JP3141919B2 - Chemical liquid preparation apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for preparing an alkaline developer for use in developing a positive resist in, for example, a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In recent years, the development of the semiconductor industry has been remarkable. Particularly, in recent semiconductor integrated circuits, as represented by a super LSI, a minimum line width for drawing a circuit has been gradually reduced along with high integration. It is desired to form a resist pattern with high accuracy. Positive resists meet this demand, and have higher resolution than conventional negative resists, and are therefore often used for drawing highly integrated circuits.

As a developing solution for the positive resist, an aqueous alkali solution such as tetramethylammonium hydroxide or trimethylmonoethanolammonium hydroxide is generally used. This developer is said to be as important as the resist. That is, in order to obtain image sharpness, excellent resolution and stability, a developing solution having a concentration suitable for the positive resist to be used is required.
In particular, with the recent increase in the degree of integration of semiconductors, the pattern dimensions have been miniaturized, and the submicron era has been entered. In order to reduce the variation in the effective sensitivity of the resist, improvement in the accuracy of the development density has become an issue.

[0004] It is extremely difficult to control the concentration of the developer with high accuracy, and this control cannot be performed by a developer using a developer such as a semiconductor factory.
A developing solution prepared by diluting a developing solution with ultrapure water to a desired concentration is purchased and used. The dilution ratio of the undiluted developing solution varies depending on the concentration of the undiluted solution, the purpose of use, and the like.
It is about 10 to 10 times. As an apparatus for preparing such a developing stock solution, Japanese Patent Application Laid-Open No. 62-27624 proposes an apparatus for adjusting the concentration by measuring the conductivity. Japanese Patent Laid-Open No. 5-
No. 216241 describes an automatic titration analyzer using a load cell and a potential difference measurement, and JP-A-6-61136 describes an automatic diluting device using a load cell and an ultrasonic densitometer.

[0005]

Conventionally, various attempts have been made to obtain a precise mixing accuracy. The main method is to measure the concentration of the preparation tank solution equipped with mixing means, and if the concentration differs from the target value, so-called feedback control that adjusts the supply amount of one or both of the stock solutions depending on the degree. As a general solution supply method, flow control and weight measurement by a load cell have been proposed. However, since the measurement of the undiluted solution supply amount has a steady error and a drift error peculiar to the measuring instrument, a great deal of effort has been devoted to accurately controlling the concentration of the prepared solution. For example, in the batch system, fine blending is performed after coarse blending and concentration analysis are performed. When the density analysis is rejected, it is a general method that fine preparation is performed again and the process is repeated until the density analysis is passed. In such a method, it takes a long time to obtain a high-precision blended product, and therefore, the production capacity is small with respect to the size of the apparatus. Are full and cannot be dispensed, and the processing of the defective product becomes complicated.

For example, in a batch type mixing apparatus for mixing pure water and a chemical, etc., when supplying pure water and a chemical to the mixing apparatus, the raw material supply time is shortened to shorten the mixing time and increase the production capacity. In such a case, it is often necessary to supply a large amount of undiluted solution in a short time, and large-scale supply equipment (for example, a large-sized pure water device) is required. When the liquid is directly supplied from the raw liquid container to the mixing device, the raw liquid may be lost during the supply of the specified amount, and there is a problem that a fully automatic unmanned facility may be unable to cope with the problem. Furthermore, in a batch-type dispenser, it generally takes a long time to mix an undiluted solution in a mixing device, and a titration method or the like requires a considerable amount of time for analysis. There are problems such as the necessity of an apparatus and a large preparation liquid storage tank.

[0007]

The inventor of the present invention has made intensive studies on the above-mentioned problems in preparing a chemical solution, and as a result, has found that a post-mixing device having a mixing means having a considerably larger volume than the mixing device is provided at the latter stage of the mixing device. And further mixing the solution from the mixing device in the post-mixing device can significantly reduce the concentration fluctuations in the post-mixing, so that even if the solution concentration in the mixing device is rejected, remixing in the post-mixing device If it falls within the acceptable range as a whole, re-mixing with the mixing device becomes unnecessary, and the above-mentioned problems (1) and (2) are greatly improved. By installing an undiluted solution intermediate tank having a measuring and controlling means for supplying and discharging a specified amount of undiluted solution, the raw materials for the next mixing can be measured in advance during the mixing operation of the mixing device, so that the adjustment can be performed. It is possible to avoid the situation of interruption due to running out of raw material in the middle, solve the problems of ~, and switch between multiple mixing devices, which is the biggest factor that determines the production capacity in batch mixing The present inventors have found that the problem of greatly increasing the capacity can be solved by doing so, and arrived at the present invention.

