JPH05216241A - Automatic diluting device for developer - Google Patents

Abstract

PURPOSE:To enable the execution of development of resist patterns with high accuracy by providing a load cell which measures the liquid volume in a compounding tank and an automatic titration device by potential difference measurement and executing control by a sequence controller. CONSTITUTION:A developing stock soln. is fed from a developing stock soln. tank 1 to a compounding tank 3 by using a transfer pump 2. This transfer pump 2 is stopped when a prescribed volume is attained. The transfer rate of this developing stock soln. is controlled by control valves 4 and 5. Ultrapure water is then sent from a piping 6 to the compounding tank 3. The volume of the ultrapure water is controlled by a control valve 7. The valve is shut when a set volume is attained. The respective liquid volumes sent to the compounding tank 3 are measured by a load cell 8 and the respective control valves 4, 5 and pump 2 are rapidly and exactly controlled via a sequence controller 9. After the developing stock soln. and the ultrapure water are fed into the compounding tank 3, the liquids in the tank are mixed for a specified period of time by using a circulating pump 10 while the liquid volumes are controlled by a control valve 11. The liquid mixture is partly sent to the automatic titration device 12 by which the concn. of the liquid mixture is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic developer diluting device for producing an alkaline developing solution used for developing a positive resist in a semiconductor manufacturing process or the like.

[0002]

2. Description of the Related Art In recent years, the semiconductor industry has been remarkably developed. Particularly, in recent semiconductor integrated circuits, as represented by VLSI, the minimum line width when drawing a circuit has been gradually miniaturized with high integration, There is a demand for accurate formation of a resist pattern. There is a positive resist that meets this demand, and since it has a higher resolution than a conventional negative resist, it is often used for drawing highly integrated circuits.

An alkaline aqueous solution is generally used as a developing solution for the positive type resist, but it is considered that this developing solution is as important as the resist in order to obtain high resolution and accurate dimensional accuracy of the resist. It is said. That is, in order to obtain clear images, excellent resolution and stability, a developing solution having a concentration suitable for the positive resist used is required.
In particular, with the recent high integration of semiconductors, the pattern size has become finer and the sub-micron era has entered, and the improvement of the accuracy of the development density has become a problem in order to reduce the variation in the effective sensitivity of the resist.

It is extremely difficult to control the concentration of the developing solution with high accuracy, and this side cannot be controlled by the side using the developing solution in a semiconductor factory.
A developing solution prepared by diluting a developing solution with ultrapure water to a desired concentration is used. The dilution ratio of the developing stock solution varies depending on the concentration of the stock solution and the purpose of use, but is usually 5
It is about 10 times. As a device for diluting the developing solution, Japanese Patent Application Laid-Open No. 62-27624 proposes a device for adjusting the concentration by measuring conductivity.

[0005]

In the prepared developing solution, the amount of the solution is increased and the kind thereof is increased according to the dilution ratio.
Therefore, when purchasing and using a developer that has been prepared to the desired concentration on the side that uses the developer, such as in semiconductor factories, the cost of filling the container, managing many types of containers, transporting them, etc. This results in an increase in the cost of the developing solution. Further, since the period from the preparation of the developing solution to the use thereof becomes long, there is a problem that the developing solution deteriorates.

Further, the apparatus for adjusting and controlling the concentration by measuring the electric conductivity as described in JP-A-62-27624 is insufficient in accuracy, and is required as the semiconductor is highly integrated. It is difficult to meet the accuracy of.
An object of the present invention is to provide a developing solution diluter that automatically manages a positive type resist developing solution with extremely high accuracy so that it can be prepared to a desired concentration on the side of use such as a semiconductor factory. Especially.

[0007]

Means for Solving the Problems As a result of earnest studies on the automatic diluting device for a developing solution having the above-mentioned problems, the inventors of the present invention measured the amount of the developing solution and the diluting water using a load cell in a mixing tank and measured the potential difference. The inventors have found that the concentration of the developing solution can be automatically controlled with extremely high accuracy by measuring the concentration of the developing solution with an automatic titrator and controlling it with a sequence controller, and arrived at the present invention.

