Gas separation: processes – With timing of operation
Reexamination Certificate
1999-06-09
2001-02-27
Smith, Duane S. (Department: 1721)
Gas separation: processes
With timing of operation
C095S247000, C095S266000, C096S156000, C096S193000
Reexamination Certificate
active
06193783
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for supplying a process solution, such as resist solution or developing solution to be applied to a semiconductor wafer or an LCD substrate. More particularly, the invention relates to an apparatus and method for supplying a process solution, which are suitable to deaerate the process solution, that is, to remove the dissolved gas from the process solution.
To perform photolithography during the manufacture of a semiconductor device, a process solution such as resist solution or developing solution is applied to a surface of a substrate such as a semiconductor wafer. As the minuteness and the integrated scale of the semiconductor circuit patterns recently become higher, it is demanded that the process solution be applied in highly controlled conditions.
To apply the process solution in highly controlled condition, deaeration of the solution must taken into consideration. The process solution, for example, resist solution, contains dissolved gas such as oxygen, nitrogen, argon, carbon dioxide, and the like. The dissolved gas may turn into bubbles in the resist solution while the solution is flowing through the solution applying tube. In this case, the solution applied to a substrate will form a film having an uneven thickness. Since the solution is applied to the substrate in a small amount of a few milliliters, the bubbles may greatly impair the thickness uniformity of the film, and thus the influence of the bubbles is not regregible.
Further, if the dissolved gas turns into bubbles as the solution flows through the solution applying nozzle, the bubbles will impair the precision of the amount of the solution applying to a substrate. This adversely influences the precision of forming a circuit pattern.
As indicated above, the process solution such as resist solution should be applied in highly controlled conditions to form a semiconductor circuit pattern. It is therefore desired that an apparatus and method be provided that can efficiently remove dissolved gas from a process solution.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing, and its object is to provide an apparatus and method for supplying a process solution, which can accelerate transform of the gas dissolved in the process solution into bubbles, thereafter removing the gas from the process solution, and which can supply the process solution containing no gas.
To attain the object, according to the first aspect of the invention, there is provided a process solution supplying apparatus comprises: a solution source from which a process solution is supplied; a supply pipe having an upstream end and a downstream end and connected at the upstream end to the solution source; a nozzle connected to the downstream end of the supply pipe; a pump provided on the supply pipe, for supplying the process solution from the solution source to the nozzle; an upstream control valve provided on the supply pipe and located between the pump and the solution source; and a deaerating mechanism provided between the pump and the upstream control valve, for removing gases from the process solution.
Since the upstream control valve is provided between the pump and the solution source, a pressure is reduced in that part of the supply pipe which extends between the upstream control valve and the pump, when the upstream control valve is closed and the process solution is drawn from the pump. The pressure reduced (negative pressure) decreases the gas-solubility of the solution in this part of the supply pipe. This accelate the transform of the gas dissolved in the solution into bubbles. The deaerating mechanism therefore can remove the gas from the process solution.
Thus, no gas changes into bubbles in the downstream end of the supply pipe, and the process solution can be applied from the nozzle to a substrate at a constant flow rate. Further, as the process solution applied from the nozzle to the substrate contains no bubbles, the substrate is coated uniformly as desired.
Preferably, the process solution supplying apparatus has a control section which controls timing of opening and closing the upstream control valve and timing of drawing the process solution into the pump. It is also desired that the gas be removed from the process solution while the pump is operating to supply the solution to the nozzle.
It is desirable that the process solution supplying apparatus be a resist solution supplying apparatus which is designed to supply a resist solution to a resist coating apparatus.
Further, the pump may have a solution holding section for drawing and holding a predetermined amount of the process solution. In this case, it is possible to prevent the process solution from dripping from the nozzle while the gas is being removed from the process solution. In the case where the apparatus is used to supply a resist solution, it is desired that the solution holding section hold the resist solution in an amount which the resist coating apparatus applies to a substrate at one time.
Preferably, the process solution supplying apparatus further comprises a downstream control valve provided on the supply pipe and located between the pump and the nozzle. In this case, it is desired that the apparatus have a control section which controls timing of opening and closing the upstream and downstream control valves and timing of drawing the process solution into the pump.
To attain the object described above, according to the second aspect of the invention, there is provided a process solution supplying method for intermittently supplying a process solution by means of a pump, comprises the steps of:
closing a first solution passage provided at an upstream of the pump; drawing the process solution into the pump from the first solution passage, thereby generating a negative pressure in the first solution passage; opening the first solution passage; and discharging the process solution from the pump into a second solution passage provided at a downstream of the pump.
With this method it is possible to deaerate the process solution while the pump is being operated to perform a series of operation steps for drawing the solution in a predetermined amount and discharging the solution. Further, the solution can be effectively prevented from dripping while gas is being removed from the solution.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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Fujimoto Akihiro
Hasegawa Izumi
Ishizaka Nobukazu
Sakamoto Kazuo
Fulbright & Jaworski L.L.P.
Smith Duane S.
Tokyo Electron Limited
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