JPS628040A - Washing apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform not only the monitoring of the concns. of hydrogen peroxide and ammonia in a washing solution but also the automatic supply of both chemicals, by performing the control of the concns. of chemicals in the washing solution with good controllability. CONSTITUTION:A washing tank 1 is filled with a washing solution consisting of hydrogen peroxide, ammonia and water and heated by a heater 3 to perform the washing of a Si-wafer 4. A part of the washing solution 2 is sampled by a specimen sampling pump 5 to be sent into the flow cell 7 of an oxygen concn. measuring part 6. Next, the concn. of oxygen in the flow cell 7 is photometrically measured by an ultraviolet ray source 8 and an ultraviolet detector 9 detecting the transmitted light thereof. Subsequently, the sampled specimen of the washing solution measured by the flow cell 7 is sent into the conductivity detection part 12 of an ammonium ion concn. measuring part 11 by a specimen sampling pump 10 and measured by an operation part 13. The measured data is sent to an interface 14 along with the data measured by the measuring part 6 and the concns. of hydrogen peroxide and ammonia are calculated from two measured values by a microcomputer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cleaning apparatus that uses a cleaning liquid consisting of hydrogen peroxide, ammonia, and water for cleaning Si wafers, etc. The present invention relates to a cleaning device that has a component concentration monitor of the cleaning fluid to maintain the cleaning fluid and has a function of controlling the component concentration of the cleaning fluid to an appropriate value in accordance with the monitor.

[Background of the invention]

Conventionally, cleaning solutions for S1 sea urchins and the like that use hydrogen peroxide, ammonia, and water are often heated to about 80°C, so the hydrogen peroxide can be decomposed in just a few minutes due to thermal decomposition. Evaporation of ammonia causes deterioration of the cleaning solution. Conventionally, these components have been confirmed using off-line and time-consuming component analysis methods such as titration analysis, or using ion electrodes to measure ammonia concentration and ultraviolet light to measure hydrogen peroxide concentration. A technique for measuring in combination with a method using absorption (for example, Japanese Patent Application Laid-Open No. 59-4603
Publication No. 2) is used.

However, methods that use ion electrodes to measure ammonia concentration utilize a chemical reaction between the ammonia gas that passes through the diaphragm and the internal liquid of the electrode, so the life of the electrode is short, there are problems with maintainability, and the response is There was a problem in that the concentration of the chemical solution in the cleaning solution could not be controlled with good controllability because of its poor performance.

Another known example is a method of emitting light using a reagent and measuring the absorbance (Japanese Utility Model Application Publication No. 57-41742). However, this method uses sodium phenolate solution and sodium hypochlorite solution as reagents, and these have the risk of causing sodium contamination, which requires the utmost care in semiconductor processes, so they cannot be used in production lines. It's inappropriate.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a method for monitoring hydrogen peroxide concentration and ammonia concentration in a cleaning solution for S1 wafers, etc., which is made of hydrogen peroxide, ammonia, and water and can be measured in-line. , and a cleaning device having an automatic supply means for these chemicals.

[Summary of the invention]

The present invention measures the amount of ultraviolet light absorbed by oxygen in a sample liquid collected from a cleaning tank (first measurement part), and measures the conductivity based on the amount of ammonium ions in the sample liquid (second measurement part).
(measuring unit) Calculates the hydrogen peroxide concentration and ammonia concentration in the sample solution based on the measurement results of the measuring unit, compares the concentration with the set concentration, and based on the results, calculates the concentration of hydrogen peroxide and ammonia in the sample solution. This system automatically replenishes water to maintain the concentration of chemical components in the cleaning solution within a certain range, allowing stable cleaning of Si wafers and the like.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention.

Here, the basic principle of the concentration measurement method used in the present invention will be explained in detail below.

