Thinning techniques for 1 μm ELO-SOI

The authors present a technique for growing epitaxial lateral overgrowth (ELO) structures and thinning them for device application. The use of trichlorosilane makes it possible to obtain local epitaxy without the edition of HCl gas and still suppress nucleation on the oxide. Resultant resistivities were above 300 Ω-cm n-type. Local epitaxy was performed at as low as 830°C making it possible to use this process after devices were realized in the substrate. Samples were planarized using a reflow photoresist and parallel-plate plasma etching. A mixture of CF₄ and O₂ was adjusted to obtain the same etch rate for silicon and organic compounds. Lapping with different grit sizes was used and shows promise with ELO structures. Polishing by combined chemical and mechanical action removes silicon only at the top of the ELO, like all mechanical processes. Additionally, polishing slurries that do not chemically attack SiO₂ films can be selected, making this an ideal technique for silicon islands on an oxide