KR100816657B1 - Method for quantitatively analyzing mixed acid liquid - Google Patents

Abstract

A quantitative analysis of mixed acid liquid is provided to quantitatively analyze acid components of mixed acid liquid containing two or more acids accurately and minutely. A quantitative analysis of mixed acid liquid containing two or more acids comprises the steps of: causing a difference of acidity between two or more acids by dissolving mixed acid liquid containing a strong acid selected from nitric acid, perchloric acid, sulfuric acid or hydrochloric acid, organic acid and phosphoric acid in low-grade alcohol with a volumetric ratio of 50 to 700 and titrating the mixed acid liquid dissolved with the low-grade alcohol with a potentiometric titration method.

Description

Method for quantitative analysis of mixed acid {METHOD FOR QUANTITATIVELY ANALYZING MIXED ACID LIQUID}

1 is a graph showing the measurement results in the case of aqueous titration of a mixed acid solution with a potentiometric titrator.

FIG. 2 is a graph showing the measurement results when non-aqueous titration of a mixed solution with a potentiometric titrator. FIG.

The present invention relates to a method for quantitative analysis of mixed acid solution. Specifically, in the method for quantitative analysis of mixed acid solution containing two or more acids, the acidity of two or more types of acids is dissolved by dissolving the mixed acid solution in a non-aqueous solvent. It is an invention relating to a quantitative analysis method comprising the step of, and titrating the mixed solution dissolved in the non-aqueous solvent by potentiometric titration.

Mixed acid solutions containing two or more acids are used as etching liquids of metal components in the manufacturing process of semiconductors or liquid crystal displays. Particularly known are phosphoric acid etchant that wet-etch single and multilayer films made of Mo, Al, Mo alloy, or Al alloy, which are used as gate electrodes, source electrodes, and drain electrodes of TFTs of flat panel displays including thin film transistor liquid crystal displays. In addition to phosphoric acid, the etchant containing phosphoric acid basically contains organic acids such as nitric acid, sulfuric acid, hydrochloric acid, strong acid, and acetic acid, etc., as well as additives for improving etching characteristics, and contains water.

As described above, when the mixed solution containing two or more acids is titrated by a conventional aqueous potentiometric titration method, the acidity of the two or more acids is not clearly distinguished, and thus, the titration cannot be performed correctly. 1 shows titration results for a mixed acid solution containing phosphoric acid, nitric acid and acetic acid as an example of the aqueous potential difference titration result. In the potentiometric titration method, the position of the point of inflection in the potential difference graph is close to the position of nitric acid and phosphoric acid so that the inflection point is not clear, and the position of the potential difference caused by the secondary dissociation of phosphoric acid also overlaps with the position of inflection point caused by the titration of acetic acid There was a problem that can not analyze the exact content of each component.

For example, inorganic acids such as perchloric acid, hydrochloric acid, and nitric acid pass all protons to water in the water system and are leveled to the same intensity. Among the inorganic acids, there is no difference in acidity compared to hydrochloric acid or nitric acid in the acid or water having the strongest perchloric acid. Such a phenomenon is called a leveling effect, and these acids cannot be distinguished by an aqueous potential difference titration method. In FIG. 1, the monovalent acid dissociation strengths of nitric acid and phosphoric acid were leveled, making it difficult to distinguish the inflection point, and separation and quantification were not possible. The diacid dissociation strength of phosphoric acid was similar to that of acetic acid, making it difficult to distinguish the inflection point.

Due to the problem of the aqueous titration method of the mixed acid solution, a method of quantitatively analyzing each of them independently has been conducted to analyze the mixed acid solution in which phosphoric acid, nitric acid and acetic acid are mixed. For example, silver nitrate is directly quantified by measuring the absorbance at 302 nm using a spectrophotometer, and the phosphoric acid is heated to a temperature of 120 to 140 ° C. to evaporate relatively low boiling nitric acid and acetic acid. Phosphoric acid content was measured by the acid group titration method using the indicator, and acetic acid was obtained by measuring the total acidity of the mixed acid solution by the acid group titration method and excluding the content of nitric acid and phosphoric acid determined above. However, such a method has a disadvantage in that it is difficult to apply a method for periodically monitoring the content of the mixed solution used in the semiconductor or liquid crystal display device production process because various devices are required and analysis time is required.

As described above, the conventional quantitative analysis method for the mixed solution has an inefficient problem such as the reliability of the analysis is low, the analysis time is long, the analysis process is complicated, and various devices are required for the analysis. Therefore, there is a demand for the development of a quantitative analysis method capable of accurately analyzing the content of each component of a mixed acid solution containing two or more acids in a short time.

An object of the present invention is to provide a method capable of accurately and precisely quantitatively analyzing each acid component of a mixed acid solution containing two or more acids.

