JP2003347250A - Method of replenishing hydrogen peroxide for correcting its concentration reduction and device used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of replenishing a hydrogen peroxide solution for correcting reduction in hydrogen peroxide concentration which is capable of accurately measuring a hydrogen peroxide concentration and easily replenishing the hydrogen peroxide solution for increasing the hydrogen peroxide concentration to a target value or to the vicinity of the target. <P>SOLUTION: In the method of replenishing hydrogen peroxide for correcting reduction caused by spontaneous decomposition in a hydrogen peroxide concentration in a CMP slurry so as to increase the hydrogen peroxide concentration to a target value or to the vicinity of the target, the concentration of hydrogen peroxide contained in the CMP slurry is measured, a certain amount of a hydrogen peroxide solution not enough to increase its concentration to the target is added to the CMP slurry, then the hydrogen peroxide concentration of the slurry is measured, the amount of the slurry is calculated on the basis of the measurement result, a certain amount of the hydrogen peroxide solution enough to increase its concentration to the target is calculated on the basis of the amount of the slurry, and then the certain amount of the hydrogen peroxide solution is added to the slurry. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the concentration of hydrogen peroxide in a slurry for CMP in a semiconductor process, and replenishing the reduced amount due to the natural decomposition to replenish the reduced amount of hydrogen peroxide as a target concentration. The present invention relates to a method and an apparatus used for the method.

[0002]

2. Description of the Related Art As a method for flattening a semiconductor substrate surface, a CMP (chemical and mechanical polishing) technique is used. The processing liquid used for this CMP is called slurry,
Hydrogen peroxide is added as an oxidizing agent to the slurry used for metal wiring. However, with the recent miniaturization of wiring, stricter compounding accuracy is required,
Hydrogen peroxide, which decomposes spontaneously, is very difficult to handle due to its properties, and there is a problem that depending on the control of the concentration, it greatly affects the process. Therefore, the concentration of hydrogen peroxide has been conventionally controlled.

[0003] In the conventional concentration control method, a sensor for measuring a liquid amount is attached to a mixing tank to measure the liquid amount.
It has been carried out by using a measuring device by ultrasonic waves or by a method using a titrator.

[0004]

However, if the slurry is not stirred, a sediment is formed unless the slurry is stirred. Therefore, since the slurry is constantly stirred, there has been a problem that the measurement of the liquid amount by the sensor cannot be accurately measured due to the fluctuation of the liquid surface. As a result, there was a problem that an accurate hydrogen peroxide replenishment amount could not be calculated. In addition, in order to keep the concentration of hydrogen peroxide within the allowable range of the target concentration by this method, a great deal of labor and skill are required, and there is a problem that the working efficiency is not improved.

When an ultrasonic in-line sensor is used for measuring the hydrogen peroxide concentration, the concentration of the mixed slurry itself and the influence of the surroundings of the sensor (temperature, noise, etc.)
As a result, there was a drawback that accurate measurement was not possible. In addition, even when the titration method is used for measurement, when averaging n times, a large amount of time is required for cleaning before and after in addition to the titration time, so that measurement of hydrogen peroxide that decomposes naturally takes too much time. was there.

[0006] The invention according to claim 1 of the present invention is:
It is an object of the present invention to provide a method for replenishing a reduced hydrogen peroxide concentration, which can accurately measure the concentration of hydrogen peroxide and can easily replenish the concentration at or near the target concentration.

[0007]

According to the first aspect of the present invention, there is provided a semiconductor device comprising:
In a method of replenishing a reduced amount of hydrogen peroxide due to spontaneous decomposition in a slurry for CMP to a target concentration, the concentration of hydrogen peroxide in the slurry is measured, and an amount of hydrogen peroxide that does not reach the target concentration is added to the slurry. The hydrogen peroxide concentration is measured by adding the hydrogen peroxide solution, the liquid amount of the slurry is calculated from the measurement result, and an amount of the hydrogen peroxide solution having the target concentration calculated from the liquid amount is added.

[0008] In short, the present invention calculates the liquid amount of a slurry from the concentration increased by adding a predetermined amount of aqueous hydrogen peroxide, thereby calculating an accurate liquid amount even if the liquid surface fluctuates due to stirring. The gist of the present invention is to make it possible to bring the concentration to a target concentration.

When the measurement of hydrogen peroxide is performed by a titration method using a plurality of titration cells, the measurement of the concentration of hydrogen peroxide can be performed accurately and quickly (claim 2).

[0010] The apparatus used in the method of the present invention comprises a sample feeding pipeline for taking out a slurry connected to a container containing a slurry for CMP, adding a hydrogen peroxide solution, and returning the sample to the container. A pipeline for sending a part of the sample branched from the to a titrator for measuring the hydrogen peroxide concentration by opening a valve, and a pipeline for supplying a hydrogen peroxide solution to the slurry (claim) Item 3).

