Strained Si-on-insulator fabricated from elastically-relaxed Si/SiGe structures

Abstract

Blanket pseudomorphic Si0.8Ge0.2/Si layer structures grown by Rapid thermal Chemical Vapor Deposition (RTCVD) on SOI substrates were etched to form 5μm × 5μm slabs, supported by a single pedestal at the center. Symmetric tri-layer slabs, 20nm Si/236nm Si0.8Ge 0.2/20nm Si supported by a SiO2 pedestal are flat and x-ray diffraction measurements of the strain and the thickness of the layers confirmed that the strain is shared between the Si and SiGe layers according to the ratio of the thickness of the SiGe and Si layers. These tri-layer structures were then firmly attached to the substrate using a filling material. A thermal oxide layer was grown on the upper and lower surface of the free-standing structures and then polycrystalline Si was deposited to fill the space between the free-standing structure and the Si substrate, thus attaching the bottom strained Si layer to the substrate. The polycrystalline Si was subsequently removed by reactive ion etching except from under the Si/SiGe/Si slab. The top SiO2 and Si layers as well as the SiGe layer were then removed selectively by wet etching. Raman spectroscopy measurements show that the strain in the attached strained Si-on-insulator layer is ε = 0.0067.