JPH05346402A - Si concentration monitor in chemical solution - Google Patents

Abstract

(57) [Summary] [Purpose] Si in a chemical solution capable of stable oxide film removal while maintaining a constant etching rate by accurately and quickly measuring a small amount of Si in an etching solution (HF) for semiconductor wafers. PROBLEM TO BE SOLVED: To provide a concentration monitoring device [Configuration] An etching solution and a carrier (pure water) are alternately sampled and sent out, and a first reaction solution (a mixed solution of ammonium molybdate and boric acid) is mixed thereinto at 80 ° C.
It is heated to the following and the color development is measured by an absorbance measuring means. Further, the Si concentration in the treatment liquid is monitored, a new treatment liquid is replenished, and this is circulated and mixed. Further, the second reaction liquid (a mixed liquid of 4-amino-3-hydroxynaphthalenesulfonic acid and sodium sulfite) is mixed and heated with the mixed liquid to measure the Si concentration with high sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing Si dissolved in a liquid by a wet process, and more particularly to a method and an apparatus for monitoring Si concentration in a chemical solution in a step of etching Si oxide with a HF chemical solution.

[0002]

2. Description of the Related Art In the conventional wet etching process for semiconductor wafers, there is no method for easily monitoring the state of the etching solution. Therefore, it is empirical to estimate the life of the etching solution from the dummy Si wafer etch rate. I decided to decide the number of sheets to process. JIS K-0101-1
The industrial water test method of 986 describes the method for measuring Si. There are (1) molybdenum yellow method and (2) molybdenum blue method as the above Si measuring methods,
The molybdenum blue method is used for microanalysis.

In the molybdenum yellow method, the Si concentration is analyzed by measuring the yellow absorbance based on the heteropoly compound produced by the reaction between Si and ammonium molybdate. In the molybdenum blue method, the heteropoly compound is further reduced with 4-amino-3-hydroxynaphthalene sulfonic acid and the blue absorbance thereof is measured to analyze the Si concentration.

Further, Japanese Patent Application Laid-Open No. 63-226932 discloses monitoring the change in the concentration of the material to be etched dissolved in the chemical liquid for wet processing of semiconductors by optical emission analysis. Further, Japanese Patent Laid-Open No. 64-68483 discloses an existing data storage system in which the absorbance of the absorption spectrum wavelength of the etching solution detected by a spectrophotometer is stored in a personal computer.
It is disclosed that the fatigue level of the etching solution is detected in comparison with that of the etching solution, the conveyance speed of the processing object is set based on the result, and a new solution is replenished so as to keep the etching ability of the etching solution constant. ing.

[0005]

The above-mentioned wet analysis has a problem that it takes much time because it is manually operated. For example, in the etching process of semiconductor wafers, the sampled etchant was transported to the analyzer for analysis each time, so it was not possible to grasp the state of the etchant in real time, and it took time and several There was no choice but to estimate empirically the state of the etching solution before the lapse of time.

Analytical Chemistry Vol. 38,419 (198
9) describes a method for continuous and automatic analysis of Si for the purpose of monitoring a small amount of Si in industrial water such as a boiler. However, a minute amount of Si concentration in an etching solution such as HF can be measured. In addition, there is a problem in that it cannot follow a rapid change in the concentration of the etching solution due to the processing of the Si wafer and the like. The object of the present invention is to trace S in the above HF drug solution.
i can be measured accurately and quickly, and S
Provided is a device for monitoring the Si concentration in a chemical solution, in which the degree of fatigue of the chemical solution is obtained from the concentration of the amount of Si dissolved in the HF chemical solution by removing the i oxide film, and the oxide film is stably removed while always maintaining a constant etching rate. To do.

[0007]

In order to solve the above problems, a predetermined amount of a wafer processing liquid and a carrier (pure water) is alternately sampled and sent out, and a first reaction liquid (ammonium molybdate and 80) by mixing a mixture of boric acid)
It is heated to a temperature of not higher than 0 ° C., and its color development is measured by an absorbance measuring means. Further, the Si concentration in the treatment liquid is monitored, a new treatment liquid is replenished, and this is circulated and mixed.

