Microstructural Characterization of Multilayer Metal Stack on InGaAs/InP Contact

Abstract

Al/InGaAs, Al/Ti/InGaAs, and Al/Ni/InGaAs contacts were prepared by conducting rapid thermal annealing at different temperatures, and the interfacial reaction was characterized using x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The specific contact resistivity of the metal film contacts onn-InGaAs was determined using a circular transmission line measurement. The Al/Ni/InGaAs, Al/Ti/InGaAs, and Al/InGaAs stack contacts remained stable even after the samples were subjected to annealing at 400 degrees C. When the annealing temperature increased to 600 degrees C, Al began melting and clustering due to the formation of Al(Ga) to form Al/InGaAs. An AlNi phase was formed at the interfaces of an Al/Ni/InGaAs contact when it was annealed above 400 degrees C, thus causing the specific resistance and roughness to increase dramatically. Each element of the Al/Ti/InGaAs contact began diffusing when it was annealed beyond 400 degrees C, and an Al3Ti phase was formed above 500 degrees C. The formation of Al3Ti led to the increase in the specific resistance and roughness. Moreover, the as-deposited Al/Ni/InGaAs, Al/Ti/InGaAs and Al/InGaAs samples had specific resistances of 1.11 x 10(-5) omega cm(2), 5.11 x 10(-5) omega cm(2), and 1.14 x 10(-4) omega cm(2), respectively. These results reveal that to develop the Al/Ti/InGaAs and Al/Ni/InGaAs stacks on InGaAs with a low parasitic resistance, the processing temperature should be lower than 400 degrees C.