Patent ID: 7900526

Claim:
A method of classifying a non-uniformity of a semiconductor wafer, comprising the steps of: providing a semiconductor comprising a wafer having a wafer surface; providing a contact potential difference sensor having a probe tip; scanning the wafer surface laterally relative to the contact potential difference sensor; generating sensor data representative of changes in contact potential difference between the sensor probe tip and the wafer surface as the sensor probe tip scans laterally relative to the wafer surface; using the contact potential difference sensor data to detect wafer non-uniformities; processing the contact potential difference sensor data at the location of a non-uniformity by performing the steps of integrating the potential difference sensor data wherein integrated sensor data is indicative of relative surface potential, testing the integrated sensor data by performing a threshold test to identify regions of the integrated sensor data which lie within at least one of (1) in a specific range, (2) above a specified value and (3) below a specified value, thereby determining polarity at the non-uniformity and detecting a direction of change to one of lower or higher surface potential of the wafer surface; and using the direction of change to one of lower or higher of surface potential as one feature to classify the wafer non-uniformity.