In situ endpoint detection by pad temperature in chemical-mechanical polishing of copper overlay
As the number of metal levels and the wafer size increase, the global planarity and effective removal of metal overlay across the wafer becomes more crucial. Chemical-mechanical polishing (CMP) has been recognized essential to achieve this goal. Accurate in situ endpoint detection and monitoring method significantly improves the yield and throughput. Previous methods have been proposed, which either require the rearrangement of the machine set-up, or can only be implanted on certain types of machines. In this study, a model for pad temperature capable of predicting the endpoint of CMP in situ is established based on the total consumed kinematic energy between wafer and pad. Limited assumptions of thermal and kinematic conditions are made. The model of temperature rise uses the integral of the relative polishing speed and is verified by on-line measurement. Since the coefficient of friction between the pad and dielectric layer is distinguishably lower than that between the pad and the metal layer, the pad temperature increases milder than polishing the metal layer. In use of the proposed regression method applied to the measured temperature rise, the endpoint of the process can be detected.
Intelligent Face-Up CMP System Integrated with On-Line Optical Measurements
An innovative design for intelligent Chemical Mechanical Polishing (CMP) system is proposed and verified by experiments in this report. On-line measurement and real-time feedback are integrated to eliminate the shortcomings of traditional approaches, e.g., the batch-to-batch discrepancy of required polishing time, over consumption of chemical slurry, and non-uniformity across the wafer. The major advantage of the proposed method is that the finish of local surface roughness can be consistent, no matter where the inner-ring region or outer-ring region is concerned. Secondly, it is able to eliminate the Edge effect. Conventionally, the interfacial induced stress near the wafer edge is generally much higher than that near the wafer center. At last, by using the proposed intelligent chemical mechanical polishing strategy, the cost of the entire machining cycle can be much reduced while the quality of the finished goods certainly upgraded. Keywords—Chemical Mechanical Polishing, Active Magnetic Actuator, On-Line Measurement.
Influence of oxides on friction during Cu CMP
In this work, we investigated the frictional behavior of copper CMP. Using a laboratory polishing set up, we polished Cu with designed polishing media. After that the copper surface and the fumed silica particles Cu were analyzed. The surface analysis techniques used are the field emission SEM, the field-emission high-resolution analytical TEM, x-ray spectroscopy, and XPS. We found evident difference in friction value using different polishing media. Discussions lead to three mechanisms during copper CMP. The nature of copper oxides has a profound influence on friction and might be directly related to defects.