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

摘要

In this work, the thermal stability issue of ultrathin Ti-based silicide (TiSi_x) in prospective dynamic random access memory (DRAM) peripheral 3D FinFET transistors was systematically studied. As-prepared TiSi_x/n~+-Si contacts and ultrathin TiSi_x films with different annealing temperatures, were characterized by means of specific contact resistivity (ρ_c), 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 (ρ_c) for TiSi_x/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 TiSi_2 is conventionally known as thermal stable silicide, the agglomeration of ultrathin TiSi_x 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 ρ_c for TiSi_x/n~+-Si contacts.