KR20210002415A - Process of cleaning metal for reducing nox - Google Patents

Abstract

The present invention relates to a cleaning method for cleaning a copper film with nitric acids, which adds hydrogen peroxide in accordance with an automated system so that NOx is 1200 to 1500 ppm. Therefore, the cleaning method can reduce the generation amount of NOx.

Description

Metal cleaning method for NOx reduction {PROCESS OF CLEANING METAL FOR REDUCING NOX}

The present invention relates to a method of cleaning a copper film with nitric acid, and more particularly, hydrogen peroxide to reduce and control the amount of NOx generated when cleaning a copper film remaining in equipment such as a chamber with nitric acid. It relates to a cleaning method in which is automatically added.

In order to recycle equipment such as sputtering again, a process of cleaning the metal film remaining in the chamber, etc., is carried out. If not cleaned at this time, the metal film attached to it will grow, but maintenance of the equipment is not performed. A step of washing the film formation is required.

Conventionally, when cleaning the metal film remaining in equipment such as a vacuum deposition chamber, nitric acid was used, because nitric acid is inexpensive and saturation for metal is high. However, when cleaning with only nitric acid, there is a problem that a large amount of NOx is generated, which adversely affects the human body or the environment, and there is a limit to controlling the amount to be less than 200ppm, which is the nitrogen oxide limit of the Air Pollution Prevention Act of the Ministry of Environment of Korea.

In this regard, when the copper film was washed only with nitric acid, about 4300 ppm, which was 10 to 20 times more than the reference value for NOx generation, was generated.

Thus, the ordinary skilled in the art treats the nitrogen oxide in a process that prevents the nitrogen oxide from going outside using a device such as a nitrogen oxide reduction scrubber, and maintains the nitrogen oxide allowable value. There was a problem that an additional process was required, and due to this, additional cost and time were incurred, and regular maintenance was required.

It is an object of the present invention to provide a cleaning method for reducing and controlling NOx generated when cleaning a copper film with nitric acid.

In order to solve the above problem, the inventors of the present invention have found that when hydrogen peroxide is added so that NOx becomes 1200 ~ 1500 ppm or less by establishing an automated system, the generation of NOx is reduced and controlled without an additional NOx removal process. It came to completion in invention.

[1] A method of cleaning a copper film with nitric acid, wherein hydrogen peroxide is added according to an automated system so that NOx is 1200 to 1500 ppm or less.

[2] The cleaning method according to claim 1, wherein the automated system includes at least one chemical liquid tank, an NOx sensor, a main controller, a hydrogen peroxide tank, and a metering pump.

[3] The method of claim 1, wherein the automated system comprises the steps of: (a) cleaning the copper film in one or more chemical baths with nitric acid; (b) measuring, by a NOx sensor, the concentration of NOx generated in the chemical bath; (c) transferring the NOx concentration measured by the NOx sensor to the main controller; (d) controlling the concentration of hydrogen peroxide in the main controller so that the measured NOx concentration is 1200 ~ 1500ppm or less; And (e) adding hydrogen peroxide of the controlled concentration from the hydrogen peroxide tank to the chemical bath by a metering pump.

[4] The cleaning method according to claim 3, wherein steps (a) to (e) are repeatedly performed until the copper film formation is cleaned.

[5] The cleaning method according to any one of claims 1 to 4, wherein the concentration of the added hydrogen peroxide is 0.1% by volume to 1% by volume.

[6] The cleaning method according to any one of claims 1 to 4, wherein the concentration of nitric acid is 20% by volume to 40% by volume.

[7] The cleaning method according to claim 3 or 4, wherein steps (a) to (e) are performed at a temperature of the chemical solution at 40 to 70°C.

[8] The cleaning method according to claim 2, wherein the automated system further comprises a scrubber.

[9] The cleaning method of claim 3, further comprising removing NOx generated through a scrubber after step (d).

In the cleaning method of the present invention, by reducing and controlling the amount of NOx generated, it is possible to shorten the cleaning time for copper film formation, reduce base metal corrosion, and recycle the cleaning liquid. In addition, since an additional process for treating nitrogen oxides is not required, the cost and time can be reduced.

