Patent attributes
A workpiece chuck includes an upper assembly on which can be mounted a flat workpiece such as a semiconductor wafer. A lower assembly is mountable to a base that supports the chuck. A non-constraining attachment means such as vacuum, springs or resilient washers applied to the chuck holds the upper assembly to the lower assembly, the lower assembly to the base and can hold the wafer to the top surface of the upper assembly. By holding the chuck together by non-constraining means, the chuck layers can move continuously relative to each other under expansion forces caused by temperature effects, such that mechanical stresses on the chuck and resulting deformation of the chuck and workpiece over temperature are substantially eliminated. A plurality of support members including inclined surfaces provided between an upper and lower portion of the chuck maintain the top surface of the chuck and any workpiece mounted thereon at a constant height over temperature.
