Practicing extension of 248-nm DUV optical lithography using trim-mask PSM

It is becoming increasingly clear that semiconductor manufacturers must rise to the challenge of extending optical microlithography beyond what is forecast by the current SIA roadmap. Capabilities must be developed that allow the use of conventional exposure methods beyond their designed capabilities. This is driven in part by the desire to keep up with the predictions of Moore's law. Additional motivation for implementing optical extension methods is provided by the need for workable alternatives in the event that manufacturing capable post-optical lithography is delayed beyond 2003. Major programs are in place at semiconductor manufacturers, development organization, and EDA software providers to continue optical microlithography far past what were once thought to be recognized limits. This paper details efforts undertaken by Motorola to produce functional high density silicon devices with sub-eighth micron transistor gates using DUV microlithography. The preferred enhancement technique discussed here utilizes complementary or dual-exposure trim-mask PSM which incorporates a combined exposure of both Levenson hard shifter and binary trim masks.