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

Japanese Journal of Applied Physics 43(4S) 1829

https://doi.org/10.1143/JJAP.43.1829

Kwan-Yong LIM, Jung-Ho LEE, Heung-Jae CHO, Jae-Geun OH, Byung-Seop HONG, Se-Aug JANG, Yong Soo KIM, Hong-Seon YANG and Hyun-Chul SOHN

Abstract

We investigated the effects of in situ NH3 preannealing immediately before sealing nitride deposition on the wordline sheet resistance (Rs) 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 Rs 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 Rs 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.