Rasterizing for SLM-based mask-making and maskless lithography

摘要

In high fidelity SLM-based mask making and maskless lithography, a high performance rasterizer with high capability is of utmost importance. The rasterizer must be capable, not only to convert the vector format input data to a bitmap suitable for the SLM in fractions of seconds, but also to perform image adjustments in terms of edge placement and edge acuity. This paper presents a new rasterizing algorithm with built-in capability to remove virtually all influence of the finite pixel size on lithographic performance, even for printed features down to the size less than 2 pixels. The rasterizer allows the SLM to mimic the performance of any phase-shifted reticle, including strong phase-shifting and chromeless lithography. In addition, with SLM-based mask making and maskless lithography, it is possible to switch between completely different printing modes (binary, weak and strong phase-shifting, or CPL) between consecutive exposures, without the need for reticle and wafer re-alignment. The result is improved image fidelity, smaller printed features relative to the pixel grid, and flexible powerful phase-shifting capabilities.