JPH10239241A - Measuring apparatus for etched amount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus by which an etched amount can be measured with high sensitivity even in a low-amount etching operation by a method wherein dissolved silicon is reacted with a supplied chemical, the concentration of the silicon is measured on the basis of the absorbance of an extracted chemical liquid and the etched amount is computed and found on the basis of the concentration. SOLUTION: A silicon substrate 29 is fixed by a holding implement 2, and a surface thin film 29 is exposed. Then, a definite quantity of a chemical liquid in which hydrogen peroxide is mixed with ammonia is poured into a closed space at the holding implement 2. After a prescribed time has elapsed, the chemical liquid 3 in which silicon is dissolved is sent to a reaction tank 4 by a pump 16. The pH value of the chemical liquid 3 is maintained at a constant value when a sulfuric acid solution 12 is supplied. After that, an ammonia molybdate solution 11, the sulfuric acid solution 12 and an L-ascorbic acid solution 10 in proper quantities are supplied to the reaction tank 4 by respective pumps 13 to 15, and they react with the chemical liquid 3 so as to generate a blue color. The discolored chemical liquids are extracted by a pump 17, and the absorbance of light is measured by an absorptiometer 5. Its absorbance signal is input to a control part 6 so as to be computed, and the etched amount of the silicon substrate is computed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the amount of etching of a silicon substrate or a silicon thin film using a chemical, and more particularly to an apparatus for measuring the amount of etching based on the concentration of components etched by the chemical.

[0002]

2. Description of the Related Art Heretofore, the evaluation of the etching amount of a silicon substrate or a thin film on a surface by a chemical solution has been performed by measuring a change in the film thickness of the thin film before and after the etching step using a film thickness measuring device.

FIG. 6 shows an example of a conventional film thickness measuring apparatus. As this film thickness measuring device, for example, an ellipsometer as shown in FIG. 6 has been used. In order to measure the thickness of the thin film 28 of the silicon substrate 29 with this ellipsometer, the laser light from the laser projector 24 is linearly polarized by the polarizer 25, enters the thin film 28, and is reflected by the elliptically polarized light reflected from the thin film 28. The photodetector 2 passes through an analyzer 26 that rotates
At 7, the light intensity is measured. Then, the phase difference and the azimuth angle are obtained from the relationship between the rotation angle of the analyzer 26 and the light intensity of the photodetector 27, and the thickness of the thin film 28 is obtained based on the relationship between the phase difference and the azimuth angle.

However, the ellipsometer has a film thickness measurement range limited to 100 angstroms or more, and its measurement accuracy is as low as ± 10 angstroms. For this reason,
In the case of etching with a small change in film thickness, it is difficult to measure the amount of etching. Another problem is that the etching amount of the silicon substrate itself cannot be measured. In addition to such a film thickness measuring device, there is a film thickness measuring device utilizing optical interference, but all have the same problems as the above-described film thickness measuring device.

In addition to the method of measuring the amount of etching by measuring the film thickness by physical analysis using light, there is a method of chemical analysis that calculates the amount of etching from the component concentration of a thin film dissolved in a chemical solution. For example, JP-A-63-226
As disclosed in Japanese Patent No. 932, a change in the concentration of a material to be etched (GaAs) dissolved in a chemical solution is monitored by emission analysis, and the end time of etching is determined based on the concentration of the material to be etched. Also, Japanese Patent Laid-Open No.
No. 46402 discloses that the concentration of silicon in a chemical solution (HF) is monitored to replenish a new chemical solution and keep the etching rate of the chemical solution constant.

[0006]

The above-mentioned method utilizing the chemical analysis is originally intended for the management of a chemical solution, and has a problem that the lower limit of detection of a dissolved component is high. For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 5-346402, the detection limit of the silicon concentration in a chemical solution is 0.1 pp.
m. For this reason, when the etching amount of the silicon substrate or the thin film containing silicon is small, the concentration of silicon dissolved in the chemical solution also becomes low, and the measurement becomes difficult.

In addition, when the chemical solution contains aqueous hydrogen peroxide, the color development is hindered and accurate measurement cannot be performed. This method has a drawback that it is limited to a chemical solution that does not contain aqueous hydrogen peroxide. . In addition, this hydrogen peroxide solution is a foaming chemical solution, and there is a problem in that the generation of bubbles hinders pumping and absorption measurement.

