Wafer flatness: An overview measurement considerations and equipment correlation

This study has shown that reliable and repeatable flatness measurements are possible and that data gathered through measurements on different types of equipment correlates within .5 microns. But some important equipment variables which affect flatness readings must always be considered. These include methods used for providing reference plane, particulate contamination, chuck geometry, vacuum distribution system, and clamping vacuum. If careful attention is given to these factors, industry-wide flatness correlation will become possible.