Void formation in pulsed laser induced via/contact hole filling

Abstract
Metal (Au, Cu, and Al-1% Cu) layers sputter deposited over vias and contact holes of varying diameter and aspect ratio are melted and planarized by irradiation with either a 600 ns pulse duration flashlamp-pumped dye laser or a 35 ns pulse duration excimer laser. High aspect ratio (≳1) vias and contact holes yield metal profiles that suffer from void formation during the laser-induced flow. This void formation is explained by considering surface tension forces that, in high aspect ratio cases, act to close off the top of a hole without filling it.