Nanoscopically Engineered Polyimides

Abstract

Polyimides are currently the materials of choice for interlayer dielectrics in microelectronic applications, since polyimides, as a class of materials, best satisfy the requisite properties to survive the thermal, chemical, and mechanical stresses associated with microelectronic fabrication. As more function is demanded of these polymer dielectrics, e.g., low residual thermal stress, adhesion, photosensitivity, and low dielectric constant, it becomes increasingly difficult to design materials with the desired enhancements without compromising existing properties. This article will describe an approach to modify polyimide with minimal sacrifice to its desirable properties. The preparation of block and graft copolymers provides a means of tailoring the morphology and properties of polyimide through the judicious choice of the coblock, coblock composition, molecular architecture, and block lengths. It is the advent of the poly(amic alkyl ester) intermediate to the polyimide that allows for the controlled synthesis of such block copolymers. The hydrolytic stability of the poly(amic alkyl ester) precursor allows for the isolation and characterization of the copolymers prior to imidization. Such systems represent self-assembling arrays with considerable potential for the preparation of nanostructures, and this article will describe the modification of rigid and semi-rigid polyimides through copolymerization to address favorably such issues as residual thermal stress, dielectric constant, auto-adhesion, and other key design criteria.