Infrared spectroscopic near-field mapping of single nanotransistors

A. J. Huber, J. Wittborn, and R. Hillenbrand

Nanotechology 21, p.235702 (2010)
We demonstrate the application of scattering-type scanning near-field optical microscopy (s-SNOM) for infrared (IR) spectroscopic material recognition in state-of-the-art semiconductor devices. In particular, we employ s-SNOM for imaging of industrial CMOS transistors with a resolution better than 20 nm, which allows for the first time IR spectroscopic recognition of amorphous SiO2 and Si3N4 components in a single transistor device. The experimentally recorded near-field spectral signature of amorphous SiO2 shows excellent agreement with model calculations based on literature dielectric values, verifying that the characteristic near-field contrasts of SiO2 stem from a phonon–polariton resonant near-field interaction between the probing tip and the SiO2 nanostructures. Local material recognition by s-SNOM in combination with its capabilities of contact-free and non-invasive conductivity- and strain-mapping makes IR near-field microscopy a versatile metrology technique for nanoscale material characterization and semiconductor device analysis with application potential in research and development, failure analysis and reverse engineering.