Theoretical Studies of Interface-State Generation in Silicon Mosfet's Using AN Ensemble Monte Carlo Method.
In this thesis hot electron injection and interface -state generation in silicon MOSFET's are investigated theoretically. To accomplish this study, we developed an ensemble Monte Carlo simulator suitable for examining the high energy tail of the electron energy distribution. The model includes all relevant details for carrier transport, such as a realistic silicon band structure (two band pseudopotential), interactions with phonons, electrons (both local and non-local), ionized impurities, a SOR Poisson solver, and statistical enhancement calculations. This work accurately predicts the quantity and lateral distribution of hot electron transport induced interface states in a silicon MOSFET using a coupled Monte Carlo/interface-state generation model. The calculations explore the sensitivity of the electron energy distribution to impact ionization coefficients, self-consistent electron -electron calculations, and surface scattering. The modeled interface-state distribution agrees with charge pumping measurements and predicts that the interface state generation extends spatially beyond the range where charge pumping measurements have been published. The study continues to apply these techniques to 0.33-, 0.20-, and 0.12-μm channel -length devices scaled by constant field and more generalized methods. Applied bias and electric field dependency were investigated. Hot-electron injection and interface-state density profiles were simulated at biases as low as 1.44 V with channel lengths as low as 0.12-mu m. These simulations demonstrate reasons that "lucky electron" or electron temperature models are no longer accurate for predicting hot-electron effects in such regimes. Electron -electron scattering is shown to be a critical consideration for simulation of hot-electron injection in low drain to source bias voltages. As expected, simulations indicate the lateral electric field may be increased with each scaling generation for an equivalent hot-electron injection. It is also shown that conventional hot-electron stressing using accelerated bias stressing continues to be valuable for drain to source biases as low as 1.44 V.
- Pub Date:
- January 1995
- Physics: Condensed Matter; Engineering: Electronics and Electrical