Development of a High Voltage mmW GaAs PIN Diode Switch

David Hoag, Daniel Curcio and Timothy Boles
M/A-COM: Tyco Electronics

The initial development of a three pole three throw, (3P3T), switch for 35 to 40 GHz applications on the surface was thought to be a straightforward frequency scaled adaptation of a previously completed 6 port, 77 GHz switch for automotive collision avoidance radar systems. This misimpression was clearly demonstrated during the customer funded development and reliability qualification of this switch. This paper will cover the difficulties involved in transforming a relatively low voltage, system qualified and validated PIN switch product into a much higher voltage, 100% on wafer tested and characterized for all port characteristics at frequency with full reliability qualification. Topics covered will include the techniques needed to increase the PIN switch breakdown voltage by modifying the PIN structure and incorporating nitride under the transmission lines. A description of the voltage limitations of this underlying nitride film and the use of test structures to validate the DC characteristics of the physical changes to the circuit dielectric structure along with the results of the final device high temperature qualification is provided. In addition, design and process changes to effect higher yields through reduced circuit element breakage, increased bond pad strength and improved metallization definition capability will be discussed.