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25 July 1989 In-House Characterization Technique For Steppers
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Abstract
This paper propose an user characterization technique for optical steppers. The purpose of such technique is to understand and to control those factors which affect stepper performances when fabrication of structures close or below the resolution specifications of the optical system is required. Two main factors are considered to limit stepper capabilities in submicron lithography: the imaging optics as a transmitter of high spatial frequencies with certain image intensity profile and the photoresist as a receiver of this optical information. The reported experiments use as the resist receiver a positive resist with a basic component added (0-4% by weight) in order to increase the resist transfer function and to decrease the K factor (from Rayleigh two points resolution criteria for isolated patterns, R = Kλ/N.A.). From spectral absorption of the in-house doped resist, we found that doping component concentration makes the process suitable for high resolution/ minimizing reflectivity/stepper target recognition. The imaging optics factors, a 0.31 N.A. /10X and 0.30-0.40 N.A./5X g-line steppers have been tested in the reversed resist process for linewidth change with defocus for various first/second exposure doses;exposure-defocus window;depth of focus for tangential/sagittal 1 micron lines/spaces patterns;lens capabilities to reproduce over all 10x10 mm field horizontal and vertical 1 micron lines. The latter is a useful indication in mixing-and-matching two steppers. Minimum 0.5 micron isolated patterns were reproduced in the reversed process, simultaneously in opposite polarities. The imaging optics was tested also for third order distorsion and errors of 50 ppm at optical field edges could be simply detected.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mircea Dusa and Dan Nicolau "In-House Characterization Technique For Steppers", Proc. SPIE 1088, Optical/Laser Microlithography II, (25 July 1989); https://doi.org/10.1117/12.953162
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