1 is a block diagram of an automated system for adding hydrogen peroxide to reduce and control NOx generated during copper film formation cleaning.
2 shows an NOx sensor measuring the amount of NOx generated during nitric acid washing.
3 shows the position of the NOx sensor installed inside the chemical liquid tank of the embodiment.
4 shows a chemical bath before and after washing.
5 shows before and after cleaning of the anode bar weld.
6 shows before and after cleaning the aluminum base material cap (Cap).

Hereinafter, a method for cleaning a copper film according to an exemplary embodiment will be described in more detail.

In the present invention, "chemical liquid" refers to a solution for cleaning copper film formation as nitric acid and/or hydrogen peroxide present in the chemical liquid tank.

In the present invention, “%” refers to a% of the total volume of the chemical solution and means volume %.

In the present invention, when cleaning a copper film with nitric acid, hydrogen peroxide is added according to an automated system so that the permissible level of nitrogen oxide generation standard set by the Ministry of Environment of the Republic of Korea is 200 ppm or less, i. It is about how to make it.

The automated system may include a chemical liquid tank (1, 2), a main controller (3), an NOx sensor (6, 7, 8), a metering pump (4, 5), and a hydrogen peroxide tank (10).

The chemical bath (1, 2) is a place to clean the contaminated copper film formation with a chemical solution, for efficiency, it may be one or more, preferably two or more.

The NOx sensor (6, 7, 8) may be located inside the chemical liquid tank, preferably a place leading from the chemical liquid tank to the hood, or in a scrubber, and measure the NOx concentration generated in the chemical liquid tank or the scrubber.

The main controller 3 can control the concentration of hydrogen peroxide so that the NOx concentration is 1200 ~ 1500ppm or less, preferably 1300ppm or less by receiving the NOx concentration measured by the NOx sensor inside the chemical tank. A signal of controlled concentration can be delivered to the hydrogen peroxide tank 10 and can be located on the sides of the NOx sensors 6, 7, 8.

The hydrogen peroxide tank 10 may receive a concentration signal from the main controller 3, and may form a controlled concentration of hydrogen peroxide according to the received signal.

The metering pumps 4 and 5 can add hydrogen peroxide of a concentration controlled by the main controller 3 from the hydrogen peroxide tank 10 to the chemical baths 1 and 2. The moving speed of the added hydrogen peroxide may be 10 to 30 ℓ/min, preferably 20 ℓ/min.

The automated system includes the steps of: (a) cleaning copper film formation in one or more chemical baths with nitric acid; (b) measuring, by an NOx sensor, the concentration of NOx generated in the chemical bath; (c) transferring the NOx concentration measured by the NOx sensor to a main controller; (d) controlling, by the main controller, the concentration of hydrogen peroxide so that the measured NOx concentration is 1200 to 1500 ppm or less; And (e) adding hydrogen peroxide of the controlled concentration from the hydrogen peroxide tank to the chemical bath by a metering pump.

solution Chemical reaction Stage 1 HNO ₃ Cu + HNO ₃ → Cu(NO ₃ ) ₂ + H ₂ O + NO, NO ₂ Step 2 H ₂ O ₂ 2NO + 3H ₂ O ₂ → 2HNO ₃ + 2H ₂ O
2NO ₂ + H ₂ O ₂ → 2HNO ₃

In the step (a), copper becomes copper nitrate by nitric acid and is dissolved in a chemical solution, and NOx such as NO and NO ₂ may be generated (Table 1, step 1). The concentration of the generated NOx can be measured by the NOx sensor.

In addition, the concentration of NOx measured in steps (c) and (d) is transmitted to the main controller, and the main controller controls and quantifies the concentration of hydrogen peroxide so that the concentration of NOx is 1200 ~ 1500ppm or less, preferably 1300ppm or less. Hydrogen peroxide can be added to the chemical liquid tank from the hydrogen peroxide tank by a pump. In the step (e), NOx can react with hydrogen peroxide to form water and nitric acid (Tables 1 and 2).

By the steps (a) to (e), the amount of NOx generated is reduced to 1200 ~ 1500ppm or less, and can be adjusted so as not to exceed 1200 ~ 1500ppm.

Steps (a) to (e) are repeatedly performed until the copper film formation is cleaned.