The pipeline for feeding the slurry to the titration unit is configured so that nitrogen and pure water can be introduced. After measuring the concentration of hydrogen peroxide for one sample, the concentration of hydrogen peroxide is measured for another sample. In the case of measurement, it is preferable that the pipeline be washed with water and then dried by introducing nitrogen (claim 4).

The pipeline for supplying the hydrogen peroxide solution is as follows:
The pipe is immersed in the hydrogen peroxide container, the valve of the pipe is opened, and the inside of the hydrogen peroxide container is pressurized with nitrogen to introduce hydrogen peroxide into the pipe. Preferably, a waste valve is connected, and a valve for supplying hydrogen peroxide from the pipe to the slurry via a check valve is connected (claim 5). When hydrogen peroxide is introduced into the pipe, bubbles are mixed in at first, so that the hydrogen peroxide solution containing the bubbles is discarded from a disposal valve at the end of the pipe.

The valve for supplying the hydrogen peroxide solution to the slurry is preferably a three-way valve. This is because a three-way valve can avoid the influence of the pressure due to the slurry when the hydrogen peroxide solution is supplied.

It is preferable to connect a pipe capable of opening a drain valve to feed the hydrogen peroxide solution to the titration unit to the hydrogen peroxide container (claim 7). By doing so, the concentration of hydrogen peroxide to be added can always be measured accurately and quickly.

The titration unit for measuring the concentration of hydrogen peroxide includes a sampling unit for sampling a predetermined amount of a sample, and a plurality of titration cells connected to the sampling unit, and the titration cell includes a washing shower. A drain valve may be connected to the lower end thereof (claim 8). By using such an apparatus, the concentration of hydrogen peroxide can be measured accurately and quickly.

The sampling section may be formed by a six-way valve.

[0017]

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

FIG. 1 is a principle diagram for explaining the method of the present invention. A tank 101 contains a slurry for CMP of unknown liquid volume. The concentration of the slurry for CMP was measured three times by a titration method, and a concentration of 106 was obtained as an average concentration of three times. It was confirmed that the concentration was lower than the target concentration (target concentration).

Then, a hydrogen peroxide stock solution 104 having a clear concentration and a liquid amount is added to a liquid amount which is equal to or lower than the target concentration, and the tank 10 is added.
The hydrogen peroxide concentration in the tank 102 was measured in the same manner to obtain a concentration 107.

From the difference between the concentration 107 and the target concentration 111 and the amount of the hydrogen peroxide stock 104 added, the target concentration 11
Calculate the required amount of hydrogen peroxide 105 by 1
2 was added. The tank 103 to which the amount of hydrogen peroxide 105 was added
When the concentration of hydrogen peroxide in the inside was measured, a concentration 108 corresponding to the target concentration 111 was obtained. In the drawing, reference numeral 110 denotes an upper limit allowable range, and reference numeral 109 denotes a lower limit allowable range. According to the method of the present invention, the concentration can be reliably set within this allowable range.

FIG. 2 is a piping diagram showing an embodiment of the apparatus of the present invention. In each of three tanks (containers) containing a slurry for CMP of unknown liquid volume, the slurry is taken out and stored. Sample feeding pipelines 201, 202, and 203 are connected to return to the same tank after adding hydrogen oxide.

Sample sending pipelines 201, 202, 2
03 is branched, and the sample introduction valves 209 and 21 at the branches are provided.
By opening 0,211, the slurry sample is sent to the titration unit 206. Pipe 223 and valves 209, 210, 21 for sending the slurry sample to the titration unit
1 are connected so as to be orthogonal to each other via branched short pipes 224, 225, and 226. A pure water introduction valve 208 for washing the inside of the pipe 223 and a nitrogen introduction valve 207 for washing with pure water and drying are orthogonally connected via a short pipe at the upper end of the pipe 223 that sends the sample to the titration unit. Have been.

Sample feeding pipelines 201, 202, 2
03, valves 212 and 21 for adding a hydrogen peroxide solution to the slurry after the slurry sample was sent to the titration unit 206.
3,214 are connected respectively.

Valves 212 and 2 for adding a hydrogen peroxide solution
The short pipes connected to 13, 214 are connected to a pipe 224 immersed in the hydrogen peroxide storage tank 205 via check valves 217, 218, 219 and short pipes, respectively.

