Hot filament CVD conductive microcrystalline diamond for high Q, high acoustic velocity micromechanical resonators

A capacitively transduced micromechanical resonator constructed in hot filament CVD boron-doped microcrystalline diamond (MCD) structural material has posted a measured Q of 146,580 at 232.441 kHz, which is 3× higher than the previous high for conductive polydiamond. Moreover, radial-contour mode disk resonators fabricated in the same MCD film and using material mismatched stems, cf., Figure 1, exhibit a Q of 71,400 at 299.86 MHz, which is the highest series-resonant Q yet measured for any on-chip resonator at this frequency. The material used here further exhibits an acoustic velocity of 18,516 m/s, which is now the highest to date among available surface micromachinable materials. For many potential applications, the hot filament CVD method demonstrated in this work is quite enabling, since it provides a much less expensive method than microwave CVD based alternatives for depositing doped CVD diamond over large wafers (e.g., 8”) for batch fabrication.