Mechanical analysis of the PLASMAX particle removal process for optical and next-generation lithography masks

Abstract

The ability to clean advanced lithographic masks in a cost-effective manner is becoming increasingly important as the semiconductor industry continues integrated circuit development with ever-decreasing feature sizes. The plasma mechanical activation and extraction of particle contamination (PLASMAX) particle removal process, under development by Beta Squared, Inc., provides a means to achieve the industry’s needs for both the current optical and next-generation lithography (NGL) masks. This cleaning procedure is imperative since all NGL technologies are unable to use a conventional protective pellicle. The cleaning process implements a charged plasma flow in conjunction with mechanical excitation. This article presents the results of research to identify the optimal procedures to mechanically oscillate 6 in. fused silica reticles and electron-beam projection lithography masks. Using both numerical and experimental methods, the analysis characterizes the dynamic response of lithographic masks to quantify and optimize the mechanical force delivered to a surface contaminant in the PLASMAX process. These modeling and simulation efforts are essential to support the experimental program and facilitate development of the cleaning process for advanced optical reticles and NGL masks.