High-throughput hybrid optical maskless lithography: all-optical 32-nm node imaging

We analyze the performance and process latitudes of a high-throughput, all-optical lithography method that addresses the requirements of the 32-nm node. This hybrid scheme involves a double exposure and only a single photomask. The first exposure forms dense gratings using maskless immersion interference lithography. These regular grating patterns are then trimmed in a second exposure with conventional projection lithography. While the highest resolution features are formed with interference imaging, the trimming operation requires significantly lower resolution. We have performed lithography simulations examining a number of representative 32-nm node patterns; both one-dimensional and two-dimensional. The results indicate that 32-nm node lithography requirements can be met using a hybrid optical maskless (HOMA) approach. Trim photomasks can be two to three generations behind the fine features, while the trim projection tools can be one to two generations behind the fine features. This hybrid optical maskless method has many of the benefits of maskless lithography without the severe throughput challenge of currently proposed maskless technologies.