JPH043425A - Method and device for evaluating cleanliness of washing liquid - Google Patents

Abstract

PURPOSE:To enable an amount of metal and reducing impurities which are brought into a washing liquid to be indirectly evaluated in-line by evaluating cleanliness by measuring composition change of the washing liquid. CONSTITUTION:A washing liquid 2 is introduced into a sample loop of a manifold 10 by closing a solenoid valve 17. Then a washing liquid 2 within the sample loop is sent to a detection part 12 at a nitrous acid ion concentration measuring part 4 by a liquid-feeding pump 20 by switching a channel of the manifold 10, thus enabling a concentration of the nitrous acid ion to be measured. As this method, by utilizing that absorbance of ultra-violet rays and concentration of the nitrous acid ion are in linear relationship, the concentration of the nitrous acid ion is obtained based on a measurement result of the previously measured absorbance and concentration by measuring the absorbance of ultra-violet rays whose wavelength is for example 354nm and an amount of coexisting metal which is in linear relationship with an amount of produced nitrous acid ion which is included within the washing liquid 2, namely the amount of produced nitrous acid ion, and a reducing impurity, especially a copper ion is calculated, thus indirectly obtaining the cleanliness of the washing liquid 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a technique for evaluating the cleanliness of a cleaning liquid, and in particular to a cleaning liquid used for cleaning objects to be cleaned such as semiconductor wafers in the manufacturing process of semiconductor integrated circuit devices. The present invention relates to a technique that is effective when applied to a method and apparatus for evaluating the cleanliness of a cleaning liquid, which enables the evaluation of the cleanliness of a cleaning liquid.

“Prior Art” Cleaning liquids used for cleaning semiconductor wafers include, for example, hydrogen peroxide (H202) and ammonia (NH, OH).
) and water (H20), and is usually heated to about 80° C. for use, so hydrogen peroxide decomposes in several tens of minutes due to thermal decomposition, causing deterioration of the cleaning solution.

Conventionally, the concentration of hydrogen peroxide has been determined by a method using ultraviolet absorption as described in Japanese Patent Publication No. 16901/1983;
It is measured by a titration method using a redox reaction described in JIS K 8230-1987.

For example, in a method that uses ultraviolet absorption,
The concentration of the hydrogen peroxide component in the cleaning solution consisting of hydrogen peroxide, ammonia and water is measured by measuring the absorbance of ultraviolet light having a wavelength of around 300 nm, and the ammonia concentration can be continuously measured using an ion electrode.

[This is a problem to be solved by the invention. However, in the prior art as described above, chemical solution management is performed by measuring the concentration of hydrogen peroxide and ammonia components in the cleaning solution, and hydrogen peroxide or ammonia is replenished as the concentration decreases.] The purpose is to stabilize the cleaning effect by cleaning the cleaning solution, but there is no consideration given to contamination by metals and reducing impurities brought into the cleaning solution, and re-contamination of semiconductor wafers by these impurities. No consideration is given to the cleanliness of the cleaning liquid, which greatly affects the yield of semiconductor integrated circuit devices. Therefore,
In the manufacturing process of semiconductor integrated circuit devices, which are becoming increasingly miniaturized,
There is a problem in that it is not possible to obtain a defect-free, high-quality semiconductor non-integrated circuit device.

Therefore, the present inventor focused on the fact that the decomposition of hydrogen peroxide is significantly accelerated when metals and reducing impurities are brought into the cleaning solution of an ammoniacal alkaline solution containing hydrogen peroxide. Iron (Fe), copper (Cu
) or when 1ooppb of nickel (Ni) ions coexist, by measuring the concentration C8 of hydrogen peroxide at time t0 and the concentration C1 at time t,
It has been found that the decomposition rate constant k can be determined from the following equation (1).

k= (1/ (t+ -to)) Iin (C+
/Co)・・・・(1) In other words, Figure 5 shows the results of determining the decomposition rate constant k of hydrogen peroxide at a liquid temperature of 80°C, and the larger the decomposition rate constant k, the more contaminated the cleaning liquid is. represents.

