0.5-micron deep-UV lithography using a Micrascan-90 step-and-scan exposure tool

Deep UV exposures utilizing wavelengths from 240-254 nm have been investigated for 0.5 micron lithography on a 0.35 NA step-and-scan exposure tool, the SVG Lithography Systems Inc. Microscan-90. Commercially available Shipley SNR-248 3X negative resist was characterized with statistically designed experiments, and the optimized single-level resist process was used for tool characterization at and below 0.5 micron. Examples of a new developmental positive resist are also shown. The effect of reflectivity variations with broad- band exposures are modeled and compared with the experimental results. Resolution and depth of focus (DOF) for both 0.4 and 0.5 micron features were studied over the full field. Results for contact holes over topography and critical dimension (CD) variation with DOF and exposure are presented. The tool focus control, stage precision, throughput, overlay capability on oxide and poly wafers, and particulate contamination studies are reported. Process latitude is evaluated. The tool and process compatibility for sub-half micron applications is discussed.