SOI structures by selective epitaxial lateral overgrowth

Selective epitaxial lateral overgrowth (ELO) of silicon has been investigated in the SiH₂Cl₂/HCl/H₂ system at reduced pressure and reduced temperature with emphasis on achieving high-quality silicon-on-insulator (SOI) structures for device applications. For these SOI structures to be viable in device applications, the ELO silicon must have good uniformity across the wafer. This would not be so difficult if the horizontal growth rate were much greater than the vertical growth rate. Presently this ratio is about 1:1. Because the vertical height is large it was necessary to etch back to form the thin (<1 μm) ELO silicon over SiO₂. To detach the ELO silicon for forming these SOI structures, trench isolation was then applied close to the edge of the seed windows. Three key steps were required to make a high-quality ELO-SOI structure: the cleaning of the silicon surface in the oxide-masked wafers prior to growth, the planar merging of crystal growth fronts and the subsequent etching back to form thin ELO silicon. A uniformity of about 2% was obtained after growth and etchback under certain conditions