Photoresist dispensing device

Details Photoresist dispensing device Photoresist dispensing device

2000-02-18

2001-12-25

Edwards, Laura (Department: 1734)

Coating apparatus

Control means responsive to a randomly occurring sensed...

Responsive to attribute, absence or presence of work

C118S052000, C118S056000, C118S319000, C118S320000, C222S571000, C239S119000

Reexamination Certificate

active

06332924

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed to a photoresist dispensing device adapted for use in applying a film of photoresist on a silicon wafer in the process of manufacturing semiconductor chips.
DESCRIPTION OF THE PRIOR ART
As is notoriously known in the art, semiconductor chips can be produced through a series of fabrication processes, including a lithography process wherein a photoresist film is applied on a silicon wafer. The photoresist film will then be exposed to a light or beam through a mask to thereby leave a circuit pattern which in turn goes through a selective chemical etching.
It is of paramount importance that the photoresist film be applied with a uniform thickness in the course of lithography process to assure enhanced yield rate of the simiconductor chips. Such a photoresist application process has been carried out by means of a photoresist dispensing device.
Schematically shown in
FIG. 1
is a prior art photoresist dispensing device which makes use of pressurized air as a power source. The prior art photoresist dispensing device includes a storage tank
1
containing liquid photoresist and a bellows pump
2
connected to the storage tank
1
so that, when operated, it can suck up and forcedly transport the photoresist in the storage tank
1
via a supply line. At the downstream side of the bellows pump
2
, there is disposed a filter
3
that serves to remove alien matters possibly existing in the stream of photoresist. A vent valve
3
a
is utilized to discharge air gathered in the filter
3
to the outside.
Provided at the downstream side of the filter
3
is a pneumatic regulator check valve
4
that functions to inhibit any backflow of the photoresist, while regulating the pressure of the photoresist flowing therethrough. The regulator check valve
4
is connected to a nozzle
6
by way of a suck-back valve
5
. The nozzle
6
is adapted to spray the photoresist onto a silicon wafer
10
which remains firmly held by a rotating spin chuck
11
. The suck-back valve
5
is operable to suck back the residual photoresist adhered to the tip end of the nozzle
6
, thus avoiding any unwanted dropping of the residual photoresist on the silicon wafer. All of the bellows pump
2
, the regulator check valve
4
and the suck-back valve
5
are pneumatically operated and associated with an air pressure source(not shown) through an air pressure line
8
and a solenoid valve
9
.
In accordance with the prior art photoresist dispensing device referred to above, there is a tendency that foreign matters are accumulated in the filter
3
with the lapse of operating time, thus resulting in the filter
3
being clogged at least partially. Even though the bellows pump
2
operates under a normal condition, therefore, the pressure of the photoresist at the downstream side of the clogged filter
3
will be dropped sharply, which leads to substantial reduction in the amount of the photoresist to be fed to the regulator check valve
4
. The means that it becomes no longer possible to supply a metered amount of photoresist to the nozzle
6
under a constant pressure, making the thickness of the photoresist film on the wafer irregular and uneven. Mainly because the silicon wafer
10
is caused to rotate by means of the spin chuck
11
, the photoresist film formed on the wafer
10
would suffer what is called “speed boat” in the event that the amount and pressure of the photoresist sprayed is not kept constant.
It might be of course possible for the operator to periodically check the degree of contamination of the filter
3
and replace any heavily contaminated filter with a new one as frequently as possible. This would however result in a decreased manufacturability because the fabrication system has to be stopped each time the filter replacing operation is carried out. As an alternative, it can be taken into account that the amount of the photoresist to be supplied is increased enough to prevent the pressure drop, in which case, the cost of fabricating the semiconductor chips becomes higher due largely to the large-scale use of expensive photoresist.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a photoresist dispensing device which can apply photoresist on a silicon wafer in a metered amount and under a controlled pressure to thereby form a uniform thickness of photoresist film on the wafer.
Another object of the invention is to provide a photoresist dispensing device which has a feeder unit of easy-to-repair, compact structure and operable in such a manner as to accurately control the amount and pressure of the photoresist to be dispensed.
With these objects in view, the instant invention provides a photoresist dispensing device for use in applying a metered amount of photoresist on a wafer comprising, a photoresist storage tank, a nozzle for spraying the photoresist on the wafer, a feeder unit for drawing a metered amount of the photoresist out of the storage tank and discharging the photoresist through the nozzle, a pneumatic control unit for controlling the operation of the feeder unit with the use of pressurized air, and a filter disposed between the storage tank and the feeder unit for removing alien matters present in the photoresist. The feeder unit includes a base having an inlet port leading to the storage tank, an outlet port leading to the nozzle and first through third intermediate passageways interconnecting the inlet and outlet ports, a first cutoff valve mounted on the base at a position between the inlet port and the first intermediate passageway, a diaphragm pump attached to the base at a position between the first and second intermediate passageways, a second cutoff valve secured to the base at a position between the second and third intermediate passageways, and a suck-back valve affixed to the base at a position between the third intermediate passageway and the outlet port.


REFERENCES:
patent: 3895748 (1975-07-01), Klingenberg
patent: 5134962 (1992-08-01), Amada et al.
patent: 5950923 (1999-09-01), Fukano et al.
patent: 5950924 (1999-09-01), Hatakeyama et al.
patent: 6062442 (2000-05-01), Yang et al.

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