An RBS study on the annealing behaviour of Cu thin films on brominated Si(111) and Si(100) substrates

Abstract

The thermal annealing behaviour of Cu thin films deposited on Si(100) and Si(111) substrates has been studied by Rutherford backscatteringspectrometry (RBS). For thin film deposition, two different initial conditions of the substrates have been used. In one, the substrates had a top native oxide layer, and in the other the native oxide layer was etched in hydrofluoric acid and treated with a bromine-methanol solution without the surface being exposed to atmosphere. RBS measurements on the Cu/Si samples showed the onset temperature of interdiffusion to be ≈300°C for the Si(111) substrate treated with bromine-methanol solution, whereas the onset temperature of interdiffusion was found to be between 500 and 700°C for both Si(111) and Si(100) surfaces with native oxide on top and Si(100) surface treated with bromine-methanol solution. The difference in behaviour for the bromine treated Si(111) and Si(100) substrates can be explained in terms of preferential saturation of Si dangling bonds by Br on the Si(111) surfaces. The onset temperature of interdiffusion for the Br-treated Si(111) surfaces is comparable to that for the atomically clean Si(111) 7 × 7 reconstructed surfaces prepared in ultrahigh-vacuum (UHV) condition.