Thermomechanical strains in small-size Au-GaAs thin film structures

In small-size contact technology, when dielectric covers with opened circular windows are used, the thermal strains appear to be considerable because of the different thermal expansion of the semiconductor (GaAs), deposited metal (Au) and dielectric cover (SiO2), widely used for manufacturing the devices. The strains occurring in the Au layer, in turn, result in defect formation or disappearance. It depends on two contrary processes: (i) the Au atom migration from the Au layer on the SiO2, surface to the GaAs windows at temperatures below 450 degrees C; (ii) the Ga atom migration from the GaAs windows into the Au on SiO2 at temperatures beyond 450 degrees C. Therefore, these processes ought to be taken into account in the pattern design of "honey-comb" structures: window dimensions, distances between the windows, SiO2, and Au layer thicknesses and their ratio. (C) 2000 Elsevier Science B.V. All rights reserved.