TWI383446B - Method for controlling etchant concentration - Google Patents

Description

Etching solution concentration control method

This case refers to a concentration control method, especially a method for controlling the concentration of an etchant.

The wet etching method using an acidic or alkaline solution has become a quite common manufacturing method in the current electronic product manufacturing process, and is applied to technical fields including display panels, semiconductors, and circuit boards. Since the etching method must maintain the concentration of the etching solution within a certain range without excessive variation, the etching rate can be stabilized and the quality of the product can be controlled. Therefore, the control method of the concentration of the etching liquid becomes an indispensable key technology in the process.

The conventional concentration control method, such as Taiwan Patent No. 1297517, is to sample the etching solution for concentration analysis at a fixed time interval, and then compare the amount of change in the concentration of the etching solution obtained by the two analyses, and then add a certain amount of the acid-base drug. The liquid keeps the concentration of the etchant stable. However, this method has its shortcomings to be overcome, for example: (1) The concentration of the initial etching solution is not easy to control. When the etching is started, it is preferable to adjust the concentration of the etching liquid to an appropriate concentration. However, the conventional technique can only add the etchant concentration to the "last measured concentration" based on the two measurement results, but if the last measured concentration is not the initial proper concentration, then the replenishing solution can never be replenished to the appropriate concentration.

(2) The acid supplement delay factor caused by the supplemental liquid pipeline is not taken into account. Those skilled in the art are aware that the etchant tends to cause blockage of the tubing and the flow velocity is affected, which in turn causes errors in the tonic, and the length of the tubing also affects the rate of replenishment. Although the conventional technique uses the estimated etchant consumption rate To replenish the liquid, try to prevent the tonic error, but the actual application is too simple, and still can not achieve the purpose of stable acid control. Therefore, it is more prone to insufficient or excessive replenishment, and it is difficult to achieve the requirement of stable tonic.

All of the above problems make it difficult to improve the quality of the product by controlling the concentration of the etching solution. Therefore, inventing a more precise method for controlling the concentration of the etching liquid has been urgently required in the art.

For the sake of the job, the applicant, based on the lack of knowledge in the prior art, has carefully tested and researched, and has a perseverance spirit, and finally conceived the "etching liquid concentration control method" in this case, which can overcome the above shortcomings. The following is the case. A brief description.

The inventor of the present invention proposed the etching liquid concentration control method of the present invention after rethinking. When the concentration of the etching solution is controlled according to the method disclosed in the present invention, it is necessary to continuously measure the concentration of the etching solution in the process, and then perform integration, differentiation, and scaling according to the difference between the measured concentration value and the desired concentration value desired by the user. The calculation method obtains the supplement amount of the acid-base liquid to carry out the medicine to maintain the concentration of the etching liquid. Since the present invention monitors the concentration change at any time, and can adjust the relevant parameters of the calculation formula according to the concentration change condition, the feedback control information can be provided immediately, so that the liquid medicine can be accurately and continuously replenished, and the concentration of the etching liquid is stabilized. The invention has the advantages of improving production efficiency and product quality.

According to the concept of the present invention, a method for controlling an etchant concentration is provided, comprising the steps of: setting a target concentration value of an etchant; measuring the etchant to obtain a measured concentration value; and determining the concentration value according to the target concentration value And calculating a difference; scaling the difference to obtain a proportional value; scaling the difference a time integral value obtains a proportional integral value; proportionalizing a time differential value of the difference to obtain a proportional differential value; and supplementing the etching solution concentration according to the proportional value, the proportional integral value, and the proportional differential value To the target concentration value.

Preferably, the method for controlling the concentration of the etching solution provided by the present invention further comprises measuring the concentration of the etching solution by using one of ion chromatography, one titration and one spectral analysis.

Preferably, the etchant concentration control method provided by the present invention, wherein the titration method extracts an etchant sample from the etchant by a micropump.

Preferably, the etchant concentration control method provided by the present invention further comprises selecting a diluent from the group consisting of propylene glycol, glycerin and isopropyl alcohol to dilute the etchant sample.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a first range, the proportional integral value is zero.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a second range, the proportional differential value is zero.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a third range, the proportional differential value is a negative value.

