Method and apparatus for mapping the edge and other characteristics of a workpiece

摘要

A method and apparatus for mapping the edge and other characteristics of a wafer. A method for mapping the edge of a wafer includes steps of providing a sensor device over a surface of a wafer on a testing chuck. A beam of electromagnetic energy emitted by the sensor device is reflected from the surface of the wafer and its intensity is measured by the sensor device. The sensor device is focussed and is then positioned at the edge of the wafer by measuring the intensity of the reflected beam as the sensor device is moved. A changed intensity signifies that the sensor device is located at the edge of the wafer. The wafer is incrementally rotated and the intensity of the reflected beam is measured at multiple locations on the edge of the wafer to provide datapoints used in the edge mapping. The height of the wafer is mapped by moving the sensor device in a z direction perpendicular to the surface of the wafer. A focal distance is found where the reflected beam is at a maximum intensity. Multiple focal distances taken from different locations on the wafer are compared to map the height of the wafer. The reflectivity of the wafer is also detected at the focal distance.