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In this paper we present the design and performance of millimeter wave MMIC switches in the patented MA-COM AlGaAs heterojunction PIN Diode process that allow us to produce high power and low insertion loss devices. The design process from a reflective SPDT switch to a non-reflective version of the switch, with intense use of HFSS and ADS software, is presented. These switches were designed to meet demanding requirements: low insertion loss less than 0.8 dB, 40dBm peak power and 37dBm CW power, and 30dB isolation.

MA-COM's monolithic GaAs PIN diode integrated circuit process has been used in high frequency switching applications for many years. A recent application of this process identified a unique failure mode related to operation at high RF power and low frequency. Under these high power conditions, switch insertion loss was seen to increase, particularly at lower frequencies (below 10 GHz). In an effort to better understand this failure mode, a series of reliability experiments were performed. Subsequent changes to this process were also subjected to process reliability tests.

Unusual negative resistance characteristics were observed in low barrier HMIC (Heterolithic Microwave Integrated Circuit) silicon Schottky diodes with HF (hydrofluoric acid)/IPA (isopropyl alcohol) vapor clean prior to epitaxial growth of silicon. SIMS (secondary ion mass spectroscopy) analysis and the results of the buried layer structure confirmed boron contamination in the substrate/epitaxial layer interface. Consequently the structure turned into a thyristor like p-n-p-n device. A dramatic reduction of boron contamination was found in the wafers with H 2 0/HCl/HF dry only clean prior to growth, which provided positive resistance characteristics. Consequently the mean differential resistance at 10 mA was reduced to about 8.1 . The lower series resistance (5.6-5.9 ) and near 1 ideality factor (1.03-1.06) of the Schottky devices indicated the good quality of the epitaxial layer.