Since the added hydrogen peroxide is decomposed and disappeared by reaction with NOx, the copper film formation is cleaned by nitric acid, so that the amount of NOx generated can be increased again. At this time, it is possible to repeat the addition of hydrogen peroxide by a metering pump so that the concentration of NOx becomes less than a certain amount.

The concentration of hydrogen peroxide to be added may be preferably 0.1% to 1%, more preferably 0.3% to 0.7%, and most preferably 0.5%. When the concentration of hydrogen peroxide is 0.1% or less, NOx generated during nitric acid washing may not be sufficiently reduced, and when the concentration of hydrogen peroxide is 1% or more, an oxide film is formed on the copper film to form a passive form.

It means until the copper film formation is completely removed until the copper film formation is cleaned. Steps (a) to (e) may be repeatedly performed until all remaining copper film formation is gone.

The concentration of nitric acid is preferably 20% to 40%, more preferably 25% to 35%, and most preferably 30%. When the concentration of nitric acid is 20% or less, the cleaning speed may decrease, and when the concentration of nitric acid is 40% or more, there may be a problem of high cleaning power but high cost.

The temperature at which steps (a) to (e) are performed is preferably 40°C to 70°C. The appropriate temperature can be determined as needed by other process conditions and factors. When the temperature of the chemical solution increases, the cleaning solution may boil and overflow, and when the temperature of the chemical solution decreases, the reactivity of hydrogen peroxide may decrease.

The automated system may further include a scrubber. The automated system may further include a step of removing NOx generated through a scrubber after step (e).

The scrubber is used to collect and purify NOx and then discharge the purified air to the atmosphere, and may preferably be a wet scrubber. In the present invention, in order to further reduce the generation of NOx, a scrubber may be additionally used.

The automation system can be connected to a computer or mobile device, thereby allowing a user to monitor in real time.

The NOx sensor, the main controller, the hydrogen peroxide tank, and the like used in the automation system may transmit signals by wire or wirelessly.

Hereinafter, specific examples of the present invention and results of the effects thereof are presented. However, the examples described below are only intended to specifically illustrate or describe the present invention, and thus the present invention is not limited.

Example

In the following, a total of five evaluations were performed, and the experiments and evaluations thereof are summarized in Tables 2 and 3 below.

In this example, “%” refers to a% of the total volume of the chemical solution and means volume %.

1st evaluation 2nd evaluation 3rd evaluation purpose Nox reduction evaluation Nox reduction evaluation Temperature control effect Nitric acid concentration 30.1% → 34.5% increase 30.3% → 33.9% increase 30.9% → 33.7% increase Chemical liquid temperature 40℃→59℃ rise 40℃ → 89℃ increase 40℃ → 64℃ rise Cleaning time 170 minutes 80 minutes 180 minutes When Nox occurs H ₂ O ₂ input when 1300 ppm occurs H ₂ O ₂ input when 1300 ppm occurs H ₂ O ₂ input when 1300 ppm occurs H ₂ O ₂ input cycle About 20 minutes About 10 to 15 minutes About 40 minutes Amount of nitric acid solution 120L 1500L (12.5 times the 1st car) 2500L
(20.8 times the first order) Copper sheep 4.6kg 85kg (18.5 times the first car) 83kg
(18 times the first order) Copper surface area 0.236㎡ 4.807㎡ (1st 20.4 times) 4.807㎡
(20.4 times the first order)

4th evaluation 5th evaluation purpose Base metal corrosion evaluation Chemical solution recycling evaluation Nitric acid concentration 30.1% → 31.1% increase 33.7% → 35.7% increase Chemical liquid temperature 40℃ → 44℃ rise 1st: 40℃→43℃
2nd: 43℃→60℃ Cleaning time 90 minutes 300 minutes When Nox occurs H ₂ O ₂ input when 1300 ppm occurs H ₂ O ₂ input when 1300 ppm occurs H ₂ O ₂ input cycle - About 60 minutes Amount of nitric acid solution 2500L (20.8 times the first car) 2500L (20.8 times the first car) Amount of copper 7kg 55kg (12 times the first car) Copper surface area 4.257㎡ 3.204㎡ (13.6 times the first)

1st evaluation

In Example 1, the concentration of generated NOx was measured by the NOx sensor while washing the copper film formation in a chemical bath with 120L of a 30% nitric acid solution. When the measured concentration of NOx was 1300 ppm, the concentration of hydrogen peroxide was controlled by the main controller, and hydrogen peroxide of the controlled concentration was automatically added by the metering pump. At this time, the controlled concentration of hydrogen peroxide was 0.5%. In Comparative Example 1, the copper film formation was cleaned in the same manner as in Example 1, except that hydrogen peroxide was added in Example 1 above.

