Directional and preferential sputtering-based physical vapor deposition

Abstract

Physical sputtering techniques are characterized by a mostly isotropic deposition profile, which is useful for depositing films over steps, edges and lines. However, it fails for deposition into modest (>1 : 1) aspect ratio features due to overhang formation and subsequent void formation. A number of techniques have addressed this issue. Sputtering at high sample temperatures has been used to allow some degree of surface tension to help fill structures. Bias sputtering has been found to be useful for reducing void formation in low aspect ratio features. Collimated sputtering has been developed to filter the depositing atoms, resulting in mostly-normal incidence deposition. Finally, post-ionization of the sputtered atoms has been developed to deposit films primarily from metal ions, which are accelerated to the sample surface by means of a d.c. sample bias. Each of these techniques can lead to deposition within high aspect ratio features and will allow the application of sputter deposition for future semiconductor manufacturing processes. © 1995.