Size distribution measurement of mixed abrasive slurry for chemical mechanical planarization using an electrospray scanning mobility particle sizer

Abstract

As the popularity of mixed abrasive slurry (MAS) use in chemical mechanical planarization (CMP) increases, analysis of number concentration and mixing ratios become increasingly important. In this study, the applicability of an electrospray-scanning mobility particle sizer (ES-SMPS) to particle-size analysis of MAS for measuring number concentration and mixing ratio is investigated. Additives to improve the CMP process cause non-volatile residue (NVR) peaks, making it difficult to obtain clear particle-size distributions. Because NVR peaks are affected by the size of the generated droplets, an aerosol generator that produces droplets of different sizes. Compared to atomizers that generate large droplets, an electrospray that generates small droplets minimizes disturbance of NVR peaks, allowing for clear particle-size distributions. Using ES-SMPS, the number concentration and mixing ratio of an MAS were analyzed with no interference from NVR peaks. CMP evaluation of an MAS of a certain number concentration confirmed that using an MAS with a constant number concentration improves the removal rate. Number concentration–based MAS analysis is therefore possible using existing weight concentration–based MAS research and ES-SMPS measurements. Measurement of abrasive number concentrations using ES-SMPS can also provide more realistic information on the number of participating abrasives.