Molecular Spectroscopy Application eHandbook

Performance of Coating Uniformity Analysis

Significance of Coating Spatial Profiling

• Uniform optical coatings on large wafers are critical for maximizing device yield and performance.
• Conventional spot checks fail to reveal non-uniformities across 200 mm substrates.

Instruments and Methodology

• Agilent Cary 7000 UMS: UV-Vis-NIR spectrophotometer with multi-angle capability from 5°–85°.
• Universal Measurement Accessory (UMA): motorized sample and detector positioning for specular reflectance, transmission, and scattering.
• Solids Autosampler: mounts 200 mm wafers and provides radial (z) and rotational (Φ) movement for spatial mapping.
• Measurement conditions: 7° angle of incidence, s-polarization, 3°×1° beam aperture, 4 nm bandwidth.
• Mapping pattern: eight diameter chords at 22.5° increments, 27 points per chord up to 94 mm radius.

Results and Key Findings

• Center spectrum shows >99% reflectance in a 950–1150 nm band for the designed interference coating.
• Spatial profiles of %Rs and %Rp at 1064 nm reveal a gradual decline from center to edge, indicating centrosymmetric uniformity.
• Reproducibility better than 0.1% over a 6.5 hour mapping run demonstrates excellent instrument stability.
• Outliers in reflectance maps correspond to local contamination observed by visual inspection.

Practical Implications

• Automated, unattended measurements reduce cost-per-analysis and accelerate QA/QC workflows.
• Enables process engineers to identify and correct coating non-uniformities in deposition chambers.
• Applicable to spatial profiling of large or complex optical components, including diffusive and scattering coatings.

Future Trends and Applications

• Integration with real-time process control and predictive modeling for adaptive coating adjustments.
• Extension to full Mueller matrix mapping for polarization-sensitive coatings.
• Deployment in high-throughput manufacturing lines for inline quality assurance.