Article

Thin Film Insights with StrataPHI 3.0 in Practice: XPS‑Based Surface Coverage and Layer Modeling

Surface Analysis Spotlight: XPS

	by Norb Biderman Staff Scientist & Analytical Services Manager

Key Takeaways

• Ultra-thin film (< 10 nm) metrology with greater accuracy: StrataPHI 3.0 uses a physics-based model to extract thickness, composition, and fractional coverage from XPS without ion-beam sputtering
• Atomic layer deposition case study: StrataPHI 3.0 quantifies partial Al₂O₃ surface coverage on SiO₂/Si wafer while simultaneously extracting thickness

Ultra-thin film deposition methods such as atomic layer deposition (ALD) are seeing expanding adoption across multiple industries, driven by the need for atomic-scale process control.

However, insights into ALD-fabricated ultra-thin films, surfaces, and buried interfaces are often obscured due to limitations of even traditional surface analysis methods such as X-ray photoelectron spectroscopy (XPS) and hard X-ray photoelectron spectroscopy (HAXPES):

• Signal from multiple depths: XPS intensities originate from a depth up to ~ 10 nm, complicating depth reconstruction of thinner layers (e.g. 2 nm layer).
• Ion beam sputter-induced surface change: ultra‑thin stacks can be thinner than ion beam sputter‑damaged layers, so destructive ion‑beam depth profiling risks removing or transforming the very interfaces of interest.

StrataPHI 3.0 enables more accurate ultra-thin film metrology by using more realistic XPS physics-based modeling to extract thickness, composition, and fractional coverage without ion-beam sputtering or sample tilting. When deeper sensitivity is required, StrataPHI incorporates HAXPES data to probe multi-layer stacks up to ~ 30 nm below the surface. Fractional coverage analysis also quantifies surface coverage of partially covered monolayers as shown in Figure 1 with ALD-deposited Al₂O₃ film on SiO₂/Si while simultaneously determining Al₂O₃ film thickness.

Figure 1. Non-destructive StrataPHI reconstruction of XPS data from ALD Al₂O₃ on SiO₂/Si wafer, showing the depth profile and the cycle-by-cycle evolution of Al₂O₃ thickness and surface coverage.

Dr. Norb Biderman, Staff Scientist & Analytical Services Manager, will present the work using the StrataPHI 3.0 software at the Hudson Mohawk AVS Chapter 2026 Spring Meeting on Wednesday, April 29, 2026, hosted at Rensselaer Polytechnic Institute (RPI) in Troy, NY. Dr. Biderman will be available after the presentation to discuss applications