Fabrication of SiO2 microcantilever arrays for mechanical loss measurements

The sensitivity of high-precision measurements is crucially affected by the mechanical losses of the involved materials. In systems incorporating highly reflective elements based on amorphous Bragg reflectors, the mechanical losses of the coating materials have to be minimized. In this contribution, we report on the detailed fabrication of SiO2 microcantilever arrays to study such mechanical losses. The fabrication steps, consisting of pattern transfer, anisotropic and isotropic dry etching, have been optimized to be employed on both thermally grown and sputtered SiO2 samples. The cantilevers released from the Si substrate show a deviation of only 2% from the design, confirming a high selectivity of the etching processes. The mechanical loss measurements of the cantilevers are carried out using a laser-based optical setup, revealing a mechanical loss of 1.2 × 10−3.