Patent ID: 6829040
Filing Date: 2004-12-07
Classification: G03F

Abstract:
A projection lithography system for exposing a photo sensitive material on a surface of a semiconductor substrate that includes surface height variations between a high level and a low level, the projection lithography system comprising:an illumination source projecting illumination within a narrow wavelength band centered about a nominal wavelength on an optic path towards the substrate during an exposure period; a wavelength modulation system within the optic path comprising: means for chromatically separating the narrow wavelength band into at least two sub-bands, the first sub-band being smaller than the narrow wavelength band and centered about a first sub-band wavelength and the second sub-band being smaller than the narrow wavelength band and centered about a second sub-band wavelength; and means for passing each of the first sub-band and the second sub-band during distinct time periods within the exposure period a patterned mask within the optic path; a lens within the optic path for focusing an image of the patterned mask onto the photosensitive material, the lens having chromatic aberration characteristics that provide for: focusing the image of the patterned mask at the low level when the first wavelength band is passed through the wavelength modulation system; and focusing the image of the patterned mask at the high level when the second wavelength band is passed through the wavelength modulation system.