MOSFET BTI Threshold Aging Calculator
Advanced CMOS Reliability: Model Negative/Positive Bias Temperature Instability (NBTI/PBTI) threshold voltage degradation (ΔV_th) over time, temperature, and gate electric field.
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Threshold Voltage Drift & Lifetime Projection
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Bias Temperature Instability (BTI) in Advanced Nodes
BTI aging is the principal wear-out mechanism dictating 10-year circuit longevity in CPUs, GPUs, and smartphone SoC processors, causing gradual clock frequency degradation and SRAM cell read/write failures.
1. Reaction-Diffusion Power Law Model
Threshold voltage degradation over operating time is expressed as:
ΔV_th = A · exp( γ · E_ox ) · exp( -E_a / (k_B · T) ) · t^n
where $E_{ox}$ is oxide electric field, $E_a$ is activation energy (0.10 to 0.20 eV), and $n$ is the time exponent.
Frequently Asked Questions
What is Negative Bias Temperature Instability (NBTI)?
NBTI occurs in pMOSFETs stressed with negative gate voltage at elevated temperatures. High oxide electric fields break trivalent silicon-hydrogen (Si-H) bonds at the Si/SiO2 interface, releasing neutral hydrogen species that diffuse into the gate oxide, generating positively charged donor-type interface traps that shift threshold voltage (|ΔVth|) and reduce drain current.
Why does Positive Bias Temperature Instability (PBTI) become severe with High-k Metal Gates?
In traditional SiO2 gate oxides, PBTI in nMOS was negligible. However, in advanced nodes utilizing hafnium-based high-k gate dielectrics (HfO2), oxygen vacancies and pre-existing trap states in the bulk high-k layer capture conduction band electrons under positive gate bias, causing substantial positive threshold voltage shifts.
What is the physical significance of the fractional time exponent n ≈ 0.16–0.25?
The sub-linear power law growth ($t^n$) reflects the Reaction-Diffusion (R-D) mechanism of hydrogen transport through the disordered gate oxide matrix, where dispersive hopping between trap sites leads to anomalous sub-diffusion.