implant dose

Implant dose is the total number of ions implanted per unit area of wafer surface, expressed in ions/cm², controlling the concentration of dopants. **Range**: Typically 10^11 to 10^16 ions/cm². Low dose for threshold voltage adjustment, high dose for source/drain and contact regions. **Dose measurement**: Faraday cup measures beam current during implant. Dose = integral of current over time divided by wafer area and charge per ion. **Accuracy**: Dose accuracy typically +/- 1-2%. Critical for device parameter matching across wafer and lot-to-lot. **Low dose** (~10^11 - 10^12): Channel and threshold voltage implants. Very light doping to fine-tune device characteristics. **Medium dose** (~10^13 - 10^14): Well implants, anti-punchthrough, halo/pocket implants. **High dose** (~10^15 - 10^16): Source/drain implants, contact implants, PAI (pre-amorphization implant). **Beam current**: Higher beam current = faster implant = higher throughput. Trade-off with beam quality and heating. **Dose uniformity**: Beam scanning and wafer motion provide uniform dose across wafer. Target <1% non-uniformity. **Sheet resistance**: Post-anneal sheet resistance (Rs) is the primary electrical verification of dose and activation. Measured by four-point probe. **Dose rate effects**: Very high dose rates can cause local heating affecting diffusion and damage accumulation.