Direct sub-μm lateral patterning of SOI by focused laser beam induced oxidation

We have developed a method for resistless patterning of Silicon-On-Insulator (SOI) in order to directly achieve lateral dielectric isolation. Our method employs a diffraction limited laser spot of a cw argon laser which is scanned across the SOI surface and directly oxidizes the silicon in ambient atmosphere. We investigate the dependence of the line width on the laser power and laser wavelength and scanning speed by AFM measurements. Line widths as narrow as 200 nm are achieved. We have fabricated in-plane-gate transistors with effective channel widths of 250 nm and excellent gate to source-drain isolation. We further demonstrate how our method can be extended for local simultaneous oxidation and doping of the silicon surface with high spatial resolution. A novel in-plane-FET device has thus been realized.