JPH0862852A - Device for diluting concentrated developer - Google Patents

Abstract

PURPOSE: To precisely and rapidly produce a developer of desired concn. even by a user's side only if it is possible to get a concd. alkaline developer for a photoresist and further to prevent the concn. being changed due to the absorp tion of the carbon dioxide in the air during dilution or the storage of the dil. developer. CONSTITUTION: A concd. alkaline developer for a photoresist and pure water are introduced into an agitated tank 18 and forcedly agitated to obtain a liq. mixture. A part of the liq. mixture is sampled, the conductivity is measured by a conductometer 20, and the supply of the concd. developer or pure water is adjusted based on the measured result to prepare a developer of desired concn. which is sent to a developer tank 22. Besides, the agitated tank 18 and developer tank 22 are sealed with gaseous nitrogen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diluting a developing stock solution 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 semiconductor manufacturing, photo-etching is repeated in various steps and a positive resist is often used. It is said that the developer for positive resist is as important as the resist as a decisive factor for obtaining high resolution and accurate dimensional accuracy of the resist. As a positive resist developer material, sodium phosphate, caustic soda, sodium silicate,
Alternatively, an inorganic alkaline aqueous solution composed of a mixture with other inorganic alkalis, an amine-based organic alkaline aqueous solution containing no metal or tetramethylammonium hydroxide (T
MAH) aqueous solution, trimethylmonoethanolammonium hydroxide (choline) aqueous solution and the like are used. These developers are matched to the positive resist used,
Its composition and concentration must be strictly controlled in order to obtain the highest resolution, image sharpness and stability.

In particular, with the recent high integration of semiconductors, it is required to make the pattern width finer, and it is strongly desired to improve the accuracy of the developer concentration in order to reduce the variation in the effective sensitivity of the photoresist.

[0004]

However, conventionally, it is not only the equipment and the operating cost that the developer is used after adjusting the composition and the concentration in the semiconductor manufacturing plant, but also the composition and the concentration are sufficiently controlled. The reality is that it is not done at all because there is a fundamental problem that it is extremely difficult to do.

Therefore, on the use side (hereinafter referred to as the "use side") of a semiconductor manufacturing plant or the like, the developer whose composition and concentration are adjusted must be used exclusively by the developer manufacturer (hereinafter referred to as the "supply side"). It was On the supply side, a developing stock solution having a predetermined composition is diluted with pure water, and the developing solution adjusted to a desired concentration is filled in a container and supplied to the use side. The dilution ratio of the stock solution for development naturally varies depending on the solution composition, the stock solution concentration, the type of positive resist, and the purpose of use,
Usually, it is about 5 to 10 times. Therefore, the amount of the developer adjusted on the supply side is significantly increased in accordance with the dilution ratio, and the preparation of the container for transporting this developer to the use side, the filling work into the container, and the transportation cost become enormous. As a result, these various expenses account for a considerable proportion of the developer cost.

Further, there is a problem that it takes a certain period of time for transportation and storage before the developing solution prepared on the supply side is used on the using side, and during that time, the developing solution deteriorates. Also,
One of the reasons why the developer was not diluted on the user side, such as in semiconductor factories, because the developer easily absorbs carbon dioxide gas in the air, even if a diluter is installed on the user side, There is a problem that the concentration is changed by absorbing carbon dioxide during the diluting operation or the storage of the diluted developing solution.

The present invention has been made in view of the above circumstances, and solves the above-mentioned problems of the prior art and allows a user to obtain a developing solution having a desired concentration with high accuracy and promptly if only a developing solution is available. Further, it is an object of the present invention to provide a developing solution diluting device which does not change the concentration by absorbing carbon dioxide during the diluting operation or the storage of the diluted developing solution.

[0008]

In order to achieve the above object, the present invention provides a stirring tank for receiving an alkaline developing stock solution for photoresist and pure water and forcibly stirring the solution for a predetermined time, and a mixed solution in the stirring tank. Conductivity measuring means for extracting a part of the conductivity and then returning it to the stirring tank, and either of the developing stock solution or pure water supplied to the mixing means based on the output signal from the conductivity measuring means. It is provided with a control means for controlling the flow rate, a storage tank for receiving and storing the mixed liquid from the stirring tank, and a nitrogen gas sealing means for sealing the stirring tank and the storage tank with nitrogen gas. .

