Excimer laser planarization of AlSi, AlSiTi and AlSiCu alloys

Abstract

In this work we use a XeCl excimer laser (λ = 308 nm) to planarize three Al alloys, namely AlSi(1%), and AlSi(1%)Ti(0.1%), and AlSi(1%)Cu(0.5%). AlSi(1%) is currently the dominant first level metalization used in production because of its low resistance and compatibility with conventional Si processes. The Ti and Cu are added to suppress hillocking and improve electromigration resistance. Our results show that excellent planarization is achieved for all topologies including submicron contact hole structures, however, for the AlSi alloy spot ablation occurs which is characterized by the removal of metal. This is not seen for the AlSiCu and the AlSiTi alloys. The best morphology is obtained for the AlSiTi alloy with large areas completely free of ablation and pitting, which indicates that excellent planarization over large device areas can be achieved using this alloy.