Buffer oxide etching solution with long etching life and application
By adding fluorinated fatty alcohols and polyols to the buffer oxide etching solution, a dense film and inhibitors are formed, which solves the problem of concentration changes caused by moisture loss, achieves long service life and stability of the etching solution, and reduces replacement frequency and cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-29
- Publication Date
- 2026-03-27
AI Technical Summary
Existing buffer oxide etching solutions suffer from severe water loss during etching, leading to large variations in hydrofluoric acid concentration, unstable etching rates, and increased costs due to frequent solution replacements.
By adding fluoro fatty alcohols as additives, a dense film is formed on the surface of the drug solution. Polyols act as inhibitors to bind water molecules, inhibit diffusion, and stabilize the concentration of hydrofluoric acid.
It effectively inhibits moisture loss, maintains a stable hydrofluoric acid concentration, extends the life of the etching solution, and reduces usage costs.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of etching solution technology, specifically to a buffered oxide etching solution with a long etching life and its application, which can effectively suppress moisture loss, stabilize the hydrofluoric acid concentration, and obtain a longer etching life. Background Technology
[0002] Functional electronic-grade wet chemicals are commonly used in the cleaning and etching processes during integrated circuit structure manufacturing. Wet cleaning and etching require chemicals with high quality, strong functionality, and high product precision. Buffered oxide etchant, also known as BOE etchant, is in high demand across various semiconductor manufacturing products due to the continuous upgrading of integrated circuits. Since BOE etchant contains more than half water, the heat generated during the etching reaction exacerbates water evaporation, leading to significant concentration and etching rate variations. Therefore, frequent replacement of the acid is necessary to meet etching rate requirements, which also increases costs.
[0003] CN119614202A discloses a BOE etching solution, which stabilizes the chemical composition of the etching solution and extends its service life by adding a corrosion inhibitor with the following structural formula. This solution uses fluorine-containing surfactants, which require specific synthesis processes, making synthesis difficult and costly. In contrast, the solution provided by this invention uses additives and inhibitors that are conventional chemical substances, resulting in a much lower cost. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a buffer oxide etching solution with a long etching life and its application. By using additives and inhibitors, it can effectively suppress moisture loss, stabilize the concentration of hydrofluoric acid, and obtain an etching solution with a longer etching life, thereby reducing usage costs.
[0005] The technical solution of the present invention is a buffer oxide etching solution with a long etching life, wherein the etching solution contains hydrofluoric acid, ammonium fluoride, additives and inhibitors; wherein the additives are fluorinated fatty alcohols; and the inhibitors are polyols.
[0006] Optionally, the etching solution contains, by mass percentage, 0.1-20% hydrofluoric acid, 0.1-40% ammonium fluoride, 0.001-1% additives and 0.01-1% inhibitors, with the remainder being water.
[0007] Optionally, the etching solution contains, by mass percentage, 1-8% hydrofluoric acid, 15-35% ammonium fluoride, 0.01-0.1% additives and 0.1-1% inhibitors.
[0008] Optionally, the hydrofluoric acid is electronic grade and has a mass concentration of 48-50%.
[0009] Optionally, the ammonium fluoride is electronic grade and has a mass concentration of 39-41%.
[0010] Optionally, the carbon chain length of the fluoro fatty alcohol is C10 or longer.
[0011] Optionally, the additive is any one or more of fluorododecyl alcohol, fluorotetradecyl alcohol, fluorohexadecyl alcohol and fluorooctadecanol.
[0012] Optionally, the polyol is any one or more of ethylene glycol, glycerol, butanetetraol, and xylitol.
[0013] Optionally, the etching solution contains water, which is ultrapure water with a resistivity of not less than 18 megohms at 25°C.
[0014] The present invention also relates to the application of the long-etch-life buffered oxide etchant in the cleaning or etching of silicon oxide films.
