CMP of fluorinated silicon dioxide: Is it necessary and feasible?

Abstract

Use of low-permittivity (low-k) fluorinated silicon dioxides (F-SiO2) for inter-metal dielectric (IMD) applications makes it necessary to evaluate the compatibility of chemical-mechanical polishing (CMP) in device fabrication. Basic material characteristics (such as adhesion, gap fill, step coverage, stress, hardness, chemical stability, moisture permeation, and wet etching rate) should be investigated thoroughly to assess CMP performance. With increasing fluorine content in the oxides, the low-k dielectric exhibits increased chemical reactivity and water absorption. These properties enhance the CMP removal rate, but degrade post-CMP material reliability and electrical performance. This article examines the CMP performance of F-SiO2 used to provide a low dielectric constant in IMD applications.