To measure the height of the top of a spherical surface shape accurately, by comparing a waveform obtained from a digital data indicating the height of every bump detected through an optical microhead and stored with a reference waveform while shifting vertically and laterally and operating correlation after the waveforms are shifted.
Top position 103 of a standard waveform is superposed on a temporary top position 105 of a detected waveform and correlation is found. An origin is set at the position 103 where the central axis of the standard waveform is aligned with that of the detected waveform and X-axis extends in the scanning direction of a detector while Z-axis extends in the direction of height. A correlation coefficient is calculated from the X-coordinate value of a collection of point data, i.e. a standard detection waveform, and the Z- coordinate value in the X-coordinate. Subsequently, the standard waveform is shifted in X and Z directions. The comparison operation of vertical and lateral shift is repeated within a preset range and a correlation coefficient is determined for each case. Top height is determined by adding the shift in Z-direction at a position having a highest correlation coefficient to the height at the position 103 of a waveform 101.
SASAKI HIDEAKI
WAI SHINICHI
Next Patent: INSTRUMENT FOR MEASURING THICKNESS AND THICKNESS VARIATION OF WAFER