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2011
Journal Article
Title
Gate oxide reliability at the nano-scale evaluated by combining cAFM and CVS
Other Title
Auswertung der Zuverlässigkeit von Gateoxiden im Nanomassstab durch Kombination von cAFM und CVS
Abstract
The gate oxide integrity of different thin films (silicon dioxide, silicon nitride and hafnium oxide) was analyzed by constant voltage stress (CVS) at the nano-scale using conductive atomic force microscopy (cAFM) with the probe tip directly in contact to the dielectric layer. The results were evaluated assuming a Weibull failure distribution for the dielectrics under voltage stress, and a good fit was obtained for the measurement data. This indicates that CVS measurements at the nano-scale can be applied for inline characterization of as-deposited dielectrics without the need of gate electrodes. Additionally, time-to-breakdown extracted from the CVS using cAFM was compared to data retrieved from CVS measurements using conventional current-voltage measurements on samples with gate electrod es. In particular, area scaling of CVS data over eight orders of magnitude using cAFM was performed for the first time. The evaluation indicates a decent match between macroscopic and nano-scale CVS measurements for the hafnium oxide and silicon dioxide samples. In contrast, significant discrepancies are evident for the silicon nitride samples which may be related to charge trapping effects.