Fabrication of Thick Silicon Dioxide Air-Bridge for RF Application

Abstract

This paper proposes a 10 mum thick oxide air-bridge Structure which can he used as a substrate for RF circuits. The structure was was fabricated by anodic reaction, multi-step thermal oxidation and micromachining technology using tetramethylammonium hydroxide (TMAH) etching. This structure is mechanically stable because of thick oxide layer up to 10mum and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties, of the transmission line formed oil the oxidized porous silicon (OPS) air-bridge were Investigated and compared with those of the transmission line formed oil the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge is (about -2dB) lower than that of CPW oil OPS layers. Therefore, this technology is very promising for extending the use of complementary metal oxide (CMOS) circuitry to higher RF frequencies.