KR20230099786A - Eco-friendly Surface Cleaning Method Using Hydrothermal Reaction - Google Patents

Abstract

Since the present invention uses a hydrothermal reaction, it has high-efficiency cleaning characteristics compared to the conventional wet cleaning process, thereby minimizing the use of relatively low-concentration cleaning liquid and ultra-pure water, and the generation of acid and base wastewater according to conventional methods is suppressed. It is about a method of cleaning the surface. The present invention has excellent cleaning performance for metal oxides even when using a cleaning solution containing an organic acid rather than a conventional cleaning solution containing inorganic acid and base chemicals having high reactivity through a hydrothermal reaction, thereby generating strong acid or strong base wastewater. There is no concern about environmental pollution due to this, and the cost of wastewater treatment is low.

Description

Eco-friendly surface cleaning method using hydrothermal reaction {Eco-friendly Surface Cleaning Method Using Hydrothermal Reaction}

The present invention relates to an environmentally friendly surface cleaning method using a hydrothermal reaction.

The surface cleaning method applied to the manufacture of semiconductors and flat panel display devices requires active response through the development of a new highly efficient cleaning process due to limitations in yield improvement and environmental problems caused by the use of a cleaning solution. For example, semiconductors and flat panel displays are manufactured through complicated processes, and in this process, the surface of a semiconductor substrate such as a silicon wafer is contaminated with metal oxide. If the subsequent process proceeds without removing oxides of alkali metal, Fe, Al, Cu, Cr, or Ni from the surface of the semiconductor substrate, the semiconductor device may be fatally deteriorated, which may cause structural distortion of the semiconductor device and It induces deterioration of electrical characteristics and causes deterioration of device performance, reliability, and yield.

Surface cleaning in the semiconductor manufacturing process is divided into wet cleaning and dry cleaning. Dry cleaning has a problem of lower detergency compared to wet cleaning, so wet cleaning is widely used. The wet cleaning has the advantage of being able to apply various types of chemicals according to the contaminants to be removed, and has excellent reliability and excellent reproducibility. A large amount of inorganic acid and base chemicals are used to remove metal oxides through wet cleaning. Inorganic acid and base chemicals used in the cleaning may cause environmental contamination if discharged without treatment. Therefore, the wet cleaning method has a disadvantage in that cost for treating inorganic acid and base wastewater is required. Therefore, compared to the conventional wet cleaning process, the use of ultra-pure water is small, so the generation of acid and base wastewater is suppressed. Demand for an eco-friendly cleaning solution using the cleaning solution and high efficiency cleaning technology that can have high space efficiency based on high cleaning efficiency is on the rise.

A hydrothermal reaction refers to a mineral synthesis or alteration reaction performed in the presence of high-temperature water, particularly high-temperature and high-pressure water. Liquid water can hardly exist in a high-temperature reaction under normal pressure, but liquid water can exist at high pressure, so a unique reaction occurs. In addition, in high-pressure water vapor, especially water above the critical temperature, many oxides, including silica and alumina, are significantly dissolved, and the reaction rate is accelerated, such as in liquid or gas phase reactions.

Therefore, it is believed that the use of the hydrothermal process can dissolve and remove metallic oxides present on the surface while minimizing the amount of inorganic acid and base chemicals used.

The patents and references mentioned herein are incorporated herein by reference to the same extent as if each document were individually and expressly specified by reference.

Korea Patent Publication 2012-0005987

The present invention uses a hydrothermal reaction, so it minimizes the concentration of cleaning components according to the increase in cleaning efficiency compared to the conventional wet cleaning process and suppresses the amount of ultrapure water, thereby reducing the generation of acid and base wastewater. To provide an eco-friendly surface cleaning method do.

Other objects and technical features of the present invention are presented more specifically by the following detailed description, claims and drawings.

The present invention is a surface cleaning method using a hydrothermal reaction, comprising: a first step of mixing a substrate whose surface is contaminated with a metal oxide and an organic acid cleaning solution; and a second step of removing the metal oxide from the surface of the substrate by performing a hydrothermal reaction at a pressure of 5 to 30 bar and a temperature of 110 to 180 ° C.