[0009]

According to the present invention, when a developing solution is diluted with pure water to produce a developing solution having a desired concentration, it has been experimentally confirmed that the conductivity and concentration of the diluted solution have a very close relationship. Then, the concentration of the developing solution is adjusted and controlled based on its conductivity. As a result, a developer having a desired concentration can be manufactured accurately and quickly.

Further, since the stirring tank for stirring the stock developing solution and the pure water and the storage tank for storing the diluted developing solution are sealed with nitrogen gas, the air in the head space of the stirring tank and the storage tank is nitrogen gas. Is replaced by. Thus, it is possible to prevent the concentration of the developing solution from being affected during the stirring operation in the stirring tank, and to prevent the concentration from changing while the diluted developing solution is stored in the storage tank.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a system diagram showing an embodiment of the present invention. The apparatus is a stock solution tank 10 for storing a developing solution, an additive tank 12 for storing an additive, a pure water supply pipe 14 for supplying pure water, a line mixer 16, a stirring tank 18, a conductivity meter 20, a manufactured developing solution. Developer tank 22 for storing
It is constituted by pipes connecting these respective devices, electric instrumentation, and nitrogen sealing pipe lines 64, 66 for supplying and sealing nitrogen gas to the stirring tank 18 and the developer tank 22.

The stock developing solution is stored in the stock solution tank 10, and the stock developing solution is replenished from a pipe 26 according to an instruction from the liquid level gauge 24. Similarly, the additive tank 12 is replenished with the necessary additive from the conduit 30 according to the instruction of the liquid level gauge 28. Stock solution tank 1
0, the developing stock solution and the additive in the additive tank 12 are continuously supplied from the pipes 32 and 34 by the pumps 36 and 38, respectively, and merge in the pipe 14 with pure water continuously supplied by the pump 40. . The mixed solution of the undiluted developing solution, additives, and pure water is mixed by the line mixer 16 and then sent to the stirring tank 18. The stirring tank 18 is an outer cylinder 42.
A stirrer 48 having an axial flow propeller 46 is inserted into the central axis of the inner cylinder 44. Therefore, the mixed liquid sent from the line mixer 16 is stirred by the stirrer 48.
Rotation of the inner cylinder 44 downwardly by the action of the axial flow propeller 46, and the mixing blade 50 provided near the lower end of the inner cylinder 44 sufficiently mixes and stirs it. Passing through the above passage in an upward flow, and thereafter forcedly circulated in the stirring tank 18 by the same repetition. A conduit 52 for extracting a part of the mixed liquid and guiding it to the conductivity meter 20 is opened in a passage portion between the outer cylinder and the inner cylinder, and the mixed liquid passing through the conductivity meter 20 is again recycled from the conduit 54. It is returned to the stirring tank 18.

A baffle plate 56 for cutting the edge of the forced circulation action of the mixed solution is provided at a predetermined position of the stirring tank 18, and a pipe line 58 is connected to the baffle plate 56. The mixed liquid in the stirring tank 18 is pumped from the pipe 58 by a pump 60.
It is sent to the developing solution tank 22, once stored in the developing solution tank, and then sent from the pipe line 62 to the use side such as a semiconductor manufacturing process.

When the alkaline developer for positive resist according to the present invention is brought into contact with outside air, it absorbs oxygen or carbon dioxide in the air or reacts with it to deteriorate its properties. Therefore, the stock solution tank 10, the additive tank 12, the stirring tank 1
Nitrogen gas having a pressure of about 100 to 200 mmAq is supplied to the pipe 8 from the pipe 64 to seal the nitrogen gas. Similarly, nitrogen gas is also supplied to the developer tank 22 from the pipe line 66 to seal the nitrogen gas. The nitrogen gas for the developer tank 22 has a pressure of 1 to ² kg / cm ² to provide energy for delivering the developer to the use side, that is, the head pressure of the developer (that is, the pressure of the nitrogen gas and that of the developer). The value obtained by adding the liquid surface head pressure). For this reason, it is not necessary to provide a pump in the conduit 62, and it is possible to prevent the adverse effect of the pulsating supply of the developer by driving the pump. Further, filters 68, 70, 72 are provided in the pipelines connected to the developer tank 22 to prevent fine particles from being mixed into the developer.

