Fluid handling – Processes – Involving pressure control
Reexamination Certificate
2000-11-07
2003-07-29
Chambers, A. Michael (Department: 3753)
Fluid handling
Processes
Involving pressure control
C137S565230, C137S565330, C118S72300R
Reexamination Certificate
active
06598615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related generally to exhaust systems for plasma reaction chambers, and more particularly to a system adapted both for throttling chamber pressure and flow and for isolating a turbomolecular pump, vacuum pump, or cryogenic pump port.
2. Description of the Related Art
Many process steps in the production of semiconductor wafers and other electronic or industrial components require the use of plasmas within a plasma reaction chamber. During use, such reaction chambers are typically maintained at low pressure through mechanical vacuum pumps, turbomolecular pumps, or some combination thereof, as is well known in the art.
Precise pressure control for maintaining high vacuum conditions in the reaction chamber is conventionally accomplished by throttling a turbomolecular pump through a valve assembly. Valve assemblies currently in use, however, do not provide for isolation of the turbomolecular pump independently from a low vacuum, or “roughing,” pump during reaction chamber or valve assembly cleaning operations or other maintenance procedures. As a consequence, the turbomolecular pump employed in conventional systems may be exposed to atmospheric conditions, thereby exposing residual reaction chamber chemistries and by-products remaining in the pump to atmospheric water vapor and other contaminants. Such exposure of a turbomolecular pump to atmosphere during a reaction chamber cleaning process may introduce particulate contamination and cause chemical corrosion in the system, decreasing process efficiency and shortening the life of the pump.
There has been a continuing and growing need, therefore, for a method and apparatus capable of providing reaction chamber pressure control as well as enabling independent isolation of the turbomolecular pump such that the pump is not exposed to atmospheric conditions when other components of the system are undergoing maintenance operations.
SUMMARY OF THE INVENTION
The present invention overcomes the foregoing and other shortcomings of conventional valve assemblies used in conjunction with plasma reaction chambers in a method and apparatus which provide both throttling functionality as well as vacuum isolation for a turbomolecular pump. Briefly, the present invention prevents extended exposure of the turbomolecular pump to atmosphere, and allows faster reaction chamber recovery after cleaning.
The present reaction chamber design prefers combining the throttling pressure control function with the atmospheric isolation function to minimize pumping speed conductance losses within the reaction chamber as well as separating the pressure throttling and turbomolecular pump isolation functions to eliminate exposing chemical and polymer depositions deposited within the confines of the turbomolecular pump.
A throttle valve plate remains exposed to plasma and process chemistry, while a removable interface allows for easy off-line cleaning. A separate turbomolecular pump isolation plate is fully protected from process plasma and chemistry to preclude deposition from occurring on the isolation mechanism.
According to one aspect of the present invention, a method of exhausting a plasma reaction chamber includes throttling at least one exhaust pump at a throttle valve and providing for isolation of a turbomolecular pump independent of the operation of the throttle valve.
According to another aspect of the present invention, a valve assembly for use in conjunction with a plasma reaction chamber is generally constituted by an upstream port having an associated throttle valve, a high vacuum port having an associated gate valve, and a low vacuum port. The low vacuum port may be operable to evacuate the reaction chamber even when the gate valve closes the high vacuum port. Operation of the gate valve may be independent of the throttle valve.
According to another aspect of the present invention, a system including a plasma reaction chamber employs the inventive valve assembly.
The above-mentioned and other attendant advantages of the present invention will become more apparent upon examination of the following detailed description of the preferred embodiments thereof with reference to the attached drawings.
REFERENCES:
patent: 4212317 (1980-07-01), Patrick et al.
patent: 4949670 (1990-08-01), Krogh
patent: 5758680 (1998-06-01), Kaveh et al.
patent: 6041817 (2000-03-01), Guertin
patent: 6080679 (2000-06-01), Suzuki
patent: 6223770 (2001-05-01), Snow
Barnes Michael
Holland John
Leahey Patrick
Mak Steve S. Y.
Mohn Jonathan D.
Applied Materials Inc.
Bach Joseph
Chambers A. Michael
Sughrue, Mion, Zinn, MacPeak & Seas
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