Characterization of high-k/metal gate stack breakdown in the time scale of ESD events

Abstract

Catastrophic gate oxide breakdown of MOSFETs with high-k gate was characterized under ESD-like pulsed stress. It was found that the excessive gate current after gate oxide failure may result in a loss of gate contact and form a resistive path between the drain and source. Using constant voltage stress (CVS) method, the gate oxide breakdown voltages (VBD) of NMSOFETs and PMOSFETs were extracted. NMOSFETs under positive stress were found to have the smallest VBD, while the VBD of the PMOSFETs under positive stress were significantly increased due to the well resistance. Compared to that measured using the CVS method, the VBD from the transmission line pulse method (TLP) was smaller by only less than 10%. Despite the cumulative damages caused by the TLP method, the result is a conservative estimation of the breakdown voltage. The VBD corresponding to the failure time of 1-ns measured using TLP method agrees well with the extrapolation result from the CVS measurements on the time scale ranging from ∼100 ns to ∼20 μs, suggesting that the failure mechanism remains the same as in the longer time scale. © 2010 IEEE.