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Particle Analysis of CMP Slurries

Chemical Mechanical Polishing (CMP) Applications

Chemical mechanical polishing (or planarization) is the most popular technique for removing the surface irregularities of silicon wafers. Typical CMP slurries consist of a nano-sized abrasive dispersed in acidic or basic solution. A chemical reaction softens the material during mechanical abrasion. The abrasive particles have a size distribution which directly affects critical metrics including rate of removal and wafer defects. Particle size analysis is therefore a key indicator of CMP slurry performance.

The typical size range of CMP abrasive particles is 50-250 nanometers and several particle sizing techniques are capable of measuring in this range with varying accuracy and precision. The typical oversize aggregate in CMP slurry is 1-10 microns and appears in the ppm range. The particle characterization challenge comes from the combination of accurately sizing the nano-scale particles while also identifying a relative few micron-scale aggregates.

Particle Size by Laser Diffraction

Laser diffraction is the most popular technique for sizing CMP slurries owing to its fast, accurate, and precise measurements of both the nano- and micro-scale particles. The LA-960 Particle Size Analyzer can accurately measure particles from 10 nanometers to 5,000 microns, making this system an obvious choice for CMP applications. Our recent study to quantify the ability of the LA-960 to find a small number of oversize particles in the presence of the main population at 31 nanometers proves this point.

Webinar: Zeta Potential of CMP Slurries

In this webinar we will first review and discuss the importance of the iso-electric point of metal-oxide polishing agents and the role of slurry pH and then we will examine the effect of slurry fluid chemistry using ZP measurements to characterize the chemically-modulated development of surface charge of such polishing agents during aqueous polishing.

Zeta Potential of CMP Slurries Webinar

Particle Size by Dynamic Light Scattering

The SZ-100 Nanoparticle Analyzer system uses dynamic light scattering has one advantage over laser diffraction: the ability to measure sub-100 nanometer particles at very low sample loading (particle concentration). After the presence of any destructive large particles has been verified, CMP test labs may add a DLS system to complement existing technologies for characterization of the smallest particles.