Pre-wet system for a filter

The present invention is a prewet system for a filter. The present invention includes a power controller. A first container is used for storing iso-propyl alcohol liquid. An air pump is connected to the first container via a liquid pipe. The air pump is utilized for sucking the iso-propyl alcohol from the first container and driving the iso-propyl alcohol liquid to flow in the prewet system. An impurity filter is connected to the air pump via a liquid pipe, which is useful for filtering out impurities of the iso-propyl alcohol liquid. A second container is connected to the impurity filter for holding a filter. Between the filter and the second container is a pressure detector for detecting the liquid pressure inside the pipe. The prewet system provides a better prewet effect than the conventional one.

FIELD OF THE INVENTION 
The present invention relates to a prewet system, and more particularly to 
a pre-wet system for soaking a filter which is utilized in semiconductor 
equipment. 
DESCRIPTION OF THE PRIOR ART 
The dimensions of the semiconductor devices are scaled down caused by the 
improvement of the integrated circuit technology. Devices and 
interconnections are manufactured on a chip about 2 cm.sup.2 or less in 
area. During the fabrication of semiconductor process, acid such as 
H.sub.2 SO.sub.4 or HF is often utilized to clean wafers. In addition, the 
acid also serves as an etchant in the etching process. For example, 
silicon etches that are nonselective with regard to crystallographic 
orientation are primarily based on HF--HNO.sub.3 --H.sub.2 O mixtures. HF 
in various dilutions in water and often buffered with ammonium fluoride 
which is the standard silicon dioxide wet etchant. Silicon nitride can be 
wet etched with either HF or with hot phosphoric acid. A lot of residues 
of etched layer are generated in the acid solution during the etching 
process. Therefore, a filter is needed to filter out the residues in the 
acid solution after the wet etching process or after the step of cleaning 
wafer. The filter is typically set in a semiconductor equipment. The 
filter has to be dismantled for removing the residues in the filter. After 
the residues are removed, then the filter will be set up in the equipment 
again. A procedure called pre-wet is needed before the filter is setup. 
The filter is made of a kind of polymer called fluorinated resin (PTFE) and 
its surface tension is 18.5 dyne/cm.sup.2, while the surface tension of 
water is about 70 dyne/cm.sup.2. Since the difference of the surface 
tension between the fluorinated resin and the water is too large, the 
water cannot be used as the pre-wet liquid. An iso-propyl alcohol has a 
surface tension about 17 dyne/cm.sup.2. Therefore, the iso-propyl alcohol 
is more suitable than the water as the pre-wet liquid for the fluorinated 
resin filter. 
A filter that is used in semiconductor equipment for filtering out residues 
is illustrated in FIG. 1. An inlet (label 1) and outlet (label 2) are 
connected to an equipment. In practicing this system, acid flows into the 
filter via the inlet 1 and flows out the filter via outlet 2. The residues 
which are generated during the etching process or the step of cleaning 
wafer are filtered out by using the filter. A valve 3 that is set on the 
bottom portion of the filter is used to drain liquid out of the filter. 
The filter has to be pre-wet before it is utilized to filter out the 
residues which are generated in semiconductor process. In the pre-wet 
procedure, first the inlet 1, outlet 2 and the valve 3 are blocked in 
order to prevent liquid from flowing out of the filter. Subsequently, the 
isopropyl alcohol is injected into the filter via an opening 4 until the 
iso-propyl alcohol flows out of the filter via an opening 5 to make sure 
that the filter is filled with the iso-propyl alcohol. Then both the 
opening 4 and the opening 5 are also blocked. In general, the iso-propyl 
alcohol will be drained out of the filter after soaking in it a half day 
or a day long. After the iso-propyl alcohol is drained out of the filter, 
deionized water is subsequently injected into the filter to clean the 
filter by repeating the aforementioned method. In other words, the inlet 
1, outlet 2 and the valve 3 are blocked. Then, the deionized water is 
injected into the filter via the opening 4 until the deionized water flows 
out of the filter via an opening 5. Unfortunately, the method is normally 
operated by hand that is not only complicated but also not effectual, 
further more, the iso-propyl alcohol is directly drained out of the filter 
after the whole procedure, which will waste a lot of the iso-propyl 
alcohol. 