In addition, especially when copper (Cu) ions coexist in the cleaning solution, the copper ions act as a catalyst and nitrite ions (N
For example, as can be seen from the relationship between the amount of copper ions coexisting in the cleaning solution and the amount of nitrite ions produced in the cleaning solution, we focus on the fact that nitrite ions are generated in the cleaning solution. is approximately 2X10' for the coexisting amount of copper ions.
It was discovered that the amount of coexisting copper ions can be indirectly measured with high sensitivity by measuring the concentration of nitrite ions.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and apparatus for evaluating the cleanliness of a cleaning liquid, which makes it possible to indirectly evaluate in-line the amount of metal and reducing impurities brought into the cleaning liquid based on the amount of nitrite ions produced. There is a particular thing.

Another object of the present invention is a method for evaluating the cleanliness of a cleaning solution, which enables indirect in-line evaluation of the amount of metals and reducing impurities brought into the cleaning solution based on the decomposition rate of the concentration of hydrogen peroxide. and equipment.

The above and other objects and novel features of the present invention will become apparent from the detailed description of this specification and the accompanying drawings.

Means for Solving the 100 Problems] A brief outline of representative ones among the hatching disclosed in the present application is as follows.

That is, the cleaning liquid cleanliness evaluation method of the present invention is an evaluation method for evaluating the cleanliness of a cleaning liquid used for cleaning an object to be cleaned, and the cleanliness is evaluated by measuring a change in the composition of the cleaning liquid. It is something. In this case, the cleaning liquid consists of hydrogen peroxide solution, ammonia water, and water.

Further, in this case, the cleanliness of the cleaning liquid is evaluated by measuring the amount of nitrite ions generated in the cleaning liquid.

Furthermore, as another cleanliness evaluation method, the cleanliness is evaluated by determining the decomposition rate of hydrogen peroxide in the cleaning liquid. In this case, the amount of ultraviolet light absorbed by the oxygen in the forward cleaning solution is diluted and reduced by pure water fed at a constant flow rate, and the time required for the absorption amount to decrease to the desired amount is measured to determine the concentration of hydrogen peroxide. is determined, and the decomposition rate of the hydrogen peroxide is determined based on the concentration of the hydrogen peroxide.

Further, the cleaning liquid cleanliness evaluation apparatus of the present invention is an evaluation apparatus that measures a change in the composition of the cleaning liquid and evaluates the cleanliness of the cleaning liquid based on the composition change, wherein a certain amount of the cleaning liquid is sampled,
comprising a nitrite ion concentration measurement unit that detects ultraviolet absorbance due to nitrite ions in the collected cleaning liquid, and a forward nitrite ion concentration measurement unit that measures the amount of nitrite ions generated in the cleaning liquid; The cleanliness of the cleaning liquid is evaluated based on the amount of nitrite ions produced.

Furthermore, another cleanliness evaluation device of the present invention is an evaluation device that measures a change in the composition of a cleaning solution and evaluates the cleanliness of the cleaning solution based on the composition change, wherein a certain amount of the cleaning solution is sampled, and the A hydrogen peroxide concentration measuring section is provided which dilutes and mixes a cleaning solution and pure water and detects the ultraviolet absorbance of the diluted and mixed cleaning solution due to oxygen, and the hydrogen peroxide concentration measuring section measures the decomposition rate of hydrogen peroxide in the cleaning solution. The cleanliness of the cleaning liquid is evaluated based on the decomposition rate of hydrogen peroxide.

[Function] The method and device for evaluating the cleanliness of a cleaning liquid described above includes a nitrite ion concentration measuring section that collects a certain amount of the cleaning liquid and detects the ultraviolet absorbance due to nitrite ions in the collected cleaning liquid. This nitrite ion concentration measuring section can measure the amount of nitrite ions generated in the cleaning solution due to changes in the composition of the cleaning solution. This results in
The cleanliness of the cleaning solution can be indirectly evaluated from the amount of nitrite ions produced.

In addition, the other method and device for evaluating the cleanliness of a cleaning solution described above collects a certain amount of cleaning solution, dilutes and mixes the collected cleaning solution with pure water, and detects the ultraviolet absorbance of the diluted and mixed cleaning solution due to oxygen. By being equipped with a hydrogen peroxide concentration measuring section, the hydrogen peroxide concentration measuring section measures the time required for the ultraviolet absorbance of the cleaning solution diluted with pure water to decrease to the desired amount of absorption, and uses this time to determine whether the cleaning solution The decomposition rate of hydrogen peroxide in the cleaning solution can be determined by changing the composition of t. Thereby, the cleanliness of the cleaning liquid can be indirectly evaluated from the decomposition rate of hydrogen peroxide.