Therefore, a control tank for supplying a predetermined amount of the new processing liquid containing a predetermined amount of HF liquid and pure water and a predetermined amount of the new processing liquid to the processing tank and / or the buffer tank for storing the processing liquid. Means and means for circulatingly mixing the treatment liquid through the treatment tank and the buffer tank are provided. Further, the processing liquid, each replenishing liquid, the carrier, the reaction liquid,
The tanks for storing the waste liquid and the like, the sampling means, the first mixing means, the heating means, the replenishment of the processing liquid, the circulation mixing means, and the like are integrally housed in a rack with casters so as to be movable.

A second reaction liquid (a liquid mixture of 4-amino-3-hydroxynaphthalene sulfonic acid and sodium sulfite) is mixed with the above liquid mixture and heated. Immediately before the first mixing means, the second reaction solution is produced by mixing a mixed solution of ammonium molybdate and boric acid with hydrochloric acid or sulfuric acid.

[0010]

The wafer processing solution and the carrier (pure water) are sampled in predetermined amounts to dilute the processing solution to a predetermined concentration. Boric acid in the first reaction liquid masks the fluorine component in the reaction liquid (HF) in the molybdate yellow method, and ammonium molybdate reacts with Si. Further, the heating at 80 ° C. or lower accelerates the reaction rate of the ammonium molybdate and Si.

Further, the second reaction liquid (4-amino 3-
The mixed solution of hydroxynaphthalenesulfonic acid and sodium sulfite) reduces the sample reacted with the heteropoly compound in the first reaction solution, and enables the Si concentration measurement at the ppb level by the molybdenum bull method.

In the case of measuring Si in pure water, since the sample is not acidic, the pH value of the sample is adjusted with hydrochloric acid or sulfuric acid, and the hydrochloric acid or sulfuric acid is added to the first reaction solution immediately before the heating reaction. And hydrogen peroxide to prevent decomposition and to react the ammonium molybdate with Si. Further, the Si concentration monitor in the treatment liquid, a replenishment, circulation, and mixing means of a new treatment liquid prevent deterioration of the treatment liquid to enable continuous Si concentration measurement, and the rack with casters is Allows the devices to be moved together.

[0013]

1 is a block diagram of an apparatus for measuring Si concentration in a chemical solution according to the present invention. The processing liquid (HF) 2 in the processing tank is sucked by the pump 1 and is sampled by the sample loop 4 of the switching valve 3 in a fixed amount. Next, the switching valve 3 is switched, and the carrier (water) 6 is driven by the pump 5.
Is sucked in and the sample solution in the sample loop 4 is pushed out to the mixer 7.

A reaction liquid (mixed liquid of ammonium molybdate and boric acid) 9 is sent to the mixer 7 by a pump 8. The deaerator 10 deaerates the bubbles due to the gas component dissolved in the carrier 6 and the reaction solution 9. The sample solution mixed with the reaction solution 9 by the mixer 7 is heated in the oven 11 to react, and the reaction result is measured by the detector 12 for absorbance.

While the pump 1 is sampling the sampling liquid 2 in the sampling loop 4, the pump 5 and the mixer 7
Are not communicated with each other. During analysis, the switching valve 3 is switched so that the pump 5, the sampling loop 4 and the mixer 7 are in communication with each other, and the sample in the sampling loop 4 is pushed out to the mixer 7 by the carrier 6. ..

The oven 11 heats the sample solution mixed with the reaction solution 9 to about 80 ° C. to accelerate the reaction, and the detector 12
Measures the absorbance of the reaction solution at a wavelength of 400 nm, for example. The data processor 13 displays the absorbance value on the calibration curve of the standard sample so that the Si concentration can be easily seen.

FIG. 2 is a block diagram of the Si concentration monitoring device. The equipment required for measurement is stored together in a dedicated rack with casters so that it can be easily moved depending on the measurement location. The apparatus of FIG. 2 has an analysis unit 20 (FIA
Part), the detection part 21, and the chemical liquid supply part 2 for supplying the liquid.
2. The data processing unit 23 for processing data is configured. It should be noted that the pumps 1, 5 and 8, the switching valve 3, the sample loop 4, the oven 11 and the like may be commercially available products according to the purpose, and for example, a flow injection device (FIA) that conveniently includes these may be used. ..

