CN111751491B - Method for analyzing concentration of mixed acid in silicon etching solution - Google Patents
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Abstract
The invention discloses a method for analyzing the concentration of mixed acid of silicon etching liquid, which comprises the steps of taking a mixed acid sample of nitric acid, hydrofluoric acid and acetic acid to be detected, respectively adding an aprotic organic solvent and an anti-precipitation interference solvent into the mixed acid sample to prepare a silicon etching mixed acid solution, and dropping a calibrated strong alkali aqueous solution into the silicon etching mixed acid solution through an automatic potentiometric titrator until a first sudden jump part, a second sudden jump part and a third sudden jump part appear respectively; and calculating the concentration of the mixed acid of the silicon etching solution, namely nitric acid, hydrofluoric acid and acetic acid according to the volume of the strong alkali aqueous solution consumed by the middle points of the first, second and third jump parts. The method simply, quickly and accurately measures the concentrations of the nitric acid, the hydrofluoric acid and the acetic acid contained in the silicon etching solution by a one-step method, can automatically drip the solution, automatically calculates the titration result, is efficient and quick, improves the precision, and saves time and labor.
Description
Technical Field
The invention relates to a method for analyzing the concentration of mixed acid in silicon etching solution.
Background
Silicon etching is a step important process in the fabrication and packaging of semiconductor integrated circuits. Generally, the integrated circuit manufacturing process occurs at several tens of nanometers to several microns on the surface of the wafer material, and several hundreds of processes are performed on the surface of the wafer, including back etching of silicon wafers, and the acid etchant used is mostly a mixture of strong acids (hydrofluoric acid, nitric acid, and acetic acid). An excessively high acid concentration causes over-etching, which results in insufficient driving current and poor display, and an excessively low acid concentration causes under-etching, which results in a decrease in aperture ratio, which greatly affects etching quality, and in addition, miniaturization of pattern formation width is increasingly required along with recent higher pattern formation accuracy, and thus, more stringent requirements are placed on the adjustment accuracy of the concentrations of hydrofluoric acid, nitric acid, and acetic acid.
Chinese patent CN 107796912a discloses a mixed acid of hydrofluoric acid and nitric acid diluted by an aprotic polar organic solvent (alcohol, isopropanol, acetone, tetrahydrofuran, methyl ethyl ketone or dimethyl pyrrolidone), and the concentration of hydrofluoric acid and nitric acid in the mixed acid is obtained by performing potentiometric titration on the mixed acid by a titrating agent of sodium hydroxide or potassium hydroxide solution; chinese patent CN 102778532B discloses a method for titrating the concentration of potassium hydroxide-ethanol solution or sodium hydroxide-ethanol solution as titrant, using monohydric alcohol (methanol or ethanol) and dihydric alcohol (ethylene glycol, 1, 2-propylene glycol or 1, 4-butylene glycol) as non-aqueous medium of mixed acid, to perform potentiometric titration on the mixed acid solution of nitric acid, phosphoric acid and acetic acid, however, the preparation of strong base-ethanol solution requires standing for 30 days for precipitation, which is tedious and time consuming; in addition, under the alkaline condition, ethyl acetate or methyl acetate is generated by methanol or ethanol and acetic acid, precipitates are separated out of the solution, and the generated precipitates interfere the detection electrode so as to influence the detection result. There are many methods for testing nitric acid, hydrofluoric acid and acetic acid, and for testing binary mixed acid consisting of two of the three acids, or for testing mixed acid consisting of nitric acid, hydrofluoric acid and phosphoric acid. However, the content test of the mixed acid composed of nitric acid, hydrofluoric acid and acetic acid is rarely reported, and the content test of the mixed acid is carried out by the methods of Xie nationality, Zhuqi and the like by adopting a spectroscopic breadth method to test the content of the nitric acid, utilizing the calcium fluoride precipitate generated by hydrofluoric acid to test the content of the hydrofluoric acid and testing the content of total acid by a potentiometric titration method, so as to obtain the content of the acetic acid (the three methods are combined to test the composition of the nitric acid-hydrofluoric acid-acetic acid mixed acid, Guangzhou chemical, Vol.43 No.5,2018.10).
Disclosure of Invention
1. The invention aims to provide a novel method.
The invention provides a method for analyzing the concentration of mixed acid in silicon etching solution.