[Example] FIG. 1 is a schematic configuration diagram showing a cleaning liquid cleanliness evaluation device according to an embodiment of the present invention, and FIG. FIG. 3 is a measurement diagram showing the relationship between ultraviolet absorbance due to nitrite ions in the cleaning solution and measurement time, and FIG. 4 is a measurement diagram showing the relationship between ultraviolet absorbance due to hydrogen peroxide in the cleaning solution and measurement time.

First, the configuration of the cleaning liquid cleanliness evaluation apparatus of this embodiment will be explained with reference to FIG.

The cleanliness evaluation device of this embodiment is a cleanliness evaluation device for a cleaning liquid used to clean a semiconductor wafer as an example of an object to be cleaned. A nitrite ion concentration measuring section 4 collects a certain amount of the cleaning liquid 2 in the processing tank 3 and detects the ultraviolet absorbance due to nitrite ions in the cleaning liquid 2, and dilutes the collected cleaning liquid 2 and pure water. and a monitor section 6 equipped with a hydrogen peroxide concentration measuring section 5 for detecting the ultraviolet absorbance of the mixed cleaning liquid 2 due to oxygen. A flow path is formed from the upper part of the treatment tank 3 to the nitrite ion concentration measuring section 4 and the hydrogen peroxide concentration measuring section 5.

In the processing tank 3, a flow path is formed between the top and bottom of the processing tank 3 in order to circulate the cleaning liquid 2, and the cleaning liquid that has automatically flowed from the top of the processing tank 3 into the flow path is transferred to the bottom of the processing tank 3. A pressure pump 7 for force-feeding the cleaning liquid 2, a filter 8 for removing impurities contained in the cleaning liquid 2, and an overflow tank 9 for temporarily storing the overflowing cleaning liquid 2 are provided. Further, the semiconductor wafer 1 is immersed in the cleaning liquid 2 in the processing tank 3, and the single conductor wafer 1 is cleaned by the circulation of the cleaning liquid 2.

The nitrite ion concentration measurement unit 4 includes a manifold 10 for collecting a certain amount of cleaning liquid 2, a collection pump 11 for guiding the cleaning liquid 2 to this seven-fold 10, and a measuring unit 4 for measuring ultraviolet absorbance due to nitrite ions in the collected cleaning liquid 2. Detection unit 12 to detect
It consists of The detection unit 12 includes, for example, an ultraviolet light source 13 and a flow cell 1 as shown in FIG.
4 and an ultraviolet detector 15, the cleaning liquid 2 flowing through the flow cell 14 is irradiated with ultraviolet rays, and the ultraviolet detector 15 detects the absorbance of the ultraviolet rays by nitrite ions.

In addition, the cleaning liquid 2 collected by the collection pump 11 is
Only the degassed cleaning liquid 2 is sent under pressure to the degassing cell 16 for defoaming air, and the degassed cleaning liquid 2 is led to the manifold 10, and the remaining cleaning liquid 2 containing air bubbles is sent to the overflow tank 9 of the processing tank 3 via the electromagnetic valve 17. It will be done.

The hydrogen peroxide concentration measurement unit 5 includes a mixing chamber 19 for diluting and mixing the collected cleaning liquid 2 and pure water 18, and a liquid feeding pump 20 for guiding the quantitatively mixed cleaning liquid 2 into the mixing chamber 19. , and a detection unit 21 that detects the ultraviolet absorbance due to oxygen in the diluted and mixed cleaning liquid 2. The detection unit 21 includes an ultraviolet light source 13, a flow cell 14, and an ultraviolet detector 15 similarly to the nitrite ion concentration measurement unit 4, and detects the absorbance of ultraviolet rays due to oxygen in the diluted and mixed cleaning liquid 2 flowing inside the flow cell 14. It is something.

Next, the operation of this embodiment will be explained.

First, impurities are removed from the processing tank 3 by the filter 8, and the overflow cleaning liquid 2 is sent to the pressure pump 7.
is circulated by Then, the semiconductor unit 1 to be cleaned is immersed in this processing tank 3 for a predetermined period of time to perform the cleaning process.

