Effects of postdeposition annealing on a high-k-last/gate-last integration scheme for 20 nm nMOS and pMOS

The authors report the use of postdeposition annealing (PDA) to improve the performance of a high-k (HK)-last/gate-last integration scheme involving the use of a chemical oxide interfacial layer (IL). They find that the chemical oxide IL can form Hf-silicate at the HK/IL interface to provide a larger effective k value and a smaller equivalent oxide thickness. They also find that they can achieve a small gate leakage current density (Jg) and minimal flat-band voltage (Vfb) degradation by PDA in O2 atmosphere. Furthermore, they find that Jg and Vfb can be further improved by optimizing the metal gate stack.