Assessment of reliability of cap layers used in Cu-black diamond~(TM) interconnects

摘要

Black Diamond~(TM) (BD) is one of the primary candidates for use in copper-low k integration.Although BD is SiO_2 based,it is vastly different from oxide in terms of dielectric strength and reliability.One of the main reliability concerns is the drift of copper ions under electric field to the surrounding dielectric layer and this is evaluated by voltage ramp (V-ramp) and time depedent dielectric breakdown (TDDB).Metal 1 and Metal 2intralevel comb structures with different metal widths and spaces were chosen for dielectric breakdown studies.Breakdown field of individual test structures were obtained from V-ramp tests in the temperature range of 30 to 150 degC.TDDB was performed in the field range 0.5-2 MV/cm.From the leakage between combs at the same level (either metal 1 or metal 2) Cu drift through SiC/BD or SiN/BD interface was characterized.It was found that Cu/barrier and barrier/low k interfaces functioned as easy paths for copper drift thereby shorting the lines.Cu/SiC was found to provide a better interface than Cu/SiN.