Effects of Pad Temperature on the Chemical Mechanical Polishing of Tungsten

In this study, the effects of pad temperature on the chemical mechanical polishing (CMP) of tungsten were investigated. During polishing, the pad temperature was monitored and the removal rate behavior with respect to the pad temperature evolution was explored. The pad temperature was increased during tungsten CMP, and the tungsten removal rate increased accordingly. Further, it was found that the two had a strong correlation. Although tetraethyl orthosilicate (TEOS) polishing experiment showed that the pad temperature increased similarly under various experimental conditions, the TEOS removal rate did not change for all conditions. A novel pad-cooling nozzle effectively reduced the pad temperature during tungsten polishing and influenced the tungsten removal rate drop. Table motor current monitoring revealed that friction forces were almost identical under all experimental conditions for tungsten polishing regardless of the application of pad cooling. On the basis of pad temperature and table motor current data, it was clear that the tungsten removal rate was determined by temperature, indicating that the tungsten removal mechanism was mostly driven by a chemical reaction. Further, the pad cooling function can be used to control the tungsten removal rate effectively, resulting in a stable tungsten CMP process.