JP6112450B2 - Etching solution component concentration measuring device and etching solution management device - Google Patents

Description

  The present invention relates to a component concentration measuring device and an etching solution management device for an etching solution (hereinafter also referred to as “etchant”) used in photolithography.

  In ICs, LSIs, etc., miniaturization and multilayering of wiring circuits are progressing along with higher integration of semiconductor elements and reduction in chip size. Further, not only such minute parts but also an FPD such as a liquid crystal display requires a minute wiring circuit to form a pixel. In order to create such a minute wiring circuit, a photolithography technique is essential.

  In photolithography, a material film for forming a wiring circuit is formed, and a photoresist is applied on the film. Then, after the photoresist is exposed to a pattern corresponding to the wiring and removed, the material film is etched. The etching solution is usually composed of a plurality of components, and causes a chemical reaction with an element in the material film, thereby dissolving the material film in a portion other than that protected by the photoresist.

  In the production site, the etching solution is repeatedly used. Therefore, as the number of treatments increases, the etched material film components increase in the etching solution, and the components of the etching solution itself are consumed. If the etching solution is composed of a plurality of components, the component ratio may change as the number of processed sheets increases. A decrease in the composition of the etching solution or a deviation in the composition ratio affects the etching rate, and in many cases leads to a decrease in productivity. Therefore, it is necessary to constantly monitor the component concentration in the etching solution.

Therefore, the component concentration of the etching solution is monitored, and when a specific component is insufficient, the performance of the etching solution is kept constant by replenishing it. In Patent Document 1, regarding the chromium etching solution composed of cerium ammonium nitrate, nitric acid and water, the concentration of cerium ions (Ce ⁴⁺ ) in the liquid is monitored by measuring the oxidation-reduction potential so that it falls within a predetermined range. A technique for supplying cerium ions is disclosed.

  Patent Document 2 discloses a method of measuring an indium concentration in a solution using an absorptiometer when managing an ITO film etching solution.

  Patent Document 3 discloses a method for calculating a component concentration from titration and conductivity of an etching solution.

JP-A-11-001781 Japanese Patent No. 2747647 JP 2004-137519 A

  The above cited references are common in that the etching rate is maintained by monitoring the components in the etching solution in which the component ratio changes, but the methods for monitoring the components in the etching solution are not common. This is because the points to be considered differ depending on the object to be etched and the composition of the etching solution.

At present, an oxide semiconductor made of InGaZnO ₄ (hereinafter also referred to as “IGZO”) is attracting attention as a semiconductor capable of high-speed switching because of its high electronic conductivity. Although some products have already been realized, the etching solution for mass production still needs to be studied. Even when an oxide semiconductor containing InGaZnO ₄ is etched with an etching solution of a mixed acid of phosphoric acid and nitric acid, sufficient study has not been made.

  Etching solutions in which phosphoric acid and nitric acid are mixed have been used in the past, but how the components of the etching solution change and how it is monitored when etching is repeated There is no unified knowledge. In particular, when the etching target is IGZO, it can be said that it is in the examination stage.

  The present invention has been conceived in view of the above-described problems. When IGZO is a mixed acid solution of phosphoric acid and nitric acid as an etching solution, an etching solution component concentration measuring device for measuring the concentration of phosphoric acid and nitric acid in the etching solution; The present invention provides an etching solution management device that avoids a decrease in etching rate when the amount of processing for the same etching solution increases.

More specifically, the component concentration measuring apparatus of the present invention is:
A component concentration measuring apparatus for measuring a component concentration of an etching solution containing phosphoric acid and nitric acid stored in an etching solution tank and etching a thin film containing metal,
A sampling pipe through which the etching solution in the etching solution tank flows;
An IR absorbance measuring device provided in the middle of the sampling pipe;
A control unit connected to the IR absorbance measurement device;
The control unit calculates a phosphoric acid concentration in the etching solution based on an IR phosphoric acid calibration curve stored in advance ,
A metal component calibration curve indicating the relationship between the absorbance of nitric acid measured in advance with the IR absorbance measurement device and the concentration of the metal component in the etching solution is stored, the measurement result of the absorbance of nitric acid with the IR absorbance measurement device, The metal concentration in the etching solution is calculated from a metal component calibration curve .

Moreover, the etching solution management device according to the present invention includes:
An etching solution management device for managing component concentrations of an etching solution containing phosphoric acid and nitric acid stored in an etching solution tank having a liquid discharging means for etching a thin film containing metal,
A sampling pipe through which the etching solution in the etching solution tank flows;
An IR absorbance measuring device provided in the middle of the sampling pipe;
A controller connected to the IR absorbance measuring device;
A solution adding means for adding a solution to the etching solution tank;
The controller is
Calculate the phosphoric acid concentration in the etching solution based on the IR phosphoric acid calibration curve stored in advance,
Controlling the solution adding means based on the phosphoric acid concentration ;
A metal component calibration curve indicating the relationship between the absorbance of nitric acid measured in advance with the IR absorbance measurement device and the concentration of the metal component in the etching solution is stored, the measurement result of the absorbance of nitric acid with the IR absorbance measurement device, The metal component concentration in the etching solution is calculated from a metal component calibration curve .

  In the component concentration measuring apparatus according to the present invention, the concentration of phosphoric acid can be determined using IR absorbance. The concentration of nitric acid can be determined using the absorbance of UV light having a wavelength near 300 nm. Therefore, the phosphoric acid and nitric acid concentrations of the etching solution can be determined in a short time.

  In the etching solution management apparatus according to the present invention, the concentration of phosphoric acid is determined using IR absorbance, and when phosphoric acid exceeds a predetermined concentration range, the etching solution, phosphoric acid, or water is supplemented. The etching rate can always be maintained within a predetermined range.

  Further, in the etching solution management apparatus according to the present invention, the metal ion concentration can be calculated from the IR measurement result of nitric acid, so it is possible to know how many times it has been used. Therefore, when the metal ion concentration becomes a predetermined concentration or more, the etching solution can be replaced with a new solution or most of the solution can be replaced. That is, it is possible to know the timing of replacement of the etching solution with a new solution.

It is a figure which shows the structure of a component density | concentration measuring apparatus. It is a graph which shows the relationship between the etching processing amount of IGZO, and an etching rate. It is a graph which shows the relationship between Zn density | concentration at the time of dissolving Zn powder in etching solution, and the etching rate of an IGZO film. It is a graph which shows the neutralization titration curve when the neutralization titration curve of nitric acid and ZnO powder are put into nitric acid. It is an assumption reaction model in each section of Drawing 4. It is a graph which shows the neutralization titration curve when the neutralization titration curve of phosphoric acid and ZnO powder are put into phosphoric acid. It is a graph explaining how to determine the inflection point of the neutralization titration curve. It is an assumed reaction model in each section of FIG. It is a graph which shows the neutralization titration curve at the time of putting ZnO powder in the etching solution which mixed phosphoric acid and nitric acid. 10 is an assumed reaction model in each section of FIG. 9. It is a graph which shows the light absorbency of water, phosphoric acid, nitric acid, and mixed acid. It is a graph which shows the light absorbency near wavelength 300nm. It is the graph which investigated the influence of the other component of wavelength 300nm vicinity. It is the graph which investigated the influence at the time of dissolving ZnO powder in mixed acid. It is the graph which investigated the etching rate at the time of dissolving Zn powder in mixed acid, and the density | concentration of phosphoric acid and nitric acid. It is the graph which investigated the etching rate when the IGZO film | membrane was dissolved in mixed acid, and the density | concentration of phosphoric acid and nitric acid. It is the graph which investigated the recovery | restoration of the etching rate by adding phosphoric acid to the etching solution in which the etching rate fell. It is a graph which shows the relationship between the IR measurement result of the nitric acid in an etching solution, and the metal ion concentration in an etching solution. It is a figure which shows the structure of an etching solution management apparatus. It is a figure which shows the change of each component density | concentration in the etching solution by operation | movement of an etching solution management apparatus. It is a figure which shows the structure of other embodiment of an etching solution management apparatus. It is a figure which shows the change of each component density | concentration in the etching solution by operation | movement of the etching solution management apparatus of FIG. It is a figure which shows the structure of other embodiment of an etching solution management apparatus. It is a figure which shows the change of each component density | concentration in the etching solution by operation | movement of the etching solution management apparatus of FIG.

