Nirmalya Maity

Al speed fill

Abstract A novel via filling method, combining ionized barrier PVD and conventional Al PVD, has been developed which exploits the surface diffusion of Al for the simultaneous fill of deep sub 0.5 μm vias and trenches. This speeds up the via fill considerably compared with the classical cold/hot approach. The Al is deposited in an all warm 2 step process consisting of the seed layer and the Al flow at a wafer temperature ranging between 425 and 450°C. Instead of avoiding the TiAl 3 reaction during the seed layer deposition 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 the subsequent Al flow a geometrical model is implemented to explain the relationship between the demand and supply of the Al.