A Technique to Reduce On-Wafer Measurement Uncertainty for CMOS Transmission Line Characterization

An improvement to the L-L method for Si monolithic Transmission Line (TL) parameter extraction is presented. The propagation constant $\gamma$ and characteristic impedance ${\rm Z}_{0}$ are obtained from cascaded ABCD matrices using on-wafer measurements up to 40 GHz. It is shown that the L-L method matrices processing is strongly dependent on the access variations as different pairs of measurements lead to different extracted TL parameters. Associating three different TLs lengths test structures measurements matrices, which theoretically point to an identity matrix, a technique is proposed to obtain the best set of three measurements with the most similar accesses. The deviation from the ideal identity matrix indicates the access variations. The suggested technique was implemented with TL structures fabricated on a 130 nm CMOS process. When using the best set of three different TL length measurements, the extracted $\gamma$ and ${\rm Z}_{0}$ parameters are almost independent on the TL pair used.