  The present invention will be described below with reference to the drawings and examples, but the embodiments can be modified without departing from the spirit of the present invention.

(Embodiment 1)
FIG. 1 shows a configuration of a component concentration measuring apparatus 1 according to the present invention. The component concentration measuring device 1 includes a sample pipe 10, a heat exchanger 12, a UV absorbance measuring device 14, an IR absorbance measuring device 16, a control unit 20, and a display device 24.

  The sample pipe 10 is a flow path through which an etching solution that is a liquid to be measured passes. The etching solution flows in from the inlet 10in and flows out from the outlet 10out. The sample pipe 10 is preferably made of a material having acid resistance and alkali resistance. PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is one of materials that can be suitably used. Moreover, the sample piping 10 may be comprised with the some raw material. For example, a quartz tube may be used in a portion to which the UV absorbance measurement device 14 and the IR absorbance measurement device 16 are connected.

  Further, a branch pipe (not shown) branching from the sample pipe 10 may be provided in these measurement apparatus portions. Of the sample pipes 10, the side closer to the inlet 10in is called the upstream side, and the side closer to the outlet 10out is called the downstream side.

  A heat exchanger 12 is provided on the most upstream side between the sample pipes 10. The heat exchanger 12 allows water having a constant water temperature to pass around the sample pipe 10, and maintains the temperature of the etching solution in the sample pipe 10 at a predetermined temperature. The heat exchanger 12 is provided with a water inlet 12in and a water outlet 12out.

  A UV absorbance measurement device 14 and an IR absorbance measurement device 16 are arranged on the downstream side of the heat exchanger 12. These arrangement orders are not particularly limited. Either may be arranged on the upstream side.

  The UV absorbance measuring device 14 measures the absorbance in the ultraviolet region of at least 280 to 320 nm. Therefore, a light source that emits light in this wavelength band is incorporated. The liquid to be measured (etching solution) may be measured by attaching a quartz tube to the sample pipe 10 and using the quartz tube. Alternatively, the liquid to be measured may be obtained in a quartz tube branched from the sample pipe 10 and measured.

  The UV absorbance measurement device 14 measures the absorbance at a designated wavelength according to an instruction Cuv from the control unit 20 described later. The measured value can be returned to the control unit 20 as a signal Suv.

  The IR absorbance measurement device 16 measures near infrared absorbance of at least 900 to 1300 nm. In other words, at least a light source that emits light in this wavelength range is incorporated. The liquid to be measured (etching solution) is handled in the same manner as in the UV absorbance measuring device 14. Further, the IR absorbance measurement device 16 may incorporate characteristic peak information for phosphoric acid and nitric acid. Therefore, an absorbance based on the characteristic peak of phosphoric acid or an absorbance based on the characteristic peak of nitric acid can be obtained by an instruction Cir from the control unit 20 described later. These values can be returned to the control unit 20 by the signal Sir.

  The thermometer 18 is provided on the most downstream side of the sample pipe 10. This is for confirming the temperature of the etching solution in the sample pipe 10. The measured value of the thermometer 18 is sent to the control unit 20 as a signal St.

  The control unit 20 can be configured by a computer including an MPU (Micro Processor Unit) and a memory 20M. The controller 20 is connected to at least the IR absorbance measuring device 16 and the thermometer 18. Further, the UV absorbance measuring device 14 and the display device 24 may be connected.

  The memory 20M stores a program for controlling the operation of the component concentration measuring apparatus 1, and the component concentration measuring apparatus 1 can be operated by this program. In the memory 20M, an IR phosphate calibration curve, a UV nitric acid calibration curve, and an IR nitric acid calibration curve (or a metal component calibration curve described later based on this) are held. The IR phosphoric acid calibration curve is a graph showing the relationship between the phosphoric acid absorbance obtained by the IR absorbance measuring device 16 obtained in advance and the phosphoric acid concentration in the solution, and may be stored as a table.

  The UV nitric acid calibration curve is a graph showing the relationship between the nitric acid absorbance determined by the UV absorbance measuring device 14 and the nitric acid concentration in the solution. The IR nitric acid calibration curve is a graph showing the relationship between the nitric acid absorbance determined by the IR absorbance measuring device 16 and the nitric acid concentration in the solution. Both may be stored in the memory 20M as a table similar to the IR phosphate calibration curve.

  The display device 24 displays the current operating state of the component concentration measuring device 1, the etching solution temperature, the phosphoric acid concentration, the nitric acid concentration, the metal component concentration, and the like. The control unit 20 transmits these pieces of information to the display device 24 as a signal Sv. The display device 24 displays these pieces of information based on this signal Sv.

  Next, the operation of the component concentration measuring apparatus 1 will be described. The inlet 10in of the sample pipe 10 is connected to, for example, the upstream side of the circulation pipe of the etching solution tank of the etching apparatus. You may arrange | position the filter and the transfer pump of etching solution between circulation piping. Further, the outlet 10out of the sample pipe 10 is connected to, for example, the downstream side of the circulation pipe. You may arrange | position so that the etching solution from the outflow port 10out may return to an etching solution tank directly.

  Further, water at a constant temperature is caused to flow through the water inlet 12 in of the heat exchanger 12. The water having a constant temperature circulates in the heat exchanger 12 and is discharged from the water outlet 12out. This is because the temperature of the etching solution in the sample pipe 10 is adjusted to the solution temperature when the calibration curve is prepared. Since the etching solution is used at a temperature of about 40 ° C. in the etching apparatus, it may be different from the temperature at which the calibration curve was produced.

  The absorbance may depend greatly on the liquid temperature. Therefore, there is a possibility that an accurate component concentration cannot be calculated. Therefore, the heat exchanger 12 is arranged in order to make the temperature of the etching solution in the sample pipe 10 constant. This constant temperature may be about 25 ° C., for example.

  When the heat exchanger 12 is operated and the etching solution starts flowing in the sample pipe 10, the component concentration measuring apparatus 1 is operated.

  The control unit 20 first confirms the temperature of the etching solution with the signal St from the thermometer 18 and waits until the temperature of the etching solution reaches a predetermined temperature. In addition, you may make it display on the display apparatus 24 that it is the present etching solution temperature or it is waiting.

  When the temperature of the etching solution reaches a predetermined temperature, measurement is started. The measurement is started by transmitting a measurement start signal to the IR absorbance measurement device 16 and the UV absorbance measurement device 14 with an instruction Cir and an instruction Cuv, respectively.

  The UV absorbance measurement device 14 and the IR absorbance measurement device 16 measure the determined wavelength and the absorbance of the target substance, respectively, and return them to the control unit 20 as a signal Suv and a signal Sir. Based on these measurement results, the control unit 20 calculates the concentration of each component using various calibration curves. The calculated density is displayed on the display device 24.

  The density measurement interval is not particularly limited, and the density display may be measured a plurality of times and the average value may be displayed.

  In the component concentration measuring apparatus 1, it can utilize suitably in the case of the etching solution which consists of phosphoric acid, nitric acid, and water. Moreover, it can utilize more suitably with respect to the etching solution repeatedly used so that it may be used in a factory etc. This is because the etching solution is continuously etched in a factory or the like, so that the component concentration of the etching solution changes every moment.

The object of etching is a film made of a metal element and may contain a metalloid element. Alternatively, the oxide may contain oxygen. For example, an oxide semiconductor (IGZO) of InGaZnO ₄ that is an oxide of In (indium), Ga (gallium), and Zn (zinc) can be used as a suitable etching target material. In the present specification, In, Ga, and Zn may be included in the metal component in the etching solution.

