| The injection of self-interstitial atoms into bulk silicon during thermal oxidation has long been associated with atomic scale phenomena, such as oxidation-enhanced diffusion (OED) and the growth of oxidation-induced stacking faults (OISF). The current work suggests that interstitial injection may also be implicated in a nanoscale mechanical phenomenon. Previous researchers have found that the use sacrificial oxidation to fabricate suspended silicon nanowires results in an unexplained accumulation of permanent strain, which is manifested as buckling of the wires. We make use of suspended single-crystal silicon beams of sub-micron thickness to quantify this oxidation-induced strain (OIS) and its dependence on oxidation conditions.; Dry oxidation followed by removal of the oxide via etching in HF reduces the thickness of the nanobeams, which are fixed at both ends. As a result of the oxidation, the nanobeams undergo an increase in length, which is quantified by measuring the profiles of the buckled beams. The microscale lateral dimensions of these beams facilitate their measurement by optical interferometry, allowing us to take advantage of the innate amplification of displacement that accompanies buckling. This allows us to measure very small strains, in the range of microstrain.; A model for the oxidation-induced strain is developed based on the volumetric strain due to injection of Si atoms, and transition state theory is employed to express strain rate in terms of thermally activated processes. The influence of stress on these processes is also explored. |