Next, the control system of the apparatus of this embodiment will be described. As shown in FIG. 2, the conductivity meter 20 has a flow cell 76 for conductivity measurement arranged in a passage 74 for the mixed liquid, and the mixed liquid in the passage 74 is controlled by a temperature controller 78.
After a constant temperature (for example, 30 ° C. ± 0.1 ° C.) is set by the heating unit 80 controlled by, the conductivity is measured by the flow cell 76. It is known that the conductivity of a solution shows a large value as the temperature of the solution increases, even if the conductivity is the same as shown in FIG. According to the experiments conducted by the present inventor, the same tendency is recognized in the alkaline developer according to the present invention, and the temperature coefficient of conductivity in a practical concentration range (when the solution temperature changes by 1 ° C., the solution It has been found that the change rate of the electric conductivity of is about 2%. Therefore, in the device of the present embodiment, the measurement error due to the temperature fluctuation of the mixed solution and the temperature compensation are minimized by measuring the conductivity after the mixed solution which is the liquid to be measured is set to a constant temperature in advance. did. The output signal from the flow cell 76 is input to the conductivity controller 82.
The conductivity controller 82 performs temperature compensation on the input signal from the flow cell 76 to calculate the conductivity of the mixed solution at the reference temperature, and outputs this value to the recorder 84,
Compare with a preset target value. When the conductivity of the mixed solution is lower than the target value, the flow rate of the developing stock solution pump 36 is increased by a predetermined amount, and conversely, when it is higher, the flow rate of the pump 36 is decreased by a predetermined amount. During this time, since the pure water pump 40 and the additive pump 38 are operated at a constant flow rate, the conductivity of the mixed liquid at the reference temperature is, as shown in FIG. Change within the range. As shown in FIG. 3, there is a perfect correspondence between the conductivity and the concentration of the mixed solution at a constant temperature. Therefore,
By maintaining the conductivity of the mixed liquid constant (target value), the concentration of the mixed liquid can be made constant. The mixed solution having a constant concentration is stored in the developing solution tank 22 and then used as a developing solution.

When the conductivity of the mixed liquid exceeds the upper limit or the lower limit shown in FIG. 4, the conductivity controller 82
A signal is emitted from the alarm and the alarm device 86 is activated. Alarm device 8
The operation of 6 may be configured in a plurality of stages, and various pumps and valves of the piping system may be automatically controlled according to importance. The stirring tank 18 is provided with a liquid level gauge 88, and the set high level,
The liquid level controller 90 operates according to the low liquid level,
The operations of the pure water pump 40, the additive pump 38, and the developing stock solution pump 36 are controlled.

The developer tank 22 is provided with a liquid level gauge 92, and the liquid level controller 94 operates according to the set high and low liquid level levels to control the pump 60 for the mixed solution. In this embodiment, the liquid level control of the stirring tank 18 and the liquid level control of the developer tank 22 are independent as described above.
However, the operation of the apparatus may be smoothed by superposing the liquid level signals of both of them and controlling the operation of each pump.

In the apparatus of the present embodiment described above, if the relationship between the concentration of the developing solution and the conductivity at the reference temperature and the temperature coefficient of the conductivity near the reference temperature are obtained in advance, the developing solution having the desired concentration can be continuously obtained with accuracy. Can be manufactured well. Since a large amount of pure water is required in a semiconductor manufacturing factory or the like which requires a developing solution for positive resist, a pure water manufacturing apparatus is indispensable. Therefore, the pure water for dilution required in the present invention can be obtained relatively easily. As is well known, the conductivity of pure water is extremely small, and the amount of various additives that are added as needed is so small that it can be ignored compared to the amount of developing solution. The relationship of (1) is uniquely determined irrespective of the properties of pure water, the type of additive, and the amount added in practice. Therefore, the concentration of the developer produced by the apparatus of this embodiment is highly reliable. Development stock solution and pure water
First, after being thoroughly mixed by the line mixer 16,
In the process of being forcedly circulated in the stirring tank 18, the uniform mixing action is performed again. Further, the mixed liquid supplied to the stirring tank 18 is sufficiently mixed with the circulation mixed liquid mixture retained while the inner cylinder 44 in the stirring tank is directed downward, and then rises between the inner and outer cylinders. At a position where the mixed liquid rises between the inner and outer cylinders, a part of the mixed liquid is extracted and guided to the conductivity meter 20, so that the mixed liquid from the line mixer 16 is not directly bypassed to the conductivity meter 20. Therefore, the conductivity measurement value is smoothed, and the control by the conductivity adjuster 82 is prevented from becoming an unstable state such as hunting. According to the experiments of the present inventors, the average residence time of the mixed solution in the stirring tank 18 is 5 minutes or more, preferably 10 to 30 minutes. If it is 10 minutes or less, the measured conductivity value tends to be unstable, and as a result, the control system is adversely affected. If it is longer than 30 minutes, the capacity of the stirring tank and the power for forced circulation become excessively large, which causes economical disadvantages.

