Effect of Short-Term Annealing on the Crystalline Structure of Metallic Multilayers with a TiB₂ Anti-Diffusion Layer on GaAs Substrate

The structural characteristics of Au-TiB ₂/GaAs and Au-Mo-TiB₂-AuGe/GaAs device structures after deposition and short-term thermal annealing (STTA) were investigated. The multilayer contacts with TiB₂ anti-diffusion layer were magnetron sputtered on (001) GaAs substrates. The structures were STTA in a stream of hydrogen at temperatures of 400°C, 600°C, and 800°C during 60 seconds. The X-ray diffraction techniques and atomic force microscopy were used for investigation. At STTA a reduction of residual strain in multilayer metallic films, an increment of film grain size, a change of grains preferred orientation in the Au polycrystalline film and a transformation of surface morphology of the upper Au film were observed. These processes do not have monotonic temperature dependence. For Au-TiB₂/GaAs a minimum value of residual strains was observed at T=600°C while for Au-Mo-TiB₂-AuGe/GaAs it was observed at T=400°C. The roughness of Au film monotonically increased at annealing of Au-TiB₂/GaAs structure at T=400°C and T=600°C and corresponded to the initial value at T=800°C. A strong change of Au film roughness was observed at annealing of Au-Mo-TiB₂-AuGe/GaAs structure at T=600°C. The XRD pattern from a Au-TiB₂ metal film denoted a quasi-amorphous structure in the initial state and an increment of micrograins size at STTA. In the initial state the crystalline structure of Au film in Au-Mo-TiB₂-AuGe/GaAs structure had some preferred orientation in the <111> direction, which was reduced after STTA at T=600°C. The polycrystalline structure of Au film was partially deteriorated after STTA at T=800°C as TiB₂ layer was destroyed and lost its diffusion protecting properties.