In-situ ATR-FTIR study of wet-chemical etching of HAR nanostructures

The surface chemistry characterization and etching kinetics of semiconductor materials like Si, SiGe, and dielectrics such as SiO2 and Si3N4 are crucial for advancing semiconductor technology. Although these materials form the foundation of modern electronic devices, there remains a significant gap when it comes to understanding the intrinsic differences in their surface properties and etching behavior, particularly on patterned and high aspect ratio (HAR) structures. HAR structures, increasingly used in advanced semiconductor devices, pose unique challenges in terms of etch uniformity, selectivity, and surface interactions. Understanding wetting and wet-chemical etching mechanisms in nano-confined geometries enables precise process control that is essential for device performance, reliability, and scalability.

In previous work^1,2, we demonstrated that a novel application of ATR-FTIR allows for direct probing of wetting states and dynamics on nanostructured surfaces.  Building on these insights, this project will further investigate how different structural geometries, pattern densities, surface chemistries and wet solutions influence wet chemical processes. Extensive work has been done over the past decades in characterizing the etching of blanket non-patterned thin films. However, the direct transfer of such knowledge to ‘real’ substrates patterned with HAR structures introduces additional complexities, such as surface roughness, plasma-induced damage and the presence of multiple materials, which often lead to unexpected observations that are not well understood at a fundamental level.

The PhD project is structured into two phases. The first phase aims to experimentally characterize the material and surface differences, establishing correlations with etch rates in both blanket and patterned materials. In the second phase, an in-situ study will be conducted using a flow cell integrated into the ATR-FTIR system to characterize the dynamic changes in surface chemistries and the solution near the surface. Additionally, a systematic study, with the aid of Lumerical FDTD simulations, will be undertaken to enhance IR absorption intensity by tuning the polarization of IR light, structure orientation with respect to the incident plane, and the geometry of the structures.

The successful candidate should have a solid background in (physical) chemistry, physics or material science, with strong problem-solving skills and good writing and oral communication skills.