Method of depositing a copper seed layer which promotes improved feature surface coverage

摘要

A method of improving step coverage of a copper seed layer deposited over a semiconductor feature surface which is particularly useful for small size features having a high aspect ratio. Using a contact via as an example of a high aspect ratio feature, we have demonstrated that it is possible to increase the copper seed layer coverage simultaneously at both the bottom of the via and on the wall of the via . This increase is achieved by increasing the percentage of the depositing copper species which are ions. The percentage of species ionization which is necessary to obtain sufficient step coverage for the copper seed layer is a function of the aspect ratio of the feature. For features having a 0.25 mum or smaller feature size, an aspect ratio of about 3:1 requires that about 50% or more of the copper species be ions at the time of deposition on the substrate.