Preferably, the method for controlling the concentration of an etchant provided by the present invention, wherein the etchant is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonia.

Preferably, the method for controlling the concentration of an etching solution provided by the present invention, wherein the etching liquid is selected from the group consisting of hydrochloric acid, hydrofluoric acid, nitric acid, acetic acid, phosphoric acid, and sulfuric acid.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the target concentration value is greater than the measured concentration value, increasing the The etchant concentration is to the target concentration value.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the target concentration value is less than the measured concentration value, reducing the etchant concentration to the target concentration value according to the difference.

According to the concept of the present invention, a method for controlling the concentration of an etching solution is provided, comprising the steps of: monitoring a concentration change value of an etching solution; and proportionalizing the concentration change value to obtain a proportional value; and prolonging the concentration change value for a time. The integral value is obtained as a proportional integral value; a time differential value of the concentration change value is proportional to obtain a proportional differential value; and the etching liquid is supplemented according to the proportional value, the proportional integral value and the proportional differential value.

Preferably, the etchant concentration control method provided by the present invention further includes setting a first concentration value of the etchant, measuring the etchant to obtain a second concentration value, and according to the first concentration value and the second The concentration value is obtained to obtain the concentration change value.

Preferably, the method for controlling the concentration of the etching solution provided by the present invention further comprises measuring the concentration of the etching solution by using one of ion chromatography, one titration and one spectral analysis.

Preferably, the etchant concentration control method provided by the present invention, wherein the titration method extracts an etchant sample from the etchant by a micropump.

Preferably, the etchant concentration control method provided by the present invention further comprises selecting a diluent from the group consisting of propylene glycol, glycerin and isopropyl alcohol to dilute the etchant sample.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a first range, the proportional integral value is zero.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a second range, the proportional differential value is zero.

Preferably, the etchant concentration control method provided by the present invention further comprises: when the time differential value falls within a third range, the proportional differential value is a negative value.

Preferably, the method for controlling the concentration of an etchant provided by the present invention, wherein the etchant is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonia.

Preferably, the method for controlling the concentration of an etching solution provided by the present invention, wherein the etching liquid is selected from the group consisting of hydrochloric acid, hydrofluoric acid, nitric acid, acetic acid, phosphoric acid, and sulfuric acid.

Preferably, the etchant concentration control method provided by the present invention, wherein the proportional value is a product of the concentration change value and a first fixed number, wherein the proportional integral value is a product of the time integral value and a second fixed number The proportional differential value is the product of the time differential value and a third fixed number.

In accordance with the teachings of the present invention, an apparatus capable of implementing the above method is presented.

The present invention will be fully understood by the following examples, which can be implemented by those skilled in the art, and the implementation of the present invention may not be limited by the following embodiments.

Please refer to the first figure, which is a schematic diagram of an etchant concentration analysis and control device matched with the method of the present invention. The etch machine side 1 is generally a conventional etch machine structure including an etchant tank 10, a circulation pump 11, and a circulation line 12. The etching liquid tank 10 is used for storing an etching liquid for performing an etching reaction, and the etching liquid in the etching liquid tank 10 contains a conventional alkaline solution such as sodium hydroxide, potassium hydroxide or ammonia, and a mixed solution thereof, and, for example, hydrochloric acid and hydrofluoric acid. Acid, nitric acid, acetic acid, A solution of a conventional acidic solution such as phosphoric acid or sulfuric acid and a mixed solution thereof. The circulation pump 11 is for withdrawing the etching liquid after the etching reaction, and returns it to the etching liquid tank 10 through the circulation line 12 to repeat the etching reaction.

The concentration analysis and control side 2 includes a liquid medicine tank 20, a dosing machine 21, and an analyzer 22. The analyzer 22 is connected to an analysis line 23, and the analysis line 23 is connected to the circulation line 12, so that the etching liquid flowing in the circulation line 12 can be extracted by the analyzer 22 by a micro pump (not shown). The extracted etchant samples are analyzed in the analyzer 22. The chemical liquid tank 20 is provided with a chemical liquid for supplementing the etching liquid in the etching liquid tank 10, and the dosing machine 21 sends the chemical liquid according to the instruction of the analyzer 22, and the control tube connected to the etching liquid tank 10 via the dosing machine 21 is provided. The liquid 24 replenishes the chemical solution to the etching solution tank 10.