[0015] The present invention has the following beneficial effects: During the etching of oxide films in BOE wafers, the etching process is exothermic, and prolonged contact with the atmosphere leads to moisture evaporation, along with the simultaneous evaporation of hydrofluoric acid, resulting in significant fluctuations in the solution concentration and a short etching solution lifespan. This invention addresses this by adding fluorohydroxyl alcohols as additives to form a dense, non-volatile, multi-molecular film on the solution surface. This physically prevents water molecules from escaping into the air, while the inhibitor polyols bind water molecules through their polar groups, inhibiting diffusion activity. This results in minimal moisture loss and a more stable hydrofluoric acid concentration after prolonged etching, thus achieving a longer etching lifespan.
[0016] The etching solution provided in this invention contains fluorinated fatty alcohols as additives and polyols as inhibitors, used for cleaning and etching silicon oxide films in semiconductor manufacturing. Etching rate is a crucial indicator for semiconductors; a decrease in etching rate severely impacts product yield, with the most serious consequence being direct product scrap, which is extremely costly. The additives form a dense, non-volatile, multi-molecular film on the surface of the etching solution, physically preventing water and hydrofluoric acid molecules from escaping into the air. Simultaneously, the inhibitors bind water and hydrofluoric acid molecules through polar groups, inhibiting diffusion activity. This results in minimal concentration loss and more stable hydrofluoric acid concentration even after prolonged etching. Detailed Implementation
[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.
[0018] A buffered oxide etchant with a long etching life contains, by mass percentage, 0.1-20% hydrofluoric acid, 0.1-40% ammonium fluoride, 0.001-1% additives, and 0.01-1% inhibitors, with the remainder being water. The additives are fluorinated fatty alcohols; the inhibitors are polyols. Preferably, the etchant contains 1-8% hydrofluoric acid, 15-35% ammonium fluoride, 0.01-0.1% additives, and 0.1-1% inhibitors.
[0019] In some embodiments, the hydrofluoric acid is electronic grade and has a mass concentration of 48-50%.
[0020] In some embodiments, the ammonium fluoride is electronic grade and has a mass concentration of 39-41%.
[0021] In some embodiments, the carbon chain length of the fluorofatty alcohol is C10 or longer. The fluorofatty alcohol is preferably any one or more of fluorododecyl alcohol, fluorotetradecyl alcohol, fluorohexadecyl alcohol, and fluorooctadecanol. The polyol is preferably any one or more of ethylene glycol, glycerol, butanetetrate, and xylitol. Optionally, the etching solution contains water, which is ultrapure water with a resistivity of not less than 18 megohms at 25°C.
[0022] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.
[0023] Example 1 The composition of the buffer oxide etching solution in Example 1 is: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.05 wt% fluorododecyl alcohol, 0.3 wt% glycerol, and the balance is water.
[0024] Example 2 The composition of Example 2 is: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.01 wt% fluorohexadecyl alcohol, 0.1 wt% xylitol, and the balance is water.
[0025] Example 3 The composition of Example 3 is: 6 wt% hydrofluoric acid, 20 wt% ammonium fluoride, 0.05 wt% fluorotetradecyl alcohol, 0.3 wt% ethylene glycol, and the balance is water.
[0026] Example 4 The composition of Example 4 is: 3 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.05 wt% fluorotetradecyl alcohol, 0.3 wt% ethylene glycol, and the balance is water.
[0027] Example 5 The composition of Example 5 is: 3 wt% hydrofluoric acid, 20 wt% ammonium fluoride, 0.05 wt% fluorotetradecyl alcohol, 0.3 wt% ethylene glycol, and the balance is water.
[0028] Example 6 The composition of Example 6 is: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.01 wt% fluorododecyl alcohol, 0.5 wt% glycerol, and the balance is water.
[0029] Comparative Example 1 The buffer oxide etching solution consists of: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.05 wt% fluorododecyl alcohol, and the balance being water.
[0030] Comparative Example 2 The buffer oxide etching solution consists of: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 0.3 wt% glycerol, and the balance being water.
[0031] Comparative Example 3 The buffer oxide etching solution consists of: 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, 2 wt% fluorododecyl alcohol, 0.3 wt% glycerol, and the balance being water.
