Fluid handling – With liquid valves or liquid trap seals – Liquid seal in liquid flow line; flow liquid forms seal
Reexamination Certificate
2000-05-02
2001-08-28
Rivell, John (Department: 3753)
Fluid handling
With liquid valves or liquid trap seals
Liquid seal in liquid flow line; flow liquid forms seal
C137S247410, C137S247190, C355S018000, C355S030000
Reexamination Certificate
active
06279601
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
BACKGROUND OF THE INVENTION
The present invention is directed generally to a liquid seal for maintaining pressure differentials between various parts of an apparatus. In particular, to a seal that provides for defining separately controlled vacuum zones. The low gas conductance seal is mechanically robust and is designed so that mechanical vibrations cannot be transmitted through the seal.
Quite often, within an apparatus, such as a piece of processing equipment, it can be desirable to define zones having different pressures and to maintain these differential pressures for extended periods of time. There are various ways of accomplishing this separation such as by the use of physical structures or barriers that act to seal one region of the apparatus from another. In systems that operate at sub-atmospheric pressures, these zones can be maintained by means of differential pumping, i.e., having separate vacuum pumps to control the pressure-within the various regions. In addition to establishing zones or regions having different pressures, it can also be necessary in some applications to minimize or substantially eliminate vibration transmission from one zone or region to another.
Seals capable of creating zones of different pressure within a vacuum system while at the same time transmitting negligible or substantially no vibration are particularly desirable for applications such as Extreme Ultraviolet Lithography (EUVL). Here Extreme Ultraviolet (EUV) radiation (10-14 nm) is used to produce features having linewidths less than 100 nm. Because of the very fine dimensional tolerances (≈10s of nm) involved in EUVL low vibrational transmission is an absolute necessity. It can also be desirable to have a seal that can operate with pressure differentials up to 0.5 Torr while at the same time having negligible gas conductance. Moreover, it can also be desirable to have a mechanically robust seal that can maintain its structural integrity. It can be necessary to clean the inner surfaces of the vacuum system from such things as carbon deposits. This cleaning operation is frequently done by rf-discharge cleaning, wherein reactive oxygen species are introduced into the vacuum system. Thus, it is further desirable that the zone seal be resistant to reactive ion species used for cleaning the vacuum system.
SUMMARY OF THE INVENTION
This invention is based, in part, on the recognition that in some technologies it is necessary to create zones having different pressures within the same apparatus. This is particularly true in vacuum-based technologies such as extreme ultraviolet lithography (EUVL), electron projection lithography (EPL), and ion beam lithography (IPL), were it is necessary to create and maintain separate vacuum zones while at the same time maintaining low vibration transmissibility from one structure to another.
Accordingly, it is an object of this invention to provide a seal assembly for maintaining different pressure zones in an apparatus.
It is another object to provide a seal assembly for a vacuum system having separately controlled vacuum zones.
It is a further object to provide a seal assembly that will not transmit mechanical vibrations from one zone to another or from the walls of the apparatus to the interior.
Yet another object is to provide a seal assembly that is mechanically robust.
A further object is to provide a seal assembly that can maintain a pressure differential of at least about 0.5 Torr between the separate zones.
Another object is to provide a seal assembly that will not be a source of gaseous contaminants.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings.
In one aspect, the invention is directed to a conductance limiting and substantially vibration-free zone seal assembly for establishing zones of differential pressure in an apparatus by connecting first and second members that are spaced apart, the seal assembly including:
a housing defining a vacuum chamber;
a tray, or barrier, within the vacuum chamber that can be supported by at least one support member, wherein the tray separates the vacuum chamber into a first compartment and a second compartment which are at different pressures;
a well or depression formed along the perimeter of the tray that contains fluid having a low vapor pressure; and
means for joining the inner surface of the housing to the fluid, wherein the combination of the joining means and the well along the perimeter of the tray form an aperture at the boundary between pressure zones and the fluid in the well seals the aperture forming a gas conductance limiting and vibration-free seal.
In another aspect, the present invention is directed to a EUV photolithography apparatus that includes:
a housing having an outer enclosure that defines a cavity and an inner enclosure, disposed within the cavity, that defines a vacuum chamber;
a first tray, situated within the vacuum chamber, that can be supported by at least one support member, wherein the first tray separates the vacuum chamber into a first and a second zone, wherein the first and second zones can be at different pressures;
a second tray, situated within the vacuum chamber, that can be supported by at least one second support member, and spaced apart from the first tray, wherein the second tray defines a third chamber that can be at a different pressure from either of the first and second chambers;
a reticle stage that supports a reflective reticle, disposed within the first chamber;
a projection optics device disposed within the second chamber;
a wafer stage that supports a photoresist coated wafer disposed within the third chamber;
a well or depression formed along the perimeter of each tray that contains fluid having a low vapor pressure; and
means for joining the inner surface of the inner enclosure to the fluid, wherein the combination of the joining means and the fluid contained in the well formed along the perimeter of each tray provides a conductance limiting and vibration-free seal that serves to define and maintain a pressure zone within the apparatus.
In a preferred embodiment, joining means comprises a plate extending from the inner wall of housing or inner enclosure that intersects with and is immersed in the fluid contained in the well formed in the tray contained within the vacuum enclosure. In this instance, the fluid is a low vapor pressure oil, chemically inert and oxidation resistant.
REFERENCES:
patent: 1708465 (1929-04-01), Boosey
patent: 3290022 (1966-12-01), Brown, Jr. et al.
patent: 4198717 (1980-04-01), Kessel
patent: 4502500 (1985-03-01), Upton
patent: 6031598 (2000-02-01), Tichenor et al.
EUV LLC
Nissen Donald A.
Rivell John
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