Cleaning and liquid contact with solids – Apparatus – Having self cleaning means
Reexamination Certificate
2001-11-27
2004-10-05
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
Having self cleaning means
C134S113000
Reexamination Certificate
active
06799590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor fabrication equipment. More particularly, the invention relates to a device and method for preventing errors in a sensing operation during a wafer cleaning process.
2. Description of Related Art
A wet clean station supplies N
2
gas and pure water (DI) to wafers to remove wafer impurities such as polymer particles. Wafers are cleaned in a pure water bath (DI Water Bath) of the wet station. A quartz wet station (Quartz DI Water Bath) includes an optical fiber sensor attached to the outside of the pure water bath. The optical fiber sensor detects whether a wafer is present in the pure water bath.
FIG. 1
is a cross sectional view of a conventional wet clean station having optical fiber sensors
20
a
,
20
b
disposed on the outside of the pure water bath
10
. Referring to
FIG. 1
, a conventional wet clean station includes a pure water bath
10
. The pure water bath
10
receives a wafer. Pure water is supplied to the pure water bath
10
to clean the wafer. First and second fixing guides
12
a
,
12
b
are disposed at the upper and lower portions of the pure water bath
10
, respectively, to fix an optical fiber sensor thereto. First and second gas supply pipes
14
a
,
14
b
are respectively inserted into the fixing guides
12
a
,
12
b
to supply nitrogen (N
2
) gas to the inner side of the fixing guides
12
a
,
12
b
. First and second gas supply boxes
22
a
,
22
b
supply the N
2
gas through a gas inlet (N
2
Input) to a respective one of the first and second gas supply pipes
14
a
,
14
b
. The gas supply boxes
22
a
,
22
b
discharge the gas from the respective one of the first and second supply pipes
14
a
,
14
b
through a gas outlet (N
2
Output).
The first gas supply pipe
14
a
is provided with first and second O-rings
16
a
,
18
a
around its outer circumference. The second gas supply pipe
14
b
is provided with third and fourth O-rings
16
b
,
18
b
around its outer circumference. The first and second gas supply pipes
14
a
,
14
b
respectively include first and second optical fibers
20
a
,
20
b
. The first through fourth O-rings
16
a
,
18
a
,
16
b
,
18
b
serve to prevent pure water from flowing into the first and second fixing guides
12
a
,
12
b
from the outside. The first through fourth O-rings
16
a
,
18
a
,
16
b
,
18
b
also serve to prevent N
2
gas from being discharged from the first and second fixing guides
12
a
,
12
b
. The first and second O-rings
16
a
,
18
a
, and the third and fourth O-rings
16
b
,
18
b
further serve to secure the first and second gas supply pipes
14
a
,
14
b
into the first and second fixing guides
12
a
,
12
b
, respectively.
The pure water bath
10
of the wet station is supplied with pure water having a temperature of approximately 70° C. After cleaning the wafer, the waste water is then discharged, and a robot transfers the wafers from the pure water bath
10
to the next pure water bath. When the wafers are transferred to the next pure water bath of the wet station, the first and second optical fibers
20
a
,
20
b
detect whether a wafer is present in the pure water bath
10
. During normal operation, the first fiber
20
a
emits light and the second fiber
20
b
receives the emitted light when no wafers are present.
Unfortunately, the temperature difference between the pure water (approximately 70° C.) and the outside room temperature (approximately 25° C.) results in dew forming on the outside surface of the pure water bath
10
. Dew also forms inside the first and second fixing guides
12
a
,
12
b
. The presence of dew in the fixing guides
12
a
,
12
b
prevents the optical sensors
20
a
,
20
b
from transmitting and receiving light therethrough. This can result in errors in equipment operation because the system may operate as if wafers are present in the pure water bath
10
even when no wafers are present. If the first and second sensing fibers
20
a
,
20
b
experience errors in operation, the robot will stop transferring the wafers into the wet station, resulting in the wafers being dried in air. This causes inferior wafer quality.
To prevent operation error, N
2
gas is supplied to the first and second gas supply boxes
22
a
,
22
b
through the N
2
Inputs. Gas from the gas supply boxes
22
a
,
22
b
is supplied to the gas supply pipes
14
a
,
14
b
. Gas pressure (for example, 0.2 to 1 Kgf/m
2
) builds up in the inner side of the first and second fixing guides
12
a
,
12
b
. Dew that is formed on the outside of the pure water bath
10
is discharged through the N
2
Output due to the pressure created by the N
2
gas. In this way, dew formed on the outside of the pure water bath
10
can be removed to prevent sensing errors.
Unfortunately, however, the gas pressure built up in the fixing guides
12
a
,
12
b
may cause the gas supply pipes
14
a
,
14
b
to become separated from the first and second fixing guides
12
a
,
12
b
. It would be desirable to have a device and method that prevented sensing errors. It would further be desirable to have a device and method that prevented unwanted pipe separation while preventing sensing errors.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an error-preventing device that prevents errors in the operation of optical sensor units for semiconductor fabrication equipment.
Another object of the present invention is to provide a method for preventing errors in the operation of the optical fiber sensors of the fabrication equipment.
In order to achieve the foregoing objects, a wet clean station according to a preferred embodiment of the present invention includes a pure water bath for receiving pure water or chemicals to remove particles from a wafer. The pure water bath can be further configured to discharge waste water after removing the particles. Gas supply pipes are provided having optical fiber sensors inserted into the gas supply pipes. Fixing guides are disposed on the outside of the pure water bath to fix the optical fiber sensors thereto. Purge output holes are formed at predetermined locations along the fixing guides.
A method for preventing errors in the operation of fabrication equipment is also provided. The fabrication equipment preferably includes a cleaning station and an optical sensor unit. The cleaning station may be pure water bath. The optical sensor unit can include gas supply pipes, fixing guides, and optical sensors. The method includes discharging excess pressure and/or moisture from the optical sensor unit. This can be done, for instance, by forming purge output holes in the fixing guides to permit the expulsion of excess pressure and moisture therefrom.
REFERENCES:
patent: 4696712 (1987-09-01), Nonaka
patent: 5529638 (1996-06-01), Lutz
patent: 2002/0117188 (2002-08-01), Galburt et al.
Marger & Johnson & McCollom, P.C.
Perrin Joseph L.
Samsung Electronics Co,. Ltd.
Stinson Frankie L.
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