Planarizing a trench dielectric having an upper surface within a trench spaced below an adjacent polish stop surface

Abstract

The present invention advantageously provides a method for using an abrasive surface and a particle-free liquid to polish a dielectric, wherein the dielectric is deposited within an isolation trench and across a polish stop surface such that a recess region of the dielectric is spaced below the polish stop surface. In an embodiment, the dielectric is an isolation oxide, and the polish stop surface belongs to an upper surface of a nitride layer formed above a silicon-based substrate. The surface of the dielectric is positioned laterally adjacent the abrasive polishing surface such that the particle-free liquid is positioned at the interface between the dielectric and the polishing surface. The particle-free liquid is preferably deionized water, and the abrasive polishing surface is preferably a polymeric matrix entrained with particles composed of, e.g., ceria. A force configured perpendicular to the backside of the substrate is applied to the polishing surface to force the dielectric surface against the polishing surface while the polishing surface is being rotated relative to the dielectric. As a result, elevationally raised regions of the dielectric are polished to the recessed region of the dielectric, planarizing the dielectric surface. The polish rate of the dielectric is substantially greater than that of the polish stop surface, and thus the polishing stop layer remains intact above the substrate. The polish rate of the elevationally raised regions of the dielectric is also greater than that of the recess region of the dielectric.