Sputtered dielectric films for GaAs diffusion masks

Abstract

We have explored the use of sputtered dielectrics, rather than the more conventional thermal or plasma enhanced chemical vapor deposition films, as masks for localized zinc diffusion into GaAs. The masks employed in this study were films of Si0₂, Si₃N₄, and A1₂O₃, and part of the routine characterization included measurement of the mechanical stress within the films. Zinc diffusion was carried out for 60 min at 600° C in a “leaky tube” diffusion furnace. In short, it was found that (1) the alumina films did not work as diffusion masks, (2) the build-in stress within the SiO₂ and Si₃N₄ films was dependent upon the thickness of the film (increasing with thickness for SiO₂, and diminishing with thickness for Si₃N₄), and (3) the lateral diffusion of the zinc underneath the mask increased with the stress content of the film, regardless of the mask composition.