Patent ID: 8519363

Claim:
A wafer handling method performed in an ion implanter including a platen configured to hold a wafer having a notch on an outer peripheral region thereof, a twist angle adjustment mechanism configured to adjust a twist angle, which is an angle of the notch of the wafer with respect to a first reference position and an aligner configured to adjust an alignment angle, which is an angle of the notch of the wafer with respect to a second reference position, the method comprising: adjusting an alignment angle while rotating the wafer by the aligner; transferring, after adjusting the alignment angle, the wafer from the aligner to a twist angle adjustment mechanism that is disposed inside an ion implantation chamber of the ion implanter, wherein the twist angle adjustment mechanism comprises the platen and the platen is configured to hold the wafer during ion implantation; irradiating at least three portions on the outer peripheral region of the wafer on the twist angle adjustment mechanism with a light from a first side of the wafer without irradiating an entirety of the outer peripheral region of the wafer, after transferring the wafer; taking an image of the wafer on the twist angle adjustment mechanism from a second side of the wafer; detecting the twist angle of the wafer on the twist angle adjustment mechanism based on the image of the wafer; and performing a twist control in which the wafer is rotated by the twist angle adjustment mechanism by an angle obtained from a first difference between the detected twist angle and the alignment angle and a second difference between the alignment angle and a target twist angle given as one of ion implantation conditions.