JP3347802B2 - Solution concentration control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution concentration control device, and more particularly to a device for controlling the concentration of a solution by measuring the conductivity of a solution, which corrects a measurement error of a concentration of a solute other than a target component. To a solution concentration control device.

[0002]

2. Description of the Related Art As a method of measuring the conductivity of a solution for controlling the concentration of the solution, an AC voltage is applied between electrodes of platinum or stainless steel or the like opposed to the solution. A method of determining the liquid resistance from the amount of current, and immersing a pair of toroidal coils in a solution, applying an alternating current to one of the coils, measuring the amount of alternating current induced in the other coil, and measuring the inductance of the coil. There is known a method of measuring a change in concentration based on a change in the amount of ions therein.

However, whichever method is used,
For example, in a solution containing a single component of acid or alkali, its concentration is always proportional to the electrical conductivity, but even if the solution initially contains a single component acid, such as a metal pickling solution, as the cleaning process proceeds, In the case where the metal is dissolved, the conductivity of the whole liquid is not proportional to the acid concentration to be measured due to the increase of the eluted ions, errors gradually accumulate, and accurate control of the acid concentration becomes impossible. The same applies to the alkaline solution, which may be caused by a difference in the moving speed of dissolved foreign ions.

[0004] As a specific case, for example, in the process of derusting iron with hydrochloric acid, free hydrochloric acid has the ability to dissolve iron rust, while ferrous chloride produced by dissolving iron rust in hydrochloric acid is capable of dissolving iron. Since it has no dissolving ability, it is necessary to constantly measure the concentration of free hydrochloric acid during the derusting process to keep the derusting ability constant. However, as the ferrous chloride in the solution decreases the conductivity of the solution due to its increase, the measured conductivity of the solution is indicated to be lower than the value originally derived from free hydrochloric acid as the pickling process proceeds. For this reason, an error occurs in the measurement of the free hydrochloric acid concentration using the electric conductivity as a scale, and the amount of the supplied hydrochloric acid gradually becomes excessive, so that it is impossible to properly control the liquid concentration.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of the prior art and eliminate errors caused by factors other than the concentration of a desired component when measuring a solution concentration based on its conductivity. An object of the present invention is to provide a solution concentration management device capable of performing solution management.

[0006]

SUMMARY OF THE INVENTION The problems of the prior art are as follows.
The concentration of a specific component in the solution is measured based on the conductivity of the solution, and in a solution concentration management device adapted to always maintain the concentration at a predetermined value, the device continuously adjusts the conductivity of the solution. A continuous concentration measuring unit having a first concentration sensor for measuring and outputting a measurement signal corresponding to the concentration, a titration nozzle immersed in an analysis cell for a sample of the solution, and A burette that supplies a titrant for the specific component at a predetermined time interval, and a second concentration sensor that outputs a concentration measurement signal by a liquid junction potential difference caused by a titration reaction of the specific component in the solution with the titrant. The measurement signal from the concentration titration analysis unit and the continuous concentration measurement unit is processed, and the obtained concentration data is compared with a preset reference concentration value and continuously output to the liquid supply unit. A control unit that operates the concentration titration analysis unit at predetermined time intervals and intermittently corrects a measurement signal from the continuous concentration measurement unit with a concentration measurement signal obtained by the titration. This is achieved by a solution concentration control device.

[0007]

In the present invention, the concentration of a specific component in a solution to be controlled is measured based on the conductivity, and the specific component is added to the solution according to the difference between the measured value and a predetermined reference concentration value. When replenishing, the concentration of the specific component of the solution is continuously measured by the first concentration sensor of the continuous concentration measuring unit provided in the solution, and the measurement signal is calculated by the control unit and converted into a concentration value. Is done.

This concentration value is compared with a predetermined reference value, and the comparison output is output to an external liquid replenishing unit, so that the replenisher is continuously supplied so that the concentration of the solution always becomes a predetermined value.

Here, if products other than the predetermined component accumulate in the solution with the progress of the process, the conductivity corresponding to the concentration of the predetermined component is not necessarily proportional to the concentration. The measured conductivity output shows a lower value than the original concentration value. When such errors accumulate, the concentration of the predetermined component of the solution is gradually controlled to an excessive side, and the solution concentration is not properly managed.

