Progression of overlay performance on a 0.5-NA broadband DUV wafer exposure system

The MICRASCAN-II (MS-II) is a 0.50 NA DUV broadband illumination (245 nm to 252 nm) step-and-scan exposure system manufactured by Silicon Valley Group Lithography Systems, Inc. (SVGL) of Wilton, Connecticut. The system is designed to provide 350 nm resolution and 90 nm overlay in a semiconductor manufacturing environment. Overlay system improvements and performance testing have been made on pre-production and production versions of the MS-II. The MICRASCAN system has both a laser illuminated `through-the-lens' (TTL) and a broadband illuminated `off-axis alignment system' (OAAS). This paper summarizes the progression of system overlay improvements and the results of the tests conducted. Results from initial baseline tests pre and post system improvements on artifact wafers are presented. Product level data collected from marathon testing showing system performance on six individual product levels and areas for improvement are presented. Descriptions of an improved TTL alignment system and its attributes are provided. A description of a new and completely independent alignment system (OAAS) and its attributes are discussed.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.