Verification of Operation Principle on End Point Detection by Skin Effect in Chemical Mechanical Planarization

摘要

An original eddy current sensor by making use of skin effect of copper film was developed for end point prediction in CMP (Chemical Mechanical Planarization). The main operation principle is based on detecting a local maximum point of eddy current due to skin effect in the course of film thickness reduction by CMP. This paper focuses on the verification of the operation principle. The verification evaluation using ferrite sheet supported that magnetic field passing through to a copper film is indispensable to operate the end point detection. From the result of both copper film process and tungsten film process, it was apparent that the resonant frequency profile depends on the skin depth of film material. The equivalent circuit model including the plane inductor and copper film indicates that a real part of an impedance of a plane inductor is proportion to the square of mutual inductance corresponding to eddy current induced. The simulation result of the real part of impedance of the plane inductor was a good agreement with actual resonant frequency profile. It was clarified that the operation principle of the end point detection is based on eddy current generation due to skin effect. (C) The Author(s) 2017. Published by ECS.