Large depth-of-field microscopes are capable of acquiring clear images at different focal planes,providing strong support for wafer alignment.To extend the depth of field,researchers have proposed a variety of techniques,including reducing the system aperture,wavefront encoding,and optical toe-cutting.In this paper,a new method to extend the depth of field is proposed,i.e.,bifocal objective lens alignment,which is simple and intuitive to operate and allows direct acquisition of alignment markers to achieve alignment,thus greatly improving the accuracy and efficiency of alignment.These techniques and methods lay a solid foundation for the subsequent research of large depth-of-field microscopy.
Integrated circuit manufacturingMicroscopyLarge depth of fieldBifocal objective lens alignment
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