Christian Camus, Kolja Haberland, LayTec AG, Berlin, Germany
Optical in-situ metrology is a well-established tool for real-time characterization in semiconductor epitaxy where it is routinely used for process development, advanced process control, and early detection of deviations from nominal growth conditions. By providing continuous access to parameters such as layer thickness, growth rate, surface roughness, and substrate curvature, optical techniques enable direct insight into stress evolution and mechanical stability of multilayer systems. In contrast, comparable in-situ approaches are still not widely adopted for sputter-based thin-film deposition, despite their relevance for functional coatings and engineered surfaces.
In this contribution, we demonstrate how optical in-situ metrology techniques, including reflectometry, deflectometry, and pyrometry, can be applied to sputter processes to support characterization, testing, and failure analysis of thin films. Examples from magnetron sputtering of epitaxial GaN and AlN layers show how real-time monitoring of thickness, roughness, and curvature allows early detection of process instabilities and subtle deviations in film growth behavior that are not accessible by ex-situ methods.
Furthermore, a particular focus is placed on curvature and wafer-bow measurements during sputtering of tungsten–titanium (WTi) thin films. The results demonstrate that film stress and resulting substrate bow can be intentionally tuned between compressive and tensile regimes by adjusting process parameters, while unintended process drifts lead to characteristic and immediately detectable curvature signatures. These observations highlight the sensitivity of in-situ bow measurements as well as its value as an indicator for stress-related failure risks such as cracking or delamination.
Overall, this work illustrates how optical in-situ metrology transforms sputter deposition from a post-process characterization task into a real-time diagnostic tool, enabling early detection of process deviations, improved stress control, and enhanced reliability of thin-film and coating systems.