New metrology technique for measuring patterned wafer geometry on a full 300mm wafer

The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing1. Chemical-Mechanical Planarization (CMP) is one of many processes outside the lithographic sector that will influence wafer flatness across each image lithographic exposure section field and across the wafer2. Advanced lithographic patterning processes require a detailed map of the wafer shape to avoid overlay errors caused by depth-of-focus issues1. In recent years, a metrology tool named PWG5TM (Patterned Wafer Geometry, 5th generation), based on using double Fizeau interferometry to generate phase changes from the interferometric pattern applied to the reflective surface, has been used to generate a wafer geometry map to correct for process induced focus issues as well as overlay problems2. In this paper we present Wave Front Phase Imaging (WFPI); a new patterned wafer geometry technique that measures the wave front phase utilizing two intensity images of the light reflected off the patterned wafer. We show that the 300mm machine acquires 7.65 million data points in 5 seconds on the full 300mm patterned wafer with a lateral resolution of 96μm.