Bias Temperature Instability in Semiconductor Devices

Bias Temperature Instability (BTI) is a pervasive ageing phenomenon in metal-oxide-semiconductor field-effect transistors (MOSFETs), manifesting as a gradual shift of the threshold voltage under prolonged gate stress at elevated temperatures. In p-channel devices, negative BTI (NBTI) arises under negative gate bias, while in n-channel devices positive BTI (PBTI) occurs under positive bias. Both processes are driven by the generation of defects within the gate dielectric or at the semiconductor–dielectric interface, leading to charge trapping and the formation of oxide traps. At the nanoscale these effects can proceed in discrete steps corresponding to single-defect capture and emission events, observed as Random Telegraph Noise (RTN). Over device lifetime BTI can degrade switching speed, increase power consumption and lead to circuit failure, making its accurate modelling and prediction vital for the reliability of modern integrated circuits. Research efforts focus on elucidating the underlying physical processes, developing predictive models that account for defect kinetics under dc and ac stress, and devising mitigation strategies such as dynamic bias adaptation and material engineering to extend device longevity.

Research from Nature Portfolio

Recent studies have employed high-resolution charge sensing at low temperatures to dissect RTN behaviour in advanced transistors. One work has demonstrated that RTN can be induced by resonant tunnelling through parasitic single-hole transistors, enabling systematic identification of trap locations via bias-dependent measurements. Another investigation has revealed a four-state trap model in high-κ dielectrics, providing direct evidence of metastable configurations of single oxide traps and their contribution to anomalous RTN. These findings offer critical insights into the microscopic defect states that govern BTI kinetics and support the refinement of defect-centric reliability models.

Bias Temperature Instability in Semiconductor Devices publication trend

The graph below shows the total number of articles in bias temperature instability in semiconductor devices across all publications each year (not limited to Nature Index journals).

Technical terms

Bias Temperature Instability (BTI): Threshold voltage shift in a MOSFET under prolonged gate bias at elevated temperature.

Negative BTI (NBTI): BTI occurring under negative gate bias in p-channel MOSFETs, leading to hole trapping.

Positive BTI (PBTI): BTI occurring under positive gate bias in n-channel MOSFETs, associated with electron trapping.

Random Telegraph Noise (RTN): Discrete two-state current fluctuations caused by single defect charge capture and emission.

Oxide trap: A defect site within the gate dielectric or at the interface that can capture charge carriers and alter device characteristics.

Threshold voltage (Vth): The gate voltage at which a conductive channel forms between source and drain in a MOSFET.

References

1. Random telegraph noise from resonant tunnelling at low temperatures. Scientific Reports (2018).
2. Anomalous random telegraph noise in nanoscale transistors as direct evidence of two metastable states of oxide traps. Scientific Reports (2017).
3. As-grown-Generation Model for Positive Bias Temperature Instability. IEEE Transactions on Electron Devices (2018).
4. Bias Temperature Instability of MOSFETs: Physical Processes, Models, and Prediction. Electronics (2022).
5. Comphy v3.0—A compact-physics framework for modeling charge trapping related reliability phenomena in MOS devices. Microelectronics Reliability (2023).