Effects of wafer bow and warpage on the integrity of thin gate oxides

Abstract

We have studied the effects of initial wafer bow and warpage on the integrity of thinner gate oxides grown by both furnace and rapid thermal processing (RTP) methods. There is evidence of a correlation between wafer warpage and bow to the charge-to-breakdown characteristics of the gate oxide. An almost linear increase in defect density was observed when plotted as a function of increasing wafer warpage. The lifetime (t50%) of the samples with initial warpage of 10 μm or less is reported higher than those with initial warpage of more than 60 μm for both furnace and RTP-grown oxides. The value of bow for the warped samples was taken for cases with the highest positive and negative values so both kinds of shape trends could be investigated. With initial wafer warpage ranging from 4 to 70 μm, we present the results of wafer dimensional analysis and correlate these to defect density and lifetime studies for thin gate oxides.