Al speed fill

A novel via filling method, combining ionized barrier PVD and conventional Al PVD, has been developed which exploits the surface diffusion of Al for t he simultaneous fill of deep sub 0.5 mu m vias and trenches. This speeds up the via fill considerably compared with the classical cold/hot approach. T he Al is deposited in an all warm 2 step process consisting of the seed lay er and the Al flow at a wafer temperature ranging between 375 and 450 degre es C. Instead of avoiding the TiAl3 reaction during the seed layer depositi on the reaction is used to spread the Al. This requires a match between the deposition rate and the advancement of the reaction front. As a result the seed layer is formed independent of the aspect ratio of the recess. For th e subsequent Al flow a geometrical model is implemented to explain the rela tionship between the demand and supply of the Al. (C) 1999 Elsevier Science Ltd. All rights reserved.