A chemical role of refractory metal caps in Co silicidation: Evidence of SiO2 reduction by Ti cap

An interfacial SiO2 hampers a silicidation reaction between Co and Si. A re fractory metal cap is believed to block ambient oxygen diffusing toward the Co/Si inter-face. However, an interfacial SiO2 can also be present prior t o and/or during the annealing. This work reports on our findings of the int eraction between SiO2 and Co layers capped with refractory metals. It was f ound that Ti diffuses through the Co layer and segregates underneath the Co , which lends to the reduction of SiO2 and the fornaation of free Si. The f ree Si in-diffuses and reaches the original Ti surface. On the other hand, TiN shows a very inert behavior compared to Ti. The results are discussed i n connection with Co silicidation processes.