RELIABILITY OF PASSIVATED COPPER MULTICHIP-MODULE STRUCTURES EMBEDDEDIN POLYIMIDE

Multichip module (MCM) structures were used to study the reliability o f copper conductor embedded in polyimide. Conductor lines fully encase d in titanium passivation, 50-100 nm thick, increased in resistance le ss than 0.4% after 1000 h of exposure to 85% humidity at 85-degrees-C and 10-V bias. The fully encased lines also had corrosion rates six ti mes lower than lines that had only 60% passivation coverage. Transmiss ion lines passivated with 50 nm of titanium showed very little degrada tion in the rise time or amplitude of digital pulses that had a 0.5-GH z clock rate and 149-ps rise time. Copper/polyimide via chain structur es were fabricated from vias having dimensions of 10-25 mum. After 100 0 cycles of thermal shock from -65 to 150-degrees-C, via chains showed no significant resistance change.