Surface adhesion reduction in silicon microstructures using femtosecond laser pulses

A reduction of the adhesion between polysilicon surface-micromachined structures and its silicon substrate using ultrashort pulse laser irradiation has been demonstrated. Polysilicon cantilevers, which adhered to the silicon substrate after final rinse and dry, were freed after irradiation by a 800 nm wavelength laser with purse duration of 150 fs (full width at half-maximum) and fluences up to 40 mJ/cm(2). Increasing the pulse widths to 2.7 ps resulted in significantly fewer freed cantilevers indicating that the process depends heavily on the presence of high-temperature carriers in the silicon. Adhesion reduction has been observed from exposure to a single pulse which results in minimal lattice temperature increase. (C) 1996 American Institute of Physics.