Unraveling fundamental properties of exploratory materials using tip-enhanced spectroscopy

Metrology and materials characterization are critical components in the development of advanced nanoelectronics structures for both CMOS and more exotic applications. Within the family of characterization techniques, optical spectroscopies are of particular interest due to the non-destructive character and exceptionally fast time-to-result. The techniques are uniquely sensitive to mechanical stress, chemical composition, doping and crystallographic structure. However, regardless of the concept, state-of-the-art semiconductor devices are defined on length scales that are far beyond the optical diffraction limit, making them inaccessible for classical optical spectroscopy which typically has spatial resolutions of the order of 1 µm. Through plasmonic coupling with ultra-sharp Scanning Probe Microscopy (SPM) tips, the strengths of both techniques are combined in what is known as Tip-Enhanced Optical Spectroscopy (TEOS), translating the versatility of Raman and photoluminescence spectroscopy into the SPM nanoscale resolution. A similar implementation of this concept exists in the format of AFM-IR spectroscopy, which could further complement the investigations. This opens the path toward answering key questions for materials’ research like how currents and strain behave at nanoscale dimensions, how the material is affected by nanoscale device fabrication and how these parameters affect device performance. The technique has the potential to reveal at what length scales non-uniformities in the material are present and how these defects correlate with the electrical properties of the device.

Despite the availability of best-in-class setups, TEOS and AFM-IR remain expert techniques requiring deep insight in both the SPM and spectroscopy component, which the successful candidate will have the opportunity to develop. Laser-tip interaction and cross-correlation with the available SPM modes (KPFM, MFM, SCM,...) are some of the challenges of the project. The PhD candidate will explore the use of nanoscale spectroscopies for compositional, stress, doping and other parameters characterization in advanced structures like 2D materials transistor channels, CFETs and individual nanowires for future technology nodes. Building on extensive in-house know-how on both the spectroscopy and SPM aspects of the techniques, the PhD candidate will develop and optimize measurement approaches and explore their interpretation for deep-subwavelength semiconductor structures. The unique and stimulating imec research environment and the availability of flagship metrology equipment will enable breakthrough scientific results.