CVD AL for advanced interconnect applications

Abstract A method for depositing low resistivity, high purity aluminum films by Chemical Vapor Deposition (CVD) is introduced. Pyrolysis of Dimethyl Aluminum Hydride (DMAH) using either H 2 or an inert gas as a carrier is shown to yield films with less than 0.01 at.% carbon and oxygen and resistivities of 3.0 μΩcm. The kinetics are exponentially temperature dependent with E act ∼ 0.5 eV independent of substrate. Introduction of some possible byproducts indicate that the deposition mechanism may be self reduction of DMAH. The morphology, wettability, and step coverage of the films are shown to depend strongly on the nature of the substrate and how it is integrated with the CVD Al process. Clustering of CVD Al with the deposition of the underlying liner is shown to be critical in achieving the highest quality films. Smooth, highly 〈111〉 oriented films with excellent reflectivity may be obtained. Some methods for Cu doping are discussed including a novel form of in situ deposition. Complete via fill is obtained with blanket depositions with one or two grains filling the vias in most cases. Vias as high as 3.5:1 aspect ratio are filled—sometimes with a single grain of Al. Electrical results indicate that the via resistances and electromigration resistance of the Al plugs are excellent.