To easily adjust the extent of focusing range corresponding to the positioning precision of a semiconductor substrate supporting mechanism of respective process apparatuses and at the same time, to improve the function of detecting foreign matters and improve the production yield by making the numerical apertures for illuminating light for detecting focal point changeable.
Light rays from a lighting source 101 such as a semiconductor laser pass through a lens 102a and reach an object work (a wafer) 4 whose focal point to be measured, and thus an image of the lighting source 101 is formed. Moreover, the image of the lighting source 101 focused on the work 4 is formed on a detector 105 by a lens 102b. The number of apertures of the lens 102a can be adjusted through an aperture diaphragm 103 by properly selecting lens stops with different sizes. That is, the size of the spot diameter of the work 4 can be adjusted by selecting the diameter of an aperture diaphragm 103. Consequently, the size of the spot diameter oon the detector 5 can be adjusted, so that the extent of the focusing range can be adjusted corresponding to the positioning precision of the z-axial stage 108.
NOGUCHI MINORU
MORIOKA HIROSHI
SAKAI SHIGETOSHI
NISHIYAMA HIDETOSHI
HITACHI ELECTR ENG
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