14 June 1999 Wafer mapping for stepper effects characterization
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A simple technique is introduced to compare wafer flatness measured on a non-contact capacitative flatness gauge with flatness reported by a photolithography stepper. Because the capacitive gauge measures a wafer in a mechanically free state, the differences between the two types of wafer data maps represent the sets induced by the stepper. For wafers with large Total Thickness Variations (TTV), the effective stepper flatness comes close to the true metrology flatness. However, on ultra-flat wafers with very low TTVs, the stepper signature becomes more visible, which distorts the true flatness reading. Irregular wafer shape may also affect the flatness reading on the stepper due to imperfection of vacuum chucking.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yuan Zhang, Ronald A. Carpio, Lucian Wagner, Peter V. Golubtsov, "Wafer mapping for stepper effects characterization", Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350812; https://doi.org/10.1117/12.350812

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