid, and the balance is water.

[0018] The monohydric alcohol may be one or more of methanol, ethanol, propanol and isopropanol. The polyhydric alcohol may be one or more of ethylene glycol, propylene glycol, glycerol, diethylene glycol, butylene glycol, diethylene glycol and 1,4-butanediol. The organic acid may be one or more of fumaric acid, succinic acid, tartaric acid, oxalic acid, citric acid and maleic acid.

[0019] In the following examples, hydrofluoric acid is a 49 wt % hydrofluoric acid aqueous solution, and water is ultrapure water. The ingredients and amounts of the specific examples and comparative examples are shown in Table 1.

[0020] Table 1

[0021] When preparing the etching solutions of the above embodiments and comparative examples, all raw materials are directly mixed in proportion. A 10 mm*10 mm sample was etched for 30 min in a 23°C water bath, and the thickness of the sample before and after was measured by an ellipsometer, and finally the etching rate (ER) was calculated. The specific etching results are shown in Table 2.

[0022] Table 2

[0023] Through the above examples and comparative examples, it is found that the increase of polyols will reduce the etching rates of THOX and TEOS at the same time, and the presence of organic acids will reduce the etching rate of TEOS but have almost no effect on the etching rate of THOX, thereby increasing the etching selectivity.

[0024] The high content of alcohol added in the present invention prevents the ionization of hydrofluoric acid. At the same time, the presence of alcoholic hydroxyl groups can also form hydrogen bonds with oxygen atoms on the surface of silicon dioxide to prevent silicon dioxide from being etched too quickly. The presence of polyols can also provide alcoholic hydroxyl groups and increase the viscosity of the system to hinder the mass transfer process during the etching process. This will make the etching rate of TEOS lower than the etching rate of THOX, and increase the etching selectivity of THOX to TEOS. The hydroxyl group of TEOS in the present invention is usually more than that of THOX, and the addition of organic acid additives will also combine more with TEOS, which can well prevent the attack of HF to avoid TEOS from being etched. This further improves the etching selectivity of the etching solution to THOX and TEOS, making the etching selectivity greater than 5.

[0025] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A THOX and TEOS selective etching solution, characterized in that: The etching solution contains the following components in percentage by mass: 80-95% of monohydric alcohol, 0.1-1.5% of polyhydric alcohol, 0.02-0.5% of hydrofluoric acid and 0.01-0.2% of organic acid, and the balance is water.

2. The etching solution according to claim 1, characterized in that: The monohydric alcohol is one or more of methanol, ethanol, propanol and isopropanol.

3. The etching solution according to claim 1, characterized in that: The polyol is one or more of ethylene glycol, propylene glycol, glycerol, diethylene glycol, butylene glycol, diethylene glycol and 1,4-butanediol.

4. The etching solution according to claim 1, characterized in that: The hydrofluoric acid is a 49 wt % hydrofluoric acid aqueous solution.

5. The etching solution according to claim 1, characterized in that: The organic acid is one or more of fumaric acid, succinic acid, tartaric acid, oxalic acid, citric acid and maleic acid.

6. The etching solution according to claim 1, characterized in that: The water is ultrapure water.

7. The etching solution according to any one of claims 1 to 6, characterized in that: The etching solution contains 95% monohydric alcohol, 0.1-0.5% polyhydric alcohol, 0.2% hydrofluoric acid, and 0.1-0.15% organic acid.

8. The etching solution according to any one of claims 1 to 6, characterized in that: The etching solution contains 95% isopropanol, 0.1-0.5% 1,4-butanediol, 0.2% hydrofluoric acid and 0.1-0.15% tartaric acid.

9. Use of the etching solution according to any one of claims 1 to 8 in improving the etching selectivity ratio of THOX and TEOS, wherein the etching ratio is greater than 5.

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