Patent ID: 7292428

Claim:
A lift pin assembly for use in a reactor for processing a workpiece, said lift pin assembly comprising: plural lift pins extending generally parallel with a lift direction, each of said plural lift pins having a top end for supporting a workpiece and a bottom end; a lift table translatable in a direction generally parallel with said lift direction; a first lift pin force detector for an individual first one of said lift pins, comprising: (a) an elastic plate having one end attached to said lift table and an opposite end, said elastic plate supporting the bottom end of said first one of said lift pins; (b) a small force detector responsive to a deflection of said elastic plate for sensing a force exerted by said first one lift pin that is sufficiently large to indicate a chucked wafer and sufficiently small to avoid dechucking a wafer; and (c) a large force detector responsive to a force exerted on said elastic plate by said first one lift pin in a range sufficient to de-chuck the wafer.