Fluid handling – With leakage or drip collecting
Reexamination Certificate
2000-08-08
2003-02-04
Walton, George L. (Department: 3753)
Fluid handling
With leakage or drip collecting
C137S554000, C137S557000, C137S486000, C137S487500, C073S04050R, C340S605000, C340S606000, C340S608000
Reexamination Certificate
active
06513542
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a liquid supply or drain pipe for a chemical process tank and more particularly, relates to a liquid supply or drain pipe for a chemical process tank that is equipped with a detector for inner leakage of liquid.
BACKGROUND OF THE INVENTION
In the processing of semiconductor devices, a variety of liquid chemicals are used in processes such as cleaning, etching, photolithographic processes etc. These chemical processes are frequently conducted either in a process tank or the liquid chemical is first stored in a reservoir tank and then dispensed. In any event, the liquid chemical must first be transported into a process tank and then drained from the tank. When the chemical process is to be conducted in the process tank, i.e. such as in a wet etch process, the liquid chemical in the tank must also be replaced or replenished after repeated usage, i.e. by draining from the tank through a drain pipe into a waste chemical collection tank.
A conventional liquid chemical process tank equipped with a supply conduit and a drain conduit is shown in FIG.
1
. The liquid chemical process system
10
consists of a process tank
12
, a supply conduit
14
and a drain conduit
16
. The process tank
12
is shown equipped with an optional overflow tank
18
for receiving an overflow of liquid chemical
20
from the process tank
12
. The supply conduit
14
consists of a first supply pipe
22
, a supply valve
24
and a second supply pipe
26
. The supply valve
24
utilized is a normal-closed type which opens only when activated. The drain pipe
16
consists of a drain valve
28
, a first drain pipe
30
and a second drain pipe
32
. The overflow tank
18
is further equipped with a recycling pipe
34
for recycling overflow liquid chemical
20
through pump
36
, the first drain pipe
30
and a filter
38
back into the process tank
12
.
The conventional liquid chemical process system
10
has several operational drawbacks. First, when there is an internal leakage in the supply valve
24
when the valve is supposed to be closed (i.e. in a normal-closed position when not activated), liquid chemical continuously flows into the process tank
12
through the second supply pipe
26
. The terminology of “inner leakage” is used to denote a situation wherein liquid leaks through an internal passageway, i.e. through the supply valve
24
, and therefore cannot be detected by leakage detectors that are frequently mounted outside the process tank
12
for detecting leakage from the tank or from the supply pipes
22
,
26
. The inner leakage through the supply valve
24
, therefore, cannot be detected by this type of leakage detectors. As a result, the inner leakage cannot be detected by machine operators when liquid chemical continuously flows into the process tank
12
, and thus making the concentration of the process chemical out of control. Since most semiconductor processes require an accurate control of the composition of the process chemicals, any deviation from the specified chemical composition renders the process unreliable and the product made by the process out of control.
A typical processing problem caused by out-of-specification chemical concentrations is shown in
FIG. 2
of a chemical wet etch system. The etch rates are plotted against the number of days the etch chemical has been used illustrating a gradual decrease in the etch rates due to a continuous dilution (or decrease in concentration) of the liquid chemical in the process tank.
Similar processing problems can also be caused by the lack of detection of a leakage in the drain conduit
16
, shown in FIG.
1
. When the drain valve
28
, of the normal-closed type, fails to close completely, liquid chemical
20
in the process tank
12
continuously drains away through drain conduit
16
into a waste collection tank (not shown). This causes excessive usage of the liquid chemical. The inner leakage of liquid chemical through the drain valve
28
cannot be detected by conventional leakage detectors that are mounted in the liquid process system
10
.
An example of excessive usage of a liquid chemical is when an inner leakage is not detected as shown in FIG.
3
. When the inner leakage is finally corrected in August, the usage of liquid chemical returns to a normal volume.
SUMMARY OF THE INVENTION
In accordance with the present invention, a liquid supply or drain conduit system that is equipped with an inner leakage detector is provided. In an alternate embodiment, a liquid process tank that is equipped with a liquid supply/drain system capable of detecting an inner leakage is further provided.
In a preferred embodiment, a liquid supply or drain conduit system equipped with an inner leakage detector is provided which includes a first conduit for feeding a liquid into an inlet of a first valve of the normal-closed type, a second conduit of T-shape having a horizontal portion and a vertical portion, the horizontal portion of the second conduit flows the liquid from an outlet of the first valve into a reservoir tank, a second valve of the normal-open type that has an inlet and an outlet, the inlet is situated in relation to the first valve in such a way that it receives through a vertical portion of the second conduit a leaked flow of liquid by gravity when the normal-closed first valve failed to close, and a leakage detector for detecting a flow of liquid through the second valve.
In the liquid supply or drain pipe equipped with a leakage detector, the reservoir tank may be a chemical process tank, or a waste chemical collection tank. The leakage detector may further include a liquid flow meter, or an alarm to be activated when a liquid flows through the second valve. The leakage detector sends a signal to a micro-processor when a flow of liquid through the second valve is detected. The leakage detector further sends a signal to a close-loop control system for closing the first valve when a flow of liquid through the second valve is detected.
The present invention is further directed to a liquid process tank that is equipped with a supply/drain system capable of detecting inner leakage that includes a process tank for receiving a fresh liquid from a second conduit and for draining a used liquid to a third conduit, a first conduit for feeding the fresh liquid into an inlet of a first valve of the normal-closed type, the second conduit is provided in a T-shape that has a horizontal portion and a vertical portion, the horizontal portion flows the fresh liquid from an outlet of the first valve into the process tank, a second valve of the normal-open type that has an inlet and an outlet, the inlet is situated in relation to the first valve in such a way that it receives through the vertical portion of the second conduit a leaked flow of the fresh liquid by gravity when the first valve failed to close, a first leakage detector for detecting a flow of the fresh liquid through the second valve, the third conduit for draining the used liquid from the process tank into an inlet of a third valve, a fourth conduit that is provided in a T-shape that has a horizontal portion and a vertical portion, the horizontal portion receives the used liquid from an outlet of the third valve and delivers the used liquid to a used liquid collection tank, a fourth valve of the normal-closed type that has an inlet and an outlet, the inlet is situated in relation to the third valve in such a way that it receives through the vertical portion of the fourth conduit a leaked flow of the used liquid by gravity when the third valve failed to close, and a second leakage detector for detecting a flow of the used liquid through the fourth valve.
The liquid process tank that is equipped with a supply/drain system capable of detecting inner leakage may further include a micro-processor for receiving a signal from the first and the second leakage detector when a leakage is detected by either one of the detectors. The liquid process tank may further include an alarm system to be activated by a signal received from eith
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
Walton George L.
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