Title :
Observations on the sensitivity of on-wafer cascode cell S-parameter measurements due to probing uncertainties
Author :
Shinghal, Priya ; Sloan, R. ; Duff, Christopher I. ; Cochran, Sandy
Author_Institution :
MCS Res. Group, Univ. of Manchester, Manchester, UK
Abstract :
On-wafer probing accuracy limitations affect measurement repeatability for potentially unstable circuits. Here we present a 2×25 μm pHEMT cascode cell on 2 mil GaAs substrate measured from 0.045-110 GHz. The S-parameter measurements carried out for the same device using two different on-wafer measurement systems, one PNA based (Sys-1) and the other a 8510XF VNA (Sys-2), differed by up to 2 dB in gain above 50 GHz. Measurements were performed using a Cascade Microtech probe station after applying on-wafer LRRM calibration on WINCAL XE using the same set of standards. Sys-1 used Cascade infinity probes; Sys-2 Cascade ACP probes. A maximum difference in measured gain of 1.1 dB at 85 GHz was observed with variation in probe position. As |S22| for the cascode configuration is > 1, measured gain is highly sensitive to the output termination. The extra pad metallization due to differing probe position was modeled as a negative shunt capacitance (-5 fF), effectively de-embedding the extra pad capacitance.
Keywords :
S-parameters; calibration; high electron mobility transistors; microwave measurement; millimetre wave measurement; 8510XF VNA; Cascade Microtech probe station; GaAs; GaAs substrate; PNA; Sys-1; Sys-2 Cascade ACP probes; WINCAL XE; cascade infinity probes; extra pad metallization; frequency 0.045 GHz to 110 GHz; negative shunt capacitance; on-wafer LRRM calibration; on-wafer cascode cell S-parameter measurements; on-wafer measurement; on-wafer probing accuracy limitations; pHEMT cascode cell; probing uncertainties; sensitivity; size 50 mum; Gain; Gain measurement; Loss measurement; Position measurement; Probes; Scattering parameters; Semiconductor device measurement; Cascode; MMIC; On-wafer; Probe; S-parameters; Ultra-broadband;
Conference_Titel :
Microwave Measurement Conference (ARFTG), 2014 83rd ARFTG
Conference_Location :
Tampa, FL
DOI :
10.1109/ARFTG.2014.6899524