Fluid handling – Self-proportioning or correlating systems – Mixture condition maintaining or sensing
Patent
1988-08-25
1990-11-06
Nilson, Robert G.
Fluid handling
Self-proportioning or correlating systems
Mixture condition maintaining or sensing
427345, G05D 2402
Patent
active
049677829
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to recovering and reusing, while applying resist composition onto silicon wafers to form thin films thereon, the resist composition scattered from a spinner and no longer usable on the silicon wafer.
More particularly, this invention relates to a process and apparatus for recovering the scattered unused resist composition as mentioned above for reuse.
2. Discussion of the Prior Art
Resist compositions are used in large volumes, for example, in semiconductor industries or in printing industries. For example, resist compositions are used to manufacture integrated circuits, e.g. by the spin-coating technique whereby they are applied, by means of a spinner or the like, to silicon wafers to form thin films. With this technique of coating silicon wafers, however, more than 90% of the resist composition used is scattered without being coated on the silicon wafers, resulting in waste liquid having no use. As a matter of fact, the waste liquid is collected and commissioned to industrial waste disposal workers for disposal.
From the standpoint of efficient utilization of resources, the inventors have made extensive studies on a process and an apparatus for recovering for reuse such resist compositions otherwise disposed of as waste liquid, and succeeded in providing a process for recovering for reuse such resist composition waste liquid as mentioned above as well as an apparatus therefor.
SUMMARY OF THE INVENTION
Thus, the present invention provides a process and an apparatus as mentioned below, which make it possible to recover and reuse resist composition scatters in silicon wafer coating. under a constant temperature (thermostatic) condition; recovery tank; solvent until the resist composition shows a predetermined viscosity; composition has reached the predetermined viscosity; a storage tank; and tank to a coating chamber for reuse in silicon wafer coating.
The present invention also provides an apparatus to be used for the process mentioned above.
The apparatus according to the invention comprises a resist composition recovering tank characterized by being provided with the following means and lines a) - e) :
(a) a means to maintain the tank under a constant temperature condition;
(b) a means to measure the viscosity of the resist composition introduced as waste liquid, i.e. composition scattered from the spinner without being used;
(c) a transmittal means to transmit the result of the measurement by the viscosity measuring means to the opening/closing action of a valve placed in a passage through which to feed solvent replenishments in such a manner that the valve opens when the result of the measurement of the viscosity of the composition is higher than a predetermined viscosity and closes when it has reached the predetermined viscosity;
(d) a line through which to introduce thereinto the resist composition recovered as waste liquid; and
(e) a line through which to discharge therefrom the resist composition with the predetermined viscosity.
BRIEF DESCRIPTION OF THE INVENTION
The process and apparatus according to the present invention will now be illustrated in more detail with reference to the attached drawing.
FIG. 1 in the attached drawing is a schematic representation of the process and apparatus, of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the drawing, 1 is a coating chamber where a resist composition is applied by means of a spinner to a silicon wafer to form its thin films thereon. The resist composition scattered from the spinner without being used on the silicon wafer during application of the resist composition to the wafer in the coating chamber, hereinafter referred to as "waste liquid composition", is collected and introduced into a preliminary recovery tank 2. The waste liquid composition is then led from the preliminary recovery tank 2 into a recovery tank 3. The recovery tank 3 is provided with a means 6 to maintain it under a constant temperature condition and a means 4 to homo
REFERENCES:
patent: 2711750 (1955-06-01), Norcross
patent: 3831616 (1974-08-01), Weyers
patent: 4426877 (1984-01-01), Srivasta
Mori Kiyoto
Saito Tsugio
Shimauchi Shiro
Yamashita Asaaki
Kanto Kagaku Kabushiki Kaisha
Nilson Robert G.
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