Tailoring of a wetting/barrier layer to reduce electromigration in an aluminium interconnect

摘要

A number of different wetting layer or wetting/barrier layer structures enables depositing of overlying aluminum interconnect layers having (111) texturing sufficient to provide a Rocking Curve FWHM angle θ of about 1° or less. These barrier layers include: 1) Ti alone, where the Ti is deposited using a high density plasma; 2) Ti/TiN, where both layers are deposited using a high density plasma; and, 3) Ti/TiN, where the Ti layer is deposited using a high density plasma and the TiN layer is deposited using standard sputtering techniques or collimated sputtering techniques. These barrier layers can be formed on a substrate in a single process chamber or in two process chambers, depending on the composition of the barrier layer and the features available in a given deposition chamber. When it is desired to use a tri-layer barrier layer (for reasons other than electromigration resistance), a Ti/TiN/TiN_x tri-layer having at least the initial Ti layer formed in a high density plasma provides excellent electromigration resistance in an aluminum layer subsequently deposited thereover. This is true even when the aluminum deposition temperature is below about 350 °C, for interconnect applications. The application of bias to a substrate (to attract ions toward the substrate) during deposition of at least the initial Ti layer is beneficial in improving the (111) texturing of a subsequently-deposited aluminum layer up to a point, after which the (111) texturing decreases.