Dielectric Relaxation of MIM Capacitor and Its Effect on Sigma-Delta A/D Converters

Dielectric relaxation of capacitors is one of the error sources when determining the accuracy of analog sampled-data systems that are based on charge storage. To perform an accurate characterization of the dielectric relaxation of metal-insulator-metal (MIM) capacitor, techniques based on the voltage recovery principle and the Curie Von Schweidler discharge current approach are developed. To model the dielectric relaxation of the MIM capacitor, Dow's model is selected. An algorithm for the model parameter extraction on the Curie Von Schweidler current has been developed, which shows the phenomenon of dielectric relaxation in detail and is very fast to determine the parameters. Based on the measurement data, a set of model parameters is extracted and verified, which approximates the Curie Von Schweidler law over a sufficiently wide interval of time constants. To study the effect of the dielectric relaxation on the circuit performance of high resolution sigma-delta ADC, a 12-b incremental ADC has been selected as an example for simulation. The simulation results show that the effect of the dielectric relaxation on the performance of the 12-b ADC is not significant. We show that the .major reason for this is that the noise shaping which is enforced by the integrators in SigmaDelta-ADC is almost not affected by the dielectric relaxation phenomenon.