Dual-Tandem 160 kV High-Voltage Power Supply Upgrades for Ion Implantation Systems

Medium-current and high-energy ion implanters increasingly adopt dual-tandem accelerator configurations that require two independent 160 kV columns operating from a common ion source platform, demanding high-voltage systems capable of delivering ±160 kV with microampere regulation while surviving frequent spark-down events characteristic of high-energy beamlines.

Upgrade architectures replace legacy single-column supplies with dual parallel-fed multiplier stacks driven by a shared 20 kHz resonant inverter. Each column retains fully independent regulation loops with separate feedback dividers and opto-isolated control, allowing asymmetric operation for beam optics tuning while maintaining less than 12 V difference to minimize stress on intermediate electrodes. Stored energy per column is limited to 14 J through deliberate selection of low-capacitance ceramic capacitors and distributed filter networks, enabling spark recovery within 80 ms without damage to terminal components.

Spark management uses a three-stage approach: passive series resistance limits initial current to 35 A, active crowbar circuits collapse terminal voltage in under 4 µs, and a solid-state series switch isolates the multiplier stack until spark debris clears. Recovery sequences incorporate programmable delay ramps that gradually restore voltage while monitoring load current slope, preventing re-ignition that previously extended downtime to seconds.

Voltage stability during beam transport relies on active ripple cancellation. Each multiplier operates in parallel-fed mode to minimize inherent ripple, with residual 120 Hz components further reduced by injecting counter-phase current from a linear amplifier driven by a sense winding at the column entrance. Resulting terminal ripple remains below 18 V p-p even at 800 µA beam current.

Terminal grounding strategy addresses the challenge of floating the entire source platform at continuously variable potential. A dynamic grounding system uses motor-driven sliding contacts with active current balancing that maintains source-to-ground resistance below 200 kΩ while supporting ±160 kV excursion without flashover during rapid polarity reversals required for boron/phosphorus switching.

Long-term drift compensation combats resistor aging in the feedback dividers. Every 1000 hours, an automated calibration sequence injects known currents through precision resistors at the terminal and adjusts digital multiplier coefficients to nullify TCR and VCR effects, preserving regulation accuracy better than 0.02 % over five-year intervals.

Cable stabilization prevents microphonic modulation from implanter vibration. Special low-tribo coaxial cable with carbon-loaded semiconductive layers exhibits less than 8 V charge generation during 2 g mechanical shock, while active cable compensation injects opposing charge via guard electrodes driven from acceleration tube pick-off signals.

Upgrade kits incorporate backward-compatible mounting footprints and terminal connections, allowing replacement of 30-year-old supplies in under 12 hours including vacuum cycling. Post-upgrade systems routinely deliver dose uniformity improvements from 0.9 % to 0.38 % 1-sigma on 300 mm wafers at 320 keV phosphorus while reducing beam-induced sparking by 72 % through lower stored energy and faster recovery, significantly increasing tool availability in high-energy implant sectors.