Poly-Si/AlN/HfSiO stack for ideal threshold voltage and mobility in sub-100 nm MOSFETs

Abstract

A scalable poly-Si/AlN/HfSiO gate stack, implementing a new aluminum nitride (AlN) cap layer, combined with oxygen diffusion barrier, halo and counter doping engineering, high temperature spike anneal for gate and junction activation, and optional inverted gate implant, has been successfully developed to fully offset the large threshold voltage (Vt) shifts in poly-Si/HfSiO devices and achieve good thickness scalability and gate stack stability. The new AlN cap layers provide better PFET Vt control than e.g. Al2O3 layers, and can be removed from NFETs without impacting device properties. We thus have achieved sub-100 nm device V t of 0.3-0.4 V with PFETs Ion ∼ 140 μA/μm at Ioff ∼ 13 pA/μm, suitable for low-power technologies. Carrier mobilities are close to those of SiON control devices. Thus the Vt problem impeding the implementation of poly-Si/high-k gate stacks for low power device applications has been resolved. © 2006 IEEE.