In addition, another object of the present invention is to significantly reduce the analysis time and improve the reliability of the analysis results to monitor the process conditions by periodically analyzing the content of each component of the mixed solution in the manufacturing process to which the actual mixed solution is applied. The present invention provides a method for quantitative analysis of mixed acid solution.

As a result of efforts to solve the technical problem of the present invention, the present inventors have found that the problem of the aqueous titration method can be solved by causing an acidity difference of each acid component of a mixed solution of two or more acids mixed using an appropriate non-aqueous solvent. This invention was completed.

Accordingly, the present invention relates to a quantitative analysis method comprising the following steps in a quantitative analysis method of a mixed acid solution containing two or more acids.

Dissolving the mixed acid solution in a non-aqueous solvent to cause a difference in acidity of two or more acids; And

Titrating the mixed solution dissolved in the non-aqueous solvent by potentiometric titration.

The quantitative analysis method of the mixed acid solution according to the present invention is more useful in the case of the mixed acid solution containing phosphoric acid, and more useful in the case of further containing a strong acid and a weak acid selected from nitric acid, perchloric acid, sulfuric acid or hydrochloric acid. Quantitative analysis.

Hereinafter, the present invention will be described in more detail.

At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art.

In addition, repeated description of the same technical configuration and operation as in the prior art will be omitted.

The present invention provides a method for quantitative analysis of mixed solution comprising the following steps.

Dissolving the mixed acid solution in a non-aqueous solvent to cause a difference in acidity of two or more acids; And

Titrating the mixed solution dissolved in the non-aqueous solvent by potentiometric titration.

The mixed acid solution according to the present invention may contain water, which is naturally contained in the commercially used acid, so that water is naturally contained in preparing the mixed acid solution. It is not necessary to limit the amount of water contained in the mixed acid solution, but if the amount of water is too large, it may affect the cause of the difference in acidity, so it is preferable that the amount is 50% by weight or less based on the total weight of the mixed acid solution. Although water does not need to be contained in mixed acid solution, when water is contained, it is good to set it as 0.1 to 50 weight%.

The method of quantitative analysis of the mixed acid solution according to the present invention is more useful in the case of the mixed acid solution containing phosphoric acid, in the case of phosphoric acid, the monovalent acid dissociation intensity is similar to that of nitric acid, perchloric acid, sulfuric acid or hydrochloric acid. For example, the bivalent acid sea strength is similar to the acid dissociation intensity of the weak acid. Therefore, in the case of mixed acid containing phosphoric acid, there was a problem that the content of each acid component cannot be accurately measured by an aqueous titration method. In addition, the mixed acid solution according to the present invention can be used more usefully in the case of further containing phosphoric acid and an organic acid which is a strong acid and a weak acid selected from nitric acid, perchloric acid, sulfuric acid or hydrochloric acid. The organic acid is an acid having a carboxyl group, and examples thereof include acetic acid, benzoic acid, citric acid and malic acid. In a preferred embodiment according to the present invention the mixed acid solution may contain nitric acid, phosphoric acid and acetic acid, more preferably 50 to 70% by weight of phosphoric acid, 6 to 10% by weight of nitric acid, 3 to 12% by weight of acetic acid, It may be made of water.

In the quantitative analysis method of the mixed solution according to the present invention, by selecting an appropriate non-aqueous solvent and diluting the mixed solution, the acidity of each component of the mixed solution is induced, and the mixed solution diluted in the non-aqueous solvent is titrated by potentiometric titration. At the same time it is characterized by analyzing the content of each acid component. Potentiometric titration is a method of recognizing an equivalence point using a potentiometric electrode. The titration is performed using an appropriate electrode according to an analytical sample, and the equivalence point is recognized from a potential difference (mV) curve according to a titration liquid (mL).

Suitable non-aqueous solvents are preferably lower alcohols selected from methanol, ethanol, and isopropanol, and more preferably, when methanol is used, a more accurate measurement result is shown in the phosphate-based mixed acid solution. It is preferable to dilute the non-aqueous solvent using a 50 to 700 weight ratio with respect to the mixed acid solution, more preferably 200 to 300 weight ratio. In the case of using a non-silicone-based solvent in less than 50% by weight relative to the mixed acid solution, the effect of causing a difference in acidity may be insignificant, and in many cases exceeding 700% by weight, the concentration of the acid component may be too low to facilitate titration. have. Therefore, the amount of the non-aqueous solvent is preferably adjusted in consideration of the effect of causing a difference in acidity within the above range, the concentration of a titrant such as sodium hydroxide or potassium hydroxide solution. In addition, the mixed value of the mixed solution should be within the cylinder capacity of the content analyzer so that the measured value is constant. Since there is time to make a small potential change in the electrode, which can cause errors in the measurement result, it is preferable to collect the mixed solution so that the titration is completed before the titrant in the cylinder capacity is exhausted if possible.

