Device Simulation

Device Simulation
Overview

Device simulation uses numerical methods to solve semiconductor physics equations (Poisson's equation, carrier continuity, drift-diffusion or hydrodynamic transport) on a meshed device structure to predict transistor electrical behavior without fabricating silicon.

What Device Simulation Solves

• Poisson's Equation: Relates electrostatic potential to charge distribution (dopants, free carriers).
• Electron Continuity: Conservation of electron current with generation/recombination.
• Hole Continuity: Conservation of hole current with generation/recombination.
• Transport Models: Drift-diffusion (standard), hydrodynamic (includes carrier heating), Monte Carlo (most accurate, slowest).

Key Outputs

• I-V Characteristics: Drain current vs. gate voltage (transfer curve), drain current vs. drain voltage (output curve).
• Threshold Voltage (Vt): Extracted from transfer curve.
• Subthreshold Slope (SS): Steepness of off-to-on transition.
• DIBL: Drain-Induced Barrier Lowering (short-channel effect metric).
• Capacitances: Gate, overlap, junction capacitances for circuit simulation.
• Band Diagrams: Energy band structure across the device.
• Current Flow: Visualize current density and path through the device.

Applications

• Technology Development: Optimize device architecture (FinFET, nanosheet, CFET) and doping profiles before silicon.
• DTCO: Design-Technology Co-Optimization—co-optimize device and standard cell together.
• SPICE Model Extraction: Generate compact model parameters for circuit simulators from device simulation data.
• Reliability: Simulate HCI, NBTI, TDDB degradation mechanisms.

Tools

• Synopsys Sentaurus Device (SDevice): Industry standard.
• Silvaco Atlas: Strong for power devices, III-V compounds.
• Simulation time: Minutes to hours per bias point depending on mesh complexity and physics models enabled.