Time resolved reflectivity measurements of Al alloys during excimer laser planarization

Time-resolved reflectivity measurements have been made in situ during XeCl (λ=308 nm) excimer laser planarization of Al, AlSi(1%), and AlSi(1%)Cu(0.5%) at 25, 250, and 400°C. The reflectivity change observed when using a HeNe (λ=632.8 nm) probe beam is assumed to indicate layer melting. Metal melt times have been determined as a function of laser energy fluence, substrate temperature, and oxide thickness. The results show that metal melt times increase with laser energy fluence and substrate temperature, the pure Al melts for shorter times and needs higher laser energy fluences than the corresponding alloys, and little difference is seen in the melting characteristics of the alloys. The best conditions for insuring complete planarization (long melt times) would thus be for conditions in which the wafer is heated