This invention relates to a substrate support
assembly for a substrate support device. The invention is characterized by comprising: a chuck base supporting the substrate to be processed, having a housing portion formed along the circumferential direction near its outer
peripheral surface, and an upwardly opening receiving groove formed in the inner portion surrounded by the housing portion, capable of rotation about a rotation axis; a chuck pin disposed on the upper part of the housing portion of the chuck base, movable in directions away from and towards the substrate; a device portion disposed within the housing portion and connected to the chuck pin for moving the chuck pin; a drive portion for transmitting power to the device portion; and an ultrasonic cleaning unit housed in the receiving groove. The device portion is centrally disposed within the housing portion formed along the circumferential direction near the outer
peripheral surface of the chuck base, and the ultrasonic cleaning unit is housed in the central receiving groove. Therefore, it can have the functional effect of cleaning the back side of the substrate using an ultrasonic
generating unit.