Large‐Area Uniform 1‐nm‐Level Amorphous Carbon Layers from 3D Conformal Polymer Brushes. A “Next‐Generation” Cu Diffusion Barrier?
Yun‐Ho Kang, Sang‐Bong Lee, Sangbong Lee, Youngwoo Choi, Won Kyung Seong, Kyu Hyo Han, Jang Hwan Kim, Hyun‐Mi Kim, Seungbum Hong, Sun Hwa Lee, Sun Hwa Lee, Rodney S. Ruoff, Ki‐Bum Kim, Sang Ouk Kim
Abstract
Abstract A reliable method for preparing a conformal amorphous carbon (a‐C) layer with a thickness of 1‐nm‐level, is tested as a possible Cu diffusion barrier layer for next‐generation ultrahigh‐density semiconductor device miniaturization. A polystyrene brush of uniform thickness is grafted onto 4‐inch SiO 2 /Si wafer substrates with “self‐limiting” chemistry favoring such a uniform layer. UV crosslinking and subsequent carbonization transforms this polymer film into an ultrathin a‐C layer without pinholes or hillocks. The uniform coating of nonplanar regions or surfaces is also possible. The Cu diffusion “blocking ability” is evaluated by time‐dependent dielectric breakdown (TDDB) tests using a metal−oxide−semiconductor (MOS) capacitor structure. A 0.82 nm‐thick a‐C barrier gives TDDB lifetimes 3.3× longer than that obtained using the conventional 1.0 nm‐thick TaN x diffusion barrier. In addition, this exceptionally uniform ultrathin polymer and a‐C film layers hold promise for selective ion permeable membranes, electrically and thermally insulating films in electronics, slits of angstrom‐scale thickness, and, when appropriately functionalized, as a robust ultrathin coating with many other potential applications.