Patent ID: 6555832
Filing Date: 2003-04-29
Classification: H01J

Abstract:
An alignment measuring apparatus comprising:a process chamber having a chamber wall; an ion beam generator to produce a bean of ions for implantation, said beam having a nominal beam direction in said chamber; a wafer holder in said chamber to carry for ion implantation therein a planar crystalline wafer having a crystal axis nominally normal to the plane of the wafer, said wafer holder having a normal direction which is nominally normal to the plane of a wafer on said holder; a tilt mechanism for adjusting the tilt angle of said normal direction of the holder relative to said nominal beam direction about an axis perpendicular to said normal direction and to said nominal beam direction; and a twist mechanism for rotating the holder and any wafer thereon to selected rotational positions about an axis nominally parallel to said normal direction, the alignment measuring apparatus comprising: a scattered ion receiver adapted to be mounted on said chamber wall to receive beam ions back scattered from a wafer on the holder; and a scattered ion current detector for determining the current said back scattered beam ions received by said receiver, said scattered ion receiver including a filter to reject low energy secondary ions from the wafer and pass substantially only back scattered beam ions to said current detector.