Ellipsometer

About

Ellipsometer system in Photo Bay

Process: This is a spectroscopic ellipsometer that measures the change in polarization of light reflected from a sample to determine thin film thickness, optical constants (refractive index n and extinction coefficient k), and layer structure. It supports multi-wavelength operation and wafer mapping for spatial uniformity analysis.

Hardware: Multi-laser system with discrete wavelengths: 4050 Å (405 nm), 6328 Å (633 nm), 8300 Å (830 nm). Rotating analyzer/polarizer configuration for high precision. Automated stage for wafer mapping (multiple points across sample). Software for data acquisition, modeling, and fitting (e.g., Cauchy, Sellmeier, or tabulated dispersion models).

Key Features:

• Wavelengths: 4050 Å, 6328 Å, 8300 Å
• Measurement type: Spectroscopic ellipsometry (Psi and Delta)
• Capabilities: Thin film thickness (Å to µm range), refractive index n, extinction coefficient k, multi-layer modeling
• Wafer mapping: Yes (automated point-to-point or grid scans for uniformity)
• Sample size: Full wafers or pieces (confirm max diameter on tool)

Applications:

• Thickness measurement of dielectrics (SiO₂, Si₃N₄, Al₂O₃, HfO₂, etc.)
• Optical constants of thin films (high-k, low-k, AR coatings)
• Uniformity mapping across deposited wafers
• Characterization of ALD/CVD/PECVD films
• Process control for deposition tools (e.g., cross-check with PECVD, ALD, sputter)
• Research in optics, photonics, and semiconductors

Usage: Place sample on stage (flat, clean surface), align beam spot, select wavelengths and measurement points (single spot or map), run scan, fit model to Psi/Delta data, extract thickness/n/k. Save data and export maps/reports.

Detailed Specifications

• Model: Not specified (multi-wavelength ellipsometer)
• Location: Photo Bay
• Wavelengths: 4050 Å (405 nm), 6328 Å (633 nm), 8300 Å (830 nm)
• Measurement: Thin film thickness and optical constants (n, k)
• Wafer mapping: Yes (automated multi-point scans)
• Features: High precision for Å-level thickness, dispersion modeling, suitable for transparent/semi-transparent films
• Restrictions: Requires reflective surface (no fully transparent or very rough samples); accurate for films with known substrate properties
• Other: Non-destructive, fast optical metrology for thin-film process control

Documentation

• SOP – Standard Operating Procedure
• Training required – contact lab staff (Chandan Ramakrishnaiah or Shivakumar Bhaskaran)

Recipes & Data

• Standard Measurements: Common setups include:

 * SiO₂ on Si: Thickness via Cauchy model at 6328 Å
 * Si₃N₄ or high-k oxides: Multi-wavelength fit for n/k and thickness
 * ALD films (Al₂O₃, HfO₂): Å-level precision with wafer mapping
 * Organic/polymer layers: Dispersion models for thicker films

• Process Control: Use 3–5 points per wafer for uniformity; compare with Dektak (step height) or Filmetrics for cross-validation. Recalibrate model if substrate changes.
• Notes: Clean sample surface (no particles/oils). Use known substrate parameters (e.g., Si n/k) for accurate fitting. Multi-wavelength data improves robustness for complex stacks.

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