Optimization of tip material and shape for near‐UV TERS in Si structures

Abstract

High spatial resolution stress mapping of Si device structures is in high demand throughout electronic industry. This problem can be solved by application of the tip-enhanced Raman scattering (TERS) to Si structures. This work involves searching for a suitable TERS material for the near-UV spectral range that is favorable for Raman mapping of Si structures. We show both theoretically and experimentally that Al is a good Raman enhancer at the 363.8 nm wavelength. Taking into account Raman selection rules of Si and high dielectric contrast between Si and air, we employed an inclined Al-coated Si atomic force microscope (AFM) tip that is also suitable for the top-illumination geometry of the experiment. We succeeded in detecting of a weak TERS signal of strained Si. Possible ways of improvement of the Si TERS signal/noise ratio are discussed. An Al-particle-topped AFM tip is considered as a promising solution to the problem. A prototype tip was fabricated.

Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions

“…With etched metal tips, the fragile apex can be easily damaged by contact; with metallized AFM tips, adhesion of the metal is often poor. 274 Representative TER spectra obtained using a Au coated AFM tip under ambient conditions are shown in Fig. Thin coatings of a metal oxide such as SiO 2 or Al 2 O 3 have been shown to protect the tip from physical and chemical damage.…”

Effect of Scattering Efficiency in the Tip-Enhanced Raman Spectroscopic Imaging of Nanostructures in the Sub-diffraction Limit

“…On the 5 other hand, the studies on inorganic crystalline solids with pure covalent bonding such as Si crystal (fractional ionic character; FIC  0) showed medium enhancement of the order of 10 3 10 4 , however, with very few reports on imaging of single nanostructure. [25][26][27] The group III nitride crystals (InN, GaN, InGaN) having partially covalent and ionic bonding nature (FIC  0.5) resulted in very low Raman intensity enhancement than the covalent organic molecules and even lower than that of Si, [28][29][30] with hardly any reports on single nanostructure TERS imaging. In fact, not a single study on Raman enhancement of AlN is reported, as the AlN is an inorganic crystalline solid possessing highest iconicity (FIC  0.72) among other group III nitrides.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…High-spatial-resolution stress mapping of Si device structures is in high demand throughout electronic industry. Poborchii et al [55] show that this problem can be solved by the application of the TERS to Si structures. Their work involves searching for a suitable TERS material for the near-UV spectral range which is favorable for Raman mapping of Si structures.…”