| 摘要 |
PROBLEM TO BE SOLVED: To make measurable unevenness of wafer thickness with high accuracy by measuring the relative change amount of the surface and back of a wafer along the rectilinear scanning direction, selecting and calculating the increasing and decreasing directions as the same direction, and calculating the displacement of thickness from the sum of displacements corresponding to the scanning position. SOLUTION: A calculating program 12b for unevenness of wafer thickness is called by keying a designated function for measurement of unevenness of thickness, and executed by an MPU 11. When the program is executed, a laser irradiation position S is set in a designated measurement point of a wafer 1, and spiral scanning is performed taking the above point as a reference point to obtain a relative distance by the respective photo heterodyne interference measuring devices 3, 4. The sum of displacements on the surface and back sides is calculated to be taken as a thickness variation, and this variation is calculated on the respective measuring points on the wafer 1. Subsequently, the average value of the change amounts is calculated corresponding to each track and stored in a memory 12. After this processing is ended, a correcting process program 12C for unevenness of thickness is called. Spiral scanning is normally performed taking the center of the wafer 1 as reference to obtain a measured value.
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