That is, the present invention provides: 1) a drug solution preparation device for mixing a plurality of undiluted solutions to obtain a target component at a specified concentration, and a mixing device having means for measuring and supplying the undiluted solution and mixing means;
A concentration meter for measuring the concentration of the target component in the mixed solution, an arithmetic unit for determining the supply amount of the undiluted solution based on the difference between the target concentration of the target component and the measured concentration of the component, and a target component larger than the capacity of the mixing device. A chemical dispensing device having a concentration meter and a liquid level meter for measuring the concentration of the mixture, and a mixing means, and having a mixing device after receiving the mixed solution from the mixing device.2) In a batch type dispensing device, the mixing amount is larger than a single dispensing amount. A drug solution dispensing device having a stock solution intermediate tank having a measuring and controlling means for supplying and discharging an amount of stock solution; and 3) a drug solution dispensing device having a plurality of mixing devices in a batch-type dispensing device.

The stock solution used in the present invention is not particularly limited, and a solution of various chemicals, water or an organic solvent having a purity depending on the use for diluting the same, and the like are used.
For example, when a developing solution is produced from an undiluted developing solution, a developing alkali solution and ultrapure water for diluting it are used. When a developer is manufactured in a semiconductor factory, a method is usually adopted in which a stock solution for development is supplied to the factory by a transport container (canister) and transferred to a stock solution tank by pressurized inert gas.

In the invention of 1), there is provided a post-mixing device provided with a concentration meter for measuring the concentration of the target component, a liquid level meter, and mixing means. By calculating the concentration of the solution in the mixing device so that the solution concentration of the post-mixing device becomes the target concentration from the mixing volume in the mixing device, and controlling the calculated concentration as the target concentration of the mixing device, fluctuations in the concentration of the liquid to be sent are significantly reduced. Can be done. After this, the capacity of the mixing device is greater than the capacity of the mixing device,
It is preferably at least twice the capacity of the mixing device, more preferably at least four times. In this way, by setting the capacity of the post-mixing device several times or more as large as that of the mixing device, it is possible to reduce the fluctuation in the concentration of the liquid sent from the mixing device to a fraction or less.

Therefore, according to the invention of 1), even if the solution concentration of the mixing device is unacceptable, if remixing with the post-mixing device falls within the acceptable range as a whole, re-mixing in the mixing device becomes unnecessary, Thus, the prepared liquid can be obtained in a short time. In this way, the determination that re-mixing becomes unnecessary can be made by performing comprehensive calculations such as the concentration measurement history of the mixing device, the amount of liquid sent, and the stock amount history of the post-mixing device. More accurate calculation is performed by installing a densitometer. That is, a concentration meter is installed in the post-mixing device, and from the target concentration, the amount of the solution in the post-mixing device, the measured value of the solution concentration, and the mixing volume of the mixing device, the solution concentration in the post-mixing device matches the target concentration. By calculating the concentration of the solution in the mixing apparatus and incorporating the calculated concentration into one of the determinants of the target concentration of the mixing apparatus, stable and accurate compounding can be performed over a long period of time. Changing the target concentration of the mixing device based on the calculated concentration is continuously performed at a fraction of the required change amount required by the calculation in order to avoid a sudden change and to reduce the influence of fluctuation due to a measurement error. It is desirable to carry out.

In the invention of 2), in the batch-type dispensing apparatus,
By installing an undiluted solution intermediate tank that has a measuring and controlling means for supplying and discharging a specified amount of undiluted solution that is larger than the amount of one batch, even if the undiluted solution cannot be supplied to the mixing device during the dispensing, The operation of the compounding device can be continued. Also, the supply to the undiluted solution intermediate tank may be completed during the time of the mixing and analysis operation in the mixing device,
There is no need to supply a large amount in a short time, and the equipment for supplying the stock solution to the blending device does not need to be larger than necessary.

A measuring and controlling means for supplying and discharging a specified amount of the undiluted solution to and from the undiluted solution intermediate tank is added to the undiluted solution intermediate tank during the mixing operation and the analysis operation in the undiluted solution intermediate tank during the next operation. Can be supplied to the mixing device in a short time at a necessary timing by accurately supplying in advance. This makes it possible to shorten the overall blending time, and to substantially increase the capacity of mixing devices having the same capacity. It is preferable that the control means for supplying and discharging the undiluted liquid be provided separately for coarse preparation and fine preparation, and according to the invention of 3) to be described later, a batch-type preparation apparatus comprises a plurality of mixing devices. The effect is further exhibited.

