All mask-related distortions must be minimized in order to meet the stringent error budgets for sub-100 nm lithography. Thermomechanical distortions during mask patterning are one source of image placement errors and may potentially consume a relatively large portion of the overlay error budget. This article investigates the thermomechanical distortions of an optical mask during electron-beam patterning. Pattern-specific distortions have been predicted for actual static random access memory layouts using numerical simulations. Finite element simulation results are presented illustrating the temperature rise and final in-plane distortion vector fields for those layouts.