Patent ID: 7134668

Claim:
A differential pumping seal apparatus for use in a semiconductor fabrication apparatus, said apparatus comprising: a hydrostatic bearing comprising a working fluid supply source; a differential pumping seal for sealing a first space and a second space from each other in a non-contact manner so as to prevent fluid communication between the first space and the second space, a pressure of the first space being lower than a pressure of the second space; wherein during operation of said differential pumping seal, said working fluid supply source is maintained at a pressure greater than the pressure of said differential pumping seal, and a back up seal mechanism for sealing said first space and said second space from each other in a contact manner; wherein said back up seal mechanism, said hydrostatic bearing and said differential pumping seal are arranged in this order in a direction from the second space to the first space, and said back up seal mechanism seals said first space and said second space from each other only when operation of said differential pumping seal is stopped or while operation of said differential pumping seal is stopped.