a method and apparatus for rotating wafers in a double sided scrubber without slipping or hesitating . a rotating roller imparts rotary motion to a semiconductor wafer during a double sided cleaning process . the rotating roller and wafer contact at their outer edges and the friction between their outer edges causes the wafer to rotate . the roller has an outer edge with a groove . the wafer edge is pinched inside the groove to create enough friction that when cleaning solutions are applied the wafer does not slip and continues to rotate . also , the groove allows the roller to pinch the wafer just enough so that when the roller reaches the flat of the wafer , the roller may regain the radius of the wafer without hesitating .