Introducing nitrogen through the pressure regulating valve 220,
When the inside of the hydrogen peroxide storage tank 205 is pressurized and the hydrogen peroxide addition valve 215 is opened, the hydrogen peroxide is introduced into the pipe 224, but bubbles are mixed in the hydrogen peroxide solution immediately after the introduction. Therefore, the valve 216 at the upper end of the pipe 224 is opened to discard the hydrogen peroxide solution. Then, the valve 216 is closed, and the valves 212, 213, and 2 for adding hydrogen peroxide.
14 is opened, and a hydrogen peroxide solution is added to the sample sending pipelines 201, 202, and 203 from the short pipes in which the pipes 224 are orthogonally connected.

In the above embodiment, the valves 212, 213 and 214 for adding the hydrogen peroxide solution are formed by three-way valves. When the hydrogen peroxide solution is introduced, it communicates with the sample supply pipelines 201, 202 and 203 in front of the hydrogen peroxide supply pipe and the same valve, and the sample supply pipelines 201, 202 and 203 up to this valve. 20
This is because the influence of the pressure caused by the passage of the slurry is avoided by shutting off the flow rate of the slurry. Also, check valves 217, 21
8, 219 prevent the slurry from flowing backward.

The hydrogen peroxide solution in the hydrogen peroxide storage tank 205 is sent from the pipe 227 to the titration unit 206 by opening the hydrogen peroxide stock solution introduction valve 222, and the concentration of the hydrogen peroxide solution is increased. Can be measured.

In FIG. 2, reference numeral 221 denotes a level meter, which checks the amount of aqueous hydrogen peroxide, and when the amount of aqueous hydrogen peroxide falls below a predetermined amount, opens an exhaust valve 228 to discharge nitrogen and then opens a valve 204 to open the valve. As shown by the arrow, an aqueous solution of hydrogen peroxide is introduced.

Using the above-described apparatus, a predetermined amount of aqueous hydrogen peroxide is added, and each container and sample sending pipeline 20 are added.
1, 202, and 203 are circulated so as to have a uniform concentration, and the concentration of hydrogen peroxide is measured. In order to confirm whether or not the concentration is uniform, the measurement may be performed a plurality of times over time. Then, an aqueous solution of hydrogen peroxide having a target concentration is added, circulated in the same manner, and measurement may be performed a plurality of times until the concentration becomes uniform over time.

In the above embodiment, since three types of slurry storage containers are used, the sample feeding pipeline 2
Although 01, 202 and 203 are provided, it goes without saying that the number is not particularly limited.

FIG. 3 shows an embodiment of the titration unit of the present invention. The slurry from 206 in FIG.
07. The six-way valve 307 serves as a sample injector. When the six-way valve 307 is in the state of (B), the slurry is introduced into the sample loop 315, and in the state of (A), a certain amount of sample is in the sample loop 315. Is held.

The held sample opens the three-way valve 308 and introduces water 302 to supply a slurry sample to the sample cell 305 or 306. The sample cell 305 or 306 is equipped with a stirring propeller, potential measurement electrodes 313 and 314, and a pipe for dropping a reagent (cerium ammonium sulfate) 303. The measurement of the concentration of hydrogen peroxide using this cell may be performed in the same manner as in the prior art.

In the sample cell 305 or 306 of the present invention,
Waste liquid valves 311 and 312 and washing showers 316 and 3
17 are equipped. With this configuration, the sample cell 305 or 306 is extremely easily cleaned by discharging the liquid after measurement from below and flowing the shower from above.

Using the above apparatus, the method of the present invention was applied to a CAP slurry containing hydrogen peroxide of unknown concentration at a target concentration of 1.5%. FIG. 4 shows the results. In the figure, those having the same meaning as in FIG.

A slurry having an unknown concentration was measured twice, and a plot 106a was obtained as an average. Then, 22 ml of the hydrogen peroxide stock solution 104a was replenished, stirred and circulated, and the concentration of hydrogen peroxide was measured to obtain a plot 107a. From the difference between these two plots and the initial replenishment of 22 ml, the required replenishment amount of the hydrogen peroxide solution until the target concentration is reached is calculated, and the required hydrogen peroxide solution (105a)
70 ml were obtained. This amount was replenished, and the slurry was stirred and circulated to measure the concentration of hydrogen peroxide to obtain an actually measured value of 111a.

Table 1 shows the results of measuring the concentration of hydrogen peroxide at predetermined time intervals while circulating the slurry.
In addition, 104a was measured after 10 minutes, and 105a was measured after 30 minutes.

[0037]

[Table 1] As is clear from the results in Table 1, according to the method of the present invention, the concentration of hydrogen peroxide in the CAP slurry can be set to a value very close to the target concentration. It is impossible with the conventional method to make the value close to the target density with reproducibility as described above.

