Reliability Characterization of BEOL Vertical Natural Capacitor using Copper and Low-k SiCOH Dielectric for 65nm RF and Mixed-Signal Applications

Abstract

Integration of low-cost and high performance passive capacitors into existing Silicon CMOS technologies is essential for analog and radio frequency (RF) IC applications. Recently, BEOL vertical natural capacitors (VNCAP) with stacked via-comb structures have emerged as an attractive option due to their low-cost, high density, and highly symmetric configurations. In order to accurately predict low-k VNCAP reliability, in this study, both the time-dependent dielectric breakdown (TDDB) and capacitance stability (C-stability) of Cu/low-k SiCOH VNCAPs at 65nm technology node were thoroughly investigated. The TDDB performance of Cu/SiCOH VNCAP was found to be sensitive to device layouts and process. Capacitance stability was found to be sensitive to the presence of moisture in SiCOH low-k film during process. With the optimal device design and process, SiCOH VNCAP was found to exhibit robust TDDB performance, as well as absence of capacitance instability during high temperature stress (HTS).