Data on image shortening effects with patterns replicated with x-ray and optical lithography are presented. The x-ray exposures were performed at the IBM Advanced Lithography Facility using the Helios superconducting storage ring and a SUSS stepper. The optical exposures were performed using SVGL Micrascan 1 and 2 tools and biased optical masks. The results indicate that the image shortening effects using x-ray lithography (XRL) are considerably less pronounced than the effects observed with the optical tools. In addition, modeling of the image shortening effects for XRL using the xmas three-dimensional program for resist patterns is presented and compared with experimental results.
This paper describes a mask alignment technique for a projection printer in which the mask-to-wafer offset is determined interferometrically by a phase-locked method. The alignment patterns used in this method are cross grids which are illuminated with a He-Ne laser beam. By diffraction and interference a harmonic intensity signal is obtained whose phase is representative for the relative displacement of mask and wafer. Phase modulation and fine alignment are done with a tiltable glass plate driven by a galvanometric scanner. The total alignment operation including registration and fine alignment is controlled by a PC. With a registration precision in the nanometer region and cycle times below 0.3 s, this method is particularly suited for each field alignment in projection steppers. Results of theoretical and experimental investigations are discussed.
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