Then, each time a predetermined in-line cleaning process is completed,
Alternatively, every predetermined period of time, the cleaning liquid 2 in the processing tank 3 is guided to the degassing cell 16 in the monitor unit 6 by the collection pump 11, and the excess cleaning liquid 2 containing air bubbles is removed through the opened electromagnetic valve 17. Send to overflow tank 9.

After that, the solenoid valve 17 is closed and the cleaning liquid 2 is transferred to the manifold 10.
into the sample loop. Then, the flow path of the manifold 10 is switched and the cleaning liquid 2 in the sample loop is transferred to the detection unit 1 of the nitrite ion concentration measurement unit 4 by the liquid sending pump 20.
2 and measure the concentration of nitrite ions.

This method takes advantage of the fact that there is a proportional relationship between the absorbance of ultraviolet rays and the concentration of nitrite ions (NO2-) as shown in Figure 3. For example, by measuring the absorbance of ultraviolet rays with a wavelength of 354 nm, The concentration of nitrite ions is calculated based on the measured absorbance and concentration, and the amount of nitrite ions produced in the cleaning solution 2, that is, the amount of metals and reductions that are proportional to the amount of nitrite ions produced, is determined. The cleanliness of the cleaning liquid 2 can be indirectly determined by calculating the amount of coexisting physical impurities, especially copper ions.

In this case, if the coexisting amount of copper ions is smaller than the preset value, the cleaning process of the semiconductor wafer 1 is continued without replacing the cleaning liquid 2; Replace with clean cleaning solution 2'
, J), the semiconductor wafer 1 is cleaned.

Next, along with the cleaning liquid 2 whose concentration of nitrite ions has been measured, a certain amount of pure water 18 is sent to the mixing chamber 19 by the liquid feeding pump 20. And mixing room 1
The cleaning liquid 2 diluted and mixed in the hydrogen peroxide concentration measuring section 9 is sent to the detection section 21 of the hydrogen peroxide concentration measuring section 5, and the concentration of hydrogen peroxide is measured.

In this method, as shown in Figure 4, the peak width of the ultraviolet absorbance, h, and the concentration of hydrogen peroxide are as follows (2
), for example, if the wavelength is 300n
By measuring the peak width H of the absorbance of ultraviolet rays of m, the concentration of hydrogen peroxide can be indirectly determined based on the measurement result of the absorbance peak width and concentration measured in advance.

H= (V/Q) l n 10 ・io gC-A・
... (2) However, v: Capacity of the mixing chamber 19 [m1] Q: Liquid feeding flow rate of the pure water 18 from the liquid feeding pump 20 Em1/min C: Concentration of hydrogen peroxide in the cleaning liquid 2 [%:.

A° constant shall be shown.

That is, the concentration of hydrogen peroxide in the cleaning solution 2 at the absorbance peak width, e, h, is determined.
l, C+, h2. By substituting each value of Ca into equation (1), the decomposition rate constant k of hydrogen peroxide, that is, the coexisting amount of metals and reducing impurities, especially iron, nickel, or copper ions, contained in cleaning solution 2 can be calculated. The cleanliness of the cleaning liquid 2 can be indirectly evaluated.

In this case, if the coexistence amount of metallic impurities is smaller than the preset value, similar to the nitrite ion concentration setting described above, the cleaning process of the semiconductor wafer 1 is continued without replacing the cleaning liquid 2, and the - blade metallic impurities are removed. If the amount of coexistence is larger than the set value, the cleaning liquid 2 is replaced and the semiconductor wafer 1 is cleaned using the clean cleaning liquid.

Therefore, according to the cleanliness evaluation apparatus of the cleaning liquid 2 of this embodiment, the nitrite ion concentration measuring section 4 is configured to collect a certain amount of the cleaning liquid 2 and detect the ultraviolet absorbance due to nitrite ions in the collected cleaning liquid 2. By providing this, the nitrite ion concentration measuring section 4 can measure the amount of nitrite ions generated in the cleaning liquid 2 due to a change in the composition of the cleaning liquid 2.

Thereby, the cleanliness of the cleaning liquid 2 can be indirectly evaluated from the amount of nitrite ions produced by in-line measurement.

