A new silicon micro-test-fixture facilitates the re-usability of accurately characterized low-power FET devices

Accurate characterization and modeling of microwave active devices is a prerequisite for reliable microwave circuit design. A new silicon micro-test-fixture which offers the possibility of (re-)using accurately characterized microwave GaAs FETs in final circuits is presented. In this way, device tolerances are eliminated resulting in accurately predictable microwave performances. The technological requirements that must be fulfilled to facilitate the re-usability of commercially available GaAs FET transistor chips and the required processing procedure are discussed. For device characterization purposes, microtest-fixtures are micromachined on a high resistivity silicon (MRS) wafer which is also suitable as a microwave substrate. After characterization and modeling of the microwave device, the required passive circuitry for the intended application can be realized on the same wafer incorporating the pre-tested device and using distributed coplanar components. The proposed technology minimizes the required lengths of bond wire interconnects between the chip and the passive circuit and offers the possibility of realizing planar interconnects using air-bridge technology.