Wafer Geometry Technique for Blank 300mm Silicon Wafers

In this paper we introduce a new optical metrology technique for measuring wafer geometry on full 300 mm blank and patterned silicon wafers. Wave Front Phase Imaging (WFPI) is presented that acquires 7.65 million data points in 5 seconds on a full 300mm silicon test wafer allowing for a lateral resolution of 96μm. The wafer geometry was measured 30 times on a blank 300mm silicon wafer front and backside while the wafer was resting on 3 pins close together and the deflection was found to be in close agreement to estimations for gravity pull. The system has repeatability with root-mean-square standard deviation (σRMS) of 4.75nm on the front side and 6.51nm on the backside of a 300mm silicon test wafer. Using a double Gaussian filtering technique with a 100μm lateral cutoff frequency, nanotopography was revealed on the full silicon wafer showing a repeatability of 0.265Å for the frontside and 0.204Å for the backside of the full 300mm silicon wafer.