Measurement of molar concentration spectra for nanoparticle with multi-modal nanoparticle size distribution using nanoparticle chip

Abstract

Particle size distribution (PSD) analysis for nanoparticle is important for quality management of CMP slurry, that used in chemical mechanical polishing (CMP) process. CMP slurry contains poly-dispersed particles, which consist of size-different primary particles and secondary particles in suspension. It is difficult to measure PSD for poly-dispersed particle using Dynamic Light Scattering, which is one of a typical method to evaluate PSD for mono-dispersed particles. The image analysis is also employed for PSD analysis. For image analysis, it needs to transfer the particles from suspension to a substrate before measurement. In this procedure, some particles aggregate with surrounding particles. It causes the difference between the PSD for dispersed particles in suspension and the PSD for observed particle using image analysis. In addition, concentration measurement is important for quality management of CMP slurry. Mass concentration is used in concentration evaluation for CMP slurry. However, it is difficult to identify the molar concentration for multi-modal particles, respectively. In this study, we suggested a method to define molar concentration spectra to express both a modal diameter and molar concentration for multi-modal nanoparticles to evaluate the CMP slurry. In order to measure the molar concentration spectra, we suggested a novel particle sizing method using nanoparticle chip (NPC) to measure number-weighted mean particle diameter, a variance of diameters, and molar concentration for every spectrum. Nanoparticles grid on a substrate to maintain the poly-dispersed condition in suspension to process NPC. NPC can assist the image analysis process to measure the PSD of particles in suspension. The number of particles, that aligned on the substrate, can be counted to measure the molar concentration. In this paper, a fundamental experiment was performed to investigate the feasibility of molar concentration spectra measurement. It is confirmed the molar concentration spectra for poly-dispersed particles can be measured by using NPC and it is considered that PSD with molar concentration spectra can give detail information of abrasive grain in suspension for quality management of CMP slurry.