A Study of Pulsed Laser Planarization of Aluminum for VLSI Metallization.
16 February 1989
The Aluminum flow under various excimer laser fluences and substrate temperatures has been studied systematically. The melting phenomenon, as well as the phenomena of planarization, via-filling, and ablation are reported. The laser (308nm) fluences needed to melt a 0.5microns Al film, to planarize over <=1micron contact vias, and to flow into and solidly fill the vias have been estimated at substrate temperatures of 25C, 200C, 350C, and 450C. The useful range of the laser fluences for VLSI metallization application depends on the shape and the size of the contact window. For example, for 1micron contact windows with vertical walls and an aspect ratio of 1:1, the fluences needed to fill the vias is ~2.57 J/cm sup 2 while that causes ablation is ~3.0 J/cm sup 2 at 200C. This represents a narrow process window of roughly +-8%.