RBS investigation of annealed thin gold layers on crystalline germanium

In this work we report firstly on the behaviour of Schottky barrier diodes (SBD's) when subjected to thermal treatment after metallization. To better understand this, a systematic study of the interaction between thin gold films and crystalline germanium substrates was undertaken. Gold metal films having thicknesses of 30 and 100 nm have been prepared by means of thermal evaporation on bulk-grown (111) n -type germanium doped with Sb to a level of 2.5×10 15 cm -3 . Before metallization the samples were first degreased and then etched in a mixture of H 2 O 2 :H 2 O (1:5) for one minute. Subsequently the samples have been thermally treated in Ar-atmosphere for 10 minutes and at temperatures ranging from 300 to 600°C. Rutherford backscattering spectrometry (RBS) has been performed to estimate the composition of the as-deposited and thermally treated films. It was found, that the composition of the as-deposited film remains unchanged under thermal treatment up to 340°C. Between 340°C and 360°C a gold-rich layer containing a very small amount of germanium is formed. At 361°C this layer suddenly converts to a germanium-rich layer with a small amount of gold. This transition is accompanied by the formation of agglomerates on the surface of the substrate.