It should be particularly noted that the dosing machine 21 can be connected to a plurality of liquid medicine tanks 20 (not shown), and can be supplemented with different kinds of liquid medicines as needed, for example, when the concentration of the etching liquid is too high, water can be replenished. To reduce the concentration of the etching solution.

Since the flow rate of the etchant in the circulation line 12 is slow, the micropump needs to be disposed in the analyzer 22 to extract the etchant sample more efficiently through the analysis line 23, and to reduce bubble generation for analysis. The analyzer 22 can dilute the extracted etchant sample by adding an alcohol such as ethylene glycol, propylene glycol, glycerin or isopropanol as a diluent, wherein the propylene glycol is non-toxic and is a preferred choice. The equivalent concentration of each acidic radical in the etchant sample composed of, for example, an acidic or alkaline mixed solution is measured by a non-aqueous acid-base neutralization titration method to obtain a measured concentration value. Of course, in addition to measuring the concentration by titration, the analyzer can also use ion chromatography or spectroscopic analysis to measure the concentration values of the main components in the etching solution.

In the present invention, the analyzer 22 can be preset and can be changed as needed The target concentration of the etchant, but usually set before the start of the etch process or before the etchant concentration is measured for the first time. Those skilled in the art will determine the target concentration value of a preferred range of preferred reactions through appropriate selection and selection, and thus the target concentration value may also be set to a range interval, but the embodiment of the present invention will target The concentration value is stated by a certain value. The target concentration value is used as a basis for comparison with the measured concentration value when the etching reaction is performed.

In addition, after the analyzer 22 obtains the measured concentration value, the measured concentration value is compared with the target concentration value, and if the measured concentration value is greater than the target concentration value, the analyzer 22 according to the amount A difference P between the measured concentration value and the target concentration value indicates that the dosing machine 21 replenishes the water or stops the replenishing process to reduce the concentration of the etching solution in the etching solution tank 10, so that the concentration of the etching solution in the tank is diluted to the target concentration value. . If the measured concentration value is less than the target concentration value, the analyzer 22 instructs the dosing device 21 to supplement a specific type of acidic or alkaline liquid according to a difference P between the measured concentration value and the target concentration value. The concentration of the etching solution in the etching bath 10 is increased to increase the concentration of the etching solution in the bath to the target concentration value.

Please refer to the second figure, which is a flow chart of an embodiment of the etching liquid concentration control method proposed in the present application. The steps include: (S1) setting a target concentration value of the etching liquid; (S2) measuring the etching liquid to obtain a measured concentration value; (S3) calculating the concentration difference according to the target concentration value and the measured concentration value; P; (S4) calculating the time integral value I of the difference P and the time differential value D; (S5) determining the integral coefficient Ki and the differential coefficient Kd according to the time differential value D; (S6) according to the proportional coefficient Kp, the integral coefficient Ki and The differential coefficient Kd is respectively proportional to the difference value P, the time integral value I and the time differential value D; (S7) calculating the tonic amount U according to the result of S6 to replenish the drug solution.

It should be noted that the embodiment shown in the second figure is not limited to the first The apparatus of the drawings is carried out, and the present embodiment only lists the preferred embodiments, and therefore, it is within the scope of the invention as long as it conforms to the method described in the patent application scope of the present application. In addition, the above step S1 is not limited to the step that must be performed first, and may actually be performed simultaneously with the step S2, and the measurement dosing steps may be repeated each time the dosing is completed.

The proportional, integral, and differential control methods used in this case are simply the above-described determination of the amount of replenishment U based on the difference in concentration P, but the details are as follows. First, the difference P between the target concentration value of the etching solution and the measured concentration value is calculated, and then the time differential D and the time integral I of the difference P are obtained, and are respectively multiplied according to the difference P, the time integral I, and the time differential D. The amount of acid supplementation is calculated by the previous proportional coefficient Kp, the integral coefficient Ki, and the differential coefficient Kd. The simple formula is as follows: <Formula 1> U = Kp × P + Ki × I × Kd × D Equation 1 is a simplified formula, which is actually derived from the following formula 2.

