Why photomask contamination is hard to identify
Real-world handling, cleaning, pellicle processes, packaging and fab environments can all leave trace organic films or microscopic particles on photomasks. These residues are often too thin and too small for conventional FTIR to resolve, and finding the cause usually depends on knowing what the contaminant is made of.
What PiFM tells you about a defect
- Particle or film: co-registered topography and chemical maps from the exact same spot
- Real residue or background: PiF-IR spectra separate the contaminant from the substrate
- Likely source: molecular fingerprints point to resist remnants, polymer transfer, cleaning byproducts or siloxane contamination
- Surface or buried: surface mode probes the top ~30 nm for ultrathin films, and bulk mode reaches ~100 nm for subsurface contamination
PiFM capabilities at Covalent (Molecular Vista Vista 200)
- Lateral resolution: ~5 nm
- IR range: 770–1840 and 1995–2395 cm⁻¹, 1 cm⁻¹ spectral resolution
- Stage travel: 200 × 200 mm; max scan size 120 × 120 µm
- Non-contact mode, so delicate surfaces aren’t damaged
- Semi-automated defect review: finds and identifies defects directly from KLARF files
What’s in the full case study
- How PiFM produces both chemical maps and point spectra
- When to use surface (side-band) mode versus bulk (direct drive) mode on photomasks
- PiF-IR compared with FTIR on a 20 nm polymer nanoparticle
- How chemical identification feeds back into cleaning, handling and fab processes to improve yield and CD control
Download the full case study to see PiFM spectra, chemical maps and a side-by-side comparison with FTIR.