Fluid handling – Processes
Reexamination Certificate
2000-06-28
2001-12-11
Lee, Kevin (Department: 3754)
Fluid handling
Processes
C137S613000, C137S614110, C137S565230
Reexamination Certificate
active
06328051
ABSTRACT:
FIELD OF THE DISCLOSURE
The present disclosure relates to gate valve assemblies, and more particularly to a dual pendulum valve assembly comprising a process chamber isolation valve and a vacuum pump isolation valve. The vacuum pump isolation valve is useful for isolating a vacuum pump coupled to the pendulum valve assembly so that the vacuum pump is not exposed to the atmosphere during cleaning of the pendulum valve assembly and process chamber.
BACKGROUND OF THE DISCLOSURE
A pendulum valve assembly generally includes a housing containing a pendulum valve and including an interior space and a pair of openings through which gaseous fluid can enter and exit the interior space. As its name implies, a pendulum valve pivots between open and closed positions, and includes a valve body, which is usually provided as a disk, connected to a rotatably shaft by a pivot arm. In a completely opened position the disk of the pendulum valve is moved out of the flow path defined by the openings so that fluid can enter and exit the interior space of the housing, while in a completely closed position the disk is moved into sealing contact with a valve seat surrounding one of the openings so that fluid can not enter the interior space.
The movement of the disk usually requires pivotal or rotational movement between a first angular position equal to the completely opened position and a second angular position, and then at least some translational movement from the second angular position into the completely closed position where the disk is in sealing contact with the valve seat. In order to obtain this combination of rotational and translational movement, prior pendulum valves have typically used multiple actuator elements which are inherently difficult to effect precise movement of the disk, and therefore more difficult to utilize for precise flow control purposes. For examples of such prior pendulum valves see the following: U.S. Pat. Nos. 2,850,260; 3,557,822; 3,722,857; 3,973,753; 4,052,036; 4,089,505; 4,333,631; 4,627,567; 4,785,844; 5,873,562; British Patent No. 1,050,435 and German Patent 1,190,755. Other valve structures are shown in U.S. Pat. Nos. 2,749,082; 3,854,696; 4,073,468; 4,088,301; 4,136,854; 4,395,049; 4,442,996; 4,458,905; 4,519,578; 4,921,213; 5,379,983; and 5,330,157.
U.S. patent application Ser. No. 09/339,084 discloses an improved pendulum valve assembly that is designed and constructed so as to eliminate the need for multiple actuator mechanisms. Instead, the improved pendulum valve assembly uses a simple rotating cam mechanism that precisely controls the rotational and axial movement of the valve body between a completely opened position and a completely closed position.
Pendulum valves are particularly useful in high purity gas delivery systems, such as those used in semiconductor manufacturing or other thin film coating processes performed at very low pressures (high vacuums), e.g., a pressure on the order of one torr or less. One ultra-high vacuum system adapted to operate at low conductances includes a vacuum pump separated from a process chamber by a pendulum valve, which helps control the pressure created in the process chamber by the vacuum pump within a predetermined range.
The process chamber of high purity gas delivery systems normally require cleaning after a given period of use. Such cleaning involves a physical scrubbing of the chamber surfaces and associated vacuum components, such as the pendulum valve that isolates the process chamber.
When the pendulum valve is cleaned it is necessary to shut down the vacuum pump and vent the entire system to atmosphere. Since the vacuum pump contains residues from the process conducted within the process chamber, venting to atmosphere exposes these residues to water vapor and other contaminants that may react with the residues to produce a corrosive agent that can lead to corrosion and premature failure of the vacuum pump. For example, using boron trichloride (BCl
3
) to etch an aluminum layer produces a residue of aluminum trichloride (AlCl
3
). When the aluminum trichloride residue reacts with water vapor in the atmosphere, an extremely corrosive hydrochloric acid (HCl) is produced.
As is known, such vacuum pumps are very expensive and difficult to replace. Accordingly there is a need for a device or means for isolating the vacuum pump from the atmosphere during cleaning of the process chamber and the pendulum valve.
SUMMARY OF THE DISCLOSURE
In accordance with the present disclosure, a dual pendulum valve assembly is provided for isolating the vacuum pump from the atmosphere during cleaning of the process chamber and the pendulum valve assembly. The dual pendulum valve assembly includes a housing having an interior space and first and second openings through which fluid can enter and exit the interior space; valve seats disposed in the interior space around the edges of the openings; and first and second pendulum valves for opening and closing, respectively, the first and second openings.
Each pendulum valve is independently movable and includes a valve body mounted relative to the housing so-that the valve body is movable within the interior space between a completely opened position wherein fluid is allowed to pass through its respective opening and a completely closed position wherein the valve body engages the valve seat around its respective opening and seals the opening so that fluid can not pass therethrough. Each pendulum valve also includes a shaft fixedly coupled to the valve body through at least one pivot arm and at least partially mounted within the housing so that the valve body can rotate about a longitudinal axis of the shaft between a first angular position where the first valve body is in the completely opened position and a second angular position where the valve body is substantially axially aligned with its respective opening, and move substantially parallel to the longitudinal axis of the shaft, so that the valve body can move between the second angular position and the completely closed position as the pendulum valve continues to rotate.
The dual pendulum valve assembly disclosed herein preferably utilizes simple rotating cam mechanisms that precisely controls the rotational and axial movement of the valve bodies between their completely opened and completely closed positions.
The present disclosure also provides a method of precisely controlling vacuum pressure within a process chamber of a semi-conductor wafer fabricator utilizing the dual pendulum valve. The method includes connecting the vacuum pump to the process chamber through the first and the second openings of the valve housing, respectively, and operating the vacuum pump to create a first pressure within the process chamber.
Then, the first valve body is moved to at least partially impede gaseous flow through the first opening, such that a second pressure within the process chamber is achieved. The second valve body is then substantially aligned with the second opening, such that a third pressure within the process chamber is achieved. Finally, the second valve body is laterally moved to substantially seal the second opening, such that a fourth pressure within the process chamber is maintained.
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Lee Kevin
McDermott & Will & Emery
MKS Instruments Inc.
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