Development of Original End Point Detection System Utilizing Eddy Current Variation Due to Skin Effect in Chemical Mechanical Polishing

Abstract

An original end point detection system was developed by making use of the skin effect in chemical mechanical polishing (CMP). The developed system utilizes a critical change in the eddy current due to the skin effect. The critical change is caused by the following two phases in the polishing process. The first phase is that the eddy current increases when the magnetic flux begins to penetrate the copper film as the film thickness reduces to less than `skin depth'. The next phase is that the eddy current fades out due to substantial elimination of the copper film by further polishing. Consequently, a prominent local maximum point of the eddy current emerges at the turning point between the two phases, which can be detected sensitively before the copper film is eliminated. It was demonstrated that the developed system gains a high sensitivity by making use of a critical change in the eddy current due to the skin effect without exposing the semiconductor device excessively to an intense magnetic flux.