Fatigue of Aluminum Films Leading to Melting by Multiple Laser Pulses*

Repeated laser pulses at a single point on an aluminum thin film can reduce the power needed to melt or damage the surface as compared with CW application. This multi-pulse effect was found to depend on metal thickness and number of pulses, while being weakly dependent on the pulse length. This behavior appears to result from cumulative mechanical fatigue due to cyclic thermal stress in excess of the aluminum yield stress. This principle has been applied to cutting metal wires in microelectronic applications for deletive redundancy. The results suggest a significant advantage over CW laser application since the power needed to cut a metal wire is reduced by more than 70%, and 87% as compared to a single pulse.