Comparison of Low k Dielectric Film Properties Under Ultra Violet Curing Technique

Back End Of Line (BEOL) Low k Inter Layer Dielectric (ILD) films deposited using Plasma Enhanced Chemical Vapor Deposition (PECVD) processes are typically susceptible to mechanical and chemical damages after integration & downstream processes like Etching, Polishing etc. that raise reliability and packaging concerns. Addition of ultra violet (UV) curing enhances the film properties in terms of mechanical strength measured in modulus, hardness, adhesion energy of ILD to underlying film stack in addition to porogen removal & cross linking in ultra-low k films. This publication is intended to compare the low k and ultra-low k film properties as a function of UV cure with increments of UV curing time and intensity and different UV curing techniques. ILD stack properties are investigated from direct and indirect UV curing and positioning of UV curing in the film stack in a way to achieve desired mechanical strength & adhesion strength. Low k and Ultra low k films dielectric constant measurement comparison and correlation between traditional Mercury Probe and Surface Photo Voltage technique is presented. Effect of UV curing on the chemical bonding on low k and ultra-low k films are discussed using Fourier Transform Infra-Red (FTIR) Spectroscopy results.