FIG. 3 shows the S obtained by the apparatus of the present invention.
It is an example of the result of i concentration measurement. 200 μl of the treatment liquid 2 containing HF as a main component is sampled every 2 minutes, and the carrier (pure water) 6 is mixed at a ratio of 1:99 (HF: pure water) to the reaction liquid (for atomic absorption). Si standard reagent) 9
Was mixed at about 0.8 ppm and measured. In FIG.
For about 20 minutes after the apparatus was started up, the oven 11 was not stable, and the Si concentration decreased, but the measured value variation for 4 hours thereafter was within 2%.

As described above, the apparatus of the present invention can stably measure the Si concentration of the sampling liquid in real time and the consumption of the sampling liquid is extremely small, so that the sampling liquid 2 can be continuously supplied without being replenished. It turns out that real-time measurement is possible.

In FIG. 4, the wafer is dipped in the processing liquid 2 and S
FIG. 6 is a diagram showing a relationship between the number of wafers processed and the Si concentration in the processing liquid 2 when the i oxide film is etched. The solid line shows the Si concentration when the liquid in the treatment tank is circulated while being filtered by the filter, and the dotted line shows the Si concentration when the liquid is not circulated and filtered. If the circulating filtration is not performed, the Si concentration increases linearly in proportion to the number of wafers processed, and if the circulating filtration is performed, the degree of increase in the Si concentration decreases. For example, colloidal Si
It can be seen that the Si concentration saturates as the components are filtered out. That is, when the treatment liquid 2 is circulated and filtered, the Si component in the treatment liquid can be suppressed to a certain value or less.

FIG. 5 shows data obtained by measuring the change in the etch rate depending on the number of processed wafers in the same manner. If circulation filtration is not performed (dotted line), the number of processed wafers is 60 to 80.
As the number of sheets approaches, the etch rate decreases sharply and linearly increases and the treatment solution cannot be used. On the other hand, if circulation filtration is performed, the treatment solution 2 can be used for a long time. As described above, in the present invention, as shown in FIG. 6, the processing liquid in the processing tank 241 is circulated through the filter 243 by the pump 242.

FIG. 6 is a block diagram of a Si concentration monitoring device including an automatic management system of a processing liquid according to the present invention. The processing liquid that has flowed over from the processing tank 241 is sent to the filter 243 by the pump 242 via the buffer tank 244 and returned to the processing tank 241. The monitor unit 25 is the processing tank 2
The Si concentration of the treatment liquid in 41 is monitored, and when the Si concentration exceeds a preset value, a signal is sent to the chemical liquid supply unit 27. In response to the above signal, the control unit 271 in the chemical liquid supply unit 27 controls 50% of the predetermined amount taken from the HF tank 272 to the measuring tank 273.
The HF liquid is sent to the mixing layer 274, and at the same time, a fixed amount of pure water is sent to the mixing layer 274, and the liquid level is constantly maintained by the liquid level gauge 275 to supply a new liquid to the processing tank 241.

By circulating filtration of the treatment liquid through the treatment tank 241 and the buffer tank 244, the new liquid to be replenished in the mixing layer 274 is mixed well, so that the effects shown in FIGS. Further, the monitor unit 25 is a processing tank 241.
When the Si concentration therein exceeds a predetermined value, a signal is sent to the alarm unit 26 to notify the operator of the abnormality. In addition, the processing liquid that has reached the end of its life should be automatically drained.

FIG. 7 shows Si measured by the apparatus shown in FIG.
The data is shown by comparing the concentration (dotted line) with the calculated value (solid line). Since the dotted line and the solid line almost exactly coincide with each other, it can be seen that the device of FIG. 6 operates according to theory. In addition, FIG. 7 shows the measurement after stopping the replenishment of a new processing solution,
Also, the calculated value is Si which is removed by etching from the wafer surface.
It is calculated from the amount of O ₂ film.