The metal oxide is characterized in that aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide II (CuO), and the organic acid cleaning solution is 0.01 to 1 M citric acid aqueous solution or 0.005 to 0.05 M EDTA (ethylene diamine tetraacetic acid) is characterized in that it is an aqueous solution.

The present invention relates to an eco-friendly surface cleaning method in which the generation of acid and base wastewater is suppressed because a hydrothermal reaction is used, so a lower concentration of the cleaning solution is used compared to the conventional wet cleaning process, and the amount of ultrapure water used is small. The present invention has excellent cleaning performance for metal oxides even when using a cleaning solution containing an organic acid rather than a conventional cleaning solution containing inorganic acid and base chemicals having high reactivity through a hydrothermal reaction, thereby generating strong acid or strong base wastewater. There is no concern about environmental pollution due to this, and the cost of wastewater treatment is low.

1 shows the solubility of aluminum oxide (Al ₂ O ₃ ) according to the concentration and temperature of citric acid according to the present invention.
2 shows the solubility of iron oxide (Fe ₂ O ₃ ) according to the concentration and temperature of citric acid according to the present invention.
Figure 3 shows the solubility of copper II oxide (CuO) according to the EDTA concentration and temperature of the present invention.
Figure 4 shows the solubility of copper II (CuO) according to the temperature by varying the concentration of the EDTA aqueous solution of the present invention.
Figure 5 shows the solubility of copper II oxide (CuO) according to the citric acid concentration and temperature of the present invention.
Figure 6 shows the solubility of copper II (CuO) according to the temperature by varying the concentration of the aqueous solution of citric acid according to the present invention.
Figure 7 shows the results of measuring the change in CuO dissolution rate in aqueous solutions using various chelating agents composed of organic acids of the present invention.

The present invention is a surface cleaning method using a hydrothermal reaction, comprising: a first step of mixing a substrate whose surface is contaminated with a metal oxide and an organic acid cleaning solution; and a second step of removing the metal oxide from the surface of the substrate by performing a hydrothermal reaction at a pressure of 5 to 30 bar and a temperature of 110 to 180 ° C.

The hydrothermal reaction is a reaction for eluting metal oxides under conditions of high temperature/high pressure, and has the advantage of improving the elution rate of metal oxides without using strong acids or strong bases. In the present invention, since a hydrothermal reaction is used, a cleaning solution containing an organic acid is used instead of a conventional cleaning solution containing a strong acid or strong base. The organic acid refers to an acidic organic compound, and is preferably citric acid and ethylene diamine tetraacetic acid (EDTA).

The eco-friendly surface cleaning method using the hydrothermal reaction of the present invention performs a hydrothermal reaction at a pressure of 5 to 30 bar and a temperature of 110 to 180 ° C. When the pressure is lower than 5 bar (0.5 MPa) and 110° C., the metal oxide on the surface of the substrate may not be completely removed because the metal oxide is not sufficiently eluted using the organic acid cleaning solution. Even if the pressure is higher than 30 bar (3 MPa), the reactivity of the hydrothermal reaction does not further increase, and when the reaction temperature exceeds 180 ° C, the dissolution rate of the metal oxide due to the hydrothermal reaction may rather decrease.

The metal oxide refers to a metal oxide deposited on a substrate such as silicon, and is preferably aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide II (CuO).

The organic acid aqueous solution may use 0.01 to 1M citric acid aqueous solution in the case of citric acid, and aluminum oxide (Al ₂ O ₃ ), iron oxide ( Fe ₂ O ₃ ), or a method of eluting copper oxide (CuO) can be removed. If the concentration of citric acid in the aqueous solution of citric acid is less than 0.01 M, the elution of aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide (CuO) is insufficient, and the temperature must be further increased. Even if the concentration of the aqueous solution exceeds 1 M, the elution of aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper II (CuO) is not further improved.

