  Freestanding Silicon nitride (SiN) devices are central to the field of
nanomechanical resonators and for other technology applications such as
transmission electron imaging and nanopore bioassays. The nanofabrication
techniques used for fabricating these devices often lack flexibility. While
photolithography requires printing of an expensive photomask for each new
design iteration, electron-beam lithography is extremely slow and commands high
equipment cost. Here we demonstrate maskless rapid prototyping of freestanding
SiN nanomechanical resonators fabricated by femtosecond laser ablation of plain
SiN membrane in ambient air. We fabricate microbeams with different widths from
7 to 100 um, and we characterize their resonance frequency and mechanical
quality (Q) factors. We find that membrane cracking can be avoided during
fabrication by carefully engineering the etch pattern, and that laser etching
has a negligible effect on built-in tensile stress. For each beam, Q-factors
are measured for several eigenmodes and are found to remain high after laser
etching. All beams show quality factors greater than 105, while unetched plain
membranes have Q > 106. Possible causes for Q-factor reduction are identified,
along with future process improvement directions.
