  Optomechanical SiN nano-oscillators in high-finesse Fabry-Perot cavities can
be used to investigate the interaction between mechanical and optical degree of
freedom for ultra-sensitive metrology and fundamental quantum mechanical
studies. In this work we present a nano-oscillator made of a high-stress
round-shaped SiN membrane with an integrated on-chip 3D seismic filter properly
designed to reduce mechanical losses. This oscillator works in the 200 kHz - 5
MHz range and features a mechanical quality factor of $Q\simeq10^7$ and a
Q-frequency product in excess of $6.2 \times 10^{12}$ Hz at room temperature,
fulfilling the minimum requirement for quantum ground-state cooling of the
oscillator in an optomechanical cavity. The device is obtained by MEMS DRIE
bulk micromachining with a two-side silicon processing on a
Silicon-On-Insulator (SOI) wafer. The microfabrication process is quite
flexible and additional layers could be deposited over the SiN membrane before
the DRIE steps, if required for a sensing application. Therefore, such
oscillator is a promising candidate for quantum sensing applications in the
context of the emerging field of Quantum Technologies.
