Dynamic bias-temperature instability in ultrathin SiO 2 and HfO 2 metal-oxide-semiconductor field effect transistors and its impact on device lifetime

Abstract

In this paper, we review our recent work on the dynamic bias-temperature instability (BTI) in metal-oxide-semiconductor field effect transistors (MOSFETs) with ultrathin SiO 2 and high-K gate dielectrics, operating in a digital inverter circuit. Key findings are: (1) For p-MOSFETs with ultrathin SiO 2 gate dielectrics, negative BTI (NBTI) is mainly due to the generation of interface traps. Under dynamic NBTI stress, the interface traps generated in the stressing phase are subsequently passivated in the passivation phase with a zero gate bias. As a result, p-MOSFET lifetime is significantly enhanced and the enhanced lifetime is frequency-independent up to 100kHz. (2) For n- and p-MOSFETs with ultrathin HfO 2 gate dielectrics, BTI is mainly caused by charge trapping in HfO 2. Similar lifetime enhancements in both n- and p-MOSFETs are observed under dynamic BTI stress. However, in contrast to SiO 2 devices, dynamic BTI in HfO 2 is strongly frequency-dependent, i.e., a high frequency results in a slight device degradation and hence a long lifetime. A physical model that accounts for two-step trapping and detrapping in HfO 2 is proposed to explain frequency-dependent BTI in HfO 2 gate dielectrics. Simulation results based on the new model shows excellent agreement with all experimental data.