GaN and ZnO freestanding micromechanical structures on silicon-on-insulator substrates

Using a combination of selective dry etching techniques, surface micro-machined GaN and ZnO micromechanical structures are demonstrated on silicon-on-insulator (SOI) substrates. The dry releasing technique employs a controlled gas phase pulse etching with non-plasma xenon difluoride (XeF2), which selectively etches the Si overlayer of SOI, thus under-cutting the wide bandgap semiconductor material on top. This method prevents crystal damage of overhanging wide bandgap semiconductor mechanical structures. The mechanical properties of these released microstructures are characterized by micro-Raman spectroscopy.