Vacuum bearing structure and a method of supporting a movable member
AssigneeApplied Materials, Inc.
InventorsGeoffrey Ryding, Theodore H. Smick, Marvin Farley, Takao Sakase
Life of this patent
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Abstract
A vacuum bearing structure comprises a combination of a planar gas bearing with a differentially-pumped vacuum seal. The bearing surface and the vacuum seal surfaces are formed of a porous material divided into a first outer region through which bearing gas can percolate to provide support and an inner second region providing the vacuum seal. An exhaust groove separates the two regions so that bearing gas can flow to atmosphere. The resulting structure can operate at a lower fly height to reduce loading on the differentially-pumped vacuum seal. The structure is particularly useful for motion feedthroughs into vacuum processes such as ion implantation.
Claims21
A vacuum bearing structure comprising:
- a vacuum chamber including a wall having an aperture,
- a movable member arranged to extend through said aperture,
- one of said vacuum chamber wall and said movable member having a first bearing surface provided thereon,
- the other of said vacuum chamber wall and said movable member having a second bearing surface provided thereon,
- said first and second bearing surfaces extending transverse to the line of action of external pressure acting on said movable member to urge said surfaces towards each other,
- said first and second bearing surfaces permitting a predetermined movement of said movable member relative to said chamber wall,
- said first bearing surface being provided by porous gas-permeable material facing said second bearing surface,
- said porous material having a first region which is porous to gas flow through the thickness of the material and a second, inner region between said first region and the interior of the vacuum chamber,
- at least one gas supply plenum beneath said first region for a supply of bearing gas under pressure to percolate through said porous first region to apply a bearing pressure to said second bearing surface opposing the action of said external pressure,
- an exhaust groove through said porous material and positioned between said first region and said second, inner region thereof, and
- an exhaust plenum connecting to said exhaust groove for allowing bearing gas to escape from between said bearing surfaces.
A vacuum bearing structure comprising:
- a vacuum chamber including a wall having an aperture,
- a movable member arranged to extend through said aperture,
- a bearing between said vacuum chamber wall and said movable member allowing a predetermined movement therebetween, first and second spaced opposed sealing surfaces on said vacuum chamber wall and said movable member, a continuous differential pumping groove in said first sealing surface, respective lands of said first sealing surface on each side of said differential pumping groove, a differential pumping plenum extending beneath said differential pumping groove along substantially the entirety of the dimension transverse to the width dimension of said differential pumping groove and having a width greater than the width of said differential pumping groove so that at least one edge of the differential pumping groove is cantilevered over the underlying differential pumping plenum, and bridging elements crossing over said differential pumping plenum under said differential pumping groove to support said at least one cantilevered edge of the differential pumping groove.
A method of supporting a movable member in an aperture provided in a wall of a vacuum chamber, wherein one of said vacuum chamber wall and said movable member has a first bearing surface and the other has a second bearing surface, and the first and second surfaces extend transverse to the line of action of external pressure acting on said movable member to urge said first and second surfaces towards each other and permit a predetermined movement of said movable member relative to said chamber wall, the method comprising the steps of
- providing a porous gas-permeable material as said first surface facing said second surface, said porous material having a first outer region which is porous to gas flow through the thickness of the material and a second, inner region,
- applying gas under pressure via a gas supply plenum to said first region to permit gas under pressure to percolate through said first region to apply bearing pressure to said second surface opposing the action of said external pressure, and
- exausthing gas to atmosphere via an exhaust channel between said outer and inner regions.
Dependencies are inferred from the claim text.