Simple method for decreasing wafer topography effect for implant mask

Abstract

Controlling critical dimension (CD) of implant blocking layers during photolithography has been challenging due to reflection caused by wafer topography. Unexpected reflection which comes from wafer topography makes severe CD variation on mask patterns of implnat layer. Using bottom antireflective coatings(BARCs) can reduce the topography effect, but it could also damage wafer surface during BARCs dry etching. Developable BARCs(D-BARCs) could be alternative solution for wafer topography effect. However there are some issues that should be considered in D-BARCs process such as sensitive temperature control and managing defects. There are also papers introducing model based topography aware OPC as a solution for wafer topography effect implant layer. But building topography aware OPC model is very complex and it takes too much time to build.In this paper, we will introduce experimental results of wafer topography effect using various test patterns and propose a simple method that could effectively reduce wafer topography effect.