PR-200 ion implantation system

Abstract

PR-200 is a 200-kV, general-purpose, high-throughput ion-implantation system which was installed on Western Electric’s production line at Reading, PA in mid-1975. The ’’front end’’ is a commercial Lintott mass separator to which has been added a high-current version of the Lintott–Harwell hot-cathode ion source. The front end produces 11B currents of 1 mA and 31P, 75As, and 121Sb currents of 3 mA. The ’’rear end’’ is an acceleration and rotating scan target stage based upon the PR-500 technology which was developed at this laboratory. Careful matching of the front-end slit-beam ion optics to the rear-end circular-beam optics produces high currents on target, up to 1 mA of 11B and 2.5 mA or 31P, 75As, and 121Sb. These currents, combined with fast turnaround time (5–7 min) and rotating mechanical scan, permit more than 100 3-in. wafers/h to be implated with wafer nonuniformities (1 σu) less than 0.5% and a total product nonuniformity (1 σT) less than 2.0%. The target stage floats at high voltage, and is pumped through insulating columns by a vacuum system at ground potential. Additional pumping speed is obtained by a titanium sublimation pump inside the target stage. The pumpdown sequence is automated and the implant sequence is under minicomputer control, permitting operation of the system by unskilled personnel. Communication between the high-voltage target stage and ground potential is accomplished with a four-light-beam telemetry system. Two light beams are dedicated to the rotating-scan implant and dose control, and two other light beams communicate a variety of analog, digital, and status information.