ABSTRACT
III-V semiconductors are useful for RF and optical applications because of precise control possible with epilayers and stress control through lattice mismatch. Compound semiconductors are directenergy-bandgap materials, so MEMS fabrication on these can be combined with optical devices like lasers. For silicon SiO2 and borophosphate silicon glass (BPSG) are used as sacrificial layers, so HF and buffered oxide etch (BOE) are used as chemical etches. For III-V compounds there are more choices of sacrificial compounds and therefore etchants. Polyimide-type polymers are already in use in MMIC processing, so these can be easily incorporated as sacrificial layers, too. Compound semiconductors are piezoelectric materials; therefore this property can be used for actuation.
