Analysis of buried interfaces for device technology by soft and hard X-ray photoemission

K. Artyushkova, J. Mann, S. Zaccarine
Physical Electronics,
United States

Keywords: XPS, HAXPES, characterization, surface analysis, thin-films, structure analysis


Due to its accuracy and reliability in determining nm-thick overlayers on Si, XPS has been utilized as a metrology technique for many years. It has become more challenging to perform surface-sensitive XPS with a soft X-ray source because the interfaces of interest are frequently hidden beneath metal electrodes or oxide layers. Higher energy X-ray probe beams have made it possible to gather photoelectron signals from further deep in the material thanks to the development of lab-based hard X-ray spectrometers (HAXPES). New options for routine application for the qualification of the procedures and components utilized in technologically significant devices are thus made available. In this talk, we will discuss the current state of the art and possible future directions for integrating hard X-ray photoelectron spectroscopy (HAXPES) and soft X-ray photoelectron spectroscopy (XPS) in the study of semiconductors and nanoelectronics. We'll discuss the benefits of employing Hard X-ray sources on a lab-based high throughput fully automated spectrometer. This includes analysis of buried interfaces, such as electronic layers below a surface capping layer, and compositional studies in the bulk of materials and interfaces below the sampling depth of soft X-rays. Reduced surface contamination's impact on the photoelectron signal is another benefit of deeper sampling. For precisely the same reason, a deeper sample depth of the Cr source enables one to explore past the potential depth of ion sputtering-induced damage. Another crucial benefit is eliminating the overlap between Auger and major photoemission peaks. This is particularly important for transistor devices based on GaN technology, for which quantification using XPS is impossible due to the overlap between Ga Auger peaks and N 1s photoelectron peaks. Thin films of various types are critical components of modern microelectronic products. Conducting films form the interconnect layers in all chips, and dielectric films provide electrical insulation. Angle-resolved or angle-dependent XPS and HAXPES (ADXPS/ADHAXPES) is a powerful, non-destructive method that provides a quantitative chemical composition depth profile for thin film structures with thicknesses within the XPS sampling depth - under 5-10 nm for an Al K alpha soft X-ray source and ~15-30 nm for a Cr K alpha hard X-ray source. We will describe the use of the software StrataPHI for metrological applications in devices to estimate the structure of thin-film stacks from angle-dependent and spectral XPS and HAXPES data.