Dielectric absorption of low-k materials: extraction, modelling and influence on SAR ADCs

Low-k dielectrics will be required to continue miniaturisation of integrated circuits beyond the 90 nm node. The integration of these advanced materials results in significant reduction of signal delay and power dissipation compared to conventional silicon dioxide. As the technology continues to advance, the implementation of low-k dielectrics for the 65 nm node (Luo, et al., 2004) causes also problems, when using backend of line (BEOL) capacitors in mixed signal circuits. Especially the dielectric absorption effect increases dramatically. It limits the performance of capacitors and the circuits, where the capacitors are used (Zanchi, et al., 2000). A SAR ADC is a good example to show the impact of this effect. This paper presents the extraction and the modelling of the dielectric absorption effect of a low-k material as well as its influence on the resolution of a differential 16 bit SAR ADC.