Surface-related low-frequency noise of sputtered copper film

This paper presents the first attempt in correlating the low-frequency noise with the surface characteristics of metal films prepared by sputtering of copper onto oxidized-silicon and sapphire substrates. Results show that the noise behaviors and the surface physics of the metal films on these two kinds of substrates are different from each other. Particularly, the spectral slope of noise spectrum not only depends on the substrate but also on the thickness and surface area of the metal films. These observations suggest that the low-frequency noise of metal film, being governed by the surface roughness and irregularity of the sample, should be a surface effect. In addition, a number fluctuation model based on the electron tunneling between the hillocks at the surface is proposed to explain the observations.