process simulation flow

Process simulation flow (also called a virtual fabrication flow) is the practice of chaining multiple TCAD simulators in sequence to model an entire semiconductor process integration — from bare silicon through finished device — with each simulation step feeding its output as input to the next.

How It Works

• Each process step (oxidation, implantation, deposition, etch, lithography, CMP, etc.) is simulated individually using the appropriate physics engine.
• The output of one step — the physical structure (geometry, material layers, doping profiles, stress state) — becomes the input for the next step.
• The complete chain recreates the physical state of the device at every point in the manufacturing flow.

Typical Simulation Flow

1. Substrate Definition: Define starting wafer (orientation, doping, thickness).
2. Isolation (STI): Simulate oxidation, nitride deposition, trench etch, fill deposition, CMP planarization.
3. Well Formation: Simulate deep implants, drive-in diffusion/anneal.
4. Gate Stack: Simulate gate oxide growth, high-k deposition, metal gate deposition, gate patterning/etch.
5. Spacer Formation: Simulate spacer deposition and etch.
6. Source/Drain: Simulate extension implants, deep S/D implants, activation anneal.
7. Contacts/Metallization: Simulate silicidation, contact etch, barrier/seed deposition, metal fill.
8. Device Simulation: Extract the final structure and simulate electrical characteristics (I-V, C-V).

Key Software Tools

• Process Simulation: Sentaurus Process, ATHENA/VICTORY Process — simulate physical and chemical transformations.
• Device Simulation: Sentaurus Device, ATLAS/VICTORY Device — solve semiconductor equations (Poisson, drift-diffusion, quantum corrections) on the simulated structure.
• Interconnect: Raphael, StarRC — extract parasitic R, C, L from metal stack simulations.
• Integration Frameworks: Sentaurus Workbench, VICTORY Suite — manage the flow, parameter sweeps, and DOE.

Why Process Simulation Flow Matters

• Process Development: Test new integration schemes virtually before committing silicon — saves wafers, time, and fab resources.
• Root Cause Analysis: When a device fails electrically, trace back through the process flow to identify which step caused the problem.
• Process Window Exploration: Run virtual DOEs (varying process parameters) to find robust operating conditions.
• Technology Transfer: Use calibrated flows to predict device performance at a new fab or on new equipment.

Calibration

• Simulation accuracy depends on calibrated models — physical parameters (diffusion coefficients, reaction rates, etch rates) must be tuned to match actual fab data.
• A well-calibrated process flow can predict device performance within 5–10% of measured values.

Process simulation flow is the digital twin of semiconductor manufacturing — it enables engineers to explore, optimize, and troubleshoot process integration virtually before touching real silicon.