Spin-on dielectric films-a general overview

Abstract

In this paper an overview of both new and existing spin-on dielectric materials used in the manufacture of integrated circuit devices will be presented. Present day integrated circuit devices have 2 to 3 levels of metal interconnects, and future devices may contain upwards of 6 metal levels. This evolving structural complexity necessitates the development of low dielectric constant insulators keeping the RC time constant of the metal-insulator structure to a minimum. This meets the needs of today's high clock speed devices. In addition, spin-on dielectric films must be capable of withstanding temperatures in excess of 400/spl deg/C, resistant to water absorption, have good adhesion to underlying films, generate crack free films ranging in thickness from 0.1 to 1 /spl mu/m, and possess excellent mechanical and electrical strength. Spin-on dielectric films can be classified into four families: silicate, siloxane, organic, and nanoporous silicate. Silicates are silicon dioxide films formed by the cross-linking reaction of hydroxylated-silicate oligomers. Siloxanes are silicate compounds that are either partially or fully methylated. The addition of the methyl group lowers the film stress, lowers the dielectric constant by lowering the film density, and at the same time improves the gap fill and planarization of these films. Hydrogen, and have hydrogenmethyl siloxane combinations are under evaluation as well. Organic dielectrics are currently receiving a lot of attention from semiconductor device manufacturers and have-the benefit that thick, crack free, films can be formed. Organic polymers, on the other hand, are limited by their thermal stability. Nanoporous silicates overcome this issue by retaining a thermally stable silicon-oxygen backbone but make use of a modified xerogel technology to impart a nanoporous film structure resulting in ultra-low dielectric constant films.