Depth measuring device

Abstract

Abstract PURPOSE:To measure the depth of a recessed part with high accuracy without being affected by the shape accuracy of an edge, by forming two kinds of the interference fringes corresponding to the surface and bottom surface of the recessed part of a Michelson interferometer and measuring the interval between two interference fringes. CONSTITUTION:The parallel beam 4a from a beam projection part 4 is split into beams 5, 6 by a beam splitter 7 and both beams are respectively incident to a specimen 1 and a mirror 11 and the reflected beams 23, 21 thereof interfere with each other in the splitter 7 and issue in the direction shown by an arrow 25 to be received by an observation means 2. When the mirror 11 is inclined by predetermined quantity with respect to an optical axis, linear interference fringes are obtained. Herein, the mirror 11 is moved in the direction shown by an arrow 18 by a piezoelectric element 19 so that the interference fringes formed by the surface S of the specimen 1 come to the specific position of the visual field of the observation means 2. At this time, the applied voltage due to a driver 20 is stored. Next, the mirror 11 is moved so that the interference fringes due to the bottom surface B of the recessed part 31 of the specimen 1 come to the same specific position in the visual field to store the applied voltage. Subsequently, the depth (d) of the recessed part 31 is calculated according to the relational expression of the applied voltage and moving quantities. Further, the coherent length of measuring beam is set to two times or less of the depth (d).

Inventors

• 👤 Akira Tsumura
• 👤 明 津村

Bibliographic Details