DECISION OF CENTER OF DISK, SUCH AS WAFER, AND CENTER DECISION DEVICE FOR DISK, SUCH AS WAFER

摘要

PURPOSE: To determine the center of a disk including a discontinuous part, such as an orientation flat, with high accuracy by a method wherein variances on data on the distances of a prescribed ratio are calculated from data on the longest distance among data on the distance from one point of the disk to the plural peripheral edge parts of the disk and the center of the disk is determined. ;CONSTITUTION: When a wafer 2 is rotated, light from a light source 27 is received by a linear optical sensor 23 and is transmitted to an arithmetic means along with data from a pulse motor 11 for rotation. The arithmetic means converts the positions of the peripheral edge parts 2a of the wafer 2 to each angle ϕ_m of rotation into an X-Y coordinate system using the center O_c of rotation as its origin to integrate data on the positions. Then, constant distances (x₁) and (y₁) are increased and decreased and are changed to set a visual center O₁, the distances R_1m,... from the virtual center O₁ to the peripheral edge part 2a,... of the wafer 2 are calculated and variances on N R_1m,... are calculated from the longest one. The virtual center, which makes smallest the variances among the plural virtual centers O₁, (O₂),..., is selected and the virtual center is determined to be the center of the wafer 2.;COPYRIGHT: (C)1996,JPO