Fabrication of suspended dielectric mirror structures via xenon difluoride etching of an amorphous germanium sacrificial layer

The authors present a simplified fabrication method for the creation of free-standing dielectric mirrors for use in monolithic wavelength tunable surface-normal photonic devices, including vertical-cavity surface emitting lasers. This process utilizes a nonplasma dry etching process, based on the noble gas halide, xenon difluoride (XeF₂), to remove an inorganic sacrificial film comprised of low-temperature deposited amorphous germanium (α-Ge). By utilizing nonplasma dry etching of an inorganic film, this procedure circumvents the need for critical point drying and avoids the limitations imposed by polymer-based sacrificial layers. In this procedure the authors observe remarkably rapid lateral etching, with rates in excess of 150 μm/min for electron-beam evaporated α-Ge films. The viability of this novel surface micromachining process is demonstrated by presenting the static and dynamic mechanical characteristics of electrostatically actuated suspended dielectric Bragg reflectors.