Particle size distribution shift as a predictor of slurry stability

As device dimensions shrink, increasing efforts are made to reduce micro- and sub micro-scratches. Liquid particle count (LPC) has traditionally been used to quantify slurry particles that may cause scratch defects during the chemical mechanical planarization (CMP) process, with a subsequent reduction in wafer yield. However, LPC has historically had a limitation in that the method could only detect relatively large particles, typically > 0.5 μm. For future advanced (small) nodes, micron and sub micro-scratches may be generated by particles <; 0.5 μm. In this paper, it will be demonstrated that particle size distribution (PSD) can be used as a more accurate metrology than LPC in predicting scratches. Furthermore, it will be demonstrated that PSD can be stabilized by the ingredients in the formulation.