Pattern-specific emulation (PSE) for ion-beam projection lithography masks using finite element analysis

Abstract
Pattern specific emulation (PSE) may be required for ion- beam projection lithography to meet the high pattern placement requirements in the sub-0.13 micrometers regime. To effectively employ PSE, it is necessary to simulate the distortion of the stressed mask membrane due to the fabrication of the stencil void pattern. Equivalent modeling techniques have been developed to determine both global and local in-plane distortions (IPD) using finite element (FE) methods. IPD is calculated by first dividing the patterned area of the membrane into subregions of equivalent void fraction. These subregions are based upon the percent void fraction as well as the pattern geometry. For each subregion, a set of equivalent elastic constants are used as input into the FE model to represent the stiffness of the actual perforated membrane. Global distortions are then computed to simulate the pattern transfer process. In this paper, a verification test case for equivalent modeling and an example of PSE for a complete mask pattern are presented.

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