| 摘要 |
<p>PURPOSE:To accurately determine the quantity of eccentricity by a method wherein a value most frequently detected in diameter distribution is presumed to be a wafer diameter before an accurate wafer diameter is determined, a four-point position detection free of noise, etc., is accomplished, and the quantity of eccentricity is determined using the result of the four-point position detection. CONSTITUTION:Outer circumference position data along the entire wafer circumference are determined by a wafer outer circumference position data detecting means, distances rhofrom the center of rotation of a theta-stage 2 to the wafer edge is detected at every point, a distance rho1 involving a point (i) and a distance rho1+180 deg. involving a point i+180 deg. which is 180 deg. degrees apart from said point (i) are summed up, for the approximation of a wafer diameter r1 involving said point (i). The same is repeatedly accomplished to cover half the wafer circumference for the preparation of a wafer diameter frequency distribution, wherein the most frequently observed value is presumed to be a diameter (r). Distances from the center of rotation of the theta-stage 2 to four points, free of noise and 90 deg. apart from each other, are measured for the determination of the quantity of eccentricity from the center of rotation. When four points are not available, three points separated by 90 deg. may be used to determine the quantity of eccentricity, when the most frequently appearing value in the frequency distribution is determined to be the quantity of eccentricity.</p> |