When oxygen is dissolved in an aqueous solution, a very characteristic absorption band appears in the ultraviolet region. FIG. 2 is a diagram showing changes in the absorbance of oxygen and ammonia with respect to ultraviolet wavelengths due to hydrogen peroxide. In FIG. 2, curve A is a curve showing the absorbance of oxygen only by hydrogen peroxide, and curve B is a curve showing the absorbance of only ammonia. As can be seen from the graph in Figure 2, oxygen and ammonia due to hydrogen peroxide are
Both have an absorption peak in the ultraviolet region around a wavelength of 19 Jnm, and it is difficult to distinguish between the two near the peak. However, the absorption spectrum of oxygen caused by hydrogen peroxide is broad, and the absorption spectrum of ammonia is almost zero at wavelength 30.
Even around 0 nm, it still exhibits a slight absorption. Therefore, by measuring the absorbance at a wavelength of around 500 nm, it is possible to separate the absorption of oxygen by hydrogen peroxide from the absorption by ammonia in the collected sample of the cleaning liquid in which ammonia, hydrogen peroxide, and water coexist.

The oxygen concentration of the above aqueous solution is influenced by the hydrogen ion concentration of the solution. However, when the hydrogen ion concentration of the aqueous solution is set to 4 or less, the absorbance (Ab) at a wavelength of around 300 nm provides an absorbance that is unrelated to the ammonia concentration. Therefore, the following equation holds.

H2O2 (%) = a XAb ” =...
11) However, a is a constant.

In addition, Figure 3 shows the absorbance ratio (Aa/Ab
) and the logarithm of the ammonia concentration in the solution. As shown in the figure, there is a proportional relationship between the logarithm of the ammonia concentration and the absorbance ratio (Ac/Ab) near a wavelength of 300 nm. That is, 1ogNH4oHc%)=bxAc/hb --
-----・-(2) Substituting equation (1) into equation (2) yields the following.

1ogNH40H(1) =l) x AQ/-x)I
2o2 (%) = cxAQ/H2O2 (*) −・−
...(3) However, C is a constant (c=ab).

Figure 4 is a graph showing the relationship between ammonia concentration and electrical conductivity. Curve P is for an ammonia aqueous solution containing no hydrogen peroxide, and curves F and F are for a case where hydrogen peroxide coexists. , F' are cases where the hydrogen peroxide concentration is higher than F. As can be seen from the graph in FIG. 4, if the hydrogen peroxide concentration is constant, the electrical conductivity increases as the ammonia concentration in the sample liquid increases. In other words, when ammonia and hydrogen peroxide coexist, a buffering effect works in the aqueous solution, and ammonium ions dissociate in proportion to the hydrogen peroxide concentration, increasing the amount of ammonium ions in the aqueous solution and increasing the conductivity. be.

Figure 5 shows the ratio (X/X') of the conductivity X when hydrogen peroxide coexists in the sample of the cleaning solution and the conductivity X' when no hydrogen peroxide coexists. It is a graph showing the relationship with hydrogen concentration.

As can be seen from the graph in FIG. 5, the hydrogen peroxide concentration in the sample of the cleaning liquid can be calculated by calculating X/X. That is, H202 (%) == a −X, /X' −o
...--(4) However, d and e are constants.

Also, the conductivity of the solution when hydrogen peroxide is not present
is in a linear relationship as shown by curve E in FIG.

log N H40H (chi) = f-X + g ・
・・・・・・・・・(5) However, f and g are constants.

Therefore, by substituting equation (5) into equation (4), as described above, the absorbance (Ao) and conductivity (X) in the vicinity of a wavelength of 300 nm in the solution are measured.

By substituting this into equations (3) and (6) and solving the simultaneous equations, the concentrations of hydrogen peroxide and ammonia in the solution can be determined.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 6 to 8.

In this example, the above-mentioned method for measuring the concentration of hydrogen peroxide and ammonia is applied, and a microcomputer is used to adjust the concentration of each component of the cleaning liquid to a predetermined concentration. It is configured to control IJ.

FIG. 6 is a system diagram showing an example of a cleaning device for S1 cleaning according to the present invention. In the figure, cleaning tank 1
For cleaning solution 2 consisting of hydrogen peroxide, ammonia and water.
5. is filled and heated by heater 3. Si ueno・
4 cleaning is being carried out. A part of the cleaning liquid 2 is sampled by the sampling pump 5 and sent to the flow cell between the oxygen concentration measurement units. Absorption is measured using an ultraviolet light source 8 with a wavelength of around 500 nm and an ultraviolet detector 9 that detects the transmitted light. 70 - The collected sample of the cleaning liquid whose ultraviolet absorption was measured in the cell 7 is sent to the conductivity detection unit 12 of the diammonium ion concentration measurement unit 11 by the sample collection pump 10.
After the following measurements are taken, the sample is discharged from the discharge port 22. That is, the conductivity depending on the ammonium ion concentration is measured by the conductivity detection section 12 and the operation section 13 of the ammonium ion concentration measurement section 11. The data measured here is sent to the Inter 7Ace 14 together with the data measured by the oxygen concentration measuring section 6. In this manner, the hydrogen peroxide concentration and ammonia concentration are calculated from the two measured values by the microcomputer 20 based on the measurement principle described above.

