Charge Trapping and Detrapping in nc-RuO Embedded ZrHfO High-k Thin Film for Nonvolatile Memory Applications

Abstract

The charge trapping and detrapping characteristics of the nc-RuO embedded Zr-doped HfO2 (ZrHfO) high-k MOS capacitor have been studied. The memory function of the capacitor is mainly contributed by hole trapping during the forward sweep from −9 V to +9 V and electron trapping during the backward sweep from +9 V to −9 V. The time- and bias-dependent stress test results show that the hole-trapping efficiency is higher than the electron-trapping efficiency due to different charge trapping sites and supply mechanisms. In order to delineate the detailed mechanisms, samples were characterized with the frequency-dependent conductance-voltage curves, relaxation currents, ramp-relax current measurements, and retention characteristics. Although most electrons are deeply trapped in the bulk nc-RuO sites, a portion of holes are loosely trapped at the nc-RuO/ZrHfO interface due to the lost of the short-term retention capability. The deeply-trapped holes and electrons were strongly held for a long period.