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ON-WAFER MILLIMETER-WAVE NETWORK ANALYSIS FOR DEVICE AND CIRCUIT DESIGN James Tabuchi, Brian Hughes and Julio Perdomo Hewlett-Packard Company Network Measurements Division Microwave Technology Division Santa Rosa, CA 95403 ABSTRACT frequency and reduce the extrapolation span. It is evident that as technology pushes devices A broadband, millimeter-wave on-wafer and circuits to higher frequencies, the network analyzer system is necessary for the network analyzer systems must also evolve. characterization and design of millimeter- wave devices and circuits. The HP 85109B 45 MHz to 62.5 GHz network analyzer was' CRITICAL REQUIREMENTS OF A used to determine the fT and f max of a BROADBAND ON- WAFER NETWORK 0.25}Lm MODFET. The S-Parameters were ANALYZER SYSTEM also used to model an equivalent circuit of the MODFET. A broadband 0.5 to 50 GHz The most important criteria of a travelling wave amplifier [I] was measured to broadband on-wafer network analyzer system determine the cutoff frequency and the is measurement bandwidth. For device potential for out-of-band oscillations. measurements, it is desirable to have the Finally, a criteria was established for the widest bandwidth possible. For circuit selection of a broadband millimeter-wave measurements the bandwidth should not only network analyzer. be adequate to measure the device under test in its operating bandwidth, but should also extend higher in frequency for guardband INTRODUCTION measurements. Broadband on-wafer network analyzers are currently limited to 62.5 GHz In recent years improvements in semi- and broadband wafer probes are limited to 65 conductor processes have resulted in the GHz. V-Band network analyzer systems and ability to produce FETs with gate lengths as wafer probes are available for measurements small as O.I}Lm[2]. This, together with from 50 to 75 GHz [6], but are narrow improved material systems, such as banded. AlGaAsjInGaAs and AlInAsjInGaAs[3][4], In addition to measurement bandwidth, has provided the capability to produce another very important characteristic to MODFETs with fTS as high as 250 GHz[5]. consider in selecting an on-wafer network analyzer system is acc