  In the component concentration measuring apparatus 1, the phosphoric acid concentration in the etching solution is measured by infrared spectroscopy (IR), and the nitric acid concentration is measured by ultraviolet spectroscopy (UV). In particular, ultraviolet light has a wavelength selected from wavelengths of 280 to 320 nm, and preferably measures absorption at 300 nm. As will be described later, in this etching solution, the absorption characteristic at a wavelength of 300 nm well reflects the concentration of nitric acid. Moreover, the phosphoric acid concentration measured by infrared spectroscopy is in good agreement with the phosphoric acid concentration obtained from the neutralization titration measurement. Hereinafter, the principle and validity of the measurement used in the component concentration measuring apparatus 1 will be described.

<1: Existence of problems Repeated use of etching solution>
As an etching solution, water, phosphoric acid 3.5 wt%, and nitric acid 0.50 wt% were prepared. Hereinafter, this etching solution is also referred to as “mixed acid”. This composition is a composition of a new solution, and the concentration of phosphoric acid and nitric acid deviates from this value by repeated use. Further, when phosphoric acid or nitric acid is added to recover the etching rate (hereinafter also referred to as “E / R”), the composition may deviate from this composition. Etching solution samples 1 to 3 were prepared by dissolving In, Ga, and Zn shown in Table 1 in this etching solution.

A 10 mm × 50 mm substrate in which an IGZO film (InGaZnO ₄ ) was formed to a thickness of 100 nm was immersed in a silicon substrate, and stirring was performed at 370 rpm with a magnetic styler. The etching solution was at room temperature (25 ° C.).

  The time during which the IGZO film disappeared visually was measured as the just etching time (hereinafter also referred to as “JET”), and the etching rate was calculated. The results are shown in FIG. In FIG. 2, the horizontal axis represents the In concentration (1000 ppm) in the etching solution, and the vertical axis represents the etching rate (nm / min). The etching rate, which was 43 nm / min when the In concentration was 0 ppm (in the case of a new solution), decreased as the In concentration increased, and decreased to 25 nm / min when the In concentration was 1260 ppm.

  Such a decrease in the etching rate may cause a decrease in the production rate or an etching failure. Therefore, in order to keep the etching rate constant, the etching solution must be added or replaced.

<1-1. Applicability of alternative tests>
The above phenomenon is also reproduced when zinc is contained in an etching solution of phosphoric acid and nitric acid. A predetermined amount of zinc (Zn) powder was dissolved in 50 ml of the above etching solution (mixed acid) to prepare Test Samples 4 to 7. Increasing the amount of zinc dissolved reproduces the repeated use of the etching solution. The Zn concentration of each sample (etching solution) was set to 0 ppm, 3020 ppm, 5030 ppm, and 10000 ppm for samples 4 to 7, respectively.

A 10 mm × 50 mm substrate in which an IGZO film (InGaZnO ₄ ) was formed to a thickness of 100 nm was immersed in a silicon substrate, and stirring was performed at 370 rpm with a magnetic styler, and the etching rate was calculated in the same manner as described above. The etching solution was at room temperature. The results are shown in FIG.

  In FIG. 3, the horizontal axis represents the Zn concentration (ppm) of the etching solution, and the vertical axis represents the etching rate (nm / min). The etching rate, which was 43 nm / min when the Zn concentration was 0 ppm, decreased with increasing Zn concentration, and decreased to 10 nm / min when the concentration was 10,000 ppm. This can mimic the etching rate reduction caused by repeated etching of the IGZO film. In the subsequent examination, Zn powder or ZnO powder was used instead of IGZO.

<2: Elucidation of phenomenon Neutralization titration curve>
Etching is a phenomenon in which the target substance dissolves in the etching solution. Therefore, if etching is performed, it is easily expected that the component concentration of the etching solution will change. This is because the change in etching rate with time is considered to be caused by a change in component concentration. Therefore, it is necessary to separately measure the phosphoric acid concentration and nitric acid concentration in the etching solution. The basis of concentration measurement is neutralization titration. Therefore, it was started by confirming neutralization titration with the components alone.

<2-1. For nitric acid + metal>
FIG. 4 shows a neutralization titration curve L10 of nitric acid and a neutralization titration curve L12 when ZnO powder is dissolved in nitric acid. Sodium hydroxide (NaOH) was used for neutralization. When ZnO powder was dissolved, the titration curve had two inflection points. The first inflection point when the ZnO powder is dissolved is A1, and the inflection point of the neutralization titration curve with only nitric acid is A2. Table 3 shows the composition and the position of the inflection point of each sample (8 and 9).

  In FIG. 5, the assumed reaction of the area from 0 to A1 and the area from A1 to A2 is shown. Between 0 and A1, nitric acid ionization occurs, and ZnO is etched by the generated protons (enclosed by squares) to become zinc ions. Between A1 and A2, it is considered that zinc nitrate is generated by the generated zinc ions and nitrate ions.

<2-2. For phosphoric acid + metal>
FIG. 6 shows a neutralization titration curve L14 of phosphoric acid and a neutralization titration curve L16 when ZnO powder is dissolved in phosphoric acid. NaOH was used for neutralization. Since phosphoric acid ionizes with H ₂ PO ₄ ⁻ , HPO ₄ ²⁻ , and PO ₄ ³⁻ , the neutralization titration curve possesses two inflection points in the first place. Let each inflection point be A1 and A2. In the case of phosphoric acid, when the ZnO powder was dissolved, the neutralization titration curve shifted to the left. Furthermore, as the Zn concentration increased, the value of A2-A1 increased. Table 4 shows the composition of each sample and the position of the inflection point.

  FIG. 7 shows the inflection points of the neutralization titration curve. FIG. 7 is a neutralization titration curve L13 of phosphoric acid. The inflection point refers to the titration reagent capacity at the extreme points P1 and P2 of the secondary differential curve L132 of the neutralization titration curve L13. In the present specification, the secondary differential curve of the neutralization titration curve is not clearly shown, but the inflection point is determined by the extreme value of the secondary differential curve.

FIG. 8 shows an assumed reaction occurring in a section divided by A1 and A2 in the titration reagent volume. The section surrounded by “A” is a section from 0 to A1, the section surrounded by “B” is a section from A1 to A2, and the section surrounded by “C” is The section where the titration reagent volume is greater than A2 is shown. Since the protons (enclosed by squares) supplied by phosphoric acid existing in the section from 0 to A1 contribute to the etching, when ZnO powder is added, the amount of H ₃ PO _{4 in} this section decreases, The neutralization titration curve is thought to shift to the left.

<2-3. Mixed acid + metal>
FIG. 9 shows a neutralization titration curve when different ZnO powder amounts are dissolved in a mixed solution of nitric acid and phosphoric acid. Table 5 shows the composition ratio of each sample and the values of the inflection points A1 and A2.

  Here, the Zn concentration indicates the Zn content of the input ZnO powder. When the dissolution amount of the ZnO powder is increased, the neutralization titration curve itself shifts to the left as in the case of phosphoric acid alone. In addition, the amount of A2-A1 increased as the Zn concentration increased, as was the case with phosphoric acid alone. Thus, it is thought that the amount of A2-A1 increases as the Zn concentration increases due to the influence of metal ions.

In FIG. 10, the assumed reaction which has arisen in each area is shown. Protons (enclosed by squares) supplied by HNO ₃ and H ₃ PO ₄ between 0 and A1 are considered to contribute to dissolution (etching) of ZnO. Here, the fact that A2-A1 increases as the Zn concentration increases indicates that the consumption of protons supplied from nitric acid and protons supplied from phosphoric acid are not the same. That is, the consumption of protons supplied from nitric acid and the consumption of protons supplied from phosphoric acid are not the same.

<3: Utilization of absorbance>
No further analysis is possible using only neutralization titration. A method for independently detecting at least one of the nitric acid concentration and the phosphoric acid concentration in the section from 0 to A1 is required. Then, the light absorbency of the mixed acid state containing phosphoric acid and nitric acid was investigated.

