Evaporating and Sputtering of High-Density Ag Nanotwinned Films on GaAs Compound Semiconductor Wafers

Gallium arsenide (GaAs) has shown potential for its wide range of applications in radio frequency integrated circuit (RF-IC) packaging due to its unique properties over the traditional Si wafers. We reported the fabrication of high-density Ag nanotwinned films deposited on (400)-oriented GaAs substrates by magnetron sputtering and electron beam evaporation. In contrast to Si, the Ti precoating on GaAs is no longer necessary to provide better adhesion of the Ag nanotwinned film on the substrates. The results indicate that both the sputtered and evaporated Ag thin films exhibit high-density columnar Ag grains vertically growing on the substrates with the coincidence site lattice (CSL)- $\Sigma 3$ twin boundaries fraction of 35.6%. The electron backscatter diffraction (EBSD) analysis reveals that the twin boundaries within the sputtered Ag columns consist of a strongly preferential orientation of (111). The successful fabrication of Ag nanotwinned film via evaporation deposition will allow the applications in the backside metallization industry to be practical.