FIG. 8 is a block diagram of an embodiment of a Si concentration measuring device according to the present invention capable of measuring a minute amount of Si of 1 ppm or less. In FIG. 8, the sample reacted with the heteropoly compound in the reaction solution 9 of FIG.
-A mixture of hydroxynaphthalene sulfonic acid and sodium sulfite) 15 is used for reduction, and the Si concentration is measured at the ppb level by the molybdenum bull method. The reduction reaction treatment method is the same as the molybdenum bull method of JIS K-0101-1986.

That is, the mixer 14 is provided after the reaction coil in the oven 11, and the reaction liquid 15 is supplied by the pump 16.
Is supplied to react with the reaction coil 17, and the absorbance is measured by the detector 12 by the molybdenum yellow method. In the apparatus of FIG. 1, the measurement wavelength at this time was 400 nm, but in this case, a wavelength around 700 nm is preferable.

FIG. 9 shows Si measured by the apparatus shown in FIG.
It is the data showing the concentration (dotted line) in comparison with the calculated value (solid line). Since the dotted line and the solid line almost exactly coincide with each other, it can be seen that the apparatus of FIG. 8 operates according to the theory. It should be noted that FIG. 9 is measured manually after stopping the replenishment of a new processing liquid, and the calculated value is calculated from the amount of the SiO ₂ film etched and removed from the wafer surface.

10 and 11 are block diagrams of an embodiment of the Si concentration measuring apparatus of the present invention for measuring the Si concentration in pure water by the molybdenum bull method. The Si concentration in pure water is a problem, for example, in a pure water production system or the same monitoring system. Si
Since pure water containing water is not acidic like HF chemicals, ammonium molybdate does not react with Si. Also, the reaction liquid 9
If an acid for pH adjustment is added to the mixture, perhydrolysis is likely to occur. Therefore, it is preferable to mix it with the reaction solution as shown in FIG. That is, as in FIG. 1, the reaction liquid 9 and the sample are mixed in the mixer 7 and the reaction liquid (hydrochloric acid or sulfuric acid) 18 is mixed by the pump 19 at the same time.

FIG. 11 shows a case where the reaction solution 15 is added as in FIG. 7 corresponding to the case where Si in the pure water has a low concentration. In each of the above-described embodiments of the present invention, it is possible to specify a manual mode in which point measurement is performed for each process and an auto mode in which continuous measurement is automatically performed by switching the mode switch. You can

[0030]

In the molybdenum yellow method, the first reaction solution (ammonium molybdate and boric acid) was previously mixed with the semiconductor etching solution (HF) in advance, so that ammonium molybdate was decomposed by perhydration for a long time. Where it could not be used, in the present invention, since the etching treatment liquid and the first reaction liquid are mixed immediately before the reaction oven, the first reaction liquid can be continuously used for a long time.

Further, since the etching treatment liquid, the diluting water, the reaction liquid and the like can be accurately measured and mixed by the pump and the sampling valve, the Si content of the etching treatment liquid is, for example, a repeatability of 2% or less and a detection limit of 0. It can measure with an accuracy of 1ppm, and the measurement time for one sample is 30
Since the time can be shortened from -40 minutes to less than 1 minute, the measurement can be automatically performed in real time with high accuracy, and the etching rate can be managed.

Further, since the sampling amount per sample, which is 10 ml or more in the above-mentioned conventional apparatus, can be reduced to 0.2 ml or less, the consumption of the etching treatment liquid can be reduced to 1/50 or less. Further, by automating the above-mentioned measurement, the worker does not have to directly operate a dangerous chemical such as an etching treatment liquid containing HF as a main component, so that the safety of the work is improved and at the same time, the unmanned continuous measurement becomes possible. Become. In the case of the molybdenum blue method, by adding one type of reaction solution, the Si content can be automatically measured in real time at a detection limit of 1 ppm in the same manner.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for measuring Si concentration in an HF treatment liquid according to the present invention.

FIG. 2 is a configuration diagram of a Si concentration monitoring device according to the present invention.

FIG. 3 is measurement data of Si concentration in the device of the present invention.

FIG. 4 is measurement data of Si concentration in the device of the present invention.

FIG. 5 is wafer etch rate measurement data in the apparatus of the present invention.

FIG. 6 is a block diagram of an Si concentration automatic management system according to the present invention.

FIG. 7 is data showing the Si concentration measured by the device of the present invention in comparison with the calculated value.

