Nanoscale patterning induced strain redistribution in ultrathin strained Si layers on oxide

Abstract

We present a comparative study of the influence of the thickness on the strain behavior upon nanoscale patterning of ultrathin strained Si layers directly on oxide. The strained layers were grown on a SiGe virtual substrate and transferred onto a SiO(2)/Si substrate using wafer bonding and hydrogen ion induced exfoliation. The post-patterning strain was evaluated using UV micro-Raman spectroscopy for thin (20 nm) and thick (60 nm) nanostructures with lateral dimensions in the range of 80-400 nm. We found that about 40-50% of the initial strain is maintained in the 20 nm thick nanostructures, whereas this fraction drops significantly to approximately 2-20% for the 60 nm thick ones. This phenomenon of free surface induced relaxation is described using detailed three-dimensional finite element simulations. The simulated strain 3D maps confirm the limited relaxation in thin nanostructures. This result has direct implications for the fabrication and manipulation of strained Si nanodevices.

Coherent X‐Ray Diffraction Imaging and Characterization of Strain in Silicon‐on‐Insulator Nanostructures

“…Thicker layers can be obtained by additional homoepitaxial growth without significant relaxation of the strain. For a 0.6% initial strain it has been found that the strain can be preserved during the subsequent homo‐epitaxial growth up to a thickness of 60 nm …”

Structural inhomogeneity in silicon-on-insulator probed with coherent X-ray diffraction

“…In previous work, SOI-structures have been characterised by Micro-beam Raman Spectroscopy [7], X-ray diffraction (XRD) [7]; cross-sectional high resolution transmission electron microscopy [8], white beam X-ray topography technique [9] and high-resolution nano-beam electron diffraction [10]. Here we report characterisation of SOI wafer structures by a coherent X-ray diffractive imaging method, which produces real-space images of the defects with a resolution potentially reaching tens of nanometres.…”

Stress redistribution in individual ultrathin strained silicon nanowires: a high-resolution polarized Raman study

“…Recently, it was demonstrated that ultrathin, globally strained silicon layers (nanomembranes) are the material of choice to generate strained Si nanowires using top-down nanofabrication processes [7,10,11]. Interestingly, upon nanoscale patterning of biaxial strained nanomembranes-a crucial step in the fabrication of strained nanowires-the formation of free surfaces induces a local relaxation of strain due to rearrangement of lattice atoms near the newly formed edges [10,[12][13][14][15][16]. In general, the extent of this phenomenon depends on dimension and geometry [12][13][14][15][16].…”