Strategy of DoseMapper (DoMa) Application and Monitor for Critical Dimension Uniformity (CDU) Control in Sub-45nm Gate Process

Abstract

As the industry enters 45/40 nm technology node and beyond, the effective control of polysilicon gate's critical dimension uniformity (CDU) becomes more important to device performance. However, to achieve good uniformity is very challenging since the CDU has shown high sensitivities to the variations from resist track recipe, scanner variation, and etcher. It is well known, the DoseMapper (DoMa) is a highly effective tool for the improvement of CDU. In this paper, we will focus on the set up of a DoMa application and monitor system for 40 nm poly gate CDU improvement. Through the use of a state of the art immersion exposure tool (ASML 1900Gi), a DoMa application can successfully improve a gate across wafer CDU by 49% in 40 nm node. In addition, DoMa is more effective when it is applied at post-etch stage than at post-litho stage because it can cover the systematic etch CD variation. However, when a DoMa recipe is applied at post-etch stage, at post-litho, the CDU is no longer meaningful. Before the wafer is etched, we need a new metric to monitor the DoMa performance. A new DoMa monitoring system by RSQ function at post-litho has been introduced and the result will be presented in this paper, which can monitor CD map change by SPC (Statistics Process Control) alarm function.