In the present invention, the concentration titration analyzer is operated at predetermined time intervals by a controller, and a titrant for measuring the concentration of a specific component in the solution is dropped on the sample solution in the analysis cell. Allow a titration reaction to take place. In this titration reaction, apart from the measurement of the concentration of the solution by the electric conductivity, only the concentration of the specific component in the solution is accurately measured. This density measurement signal is output to the control unit and used for correcting an arithmetic expression when converting the measurement signal from the continuous density measurement unit into a density value, and the converted value matches the density value of the specific component at this time. Let it do. Therefore, a command signal corresponding to the required amount of replenisher at that time is always output to the replenisher.

In the present invention, the concentration of a specific component of the solution is always continuously measured by the continuous concentration measuring section, and errors occurring during the processing steps are corrected at predetermined time intervals by measurement by the concentration titration analyzing section. Generally, it takes 10 to 20 seconds or more to complete the titration reaction in the automatic analysis. However, by setting the timing of the titration operation appropriately according to the purpose, the concentration of the specific component of the solution is practically always substantially constant. And can be controlled continuously.

As a first concentration sensor used in the continuous electric concentration measuring section, it is common to provide a pair of electrodes such as platinum or stainless steel as described above and measure the electric conductivity by the liquid resistance between them. It is a target. However, in this case, there is a possibility that an accurate solution resistance may not be measured due to dissolution of the electrode surface into the solution, deterioration of the electrode, or adhesion of dirt.

On the other hand, a pair of electromagnetic coils is provided to induce an alternating current on the secondary coil side by the alternating current applied to the primary coil side, and the fact that the current value is changed by the conductance which changes due to the change in the concentration of the solution is used. In the electromagnetic sensor, since it is not necessary to bring the sensor surface into contact with the liquid, it can be coated with an inert substance such as plastic, and an accurate measurement output can be obtained over a long period of time.

As the second concentration sensor immersed in the analysis cell of the concentration titration analyzer for titration analysis, any known sensor can be used. For example, the second concentration sensor can be used for the acid / alkali concentration analysis of the process solution. In this case, a general pH electrode (glass electrode) or the like is used.

However, in the case of a glass electrode, a reference electrode filled with an internal solution such as potassium chloride is required, and since this internal solution oozes out of the joint portion during use, it needs to be replenished. In the case of alkali, the glass material is eluted, so that its service life is limited.

According to the present inventor, in such a case, even if a pair of platinum electrodes immersed in a sample solution is used in place of the pH electrode, the pH electrode is used as a concentration sensor for titration of acid / alkali. It was found that almost the same measurement results were obtained.

For example, a platinum wire having an appropriate diameter as one platinum electrode is accommodated in the flow path of a titration nozzle of a titrator immersed in the solution of the analysis cell, and the tip of the electrode is brought into contact with the sample solution of the analysis cell. As the other platinum electrode, a platinum plate or a platinum rod may simply be immersed in a position facing the titration nozzle in the analysis cell. As a result, an inter-liquid electrode is formed at the part where the analysis sample and the titrant are in contact with each other at the time of titration, and a clear potential change is obtained at the end point of the titration, which sufficiently functions as a concentration sensor at the time of titration analysis. The sensor electrode is Pt
In addition to / Pt, Au / Au or carbon / carbon which is inert to the measurement solution and forms a clear liquid junction potential
Other arbitrary combinations of materials such as carbon can be used.

In the present invention, when the analysis sample is quantitatively collected at the time of titration measurement of the solution, if the measurement is performed on a volume basis as is generally performed, air bubbles are mixed in the sample in the case of the actual liquid used. An error may occur in the analysis value. In addition, a sampling buret, a large number of solenoid valves, and the like are required for volume-based liquid sampling, which complicates the configuration of the apparatus and increases the frequency of occurrence of a failure.

For this reason, in a preferred embodiment of the present invention, a sample is sampled into an analysis cell on a weight basis. As a specific means, the analysis cell for putting the sample is mounted on a load cell as a weight sensor. Then, the weight data output by the load cell according to the sample weight is sent to the control unit, and is used as a parameter for calculating the concentration value of the solution obtained by titration analysis.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a flowchart showing the outline of the apparatus of the present invention.
FIG. 2 is a graph showing a titration curve obtained by a concentration sensor used for titration analysis of the present invention, and FIG. 3 is a graph showing a titration curve obtained by a concentration sensor used for conventional titration analysis.

FIG. 1 is a flow chart showing the outline of the case where the present invention is applied to an automatic analyzer of an alkali developing solution. A process solution for processing is an alkali developing solution containing sodium carbonate set to about 1% concentration. It is.

