Elastic relaxation in an ultrathin strained silicon-on-insulator structure

Abstract

Coherent x-ray diffraction was used to study the relaxation in single ultrathin strained silicon structures with nanoscale accuracy. The investigated structure was patterned from 20 nm thick strained silicon-on-insulator substrate with an initial biaxial tensile strain of 0.6%. Two-dimensional maps of the post-patterning relaxation were obtained for single 1 × 1 μm2 structures. We found that the relaxation is localized near the edges, which undergo a significant contraction due to the formation of free surfaces. The relaxation extent decreases exponentially towards the center with a decay length of 50 nm. Three-dimensional simulations confirmed that over-etching is needed to explain the relaxation behavior.

Radiation-induced bending of silicon-on-insulator nanowires probed by coherent x-ray diffractive imaging

“…Similar defects have been observed using the coherent x-ray diffractive imaging (CXDI) technique in these wafers after patterning [11,12]. Strained-SOI nanostructures have also been studied and characterized by CDI and found to relax near their cut edges [13].…”

“…All the measurements reported here were performed at beamline 34-ID-C of the Advanced Photon Source at Argonne National Laboratory. CXD [13][14][15][16][17], especially when used for phase-contrast imaging, is one of the strongest contenders for investigating internal structures (both atomic density and phases) of nanosized crystalline materials. More conventional imaging techniques such as transmission electron microscopy can only probe very thin cross sections [18] and often require invasive sample preparation.…”

Quantitative Nanoscale Imaging of Lattice Distortions in Epitaxial Semiconductor Heterostructures Using Nanofocused X-ray Bragg Projection Ptychography

“…8,29 Near an in-plane edge, the SiGe unit cell gradually approaches its stress-free state, 30 SiGe plane, including the effects of both rotation and unit cell contraction averaged through the 9 film thickness, is shown in Figure 4 (green curve), and has a negative curvature consistent with the compressive in-plane strain state of epitaxial SiGe on SOI. (see SI for more model details).…”

Partially coherent x-ray diffractive imaging of complex objects

“…A related technique, Fourier-transform holography (FTH), solves the phase problem in the Fourier domain by interfering the far field scattering pattern with planewave references. CDI and FTH techniques have provided quantitative, high-resolution images of a variety of samples, including magnetic domains [5][6][7][8], ZnO nanocrystals [9], strained-silicon-on-insulator nanostructures [10], silicon-oninsulator nanowires [11], ceramic nanofoams [12], and biological samples such as yeast cells [13][14][15] and individual virus particles [16]. While improvements to reconstruction algorithms have allowed a broader range of information about the real-space nature of the sample being imaged, such as some knowledge of its composition [17], to serve as constraints on the reconstruction, the requirement of the reconstruction algorithms that the illuminating radiation have both high spatial and temporal coherence has hindered the progress and application of diffractive imaging.…”