Integrated circuit air bridge structures and methods of fabricating same

Airbridge structures and processes for making air bridge structures and integrated circuits are disclosed. One airbridge structure has metal conductors 24 encased in a sheath of dielectric material 249. The conductors extend across a cavity 244 and a semiconductor substrate 238. In one embodiment, the conductors traversing the cavity 244 are supported by posts 248 that extend from the substrate. In another embodiment, oxide posts 258 extend from the substrate to support the conductors.In another embodiment, trenches 101 are made in a device substrate 110 bonded to a handle substrate 100. The trenches are filled with a dielectric and a conductor pattern is formed over the filled trenches. The substrate material between the conductors is then removed to leave a pattern of posts 116, 114, 112 that included dielectrically encased conductors 106.In another bonded wafer embodiment, conductors 204 are encased in a dielectric above a sacrificial device region. The device region is isolated by suitably filled trenches. Vias 224, 226 in the dielectric 205 allow removal of the substrate material to form a cavity 208 beneath the conductors 204.Other embodiments included a conductor 42 encased in dielectric that is formed above a region from which sacrificial polysilicon is removed to form a cavity 66. It is still another embodiment the conductor 42 is enclosed in a dielectric above a cavity 66a from which device material is removed.