As shown in FIG. 1, the apparatus of this embodiment controls a continuous concentration measuring section I based on the conductivity of an alkaline solution, a concentration titration analyzing section II by neutralization titration of an alkaline solution with hydrochloric acid, and controls the operations of these sections. And a controller III for outputting a replenishment command signal to a replenisher (not shown) for the alkaline solution. The continuous concentration measuring section I has an electromagnetic sensor 1 provided as a first concentration sensor, for example, provided in a part of a liquid tank of an alkaline developer, and continuously measures the concentration of the alkaline solution based on its conductance. It has been made like that.

The electromagnetic sensor 1 is comprised of a pair of toroidal coils 3 (3) which are incorporated in a housing 2 through which an alkaline solution can flow and are electromagnetically coupled to each other using the solution as a medium. The secondary coil 3 is connected to an AC signal oscillation source (not shown) for generating an induced current. Here, the measurement signal based on the current induced in the secondary coil 3 is proportional to the conductance of the solution to be measured,
Therefore, in principle, the measurement signal is proportional to the alkali concentration of the solution. The outer peripheral surface of each coil 3 (3) is molded with a corrosion-resistant plastic. The measurement signal from the secondary coil 3 is connected via a converter 4 to a control unit III described later.

The concentration titration analysis section II has an analysis cell 5 filled with a sample of an alkali developing solution and a load cell 7 on which the analysis cell 5 is placed via a balance beam 6. The nozzle 8 is facing.

In FIG. 1, reference numeral 9 denotes a measurement burette for measuring the sample concentration of the alkaline solution in the analysis cell 5 by titration. The measurement burette 9 is selectively connected to the titration nozzle 8 and the titration solution tank 10. It has been made to be.

The analysis cell 5 is provided with a pair of platinum electrodes 12 and 13 as a second concentration sensor 11 so as to be in contact with the sample solution to be filled. One platinum electrode 1
2 is inserted into the liquid supply passage having an inner diameter of about 2 mm of the titration nozzle 8 so that the tip is in contact with the sample liquid, and the other platinum electrode 13 is immersed in a sample solution of about 1 mmΦ platinum wire. I have.

In the figures, 14 is a stirrer for the sample solution in the analysis cell 5, 15 is a pump for draining water from the analysis cell 5, S
V1 is a solenoid valve for supplying a sample, SV2 is a solenoid valve for supplying a washing water, SV3 is a solenoid valve for discharging a sample, SV4 is a solenoid valve for supplying a titrant from a titration burette 9, and SV5 is a solenoid valve for a titrant tank 10. A solenoid valve for supplying a titrant to the burette 9.

The control unit III is composed of a microcomputer. The A / D converter 16 converts the output signal from the converter 4 of the continuous concentration measurement unit II, and the titration is performed by the concentration measurement sensor 11 of the concentration titration analysis unit II. An A / D converter 17 for inputting the alkali concentration signal and the weight data signal of the analysis cell weight (sample weight) from the load cell 7 under the switching of the switch SW and converting them, and these converters 16 and 17
And a CPU 18 for processing an input signal from the CPU.

The CPU 18 controls a density calculation and a correction process to be described later according to a predetermined program, outputs the result to a display 19 and a printer 20, and based on the calculated output signal, a developing solution outside the apparatus. It outputs a replenishment command output A to a replenishment unit (not shown), upper and lower concentration alarm outputs B and C, a system alarm output D, and the like. In addition, reference numeral 21 in the figure denotes each of the solenoid valves SV1 to SV5, the burette 9 and the pump 1.
4 is a driver for outputting a command signal from the CPU 18 for operation control.

The operation of the automatic analyzer for automatic developer development of this embodiment will be described below with reference to the drawings. The binder polymer of the photoresist to be processed is solubilized by neutralizing the terminal carboxyl groups with Na ⁺ ions in the developer to form a carboxylate, and is dissolved in the solution as the processing with the alkaline developer proceeds. Dissolve.

The concentration of sodium carbonate in the alkali developer is usually set to about 1%. However, the alkali concentration is reduced by the above-described neutralization together with the development processing, and the developing ability is reduced. It is constantly monitored by the electromagnetic sensor 1 of the continuous concentration measuring section I. That is, since the electromagnetic coupling between the pair of coils 3 (3) provided in the housing 2 is changed by the conductance of the liquid due to the decrease in the alkali concentration of the solution, this is converted into a continuous concentration measurement signal by the control unit III. A / D converter 16 to CP
Input to U18. The CPU 18 converts the signal into data of the concentration of the solution according to a predetermined arithmetic expression programmed in advance as data, and displays the signal on the display 19 and the printer 20.
To display and print out. Further CP
U18 compares the obtained density data with a preset density reference value and outputs an output command signal A corresponding to the amount of the alkali developing solution to be replenished to the developing tank to the liquid replenishing unit. As a result, a required amount of the alkali developing solution is replenished from the liquid replenishing unit, and the alkali concentration in the developing tank is restored to a predetermined value.