Accordingly, an object of the present invention is to provide an etching amount measuring apparatus capable of measuring the etching amount of a silicon substrate or a thin film containing silicon with high sensitivity in a wide range in which even a small etching amount can be measured.

[0009]

A feature of the present invention is an etching amount measuring apparatus for measuring an etching amount of a silicon substrate or a thin film containing silicon formed on a substrate surface by chemical treatment in a semiconductor manufacturing process. A processing unit including a wafer holder for holding the silicon substrate so as to be able to come into contact with a chemical solution on the substrate surface or the silicon thin film surface and storing the chemical solution, and a heating unit for heating the wafer holder, and the silicon substrate or the thin film Sampling means for collecting a chemical solution containing silicon that is in contact with and dissolved in the surface, supply means for supplying a chemical that reacts with the dissolved silicon to form a color, and the chemical solution sent from the sampling means, A reaction tank for mixing and reacting the medicine supplied from the supply means, and coloring after the reaction. And the absorbance meter for measuring the absorbance of the coloring of the drug solution, an etching amount measuring device and a control unit for calculating the amount of etching from the absorbance of the chemical.

[0010] It is preferable that the apparatus further comprises a degassing device for removing gas components contained in the chemical solution supplied from the processing section to the reaction tank. Further, the liquid medicine contains hydrogen peroxide, and the sampling means has a first heater for heating a part of the liquid supply pipe while the inner wall of a part of the liquid supply pipe of the chemical liquid is made of platinum, Alternatively, the inner wall of the reaction vessel is made of platinum and a second solution for heating the chemical solution in the reaction vessel is used.
It is desirable to provide the heater of the above.

[0011]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an etching amount measuring apparatus according to an embodiment of the present invention. The etching amount measuring apparatus of the present invention focuses on the molybdenum blue method (JIS-K0555 “Quantitative method for ultrapure water silica” 1990), which is a method for quantifying silicon in a processing solution. The molybdenum blue method is a method in which a heteropoly compound formed by the reaction between silicon and ammonium molybdate is reduced with L-ascorbic acid and the silicon concentration is determined from the blue absorbance.

As shown in FIG. 1, an etching amount measuring apparatus to which the silicon concentration quantification method is applied is a chemical solution containing a hydrogen peroxide solution which is brought into contact with the surface of a silicon substrate 29 or a thin film 28 on the silicon substrate 29. A processing unit 1 comprising a holder 2 for holding a certain amount and holding a silicon substrate 29 and a heater 9 for heating the silicon substrate 29;
A degassing module 8 for removing gas components in the chemical solution 3 in the holder 2 sucked up by the pump 16, a chemical solution 3 extracted from the pump 16, a sulfuric acid solution 12 supplied by a pump 15, and supplied by a pump 14. A reaction tank 4 in which the ammonium molybdate solution 11 and the L-ascorbic acid solution supplied by the pump 13 are mixed and reacted.
An absorbance meter 5 for measuring the absorbance of the chemical solution 3 which is colored by the reaction in the reaction tank 4 and extracted by the pump 17, and a PH for measuring the PH in the solution of the reaction tank 4 which is kept constant by the supply of the sulfuric acid solution 12. And a control unit 6 for controlling the currents of the pumps 13 to 17 and the heater 9 and inputting and calculating the signal value of the absorbance meter 5 to obtain the etching amount of the surface of the silicon substrate or the thin film 28.

The pH value of the chemical solution 3 sent to the reaction tank 4 is measured by a pH meter 7, and the obtained pH value is sent to the control unit 6. The sulfuric acid solution 12
Is sent to the reaction tank 4 by the pump 15, and the chemical solution 3 has a low pH.
Is maintained at a constant value. Next, after the ammonium molybdate solution 11 is sent by the pump 14, the sulfuric acid solution 12
And L-ascorbic acid solution 10 are supplied by pumps 15 and 13.

The chemical solution 3 which has been changed to blue in the reaction tank 4 by the respective liquids is extracted by the pump 17, passes through a transparent quartz tube, and the optical absorbance of the chemical solution 3 is measured by the absorbance meter 5, and the absorption is measured. The degree is output as a signal. The control unit 6 receives the absorbance signal, obtains the known absorption coefficient and absorbance, obtains the silicon concentration in the chemical solution, and calculates the etching amount of the thin film 28 of the silicon substrate 29.