2. The technical scheme adopted by the invention is disclosed.
A method for analyzing the concentration of mixed acid in silicon etching liquid is characterized by comprising the following steps:
(1) taking a mixed acid sample of nitric acid, hydrofluoric acid and acetic acid to be detected, and respectively adding an aprotic organic solvent and an anti-precipitation interference solvent into the mixed acid sample to prepare a silicon etching mixed acid solution, wherein the mass-volume ratio of the mixed acid sample to the added solvent is 0.6-1.7g:100 mL;
(2) dropping the calibrated strong alkali aqueous solution into the silicon etching mixed acid solution through an automatic potentiometric titrator until a first sudden-jump part, a second sudden-jump part and a third sudden-jump part respectively appear;
(3) calculating the concentration of the mixed acid of the silicon etching solution, namely nitric acid, hydrofluoric acid and acetic acid according to the volume of the strong alkali aqueous solution consumed by the middle point of the first, second and third jump parts
CHNO3%= 
*100%
CHF%=
*100%
CCH3COOH%=
*100%
In the formula:
c-concentration of strongly basic aqueous solution, mol/L
V1Volume of aqueous strong base consumed by the midpoint of the first jump portion, mL
V2Volume of aqueous strong base consumed by the midpoint of the second jump portion, mL
V3Volume of aqueous strong base consumed by the midpoint of the third jump portion, mL
M1Molar mass of nitric acid, g/mol [ M (HNO)3)=63.01]
M2Molar mass of hydrofluoric acid, g/mol [ M (HF) =20.01]
M1Molar mass of acetic acid, g/mol [ M (CH)3COOH))=60.05]
m-testing the mass, g, of the weighed silicon etching solution mixed acid.
Preferably, the strong alkali aqueous solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration is 0.9-1.1 mol/L.
Preferably, the strong alkali aqueous solution is calibrated by adopting HCl solution with standard concentration.
Preferably, the aprotic organic solvent is methanol or ethanol.
Preferably, the precipitation interference resistant solvent is cyclohexanol.
Preferably, the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in step (1) is 1-8: 1.
Preferably, the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in step (1) is 1-5: 1.
Preferably, the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in step (1) is 1: 1.
Preferably, three replicates are performed with three deviations per acid concentration within 0.2%, and the median of the three measurements is selected as the final measurement.
3. The technical effect produced by the invention.
(1) The method takes a strong alkaline aqueous solution as a titrant, adopts an aprotic organic solvent (methanol or ethanol) and an anti-precipitation interference solvent (cyclohexanol) as a non-aqueous medium of mixed acid, and performs potentiometric titration on the mixed acid solution of nitric acid, hydrofluoric acid and acetic acid. Under the alkaline condition, ethyl acetate or methyl acetate can be generated by methanol or ethanol and acetic acid, precipitates are separated out from the solution, and the generated precipitates interfere with a detection electrode to influence the detection result.
(2) The method simply, quickly and accurately measures the concentrations of the nitric acid, the hydrofluoric acid and the acetic acid contained in the silicon etching solution by a one-step method, can automatically drip the solution, automatically calculates the titration result, is efficient and quick, improves the precision, and saves time and labor.
Drawings
FIG. 1 is a graph of potentiometric titration.
Detailed Description
Example 1
A method for analyzing the concentration of mixed acid in silicon etching liquid comprises the following steps:
(1) preparing a strong alkaline solution with the concentration range of 0.9-1.1mol/L by using sodium hydroxide as a solute and pure water as a solvent, calibrating the concentration by using an HCl solution with a standard concentration, taking a mixed acid sample of nitric acid, hydrofluoric acid and acetic acid to be detected, and respectively adding ethanol and cyclohexanol into the mixed acid sample to prepare a silicon etching mixed acid solution, wherein the mass volume ratio of the mixed acid sample to the added solvent is 1g:100ml, the added solvent is a mixed solution of ethanol and cyclohexanol, and the volume ratio of the ethanol to the cyclohexanol is 1:1, quantifying the total volume of the mixed acid sample and the added solvent to be 100 mL;
(2) dropping the calibrated strong alkali aqueous solution into the silicon etching mixed acid solution by using an automatic potentiometric titrator until a first sudden-jump part, a second sudden-jump part and a third sudden-jump part appear respectively, as shown in figure 1;
(3) calculating the concentration of the mixed acid of the silicon etching solution, namely nitric acid, hydrofluoric acid and acetic acid according to the volume of the strong alkali aqueous solution consumed by the middle point of the first, second and third jump parts
CHNO3%= 
*100%
CHF%=
*100%
CCH3COOH%=
*100%
In the formula:
c-concentration of strongly basic aqueous solution, mol/L
V1Volume of aqueous strong base consumed by the midpoint of the first jump portion, mL
V2Volume of aqueous strong base consumed by the midpoint of the second jump portion, mL
V3Volume of aqueous strong base consumed by the midpoint of the third jump portion, mL
M1Molar mass of nitric acid, g/mol [ M (HNO)3)=63.01]
M2Molar mass of hydrofluoric acid, g/mol [ M (HF) =20.01]
M1Molar mass of acetic acid, g/mol [ M (CH)3COOH))=60.05]
m-testing the mass, g, of the weighed silicon etching solution mixed acid.