That is, the present invention is provided with a load cell for measuring the weight of the liquid amount in the mixing tank and an automatic titration device by potentiometric measurement when diluting the developing stock solution of the positive type resist with ultrapure water, which is controlled by a sequence controller. This is an automatic diluting device for a developing solution.

As the developing solution for the positive type resist, an inorganic alkaline aqueous solution composed of a mixture of sodium phosphate, caustic soda, sodium silicate, or other inorganic alkali, etc. is used, but when alkali metal contamination is concerned. Is an amine-based organic alkali aqueous solution containing no metal. Tetramethyammonium hydroxide (hereinafter referred to as TMAH) is a widely used developer for such an amine-based positive resist.

In the present invention, a load cell is used to measure the liquid amount in the mixing tank. The load cell is generally used to extract and control the fluctuation of weight as a signal to some differential pressure detection ends (Dp cells). Normally, the Dp cells are used at four places to quickly absorb the unbalanced load. Is used.
In the present invention, by measuring the weight of the mixing tank using this load cell, it is possible to accurately and quickly measure the amount of the developing stock solution and the dilution water introduced into the mixing tank, and it is possible to suitably control and manage the diluting device. ..

Further, in the present invention, the concentration of the developing solution is determined by an automatic titrator by measuring the potential difference. The automatic titrator is equipped with a potentiometric titration unit for concentration measurement, a pretreatment unit for automatic sample collection, and a post-treatment unit for washing and waste liquid treatment. For the concentration measurement, after introducing the sample into the sample collecting tube and sufficiently replacing the sample, a fixed amount of the sample is transferred to a titration bottle, and automatic titration by potentiometric measurement is performed. After the titration is completed, the liquid is discharged and washed, one analysis is completed, and the measured concentration value is transmitted to the sequence controller. In order to measure the concentration of the developer with high accuracy, it is necessary to eliminate the influence of outside air as much as possible. For this reason, the sampler (sampler) of the automatic titrator was placed in a thermostatic chamber and the set temperature was adjusted to 0.0
It is necessary to control the temperature within 1 ° C, and it is necessary to seal the mixing tank and the raw material tank with a dry inert gas.

As the sequence controller used in the present invention, a small computer is usually used, and an amount determined by the concentration set value is sent to the mixing tank to store each liquid amount and the concentration measurement value. The amount of stock solution to be replenished and the amount of diluting water to be replenished are calculated based on the above data, and the controller operates the control valve. It is desirable to install a micro control valve separately for the operation of these liquid amounts to be replenished.
In addition, each control valve, pump,
Each operation performed by the titration device or the like is set to be automatically performed by a timer, and therefore, in the automatic diluting device of the present invention, by inputting the concentration and production amount of the target developing solution to the sequence controller. The desired highly accurate concentration of the developing solution is automatically obtained.

Next, the present invention will be described with reference to the drawings. Figure 1
Shows an example of a system diagram of a developer diluter according to the present invention. The diluting device of the present invention includes, in addition to the mixing tank 3 having the above load cell and the automatic titration device 12, a raw material tank 1 for storing a developing stock solution, a developing stock solution transfer pump 2, a circulating pump 10 for the mixing tank, and control valves. It is composed of a sequence control unit 9 for controlling them, piping for connecting each device, electric instrumentation and the like.

To prepare the developing solution, first, the developing stock solution is sent from the developing stock solution tank 1 to the preparing tank 3 using the transfer pump 2, and when the predetermined amount is reached, the transfer pump 2 is stopped. The transfer amount of the developing solution is controlled by the control valve 4 and the control valve 5. Next, ultrapure water is sent to the mixing tank 3 through the pipe 6. The amount of ultrapure water is controlled by the control valve 7, and closes when the set amount is reached. The amount of each liquid sent to the mixing tank is measured by the load cell 8, and each control valve and pump are quickly and accurately controlled through the sequence controller 9.

