Damage-free extreme ultraviolet mask with TaBN absorber

Abstract

This article presents the results of evaluation of process-induced damage and improved reflectivity of an extreme ultraviolet (EUV) mask fabricated using a blank consisting of a multilayer, a Si capping layer, a CrN buffer layer, and a TaBN absorber. Long-term storage causes a centroid wavelength shift and stress change in the multilayer. The multilayer blank annealed at 90 °C was quite stable in centroid wavelength and film stress against resist baking at 135 °C and air storage. After the CrN buffer layer was etched with a mixture of Cl2 and O2 gases, the mask featured reflectivity loss of 1.5% due to the additional oxide layer generated on the Si capping layer. The reflectivity loss was able to be completely restored to its original value by treatment with a diluted HF solution. An EUV mask with a high reflectivity of 65% and excellent reflectivity uniformity of 0.7% 3σ was demonstrated using a blank consisting of a 40-period multilayer and a Si capping layer through a newly developed damage-free process that includes HF treatment.