The titrant used in the potentiometric titration according to the present invention uses a base solution prepared at an accurate concentration, and it is preferable to use a solution in which sodium hydroxide is dissolved in a lower alcohol selected from methanol, ethanol and isopropanol.

In addition, in the case of the electrode used in the potentiometric titration according to the present invention, it is preferable to use an electrode using methanol or ethanol as the electrolyte solvent in favor of accurate quantitative analysis.

In addition, in order to obtain accurate and reproducible analysis results in the potentiometric titration according to the present invention, it is preferable that the titration rate of the titrant is 1 to 5 ml / min, the potential change is 40 to 60 mV / min, and the stabilization time is 10 to 40 seconds. In order to improve the measurement accuracy and reproducibility, it is recommended to minimize the titration speed, but 1 to 5ml / min is appropriate in consideration of the measurement time, and the potential change suddenly occurs when the titrant is dispensed into the analysis solution. If it is set high, it is difficult to accurately measure the equivalence point. On the contrary, if the value is set too low, the electrode may become unstable due to the long analysis time. Therefore, it is preferable to maintain the potential change at 40 to 60 mV / min. The stabilization time refers to the time remaining after stabilization by rapid change of potential after dispensing the titrant, and 10 sec to 40 sec is appropriate for setting to improve measurement accuracy and reproducibility. When titrating with 0.3N KOH solution in Methrohm 794 Basic Titrino titration system, titration speed is 2 ~ 3ml / min, potential change is 45mV / min ~ 55mV / min, and equilibrium time is 15sec ~ 20sec. desirable.

Hereinafter, the content analysis method of the mixed acid solution containing phosphoric acid, nitric acid and acetic acid as an embodiment according to the present invention will be described in detail.

1 is a graph showing the results of titration of the aqueous potential difference for a mixed solution consisting of phosphoric acid, nitric acid, acetic acid and deionized water, and FIG. 2 is a graph showing the results of potentiometric titration using methanol as a non-aqueous solvent for the same mixed solution as in FIG. to be.

The mixed solution used to wet-etch single and multilayer films made of Mo, Al, Mo alloy, or Al alloy used as the gate electrode, source electrode, and drain electrode of a TFT of a flat panel display including a thin film transistor liquid crystal display device is used. Phosphoric acid-based etching solution is composed of 50 to 70% by weight of phosphoric acid, 6 to 10% by weight of nitric acid, 3 to 12% by weight of acetic acid, the remainder is water.

Referring to Figure 1, the aqueous titration (Aqueous titration), that is, when the solvent is water, the phosphoric acid divalent dissociation. The acid dissociation constant of triprotic phosphoric acid (H ₃ PO ₄ ) is K _a1 : 7.11 x 10 ^-3 , K _a2 : 6.32 x 10 ^-8 , K _a3 : 7.1 x 10 ^-13 , which means that trivalent dissociation is possible. The acid dissociation constant is too small to be detected at the time of titration. In the end, phosphoric acid behaves as if 2 dissociates during titration. However, in the case of a mixed solution containing nitric acid, phosphoric acid, and acetic acid, the monovalent acid dissociation of phosphoric acid affects the titration of nitric acid, and the divalent acid dissociation affects the dissociation of acetic acid, as shown in FIG. 1. Phosphoric acid and acetic acid cannot be accurately and independently quantified.

Referring to FIG. 2, which is the result of potentiometric titration of a mixed solution containing phosphoric acid, nitric acid and acetic acid using methanol as a non-aqueous solvent, phosphoric acid under methanol, a non-aqueous solvent, does not dissociate excessively as in an aqueous solution, and only monovalent acid dissociation occurs. The monovalent acid dissociation intensity differed from that of nitric acid. In other words, it was possible to independently quantitative analysis of nitric acid and phosphoric acid by causing the acidity difference between phosphoric acid and nitric acid, and accurately analyzed the acetic acid content by preventing the dissociation of phosphoric acid 2.

The present invention will be described in more detail with reference to the following Examples. However, the following examples are merely examples of the present invention, and the claims of the present invention are not limited thereto.

<Example 1>

Quantitative analysis was carried out using a potentiometric titration method on a mixed solution consisting of 64% by weight of phosphoric acid, 8% by weight of nitric acid, 10% by weight of acetic acid and 18% by weight of deionized water.

The potentiometric titrator used for potentiometric titration was Metrohm 794 Basic Titrino, the electrode was Metrohm Solvotrode (6.0229.100 LL), and the electrolyte was an ethanol solution in which LiCl was dissolved.

