Elasto-Viscoplastic Response of Silicon to Femtosecond Laser Heating at Elevated Temperature
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The elasto-viscoplastodynamics of single-crystalline silicon in response to femtosecond laser pulsing at elevated temperature is studied. Hyperbolic energy transport dynamics is considered in conjunction with the Haasen-Sumino constitutive law to explore the thermo-elasto-visco-plastic response of the silicon material subjected to ultrafast optical heating. A computational scheme with staggered-grids is developed to time-integrate the coupled thermal-mechanical responses of silicon wafer at annealing temperatures up to 1,100K. Non-thermal melting fluence threshold is examined favorably against published physical data. The elasto-viscoplastic response at high annealing temperature is characterized by thermal stress waves that propagate with increased oscillation amplitude and modified frequency spectrum. It is shown that the induced transverse and longitudinal displacements along with the normal stress components all establish well-defined relations with temperatures, suggesting that they may be utilized for the thermometric profiling of silicon wafers undergoing Rapid Thermal Processing (RTP) with desired thermal resolution. Copyright © Taylor & Francis Group, LLC.
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