TCAD (Technology CAD) Overview

TCAD software simulates semiconductor fabrication processes and device physics, enabling engineers to develop and optimize new technology nodes virtually before committing to expensive silicon experiments.

Two Main TCAD Domains

• Process Simulation: Models fabrication steps (implantation, diffusion, oxidation, etch, deposition, CMP) to predict the resulting 2D/3D device structure and doping profiles.
• Device Simulation: Takes the process-simulated structure and solves semiconductor physics equations (Poisson, drift-diffusion, continuity) to predict electrical characteristics (I-V curves, C-V, breakdown voltage).

What TCAD Predicts

• Doping profiles after implant and anneal (junction depth, peak concentration).
• Film thickness and shape after deposition and etch.
• Transistor I-V characteristics (Vt, Ion, Ioff, DIBL, SS).
• Breakdown voltage and leakage mechanisms.
• Stress/strain effects on carrier mobility.
• Hot carrier and reliability degradation.

Major TCAD Tools

• Synopsys Sentaurus: Industry standard. Process (SProcess), Device (SDevice), mesh generation, visualization.
• Silvaco Victory: Process and device simulation suite. Strong in power devices and compound semiconductors.
• COMSOL: Finite-element multiphysics. Used for MEMS, thermal, and coupled simulations.

TCAD Workflow

1. Define process flow (sequence of fab steps with parameters). 2. Run process simulation → generates device structure with doping, geometry, stress. 3. Define electrodes and bias conditions. 4. Run device simulation → generates I-V, C-V, and other electrical characteristics. 5. Calibrate to silicon data. Iterate to match experiments. 6. Use calibrated TCAD for predictive splits and optimization.

Value: A single TCAD simulation takes hours. A real silicon experiment takes weeks and costs $50K-500K per wafer lot. TCAD dramatically accelerates technology development.