Accurate and precise mass determination for enhanced ion beam tuning efficiency

Autotuning of beams used for ion implantation often employs time consuming peak-finding algorithms implemented to obtain maximum beam current and to ensure selection of the proper dopant species. Recently, novel autotuning and mass selection routines have been developed using a Varian VIISion ion implanter. Voltage signals from a Hall probe were calibrated to the quantity √mU/q for a variety of ion beams. Use of the calibration equation permitted a desired magnetic field strength to be calculated from the specified ion mass, charge state, and extraction voltage. This provided greater autotuning efficiency by allowing the magnet to be set to a prescribed value. Comparison of the manually tuned peak beam current to the value obtained by autotuning revealed a differential of less than 2.0%