| 摘要 |
A position detection method detects the position of a mark formed at the bottom of a film such as a polysilicon layer which transmits no visible light. A flattened alignment mark (26) is formed on a wafer (4), onto which the pattern on a reticle (R) is transferred. A polysilicon film (27) is formed on the alignment mark (26). An alignment sensor (3) includes a laser light source (10) and a frequency shifter (12), which produce light beams (LA and LB) having wavelengths between 800 and 1500 nm and differing slightly in frequency from each other. The beams (LA and LB) are radiated through a projection optical system (PL) and transmitted by the polysilicon film (27) to irradiate the alignment mark (26). The diffracted light (LD) from the alignment mark (26) is received through the optical system (PL) by a photoelectric detector (16). On the basis of the signal detected by the photoelectric detector (16), the position of the alignment mark (26) is detected. <IMAGE> <IMAGE> |
