Growth process and chemical characterization of an ultrathin phosphate film grafted onto Al-alloy metallization surfaces relevant to microelectronic devices reliability

摘要

A simple process to grow an ultrathin phosphate layer on top of an Al-alloy metallization in microelectronic devices is described. The grown layer, about one-to-two monolayers thick, is able to protect the underlying metal from moisture induced corrosion even under severe stress conditions as in pressure cooker reliability tests. A chemical characterization of the passivating phosphate film carried out through ESCA and FTIR analyses reveals the existence of a certain degree of polymerization on the very surface, that turns to be a key factor to ensure corrosion inhibition properties. Hydroxidation after pressure cooker or atmosheric pressure saturated vapour tests was monitored by optical microscopy, surface chemical analysis and electrical resistence measurements. All those measurements confirm optimal corrosion inhibition behaviour of the grafted phosphate thin film.