Impact of In Situ NH3 Preannealing on Sub-100 nm Tungsten Polymetal Gate Electrode during the Sealing Nitride Formation

概要

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We investigated the effects of in situ NH3 preannealing immediately before sealing nitride deposition on the wordline sheet resistance ($R_{\text{s}}$) of a tungsten polymetal gate electrode (W/WNx/poly-Si). While in situ NH3 preannealing is very effective for the suppression of W-O whisker formation, it was found that excessively long-time NH3 preannealing could cause an unexpectedly abnormal increase in the wordline $R_{\text{s}}$ of short gate length electrodes, typically ${<}100$ nm. Since X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS) analyses reveal that long-time NH3 preannealing results in the nitridation of tungsten sidewall surfaces, the wordline $R_{\text{s}}$ increase in a small-gate-length sample subjected to long-time NH3 preannealing is mainly due to tungsten sidewall nitridation, which is localized at the surface region of the tungsten sidewall. In addition, at a long-time NH3-preannealed gate electrode, an abnormal inflation of the tungsten sidewall occurred due to a slight increment in lattice spacing by tungsten nitridation.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2004-04-15