Analysis of the post-breakdown current in HfO_2/TaN/TiN gate stack MOSFETs for low applied biases

摘要

A thorough analysis of the post-breakdown current-voltage characteristics in HfO_2 high-κ/TaN/TiN gate stacks for low positive applied biases reveals an apparent band gap narrowing of the silicon substrate at the very location of the leakage site. This effect may be caused by the migration of gate material through the percolation path during the breakdown runaway. Additionally, the voltage dependence of the current suggests that the origin of the leakage current is thermal generation within the depletion region close to the breakdown spot. A simple analytical model to deal with this current is proposed.