As described above, the concentrations of ammonia and hydrogen peroxide in the cleaning tank 1 are measured at approximately the same time. Of course, in this case, the sample for oxygen concentration measurement and the sample for conductivity measurement may be collected separately and in parallel. In addition, the discharge port 22
The measured sample discharged from the tank can also be returned to the cleaning tank 1 since no reagent is used in the sample.

The calculated concentration data of hydrogen peroxide and ammonia are compared and referenced with the cleaning liquid concentration set value data stored in the microcomputer 20 in advance. and,
Based on the difference between the concentration setting value and the actual concentration, a command is given to the solenoid valve control section 15 based on a program given in advance to the microcomputer 20, and the solenoid valve 16.1 is
7 opens and closes, and the necessary amounts of hydrogen peroxide and ammonia are supplied to the cleaning tank 1 from the hydrogen peroxide tank 18 and the ammonia water tank 19, respectively, or the pure water supply pump 23 is operated to supply pure water. supply. As a result, the hydrogen peroxide concentration and ammonia concentration of the cleaning liquid 2 can always be kept within a certain range, and the S1 wafer can be cleaned stably.

FIG. 7 is a diagram showing an example of a flowchart of the arithmetic section for the hydrogen peroxide concentration and ammonia concentration. In the embodiment shown in FIG. 6, this arithmetic processing is performed by a microcomputer 2.
Although the case where the calculation is performed with 0 is shown, it is also possible to calculate the concentration using a device that performs another arithmetic processing.

The flowchart in FIG. 7 will be explained. First, start at step KA, set the parameters necessary for calculation (step KB), and then it is determined whether or not to read the instrument output values of the ultraviolet absorbance detector 9 and the conductivity meter operating section 13. (Step K.). If the reading conditions are met, in step, each output value from the ultraviolet absorbance detector 9 and the conductivity meter operating section 13 is read.

When it is determined that reading has been performed a specified number of times in step , the values are averaged in step and sent to the next step as each measured value. Step K. If it is determined whether to import the measured values and the conditions are met, each measured value is stored (step Kg). Next, in step 1, the hydrogen peroxide concentration and ammonia concentration are calculated using each measured value and the above-mentioned relational expressions (3) and (6) K, and one cycle of concentration calculation processing is completed here. (to step).

FIG. 8 is a flow chart of the microcomputer 20. An example of a control method for automatically managing the cleaning liquid concentration to a predetermined concentration according to the present invention will be explained based on this flowchart. First, if you start with step A,
When the pure water pump 23 is turned on (step B), pure water is sent from the pure water tank 24 into the cleaning tank 1. Cleaning tank 1
The water level inside is measured by the liquid level sensor 25 (step C),
It is determined whether the water level in the cleaning tank 1 is at a predetermined value (step D). When the water level reaches a predetermined level, the pure water pump 23 is stopped (step E), the heater 3 is turned on (step F), the cleaning liquid circulation pump 26 is turned on (step G), and then the The solenoid valves 16 and 17 for replenishing hydrogen oxide and ammonia are opened for predetermined times 11 and 12, respectively (step H).

Next, a sample collection pump 5゜10 for liquid sampling.
is turned on (Step E). This is good.

Oxygen concentration measuring section 6, ammonium ion concentration measuring section 11
Step J
), the concentrations of hydrogen peroxide and ammonia are calculated based on the measured values (step K), and it is determined whether the above calculated concentrations are within the target concentration range (step also). If the calculated hydrogen peroxide and ammonia concentrations are outside the target values, or if the concentrations are too low, the solenoid valve 16.17 is opened to release hydrogen peroxide and ammonia at a time t, t2.
is calculated, and if the concentration is too high, a time t5 for sexing the pure water by operating the pure water supply pump 23 for pure water replenishment is calculated (steps M, N), and sexing is performed. (Step Q). In this way, the hydrogen peroxide concentration and ammonia concentration in the cleaning liquid are controlled, and it is determined whether the temperature of the cleaning liquid is within the set range (Step R). If the liquid temperature value measured by the thermometer 28 is within the set value, The Si wafer is cleaned for a certain period of time (step S).

