News from Nanotechjapan

加工技術

Magnetic field affects electrons during etching---Photochemical reactions induced by optical magnetic field---

 The University of Tokyo issued a press release on 31st March 2016 that a collaborative research group from Japan and France has succeeded in nano-scale photo-etching where the oscillating magnetic field of linearly polarized laser light strongly interacts with the material surface. The results were published in Light: Science & Applications* with Associate professor Takashi Yatsui as the senior author. 

 The research group has previously developed "near-field etching" as non-contact light-based polishing technology instead of CMP (Chemical Mechanical Polishing) in which electric field was thought to contribute to the polishing effect. In the present work, they performed photo-etching of ZrO2 nano-stripe structures using He-Cd laser (λ=325 nm) and oxygen radical from atmosphere. Etching property was identified to be polarization dependent and etching profiles were found to depend on the structure width. Experimental data were compared with numerical simulation results based on FDTD (Finite Difference Time Domain) method. The results revealed that the localized magnetic field induced by nano-scale structures causes the polarization dependent etching. This is contrary to the conventional idea that the magnetic field is negligible in photo-induced reactions.

 This nano-scale photo-etching is expected to find applications in non-contact polishing for Si-LSIs and opto-electronic devices with nano-scale flat surface and reduced contamination. 

*T. Yatsui, T. Tsuboi, M. Yamaguchi, K. Nobusada, S. Tojo, F. Stehlin, O. Soppera, D. Bloch, "Optically controlled magnetic-field etching on the nano-scale", Light: Science & Applications Vol. 5, Page number: e16054, doi:10.1038/lsa.2016.54; Published online 25 March 2016