Temperature rise of extreme ultraviolet lithography mask substrate during dry etching process

Experiments and numerical calculations were performed to investigate the dry etching heating of mask substrate. Changes of the glass substrate temperature were observed by color changes of a heat-sensitive label pasted on the substrate. A simulation model based on a lumped heat capacity system was proposed to investigate the heat transfer mechanism at the contact interface between the mask and the stage or carrier. When thermal radiation dominates the heat transfer mechanism between the mask and the stage, a temperature rise of about 100°C was observed and predicted for an etching time of 60s. The heating of mask substrate cooled by the stage indicated a temperature rise less than 43°C. The cause of mask substrate temperature rise was found to be insufficient adhesion between the mask and stage. Estimation of thermal response of a 150-mm square standard glass substrate with a thickness of 6.5 mm was attempted using the simulation model based on the experimental results. The dry etching of the mask substrates was found to be a practicable and safe thermal process if the etching time is within 60 s.