Temperature Effects of Constant Bias Stress on n-Channel FETs with Hf-based Gate Dielectric

概要

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Temperature dependence of degradation and breakdown behavior of hafnium silicate gate dielectrics in n-channel field-effect transistors (NFET) with polysilicon and TiN gate electrodes has been investigated. At elevated temperatures under positive gate bias, devices with polysilicon gate electrodes exhibit a so-called $V_{\text{th}}$ turn around phenomenon (a change of the direction of the $V_{\text{th}}$ shift from positive to negative), accompanied by decreasing transconductance and increasing gate leakage current. Hot-holes generation in the poly-Si gate by the injected electrons and a subsequent hole diffusion and trapping near the high-k/Si-substrate interface is proposed to contribute to the turn around behavior. No $V_{\text{th}}$ turn around phenomenon was observed in devices with the TiN gate electrode. This hole induced degradation of the high-k/poly-Si gate stack may further complicate integration of the polysilicon gate electrode with high-k dielectrics.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-04-15