A technique for optimizing the dose uniformity of a magnetic scanning high current implanter

Magnetic scanning high current implanters pose a unique challenge to achieving the wafer doping uniformity that is typical of serial implant, lower current machines. Precise control of the beam centroid location over the spinning disk is essential to the achievement of good wafer uniformity, as evidenced by machine performance and computer simulation. A technique has been developed on the Varian/Extrion 120-10 to obtain this control as well as compensate for any machine aberrations to improve the dose uniformity over a wide range of implant conditions. This technique uses the machine computer system and the actual implanted wafer resistivity data to determine an improved functional dependence of the scan rate with beam location. Subsequent implants are then run with this compensated scan rate information. Successful use of this technique at the 1% level will be demonstrated for 100, 125 and 150 mm wafers. (orig.)