<3-1. Absorbance results>
FIG. 11 shows the absorbance in the case of water alone (FIG. 11 (a)), phosphoric acid alone (FIG. 11 (b)), nitric acid alone (FIG. 11 (c)), and mixed acid (FIG. 11 (d)). . In each graph, the vertical axis represents absorbance and the horizontal axis represents light wavelength. The wavelength of the measured light is in the range of 200 nm to 2000 nm. Referring to FIGS. 11A and 11B, in this wavelength range, water and phosphoric acid have the same absorbance and cannot be distinguished.

  On the other hand, referring to FIG. 11C, it can be seen that nitric acid has a characteristic absorption peak at a wavelength of 300 nm. This 300 nm absorption peak is maintained even when mixed acid is used (see FIG. 11 (d)). Further, since it is an absorption peak not found in water and phosphoric acid, it may be used for detection of nitric acid.

<3-2. Absorption peak at 300 nm>
FIG. 12A shows an absorption spectrum obtained by enlarging only the vicinity of a wavelength of 300 nm. The vertical axis is absorbance, and the horizontal axis is wavelength. Each represents an absorption peak when the concentration of nitric acid is changed. The absorbance is shown when the nitric acid concentration is changed to 0.22 wt% (two-dot chain line), 0.42 wt% (one-dot chain line), 0.78 wt% (dotted line), and 1.09 wt% (solid line). As the nitric acid concentration increased, the absorbance at 300 nm increased. In FIG. 12 (b), in order to more clearly show the relationship of FIG. 12 (a), the relationship between the absorbance and the blended value of nitric acid (wt%) is plotted. The vertical axis is the blended value (wt%), and the horizontal axis is the absorbance. The absorbance of deionized water was set to zero. From FIG. 12 (b), the absorbance at 300 nm and the blended value of nitric acid showed very good linearity. This can be used as a calibration curve for nitric acid. This calibration curve is a “UV nitric acid calibration curve” and is stored in the memory 20M.

<3-3. Influence of other ingredients>
FIG. 13 shows the results of examining the influence of other components present in the etching solution on the wavelength of 300 nm. Even if the absorbance at 300 nm can be used for detecting the concentration of nitric acid, if other components similarly affect the absorbance at 300 nm, it cannot be used as a calibration curve. In particular, it is known that a NOx absorption peak appears in the vicinity of 300 nm.

  The graph of FIG. 13 shows the case of a mixed acid alone (solid line), the case of a mixed acid with a Zn concentration of 1000 ppm (dotted line), the case of a mixed acid with a Zn concentration of 2000 ppm (one-dot chain line), and the case of a mixed acid with a Zn concentration of 3000 ppm ( Absorbance is shown for the two-dot chain line). The vertical axis represents absorbance and the horizontal axis represents wavelength. In the case of water alone, 0.49% nitric acid simple substance, nitric acid Zn powder added, 3.4 wt% phosphoric acid simple substance added, Zn powder added to phosphoric acid, ZnO mixed acid Measurement was also performed when powder was added, but no absorption peak could be observed in the wavelength band and measurement sensitivity of FIG.

  It can be seen that the absorbance from 350 nm to 370 nm increases as the Zn concentration increases. On the other hand, the absorbance at 300 nm decreased as the Zn concentration increased. This is presumed that with the increase in Zn concentration, protons supplied from nitric acid were consumed for dissolution of ZnO, so the amount of nitric acid decreased and NOx increased instead.

  When nitric acid was not contained, the absorbance at 300 nm was not measured, and even if nitric acid, phosphoric acid, and water coexisted, there was no effect on the wavelength of 300 nm of phosphoric acid and water. FIG. 14 shows the results of absorbance when phosphoric acid was added to the sample having a Zn concentration of 3000 ppm in FIG. 13 (one-dot chain line) and when nitric acid was added (two-dot chain line).

  The case where the Zn concentration is 1000 ppm (solid line) and the case where the Zn concentration is 2000 ppm (dotted line) are also shown. In the graph of FIG. 14, the vertical axis represents absorbance, and the horizontal axis represents wavelength. Even when phosphoric acid was added, the absorbance at a wavelength of 300 nm did not change at all (solid line, dotted line, dash-dot line). On the other hand, when nitric acid was added, the absorbance value at 300 nm increased according to the amount of nitric acid added (two-dot chain line). That is, the UV nitric acid calibration curve can be effectively used to calculate the nitric acid concentration in the solution.

  From the above, the concentration of nitric acid alone in the mixed acid can be measured by the absorbance at 300 nm. The phosphoric acid concentration can be calculated by subtracting this nitric acid concentration from the concentration obtained from the interval from 0 to A1 of the neutralization titration curve.

<4: Verification>
As described above, the relationship between the etching rate and the components of each etching solution was examined using neutralization titration and absorbance at 300 nm. FIG. 15 (a) is a reprint of FIG. 15B and 15C show the results of examining the concentrations of phosphoric acid (FIG. 15B) and nitric acid (FIG. 15C) in the etching solution, respectively. It can be seen that as the Zn concentration increases, both the phosphoric acid concentration and the nitric acid concentration decrease. However, comparing the case where the Zn concentration was 10,000 ppm and 0 ppm, phosphoric acid was reduced by about 90%, whereas nitric acid was only reduced by about 70%.

  This well explains the results when metal (ZnO) is dissolved in the mixed acid of FIG. That is, the amount of protons supplied for etching in the interval from 0 to A1 is greater for protons provided from phosphoric acid than for protons supplied from nitric acid.

<5: In case of verification IGZO>
FIG. 16 shows the results when the IGZO film is dissolved in the mixed acid. FIG. 16A is a reprint of FIG. 2 and shows the relationship between the In concentration and the etching rate. The vertical axis represents the etching rate, and the horizontal axis represents the In concentration. FIG. 16B shows the relationship between the In concentration and the phosphoric acid concentration. The vertical axis represents the phosphoric acid concentration (wt%), and the horizontal axis represents the In concentration. FIG. 16C shows the relationship between In concentration and nitric acid concentration. The vertical axis represents the nitric acid concentration, and the horizontal axis represents the In concentration.

  Referring to FIG. 16A, when the IGZO film is etched with a mixed acid solution, the etching rate decreases as the number increases. At this time, the phosphoric acid concentration decreased in the etching solution (FIG. 16B), but the nitric acid concentration was almost constant (FIG. 16C). This is considered as follows.

In an aqueous solution, HNO ₃ is almost completely dissociated and is considered to exist as H ⁺ and NO ₃ ⁻ . This H ⁺ etches the metal oxide, and the metal ions dissolve in the aqueous solution. However, since H ₃ PO ₄ is present, the metal becomes a phosphate, and H ⁺ and NO ₃ ⁻ are restored. That is, the concentration of nitric acid does not change apparently because phosphoric acid supplements the spent protons of nitric acid.

  In addition, it is considered that the nitric acid concentration decreases when Zn powder is put in the etching solution as follows. When Zn powder is added, the above reaction occurs after Zn is once oxidized to ZnO by nitric acid. That is, in the case of Zn powder, nitric acid is consumed to make the ZnO powder once, so that the nitric acid concentration also decreases.

<6: Result of measurement method>
As described above, the concentration of phosphoric acid and nitric acid in the etching solution can be measured by combining neutralization titration and absorbance at 300 nm. By the way, neutralization titration takes time, although there is an automatic measuring apparatus at present. Then, the method which can measure phosphoric acid more easily was examined. IR measures the absorbance in the range from the near infrared to the far infrared, and by referring to a plurality of characteristic peaks, it is possible to analyze the concentration of the components in the mixed solution.

  Therefore, the concentration of phosphoric acid in the mixed acid was measured by IR. A comparison with neutralization titration is shown in Table 6. Sample 20 is a mixed acid only sample. Sample 21 is a sample in which an IGZO film having a thickness of 10 mm × 25 mm and a thickness of 100 nm is dissolved in 50 ml of mixed acid. Samples 22 and 23 are cases where the number of IGZO films is two or three, respectively. That is, the amount of IGZO dissolved in 50 ml of mixed acid increases from sample 20 to sample 23.

