Filling narrow apertures and forming interconnects with a metal utilizing a crystallographically oriented liner layer

Abstract

An aluminum sputtering process, particularly useful for filling vias and contacts of high aspect ratios formed through a dielectric layer and also usefull for forming interconnects that are highly resistant to electromigration. A liner or barrier layer is first deposited by a high-density plasma (HDP) physical vapor deposition (PVD, also called sputtering) process, such as is done with an inductively coupled plasma. If a contact is connected at its bottom to a silicon element, the first sublayer of the liner layer is a Ti layer, which is silicided to the silicon substrate. The second sublayer comprises TiN, which not only acts as a barrier against the migration of undesirable components into the underlying silicon but also when deposited with an HDP process and biased wafer forms a dense, smooth crystal structure. The third sublayer comprises Ti and preferably is graded from TiN to Ti. Over the liner layer, an aluminum layer is deposited in a standard, non-HDP process. The liner layer allows the hottest part of the aluminum deposition to be performed at a relatively low temperature between 320 and 500° C., preferably between 350 and 420° C., while still filling narrow plug holes, and the TiN does not need to be annealed to form an effective barrier against diffusion into the silicon. A horizontal interconnect formed by the inventive process is resistant to electromigration.