In this embodiment, since the flow-rate type flow cell 76 is used as the conductivity measuring cell, the detection end of the cell is always washed with the mixed solution which is the solution to be measured, and the cell is used for a long time. Does not cause measurement error. Further, since the conductivity meter 20 preheats the liquid to be measured to a constant temperature, the range of temperature compensation can be small. Therefore, it contributes to simplification of the control system, responsiveness, and reliability.

In the above-mentioned embodiment, the flow rate of the developing solution is controlled by the conductivity controller, but conversely,
The developing stock solution may have a constant flow rate, and the flow rate of pure water may be controlled. Furthermore, the developing stock solution pump is divided into two parts, a metering pump that covers most of the predetermined flow rate and a minute flow rate control pump, and the flow rate based on conductivity is controlled exclusively by the control pump. Good. Also,
In the above-described embodiment, the detected value of the conductivity of the mixed solution is directly used to control the flow rate of the developing stock solution, alarm, record, etc., but not limited to this, the relationship between the concentration and the conductivity is described. It is also possible to store the data as a data in a microcomputer attached to the controller, once convert the conductivity into a concentration, and then control the input / output.

[0021]

According to the present invention, when the alkaline developing stock solution for photoresist is diluted with pure water to produce a developing solution, a conductivity measuring means is provided, and the concentration of the developing solution is based on the conductivity. Since the adjustment and control are performed, a developer having a desired concentration can be manufactured accurately, quickly, and continuously. At this time, since the stirring tank and the storage tank are sealed with nitrogen gas, the accuracy of the concentration of the developing solution can be further improved.

Further, the alkaline developing stock solution absorbs carbon dioxide gas in the air and its concentration is likely to fluctuate. In the case of the present invention, the concentration itself of the developing solution is measured by the conductivity measuring means, Since the control is performed so as to eliminate the deviation between the measured developer concentration and the target concentration, accurate dilution can be performed regardless of the concentration fluctuation of the alkaline developing stock solution. Further, since the stirring tank and the storage tank are sealed with nitrogen gas, it is possible to prevent the concentration of the developing solution from changing during the diluting operation or during the storage of the diluted developing solution.

Therefore, on the side of use, a developer having a desired concentration can be produced at any time in a required amount as long as a developer stock is available.
A significant reduction in developer cost can be achieved. It is needless to say that the present invention can be implemented on the supply side instead of the conventional method to enjoy the above-described operational effects.

[Brief description of drawings]

FIG. 1 is a device system diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the interrelationship of a conductivity meter and a conductivity controller according to the present invention.

FIG. 3 is a graph showing a general relationship between solution concentration and conductivity.

FIG. 4 is an explanatory diagram exemplifying a change with time of conductivity of a mixed liquid according to the present invention.

[Explanation of symbols]

 10 ... Development stock solution 12 ... Additive solution 14 ... Pure water supply piping 16 ... Line mixer 18 ... Stirring tank 20 ... Conductivity meter 22 ... Developer tank 64, 66 ... Nitrogen sealing pipe line 82 ... Conductivity controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimoto Nakagawa 31 Tajiri-cho, Nakahara-ku, Kawasaki-shi, Kanagawa Hirama Rika Institute Co., Ltd. (72) Inventor Osamu Ogawa 5-1 Nihonbashi Kobune-cho, Chuo-ku, Tokyo Nagase Sangyo Co., Ltd. (72) Inventor Mitsuhiko Sano 236 Nakai, Tatsuno-cho, Tatsuno-shi, Hyogo Nagase Kasei Kogyo Co., Ltd. Harima Plant (72) Inventor Nobuo Takashima 1-1-14 Uchikanda, Chiyoda-ku, Tokyo Hijiri Plant Construction Co., Ltd.

Claims (1)

[Claims] 1. A stirring tank for receiving an alkaline developing stock solution for photoresist and pure water and forcibly stirring the solution for a predetermined time, and extracting a part of the mixed solution in the stirring tank and measuring the electric conductivity thereof, and then putting it in the stirring tank. Conductivity measuring means for returning, control means for controlling the flow rate of either the developing stock solution or pure water supplied to the stirring tank based on the output signal from the conductivity measuring means, and the mixed solution from the stirring tank And a nitrogen gas sealing means for sealing the stirring tank and the storage tank with nitrogen gas, and a developing stock solution diluting device.