  Referring to Table 6, the column described as “neutralization titration + UV” is the result of measuring the concentration of nitric acid and phosphoric acid with the neutralization titration curve and the absorbance from 300 nm. The column described as “IR measurement result” is the measurement result of nitric acid and phosphoric acid using the absorbance of infrared wavelength light having a wavelength of 900 to 1300. It is the value calculated | required based on the calibration curve only with nitric acid and phosphoric acid, respectively. In the IR measurement, a calibration curve was created using characteristic absorption peaks in the infrared wavelength region of nitric acid and phosphoric acid. They are an IR phosphate calibration curve and an IR nitric acid calibration curve respectively stored in the memory 20M. However, it is considered that these peaks are affected when a mixed acid state or metal ions are present.

  The column described as “UV measurement result” is a result of measuring nitric acid with absorbance at a wavelength of 290 nm. The nitric acid concentration and absorbance determined from the calibration curve (UV nitric acid calibration curve) were described.

The column labeled “Error” shows the difference between the nitric acid concentration in the “Neutralization Titration + UV” column and the nitric acid concentration in the “UV Measurement Result” column as an error in the nitric acid concentration. Acid concentration and “I
The difference from the phosphoric acid concentration in the “R measurement result” column is shown as an error in the phosphoric acid concentration.

  From the IR measurement results, the nitric acid concentration increased as the number of treated IGZO sheets increased. This was considered to be a result of the influence of other components in the etching solution on the characteristic peak of nitric acid in the infrared wavelength region. On the other hand, in the UV measurement result, the change in nitric acid concentration was not measured with respect to the number of treated IGZO. This can also be seen from the error column where the nitric acid error is in the range of -0.03 to -0.04, which is almost constant.

  The wavelength 290 nm is a wavelength adjacent to the wavelength 300 nm, and as shown in FIGS. 12 to 14, the absorbance of nitric acid in this portion is not affected by other substances from 280 nm to 320 nm. Therefore, when the nitric acid concentration is measured by absorbance, absorbance in the range of 280 nm to 320 nm may be used.

  On the other hand, when the measurement result of phosphoric acid in the IR measurement result was seen, it was in very good agreement with the measurement result of phosphoric acid by neutralization titration + UV. It can also be seen from the error column that the phosphoric acid error is in the range of 0.05 to -0.04. That is, with respect to phosphoric acid, the IR measurement results can be used for concentration measurement. It was found that neutralization titration and IR measurement can be substituted for the phosphoric acid concentration in the etching solution when etching IGZO with an etching solution composed of at least phosphoric acid, nitric acid and water.

<7: Maintenance of E / R>
As described above, when IGZO is etched with an etching solution composed of phosphoric acid, nitric acid, and water, the nitric acid concentration in the etching solution can be measured by UV (300 nm) absorbance, and the phosphoric acid concentration can be measured by IR absorbance. it can. Therefore, the means for maintaining the etching rate when IGZO was etched with the same etching solution was studied. As shown in FIG. 2 or FIG. 15A, when IGZO is etched with the same etching solution, the etching rate decreases.

  FIG. 17 shows the result of study on the case where phosphoric acid is added to maintain the etching rate. FIG. 17A shows the relationship between the etching rate and the number of processed IGZO (represented by the amount of In). The vertical axis represents the etching rate, and the horizontal axis represents the In concentration. FIG. 17B shows the relationship between the phosphoric acid concentration and the In concentration. The vertical axis represents the phosphoric acid concentration, and the horizontal axis represents the In concentration. FIG. 17C shows the relationship between nitric acid concentration and In concentration. The vertical axis represents the nitric acid concentration, and the horizontal axis represents the In concentration.

  Since the phosphoric acid concentration decreased according to the number of treated IGZO, it was added so as to maintain the initial concentration (see FIG. 17B). As a result, the decrease in the etching rate could be suppressed considerably (see FIG. 17A). In addition, phosphoric acid was added at a concentration of 1,300 ppm (in a state where 10 samples were dissolved) to a concentration 1.3 times the original (P + point in FIG. 17B). As a result, the decrease in the etching rate was substantially suppressed (PP point in FIG. 17A). From the above, it was found that the etching rate can be maintained by adding phosphoric acid. In addition, as shown in FIG.17 (c), the density | concentration of nitric acid does not change.

  From the above results, the phosphoric acid concentration of the etching solution is measured using IR, and when the phosphoric acid concentration falls below the predetermined concentration, the phosphoric acid is supplemented, so that the predetermined etching rate is always maintained even in mass production. Can be maintained.

  FIG. 18 shows the relationship between the result of IR measurement of mixed acid nitric acid obtained by repeatedly etching IGZO and the total amount of metal ions in the mixed acid. The horizontal axis represents the IR measurement result (wt%) of nitric acid, and the vertical axis represents the result (wt%) of the total amount of metal ion concentration in the mixed acid measured by ICP-MS. Since nitric acid is a value obtained by a calibration curve (IR nitric acid calibration curve) obtained while changing the concentration of a single substance, it is a weight ratio. However, since the calibration curve (IR nitric acid calibration curve) showing the relationship between the absorbance of nitric acid by IR and the concentration of nitric acid is almost a straight line, the horizontal axis of FIG. Can be obtained. A calibration curve indicating the relationship between the absorbance of nitric acid by IR or the concentration of nitric acid obtained from an IR nitrate calibration curve and a metal component (metal ion) is referred to as a “metal component calibration curve”.

  As shown in FIG. 17C, the nitric acid concentration in the mixed acid is constant even after repeated etching, but when measured by IR, it appears that the nitric acid concentration increases with the number of etchings. This is considered to be a result that the absorption peak of metal ions in the mixed acid and the absorption peak of nitric acid are very close. Therefore, the correct nitric acid concentration cannot be obtained even if the nitric acid in the mixed acid is measured by IR.

  However, as shown in FIG. 18, the IR measurement result of nitric acid and the total amount of metal ions in the mixed acid show very good linearity. This indicates that an alternative measurement of the metal ion concentration in the mixed acid can be performed with the IR measurement result of nitric acid. It may be said that the metal ion concentration in the mixed acid is substituted by the IR measurement result of nitric acid. That is, it means that the metal ion concentration in the mixed acid can be confirmed on the mass production site without sequentially measuring with an expensive measuring device called ICP-MS.

  Further, it is considered that the total amount of metal ion concentration in the mixed acid that is the etching solution represents the usage history of the etching solution. As shown in FIG. 17, even with an etching solution whose etching rate is reduced by repeated use, the etching rate can be recovered by supplementing with phosphoric acid. However, the phosphate ion concentration gradually increases. Therefore, if the etching rate is recovered by phosphoric acid supplementation a predetermined number of times, the etching solution needs to be replaced with a new solution.

  In that case, it can be set as the standard which replace | exchanges for a new liquid based on the density | concentration of the metal ion total amount in an etching solution. That is, the nitric acid concentration in the etching solution is measured using IR, and the metal ion concentration in the etching solution is calculated from a calibration curve (metal component calibration curve) as shown in FIG. If the concentration is higher than the predetermined concentration, the etching solution is replaced with a new solution. By doing so, it becomes possible to manage the etching solution precisely even at the site of mass production.

  As described above, the phosphoric acid concentration, the nitric acid concentration, and the total metal ion concentration of the etching solution containing phosphoric acid and nitric acid for IGZO can be calculated using the absorbance. The component concentration measuring apparatus 1 according to the present invention can measure the component concentration of the etching solution based on the principle as described above.

