Ti/borophosphosilicate glass interfacial reactions and their effects on adhesion

The interfacial reaction of sputtered Ti films with borophosphosilicate glass (BPSG) sublayers has been studied using primarily Auger electron spectroscopy depth profiling techniques. Thin interfacial layers formed during rapid thermal annealing in N2 ambients were studied as a function of temperature, time, BPSG composition, and sublayer preclean treatment. A P-rich (phosphide) layer was found to accumulate at the Ti/BPSG interface during the reactions and in so doing inhibited the Ti/SiO2 reduction reaction. B accumulated only when the consumption of the entire Ti film neared completion. In some cases, adhesion failures could be generated following the deposition of an Al metallization over the reacted Ti/BPSG films. These failures were found to occur between the P-rich (phosphide) interfacial layer and the BPSG sublayer and could be prevented by backsputtering the BPSG prior to Ti deposition.