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.