  It has been described that each calibration curve is stored in the memory 20M of the control unit 20, and the control unit 20 calculates each component based on the IR absorbance and the UV absorbance. However, each calibration curve may be stored in the IR absorbance measurement device 16 and the UV absorbance measurement device 14 so that each device calculates the concentration. Even in such a configuration, it may be said that the control unit 20 is connected to the IR absorbance measurement device 16 and calculates the phosphoric acid concentration in the etching solution based on the IR phosphoric acid calibration curve stored in advance. Similarly, the same applies to a UV nitric acid calibration curve, an IR nitric acid calibration curve, and a metal component calibration curve based thereon.

(Embodiment 2)
In FIG. 19, the structure of the etching solution management apparatus 5 which concerns on this invention is shown. The etching solution management device 5 manages an etching solution that is used cyclically in the etching device. As shown in FIG. 16, the component ratio of the etching solution changes according to the processing amount of the workpiece 56, and the etching rate decreases. A decrease in the etching rate leads to an increase in tact time, resulting in an increase in cost.

  Further, when the etching rate is lowered, the etching is not completed within a specified processing time, and there is a possibility that an etching failure occurs. Therefore, it is necessary to check the component concentration of the etching solution as needed and to add an insufficient component or to replace the etching solution itself when the etching rate deviates from a predetermined range.

  With reference to FIG. 19, the structure of the etching apparatus 50 is demonstrated first. The etching apparatus 50 includes an etching solution tank 51, a chamber 52, a transport unit 53, a recovery unit 55, and a shower 54. A shower nozzle 54 a is disposed in the chamber 52. The shower nozzle 54a communicates with one end of the shower pipe 54b. The other end of the shower pipe 54 b communicates with the etching solution tank 51. A shower pump 54c is disposed in the shower pipe 54b.

  The transport means 53 is disposed so as to pass through the chamber 52. The transport means 53 places the workpiece 56 and passes through the chamber 52. For example, a conveyor can be suitably used. The chamber 52 is provided with a recovery means 55 for recovering the etching solution sprayed on the workpiece 56 in the chamber 52. In FIG. 19, the recovery means 55 that recovers the etching solution by the funnel shape provided at the bottom of the chamber 52 is shown, but the invention is not limited to this. The chamber 52 is ventilated by the exhaust means 59. As the exhaust means 59, a duct with a fan or the like can be suitably used.

  The etching solution tank 51 is a container for storing an etching solution. The etching solution recovered by the recovery means 55 is returned here. The etching solution tank 51 is provided with a liquid discharge means 60. Here, although the liquid discharge means 60 shows the example comprised from the piping 60a and the discharge valve 60b, it is not limited to this. The discharge valve 60b can be electrically controlled.

  The etching solution tank 51 may be provided with a circulation means 58. The circulation means 58 prevents the solution components from being unevenly distributed by stirring the etching solution in the etching solution tank 51. Moreover, debris is removed by filtering during circulation. The circulation means 58 includes a circulation pipe 58a, a circulation pump 58b, and a filter 58c. Note that the present invention is not limited to this configuration.

  The etching solution tank 51 is provided with solution adding means 40. The solution adding means 40 adds a solution to the etching solution tank 51. In FIG. 19, an etching solution supply line 41 is shown. The etching solution supply line 41 includes a pipe 41a and a valve 41b. An upstream of the pipe 41a is connected to an etching solution storage tank (not shown). The valve 41b can be electrically controlled.

  The etching apparatus 50 operates as follows. The object 56 is moved on the transfer means 53 and moves in the chamber 52. In the chamber 52, a shower nozzle 54a communicating from the etching solution tank 51 via the shower pipe 54b is provided, and the etching solution is sprayed. The workpiece 56 is etched by receiving the spray of the etching solution.

  After being etched for a predetermined time, the workpiece 56 is unloaded from the chamber 52. When carrying out, it passes the washing | cleaning which is not shown in figure and the air shower which blows off a liquid component. However, the etching solution cannot be completely removed, and the carry-out liquid 57 adheres to the object to be processed 56 although it is a little. The etching solution sprayed into the chamber 52 is recovered by the recovery means 55 and returns to the etching solution tank 51.

  Next, the etching solution management device 5 will be described. The etching solution management device 5 has the same configuration except for the component concentration measuring device 1 and the control unit 20 shown in the first embodiment. Therefore, in the etching solution management apparatus 5, the code | symbol of a control part is set to 30. FIG. The inlet 10in of the sample pipe 10 is connected to the circulation pipe 58a closer to the circulation pump 58b (upstream side), and the outlet 10out is connected to the far side (downstream side).

  In the etching solution management device 5, a control line 34 for controlling the solution adding means 40 and a control line 36 for controlling the liquid discharging means 60 are added to the control unit 30 as compared with the component concentration measuring device 1. . In the present embodiment, the solution adding means 40 is an etching solution supply line 41. The control line 36 is connected to the discharge valve 60 b of the liquid discharge means 60. The control line 34 is connected to the valve 41b of the solution adding means 40 (etching solution supply line 41).

  The memory 30M connected to the control unit 30 stores an IR phosphate calibration curve, a UV nitric acid calibration curve, an IR nitric acid calibration curve (metal component calibration curve), and a phosphoric acid concentration lower limit value described later.

  The operation of the etching solution management apparatus 5 having the above configuration will be described. In the etching solution management device 5, the etching solution from the circulation pipe 58a of the etching solution tank 51 flows into the inlet 10in, and returns to the circulation pipe 58a from the outlet 10out. That is, the etching solution flows through the sample pipe 10. The control unit 30 confirms the temperature of the etching solution with the signal St from the thermometer 18. When the etching solution reaches a predetermined temperature, the control unit 30 causes the IR absorbance measurement device 16 and the UV absorbance measurement device 14 to measure the absorbance. The control unit 30 receives the respective measured values as the signal Sir and the signal Suv, and calculates the concentration of each component using a calibration curve.

  FIG. 20 shows the change of the concentration of each component thus determined with respect to the processing amount of the workpiece 56. Here, the processing amount is expressed as the number of processed sheets. In all graphs, the horizontal axis represents the number of processed sheets. FIG. 20A shows the relationship between the metal component (total metal ion amount) and the number of processed sheets. FIG. 20B shows the relationship between the phosphoric acid concentration and the number of processed sheets. FIG. 20C shows the relationship between the nitric acid concentration and the number of processed sheets. FIG. 20D shows the relationship between the etching rate (E / R) and the number of processed sheets.

  In any graph, when the number of processed sheets is zero, the etching solution is assumed to be a new solution. As the number of processed sheets increases, the metal component is increased by etching the workpiece 56 (FIG. 20A). On the other hand, as described in Embodiment 1 (FIG. 16), phosphoric acid is consumed by etching, and the phosphoric acid concentration decreases (FIG. 20B). As the phosphoric acid concentration decreases, the etching rate also decreases (FIG. 20 (d)). The nitric acid concentration does not change (FIG. 20 (c)).

  Here, it is the etching rate that limits the use of the etching solution. This is because a decrease in the etching rate may delay the manufacturing tact time and lead to an increase in defective products. Therefore, the etching solution is replaced when the etching rate falls below a predetermined value. In FIG. 20B, this time is represented by an arrow Pcg.

  In this case, the reference for determination is the lower limit of the etching rate (referred to as “E / R lower limit”). The lower limit of the etching rate may be a design value set in advance in the manufacturing process. Then, a lower limit value of the phosphoric acid concentration corresponding to the lower limit value of the etching rate is determined. This is called the “phosphoric acid concentration lower limit”. This memory lower limit value is stored in the memory 30M of the control unit 30.

  Referring to FIG. 19 again, the control unit 30 measures the component concentration of the etching solution at least every predetermined time. Therefore, when the phosphoric acid concentration falls below the lower limit of phosphoric acid concentration, it is determined that it is time to replace the currently used etching solution. In this case, an instruction Cst for temporarily stopping the etching process may be output to a control device or the like that controls the etching apparatus 50.

  Next, the control unit 30 transmits an instruction Cex for opening the discharge valve 60 b via the control line 36. The discharge valve 60b is opened in response to the instruction Cex, and the etching solution in the etching solution tank 51 is discharged.

