Abstract: An apparatus for cleaning semiconductor wafers includes a tank for containing a liquid and receiving a wafer holder with at least a portion of the wafers immersed in the liquid in the tank. A sonic energy generator imparts sonic energy to the liquid. A wafer-moving mechanism in the tank reciprocates and rotates the semiconductor wafer so that at least a portion of the wafer repeatedly passes through an upper surface of the liquid. The wafer-moving mechanism comprises a camming mechanism rotatably received in the tank and a drive for rotating the camming mechanism about a fixed central longitudinal axis of the camming mechanism to reciprocate and rotate the wafer. The camming mechanism includes a cam body having opposing flats spaced apart on opposite sides of its longitudinal axis and opposing gripping surfaces extending between the flats. The cam body has a cross-section defining a major axis and a minor axis, with the major axis of the cam body cross-section being greater than the minor axis.