Polyimide-silica microcomposite films

Planarizing films of fine-grained silica embedded in polyimide have been prepared by a spincoating technique and their structure has been investigated by optical and electron microscopy. The films were found to be diphasic. A silica content near 9 vol% yields a well mixed silica/polyimide composite which is homogeneous down to nanometre scale and has good planarization characteristics. Films with contents of 3 and 6 vol% silica have rough surfaces and exhibit two forms of segregation. In the 3% case, elongated inclusions of such silica/polyimide material appear at 100-m islands in a pure polyimide matrix. In the 6% case, the pure polyimide appears as 100-m elongated lakes surrounded by silica/polyimide material.