The use of Ti as an antireflective coating for the laser planarization of Al for VLSI metallization

Abstract

Summary form only given. A report is presented on Ti as an antireflective coating (ARC) to solve the problems encountered using excimer lasers to melt and planarize an Al film. The composite metal film consists of 100-AA Ti on 0.5-1- mu m Al on 1000-AA Ti:W, where Ti is the ARC and Ti:W serves as both a wetting layer and a diffusion barrier. The absorptivity at 308 nm of this composite film has been measured as 0.4, which is about five times higher than that of Al. The introduction Ti ARC widens the process window (via-fill to ablation) from +or-6-8 to more than +or-20%. ARC does not improve the via-fill limit: the temperature of sufficient Al flow to fill contact windows is not lowered. Rather, the wider process window is achieved by pushing the ablation limit towards a higher laser fluence range. It is concluded that 100-AA Ti is not a desirable ARC. However, the value of an ARC in widening the process window is very important to laser planarization and has been demonstrated.<>