The effect of Mg concentration and annealing temperature on the adhesion characteristics of Cu(Mg) films on glass substrates

Abstract

Pure Cu film and Cu(Mg) films having 1–4.5 at.% Mg were sputter-deposited on glass substrates, and annealed in vacuum at varying temperatures up to 400 °C. We investigated the effects of the Mg content and the annealing temperature on the resistivity and adhesion force of the Cu(Mg) film. We also discuss changes in surface morphologies such as agglomeration and hillock formation. The adhesion strength of the Cu film was greatly improved by adding Mg to the sputtering target. Cu(≥ 2 at.% Mg) films annealed at 350 °C showed critical loads over 300 mN, more than 10 times higher than the 5–26 mN of pure Cu films annealed at the same temperature. The incorporation of Mg also suppressed the agglomeration of the Cu film during annealing. The adhesion strength of Cu(2.7 at.% Mg) film decreased with increasing annealing temperature due to the increase in the residual tensile stress in the Cu(Mg) film. Hillocks were observed in the Cu(Mg) film annealed at 400 °C. Cu(2–3 at.% Mg) films annealed at 350 °C showed excellent adhesion strength to smooth-surfaced glass substrates without any glue layer, and had a relatively low resistivity of 3.5–4 μΩ cm.