Cleaning and liquid contact with solids – Processes – With work or work parts movable during treatment
Reexamination Certificate
2001-01-23
2001-12-04
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
With work or work parts movable during treatment
C134S042000, C134S902000
Reexamination Certificate
active
06325865
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for drying a substrate such as a semiconductor wafer and a liquid crystal display glass after the substrate has been cleaned.
FIG. 28
illustrates one example of a drying process known in the art. This known process is called the “direct displacement isopropyl alcohol (IPA) drying process”, also known as the “Marangoni drying process”. A rinsing bath
92
is closed by a lid
91
and filled with pure water
93
. After a semiconductor wafer W (hereinafter, simply referred to as a “wafer”) has been cleaned by a chemical agent, it is immersed in the pure water
93
for rinsing purposes. A gas mixture of isopropyl alcohol vapor and nitrogen is then fed to the upper interior space of the rinsing bath
92
through gas inlet and outlet ports
95
a
and
95
b
to fill the upper interior space with the mixture.
Thereafter, a holder
94
on which the wafer W is placed is raised toward the upper interior space of the rinsing bath
92
as shown by phantom line in FIG.
28
. when the wafer W upwardly passes past the level of the pure water, isopropyl alcohol is attached to the surface of the wafer W. A change in the surface tension of water due to concentration gradient of isopropyl alcohol causes a film of water attached to the surface of the wafer to be forced back to the pure water. This enables the surface of the wafer to be quickly dried out. In this example, the holder
94
is raised within the rinsing bath. Alternatively, the pure water
93
may be withdrawn from the rinsing bath
92
whereas the holder
94
is fixed in place.
FIG. 29
illustrates another example of a drying process known in the art. In this example, the holder
94
is fixed in place. A gas mixture of isopropyl alcohol vapor and nitrogen is fed to the upper interior space of the rinsing bath
92
through the gas inlet and outlet ports
95
a
and
95
b.
The gas pressure causes the pure water
93
to be displaced from the rinsing bath
92
through a drain valve
96
. After the pure water
93
has been withdrawn, heated nitrogen is fed to the rinsing bath through second gas inlet and outlet ports
97
a
and
97
b
to thermally dry out the surface of the wafer. In this example, the pure water
93
is withdrawn. The holder
94
may alternatively be lifted.
FIG. 30
illustrates a further example of a drying process known in the art. This known process is called the “hot water drying process”. The pure water
93
within the rinsing bath
92
is heated to a predetermined temperature. The wafer W is immersed in the resulting hot water after it has been cleaned by a chemical agent. After the wafer has been rinsed, the holder
94
on which the wafer W is placed is raised to a position shown by phantom line in FIG.
30
. The wafer is then dried by air or hot air. In this example, the holder
94
is lifted. The pure water
93
may alternatively be withdrawn from the rinsing bath
92
while the holder
94
may be fixed in place.
All of the known drying processes present the following common problems. As shown in
FIG. 31A
, the holder
94
includes a pair of support arms
94
a.
A plurality of Y-shaped wafer holding grooves
94
b
are formed in the upper ends of the support arms
94
a.
The wafer W is inserted into the grooves
94
b
whereby the wafer W is held in a vertical orientation. As shown, on an enlarged scale, in
FIG. 32
, the wafer W is constantly in contact with a portion of the wafer holding groove
94
b.
As shown in
FIG. 32
, a water droplet
98
remains between the wafer W and the groove
94
b
when the wafer W is moved out of the pure water, or the pure water is withdrawn from the rinsing bath.
In such a case, a certain period of time is required to dry out the water droplet
98
. This results in an increase in the time required to complete the drying process and brings about a reduction in the throughput of the apparatus. Moreover, watermarks are left on the surface of the wafer due to foreign substance contained within the water droplet while the water droplet
98
is being dried. Such watermarks may cause the wafer to malfunction.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and apparatus for drying a substrate such as a semiconductor wafer, a liquid crystal display glass and the like, which prevent water droplets from remaining between the substrate and a holder on which the substrate is held when the substrate is rinsed by pure water or a similar rinsing liquid.
According to one aspect of the present invention, there is provided a method for drying a substrate by displacing the substrate relative to a rinsing liquid after the substrate is rinsed in a rinsing bath in which the rinsing liquid is contained. The method comprises the steps of: providing a first holder vertically movably arranged in the rinsing bath and including at least one substrate holding groove, and a second holder vertically movably arranged in the rinsing bath below the first holder and including at least one substrate holding groove; substantially vertically holding the substrate solely by the second holder, with the substrate engaged with the substrate holding groove of the second holder, when a level of the rinsing liquid passes past the substrate holding groove of the first holder; and after the level of the rinsing liquid has passed the substrate holding groove of the first holder, raising the first holder to bring the substrate holding groove thereof into engagement with the substrate and lowering the second holder to disengage the substrate holding groove of the second holder from the substrate, to thereby substantially vertically hold the substrate solely by the first holder, with the substrate engaged with the substrate holding groove of the first holder, when the level of the rinsing liquid downwardly passes past the substrate holding groove of the second holder.
According to the method of the present invention, the substrate is maintained out of contact with each of the holders when the level of the rinsing liquid passes past the substrate holding groove of a corresponding one of the holders. This prevents water droplets from being left between the holder and the substrate.
In a preferred embodiment, after the level of the rinsing liquid has passed past the substrate holding groove of the first holder, the substrate holding groove of the first holder is dried and then brought into contact with the substrate.
In a preferred embodiment, when the level of the rinsing liquid passes a lower end of the substrate, the lower end of the substrate is kept in contact with a triangular edged member to make a portion of the rinsing liquid remaining on the lower end of the substrate flow away therefrom.
According to another aspect of the present invention, there is provided an apparatus for drying a substrate by displacing the substrate relative to a rinsing liquid after the substrate is rinsed in a rinsing bath in which the rinsing liquid is contained. The apparatus comprises a first holder arranged in the rinsing bath to hold the substrate in a substantially vertical orientation and including at least one substrate holding groove with which the substrate is engageable, a second holder arranged in the rinsing bath below the first holder so as to hold the substrate in a substantially vertical orientation and including at least one substrate holding groove with which the substrate is engageable, and a holder lifting mechanism arranged to substantially vertically move the first holder and the second holder. The holder lifting mechanism is operable to substantially vertically move the first holder and the second holder, so that the substrate is held solely by the second holder when a level of the rinsing liquid downwardly passes past the substrate holding groove of the first holder, and the substrate is held solely by the first holder when the level of the rinsing liquid downwardly passes past the substrate holding groove of the second holder.
According to the apparatus of the present invention, the substrat
Kurauchi Hiromitsu
Ohsawa Tadayasu
Chaudhry Saeed
Gulakowski Randy
Kaijo Corporation
Lerner David Littenberg Krumholz & Mentlik LLP
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