Patent ID: 8021485

Claim:
A positioning apparatus, comprising: a box body including a process chamber exposed to a decompression environment in the interior of the box body and an opening allowing said process chamber to communicate with an area outside of the box body; a moving member for shielding said opening of said box body with a slight clearance between said box body and the moving member and movable with respect to said opening of said box body; a driving portion that moves said moving member; and a differential pumping seal for sealing said slight clearance between said opening of said box body and said moving member, wherein on a portion of said moving member to be moved into the interior of said process chamber, when said moving member moves, there is formed a treated surface that restricts an amount of emission gas accumulatable thereon, and wherein a width of a portion of said box body opposed to said moving body in a moving direction of said moving member is set equal to or larger than a moving amount of said moving member.