Effects of Al2O3 dielectric cap and nitridation on device performance, scalability, and reliability for advanced high-k/metal gate pMOSFET applications
Chang, Vincent S × Ragnarsson, Lars-Ake Yu, Hong Yu Aoulaiche, Marc Conard, Thierry Yin, KaiMin Schram, Tom Maes, Jan Willem De Gendt, Stefan Biesemans, Serge #
Ieee-inst electrical electronics engineers inc
Ieee transactions on electron devices vol:54 issue:10 pages:2738-2749
A pFET threshold-voltage (V-t) reduction of about 200 mV is demonstrated by inserting a thin Al2O3 layer between the high-kappa, dielectric and the TiN gate without noticeable degradation of other electrical properties. HfSiOx capped with 9 A of Al2O3 obtains a low long-channel Vt of -0.37 V (the lowest among those with TiN gate), a high mobility of 59 cm(2)/V center dot s at 0.8 MV/cm (92% of universal value), a negligible equivalent-oxide-thickness (EOT) increase of 0.1 A (compared to the un-capped reference), and a low Vt instability of 4.8 mV at 7 MV/cm. It also passes the ten-year negative-bias-temperature-instability (NBTI) lifetime specification with a gate overdrive of -0.7 V. This indicates that Al2O3 caps are beneficial to the pFET applications. In contrast, nitrogen incorporation in the Al2O3-capped HfSiOx. is not favorable because it,increases the Vt by 50-140 mV, degrades the mobility by 10%-22%, increases the EOT by 0.54.8 A and the V-t instability by 5-13 mV, and reduces the NBTI lifetime by four to five orders of magnitude. Compared to postcap nitridation, posthigh-kappa nitridation results in more severe degradation of these properties by incorporating nitrogen closer to the Si/SiO2 interface.