Abstract: A transfer arm assembly for transferring wafers between a load-lock chamber or a transfer chamber and processing chamber. The wafer is selectively held on the end of a paddle. Linear horizontal motion is provided by a drawer-slide mechanism including a base, a carriage, and the paddle. Slides are mounted on the base and on the carriage. Wheels mounted on the carriage slidably engage the base slides and support the carriage on the base, and wheels mounted on the paddle slidably engage the carriage slides and support the paddle on the carriage. Thereby, the paddle may be projected a distance greater than the lateral extent of the base or of the vacuum chamber accommodating the base and its supported components in their retracted positions. A single motor mounted on the carriage can provide the two relative motions among the base, carriage, and paddle by means of two belt mechanisms wrapped around two capstans attached to the motor shaft.