Further, the collected cleaning liquid 2 and pure water 18 are diluted and mixed,
By providing the hydrogen peroxide concentration measuring section 5 that detects the ultraviolet absorbance of the diluted and mixed cleaning liquid 2 due to oxygen, the hydrogen peroxide concentration measuring section 5 can adjust the ultraviolet absorbance of the cleaning liquid 2 diluted with pure water 18 to a desired value. The time required for the amount of hydrogen peroxide absorbed to decrease to 1 is measured, and the decomposition rate of hydrogen peroxide in the cleaning liquid 2 due to a change in the composition of the cleaning liquid 2 can be determined from this time. Thereby, the cleanliness of the cleaning liquid 2 can be indirectly evaluated from the decomposition rate of hydrogen peroxide by in-line measurement.

As above, the invention made by the present inventor has been specifically explained based on Examples, but it should be noted that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Not even.

For example, with regard to the cleanliness evaluation device of this embodiment, a case has been described in which the cleaning liquid 2 is guided into the monitor section 6 by the collection pump 11, but the present invention is not limited to the above embodiment. It is also applicable to the case where the liquid is sucked into the monitor section 6 by suction using a suction device.

In addition, regarding the concentration measurement of nitrite ions and hydrogen peroxide in the cleanliness evaluation device of this example, each concentration measuring section 4.5
Although the case has been described in which the filter is provided in the fluid path leading from the upper part of the processing tank 3 to the monitor unit 6, it is also applicable to the case where it is provided in the middle of the fluid path t for circulating the cleaning liquid 2 in the processing tank 3, for example. Furthermore, regarding each method of measuring the concentration of the cleaning liquid 2, it is also possible to sample a part of the cleaning liquid 2 and measure it by redox titration or ion chromatography.

Sarani, Cleaning Solution 2) explained about the cleaning solution 2, which is an ammoniacal alkaline solution containing hydrogen peroxide, but is it close to pure water? ) It is also applicable to the case where hydrogen peroxide and ammonia are added to the water-soluble cleaning liquid 2 and the cleanliness of the water-soluble cleaning liquid 2 is evaluated.

In the above description, the invention made by the present inventor will mainly be described as a cleaning liquid 2 used for cleaning semiconductor urchins/Xl in the manufacturing process of semiconductor integrated circuit devices, which is the field of application of the invention.
We explained the case where it was applied to a cleanliness evaluation device.
The cleanliness evaluation device for the cleaning liquid 2 for cleaning objects to be cleaned such as masks of glass substrates, ceramic substrates, and even semiconductor wafers 1 is not limited to this. It is also widely applicable.

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

In other words, using an evaluation method and apparatus that measures changes in the composition of the cleaning solution and evaluates the cleanliness of the cleaning solution based on this compositional change, a certain amount of the cleaning solution is collected, and the ultraviolet absorbance due to nitrite ions in the collected cleaning solution is measured. By being equipped with a nitrite ion concentration measuring section that detects nitrite ions, the nitrite ion concentration measuring section measures the amount of metal and reducing impurities brought into the cleaning solution by measuring the amount of nitrite ions generated in the cleaning solution due to changes in the composition of the cleaning solution. Since the amount of nitrite ions produced can be measured indirectly, the cleanliness of the cleaning solution can be evaluated by in-line measurement from the amount of nitrite ions produced.

In addition, it is equipped with a hydrogen peroxide concentration measuring section that collects a certain amount of cleaning fluid, dilutes and mixes the collected cleaning fluid with pure water, and detects the ultraviolet absorbance of the diluted and mixed cleaning fluid due to oxygen. The hydrogen oxide concentration measurement unit measures the amount of metal and reducing impurities brought into the cleaning solution by measuring the time required for the ultraviolet absorbance of the cleaning solution diluted with pure water to decrease to the desired absorption amount, and using this time to determine the amount of metal and reducing impurities brought into the cleaning solution. Since the decomposition rate of hydrogen peroxide in the cleaning liquid due to compositional changes can be determined indirectly, the cleanliness of the cleaning liquid can be evaluated by in-line measurement from the decomposition rate of hydrogen peroxide.

Furthermore, since the concentration of hydrogen peroxide in the cleaning solution can be measured by diluting and mixing with pure water, the concentration of hydrogen peroxide in the cleaning solution can be measured with high accuracy without being affected by the buffering effect caused by air bubbles and pH changes in the cleaning solution. It is possible to evaluate cleanliness.