<Formula 2>U(t)=Kp×[P(t)+1/Ti×∫p(t)dt+Td×dP(t)/dt]

In Equation 2, Ti is the integration time, Td is the differential time, and Ki = Kp / Ti, Kd = Kp × Td. Usually only for proportional control, if the input value at time t is U(t) and the output value is P(t), and U ₀ is the input value necessary to maintain P(t)=P ₀ (P ₀ is the target Concentration value), therefore, under the premise that the relationship of ΔU(t)=U(t)-U ₀ and ΔP(t)=P(t)-P ₀ is established, the proportional control should satisfy ΔU(t)= Kp×ΔP Formula of (t).

The concept of proportional control of the above formula is to eliminate the current concentration difference P, that is, the larger the concentration difference P, the larger the amount of replenishment U required, and the two must be in a proportional relationship. The concept of integral control is the average past concentration difference, which is used to eliminate the fixed deviation between the target concentration value and the measured concentration value. The differential control is to predict the future concentration difference through the change trend of the concentration difference, which is used to correct the acid supplement amount. The phenomenon of target value oscillating up and down, combined with the three directions to give more detailed and complete concentration control than the conventional technology, and usually the conventional technology can only achieve proportional control.

In the etchant concentration control method of the present case, when the ratio control is performed, since the replenishment of the chemical solution and the measurement of the concentration of the etchant require time, the change of the concentration during this period requires integral control to increase the amount of replenishment, and the control of the tonic is controlled. The degree of blockage of the tubing may cause delays in the replenishment of the drug solution. Therefore, in order to prevent the subsequent measurement of the concentration value, the actual situation is miscalculated, and finally, the excess liquid is replenished. Therefore, it is necessary to add differential control, and the differential coefficient Kd should be negative.

However, there are still some shortcomings in controlling the concentration of the etching solution by proportional, integral and differential. The physical properties of the etching solution are thick, and the replenishing pipeline leading to the etching tank is easy to follow the etching time. A considerable degree of hysteresis blockage is generated, so the above formula should increase the adjustment of the dosing amount U depending on the etching condition.

Since the condition of the tonic delay can be obtained by measuring the variation of the concentration of the etching solution, the present case can vary with the magnitude of the D value. For example, when the D value falls within the first range, the proportional coefficient Kp used for the three control modes is adjusted. , the integral coefficient Ki, the value of the differential coefficient Kd, or optionally one of the above coefficient values to adjust, such that the proportional value Kp × P, the proportional integral value Ki × I, the proportional differential value Kd × D generated Corresponding changes, in turn, calculate the amount of supplement U (output) that varies according to the value of D.

In the control method of the present case, the time integral I and the time differential D need to accumulate several measurement results in order to obtain sufficiently usable data, so although Kp, Ki, and Kd are usually fixed numbers set by appropriate selection, In the first two to three concentration measurement steps after the start of the etching process (in the initial stage of etching, the D value of the period is defined as falling within an interval [a ₀ , b ₀ ]), and when the value of D falls within the interval [a ₀ When b ₀ ], let Ki and kd be set to zero, and the proportional integral value and the proportional differential value are invalidated. That is to say, in the initial stage, the concentration of the etching solution can be maintained only by proportional control, and the values of Ki and Kd can be changed after the D value is calculated and falls within the appropriately selected predetermined interval [a ₀ , b ₀ ], of course, only It is also within the scope of the present invention that Ki or Kd is set to zero when the D value falls within the interval [a ₀ , b ₀ ] or the interval [a' ₀ , b' ₀ ], respectively.

If the concentration difference P is large (usually the initial stage of etching), the time differential D value indicating the change trend of the concentration will usually increase (due to the large amount of the drug to make the concentration change), then the D value can be set to fall. When an interval [a, b] or does not fall within an interval [a ₁ , b ₁ ], Kd is a negative value, which causes the proportional differential value Kd × D to become a large negative value, which can suppress the problem of overdose. Once the concentration enters a steady state, that is, the amount of change in concentration is small (D becomes small), the influence of the proportional differential value Kd×D is relatively small.