  When the discharge of the etching solution is completed, the control unit 30 transmits an instruction Cex so as to close the discharge valve 60b. Next, the control unit 30 transmits an instruction Csl for opening the valve toward the valve 41 b of the solution adding means 40. The valve 41b opens upon receiving the instruction Csl, and adds the etching solution (new solution) to the etching solution tank 51. The above is called “new liquid replacement process”. The new liquid replacement process not only replaces all of the etching solution but also includes a process of replacing a part of the etching solution.

  When the replacement process of the new solution is completed, the phosphoric acid concentration of the etching solution also returns to the initial content, so that the etching rate also returns to the initial value (see FIG. 20). In this way, the etching solution management device 5 measures the phosphoric acid concentration in the etching solution as needed. When the phosphoric acid concentration falls below a predetermined value, the etching solution management device 5 determines that the etching rate has fallen below the predetermined value, and updates the etching solution. Can be replaced with liquid.

  It has been described that the control unit 30 directly controls the solution adding unit 40 and the liquid discharging unit 60 by the control lines 34 and 36. However, it may be said that the control unit 30 has controlled the liquid discharging means 60 and the solution adding means 40 if the instruction Csl for opening the valve 41b and the instruction Cex for opening the discharge valve 60b are output.

  In the above description, the new liquid replacement process is performed according to the phosphoric acid concentration. However, when the metal component concentration exceeds the metal component upper limit value by providing a “metal component upper limit value” for the metal component concentration, the new liquid replacement is performed. Processing may be performed. In this case, although not shown, the metal component upper limit value is recorded in the memory 30M (FIG. 19).

  Moreover, the control part 30 monitors nitric acid concentration similarly to phosphoric acid concentration (FIG.20 (c)). As described with reference to FIG. 16 of the first embodiment, the nitric acid concentration does not change even when the phosphoric acid concentration changes as etching progresses. However, if the nitric acid concentration decreases, it can be determined that some abnormality has occurred in the etching solution. That is, it is monitored that the nitric acid concentration does not change as well as the phosphoric acid concentration. And when there is an abnormality in the nitric acid concentration, the control unit 30 may send a signal to notify the abnormality.

(Embodiment 3)
FIG. 21 shows an etching solution management device 6 according to the present invention. The same parts as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, the solution adding means 40 has a phosphoric acid supply line 42. The phosphoric acid supply line 42 includes a pipe 42a and a valve 42b. An upstream of the pipe 42a is connected to a phosphoric acid tank (not shown). Of course, the valve 42b can be controlled to open and close by the instruction Cln from the controller 31.

  FIG. 22 is a graph showing the relationship with the number of processed sheets. In any graph, the horizontal axis indicates the number of processed sheets. FIG. 22A shows the relationship between the number of processed sheets and metal components. FIG. 22B shows the relationship between the phosphoric acid concentration and the number of processed sheets. FIG. 22C shows the relationship between the nitric acid concentration and the number of processed sheets. FIG. 22D shows the relationship between the etching rate (E / R) and the number of processed sheets.

  The etching solution management device 6 adds phosphoric acid when the number of processed sheets increases and the phosphoric acid concentration decreases and falls below a predetermined value. As shown in FIG. 17 of the first embodiment, the addition of phosphoric acid increases the phosphoric acid concentration and restores the etching rate. The determination to add phosphoric acid is made when the phosphoric acid concentration falls below a predetermined value. This predetermined value is referred to as “phosphoric acid additional concentration”. This additional concentration of phosphoric acid is higher than the lower limit of the phosphoric acid concentration. The phosphoric acid additional concentration is recorded in the memory 31M of the control unit 31.

  The control unit 31 compares the phosphoric acid concentration of the etching solution with the phosphoric acid additional concentration, and adds phosphoric acid from the phosphoric acid supply line 42 to the etching solution tank 51 when the phosphoric acid concentration falls below the phosphoric acid additional concentration. In FIG. 22B, the first phosphoric acid addition point is indicated by an arrow “Pln”. By adding phosphoric acid, the phosphoric acid concentration is restored, and the etching rate is also restored (FIG. 22D). On the other hand, the metal component in the etching solution gradually increases (FIG. 22 (a)). However, there is a metal component that adheres to the workpiece 56 and is taken out together with the carry-out liquid 57 and is saturated at a certain value.

  The control unit 31 measures the metal component concentration at a predetermined time interval, and determines that the metal component concentration at that time is saturated when the difference between the previous measurement value and the current measurement value becomes small. This is called a “metal component saturation value”.

  Since the etching solution management device 6 only adds phosphoric acid when the phosphoric acid concentration falls below the phosphoric acid addition concentration, it is not necessary to stop the etching device 50. This has the effect that the loss of tact time can be eliminated. Further, since phosphoric acid is added while the decrease in phosphoric acid concentration is small, the fluctuation range of the etching rate is small.

  Further, since the etching solution can be used for a long period of time, the cost of the etching solution is reduced, and the waste liquid treatment cost is low because there is almost no waste liquid. Although the phosphoric acid supply line 42 has been described by adding phosphoric acid, a concentrated etching solution containing nitric acid and having a low ratio of water may be added. This is because the phosphoric acid concentration increases.

  However, the amount of various minute components increases as the number of etching processes increases. Therefore, as shown in FIG. 22, after the metal component concentration is saturated (FIG. 22A), etching cannot be continued permanently by adding phosphoric acid, and the etching solution needs to be replaced with a new solution. In that case, the replacement | exchange process of an etching solution can be performed based on a metal component density | concentration.

  FIG. 22 shows a case where the metal component upper limit value is set below the metal component saturation value. When the metal component concentration exceeds the metal component upper limit value, a new liquid replacement process (see Embodiment 2) is performed. When this processing is performed, the “metal component upper limit value” is stored in the memory 31M (FIG. 21). In addition, after a predetermined number of sheets are processed after reaching the metal component saturation value, a new liquid replacement process may be performed. In this case, the “predetermined number of sheets” until the new liquid replacement process is performed is stored in the memory 31M. In either case, the etching solution is replaced based on the metal component concentration.

  Note that in this embodiment mode, the range of variation in the etching rate is reduced while phosphoric acid is added, so phosphoric acid is often added. For this reason, it is necessary to always monitor whether the etching solution is normal. Therefore, the nitric acid concentration is constantly monitored. If there is a change in the nitric acid concentration, the control unit 31 may send a signal to notify the abnormality.

(Embodiment 4)
FIG. 23 shows an etching solution management apparatus 7 according to the present invention. The same parts as those in Embodiment 2 are denoted by the same reference numerals, and description thereof is omitted. In this embodiment, a case where a large amount of moisture evaporates in the chamber 52 or the like will be described. When the amount of water evaporation is large, the increase in the phosphoric acid concentration due to the absence of water becomes larger than the decrease in the phosphoric acid concentration due to an increase in the number of treatments. As a result, according to the number of processed sheets, the phosphoric acid concentration increases and the etching rate increases.

  If the thin film is not etched slowly to some extent, the end face of the film may not be etched cleanly. Therefore, there is an upper limit on the etching rate. This is called the upper limit of the etching rate. There is a phosphoric acid concentration corresponding to the upper limit of the etching rate. This upper limit value of the phosphoric acid concentration is referred to as “phosphoric acid concentration upper limit value”.

  The etching solution management device 7 responds to the increase in phosphoric acid concentration. That is, it has a water supply line 43 for adding water when the phosphoric acid concentration exceeds a predetermined value. This predetermined value is called “phosphoric acid dilution concentration”. This phosphoric acid dilution concentration is lower than the phosphoric acid concentration upper limit. The phosphoric acid dilution concentration is stored in the memory 32M of the control unit 32.

  The control unit 32 compares the phosphoric acid concentration of the etching solution with the phosphoric acid dilution concentration, and adds water from the water supply line 43 to the etching solution tank 51 when the phosphoric acid concentration exceeds the phosphoric acid dilution concentration. In FIG. 24B, it is indicated by an arrow of Pwa. The addition of water reduces the phosphoric acid concentration and the etching rate. On the other hand, the metal component in the etching solution gradually increases. However, there is a metal component that is taken out together with the carry-out liquid 57 adhering to the object to be processed 56 and is saturated at a certain value.

