TCAD (Technology Computer-Aided Design) is the physics-based simulation framework that models semiconductor device fabrication processes (process TCAD) and device electrical behavior (device TCAD) — solving the fundamental equations of semiconductor physics (drift-diffusion, Poisson, continuity) on calibrated 2D/3D device structures to predict device performance, optimize process conditions, and reduce the number of expensive silicon experiments required to develop new technology nodes.

Process TCAD

Simulates each fabrication step to predict the resulting device structure:

• Ion Implantation: Monte Carlo simulation of ion trajectories in the silicon lattice, accounting for channeling, straggle, and damage accumulation. Predicts dopant concentration profiles after implant.
• Diffusion/Annealing: Solves coupled partial differential equations for dopant diffusion, point defect (vacancy/interstitial) dynamics, and dopant activation during thermal processing. Predicts junction depth and sheet resistance.
• Oxidation: Models silicon consumption and oxide growth kinetics (Deal-Grove model extended for thin oxides). Critical for gate oxide process development.
• Deposition/Etch: Level-set or topography simulation of film deposition (conformality, step coverage) and etch profiles (anisotropy, selectivity, microloading).
• Lithography: Aerial image simulation and resist development modeling to predict post-litho feature profiles.

The output is a complete 2D or 3D device structure with material composition and doping profiles — ready for device simulation.

Device TCAD

Solves semiconductor physics equations on the device structure:

• Poisson Equation: ∇²ψ = -ρ/ε — relates electrostatic potential to charge distribution.
• Continuity Equations: ∂n/∂t = (1/q)∇·J_n + G - R — conservation of electrons and holes, with generation (G) and recombination (R) terms.
• Drift-Diffusion Transport: J_n = qnμ_nE + qD_n∇n — current driven by electric field (drift) and concentration gradient (diffusion).

From these, TCAD extracts: I_D-V_G characteristics, threshold voltage, subthreshold swing, on/off current ratio, breakdown voltage, capacitance, and other key device parameters.

Commercial TCAD Tools

• Synopsys Sentaurus: Industry-leading TCAD suite. Sentaurus Process for fabrication simulation, Sentaurus Device for electrical simulation. Supports 3D FinFET, GAA nanosheet, and custom device structures.
• Silvaco Victory/Atlas: Alternative TCAD platform. Victory Process for 3D process simulation, Atlas for 2D/3D device simulation.

TCAD Applications

• Technology Development: Explore process parameter spaces (implant dose, anneal temperature, gate length) virtually before committing to silicon. 100 TCAD experiments can replace 10 silicon wafer lots, saving $500K-1M per experiment cycle.
• Device Optimization: Optimize fin shape, nanosheet thickness, work function metal composition, S/D epitaxy stress to hit performance targets.
• Compact Model Calibration: Generate I-V and C-V data across corners for SPICE model parameter extraction (BSIM-CMG for FinFET/GAA).
• Reliability Prediction: Simulate degradation mechanisms (HCI, NBTI, EM) to predict device lifetime under accelerated stress.

TCAD is the virtual fab on a workstation — the simulation infrastructure that enables semiconductor engineers to explore, understand, and optimize fabrication processes and device designs at a fraction of the time and cost of physical experimentation, accelerating the development of each new technology generation.