Of course, in addition to the differential coefficient Kd, the integral coefficient Ki can also be set according to the D value. Due to the etching process in the present method, after the concentration of the etching solution gradually reaches a stable value, the target concentration value and the measured concentration value produce a fixed deviation. Therefore, the setting of the change condition can also be made for the Ki value. For example, for a specific situation, when the integral control does not need to be operated at the initial stage of etching, or when the concentration of the etching solution is gradually stabilized, or the etching process continues for a long time, causing the pipe blockage degree to become serious, respectively, setting one for the D value. The first interval [a ₂ , b ₂ ] and the second interval [a ₃ , b ₃ ], such that when the D value falls within the first interval, Ki is a first constant value, and when the second interval falls, Ki For a second fixed value, Ki is zero when it does not fall within the first interval and the second interval, and the three kinds of conditions described above are determined by three variable Ki values.

Please refer to the third figure, which is a line diagram of the acid control state of an embodiment of the etching liquid concentration control method proposed in the present invention. According to the etching liquid concentration control method proposed in the present case, Kp=0.5, Ki=0, Kd=0 of the first two acid-controlling acids are set, Kd=-0.25 is set from the third acid control, and Ki is less than 0.01 when D is less than 0.01. = 0.25; when the value exceeds 0.01, Ki=0. The target concentration was set to 1.79%, and the initial concentration of the etching solution was 1.60%. In the third figure, the Y coordinate on the left side is the concentration after acid control, and the Y coordinate on the right side is the acid supplement amount. If the acid supplement amount is 0.1, it means that the added acid amount can increase the concentration of the chemical solution by 0.1%. The acid control result is shown in the third figure. From the third figure, the concentration of the etching solution will gradually stabilize under the premise that the etching liquid consumption rate is constant.

According to the technical content disclosed above, when the concentration of the etching liquid is controlled according to the method disclosed by the present invention, it is necessary to continuously measure the concentration of the etching liquid in the process, and then according to the difference between the measured concentration value and the ideal concentration value desired by the user. The calculation method of integration, differentiation, and proportionalization is performed to obtain a supplement amount of the acid-base liquid solution to perform the medicine to maintain the concentration of the etching liquid. Since the present invention monitors the concentration change at any time, and can adjust the relevant parameters of the calculation formula according to the concentration change condition, the feedback control information can be provided immediately, so that the liquid medicine can be accurately and continuously replenished, and the concentration of the etching liquid is stabilized. The invention has the advantages of improving production efficiency and product quality.

The present invention is a rare and inconspicuous invention, and the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention. That is, the equal changes and modifications made by the applicant in accordance with the scope of the patent application of the present invention should still fall within the scope covered by the patent of the present invention. I would like to ask your review committee to give a clear explanation and pray for it.

1‧‧‧ etching machine side

2‧‧‧Concentration analysis and control side

10‧‧‧etching tank

11‧‧‧Circulating pump

12‧‧‧Circulation pipeline

20‧‧‧ drug liquid barrel

21‧‧‧Dosing machine

22‧‧‧Analyzer

23‧‧‧Analysis pipeline

24‧‧‧Control line

P‧‧‧ difference

I‧‧‧ time integral value

D‧‧‧ time differential value

Kp‧‧‧ scale factor

Ki‧‧· integral coefficient

Kd‧‧‧ differential coefficient

U‧‧‧Replenishment

First: a schematic diagram of an etchant concentration analysis and control device matched with the etchant concentration control method of the present invention; a second diagram: a flow chart of an embodiment of the etchant concentration control method of the present invention; and a third diagram: etching of the present invention A line diagram of the acid control state of an embodiment of the liquid concentration control method.

P‧‧‧ difference

I‧‧‧ time integral value

D‧‧‧ time differential value

Kp‧‧‧ scale factor

Ki‧‧· integral coefficient

Kd‧‧‧ differential coefficient

U‧‧‧Replenishment

Claims (24)