  Since the etching solution management device 7 only adds water when the phosphoric acid concentration exceeds the phosphoric acid dilution concentration, it is not necessary to stop the etching device 50. This can eliminate the loss of tact time. Further, since phosphoric acid is added while the decrease in phosphoric acid concentration is small, the fluctuation range of the etching rate is small.

  In addition, since it can be used for a long period of time, the cost of the etching solution is reduced, and since there is almost no waste liquid, the cost of waste liquid treatment is also low. The replacement of the etching solution can be performed based on the metal component concentration, as in the case of the third embodiment. When the new liquid replacement process is performed based on the metal component concentration, the “metal component upper limit value” or the “predetermined number” after reaching the metal component saturation value is stored in the memory 32M.

  In this embodiment, since the etching solution water evaporates, the nitric acid concentration also increases (FIG. 24C). Therefore, it can be seen that the evaporation of water occurs even if the change in the nitric acid concentration is monitored. In addition, since the change in nitric acid concentration is synchronized with the change in phosphoric acid concentration, the presence or absence of abnormality in the etching solution can be grasped by monitoring the nitric acid concentration. When the change in nitric acid concentration does not synchronize with the change in phosphoric acid concentration, or when it does not change conversely, it may be determined that an abnormality has occurred in the etching solution, and the control unit 32 may transmit a signal indicating the abnormality.

  Since the etching solution component concentration measuring method and the etching solution management method according to the present invention can measure the concentrations of phosphoric acid and nitric acid and the metal ion concentration individually only by using absorbance as a result, phosphoric acid It can be widely used in places where an etching solution made of nitric acid and nitric acid is used.

1 component concentration measuring device 10 sample pipe 10 in inlet 10 out outlet 12 heat exchanger 12 in water inlet 12 out water outlet 14 UV absorbance measuring device 16 IR absorbance measuring device 18 thermometer 20 control unit 20M memory 24 display devices 30, 31, 32 Control unit 30M, 31M, 32M Memory 40 Solution addition means 41 Etching solution supply line 41a Pipe 41b Valve 42 Phosphoric acid supply line 42a Pipe 42b Valve 43 Water supply line 43a Pipe 43b Valve
50 Etching apparatus 51 Etching solution tank 52 Chamber 53 Conveying means 54 Shower 54a Shower nozzle 54b Shower pipe 54c Shower pump 55 Recovery means 56 Object to be treated 57 Take-out liquid 58 Circulating means 58a Circulating pipe 58b Circulating pump 58c Filter 60 Liquid discharging means 60a Pipe 60b Discharge valve L10 Neutralization titration curve L12 of nitric acid Neutralization titration curve L14 when ZnO powder is dissolved in nitric acid Neutralization titration curve L16 of phosphoric acid Neutralization when ZnO powder is dissolved in phosphoric acid Titration curves A1, A2 Inflection point L13 Neutralization titration curve of phosphoric acid L132 Secondary differential curve P1 of L13, peak value L20 of L132 L20 Neutralization titration curve L22 when 0 ppm of Zn is contained in phosphoric acid Neutralization titration curve L24 containing 1230 ppm Zn The etching rate at which the phosphoric acid concentration PP phosphate concentrations compensation to restore the neutralization titration curve P + etch rate when incorporated 2970ppm of Zn in the supplemented until P +

Claims (13)

A component concentration measuring apparatus for measuring a component concentration of an etching solution containing phosphoric acid and nitric acid stored in an etching solution tank and etching a thin film containing metal,
A sampling pipe through which the etching solution in the etching solution tank flows;
An IR absorbance measuring device provided in the middle of the sampling pipe;
A control unit connected to the IR absorbance measurement device;
The control unit calculates a phosphoric acid concentration in the etching solution based on an IR phosphoric acid calibration curve stored in advance ,
A metal component calibration curve indicating the relationship between the absorbance of nitric acid measured in advance with the IR absorbance measurement device and the concentration of the metal component in the etching solution is stored, the measurement result of the absorbance of nitric acid with the IR absorbance measurement device, An apparatus for measuring a concentration of a component in an etching solution, wherein the concentration of the metal in the etching solution is calculated from a metal component calibration curve . In the middle of the sampling pipe, a UV absorbance measuring device that measures absorbance in a wavelength band of 280 to 320 nm,
2. The etching solution according to claim 1, wherein the control unit is also connected to the UV absorbance measurement device and calculates a nitric acid concentration in the etching solution based on a UV nitric acid calibration curve stored in advance. Ingredient concentration measuring device. 3. The etching solution component concentration measuring device according to claim 2 , further comprising a heat exchanger upstream of the IR absorbance measuring device and the UV absorbance measuring device of the sampling pipe. Constituent concentration measuring apparatus of the etching solution described in any one of claims 1 to 3 thin film is characterized by comprising an oxide semiconductor of indium, gallium, zinc and oxygen containing said metal. An etching solution management device for managing component concentrations of an etching solution containing phosphoric acid and nitric acid stored in an etching solution tank having a liquid discharging means for etching a thin film containing metal,
A sampling pipe through which the etching solution in the etching solution tank flows;
An IR absorbance measuring device provided in the middle of the sampling pipe;
A controller connected to the IR absorbance measuring device;
A solution adding means for adding a solution to the etching solution tank;
The controller is
Calculate the phosphoric acid concentration in the etching solution based on the IR phosphoric acid calibration curve stored in advance,
Controlling the solution adding means based on the phosphoric acid concentration ;
A metal component calibration curve indicating the relationship between the absorbance of nitric acid measured in advance with the IR absorbance measurement device and the concentration of the metal component in the etching solution is stored, the measurement result of the absorbance of nitric acid with the IR absorbance measurement device, An etching solution management apparatus that calculates a metal component concentration in the etching solution from a metal component calibration curve . In the middle of the sampling pipe, a UV absorbance measuring device that measures absorbance in a wavelength band of 280 to 320 nm,
6. The etching solution according to claim 5 , wherein the control unit is also connected to the UV absorbance measuring device and calculates a nitric acid concentration in the etching solution based on a UV nitric acid calibration curve stored in advance. Management device. The etching solution management device according to any one of claims 5 and 6 , further comprising a heat exchanger at least upstream of the IR absorbance measuring device of the sampling pipe. Etching solution management apparatus according to any one of claims 5 to 7, characterized in that an oxide semiconductor thin film containing the metal of indium, gallium, zinc, and oxygen. Wherein, the etching solution management apparatus according to any one of claims 5 to 8, wherein the controller controls the liquid discharge means on the basis of the concentration of phosphoric acid. The solution adding means is means for adding at least an etching solution to the etching solution tank,
The controller is based on the phosphoric acid concentration.
Controlling the liquid discharge means to discard the solution in the etching solution tank;
The etching solution management apparatus according to claim 9 , wherein the etching solution is added to the etching solution tank by controlling the solution adding unit. The solution adding means is means for adding at least a phosphoric acid solution to the etching solution tank,
The said control part adds the said phosphoric acid solution to the said etching solution tank by the said solution addition means based on the said phosphoric acid density | concentration, The claim in any one of Claim 5 or 6 characterized by the above-mentioned. Etching solution management device. The solution adding means is means for adding water to the etching solution tank,
The said control part adds the said water to the said etching solution tank by the said solution addition means based on the said phosphoric acid density | concentration, The etching solution described in the claim in any one of Claim 5 or 6 characterized by the above-mentioned. Management device. The solution adding means is means for adding an etching solution to the etching solution tank,
The control unit is based on the metal component concentration,
Controlling the liquid discharge means to discard the solution in the etching solution tank;
Etch solution management apparatus according to any one of claims 9 to 12, characterized in that adding the etching solution in the etching solution tank by controlling the solution additional means.