The chemical solution temperature, cleaning time, NOx generation amount, hydrogen peroxide input cycle, and copper cleaning amount of Example 1 and Comparative Example 1 were measured, and the results are shown in Table 4 below, and the NOx generation amount of Example 1 and Comparative Example 1 It is shown in Reference Figure 1 and Reference Figure 2, respectively.

Example 1 Comparative Example 1 Chemical liquid temperature 40℃ → 59℃ increase 40℃ Cleaning time 3 hours 6 hours Nox generation amount When 1300ppm occurs, add H ₂ O ₂ 4300ppm or more Hydrogen peroxide input cycle About 20 minutes (5 times) - Chemical liquid 120L Amount of copper 4.6kg

[Reference Figure 1]

[Reference Figure 2]

As can be seen from Table 4 and Reference Figures 1 and 2, in Example 1, when washing with nitric acid, hydrogen peroxide at a concentration of 0.5% was automatically added after 20 minutes, thereby reducing the amount of NOx generated. . On the other hand, in Comparative Example 1, hydrogen peroxide was not added, so that the generation amount of NOx was maintained at 4300 ppm or more.

The cleaning time of Example 1 was also about 170 minutes, which could be reduced by about 1/2 compared to Comparative Example 1.

For reference, in Example 1, the temperature of the chemical solution was increased by about 20°C because the amount of the chemical solution was insufficient compared to the amount of copper.

2nd evaluation

In Example 2, the concentration of generated NOx was measured by the NOx sensor while washing the copper film formation in a chemical bath with 1500 L of a 30% nitric acid solution. When the measured concentration of NOx was 1300 ppm, the concentration of hydrogen peroxide was controlled by the main controller, and hydrogen peroxide of the controlled concentration was automatically added by the metering pump. At this time, the controlled concentration of hydrogen peroxide was 0.5%.

The hydrogen peroxide chemical solution temperature, cleaning time, NOx generation amount, hydrogen peroxide input cycle, and copper cleaning amount were measured, and the results are shown in the secondary evaluation of Table 2, and the NOx generation amount of Example 2 is shown in Reference Figure 3. Meanwhile, the bath before and after washing is shown in FIG. 3.

[Reference Figure 3]

As can be seen from Figure 3, in Example 2, when washing with nitric acid, hydrogen peroxide at a concentration of 0.5% was automatically added at the time of about 10 to 15 minutes, thereby reducing the amount of NOx generated, and cleaning time It could also be shortened to about 80 minutes.

For reference, the amount of copper in Example 2 is 85 kg (an increase of 12.5 times compared to Example 1), and the amount of the chemical liquid is 1500 L (an increase of 18.5 times compared to Example 1). It rose significantly from 40°C to 89°C.

3rd evaluation

In Example 3, while washing the copper film formation in a chemical bath with 2500 L of a 30% nitric acid solution, the concentration of generated NOx was measured with an NOx sensor. When the measured concentration of NOx was 1300 ppm, the concentration of hydrogen peroxide was controlled by the main controller, and hydrogen peroxide of the controlled concentration was automatically added by the metering pump. At this time, the controlled concentration of hydrogen peroxide was 0.5%.

The temperature of the chemical solution of Example 3, the cycle of adding hydrogen peroxide, and the amount of copper cleaning were measured, and the results are shown in the third evaluation in Table 2, and the NOx generation amount of Example 3 is shown in Reference Figure 4.

[Reference Figure 4]

As can be seen from Reference Figure 4, in Example 3, hydrogen peroxide at a concentration of 0.5% was automatically added at the time of about 40 minutes, thereby reducing the amount of NOx generated, and the cleaning time for copper film formation was also about 180 minutes. Could be shortened.

