Elasto-Viscoplastic Response of Silicon to Femtosecond Laser Heating at Elevated Temperature

Abstract

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 1,100 K. 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.

Thermal stress analysis and entropy generation rate due to laser short pulse heating of a metallic surface

“…In this case, for a deformable solid body, the specific enthalpy can be written as [24] h ϭ h(T L , e) (2) where e is the strain. It has been shown that [25] ͩ Ѩh Ѩe ͪ…”

“…Elastoviscoplastic response of silicon to femtosecond laser heating pulse was investigated by Qi and Suh [2], who indicated that the resulting transverse and longitudinal displacements, along with the normal stress components could be established through well-defined relations with temperatures. Deformation of an axially loaded thermoviscoplastic bar due to laser heating was studied by Wei and Batra [3].…”