Spectral analysis of line width roughness and its application to immersion lithography

Various approaches can be used to quantify line width roughness (LWR). One of the most commonly used estimators of LWR is standard deviation sigma. However, a substantial amount of information is ignored if only sigma is measured. We use an automated approach to investigate LWR, where standard deviation, correlation length, and power spectrum are measured online on critical dimension scanning electron microscopes. This methodology is used to monitor LWR, investigate the effect of LWR on critical dimension precision, and to benchmark new resists for immersion lithography. Our results indicate that online LWR metrology is a critical tool in a variety of applications, including but not restricted to process control. (C) 2006 Society of Photo-Optical Instrumentation Engineers.