Validation of ArF PSM quality using AIMS simulation method inrepeated cleaning

摘要

Since the haze generation causes unexpected wafer yield losses, it has been a serious issue on wafer lithography as illumination wavelengths become shorter with 248nm and 193nm. Several papers regarding to cleaning and its effect on haze generation have been published. A mask is cleaned periodically to prevent from the haze generation. These periodic or repetitive cleanings causes unacceptable phase and transmittance variation. Therefore, the number of cleaning cycles has been limited to meet limitation of phase and transmittance.In this paper, relaxation for pass or fail criteria was studied based on phase and transmittance margin, as one of the solutions of cleaning limitation. Optimum cleaning cycles were determined by using AIMS (Aerial Image Measurement system) simulation methods. Various parameters such as phase and transmittance variation, depth profile, intensity, CD (Critical Dimension) with line and space and contact pattern of pre and post cleaned ArF PSM were measured whenever a mask was cleaned repeatedly. Moreover, a mask quality was validated based on the measured parameters, considering limitation of phase and transmittance and lithography margin. The cleaning and validation were repeated several times until intensity and CD were out of limitation. Based on these studies, a correlation model between the numbers of cleaning cycles and measured parameters from AIMS simulation were developed. The newly developed correlation model was used for an estimating parameter for the optimum number of cleaning cycles to be performed.