The organic acid aqueous solution may use 0.005 to 0.05 M EDTA aqueous solution in the case of EDTA, and aluminum oxide (Al ₂ O ₃ ) deposited on the substrate by performing a hydrothermal reaction at a pressure of 5 to 30 bar and a temperature of 110 to 180 ° C., iron oxide (Fe ₂ O ₃ ), or copper oxide II (CuO) can be removed by eluting. When the EDTA concentration of the EDTA aqueous solution is less than 0.005 M, the elution of aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide (CuO) is insufficient, and the temperature must be further increased, and the citric acid Even if the concentration of the aqueous solution exceeds 0.05 M, the elution of aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide (CuO) is not further improved.

The present invention is explained in detail through the following examples.

Example

Example 1: Removal of aluminum oxide using citric acid solution

1 shows the solubility of aluminum oxide (Al ₂ O ₃ ) according to the concentration and temperature of citric acid according to the present invention. In a hydrothermal reactor, the temperature of the aqueous citric acid solution having a concentration of 1 M was set to 70 °C, 90 °C, 110 °C, 130 °C, 150 °C, and 180 °C, and the pressure was set to 20 bar (2 MPa). Thereafter, aluminum oxide (Al ₂ O ₃ ) was treated with the same dissolution treatment time, and then the concentration of aluminum oxide (Al ₂ O ₃ ) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the analysis, it was confirmed that aluminum oxide was better dissolved in the citric acid aqueous solution as the treatment temperature increased, and it was confirmed that the solubility rapidly increased from 130℃. The above results show that when the temperature of the citric acid aqueous solution is increased in the hydrothermal process, it is possible to remove the metallic material through dissolution.

Example 2: Removal of iron oxide using citric acid solution

2 shows the solubility of iron oxide (Fe ₂ O ₃ ) according to the concentration and temperature of citric acid according to the present invention. In a hydrothermal reactor, the temperature of the aqueous citric acid solution having a concentration of 1 M was set to 70 °C, 90 °C, 110 °C, 130 °C, 150 °C, and 180 °C, and the pressure was set to 20 bar (2 MPa). Thereafter, iron oxide (Fe ₂ O ₃ ) was treated with the same dissolution treatment time, and then the concentration of iron oxide (Fe ₂ O ₃ ) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the analysis, it was confirmed that the higher the treatment temperature, the better the iron oxide was dissolved in the citric acid aqueous solution. The above results show that removal through dissolution of metallic materials is possible when the temperature is increased in the hydrothermal process using an aqueous solution of citric acid.

Example 3: Removal of Copper II Oxide Using EDTA Solution

Figure 3 shows the solubility of copper II oxide (CuO) according to the EDTA concentration and temperature of the present invention. In a hydrothermal reactor, the temperature of the EDTA aqueous solution having a concentration of 0.01 M is set to 20 ° C, 40 ° C, 60 ° C, 80 ° C, 100 ° C, 120 ° C, 140 ° C, 160 ° C, 180 ° C, or 200 ° C , the pressure was set to 20 bar (2 MPa). Thereafter, copper II (CuO) was treated with the same dissolution treatment time, and then the concentration of copper II (CuO) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the analysis, it was confirmed that the higher the treatment temperature, the better the dissolution of copper II (CuO) in the EDTA aqueous solution. The above results show that removal through dissolution of metallic materials is possible when the temperature is increased in the hydrothermal process using an aqueous solution of citric acid.

Figure 4 shows the solubility of copper II (CuO) according to the temperature by varying the concentration of the EDTA aqueous solution of the present invention.

Setting the temperature of 0.005 M EDTA aqueous solution, 0.01 M EDTA aqueous solution, and 0.05 M EDTA aqueous solution in a hydrothermal reactor to 80 ° C, 100 ° C, 120 ° C, 140 ° C, 160 ° C, 180 ° C, or 200 ° C and the pressure was set to 20 bar (2 MPa). Thereafter, copper II (CuO) was treated with the same dissolution treatment time, and then the concentration of copper II (CuO) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the experiment, when the concentration of EDTA was 0.005, 0.01, or 0.05M, it was predicted that there would be an effective CuO removal effect at a relatively high temperature by showing the highest elution at 160 ℃.

