Laser decal transfer of freestanding microcantilevers and microbridges

Freestanding silver microcantilevers and microbridges were fabricated over trenches in Si substrates by the laser decal transfer process without the use of sacrificial layers or subsequent etch processes. Single laser pulses (355 nm, 30 ns FWHM) were used to directly transfer 200 nm thick silver nanopaste layers (5 ?m wide×25 ?m long) over prepatterned Si substrates with 15 ?m wide trenches. By adjusting the position of the laser spot over the substrate, it was possible to directly deposit freestanding microcantilevers 7 to 9 ?m in length or 15-?m long microbridges over the trenches. Subsequent oven curing at 250°C resulted in sintering of the Ag nanoparticles without greatly affecting the shape and form of the transfers. Laser vibrometry experiments yielded fundamental resonance frequencies in vacuum of ?1–2 MHz for the microcantilevers and ?3 MHz for the microbridges. The fitted Q-factors averaged 1500 for the microcantilevers and 1400 for the microbridges. Overall, the measured resonances of the microbridges deviated from theoretical predictions in a manner suggesting a tensile residual stress state.