0.13μm BiCMOS emitter window lithography with KrF scanners

Defining the emitter window is one of the most critical lithographic steps in a BiCMOS process. Step-and-scan exposure tools are typically the largest component of fixed capital expense so the industry is constantly trying to push the resolution limit without purchasing new equipment. As the industry extends KrF scanner to 0.13μm BiCMOS process, the lithography process window of shallow trenches patterns which are typical for emitter windows will be challenged. Generally speaking, printing these patterns with conventional single exposure methods will suffer from lack of sufficient process window and severe line-end shortening. In this paper, we present a method that uses KrF scanners and several resolution enhancement techniques including attenuated phase shift masks (att-PSM), model-based optical proximity correction (MbOPC), and a multi-focal exposure technique, to improve the process window of 0.13μm emitter window features. Characterization results are shown for the process window, side lobe printability margin, and line-end shortening. Comparisons are made to a traditional exposure method. The results demonstrate a significant increase in depth of focus as well as improvements in line-end shortening and intra-wafer CD uniformity.