Micromachined planar spiral inductor in standard GaAs HEMT MMIC technology

A novel free-standing planar spiral inductor with reduced parasitic capacitances is proposed by suspending individually the strips, through a maskless front-side bulk micromachining compatible with a commercial GaAs HEMT monolithic microwave integrated circuit (MMIC) technology. Suspended structures have been fabricated and characterized at frequencies up to 15 GHz, showing quality factors of up to 16 and self-resonant frequency superior to 16 GHz for a 4.8 nH inductor. Moreover, since the standard IC process as well as the unconcerned electronic circuits are not influenced by micromachining, such devices are directly useful to enhance RF circuits, like matching networks, filters, and low-noise amplifiers.