Acoustical method and system for detecting and controlling chemical-mechanical polishing (CMP) depths into layers of conductors, semiconductors, and dielectric materials

Abstract

A method and system for controlling the depth of removal by polishing of a selected material on a supporting underlayer where it is desired to terminate removal of the selected material, such as tungsten, at the material-underlayer interface. In accordance with this novel method and system, the selected material such as a surface metallization layer is polished to initiate removal thereof in the direction of the material-underlayer interface. A microphone is positioned at a predetermined distance from the wafer to sense acoustical waves generated when the depth of material removal reaches a certain determinable distance from the interface to thereby generate output detection signals. These output detection signals are amplified and then applied to a spectrum analyzer which operates to analyze the sound intensity-versus-frequency characteristic of the acoustical waves received by the microphone. The spectrum analyzer operates to drive a CMP computer which in turn controls the operation of a CMP polishing machine. The CMP polishing motor terminates polishing of the selected material a predetermined time after a desired output signals are received from the spectrum analyzer. The present invention is also directed to a method and system or measuring the thickness of certain materials by comparing acoustical signals in a spectrum analyzer with frequency characteristics of known materials of certain layer thicknesses.

Dependencies are inferred from the claim text.