On-chip CMOS coplanar transmission line measurements and model verification up to 50 GHz

Abstract

The results show good agreement between de-embedded measurement and T- line coplanar model in both S-parameters and in Zo representation. In all cases the results of the T-line coplanar model are very close to the corresponding results of the EM solver. The RC model deviates significantly in the frequency domain from the T-line coplanar model results - both in S- parameters and in -Zo representation. The design impact of these deviations depends on the design niche (eg. digital vs. RF), and for a given design niche it may apply only to a given subset of critical wires (eg. clock line, high speed signal line etc.). The criticality of a given wire depends also on the wire length, and the on-chip effective bandwidth (rise time in digital or frequency in RF). For digital designs, the criteria for using a model that includes inductive effects (instead of RC model) was given and discussed previously.The considerations of designing the RF launching structures have been discussed. We have found that a robust optimal design of the RF launching structure allows for the usage of very simple de-embedding techniques up to relatively high frequencies.