FIG. 8 is a block diagram of a low concentration Si concentration monitoring device according to the present invention.

FIG. 9 is data showing the Si concentration measured by the device of the present invention in comparison with the calculated value.

FIG. 10 is a block diagram of an apparatus for monitoring Si concentration in pure water according to the present invention.

FIG. 11 is a block diagram of an apparatus for monitoring Si concentration in pure water according to the present invention.

[Explanation of symbols]

1 ... Pump, 2 ... Processing liquid, 3 ... Switching valve, 4 ... Sample loop, 6 ... Carrier, 7 ... Mixer, 9 ... Reaction liquid,
10 ... Deaeration device, 11 ... Oven, 12 ... Detector, 13
... data display device, 14 ... mixer, 15 ... reaction liquid, 17
... Reaction coil, 18 ... Reaction solution, 20 ... Analytical section, 21 ...
Detection unit, 22 ... Chemical solution supply unit, 23 ... Data processing unit, 24
... Processing unit, 25 ... Monitor unit, 26 ... Alarm device, 27 ... Chemical solution supply unit, 241 ... Processing tank, 243 ... Filter, 244 ...
Buffer tank, 271 ... Control unit, 272 ... HF tank, 273
... measuring tank, 274 ... mixing tank, 275 ... liquid level gauge.

Front page continuation (72) Inventor Masahiro Watanabe 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Pref., Hitachi, Ltd.

Claims (9)

[Claims] 1. S in a chemical solution for measuring absorbance by developing color of Si dissolved in a processing solution in a semiconductor manufacturing process or the like.
In the i-concentration monitoring device, a sampling means for alternately sampling and sending a predetermined amount of the treatment liquid and a carrier (pure water), and a first reaction liquid for mixing the first reaction liquid with the sample liquid output by the sampling means. Si concentration in the chemical liquid, comprising: mixing means, means for heating the mixed solution output by the first mixing means, and absorbance measuring means for measuring the color development of the mixed solution output by the heating means. Monitor device. 2. The apparatus for monitoring the Si concentration in a chemical solution according to claim 1, wherein the heating temperature of the mixed solution by the heating means is set to 80 ° C. or lower. 3. The apparatus for monitoring the Si concentration in a chemical solution according to claim 1, wherein the first reaction solution is a mixed solution of ammonium molybdate and boric acid. 4. The method according to any one of claims 1 to 3,
A monitor unit for monitoring the Si concentration in the treatment liquid, means for replenishing the treatment liquid with a new treatment liquid according to an output signal from the monitor unit, and means for circulating and mixing the treatment liquid are provided. A characteristic Si concentration monitoring device in a chemical solution. 5. The mixing tank according to claim 4, which stores the new processing liquid containing a predetermined amount of HF liquid and pure water, and the new processing liquid in the mixing tank is processed according to the output signal of the monitor unit. An apparatus for monitoring the Si concentration in a chemical solution, comprising: a control means for replenishing a treatment tank containing a liquid and / or a buffer tank; and a means for circulatingly mixing the treatment solution through the treatment tank and the buffer tank. .. 6. The tank according to claim 4 or 5, which contains at least the processing liquid, each replenishing liquid, a carrier, a reaction liquid, a waste liquid, and the like, a sampling unit, a first mixing unit, a heating unit, and a processing liquid. An apparatus for monitoring the Si concentration in a chemical solution, characterized in that the replenishment, circulating mixing means, etc. are integrally housed in a rack with casters. 7. The method according to any one of claims 1 to 6,
A second mixing means for mixing the second reaction solution with the mixed solution output by the first mixing means, and a means for heating the output of the second mixing means are provided. Si concentration monitor. 8. The apparatus for monitoring the Si concentration in a chemical solution according to claim 7, wherein the second reaction solution is a mixed solution of 4-amino-3-hydroxynaphthalenesulfonic acid and sodium sulfite. 9. The method according to claim 1, wherein
The first reaction solution mixed by the first mixing means is produced by mixing the mixed solution of ammonium molybdate and boric acid with hydrochloric acid or sulfuric acid immediately before the first mixing means. A characteristic Si concentration monitoring device in a chemical solution.