Scanned beam uniformity control in the VIISta 810 ion implanter

The VIISta 810 is Varian's new 200 mm/300 mm serial medium current ion implanter. Scanning of the beam in the horizontal direction over the required distance is achieved through the use of an electrostatic deflector operating at 1 kHz. Horizontal uniformity is achieved by iterative adjustment of the scanning waveform. A 45/spl deg/ angle corrector magnet then makes the beam parallel. Vertical uniformity is achieved by a mechanical scan of the wafer. Data presented in this paper illustrate the machine's 300 mm performance as measured by a travelling Faraday cup in the plane of the wafer. Low energy beams can be focused by the scanner, improving beam transmission to the wafer. Enhancements in low energy beam current by applying a negative DC offset voltage to the scan plates are described.