Improved n-channel Ge gate stack performance using HfAlO high-k dielectric for various Al concentrations

Abstract

We demonstrate improved Ge n-channel gate stack performance versus HfO2 using HfAlO high-k dielectric for a wide (1.5–33%) range of Al% and post-high-k-deposition annealing (PDA) at 400 °C. Addition of Al to HfO2 is shown to mitigate degradation of the GeO2/Ge interface during PDA. HfAlO stacks with an equivalent oxide thickness (EOT) of 8 nm and large Al% exhibit improved transistor mobility (1.8 times higher) and midgap Dit (2 times lower), whereas thin (1.9 nm) EOT HfAlO stacks show reduced gate leakage Jg (by 10 times) and Dit (by 1.5 times) and 1.6 times higher mobility for Al% as low as 1.5% at matched EOT.