Patent ID: 8275564

Claim:
In a method of inspecting a surface of a material that contains a repeating pattern of relative work functions for detecting non-uniformities in the pattern, comprising the steps of: providing a surface of a material; providing a non-vibrating contact potential difference sensor having a sensor probe tip; positioning the sensor probe tip a fixed distance above the surface of the material; continuously moving the surface and non-vibrating contact potential difference sensor relative to one another so that the probe tip moves parallel to the surface of the material; generating non-vibrating contact potential sensor data arising from the continuous motion of the sensor probe tip relative to the surface of the material, the sensor data representative of changes in contact potential difference between the sensor probe tip and the surface of the material; the improvement characterized by the steps of processing the sensor data to provide relative contact potential difference values; identifying relative contact potential difference data characteristic of the repeating pattern; processing the relative contact potential difference data to reduce effects of data characteristic of the repeating pattern and providing resulting data; and processing the resulting data to identify work function non-uniformities that are not part of the repeating pattern.