LITHOGRAPHIC PERFORMANCE OF AN EL-3 SYSTEM AT 0.25-MU-M GROUNDRULES

Achieving 0.25-mu-m performance in a shaped electron beam tool has required not only enhancements to hardware and software, but also refined techniques for optimizing and monitoring resist image quality and spot placement accuracy. A compact test pattern has been designed to facilitate adjustment of the electronics which dynamically correct for astigmatism and field curvature. In some cases, SEM analysis is ineffectual in detecting either regional image quality problems or local spot placement errors. For this purpose, full-field fine line gratings have been highly effective when viewed optically at low magnification. Noise reduction and improvements to deflection electronics have contributed to short and long term stability for accurate exposures of large chips using stitched writing fields. Tight control of the tool and process results in the ability to pattern features down to 0.15-mu-m.