HIGH-TEMPERATURE POLYIMIDE NANOFOAMS FOR MICROELECTRONIC APPLICATIONS

Foamed polyimides have been developed in order to obtain thin film die lectric layers with very low dielectric constants for use in microelec tronic devices. In these systems the pore sizes are in the nanometer r ange, thus, the term 'nanofoam'. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effect ed by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nano foams prepared from a number of polyimides as matrix materials were in vestigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SA XS, WAXD, DMTA, density measurements, refractive index measurements an d dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepar ed using the copolymer/nanofoam approach.