On the influence of the surface pretreatment of a Si substrate on cobalt silicide formation

Abstract

The influence of surface contamination on silicide formation at the Co/Si interface is investigated. Some classical as well as some recently developed surface pretreatment methods are applied. Only those methods in which etching of the native oxide layer occurred lead to silicidation. To obtain silicidation, the temperature must be high enough to allow penetration of CO through this thin native oxide layer. Surface treatments that remove organic contamination from the surface produce lower silicidation temperatures. From a study of the dependence of the Schottky barrier height on annealing temperature, some suggestions about initially formed silicide could be given.

Influence of Si surface preparation on CoSi2 formation and agglomeration

“…4). It is communally argued that SiOx (or Ti) acts as a Co diffusion barrier during the early stages of the Co-Si reaction in the literature [15,16,49,52,53] and this should lead to a delay in silicide formation. As detailed before for the phase sequence, our similar temperatures of CoSi2 formation could be due to the combination of production method (SC1 solution) as well as the thin oxide layer thickness (0.7 nm and 0.8 nm for the P2 and P3 wafers respectively).…”

“…Since surface preparation is a process commonly used to modify the Si substrate surface [12][13][14][15][16], either by cleaning the Si substrate surface or by growing an oxide layer, it can have an influence on the cobalt silicide phase formation given that the presence of a silicon oxide layer between silicon and metal can prevent or alter the phase formation. Indeed, in the literature, when the formation of Co silicides occurs through an oxide layer (OME process, Oxide Mediated Epitaxy), the phase sequence can be modified [17][18][19][20][21].…”