TANTALUM-BASED ENCAPSULANTS FOR THERMAL ANNEALING OF GAAS

During thermal annealing of GaAs there is a tendency for arsenic to evaporate. This process can have deleterious consequences and must be controlled during annealing by encapsulants. We survey conducting electrically, sputtered tantalum-based encapsulants as capping materials for thermal annealing of GaAs in the temperature range 550-900-degrees-C. Conducting capping layers have the advantage that they can be integrated in a contact metallization scheme. The backscattering spectrometry results show that Ta is not an effective cap. Evaporation through TaN can be detected after annealing at 700-degrees-C. Amorphous Ta74Si-26 was a good cap up to 800-degrees-C, and amorphous Ta36Si14N50 up to 850-degrees-C. Thus, while the effectiveness of Ta-based caps was improved significantly by the addition of either nitrogen or silicon alone, the best results were obtained for caps containing both Si and N.