Rapid Thermal Nitridation of Tungsten-Capped Shallow Ohmic Contacts to GaAs

Abstract

ABSTRACTWe report on the use of AuGeNi/W and AuZn/W metallizations and their further processing by rapid thermal nitridation. Nitrided tungsten serves as a cap suppressing the sublimation of As. To study the effect of annealing conditions on the properties of the W cap, comparative experiments involving conventional annealing in H2, and RTA in N2 or O2 flow, have been performed. TEM, XRD, RBS, and SIMS have been employed to investigate contact microstructures. The obtained results prove the superiority of the contacts with nitrided W cap over conventional insulating cap. No W-N phase is observed in nitrided W layers, which is consistent with the model of a "stuffed" barrier by Nicolet.