Next, the operation of the etching amount measuring apparatus will be described. First, the silicon substrate 29 is sandwiched and fixed by the holder 2, and the silicon substrate 29 is held such that the thin film 28 on the surface is exposed in the opening of the lid. Next, a certain amount of the chemical solution 3 containing hydrogen peroxide in ammonia is injected into the closed space of the closed holder 2. Then, bubbles generated from the chemical solution 3 that comes into contact with the thin film 28 of the silicon substrate 29 heated by the heater 9 are exhausted to the outside of the liquid feeding pipe by the degassing module 8. After the elapse of the predetermined time, when the generation of air bubbles is stopped, the inside of the liquid sending pipe is depressurized, and the chemical solution 3 in which silicon is melted by the pump 16 is sent to the reaction tank 4. After the pH value of the chemical solution 3 is maintained at a low constant value by the supply of the sulfuric acid solution 12, at appropriate intervals, pumps 13 to 15 supply appropriate amounts of the ammonium molybdate solution 11, the sulfuric acid solution 12 and the L-ascorbic acid solution 1.
0 is supplied to the reaction tank 4 and mixed with the chemical solution 3.

The chemical solution supplied to the reaction tank 4 reacts in the tank and generates a blue color by this reaction. The blue-colored drug solution is extracted by the pump 17 and the absorbance of the light is measured by the absorbance meter 5. The measured absorbance signal is input to the control unit 6 for calculation, and the microcomputer of the control unit 6 calculates the silicon etching amount as described above.

FIG. 2 is a view showing a modification of the etching amount measuring apparatus of FIG. This etching amount measuring apparatus is shown in FIG.
As shown in FIG. 5, in order to remove the hydrogen peroxide solution which inhibits color development, a closed space for storing the chemical solution 3 of the holder 2 and the reaction tank 4 are provided.
The platinum tube 18 and the heater 9a are provided in the middle of the liquid supply pipe route. The platinum tube 18 may be made of platinum alone, but it is desirable to coat the inner wall of the liquid sending tube with platinum in order to reduce the cost.
Otherwise, the configuration is the same as that of the etching amount measuring apparatus in the above-described embodiment.

The platinum tube 18 acts as a catalyst, and the chemical solution passing through the platinum tube 18 is heated by the heater 9a to promote decomposition, and the hydrogen peroxide solution in the chemical solution passing through the liquid feed pipe is removed. Further, the removed hydrogen peroxide solution is exhausted by the degassing module 8. In order to perform the exhausting more effectively, a pump for degassing is provided in the platinum tube 18 separately from the degassing module 8. It is desirable to improve the exhaust. The heater 9a is a platinum tube 1
8 is provided so as to surround the periphery of 8, and heats the chemical solution to be sent efficiently to promote the removal of the hydrogen peroxide solution.

FIG. 3 is a graph showing the etching amount of a thin film on a silicon substrate by the etching amount measuring apparatus of FIG. In order to confirm the advantages of the etching amount measuring apparatus of FIG. 2, a silicon wafer with an oxide film and a mixed solution of ammonia and hydrogen peroxide were used. Then, a case where hydrogen peroxide was decomposed and a case where hydrogen peroxide was not decomposed were tried respectively.

As a result, as shown in FIG. 3, when hydrogen peroxide was decomposed, the etching amount of the oxide film increased in proportion to the immersion time of the silicon wafer. On the other hand, when the hydrogen peroxide was not decomposed, the etching amount of the oxide film showed a low value due to the hindrance of color development by the hydrogen peroxide, and the variation became large due to bubbles. From this, it was found that reproducible data can be obtained by decomposing hydrogen peroxide with a platinum tube.

FIG. 4 is a graph showing the etching amount of an oxide film by a mixed solution of ammonia and hydrogen peroxide in the etching amount measuring apparatus of FIG. As shown in FIG. 4, the etching amount of the oxide film by the etching amount measuring device of FIG. 2 showed a good linearity with respect to the immersion time even in a measurement region where the immersion time was short (low etching amount). On the other hand, in the conventional method (using an ellipsometer), the etching amount tended to decrease in the measurement region where the immersion time was short (low etching amount). This shows that the etching amount measuring apparatus according to the embodiment of the present invention can measure with high accuracy even a low etching amount that cannot be measured by the conventional method. It was also found that the lower limit of detection of the amount of etching of the oxide film by the present apparatus was 1 angstrom and the measurement accuracy was ± 2%.

