Refrigeration – Intermediate fluid container transferring heat to heat... – Flow line connected transfer fluid supply and heat exchanger
Reexamination Certificate
2000-06-01
2002-01-01
Doerrler, William (Department: 3744)
Refrigeration
Intermediate fluid container transferring heat to heat...
Flow line connected transfer fluid supply and heat exchanger
C062S185000
Reexamination Certificate
active
06334331
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a cooling water supply system and more particularly, relates to an uninterrupted water cooling system capable of supplying cooling water to a process machine during a power interruption and a method for using the uninterrupted sub-loop water cooling system.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, various fabrication processes must be conducted in various physical or chemical process machines. A great majority of semiconductor process machines requires a cooling capability such that the temperature of the process chamber can be suitably controlled. These fabrication machines include deposition chambers such as those used in chemical vapor deposition, physical vapor deposition and furnaces for growing silicon oxides.
In a semiconductor fabrication facility, the total cooling capacity of all make-up air units, recirculation air units, air coolers, ventilation units, and central and process utility systems is normally provided by a chilled water system. For instance, the dehumidification operation in a make-up air unit requires a 6° to 10° C. temperature change in order to remove the excess moisture from the air, while the temperature of a cooling coil employed in a recirculation air unit needs to be controlled above the dew point of 9° C. in order to prevent moisture from condensing such that the humidity inside a clean room can be maintained at a constant level. In a usual practice, the cooling water supply is returned or mixed in order to retain a temperature at between 14° and 18° C.
A water chiller can be constructed of a condenser and an evaporator. In most water chillers use in a semiconductor fabrication facility, the chiller is operated by a water-cooled principle supplied by a cooling tower. Inside the cooling tower, a cooling water is sprayed downwardly to meet the uprising outside air drawn in by a fan mounted on top of the cooling tower. A small amount of water evaporates as the water travels through the cooling tower such that, since evaporation of water demands heat, heat is removed from the cooling water to reach the desirable low temperature. In order to keep the system continuously running, the evaporated cooling water must be replaced.
Conventionally, cooling water required for semiconductor fabrication equipment is taken from a chilled water system using a heat exchanger. The primary side of the process cooling water system is connected to a chilled water supply system, while the secondary side is designed as an open system to keep the water pressure in the cooling water return lines as low as possible. For certain process tools such as physical vapor deposition chambers, the low return cooling water pressure is essential for preventing water from leaking into the process chamber. In the open process cooling water system, the recirculating cooling water is returned to a holding tank that is frequently opened to the atmosphere. Level sensors are used in the water holding tank to ensure a supply of deionized water to be added to the tank for compensating water loss due to evaporation.
A conventional cooling water supply system for semiconductor fabrication machines is shown in FIG.
3
and in systems A, B and C in
FIG. 1. A
typical cooling water system is shown as system A in FIG.
1
and in
FIG. 3. A
cooling water supply
10
at a temperature of about 13° C. is first fed into the process equipment
12
through a first conduit
14
and a first shut-off valve
16
. The cooling water supply exits the process equipment
12
through conduit
18
and shut off valve
20
into a cooling water return line
22
.
FIG. 3
further shows that a plurality of shut-off valves
24
are further utilized with one installed to the cooling water inlet of each process machine
12
. As shown in
FIG. 3
, a series of process machines
12
can be connected in series, or in parallel, for intaking cooling water from the same cooling water supply source, and furthermore, outputting cooling water to a factory cooling water return line
22
.
Others have attempted to improve the basic cooling water system by adding either a heat exchanger, or a heat exchanger and a compressor to the cooling water system. This is shown in systems B and C in FIG.
1
. In system B of
FIG. 1
, heat exchanger
26
is added to the cooling water system to further improve the temperature control of the cooling water. However, as shown in
FIG. 2
, System B suffers a significant loss in efficiency, i.e., the efficiency dropped to about 70%. In still another improvement to the basic cooling water system, as shown in System C of FIG.
1
, both a heat exchanger
26
and a compressor
28
are utilized in a dual heat exchanger mode. In this variation, the temperature of the cooling water can be more accurately controlled, again at a significant loss in efficiency, i.e., only 60% as shown in FIG.
2
.
None of the System A, System B or System C is capable of preventing the problem of cooling water lose during an electrical power interruption at a fabrication facility. When a power outage occurs, an emergency power generation system normally starts immediately to supply power. However, even when the emergency back-up power supply system is immediately put in operation, there is still a time delay of between 30 and 60 seconds in most fabrication facilities. During the short duration of time, the electrical motor that pumps cooling water to the process machines stops resulting in a temporary loss of temperature control in the process machine. The stopping of cooling water circulation to the process machine, and the resulting loss of temperature control can result in a serious loss in fabrication yield since most fabrication processes are sensitive to the process temperature.
It is therefore an object of the present invention to provide a water cooling system for semiconductor fabrication machines that does not have the drawbacks or shortcomings of the conventional water cooling systems.
It is another object of the present invention to provide an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine during a temporary power interruption.
It is a further object of the present invention to provide an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine by utilizing a buffer tank for cooling water storage and delivery during the power interruption.
It is another further object of the present invention to provide an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine that can be operated at 95% efficiency while consuming low uninterrupted power.
It is still another object of the present invention to provide an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine by utilizing a buffer tank, a pump means and a battery power back-up system for running the pump.
It is yet another object of the present invention to provide an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine during a power interruption by utilizing a pump means for drawing cooling water from both a cooling water reservoir and a cooling water buffer tank during a power interruption.
It is still another further object of the present invention to provide a method for preventing an interruption of cooling water supply to a process machine that can be carried out by providing a buffer tank that stores a quantity of cooling water for feeding to a process machine during power interruption.
It is yet another further object of the present invention to provide a method for preventing an interruption of cooling water supply to a process machine by operating a pump powered by an uninterrupted battery power back-up system for circulating cooling water stored in a buffer tank.
SUMMARY OF THE INVENTION
In accordance with the present invention, an uninterrupted sub-loop water cooling system for supplying cooling water to a process machine during a power interruption and a method for u
Chen Ming-Chung
Lai Min-Ter
Doerrler William
Taiwan Semiconductor Manufacturing Company Ltd
Tung & Associates
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