Three-dimensional submicron tomography of interfacial defects in GaAs IC ohmic contacts

摘要

Abstract: It is known that ohmic contact technology is a key problem in the development of GaAs MESFET circuits. It is usually achieved through a multilayer (Au, Ge, Ni) interdiffusion operation under controlled annealing. The electrical quality of the contact comes from the textures of complex alloy islands or micro-dots induced by the technology process. There is presently no nondestructive means of observing the physical nature of the interface of the contact with the bulk material. We propose using laser scanning tomography to explore the interfacial microprecipitates noninvasively and nondestructively. A new method of micro scanning and corresponding data processing allows us to obtain a 3 dimensional view of the internal region underlying the contact; this method is at a micron scale in the lateral direction, but it is, however, largely sub-micron in the z direction perpendicular to the surface which means that it gives a precise analysis of the critical region of the electronic transfer in the transistor. Experimental results are presented on standard circuits which have undergone thermal aging processes. !8