Fluid handling – Processes – With control of flow by a condition or characteristic of a...
Reexamination Certificate
1999-10-06
2001-07-17
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Processes
With control of flow by a condition or characteristic of a...
C137S113000, C137S599030, C137S599090
Reexamination Certificate
active
06260568
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for supplying a process gas to a semiconductor process equipment and more particularly, relates to an apparatus and a method for supplying uninterrupted process gas to a semiconductor process by using an automatic switching gas supply system to automatically switching a gas supply from a main gas supply source to at least one auxiliary gas supply source.
BACKGROUND OF THE INVENTION
In the semiconductor process industry, a large variety of different ultrapure gases are used in the fabrication plants. These gases include bulk gases such as N
2
, O
2
, H
2
and Ar which are normally used in very large quantities, and specialty gases such as He, A
s
H
3
, PH
3
, SiH
4
, NH
3
and NF
3
which are used only in small quantities. In general, the bulk gases are used for purging of chambers, oxidation and cleaning of wafers, while the specialty gases are used as reactant or etching gases.
The bulk gases are normally stored in large storage facilities, for instance, N
2
can be supplied from a liquified-nitrogen storage tank located in the gas yard or delivered from a pipeline from a remote air-separation plant; O
2
and Ar can be supplied from liquified gas storage tanks; while H
2
can be delivered from either a liquified-gas storage tank or a bank of high-pressure gas cylinders. The bulk gases are normally passed through purifiers and gas filters for removing impurities and contaminating particles before allowed to enter a gas-distribution piping system installed inside a cleanroom. On the other hand, the speciality gases are normally stored in small quantities in gas cylinders and are sent directly to the process tools from cylinders stored inside gas cabinets in the cleanroom. The gas cabinets are exhausted safety enclosures that contain the gas cylinders and the necessary gas handling equipment. The gas cabinets serves a major function of allowing purging and safe exchange of the speciality gas cylinders. The gas handling equipment, which includes gas panels incorporating all components for the control and monitoring of high purity gases. In most semiconductor fabrication facilities, the gas cabinet contains at least two process cylinders to allow easy switch-over when one cylinder is empty. In addition, another cylinder of inert gas such as nitrogen is provided for purging the piping line.
In most fabrication processes, the supply pressure for the bulk and the speciality gases is kept at under 10 Kg/cm
2
. A few exceptions exist such as chlorine and dichlorosilane. At each point of use, the pressure of the bulk or speciality gas has to be independently and locally controlled by a series of flow control valves, pressure regulators, pressure sensors and particle filters located inside a gas manifold box. The precise pressure required for each bulk or speciality gases to be delivered to a specific process tool is determined by the process requirement. In most semiconductor cleanroom facility, one or more gas manifold boxes are installed nearby to each process tool to facilitate gas distribution and control.
A typical bulk gas distribution system
10
is shown in FIG.
1
. The gas distribution system
10
is used, for instance, to distribute an inert gas such as helium. The system
10
consists essentially of two gas supply sources, i.e., a main gas supply source
12
which is a trailer mounted gas source and a back-up gas supply source
14
which is a plurality of gas cylinders with their outlets
16
parallelly connected. The gas from the main gas supply source
12
is fed to a three-way flow control valve
18
through conduit
22
. The conduit
22
further includes flow control valves, pressure regulators, pressure sensors and particle filters which are not shown for simplicity reasons. The back-up gas supply source
14
is also connected to the three-way flow control valve
18
through conduit
24
for feeding a gas to the process tool
20
through the three-way flow control valve
18
when the valve is manually switched over upon an indication that the pressure of the main gas supply source
12
has dropped to a level that requires replacement. The conduit
24
further includes flow control valves, pressure sensors, pressure regulators and particle filters which are not shown.
In the conventional gas supply system
10
shown in
FIG. 1
, the system functions properly as long as it is tended by a system operator to effectuate the manual switching of the three-way control valve
18
when necessary. The effective operation of the gas supply system
10
is entirely dependent on the attentiveness of the system operator and thus, even when elaborate warning devices are installed on the system control panel, it is possible that human error can lead to severe consequences when a gas is fed to the process tool
30
at insufficient pressure or no gas is fed to the process tool
30
. As a result, a significant loss in the fabrication yield occurs.
It is therefore an object of the present invention to provide an apparatus for supplying an uninterrupted gas to a process tool that does not have the drawbacks or shortcomings of the conventional apparatus.
It is another object of the present invention to provide an apparatus for the automatic switching of a gas supply that can not be affected by human errors made by a system operator.
It is a further object of the present invention to provide an apparatus of an automatic switching gas supply system that includes a main gas supply source and at least one auxiliary gas supply source.
It is another further object of the present invention to provide an apparatus of an automatic switching gas supply system wherein the automatic switching function is accomplished by pneumatic power and functions without electric power supply.
It is still another object of the present invention to provide an apparatus of an automatic switching gas supply system consisting of a main gas supply source and a back-up gas supply source with a pressure differential of at least 0.5 Kg/cm
2
between the two gas supply sources.
It is yet another object of the present invention to provide an apparatus of an automatic switching gas supply system in which a gas supply conduit switches automatically to a back-up gas supply source when the pressure of the main gas supply source drops below the pressure of the back-up gas supply source.
It is still another further object of the present invention to provide a method for automatic switching to a back-up gas supply in a gas supply system by providing a main gas supply source and at least one back-up gas supply source wherein a gas flow is controlled by a pressure differential between the two sources and by a three-way flow control valve.
It is yet another further object of the present invention to provide a method for automatic switching to a back-up gas supply in a gas supply system by flowing a gas through a conduit from the back-up gas supply source into a process tool when a pressure in the main gas supply source drops by at least 1 Kg/cm
2
lower than the pressure in the back-up gas supply source.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and a method for supplying an uninterrupted gas by an automatic switching gas supply system are provided.
In a preferred embodiment, an automatic switching gas supply system is provided which includes a main gas supply source, at least one auxiliary gas supply source, a main gas supply conduit connecting in fluid communication at a first end with the main gas supply source and at a second end with a process machine, the main gas supply conduit further includes a first pressure regulator connected in line for allowing a gas having a first pressure to pass, and at least one auxiliary gas supply conduit in fluid communication at a first end with the at least one auxiliary gas supply source and at a second end with the process machine and the main gas supply conduit in a parallel manner, the at least one auxiliary gas supply conduit includes at least one second pressure re
Hsu Ming-Tzung
Tsai Long-Chun
Yang Biing-Huang
Hepperle Stephen M.
Taiwan Semiconductor Manufacturing Company Ltd
Tung & Associates
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