Study of Metal Film Thickness on Endpoint Detection in Chemical Mechanical Polishing (CMP)

In chemical mechanical polishing (CMP), it is crucial to recognize that deficiencies in the polishing process can lead to insulation between circuits that cannot be eliminated, while excessive polishing may diminish the cross-sectional area of the wiring, thereby elevating the resistance value. The endpoint detection (EPD) system is employed to ascertain the thickness distribution of the metal film and to identify the optimal endpoint necessary for achieving global flatness, thereby preventing both under-polishing and over-polishing. However, when the metal film thickness of the High Down Force (HDF) is either excessively large or small, it becomes challenging to accurately identify the inflection point on the endpoint detection curve, which adversely affects sensitivity and accuracy. This paper theoretically and experimentally analyzes the impact of HDF metal film thickness on EPD detection accuracy, and optimizes the EPD parameters and detection window. The experimental results demonstrate that the optimized EPD curve is smoother and that the success rate of capturing the endpoint has significantly improved.