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A VDC bias diagnostic cathode is developed to measure the plasma-induced self bias uniformity on the wafer and the correlation to device charging damage on both 200mm and 300mm dielectric etch chambers. Multiple probe pins are buried within the ceramic electrostatic chuck surface with only the top surface tips exposed to plasma. The wafer surface DC bias voltage during the plasma process can be directly measured in-situ from these probes with built-in circuitry. The maximum bias difference (ΔVDC = VDC(max) - VDC(min)) of measured on-wafer VDC correlates to device damage during the plasma process. Comparing 200mm and 300mm chamber measurement results, the scale-up process in 300mm chamber is identified to have similar uniformity performance as in 200mm chamber. Using device calibration data compared to ΔVDC values, the plasma damage performance in both 200mm and 300mm chambers can be predicted in early chamber or process development stages.