Position detection device by fan-shaped Fresnel zone plate using multi-wavelength illumination

摘要

PURPOSE:To accurately detect the positions of a mask and a wafer by providing an alignment mark made of a sector-shaped Fresnel zone plate(SFZP) on each article, and irradiating the SFZP simultaneously with a light having a plurality of wavelengths from the same direction. CONSTITUTION:An illumination optical device 5 combines a laser light having a wavelength lambda1 from a laser 1 and a laser light having a wavelength lambda2 (lambda1lambda2) by a beam splitter 2, and reflects it as a parallel beam obliquely downward by a mirror 4 to radiate it. A detecting optical device 10 has an objective lens 9 having an axial chromatic aberration. The lens 9 has different focal distances of the lights having the wavelengths lambda1 and lambda2, brings the focal points having different positions of the alignment mark 16 of a mask 14 made of SLZP and the alignment mark 17 of a wafer 15 according to the lights having the wavelengths lambda1, lambda2 into coincidence with those of the lens 9 of the lights having the lambda1, lambda2, superposed on a linear sensor 6 by a relay lens 8 to be imaged. A detection signal from the sensor 6 is detected at positions of the marks 16, 17 in a direction Y by a predetermined signal process.