3-Dimensional Blow Torch-Molding of Fused Silica Microstructures

This paper presents a new and simple microfabrication process for creating various 3-D microstructures with high-aspect ratios (height/radius > 1). The key feature of this process is the use of a blow torch, which provides very intense localized heat for a short amount of time (<10 s). The flame temperature can be up to 2500 degrees C for a propane-oxygen torch, above the melting temperatures of many high-Q materials. We demonstrate the fabrication of hemispherical and half-toroid (birdbath) shells from 100-mu m-thick fused silica substrates. The structures have an rms surface roughness of 5.3 angstrom, which is crucial for achieving both high mechanical and optical Q. We create microbirdbath resonators by batch-level releasing the birdbath shells. We verify the resonance mode shapes of the degenerate n = 2 wineglass modes using laser vibrometry and measure the frequency and Q of these modes using laser vibrometry and a capacitive measurement method. We demonstrate one of the best mechanical Q and smallest frequency split between the n = 2 wineglass modes among existing micromechanical resonators. The birdbath resonator is promising for emerging applications such as the microrate-integrating gyroscope.