For reference, in Example 3, compared to Example 2, the amount of the chemical solution was increased, and it can be seen that the temperature of the chemical solution was increased from 40°C to 64°C.

4th evaluation

In Example 4, the concentration of generated NOx was measured by the NOx sensor while washing the copper film formation in a chemical bath with 2500 L of a 30% nitric acid solution. When the measured concentration of NOx was 1300 ppm, the concentration of hydrogen peroxide was controlled by the main controller, and hydrogen peroxide of the controlled concentration was automatically added by the metering pump. At this time, the controlled concentration of hydrogen peroxide was 0.5%.

The temperature of the chemical solution of Example 4, the cycle of adding hydrogen peroxide, and the amount of copper cleaning were measured, and the results are shown in the fourth evaluation in Table 3, and the NOx generation amount of Example 4 is shown in Reference Figure 5 below.

In Comparative Example 2, the copper film formation was cleaned in the same manner as in Example 4, except that hydrogen peroxide was added in Example 4 above.

[Reference Figure 5]

As can be seen in Reference Figure 5, in Example 4, hydrogen peroxide at a concentration of 0.5% was automatically added, thereby reducing the amount of NOx generated, and the cleaning time was also reduced to about 90 minutes.

In Example 4, the anode bar weld was not corroded, but Comparative Example 2 was corroded. In addition, Example 4 was not significantly different from Comparative Example 2 in the degree of corrosion of the aluminum base cap (Cap). From FIGS. 5 and 6, the degree of corrosion of the anode bar weld and the aluminum base cap can be confirmed.

5th evaluation

In Example 5, while washing the copper film formation in a chemical bath with 2500 L of a 30% nitric acid solution, the concentration of generated NOx was measured with an NOx sensor. When the measured concentration of NOx was 1300 ppm, the concentration of hydrogen peroxide was controlled by the main controller, and hydrogen peroxide of the controlled concentration was automatically added by the metering pump. At this time, the controlled concentration of hydrogen peroxide was 0.5%.

The temperature of the chemical solution of Example 5, the cycle of adding hydrogen peroxide, and the amount of copper cleaning were measured, and the results are shown in the fifth evaluation in Table 3, and the NOx generation amount of Example 5 is shown in Reference Figure 6 below.

[Reference Figure 6]

As can be seen in Reference Figure 6, in Example 5, hydrogen peroxide at a concentration of 0.5% was automatically added, thereby reducing the amount of NOx generated, and the cleaning time for copper film formation was also reduced to about 300 minutes.

When the chemical solution is recycled, the concentration of nitric acid in the chemical solution decreases, resulting in weak cleaning power. Accordingly, when the chemical solution is recycled, the cleaning power of copper is improved by increasing the temperature of the chemical solution by heating or the like.

Claims (6)

A cleaning method for cleaning a copper film with nitric acid, comprising adding hydrogen peroxide according to an automated system so that NOx becomes 1500 ppm or less,
The automation system,
(a) washing the copper film formation with nitric acid in one or more chemical baths;
(b) measuring, by a NOx sensor, the concentration of NOx generated in the chemical bath;
(c) transferring the NOx concentration measured by the NOx sensor to a main controller;
(d) controlling the concentration of hydrogen peroxide so that the NOx concentration measured by the main controller becomes 1500 ppm or less; And
(e) adding hydrogen peroxide of the controlled concentration from the hydrogen peroxide tank to the chemical liquid tank by a metering pump; and
A cleaning method in which the concentration of hydrogen peroxide added is 0.1% by volume to 1% by volume. The method of claim 1,
A cleaning method, characterized in that the steps (a) to (e) are repeatedly performed until the copper film formation is cleaned. The method according to claim 1 or 2,
Cleaning method, characterized in that the concentration of the nitric acid is 20% by volume to 40% by volume. The method according to claim 1 or 2,
The cleaning method, characterized in that the steps (a) to (e) are carried out at a temperature of a chemical solution of 40 to 70°C. The method of claim 1,
Cleaning method, characterized in that the automated system further comprises a scrubber. The method of claim 1,
After the step (d), the cleaning method further comprises removing the generated NOx through a scrubber.

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