Effects of $\hbox{Al}_{2}\hbox{O}_{3}$ Dielectric Cap and Nitridation on Device Performance, Scalability, and Reliability for Advanced High- $\kappa$/Metal Gate pMOSFET Applications

A pFET threshold-voltage (
Vt
) reduction of about 200 mV is demonstrated by inserting a thin Al
₂
O
₃
layer between the high-k dielectric and the TiN gate without noticeable degradation of other electrical properties. HfSiO
_prop
capped with 9 Aring of thin Al
₂
O
₃
obtains a low long-channel V
t
of -0.37 V (the lowest among those with TiN gate), a high mobility of 59 cm
²
/V ldr s at 0.8 MV/cm (92% of universal value), a negligible equivalent- oxide-thickness (EOT) increase of 0.1 Aring (compared to the uncapped 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 thin Al
₂
O
₃
obtains caps are beneficial to the pFET applications. In contrast, nitrogen incorporation in the Al
₂
O
₃
-capped HfSiO
_prop
is not favorable because it increases the Vt by 50-140 mV, degrades the mobility by 10%-22%, increases the EOT by 0.5-0.8 Aring and the Vt instability by 5-13 mV, and reduces the NBTI lifetime by four to five orders of magnitude. Compared to postcap nitridation, high-k nitridation results in more severe degradation of these properties by incorporating nitrogen closer to the Si/SiO
₂
interface.