title: Material design of plasma-enhanced chemical vapour deposition SiCH films for low-kcap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects.
abstract: Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing thek-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si-C2H4-Si networks. Such films were estimated to have low porosity and lowk; thus they are the key to realizing a cap layer with a lowkand strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si-C2H4-Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-kcap layer.
authors.affiliation: Taiyo-Nippon Sanso Co., Tsukuba-shi, Ibaraki 300-2611, Japan; Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 103-8656, Japan.
authors.forename: Hideharu
authors.initials: H
authors.lastname: Shimizu
authors.affiliation: Taiyo-Nippon Sanso Co., Tsukuba-shi, Ibaraki 300-2611, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Nagano
authors.affiliation: Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8577, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Uedono
authors.affiliation: National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tajima
authors.affiliation: Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 103-8656, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Momose
authors.affiliation: Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 103-8656, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Shimogaki
keywords: PECVD; SiCH; barrier dielectrics; cap layer; interconnects; material design; precursor