Monitoring charging in high current ion implanters yields optimum preventive maintenance schedules and procedures

Gate to substrate charging during high current ion implantation correlates to gate oxide damage seen at product testing or during reliability assessment, as can be discovered by tedious statistical evaluations. However, variations in charging over time do not lend themselves to the same statistical analysis. Using CHARM(R)-2 to proactively monitor charging on a consistent basis over 12 months detected adverse trends before charging levels impacted yield or reliability. Variations in charging levels also correlated to preventive maintenance schedules, indicating a need to implement optimum timing and procedures. Trends for different implanters demonstrate the results of successfully implementing procedural changes, which reduced peak charging potentials and minimized equipment drift.