Fabrication of a Cu nanodot array based on electroless plating employing a diblock copolymer nanotemplate

An array of copper (Cu) nanodots was fabricated onto a Si substrate covered with native oxide (Si O2 Si) using a diblock copolymer as a resist film. First, polystyrene/polymethylmethacrylate (PS/PMMA) diblock copolymer was spin-coated on a Si O2 Si substrate and then annealed for 24 h in a vacuum oven maintained at 170 °C to achieve good phase separation. To prepare a nanotemplate, this phase-separated diblock copolymer film was photodecomposed selectively using 172 nm vacuum ultraviolet (VUV) light. Due to the difference in photoetching rate between PS and PMMA domains, the latter regions were preferentially decomposed. By controlling the VUV irradiation conditions, that is, exposure time and atmospheric pressure, we were able to prepare a diblock copolymer template comprised of a nanoporous PS matrix on the Si O2 Si surface. Next, the nanopore regions were site-selectively modified through a vapor phase chemisorption of an amino-terminated organosilane. Palladium (Pd[II]) particles were then immobilized onto the amino-terminated nanopore regions through donor and accepter reactions and, subsequently, Cu was selectively electroless-plated onto these Pd-activated regions. As evidenced by atomic force microscopy, due to the elimination of the residual PS nanotemplate by VUV irradiation, we fabricated an array of Cu nanodots 3.0 to ∼4.3 nm in height and 10 to ∼25 nm in diameter on the entire 10×10 mm2 area of the Si O2 Si substrate.