Influence of heat-induced changeable stiffness at the contact interface on the gripping force of a bipolar electrostatic chuck

Abstract

A bipolar electrostatic chuck is a gripping device suitable for handling thin and flexible objects such as semiconductor wafers, glass and polymer films. Existing studies mainly focused on increasing the gripping force, such as smoothening the contact surface of the device. However, handling methods that include not only grasping, but also releasing of objects have not been developed. This study verifies the effect of the changeable stiffness at the contact interface on the grasping and releasing of an object handled using a bipolar electrostatic chuck. For object handling, efficient grasping and releasing are two fundamental functions needed of any gripping device. To ensure a smooth pick-and-place process, a significant difference between the maximum (grasping) and minimum gripping force (releasing) is desired. Thus, this study proposes a bipolar electrostatic chuck with changeable stiffness at the contact surface. The bipolar electrodes act as heaters, allowing the stiffness of the surface to be controllable by adjusting their temperature. For grasping, by decreasing the stiffness, a closer contact with an object can be achieved and the chuck’s maximum gripping force can be increased. Furthermore, during releasing, the chuck is expected to detach away from the object easily.