As a result, contamination by metals and reducing impurities brought into the cleaning solution and recontamination of the object to be cleaned by these impurities are reduced, improving the yield of semiconductor integrated circuit devices and producing high-quality semiconductor integrated circuit devices. It is possible to obtain a method and apparatus for evaluating the cleanliness of a cleaning liquid, which enables the production of a cleaning liquid.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a cleaning liquid cleanliness evaluation device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing a detection section of the cleanliness evaluation device of this embodiment. FIG. 3 is a cleaning liquid Figure 4 is an explanatory diagram showing the relationship between ultraviolet absorbance due to nitrite ions in the cleaning liquid and measurement time. FIG. 6 is an explanatory diagram showing the relationship between the coexisting metal ions and the decomposition rate of hydrogen peroxide, and FIG. 6 is an explanatory diagram showing the relationship between the amount of coexisting copper ions in the cleaning solution and the amount of nitrite ions produced. 1... Semiconductor wafer (object to be cleaned), 2... Cleaning liquid,
3... Processing tank, 4... Nitrite ion concentration measuring section, 5
...Hydrogen peroxide concentration measurement section, 6.Monitor section, 7.
... Pressure pump, 8 ... Filter, 9 ... Overflow tank, 10 ... Manifold, 11 ... Collection pump, 12 ... Detection section, 13 ... Ultraviolet light source, 14.
...Flow cell, 15...Ultraviolet detector, 16...
Defoaming cell, 17... Solenoid valve, 18... Pure water, 19.
...Mixing chamber, 20...Liquid pump, 21...
Detection unit. Figure Figure Time Figure Time Figure Cleaning liquid composition Cleaning liquid temperature NH, 0H H2O2: H, 0 80℃

Claims (1)

[Claims] 1. An evaluation method for evaluating the cleanliness of a cleaning liquid used for cleaning an object to be cleaned, characterized in that the cleanliness is evaluated by measuring a change in the composition of the cleaning liquid. Method for evaluating cleanliness of cleaning fluid. 2. The cleaning liquid cleanliness evaluation method according to claim 1, wherein the cleaning liquid comprises hydrogen peroxide solution, ammonia water, and water. 3. The cleaning liquid cleanliness evaluation method according to claim 1, wherein the cleanliness is evaluated by measuring the amount of nitrite ions generated in the cleaning liquid. 4. The cleaning liquid cleanliness evaluation method according to claim 1, wherein the cleanliness is evaluated by determining the decomposition rate of hydrogen peroxide in the cleaning liquid. 5. Determine the concentration of hydrogen peroxide by measuring the time required for the amount of ultraviolet light absorbed by oxygen in the cleaning solution to be diluted and reduced by pure water fed at a constant flow rate and to reduce to the desired amount of absorption; 5. The cleaning liquid cleanliness evaluation method according to claim 4, wherein the decomposition rate of the hydrogen peroxide is determined based on the concentration of the hydrogen peroxide. 6. An evaluation device that measures changes in the composition of a cleaning solution and evaluates the cleanliness of the cleaning solution based on the composition changes, wherein a certain amount of the cleaning solution is collected and the ultraviolet absorbance due to nitrite ions in the collected cleaning solution is detected. a nitrite ion concentration measuring section, the nitrite ion concentration measuring section measures the amount of nitrite ions generated in the cleaning solution, and the cleanliness of the cleaning solution is evaluated based on the amount of nitrite ions produced. A cleaning liquid cleanliness evaluation device characterized by: 7. An evaluation device that measures changes in the composition of a cleaning solution and evaluates the degree of cleaning of the cleaning solution based on the changes in composition, wherein a certain amount of the cleaning solution is collected, the collected cleaning solution and pure water are diluted and mixed, and the cleaning solution is diluted and mixed with pure water. A hydrogen peroxide concentration measuring section is provided to detect the ultraviolet absorbance of the diluted and mixed cleaning solution due to oxygen, and the hydrogen peroxide concentration measuring section determines the decomposition rate of hydrogen peroxide in the cleaning solution, and from the decomposition rate of the hydrogen peroxide. A cleanliness evaluation device for a cleaning liquid, characterized in that the cleanliness of the cleaning liquid is evaluated.