FIG. 5 is a view showing another modification of the etching amount measuring apparatus of FIG. This etching amount measuring device
As shown in FIG. 5, the inner wall of the reaction tank 4 is coated with platinum to form a platinum wall 20, and a heater 19 is provided around the reaction tank 4 to heat the platinum wall 20. Other than that, it is the same as the etching amount measuring apparatus shown in FIG. By making the inner wall of the reaction tank 4 a platinum wall 20, hydrogen peroxide contained in the chemical solution 3 sent from the processing section 1 becomes
It is heated and decomposed by the platinum wall 20. As described above, the absorbance of light of the blue color of the chemical solution 3 is measured by the absorbance meter 5. The measured absorbance signal is input to the control unit 6 and calculated,
The microcomputer of the control unit 6 estimates a silicon etching amount. This etching amount measuring apparatus has an advantage that the contact between the chemical solution and platinum is greater and the decomposition of hydrogen peroxide is promoted as compared with the above-mentioned platinum tube.

[0024]

As described above, the present invention provides a processing section having a heating means capable of contacting silicon or silicon thin film silicon to promote dissolution and having a container for storing a small amount of a chemical, and a processing section comprising: A reaction vessel that reacts the dissolved silicon with the supplied drug to produce a blue color, an absorbance meter that measures the silicon concentration with high sensitivity based on the absorbance of the drug solution extracted from the reaction vessel, and a calculation based on the silicon concentration from the absorbance meter. By providing a control unit having a calculation unit for calculating the amount etched from the silicon thin film, the etching amount can be measured with high sensitivity even with a small amount of etching. There is an effect that it can be controlled.

Further, by providing a means for removing air bubbles which hinder the sending of the chemical solution from the processing section to the reaction tank,
There is an effect that the sending of the chemical solution is smooth and the measurement can be stably performed. Further, by providing a means for decomposing hydrogen peroxide which hinders color formation, there is an effect that measurement accuracy can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an etching amount measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a modification of the etching amount measuring device of FIG. 1;

3 is a graph showing an etching amount of a thin film on a silicon substrate by the etching amount measuring device of FIG. 2;

4 is a graph of an etching amount of an oxide film by a mixed solution of ammonia and hydrogen peroxide in the etching amount measuring device of FIG. 2;

FIG. 5 is a view showing another modification of the etching amount measuring apparatus of FIG. 1;

FIG. 6 is a diagram showing an example of a conventional film thickness measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing part 2 Holder 3 Chemical solution 4 Reaction tank 5 Absorbance meter 6 Control part 7 PH meter 8 Deaeration module 9.9a, 19 Heater 10 L-ascorbic acid solution 11 Ammonium molybdate solution 12 Sulfuric acid solution 13, 14, 15, 16, 17 Pump 18 Platinum tube 20 Platinum wall 24 Laser projector 25 Polarizer 26 Analyzer 27 Photodetector 28 Thin film 29 Silicon substrate

Claims (4)

[Claims] 1. An etching amount measuring device for measuring an etching amount of a silicon substrate or a thin film containing silicon formed on a surface of a substrate by a chemical solution treatment in a semiconductor manufacturing process, wherein a chemical solution is applied to the silicon substrate surface or the silicon thin film surface. A processing unit including a wafer holder for holding the silicon substrate so as to be able to contact and storing the chemical solution, and a heating unit for heating the wafer holder; and a silicon dissolving in contact with the surface of the silicon substrate or the thin film. Sampling means for collecting a chemical solution containing, a supply means for supplying a chemical that reacts with the dissolved silicon to form a color, and the chemical liquid sent from the sampling means and the chemical supplied from the supply means. A reaction tank for mixing and reacting, and the absorbance of the color of the chemical solution that has developed after the reaction, An etching amount measuring device comprising: an absorbance meter for measuring; and a control unit for calculating the etching amount from the absorbance of the chemical solution. 2. The etching amount measuring apparatus according to claim 1, further comprising a deaerator for removing a gas component contained in the chemical solution supplied from the processing section to the reaction tank. 3. A first heater which contains hydrogen peroxide in said chemical solution, has a part of an inner wall of a pipe for sending said chemical liquid of said sampling means made of platinum, and heats a part of said liquid feed pipe. The etching amount measuring apparatus according to claim 1, further comprising: 4. The etching amount according to claim 1, wherein the inner wall of the reaction vessel is made of platinum, and the reaction vessel is provided with a second heater for heating the chemical solution according to claim 3. measuring device.