The titration solution used 0.3N KOH methanol solution.

Accurately weigh 0.3 g of amidosulfuric acid to 0.1 mg in a 100 mL glass beaker, fill 80 mL of deionized water, stir to dissolve the sulfamic acid completely, and obtain a titer using the potentiometric titrator.

Accurately weigh 0.4 g of the mixed solution of the above composition to 0.1 mg in a 100 mL polyethylene (PE) beaker, fill 80 mL of methanol, and stir to dissolve the mixed solution in methanol. The solvotrode electrode was immersed in a methanol solution of a mixed acid solution, and the potential difference was measured while titrating with 0.3 N KOH methanol solution using the potentiometric titrator. At this time, the titration rate was 3 mL / min, the signal change rate was 50 mV / min, and the stabilization time was 25 seconds.

The potentiometric titration graph is shown in FIG. 2. Referring to FIG. 2, referring to the potential change and the ERC (Endpoint Recognition Criterion), the difference in titration time between the monovalent acid dissociation of nitric acid and phosphoric acid is clear. The content was able to be measured independently, and the dibasic acid dissociation of phosphoric acid hardly occurred, so that the acetic acid content could be measured accurately.

The results measured 10 times by the above method are shown in Table 1 below. According to the results of Table 1, since the standard deviation of the results of measuring the content of nitric acid and acetic acid is very low, it can be seen that the content of nitric acid and acetic acid is accurately measured in the phosphoric acid-based mixed acid solution containing a large amount of phosphoric acid.

TABLE 1

Comparative Example 1

Quantitative analysis was performed on the mixed solution of the same composition as in Example 1 by titration with an aqueous potential difference. Instead of the electrode used in the examples, a Metrohm Ag / AgCl reference electrode was used. The electrolyte of the Ag / AgCl electrode is 0.3M KCl aqueous solution. The titrant was used 0.3N NaOH aqueous solution. Potentiometric titration was performed in the same manner as in Example 1, and the resultant potential titration graph is shown in FIG. 1.

 Referring to the result of FIG. 1, the region where the titration of nitric acid and the titration of monovalent acid of phosphoric acid are made is close to each other, and thus the inflection point is not clear. Therefore, it is difficult to accurately recognize the equivalence point. In addition, in the case of acetic acid, the position of the equivalence point is similar to the position of the divalent acid equivalence point of phosphoric acid, and it becomes inaccurate whether the content obtained from the titration titration liquid contains only acetic acid or phosphoric acid.

The quantitative analysis method of the mixed solution according to the present invention has better accuracy and precision than the conventional method, and more precisely and precisely in the conventional method in the case of a mixed solution containing polymagnetic acid such as phosphoric acid. There is an advantage in obtaining the analysis result.

In addition, it is possible to measure the content of two or more acid components at the same time by using one analysis equipment, which can significantly shorten the analysis time compared to the conventional content analysis method. Therefore, it is diverse in the wet etching process during the manufacturing process of the semiconductor or liquid crystal display device. The amount of mixed solution used can be analyzed in a short time, so that the etching process can be stably maintained.

Claims (10)

In the quantitative analysis method of mixed acid solution containing two or more acids, Dissolving a mixed acid consisting of a strong acid selected from nitric acid, perchloric acid, sulfuric acid, or hydrochloric acid, and an organic acid and phosphoric acid in a lower alcohol of 50 to 700 weight ratio based on the mixed acid solution to cause a difference in acidity of two or more acids; And Titrating the mixed solution dissolved in the lower alcohol by a potentiometric titration method; Quantitative analysis method of mixed solution comprising a. The method of claim 1, The lower alcohol is a quantitative analysis method of a mixed solution selected from methanol, ethanol, isopropanol. delete delete delete The method of claim 1, The mixed solution contains phosphoric acid, nitric acid and acetic acid. The method of claim 6, The mixed solution is 50 to 70% by weight of phosphoric acid, 6 to 10% by weight of nitric acid, 3 to 12% by weight of acetic acid, the remainder is water quantitative analysis method, characterized in that consisting of water. The method of claim 1, The titrant used in the potentiometric titration method is a quantitative analysis method of a mixed acid solution, characterized in that the sodium hydroxide or potassium hydroxide dissolved in a lower alcohol selected from methanol, ethanol, isopropanol. The method of claim 8, In the potentiometric titration method, the electrolyte solvent of the electrode is quantitative analysis method, characterized in that the methanol or ethanol. The method of claim 8, In the potentiometric titration method, the titration rate is 1 to 5 ml / min, the potential change rate is 40 to 60 mV / min, the stabilization time is 10 to 40 seconds, characterized in that the quantitative analysis method.

Images