When the alkali concentration deviates from a predetermined reference value to some extent, upper and lower concentration alarms B and C are indicated, and when an abnormally high (low) value is indicated, a system alarm D is issued.
Are output respectively.

In this manner, the alkali concentration in the developing tank is controlled to a predetermined value in principle continuously by detection by the electromagnetic sensor 1. However, as the development process on the photoresist proceeds and the binder polymer dissolves in the alkali developer, the output of the electromagnetic sensor 1 decreases not only with the decrease in the alkali concentration, but also due to the change in the solution composition due to the elution of the polymer. Because of the decrease, the measured output does not always correspond exactly to the decrease in alkali concentration. When the alkali developing solution is replenished under control according to the measurement output including such an error, the alkali concentration in the tank gradually becomes excessive, and proper concentration management becomes impossible.

For this reason, in the apparatus of this embodiment, the alkali concentration of the alkali developer is measured at predetermined time intervals by the concentration titration analysis section (II), and the measurement result by the continuous concentration measurement section I is obtained based on the measurement result. The correction is automatically made and the alkali concentration of the developer is set to an appropriate value each time.

That is, under the control of the CPU 18 of the control unit III, the washing water supply solenoid valve SV2 is opened at predetermined time intervals (for example, 20 minutes) to supply the washing water into the analysis cell 5, and the agitator 14 Then, the solenoid valve SV3 is opened and drainage is performed by operating the drainage pump 15.

Next, the solenoid valve SV1 is opened to inject a sample of the alkaline developer into the analysis cell 5, and the weight (total weight-cell tare weight) is transmitted to the load cell 7 via the beam 6. The weight detection data of the load cell 7 is transmitted to the A / D converter 1 of the control unit III via the changeover switch SW.
7 is input to the CPU 18 and used as a parameter for density calculation.

Then, the solenoid valve SV5 is opened and the titration burette 9 is operated to collect 1N-hydrochloric acid from the titrant tank 10 into the titration buret 9. Then, the solenoid valve SV4 is opened and hydrochloric acid is supplied through the measuring nozzle 8 to a predetermined amount. Each of them is dropped into the alkaline developer in the analysis cell 5.

As a result, the following two-stage neutralization titration reaction occurs between sodium carbonate and hydrochloric acid in the analysis cell 5. Na ₂ CO ₃ + HCl = NaHCO ₃ + NaCl (1) NaHCO ₃ + HCl = H ₂ CO ₃ + NaCl (2) In this case, there is a liquid junction potential between the platinum electrodes 12 and 13 of the second concentration sensor 11. In response to the sudden change in the pH value at each end point of the titration reaction corresponding to the equations (1) and (2), as shown in FIG. In the titer of hydrochloric acid (ml on the horizontal axis of the graph), a clear change is shown in the liquid junction potential (mV on the vertical axis of the graph).

FIG. 2 shows a titration curve when a similar alkaline developer is titrated with 1N hydrochloric acid using a conventional pH electrode (glass electrode). As is clear from the comparison between FIG. 2 and FIG. 3, the tendency of both titration curves agrees well, and the dropping amount of hydrochloric acid at the first end point p1 and the second end point p2 in FIG.
, Which indicates that titration is possible with a platinum / platinum electrode as well as with a pH electrode (glass electrode).

The measured potential signal of the alkali concentration from the concentration sensor 11 obtained by such titration is supplied to the control unit.
It is input to the CPU 18 via the III changeover switch SW and the A / D converter 17. Here already load cell 7
The alkali concentration data by titration is calculated using the weight data of the sample input from the above as a parameter.

The result of this operation is used to correct the coefficients of the operation expression when the CPU 18 converts the measurement signal from the electromagnetic sensor 1 into density output data. That is, the electromagnetic sensor 1 caused by the dissolution of the binder polymer in the resist
The error in the measurement signal is corrected by the titration concentration signal indicating the alkali concentration at the time of this titration, and the replenishment command output signal A from the CPU 18 exactly corresponds to the replenishment amount of the alkali concentration at that point. Thereafter, by performing correction by the titration analysis at predetermined time intervals, an error included in the concentration measurement signal of the alkaline developer by the electromagnetic sensor 1 is corrected each time, and an appropriate solution concentration is managed through development processing.

