Fluid handling – With indicator – register – recorder – alarm or inspection means
Reexamination Certificate
1999-06-01
2001-03-27
Chambers, A. Michael (Department: 3753)
Fluid handling
With indicator, register, recorder, alarm or inspection means
C137S377000, C137S382000
Reexamination Certificate
active
06206033
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a device for locking a valve control handle and a method for using the device and more particularly, relates to a valve control handle safety lockout device for tamper-proving a valve handle once it is adjusted to an open or close position to prevent unauthorized adjustment of the handle and a method for using such valve control handle safety lockout device.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, a semi-conducting wafer must be processed in a large number of processing steps for producing integrated circuit chips on the wafer. These processing steps may amount to as many as several hundred or more. The various processing steps are conducted in a variety of processing machines to carry out a large number of chemical or physical reactions on the semi-conducting wafer. In the various fabrication steps, a large variety of chemicals including gases and liquids are utilized either as raw materials in a deposition process, as dopants in an implantation process, as an etchant in a wet or dry etching process, or as a chemical reactant in any other processes.
Since a large number of chemicals utilized in a semiconductor fabrication facility are of the flammable or toxic nature, i.e., other than those inert gases normally utilized as purge or carrier gases, the storage and transporting of such chemicals are important aspects in the management of a fabrication facility. For instance, to avoid fire, explosion and serious personal injuries, a flammable or toxic gas must be securely stored in a safe storage facility. The storage of these gases is usually kept away from the plant personnel and thus, away from the processing equipment where they will be used. The transporting or delivery of these gases to a processing equipment therefore becomes another important aspect in the management of a fabrication plant.
A typical gas delivery system utilized in a semiconductor fabrication facility is shown in FIG.
1
. The system
10
includes a main process gas input line
12
and a main purge gas supply line
14
. A process gas, after being fed into the main process gas input line
12
, is transported through a two-way air actuated valve
16
into a main process gas supply line
18
. Off the main process gas supply line
18
, a number of two-way, diaphragm-type (hereinafter, diaphragm) control valves
20
are utilized to feed the process gas from the main supply line
18
into a three-way diaphragm control valve
24
. Into the three-way diaphragm control valve
24
, a purge gas is also fed from the main purge gas supply line
26
into a second gas inlet
28
of the three-way diaphragm control valve
24
. The purge gas, i.e., an inert gas, fed through the inlet
28
is then mixed with the process gas fed through the inlet
22
and outputted from outlet
32
of the three-way diaphragm control valve
24
. It should be noted that in the above example, the purge gas is utilized as a carrier gas for the process gas. The purge gas may also be used alone for purging the gas line without the process gas. In such application, the three-way diaphragm control valve is adjusted such that only inlet
28
is connected to outlet
32
of the valve, while inlet
22
is shut-off.
When the purge gas is used as a carrier gas, the gas mixture is sent through a gas pressure regulator
36
, a pressure transducer
38
into a second three-way diaphragm control valve
42
through inlet
40
. The process gas/carrier gas mixture then exits from either outlet
46
or
48
and is fed into a process equipment. It should be noted that in
FIG. 1
, the process equipment and the gas lines feeding to the process equipment are not shown for simplicity reasons. When the gas outlets
46
,
48
are not connected to a process equipment or to a gas delivery line, the outlets
46
,
48
are capped by a cap
50
. In the gas distribution system
10
shown in
FIG. 1
, the main process gas input line
18
is further provided with an expansion valve
60
. The expansion valve
60
is provided such that other gas output lines may be connected thereto allowing future expansion of processing equipment in the fab facility. The outlets
62
,
64
are also capped by caps
66
when the expansion valve
60
is not in use for add-on additional gas supply lines.
In the gas distribution system
10
, it is seen that a number of two-way or three-way diaphragm-type control valves, i.e.,
20
,
24
and
42
are utilized for controlling the flow of various gases, including those of the flammable or toxic nature or vacuum in the supply lines. The control valves are equipped with control handles mounted on top of the valves such that a handle may be turned either clockwise or counterclockwise to close or open the gas passage. The control valves can be accidentally turned and thus releasing the vacuum in the line.
As shown in
FIG. 1
, when the gas line between the two control valves
20
,
42
has been evacuated into a vacuum state, and that the main process gas supply line
18
is connected to a pressurized flammable gas supply, any accidental opening of the control valve
20
may cause the flammable gas to enter the gas line between valves
20
and
42
. A flammable gas that is frequently utilized in a semiconductor fab plant is silane which readily ignites when mixed with air, or with oxygen in the air. Consequently, when cap
50
is later removed for connecting to a process equipment, the moment silane gas contacts the atmospheric air, a fore ignites in the gas line between valves
20
,
42
. If valve
20
has been left open, the fire propagates through the main process gas supply line
18
and causes further damages to other process gas feed lines and other process equipment.
The accidental opening or closing of valves can therefore cause serious consequences in a semiconductor fab plant that utilizes flammable or toxic gases. In the above described situation, even when the operator, after accidentally opened the control valve
20
, subsequently closes it, a serious hazard has already been created in the gas line since it is now filled with a flammable gas that is unknown to other plant personnel. When the gas line is accidentally filled with a toxic gas, serious personal injuries can occur to a machine operator when cap
50
is subsequently removed for connecting to other gas lines or to a process equipment.
It has been found that accidental tampering with a gas control valves in the gas distribution system has been a main cause for serious fires in many semiconductor fab plants. Even when fire does not occur, serious personal injuries has occurred to machine operators when a gas line is accidentally filled with a toxic gas. An effective means to prevent such mishaps is therefore desperately needed in a semiconductor fab plant that utilizes a gas distribution system.
It is therefore an object of the present invention to provide a gas distribution/control system for use in a semiconductor fabrication facility that does not have the drawbacks or shortcomings of a conventional gas distribution/control system.
It is another object of the present invention to provide a gas distribution/control system in a semiconductor fabrication facility that can be easily implemented without making substantial modification to the plant equipment.
It is a further object of the present invention to provide a gas distribution/control system in a semiconductor fabrication facility that can be effectively used without accidental opening/closing of control valves.
It is another further object of the present invention to provide a valve safety lockout device that can be made readily available in a semiconductor fabrication facility.
It is still another object of the present invention to provide a valve safety lockout device that can be utilized at low cost to effectively prevent accidental opening/closing of valves.
It is yet another object of the present invention to provide a valve control handle safety lockout device that can be used to lock a valve control handle so that any tamper
Chambers A. Michael
McShane Thomas L.
Taiwan Semiconductor Manufacturing Company , Ltd.
Tung & Associates
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