There are various means for supplying and measuring the amount of the undiluted solution to the undiluted solution intermediate tank. One or a plurality of liquid detectors (LEDs or the like) are attached to the undiluted solution intermediate tank (including the peripheral piping), and the detector is set in advance. A method of supplying until the specified position is reached from the relationship between the mounting position and the capacity of the liquid, and a continuous liquid level measuring instrument is installed in the raw liquid intermediate tank, and the liquid is supplied until the liquid level reaches the raw liquid volume required for coarse preparation or fine preparation. A method of integrating the supply amount by installing an ultrasonic flow meter, etc., stopping the supply when the specified amount is reached, a method of incorporating a load cell in the stock solution intermediate tank, and supplying the required amount by weight measurement, etc. Is done. In these methods, even if the stock solution runs out during the measurement, the metering can be continued if the stock solution is supplied again. In the supply line of the undiluted liquid intermediate tank, a liquid shortage detector etc. is installed inside the tank, and when the detector detects the liquid shortage while supplying the undiluted liquid to the mixing device, it issues an alarm and completes the ongoing mixing. Later, procedures that do not enter the next formulation will be incorporated.

According to the invention of 3), the use of a plurality of mixing devices in the batch-type mixing device requires the installation of a plurality of mixing devices requiring the longest time, so that each function in the batch-type mixing device is The operating rate can be increased on average, and the mixing capacity can be increased more than the increase rate of the installation area and the equipment price by using a plurality of mixing apparatuses, which is a great advantage. As the mixing means in the mixing device and the post-mixing device of the present invention, a method of installing a stirrer in a tank, a method of installing a circulation pump to mix by circulating the liquid in the tank, and a method of mixing with a line mixer Are not particularly limited. As a densitometer for measuring the concentration of the target component, a conductivity densitometer, an ultrasonic densitometer, a titration analyzer, or the like is used.

The supply amount measuring instrument, the control means, and the concentration meter which influence the mixing accuracy have a steady error, a drift error, a hysteresis error and the like. For this reason, when the mixing error is small, it may be better to not correct the stock solution supply amount, and therefore, a mechanism that does not change the stock solution supply amount or the target concentration within a certain allowable error range. By incorporating, it is possible to improve the mixing efficiency and stabilize the mixing accuracy. For this reason, in the drug solution dilution device of the present invention, a certain range of tolerance is set for the target concentration, and when the measured concentration of the solution of the mixing device or the post-mixing device is within the tolerance range, the supply amount of the undiluted solution or the mixing A method that does not change the device is adopted.

[0017]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples.

Example 1 An alkali developer was prepared without using a stock solution intermediate tank (chemical solution intermediate tank and ultrapure water intermediate tank) in the chemical solution mixing apparatus shown in FIG. An ultrasonic flowmeter is used to measure the flow rate of the undiluted solution (alkaline solution and ultrapure water). The flow rate signal is integrated inside the sequencer, and the supply is stopped when the flow rate reaches a specified amount.
An ultrasonic densitometer was used for measuring the concentration in the mixing tank and the post-mixing tank. The mixing tank and the post-mixing tank are mixed by circulating the liquid in each tank with a pump. The volume of the mixing tank is about 1
50 L, the volume of the post-mixing tank is about 600 L. A sequencer with digital and analog input / output functions is installed for overall arithmetic control, and the undiluted solution is determined based on the difference between the target concentration of the target component and the measured concentration of the component. The calculating function for determining the supply amount, that is, the mixing device solution concentration for the solution concentration in the post-mixing tank to become the target concentration from the measured concentration value of the post-mixing tank solution, the liquid amount, and the mixing volume of the mixing device, is calculated. An arithmetic function that uses the concentration as one of the determinants of the target concentration of the mixing device, and a certain range of allowable error is set for the target concentration. When the measured concentration of the mixing device or the post-mixing tank is within the allowable error range, the undiluted solution is used. Incorporates a function that does not change the feed rate or the mixing device.

In FIG. 1, the concentration of the undiluted alkaline solution is 15% by weight, and the concentration is adjusted with ultrapure water to a target concentration of 2.38% by weight. The allowable fluctuation range of the product is ± 0.0
03% by weight. First, add about 1.38% by weight of the product to about 1
The amount of the alkaline stock solution necessary for producing 00 L was calculated and set, and the amount of ultrapure water was calculated and set so that the concentration of the prepared solution was about 2.6% by weight in the first rough preparation. Based on this setting, the alkaline solution of the stock solution and the ultrapure water are supplied to the mixing tank.
The time from the start of the supply to the stop of the supply by the above-mentioned sequencer required about 15 minutes due to the supply capacity of the ultrapure water apparatus. Mixing is started after the supply of each undiluted solution to the mixing tank, and three minutes after the measured value of the ultrasonic densitometer becomes constant, the amount of ultrapure water required to bring the mixture concentration to 2.38% by weight. Is calculated, and after the ultrapure water is supplied to the mixing tank in the same manner, the mixing for fine preparation is restarted. This supply took less than two minutes. Mixing is stopped 5 minutes after the measured value of the ultrasonic densitometer in the mixing tank becomes constant, and the liquid is sent to the mixing tank. Although the product is always sent from the post-mixing tank to the place of use, this series of operations is performed by the program of the sequencer as long as the post-mixing tank liquid level has room to receive the preparation liquid for one batch. As a result of performing continuous 20 batches in the mixing tank of the above-mentioned chemical solution mixing apparatus, the maximum fluctuation width of the mixing concentration in the mixing tank was 0.005% by weight, which exceeded the allowable fluctuation width twice, but the post-mixing was performed. The maximum value of the difference with respect to the target concentration in the tank was 0.003% by weight, and the fluctuation always fell below the allowable range. Therefore, the supply amount of the stock solution or the target of the mixing device was not changed.