In the conventional method, it takes a great deal of labor and skill to keep the hydrogen peroxide within the allowable range.
According to the method of the present invention, the amount of liquid in the CAP slurry can be accurately grasped, and the exact amount of added hydrogen peroxide can be determined, so that the target concentration or a value very close to the target concentration can be obtained. . Also, using multiple titration cells, drain the slurry after the test from the bottom of the titration cell,
When the titration cell is washed with the washing showers 316 and 317, the washing time before and after the measurement is extremely shortened. Therefore, even when the averaging is performed n times, the measurement can be performed in an extremely short time as compared with the related art.

[0039]

As described above, according to the present invention, the CMP
In addition to keeping the hydrogen peroxide in the slurry for use at a value very close to the target concentration, it also eliminates the labor and skill required for inspection due to the fluctuation of the liquid surface of the slurry, thus dramatically improving work efficiency. It has an enormous effect of improving.

[Brief description of the drawings]

FIG. 1 is a principle diagram for explaining a method of the present invention.

FIG. 2 is a piping diagram showing one embodiment of the device of the present invention.

FIG. 3 is a piping diagram showing one embodiment of the titration unit of the present invention.

FIG. 4 is a graph showing the relationship between elapsed time and the concentration of hydrogen peroxide in a slurry according to the method of the present invention.

[Description of Signs] 101: CAP slurry storage tank 102: A tank in which a hydrogen peroxide solution having a target concentration or less is added to the slurry 103: A tank in which a hydrogen peroxide solution having a target concentration is added to the slurry 104, 104a... Additional hydrogen peroxide solutions 105, 105a to be not more than the target concentration.... Additional hydrogen peroxide solutions 106, 106a to be the target concentration. Hydrogen peroxide concentration 107, 107a in the slurry for CAP. ... Concentration 108 after addition of hydrogen peroxide solution below the target concentration 108 concentration 109 after addition of hydrogen peroxide solution in an amount to reach the target concentration 109... Allowable lower limit of hydrogen peroxide concentration in slurry Range 110: allowable range of upper limit of hydrogen peroxide concentration in slurry 111, 111a: actual measured value of hydrogen peroxide concentration in slurry

Claims (9)

[Claims] 1. A method for replenishing a reduced amount of hydrogen peroxide due to spontaneous decomposition in a slurry for CMP in a semiconductor process to a target concentration, wherein the concentration of hydrogen peroxide in the slurry is measured, and Add an inconsistent amount of aqueous hydrogen peroxide to measure the concentration of hydrogen peroxide, calculate the liquid volume of the slurry from the measurement results, and add the amount of hydrogen peroxide aqueous solution that has the target concentration calculated from the liquid amount. A method of replenishing a reduced amount of hydrogen peroxide due to spontaneous decomposition in a slurry to obtain a target concentration. 2. The method according to claim 1, wherein the measurement of the hydrogen peroxide is performed by a titration method using a plurality of titration cells. 3. A sample feeding pipeline for taking out the slurry connected to the container containing the slurry for CMP, adding a hydrogen peroxide solution and returning the sample to the container, and a part of the sample branched from the sample sending pipeline. A pipeline for opening a valve to a titration unit for measuring the concentration of hydrogen peroxide by opening a valve, and a pipeline for supplying a hydrogen peroxide solution to the slurry. Equipment to do. 4. A pipeline for feeding said slurry to a titration unit is configured so that nitrogen and pure water can be introduced. After measuring the concentration of hydrogen peroxide for one sample, the peroxide for another sample is measured. 4. The apparatus according to claim 3, wherein when measuring the hydrogen concentration, the pipeline is washed with water and then dried by introducing nitrogen. 5. A pipeline for supplying a hydrogen peroxide solution, wherein a pipe is immersed in a hydrogen peroxide storage container, a valve of the pipe is opened, and the inside of the hydrogen peroxide storage container is pressurized with nitrogen to obtain a peroxide. Hydrogen water is introduced into the pipe, a hydrogen peroxide water disposal valve is connected to the pipe end, and a valve that supplies the hydrogen peroxide water from the pipe to the slurry via a check valve is connected. Item 5. The apparatus according to Item 4. 6. The apparatus according to claim 5, wherein the valve for supplying hydrogen peroxide to the slurry is a three-way valve. 7. The apparatus according to claim 5, wherein a pipe capable of opening a drain valve and sending hydrogen peroxide to the titration unit is connected to the hydrogen peroxide storage container. 8. A titrator for measuring the concentration of hydrogen peroxide,
The apparatus includes a collection unit for collecting a predetermined amount of a sample, and a plurality of titration cells connected to the collection unit. The titration cell includes a washing shower, and a lower end thereof is connected to a drain valve. Apparatus according to any of claims 5 to 7. 9. The apparatus according to claim 8, wherein said sampling section is formed by a six-way valve.