Highly-Conductive and Well-Adhered Cu Thin Film Fabricated on Quartz Glass by Heat Treatment of a Precursor Film Obtained Via Spray-Coating of an Aqueous Solution Involving Cu(II) Complexes

A Cu thin film on a quartz glass substrate was fabricated by a wet process involving heat-treatment of a precursor film spray-coated with an aqueous ammonia solution containing Cu(HCOO)2∙4H2O and Cu(II) complex of ethylenediamine-N,N,N′N′-tetraacetic acid. The precursor film that formed on the substrate at 180 °C in air was heat-treated at 350 °C and post annealed at 400 °C by placing an identical-sized glass on top, under Ar gas flow in a tubular furnace. X-ray diffraction pattern of the resultant film showed only peaks of Cu. The resultant film of 100 nm thickness has an adhesion strength and electrical resistivity of 37(7) MPa and 3.8(6) × 10−5 Ω cm, respectively. The images of atomic force and field-emission scanning-electron microscopies revealed a film of well-connected Cu grains with an average surface roughness of 11 nm. The reflectance of the thin film is more than 90% in the far-infrared region. The film’s chemical composition was also examined by using Auger electron spectroscopy.