acceleration voltage

Acceleration voltage determines the kinetic energy of implanted ions, directly controlling how deep they penetrate into the semiconductor substrate. **Definition**: Potential difference through which ions are accelerated after mass selection. Final ion energy = charge state x acceleration voltage. **Range**: Sub-keV to several MeV depending on implanter type and application. **Low energy** (0.2-10 keV): Ultra-shallow junctions for source/drain extensions. Shallow doping profiles. **Medium energy** (10-200 keV): Well implants, channel doping, threshold voltage adjustment. **High energy** (200 keV - 5 MeV): Deep well formation, retrograde wells, buried layers. Requires tandem or linear accelerator. **Depth relationship**: Higher energy = deeper implant. Range approximately proportional to energy for given ion/substrate combination. **SRIM/TRIM**: Monte Carlo simulation software predicts implant depth profiles (range, straggle) for given ion, energy, and target. **Projected range (Rp)**: Average depth of implanted ions. Increases with energy. **Straggle**: Statistical spread around Rp. Also increases with energy. **Deceleration mode**: For very low energies, ions extracted at higher voltage then decelerated near wafer. Avoids low-extraction-voltage beam quality issues. **Energy contamination**: Must ensure no ions reach wafer at wrong energy. Charge exchange and energy contamination are potential issues.