When cleaning is to be continued, the composition and temperature of the cleaning solution are measured again according to the above steps, and then the Si wafer is cleaned (Step J-9). If washing is not to be continued, the liquid is drained and one cycle is completed (steps U and V).

〔Effect of the invention〕

According to the present invention, in-line monitoring with excellent responsiveness of the hydrogen peroxide and ammonia components in the cleaning solution made of hydrogen peroxide, ammonia, and water, which is extremely widely used in the semiconductor industry, is possible. Furthermore, rapid etching of the S1 wafer due to a reduction in hydrogen peroxide can be prevented, and by supplying appropriate amounts of hydrogen peroxide and ammonia, it is possible to regenerate the cleaning solution, extend its life, and stabilize cleaning.

[Brief explanation of drawings]

Figure 1 shows the overall structure of the present invention, and Figure 2 shows the change in absorbance of oxygen and ammonia due to hydrogen peroxide to ultraviolet wavelengths, to explain the principle of measuring oxygen concentration in a solution. Figure 3 is a graph showing the change in ultraviolet absorbance due to a change in hydrogen ion concentration with respect to ammonia concentration in a cleaning solution to explain the principle of measuring hydrogen peroxide concentration, and Figure 4 is a graph showing the relationship between ammonia concentration and conductivity in a cleaning solution. A graph showing the relationship for various hydrogen peroxide contents, Figure 5 shows the ratio of conductivity when hydrogen peroxide coexists in the cleaning solution and when it does not coexist (when only ammonia is present), and the hydrogen peroxide concentration. FIG. 6 is a system diagram of an embodiment of a cleaning apparatus for S1 wafers embodying the present invention, and FIG. FIG. 8 is a flowchart of the microcomputer used in this embodiment. 1...Cleaning tank 2...Cleaning liquid 3...φ...Heater 4...S1 wafer 5.10...Sample collection pump 6... ... Oxygen concentration measuring section 7 ... Flow cell for transmitted light measurement 8 ...
Ultraviolet light source 9... Ultraviolet detection section 11... Ammonium ion concentration measurement section 12.
... Conductivity detection section 13 ... Operation section 14 ... Interface 15 ... Solenoid valve control section 16.17 ... Solenoid valve 18 ...Hydrogen peroxide tank 19 ...Ammonia water tank 20 ...Microcomputer 25 ...Pure water pump 24 ...Pure water tank 141 [N] Group I song (11Az figure 5L length (Steam ffLn army 4th ammonia: l&'s small size 4 women, 5th figure linear hydrogen concentration 19 ammonia water tank 1 5 holes,! Child species -ku)
, acid t4a su lippin self J5 Kyo 7 figure

Claims (1)

[Claims] A cleaning device that uses a cleaning liquid consisting of hydrogen peroxide, ammonia, and water, in which a sample liquid is collected from a cleaning tank containing the cleaning liquid and sent to a flow cell section for measuring transmitted light, and the sample liquid is irradiated with ultraviolet rays. A first measuring section that measures the amount of ultraviolet light absorbed by oxygen in the solution using an ultraviolet detector, and a pipe that guides the solution exiting the first measuring section, or a pipe system that is provided separately from the pipe that collects the sample liquid. A second measurement section that sends the sample solution to the conductivity measurement flow cell section and measures the conductivity according to the amount of ammonium ions in the solution using a conductivity detector, and a sample solution based on the measurement results of the first and second measurement sections. an arithmetic function block that calculates the concentration of hydrogen peroxide and ammonia in the water; a comparison function block that compares the calculated concentration value with a predetermined setting value; Operate the pump to supply an appropriate amount of each chemical solution or pure water from the hydrogen peroxide, ammonia, or pure water supply tank into the cleaning tank, and issue a control command to control the concentration of chemical components of the cleaning solution in the tank. A cleaning device characterized by comprising a control system comprising a command function block that issues commands.