Wafer thickness measurement device and method for same

A wafer thickness measurement method comprising:

• an interferometer reference measurement step of acquiring first and second interferometer reference measurement results by measuring, with a pair of first and second optical interferometers dispose to face each other with a measurement target wafer interposed between the first and second optical interferometers, a reference measurement point on a reference piece having the reference measurement point at which the reference piece has a known thickness;
• a distance meter reference measurement step of acquiring first and second distance meter reference measurement results by measuring the reference measurement point with a pair of first and second distance meters that are disposed to face each other with the measurement target wafer interposed between the first and second distance meters and that measure absolute distances;
• an interferometer measurement step of acquiring first and second interferometer measurement results by measuring the measurement point on the measurement target wafer with the first and second optical interferometers;
• a distance meter measurement step of acquiring first and second distance meter measurement results by measuring the measurement point with the first and second distance meters;
• and
• a thickness calculation step of obtaining, based on:
• the first and second interferometer reference measurement results acquired in the interferometer reference measurement step;
• the first and second distance meter reference measurement results acquired in the distance meter reference measurement step;
• the first and second interferometer measurement results acquired in the interferometer measurement step;
• and the first and second distance meter measurement results acquired in the distance meter measurement step, a number of phases between a reference displacement obtained based on the first and second interferometer reference measurement results and a displacement obtained based on the first and second interferometer measurement results, and obtaining a thickness, of the measurement target wafer, at the measurement point.