Analysis of the impact of vias on resonant rotary traveling wave oscillators

Rotatory traveling wave oscillator (RTWO) is an innovative technique for gigahertz rate clock signal generation and distribution. However, the increment of metal levels in current manufacturing technologies also increases the parasitic elements of vertical interconnections (vias), leading to a degradation in the integrity of the signal of the RTWO. In this work the analysis and quantification of undesirable effects introduced by vias are presented. Simulations were performed using the simulation tools HFSS (high frequency structural simulator) and Mentor Graphics, for different technologies (350, 180 and 130nm). The simulation results of RTWO oscillators show a degradation in frequency response above 1GHz when the effect of the vias is considered and the RTWO is operating at 30GHz. In this way is verified that the performance of RTWO systems is affected by the vertical interconnections.