Low Thermal Expansion Material (LTEM) Cleaning and Optimization for Extreme Ultraviolet (EUV) Blank Deposition

With the insertion of extreme ultraviolet lithography (EUVL) for high-volume manufacturing (HVM) expected in the next few years, it is necessary to examine the performance of low-thermal e expansion mat materials (LTEMs) and assess industry readiness of EUV substrates. Owing the high cost of LTEM, most of the development work so far has been done on fuse silica substrates. Especially in developing cleaning technology prior to multilayer deposition, fused silica substrates have been used extensively, and defect trends and champion blank data have been reported us sing multilayer deposition data on fused silica substrates. In this paper, the response of LTEMs to cleaning processes p prior to multilayer deposition is discussed. Cleaning processes discussed in this paper are developed using fused silica substrates an applied on LTEM substrates. The defectivity and properties of LTEM to fused silica are compared. Using the den scan feature of the substrate inspection tool capable of detecting defects down to 35 nm SiO2 equivalent size and appropriate defect decoration techniques to decorate small mall defects on substrates to make them detectable cleaning technologies that have the potential to meet high de demands on LTEM for EUV are developed and optimized.