EUV pellicle with very thin thickness is significantly affected when external forces are applied. The mechanical forces
such as chamber-pellicle pressure difference and stage acceleration cause the mechanical stress in pellicle. We
investigated the maximum stress that can be induced by the pressure difference for various materials by using finite
element method (FEM). We also used theoretical model and FEM for predicting the pellicle deformation. Our results
show the mechanical deformation and the stress of full size (152 × 120 mm<sup>2</sup>) pellicle with 50 nm thickness, and the
influence of the pellicle is increased with larger pressure difference. We also studied the maximum stress caused by the
acceleration force of the scanner. The full size pellicle is greatly influenced with the specific pulse width causing
resonance. Our study indicates that mechanical stress with acceleration is very small and can be ignored.