[0043]

As described above, in the apparatus according to the present embodiment, the concentration of the alkali developing solution is constantly measured by the electromagnetic sensor 1 based on the conductance of the solution, and the concentration value based on the measured output and the predetermined reference concentration value are compared. Is obtained by the CPU 18 and a corresponding replenishment command output signal is output to the liquid replenishment unit, so that the alkali concentration of the developer is continuously maintained at a substantially constant value. Then, in combination with such a continuous measurement, the concentration titration analyzer II capable of accurately measuring only the alkali concentration of the developer is operated at predetermined time intervals to prepare a concentration measurement signal by titration, thereby The error contained in the measurement signal of the electromagnetic sensor 1 is reduced by the CPU 1 by the photoresist binder polymer that melts as the development proceeds.
Since the correction is made at the time of the calculation of 8, the alkali concentration of the developing solution is substantially always recovered to a predetermined value, and proper concentration management can be performed throughout the developing operation.

In this titration analysis, the analysis cell 5
Is placed on the load cell 7 so that the sample is sampled on a weight basis, and even if bubbles are mixed in the sample, the error due to the measurement of bubbles as in the case of the conventional volume-based sampling is obtained. Is avoided, and the component configuration of the apparatus is simplified and the frequency of occurrence of failures is reduced as compared with the case of volume-based liquid sampling.

Further, since a pair of platinum electrodes is used as a concentration sensor in titration analysis, the replenishment of the solution due to leakage of the internal solution or elution of the electrode glass material into the alkaline developer as in the case of the conventional pH electrode. Also, there is no need for electrode replacement, the structure is simple and robust, and the sensor life is extended.

In this embodiment, the control of the liquid concentration in the case of treating the photoresist with a sodium carbonate developing solution has been described. However, the present invention is not limited to this, and the control of the liquid concentration by measuring the conductivity of the liquid is not limited to this. The same applies to other general cases that may be interfered by the elution of solutes other than the predetermined component to bet.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of the apparatus of the present invention.

FIG. 2 is a graph showing a titration curve obtained by a concentration sensor used for titration of the present invention.

FIG. 3 is a graph showing a titration curve obtained by a conventional concentration sensor used for titration.

[Explanation of symbols]

 I: Continuous concentration measurement unit II: Concentration titration analysis unit III: Control unit 1: Electromagnetic sensor (first concentration sensor) 2: Housing 3: Coil 4: Converter 5: Analysis cell 6: Beam 7: Load cell 8: Titration Nozzle 9 Titration burette 10 Titrant tank 11 Second concentration sensor 12, 13 Platinum electrode 14 Stirrer 15 Drainage pump 16, 17 A / D converter 18 CPU 19 Display 20 Printer 21 … Driver SV1 to SV5… Solenoid valve A… Liquid replenishment command output signal B… Upper limit alarm output signal C… Lower limit alarm output signal D… System alarm output signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-35351 (JP, A) JP-A-64-21344 (JP, A) JP-A-5-18926 (JP, A) JP-A 53-185 128386 (JP, A) Special Table 60-502114 (JP, A) International Publication No. 91/11708 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/00-27 / 10 G01N 27/26 341

Claims (3)

(57) [Claims] 1. A solution concentration control device for measuring the concentration of a specific component in a solution based on the conductivity of the solution and always maintaining the concentration at a predetermined value. A continuous concentration measuring unit having a first concentration sensor that continuously measures the degree and outputs a measurement signal corresponding to the concentration, a titration nozzle immersed in an analysis cell for the solution sample, and a titration nozzle. In contrast, a burette that supplies a titrant for the specific component in the solution at a predetermined time interval, and a second that outputs a concentration measurement signal based on a potential difference between liquids generated by a titration reaction of the specific component in the solution with the titrant. A concentration titration analysis unit having a concentration sensor, and processing the measurement signal from the continuous concentration measurement unit, and comparing the obtained concentration data with a preset reference concentration value to the liquid replenishment unit. A control unit for continuously outputting and operating the concentration titration analysis unit at predetermined time intervals, and intermittently correcting the measurement signal from the continuous concentration measurement unit with a concentration measurement signal by the titration. A solution concentration management device comprising: 2. The method according to claim 2, wherein the continuous concentration measuring unit is provided in the solution, and the primary coil to which an alternating current is applied is electromagnetically coupled to the primary coil using the solution as a medium, and an alternating current corresponding to the conductance of the solution is induced. The solution concentration management device according to claim 1, wherein the device is an electromagnetic sensor including a secondary coil. 3. The analysis cell is mounted on a load cell that weighs an analysis sample and provides weight data as a parameter for concentration measurement to a control unit.
The solution concentration control device according to the above.