Patent ID: 6566661
Filing Date: 2003-05-20
Classification: H01J

Abstract:
An ion implanter having an evacuatable implant chamber,a holder inside the chamber for holding a semiconductor wafer at a selected wafer angle during implantation, said holder being adjustable about at least one axis parallel to the plane of a wafer on the holder for changing said wafer angle, a source of focused electromagnetic radiation, mounted relative to said implant chamber and arranged to direct said radiation for reflection at a surface of a wafer held on said holder or at a surface of the holder, which is parallel or at a known angle to the plane of a wafer when held on said holder, a sensor mounted relative to said implant chamber to receive radiation from said source reflected specularly by the wafer surface or by said holder surface, said sensor providing a signal, in response to the reflected radiation, which is indicative of a predetermined wafer angle, a drive unit to adjust the rotary position of said holder about said axis and providing a rotary position signal, and a controller responsive to said signal from said sensor to reference the rotary position of said holder represented by said rotary position signal to said predetermined wafer angle indicated by said sensor signal.