[0032] Comparative Example 4 The buffer oxide etching solution consists of: 3 wt% hydrofluoric acid, 20 wt% ammonium fluoride, 2 wt% fluorohexadecyl alcohol, 0.1 wt% xylitol, and the balance being water.
[0033] Comparative Example 5 The buffer oxide etching solution consists of 6 wt% hydrofluoric acid, 30 wt% ammonium fluoride, and the balance being water.
[0034] Comparative Example 6 6 wt% hydrofluoric acid, 35 wt% ammonium fluoride, 0.05 wt% fluorobutanol, 0.3 wt% glycerol, balance water.
[0035] Comparative Example 7 6 wt% hydrofluoric acid, 35 wt% ammonium fluoride, 0.05 wt% fluorododecyl alcohol, 0.3 wt% ethanol, balance water.
[0036] The etching solutions of the above embodiments and comparative examples were prepared according to the specified proportions. After preparation, they were stirred and mixed evenly. Then, the etching solutions were poured into an open PFA etching tank and kept at 23°C in a low-temperature constant temperature tank for 48 hours. The concentration of hydrofluoric acid in the etching solution before and after the time was detected, and the difference in the hydrofluoric acid concentration within 48 hours was calculated.
[0037] Table 1. Changes in hydrofluoric acid concentration after the etching solution was left exposed for 48 hours.
[0038] As shown in Table 1, in Examples 1-6, the HF concentration of the etching solution decreased by no more than 0.1% after 48 hours of placement in the etchant wound. In Comparative Example 1, which only contained additives, the hydrofluoric acid concentration changed by more than 0.1%. In Comparative Example 2, which only contained inhibitors, the hydrofluoric acid concentration changed by more than 0.2%. In Comparative Examples 3 and 4, although the hydrofluoric acid concentration changed the least, the large amount of additives resulted in a turbid and uneven state of the etching solution, which could not meet the requirements of the process. In Comparative Example 5, which contained neither additives nor inhibitors, the hydrofluoric acid concentration loss was the fastest. In Comparative Examples 6 and 7, replacing the polyol with a low-carbon fluorohydrin or omitting the polyol significantly accelerated the concentration loss.
[0039] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.
Claims
1. A buffered oxide etching solution with a long etching life, characterized in that: The etching solution contains hydrofluoric acid, ammonium fluoride, additives, and inhibitors; the additives are fluorinated fatty alcohols; and the inhibitors are polyols.
2. The long-etch-life buffered oxide etchant according to claim 1, characterized in that: By mass percentage, the etching solution contains 0.1-20% hydrofluoric acid, 0.1-40% ammonium fluoride, 0.001-1% additives and 0.01-1% inhibitors, with the remainder being water.
3. The long-etch-life buffered oxide etchant according to claim 1, characterized in that: The etching solution contains, by mass percentage, 1-8% hydrofluoric acid, 15-35% ammonium fluoride, 0.01-0.1% additives and 0.1-1% inhibitors.
4. The long-etch-life buffered oxide etchant according to claim 1, characterized in that: The hydrofluoric acid is electronic grade and has a mass concentration of 48-50%.
5. The long-etch-life buffered oxide etchant according to claim 1, characterized in that: The ammonium fluoride is electronic grade and has a mass concentration of 39-41%.
6. The long-etch-life buffered oxide etchant according to any one of claims 1 to 5, characterized in that: Fluorinated fatty alcohols have carbon chains with a length of C10 or longer.
7. The buffered oxide etchant with a long etch life according to claim 6, characterized in that: The additive is any one or more of fluorododecyl alcohol, fluorotetradecyl alcohol, fluorohexadecyl alcohol and fluorooctadecanol.
8. The long-etch-life buffered oxide etchant according to any one of claims 1 to 5, characterized in that: The polyol is any one or more of ethylene glycol, glycerol, butanetetraol, and xylitol.
9. The long-etch-life buffered oxide etchant according to any one of claims 1 to 5, characterized in that: The etching solution contains water, which is ultrapure water with a resistivity of not less than 18 megohms at 25°C.
10. The application of the long etch lifetime buffered oxide etchant according to any one of claims 1 to 9 in the cleaning or etching of silicon oxide films.