Method for improving chemical/mechanical polish uniformity over rough topography for semiconductor integrated circuits

Abstract

A method for making a planar interlevel dielectric (ILD) layer, having improved thickness uniforming across the substrate surface, over a patterned electrically conducting layer is achieved. The method involves forming electrically conducting lines on which is deposited a conformal first insulating layer that is uniformly thick across the substrate. An etch-stop composed of Si3N,is deposited and a second insulating layer, composed of SiO,or a low-dielectric-constant insulator, is deposited. The second insulating layer is then partially chemically/mechanically polished back to within a few thousand Angstroms of the etch-stop layer. The remaining second insulating layer is then plasma etched back selectively to the etch-stop layer to form a planar surface having a uniformly thick first insulating layer over the electrically conducting lines. The contact openings or via holes can now etched to a uniform depth in the etch-stop layer and the first insulating layer across the substrate. This results in contact openings having a constant aspect ratio across the substrate, thereby resulting in more repeatable and reliable contact resistance (R,).