An Automated System for On-Wafer DC, S-Parameter, Power, and Harmonics Measurements of Broadband GaAs MMICs

An automated test system for broadband on-wafer measurements of small-signal and medium power GaAs MMICs has been developed. This system is capable of S-parameter measurements to 34 GHz, harmonics measurements to 40 GHz, and power measurements to 26.5 GHz. To maximize serviceability and phase stability, and to minimize drive signal loss the test set was constructed on the autoprober top plate. A 33 dB gain multistage 2 to 26.5 GHz GaAs MMIC amplifier with frequency selective padding develops 33 dBm midband and 30 dBm at 26.5 GHz. The system delivers 22 dBm across the measurement band at the input probe tip. The network analyzer is employed as a power meter and the power measurement dynamic range is determined by the phase lock range of the reference channel sampler. A switched filter bank provides source harmonic rejection for low level harmonic measurements. A switch at the output of the DUT allows the match presented to be varied. The system employs unique calibration and measurement algorithms which result an vector error corrected S-parameters and power. Harmonics are scalar error corrected. A number of test environment features were incorporated. A camera system was designed which gives superior imaging and working space near the probecard. A laminar flow system and air deionizer have been installed to reduce particulate and ESD respectively generated during wafer test sessions. A coolant system exercise 0 to 70 degree C control of the wafer chuck.