After the developing stock solution and the ultrapure water have been sent to the mixing tank, the liquid in the mixing tank is mixed for a certain period of time while the amount of circulating liquid is controlled by the control valve 11 using the circulation pump 10. Next, a part of the mixed solution is sent to the automatic titrator 12, and the concentration of the mixed solution is measured. For this concentration measurement, a highly accurate measurement value can be obtained by using an automatic titrator by potentiometric measurement.

In addition to the control valves 5 and 7, minute control valves 13 and 14 are provided for controlling the feed rates of the developing stock solution and the ultrapure water. The concentration of the mixed solution is compared with a target set value, and when it is lower than the set value, the sequence controller 9 controls the micro control valve 13 to feed the additional amount of the developing stock solution obtained from the measurement result. Further, when the concentration of the mixed solution exceeds the set value, the minute amount control valve 14 is controlled to feed the additional amount of ultrapure water obtained from the measurement result.

In the sequence controller 9,
The operation of each pump is stopped according to the set time,
Each liquid amount and concentration measurement value sent to the mixing tank are stored, the amount of liquid to be added is calculated based on these data, and each micro-control valve is operated. Further, in the sequence controller 9, a series of operations of each device, pump, and control valve are automatically operated by a timer to obtain a developing solution having a target concentration.

After it is confirmed that the concentration of the developer in the mixing tank is within a predetermined concentration standard range in consideration of the measurement accuracy,
The developer is withdrawn as a product from the mixing tank using the control valve 15, and is sent to the product tank through the pipe 16. As mentioned above, when the alkaline developer for photoresist is contacted with the outside air, it is affected by the reaction with oxygen and carbon dioxide in the air and the absorption of moisture, so the developing solution tank, blending tank and product tank are all dried. Sealing with the inert gas is performed.

[0019]

EXAMPLES Using blending tank of the undiluted developer solution tank and 5 m ³ of 3m ³ in FIG. 1, TMA as a developing stock Po Shi resist
H about 15 wt% to TMAH set concentration 2.380 wt% and
A developer of 3.000% by weight was produced. The product concentration in the operation of each of the 5 batches is as shown in Table 1, and the error range of the TMAH concentration was within 0.002% by weight.

Table 1 Setting value (wt%) 2.380 3.000 ────────────────────────── Product concentration (wt%) 1 batch 2.3811 3.0020 2 Batch 2.3814 3.0013 3 Batch 2.3786 3.0006 4 Batch 2.3791 2.9989 5 Batch 2.3817 3.0019 ───────────────────────────

[0021]

In the developer diluting apparatus of the present invention, the error range of TMAH concentration can be controlled with high accuracy within 0.002% by weight as shown in the examples. The developer diluting device of the present invention automatically measures the amount of liquid in the blending tank by the load cell, uses an automatic titration device, and the operation of each device and control valve etc. is performed by the sequence controller,
A developer having a desired concentration can be obtained with high accuracy with almost no human labor. As a result, it is possible to quickly obtain the developer of the desired concentration on the side of the developer using the developer, which reduces the cost of filling the container, transportation and management, and high accuracy. Since the developing solution having the concentration of 10 is easily obtained, the resist pattern can be developed with higher accuracy than the conventional one.

[0022]

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a system diagram of a developer diluter according to the present invention.

[Explanation of symbols]

 1 Development stock solution tank 2 Transfer pump 3 Mixing tank 8 Load cell 9 Sequence controller 10 Circulation pump 12 Automatic titrator

Claims (1)

[Claims] 1. When a stock solution of positive resist is diluted with ultrapure water, it is equipped with a load cell for measuring the weight of the amount of solution in a preparation tank and an automatic titration device by potentiometric measurement, which is controlled by a sequence controller. Automatic developer diluter