Thermal stability issue of ultrathin Ti-based silicide for its application in prospective DRAM peripheral 3D FinFET transistors

In this work, the thermal stability issue of ultrathin Ti-based silicide (TiSix) in prospective dynamic random access memory (DRAM) peripheral 3D FinFET transistors was systematically studied. As-prepared TiSix/n+-Si contacts and ultrathin TiSix films with different annealing temperatures, were characterized by means of specific contact resistivity (ρc), sheet resistance measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). It is shown that the specific contact resistivity (ρc) for TiSix/n+-Si contacts gradually degrades with the increase of annealing temperature in the range 450–900 °C. In addition, it is revealed that though thick TiSi2 is conventionally known as thermal stable silicide, the agglomeration of ultrathin TiSix in the source/drain regions of 3D FinFETs still occurs after DRAM annealing typically at 750 °C for few hours. This agglomeration is thought to be responsible for the deterioration of ρc for TiSix/n+-Si contacts.