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Accurate and in-situ thickness measurements of copper films on Si-based wafers are employed to improve global planarization, adjust polishing pressure, and avoid over-polishing and under-polishing during chemical mechanical polishing (CMP). However, edge effects cause inaccurate thickness measurements at the wafer edge, and greatly decrease the effective area of integrated circuit (IC) manufacturing. In this study, edge effects were studied using both a trans-dimensional simulation model of electromagnetic fields and circuit coupling in eddy-current thickness measurement and an experimental nanoscale thickness-measurement sensor system with a resolution of 2.07 Å /mV. The simulation and experimental results were in close agreement when the sensor coil was located at different edge positions. The influence of different factors such as copper film thickness, edge positions, calibrated thickness, lift-off distance, and excitation voltages on thickness-measurement performance in the edge region were also examined. Copper film surface current density was calculated to clearly evaluate eddy-current distortion at different edge positions. The determined influences of these parameters on edge effects could be used to improve the edge-measurement performance of sensor systems by adjusting coil and circuit parameters or propose an edge signal compensation algorithm during CMP. [ABSTRACT FROM AUTHOR]

In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules' GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time. [ABSTRACT FROM AUTHOR]