An etchant concentration control method, the method comprising: setting a target concentration value of an etchant; measuring the etchant to obtain a measured concentration value; and calculating a difference according to the target concentration value and the measured concentration value Diluting the difference to obtain a proportional value; scaling a time integral value of the difference to obtain a proportional integral value; scaling a time differential value of the difference to obtain a proportional differential value; and according to the ratio The value, the proportional integral value, and the proportional differential value complement the etchant concentration to the target concentration value. The method of claim 1, wherein the method further comprises: measuring the concentration of the etching solution by using one of ion chromatography, one titration, and one spectral analysis. The method of claim 2, wherein the titration method extracts an etchant sample from the etchant by a micropump. The method of claim 3, wherein the step further comprises: selecting a diluent from the group consisting of propylene glycol, glycerin, and isopropyl alcohol to dilute the etchant sample. The method of claim 1, wherein the step further comprises: when the time differential value falls within a first range, the proportional integral value is zero. The method of claim 1, wherein the step further comprises: when the time differential value falls within a second range, the proportional differential value is zero. The method of claim 1, wherein the step further comprises: when the time differential value falls within a third range, the proportional differential value is a negative value. The method of claim 1, wherein the etching solution is selected from the group consisting of hydrogen peroxide Sodium, potassium hydroxide, and ammonia are grouped together. The method of claim 1, wherein the etching solution is selected from the group consisting of hydrochloric acid, hydrofluoric acid, nitric acid, acetic acid, phosphoric acid, and sulfuric acid. The method of claim 1, wherein the step further comprises: increasing the concentration of the etching solution to the target concentration value according to the difference when the target concentration value is greater than the measured concentration value. The method of claim 1, wherein the step further comprises: decreasing the concentration of the etching solution to the target concentration value according to the difference when the target concentration value is less than the measured concentration value. An etchant concentration control method, the method comprising: monitoring a concentration change value of an etchant; scaling the concentration change value to obtain a proportional value; and proportionalizing the time change value of the concentration change value to obtain a proportional integral value And proportionalizing a time differential value of the concentration change value to obtain a proportional differential value; and supplementing the etching liquid according to the proportional value, the proportional integral value, and the proportional differential value. The method of claim 12, the method further comprising: setting a first concentration value of the etching liquid, measuring the etching liquid to obtain a second concentration value, and according to the first concentration value and the second The concentration value is obtained to obtain the concentration change value. The method of claim 13, wherein the step further comprises: measuring the concentration of the etching solution by one of ion chromatography, one titration, and one spectrometry. The method of claim 14, wherein the titration method extracts an etchant sample from the etchant by a micropump. The method of claim 15, wherein the step further comprises: selecting a diluent from the group consisting of propylene glycol, glycerin, and isopropyl alcohol to dilute the etchant sample. The method of claim 12, wherein the step further comprises: when the time differential value falls within a first range, the proportional integral value is zero. The method of claim 12, wherein the step further comprises: when the time differential value falls within a second range, the proportional differential value is zero. The method of claim 12, wherein the step further comprises: when the time differential value falls within a third range, the proportional differential value is a negative value. The method of claim 12, wherein the etching solution is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonia. The method of claim 12, wherein the etching solution is selected from the group consisting of hydrochloric acid, hydrofluoric acid, nitric acid, acetic acid, phosphoric acid, and sulfuric acid. The method of claim 12, wherein the proportional value is a product of the concentration change value and a first fixed number, and the proportional integral value is a product of the time integral value and a second fixed number, the ratio The differential value is the product of the time differential value and a third fixed number. An apparatus for controlling concentration of an etching solution, comprising: an etching liquid tank for storing an etching liquid; and an analyzer for monitoring a concentration change value of the etching liquid in the etching liquid tank and proportionalizing the concentration change value Obtaining a proportional value, proportionalizing a time integral value of the concentration change value to obtain a proportional integral value, and proportionalizing a time differential value of the concentration change value to obtain a proportional differential value; a liquid medicine barrel for storing one a liquid medicine for supplementing the etching liquid in the etching liquid tank; a dosing machine, the proportional value and the proportional integral value analyzed according to the analyzer And the proportional differential value, an appropriate amount of the chemical solution is taken out from the liquid medicine tank to be added to the etching liquid tank; and a circulation line is provided to provide a passage for the etching liquid to be introduced into the analyzer through a pump, or The liquid is replenished into the etching solution tank. The apparatus of claim 23, wherein the liquid is hydrochloric acid, hydrofluoric acid, mono nitric acid, monoacetic acid, monophosphoric acid, monosulfuric acid, monosodium hydroxide, potassium hydroxide, monoamine, and One of its combinations.