parametric test

Parametric testing measures key electrical parameters of transistors and structures on the wafer to monitor process health and detect process shifts. **Purpose**: Verify that the manufacturing process is producing devices within specification. Early warning system for process drift or excursions. **Test structures**: Dedicated structures in scribe lines designed specifically for parametric measurement - MOS capacitors, transistors, resistors, contact chains, diodes. **Key parameters**: Threshold voltage (Vt), drive current (Idsat), leakage current (Ioff, Ig), sheet resistance (Rs), contact resistance (Rc), breakdown voltage, junction leakage, capacitance. **Measurement flow**: Probe station contacts test structure pads. Source-measure units apply voltages and measure currents. Automated recipe steps through all measurements. **WAT/PCM**: Wafer Acceptance Test or Process Control Monitor - systematic parametric measurement on every lot or wafer. **Statistical analysis**: Results tracked with SPC charts. Control limits flag out-of-specification or trending measurements. **Correlation**: Parametric results correlated with process conditions (CD, thickness, dose) to understand process-to-device relationships. **Feedback**: Out-of-spec parametric results trigger hold on lot processing, investigation, and corrective action. **Frequency**: Measured on every lot for critical parameters. Subset of parameters measured more frequently during process development. **Speed**: Fast electrical measurements (minutes per wafer). Results available quickly for process decisions. **Equipment**: Keysight, FormFactor (probe stations), Keithley/Tektronix (SMUs).