STENCIL MASK DISTORTION CONTROL USING NONSYMMETRIC PERFORATION RINGS

For ion beam projection lithography to be successful in the 0.13 mu m regime, it is essential to understand and control the sources of disto rtion in the stencil mask. This paper reports on the use of circumfere ntial perforation rings to reduce the initial membrane prestress and s ubsequent pattern distortions. Using finite element methods, optimizat ion studies have been performed to identify the necessary design param eters. The use of nonsymmetric perforations rings to corrects for diff erences in membrane stiffness due to anisotropic pattern features is d emonstrated. Pattern perforations are also shown to alter vibration mo de shapes and frequencies, influencing membrane dynamic response.