Example 2 In Example 1, a 20 L chemical solution intermediate tank and a 100 L ultrapure water intermediate tank were installed after each ultrasonic flow meter as a stock solution intermediate tank, and the same alkali concentration solution was prepared. The stock solution alkaline solution and ultrapure water are first supplied to each stock solution intermediate tank, and then to the mixing tank. The supply from each stock solution intermediate tank to the mixing tank is performed simultaneously with the completion of the supply from the mixing tank to the post-mixing tank, and immediately after the supply from each stock solution intermediate tank to the mixing tank is completed, the alkali required for the next rough blending is prepared. The supply of the solution is started to the intermediate tank. In other words, mixing is started after the supply of each stock solution to the mixing tank, and three minutes after the measured value of the ultrasonic densitometer becomes constant, the ultrapure water necessary for bringing the mixed solution concentration to 2.38% by weight is obtained. The amount of water is calculated, and the calculated amount of ultrapure water is supplied to the ultrapure water intermediate tank, and then supplied to the mixing tank to start remixing for fine mixing, and at the same time, the amount of ultrapure water required for the next coarse mixing The supply of pure water is started to the intermediate tank. Further, after the measured value of the ultrasonic densitometer of the mixing tank becomes constant, another 5
After a minute, the mixing is stopped and the mixture is sent to the mixing tank. Then, the stock solution (alkaline solution and ultrapure water) of each stock solution intermediate tank, which has been completely weighed for rough mixing, is immediately supplied to the mixing tank. Is done. For comparison with Example 1 in the above apparatus, the same alkali concentration solution was prepared in 20 batches. As a result, the preparation time per batch can be reduced by about 11 minutes, and the production capacity can be improved. Was. At this time, the maximum concentration fluctuation widths of the mixing tank and the post-mixing tank were almost the same as those in Example 1, and no change was made in the supply amount of the stock solution or the target of the mixing apparatus.

[0021]

According to the apparatus of the present invention, by installing a post-mixing device having a mixing means with a considerably larger volume than the mixing device, the time required for preparing a chemical solution is shortened, and there is no defective product. Can be obtained in a short time. In addition, by installing the stock solution intermediate tank of the present invention in a batch-type blending device, the blending time can be shortened and the production capacity can be increased. The situation of interruption due to cutting can be avoided. Further, by switching and using a plurality of mixing devices in the batch mixing method according to the present invention, even if one mixing device fails, the entire stoppage can be avoided, and the capability of the chemical mixing device can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a flowchart of the apparatus of the present invention used in Examples 1 and 2.

Claims (3)

(57) [Claims] 1. A chemical solution preparation device for mixing a plurality of stock solutions to bring a target component into a specified concentration, a mixing device having a means for measuring and supplying the stock solution and a mixing device, wherein the concentration of the target component in the mixed solution is determined. A densitometer for measuring, a computing device for determining the undiluted solution supply amount based on the difference between the target concentration of the target component and the measured concentration of the component, and a densitometer for measuring the concentration of the target component which is larger than the capacity of the mixing device and A chemical liquid preparation device comprising a liquid level meter and mixing means, and a mixing device after receiving the mixed solution from the mixing device. 2. The method according to claim 1, further comprising a plurality of mixing devices.
Chemical solution mixing device. 3. A mixing apparatus having a means for measuring and supplying an undiluted solution, a mixing means, a concentration meter for measuring the concentration of a target component in a mixed solution, and a raw material based on a difference between a target concentration of the target component and the measured concentration of the component. A chemical solution dispensing device having a calculating device for determining the supply amount, a concentration meter larger than the capacity of the mixing device, a level meter for measuring the concentration of the target component, a level gauge, and mixing means, and a mixing device for receiving the mixed solution from the mixing device. In the apparatus, a mixing apparatus solution concentration for the solution concentration of the post-mixing apparatus to be the target concentration is calculated from the measured concentration value of the post-mixing apparatus solution, the liquid amount, and the mixing volume of the mixing apparatus, and the calculated concentration is set to the target of the mixing apparatus. A method for preparing a drug solution, wherein the method is one of the determining factors of the concentration.