Acetylene-terminated low-stress polyimide oligomer for interlayer dielectric applications

The authors describe a novel low-stress, acetylene-terminated polyimide well suited as the interlayer dielectric for MCMs (multichip modules). For successful application as an interlayer dielectric in a high-density microelectronic package, organic polymers must possess a variety of demanding properties, e.g. processibility, mechanical strength, adhesion, low dielectric constant, low water absorption, minimal outgassing, low thermal expansion, etc. The appropriate balance of properties depend upon the specific application. The authors describe a unique, oligomeric approach toward providing these balanced properties with the ability to customize the final product performance. It is shown how the thermal expansion and resulting residual film stress can be controlled by the proper choice of oligomeric structure. Acetylene end-capped polyisoimide oligomers with low thermal expansion from which low-stress dielectric films can be prepared are demonstrated. The properties and processing of these films are discussed and compared to conventional acetylene end-capped polyimide films