Impact of Ge pre-amorphization implantation on Co/Co-Ti/n+-Si contacts in advanced Co interconnects

Co has been proposed as one of the most promising candidates to replace W or Cu in interconnects, where Co–Ti could be used as a single barrier/liner to prevent Co out-diffusion into dielectric and Si substrate as well as to enhance the adhesion property. In this paper, the material and electrical properties of Co/Co-Ti/n+-Si contacts with different compositions and thicknesses of Co–Ti, with and without Ge pre-amorphization implantation (Ge PAI) were investigated elaborately. Sheet resistance, phase formation, interfacial morphology and element distribution were comprehensively characterized in terms of four-point probe, X-ray diffraction and high-resolution transmission electron microscopy in combination with corresponding energy dispersive X-ray spectroscopy respectively. Meanwhile, the specific contact resistivity (ρc) was extracted using refined transmission line model structures, and it is found that Ge PAI is indeed beneficial in reducing ρc values in Co/Co-Ti/n+-Si contacts. With the assistance of Ge PAI, the lowest ρc value of 8.56 × 10−9 Ω cm2 is accomplished for Co/Co0.65Ti0.35/n+-Si contacts, which is a ∼47.8% reduction in contrast to that without Ge PAI.