Soft-handed vacuum chuck

A new soft-handed vacuum chuck has been developed to allow the precise measurement of the placement accuracies of X-ray masks and wafers, which are deformed by stresses in processes, because it is difficult to clamp them without deformation. This chuck is characterized by three vacuum pinpads. The pinpads make it possible to prevent lateral movement and a vacuum seal. Thus, a lateral clamping force bearing an acceleration of 0.3 g and clamping without deformation have been achieved. This chuck was used with a NIKON 3I laser interferometry coordinate-measuring machine allowing the placement accuracies of an X- ray mask and a reticle to be measured with good repeatability at less than 30 nm (3 (sigma) ).