Hybrid optical maskless lithography: Scaling beyond the 45 nm node

Optical lithography at 193 nm with resolution enhancements and immersion is widely expected to meet the needs of the 45 nm node. Beyond this, at 32 nm and below, the solution is not as clear. In this article we present simulation results and experimental demonstrations of an all-optical approach capable of high-throughput 32 nm lithography (hybrid optical maskless lithography). In this method high-resolution dense gratings are defined in a first exposure using maskless interference lithography. A second “trim” exposure, using conventional projection lithography, customizes these gratings into useful patterns. Our simulations indicate that 32 nm node patterning can be achieved using trim tools and masks of significantly lower resolution. We also present experimental feasibility results using 157 nm “dry” interference in combination with projection 248 nm or e -beam trim exposures. The technological requirements and extendibility of such a method beyond the 32 nm node are also examined.