High-Resolution and Surface-Sensitive Tip-Enhanced Raman Spectroscopy Characterization of Strained-Silicon Devices through Cleanroom-Compatible Plasmonic Probes

Reliable characterization techniques that guarantee real-time quality control with a non-destructive and multiscale approach are currently an essential necessity for electronic industries. Tip-Enhanced Raman Spectroscopy (TERS) offers an excellent solution to this demand. In addition to providing chemical composition through the Raman spectrometer, TERS leverages the high lateral resolution of the coupled Atomic Force Microscope, enabling chemical and morphological characterization of samples down to the nanometer scale. This study advances the application of TERS by employing ad-hoc prepared TiN-coated probes, engineered to operate in cleanrooms while guaranteeing remarkable performances in terms of electromagnetic field enhancement. The subject of this analysis is a strained-silicon-based device, a technology meant to enhance the carrier's mobility in Complementary Metal-Oxide-Semiconductor (CMOS) architectures. The goal of the characterization is to detect the strain induced by a thin Si1-xGex alloy grown on a Si(100) substrate in the silicon lattice. TERS enables not only the detection of strain in the crystal structure but also its magnitude at different levels of depth, despite the penetration depth of the laser employed. This study is a result of the activities carried out in the framework of the European Union founded project CHALLENGES included in the Horizon2020 program.