| 摘要 |
<p>PROBLEM TO BE SOLVED: To catch light at a position wherein the quantity of light reflected in a bottom or a surface of a dot mark concentrates most, by setting an arrangement position of an object lens at a place wherein the focus of reflection light and the focus of an object lens almost coincide with each other. SOLUTION: A semiconductor wafer W is moved to an area near the focus of an object lens 1 and the object lens 1 alone is moved up and down to maximize sensor output of a light quantity detector 16 of a confocal detection mechanism 10 and focusing is finished. Parallel light is directed to a dot mark in a surface of the semiconductor wafer W from a reading light source 7 and focusing light directed to an area near a dot mark is directed from a detection light source 14. Reflection light is received by an image receiver 5 through first and second half mirrors 2, 3, a position wherein brightness of a dot central part thereof is the highest is detected by image processing, etc., and the object lens 1 is set at the place. As a result, a focus position of a dot mark on the wafer W and a focus position of an object lens are made coincide with each other and enough discrimination property of a dot mark is ensured.</p> |
