Application of fast wafer-level reliability PBTI tests for screening of High-k / Metal Gate process splits

This work shows how fast wafer-level reliability (fWLR) inline tests allow to quickly screen the intrinsic reliability of high-k/metal gate (HK/MG) process splits in an effective manner. Various Hf based gate stack compositions such as pure HfO₂, Hf_xZr_1-xO₂ and Hf_xSi_1-xO₂ are investigated from a reliability point of view. The main focus lies on PBTI (positive bias temperature instability) which is one of the most critical reliability concerns in current HK/MG stacks. As a key result, PBTI was found to improve when doping the HfO₂ with either silicon or zirconium. Since HK/MG technology also introduces more process parameters to be controlled, it is shown that with fWLR tests implemented in a wafer electrical test environment their influence on reliability can be evaluated much faster than with standard lab approaches.