Three replicates were performed with three deviations within 0.2% for each acid concentration, and the median of the three measurements was selected as the final measurement.
Example 2
This example is essentially identical to example 1, except that the strong alkaline solution is a potassium hydroxide solution, the mass to volume ratio of the mixed acid sample to the added solvent is 1.7g:100ml, and the volume ratio of ethanol to cyclohexanol in the solvent is 8: 1.
example 3
This example is essentially identical to example 1, except that the strong alkaline solution is a potassium hydroxide solution, the mass to volume ratio of the mixed acid sample to the added solvent is 0.6g:100ml, and the volume ratio of ethanol to cyclohexanol in the solvent is 5: 1.
the above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (7)
1. A method for analyzing the concentration of mixed acid in silicon etching solution is characterized in that: the method comprises the following steps:
taking a mixed acid sample of nitric acid, hydrofluoric acid and acetic acid to be detected, and respectively adding an aprotic organic solvent and an anti-precipitation interference solvent into the mixed acid sample to prepare a silicon etching mixed acid solution, wherein the mass-volume ratio of the mixed acid sample to the added solvent is 0.6-1.7g:100 mL;
dropping the calibrated strong alkali aqueous solution into the silicon etching mixed acid solution through an automatic potentiometric titrator until a first sudden-jump part, a second sudden-jump part and a third sudden-jump part respectively appear;
calculating the concentration of the mixed acid of the silicon etching solution, namely nitric acid, hydrofluoric acid and acetic acid according to the volume of the strong alkali aqueous solution consumed by the middle point of the first, second and third jump parts
In the formula:
c-concentration of strongly basic aqueous solution, mol/L
V1Volume of aqueous strong base consumed by the midpoint of the first jump portion, mL
V2Volume of aqueous strong base consumed by the midpoint of the second jump portion, mL
V3Volume of aqueous strong base consumed by the midpoint of the third jump portion, mL
M1Molar mass of nitric acid, g/mol [ M (HNO)3)=63.01]
M2Molar mass of hydrofluoric acid, g/mol [ M (HF) =20.01]
M1Molar mass of acetic acid, g/mol [ M (CH)3COOH))=60.05]
m-testing the mass, g, of the weighed silicon etching solution mixed acid;
the aprotic organic solvent is methanol or ethanol;
the anti-precipitation interference solvent is cyclohexanol.
2. The method for analyzing the concentration of a mixed acid in a silicon etching solution according to claim 1, wherein: the strong alkali aqueous solution is sodium hydroxide solution or potassium hydroxide solution, and the concentration is 0.9-1.1 mol/L.
3. The method for analyzing the concentration of a mixed acid in a silicon etching solution as set forth in claim 2, wherein: the strong alkali aqueous solution is calibrated in concentration by adopting HCl solution with standard concentration.
4. The method for analyzing the concentration of a mixed acid in a silicon etching liquid according to any one of claims 1 to 3, wherein: the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in the step (1) is 1-8: 1.
5. The method for analyzing the concentration of a mixed acid in a silicon etching solution as set forth in claim 4, wherein: the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in the step (1) is 1-5: 1.
6. The method for analyzing the concentration of a mixed acid in a silicon etching solution as set forth in claim 5, wherein: the volume ratio of the aprotic organic solvent to the anti-precipitation interference solvent in the step (1) is 1: 1.
7. The method for analyzing the concentration of a mixed acid in a silicon etching liquid according to any one of claims 1 to 3, wherein: three replicates were performed with three deviations within 0.2% for each acid concentration, and the median of the three measurements was selected as the final measurement.
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| CN109738577A (en) * | 2019-01-10 | 2019-05-10 | 惠科股份有限公司 | Method for detecting content of mixed acid in aluminum etching solution |
| CN113358813A (en) * | 2021-06-09 | 2021-09-07 | 合肥中聚合臣电子材料有限公司 | Method for detecting composition of hydrochloric acid and ferric trichloride ITO etching solution |
| CN113759073A (en) * | 2021-09-26 | 2021-12-07 | 山西沁新能源集团股份有限公司 | Analysis and detection method for multiple components in waste liquid or recovery liquid of mixed acid |
| CN115579311B (en) * | 2022-12-02 | 2023-05-02 | 湖北江城芯片中试服务有限公司 | Mixed acid activation state control method and device, computer equipment and storage medium |
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| CN103604856B (en) * | 2013-11-15 | 2015-11-25 | 深圳市华星光电技术有限公司 | A kind of potentiometric titration method of mixed acid solution |
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