Example 4: Removal of copper oxide using citric acid solution

5 shows the solubility of copper II oxide (CuO) according to the citric acid concentration and temperature of the present invention. In a hydrothermal reactor, the temperature of an aqueous solution of citric acid with a concentration of 0.01 M is set to 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, or 200 °C, and the pressure is set to 20 bar (2 MPa). did Thereafter, copper II (CuO) was treated with the same dissolution treatment time, and then the concentration of copper II (CuO) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the analysis, the dissolution rate of CuO tended to increase as the temperature of the 0.01M aqueous solution of citric acid increased, but the dissolution rate was low at 200℃. It is believed that the above result is due to the deterioration of the dissolution characteristics of citric acid through decomposition when the decomposition temperature of citric acid is 175 ° C or higher.

Figure 6 shows the solubility of copper II (CuO) according to the temperature by varying the concentration of the aqueous solution of citric acid according to the present invention.

In a hydrothermal reactor, the temperature of the 0.005 M aqueous citric acid solution, the 0.01 M aqueous citric acid solution, the 0.05 M aqueous citric acid solution, and the 0.1 M aqueous citric acid solution are 100 ° C, 120 ° C, 140 ° C, 160 ° C, 180 ° C, or 200 ° C. °C, and the pressure was set to 20 bar (2 MPa). Thereafter, copper II (CuO) was treated with the same dissolution treatment time, and then the concentration of copper II (CuO) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. analysis results. It was confirmed that the dissolution rate also increased as the concentration of citric acid increased. Although the elution tendency of copper oxide differs depending on the molarity, if copper oxide is removed using an aqueous solution of citric acid, it is judged that the higher the molarity under the same temperature conditions, the more advantageous it is for cleaning.

Example 5: Removal of Copper Oxide Using an Organic Acid Chelating Agent Aqueous Solution

Figure 7 shows the results of measuring the change in CuO dissolution rate in aqueous solutions using various chelating agents composed of organic acids of the present invention. In a hydrothermal reactor, the temperature of aqueous solutions of various chelating agents composed of organic acids was set to 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, or 200 °C, and the pressure was set to 20 bar (2 MPa). set up Thereafter, copper II (CuO) was treated with the same dissolution treatment time, and then the concentration of copper II (CuO) eluted in the aqueous solution was measured through ICP-OES analysis and then analyzed in a graph. As a result of the experiment, it was found that there was little elution of CuO according to the temperature in the solution composed of pure distilled water (yellow graph in FIG.

Through the above results, it was confirmed that the solubility of metal oxides according to the type of organic acid and the dissolution performance according to the hydrothermal treatment temperature were differentiated. Therefore, it is judged that metal oxides can be efficiently removed by applying an environmentally friendly aqueous solution of organic acid to the hydrothermal process. .

Specific examples described in this specification are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that variations and other uses of the present invention do not depart from the scope of the invention described in the claims.

Claims (4)

In the surface cleaning method using a hydrothermal reaction,
A first step of mixing a substrate whose surface is contaminated with metal oxide and an organic acid cleaning solution; And a second step of removing the metal oxide from the surface of the substrate by performing a hydrothermal reaction at a pressure of 5 to 30 bar and a temperature of 110 to 180 ° C.
Eco-friendly surface cleaning method using a hydrothermal reaction comprising a.
The eco-friendly surface cleaning method according to claim 1, wherein the metal oxide is aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), or copper oxide II (CuO).
The eco-friendly surface cleaning method using hydrothermal reaction according to claim 1, wherein the organic acid cleaning solution is a 0.01 to 1M citric acid aqueous solution.
The eco-friendly surface cleaning method using a hydrothermal reaction according to claim 1, wherein the organic acid cleaning solution is an aqueous solution of 0.005 to 0.05M EDTA (ethylene diamine tetraacetic acid).

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