SUMMARY OF THE INVENTION 
A pre-wet system for a filter of semiconductor equipment is disclosed. The 
pre-wet system comprises a first container having an inlet and outlet 
which is used for storing iso-propyl alcohol liquid. The capacity of the 
first container is about 12 liters. The first container includes a first 
valve that is connected near to the inlet of the first container, a second 
valve is set near to the bottom of the first container, and a third valve 
is set near to the top of the first container. An air pump is connected to 
the outlet of the first container via a liquid pipe. The air pump is 
utilized for sucking the iso-propyl alcohol liquid from the first 
container and driving the iso-propyl alcohol liquid to flow in the pre-wet 
system. Filtering means is connected to the air pump via a liquid pipe, 
which is used for filtering out impurities in the iso-propyl alcohol 
liquid. A second container is connected to the filtering means for holding 
a filter, which includes a supporter, a fixer having a rubber belt, a 
bottom valve is set near to the bottom of the second container for 
draining the iso-propyl alcohol out of the second container, a first 
bellows tube is used for injecting the iso-propyl alcohol liquid into the 
filter, a second bellows tube is utilized to drain the iso-propyl alcohol 
liquid away from the filter. The capacity of the second container is about 
40 liters. A pressure detector for maintaining the liquid pressure inside 
the pipe is provided between the filter and the second container. A third 
container is utilized to hold every means of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 2 3a, 3b, 3c show a preferred embodiment of a pre-wet system for a 
filter. The present invention includes a power control panel 10, a first 
container 11, an air pump 12, filtering means 13, a pressure detector 14, 
a second container 15, a first bellows tube 16a, a second bellows tube 
16b, a plurality of liquid pipes 17 and a third container 20. 
The first container 11 having an inlet 110 and outlet 111 is used for 
storing iso-propyl alcohol liquid, and the outlet 111 of the first 
container 11 is utilized to drain the iso-propyl alcohol liquid out of the 
first container 11. A first valve 113 is attached near to the inlet 110 of 
the first container 11 for controlling the passage of the iso-propyl 
alcohol liquid flowing into the first container 11, a second valve 114 is 
set near to the bottom of the first container 11 for the purpose of 
draining the iso-propyl alcohol liquid away from the pre-wet system, and a 
third valve 112 is set near to the top of the first container 11 for 
exhausting the vapor of the iso-propyl alcohol liquid out of the first 
container 11. The capacity of the first container 11 is about 12 liters. 
An air pump 12 is connected to the outlet 111 of the first container 11 via 
a liquid pipe 17. The air pump 12 is utilized for sucking the iso-propyl 
alcohol liquid from the first container 11 and driving the iso-propyl 
alcohol to circulate the whole cycle in the pre-wet system. 
Then a suitable filtering means 13 is connected to the outlet of the air 
pump 12 via a liquid pipe 17a, which is used for filtering out impurities 
of the iso-propyl alcohol liquid. A second container 15 is connected to 
the outlet of the filtering means 13 for holding a filter 18. A supporter 
151 is set in the second container 15 at the bottom of the second 
container 15 for supporting the filter 18, a fixer 152 having a rubber 
belt 153 is set on one of the inner walls of the second container 15 for 
tying the filter 18, a bottom valve 154 is set near to the bottom of the 
second container 15 for draining the isopropyl alcohol liquid away from 
the second container 15, a first bellows tube 16a is through the side wall 
of the second container 15, which is used for injecting the iso-propyl 
alcohol liquid into the filter 18. One end of the first bellows tube 16a 
is connected to the filtering means 13 via a liquid pipe 17b, and the 
other end is connected to the filter 18. A second bellows tube 16b is 
utilized to drain the iso-propyl alcohol liquid out of the filter 18. The 
second bellows tube 16b passes through the side wall of the second 
container 11. One end of the second bellows tube 16b is utilized to drain 
the iso-propyl alcohol liquid out of the filter 18. The second bellows 
tube 16b passes through the side wall of the second container 11. One end 
of the second bellows tube is also connected to the inlet 110 of the first 
container 15 via liquid pipe, and the other end is connected to the filter 
18. The capacity of the second container is about 40 liters. A pressure 
detector 14 for detecting the liquid pressure inside the pipe 17 is 
provided between the filtering means 13 and the second container 15. A 
third container 20 is utilized to hold every means of the invention, as 
shown in FIG. 3a, FIG. 3b and FIG. 3c. 
FIG. 3a illustrates the second container 15 fixed on one of the inner side 
walls of the third container 20. The power control panel 10 as shown in 
FIG. 3c is attached on the outside of the side wall which is used to fix 
the second container 15. The first container 11 is located in the front of 
the second container 15, the air pump 12 is normally set under the first 
container 11 and the filtering means 13 is usually set near the air pump 
12. 
In practicing this system, when the power of the system is turned on, the 
SUS air pump 12 starts to suck the iso-propyl alcohol from the first 
container 11. Initially, the pressure detector 14 shows a higher pressure 
caused by a large resistance of the filter 18, and the pressure will 
gradually decrease after several circles. The pre-wet procedure of the 
system is completed when the pressure decreases; typically it needs 30--60 
minutes to operate the system. In addition, if the temperature is higher 
than 80.degree. C., the iso-propyl alcohol will spontaneously combust. 
Therefore, the power controller 10 must have an air purge to prevent the 
vapor of iso-propyl alcohol from diffusing into itself. And under the 
safety consideration of the system operation, the air pump of the present 
invention is a heat-free air pump. 
As is understood by a person skilled in the art, the foregoing preferred 
embodiment of the present invention is illustrative of the present 
invention rather than limiting of the present invention. It is intended to 
cover various modifications and similar arrangements included within the 
spirit and scope of the appended claims, the scope of which should be 
accorded the broadest interpretation so as to encompass all such 
modifications and similar structure.