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1 January 1987 Theoretical Models For The Optical Alignment Of Wafer Steppers
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A series of models are presented which enable optical alignment signals to be computed for a wide range of target structures. Scalar diffraction theory is used to describe the illumination and imaging processes and a waveguide model is used to describe the way in which the alignment target scatters light. A generalised imaging configuration is used to model four alignment systems; bright field, scanned dark field, key and target convolution and interference of the first diffraction orders. The effects on alignment accuracy of asymmetric resist flow over the target are studied as well as the effects of focus error and comatic aberration. It is concluded that bright field alignment systems are unlikely to provide the alignment accuracy required by micron and sub-micron lithography.
© (1987) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Chris P. Kirk "Theoretical Models For The Optical Alignment Of Wafer Steppers", Proc. SPIE 0772, Optical Microlithography VI, (1 January 1987);


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