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(Color online) Buckling amplitude, measured by AFM as rms surface roughness, versus anneal time at , for 1D (blue circles) and 2D (black squares) buckling. Dotted lines show the exponential growth of buckling using extracted values of . Short solid lines indicate the maximum observed buckling amplitude . The inset schematic shows a SiGe film, initially flat, releasing its stress upon high temperature anneal via two simultaneous, competing mechanisms indicated by the arrows: lateral expansion to generate a flat, relaxed film; and buckling (vertical expansion) to create a rough surface.
(Color online) AFM images of SiGe on BPSG islands (Fig. 1 inset): (a) 2D buckling at the center of a square island, ; (b) and (c) 1D buckling at the center of rectangular islands, , aligned to the ⟨110⟩ and ⟨100⟩ crystal directions, as indicated, after a anneal at . The AFM scan size is and the -axis scale is .
(Color online) Average strain energy density of 1D and 2D buckled films vs buckling amplitude. The energy curves are plotted for the measured buckling wavelengths, as indicated. Arrows indicate the buckling amplitude at the minimum energy equilibrium state of the film, .
Summary of measured and modeled buckling parameters for 2D and 1D buckling. The values predicted by modeling are in parentheses.
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