Abstract
Ring-seal pin chucks are currently used in many lithography machines. It is known that a ring seal causes local wafer deformation due to vacuum, and that a polishing step of more than 20 nm occurs between pins and the ring seal. This paper describes the local deformations, above a lift hole and a ring seal around the chuck periphery, and the influence of the step on wafer flatness. The local deformations were calculated using FEM. It was clarified that they are caused due to the penetration of the pin into the back surface of a wafer and the compressive deformation of the fine pin, and that the influence of the steps on wafer flatness is very large. In addition, It was clarified that the site flatness for the next-generation device may be achieved using a static-pressure-seal-type pin chuck with a pitch of 1 mm.
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