Low stress films of cyclized polybutadiene rubber by vacuum annealing.

We report here a vacuum annealing technique for the post-deposition processing of cyclized polybutadiene rubber (CBR) films. The technique has proven effective in reducing film stress from 3.1+-0.5x10(8) dynes/cm(2) (tensile) to 1.4 +-0.2x10(8) dynes/cm (2) when the material is thermally cycled between 20 and 280C. For 10microns thick films the technique results in a net reduction in Si wafer bow by a factor of two. This reduction in wafer bow is important in the building of multilevel metallization structures where problems with patterning of films and automatic wafer handling equipment are encountered with excessively bowed substrates. A change in the glass transition temperature from ~320 to ~130C was also observed in the vacuum treated films and mechanical coupling to the substrate was seen to occur at ~175C instead of 280C.