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Chemical Mechanical Planarization (CMP) is a critical process in semiconductor manufacturing, using carefully engineered slurries to achieve the ultra-flat, defect-free wafer surfaces demanded by advanced device nodes. These slurries are complex, multicomponent colloidal systems comprising abrasive nanoparticles. dispersed within a liquid chemical matrix of oxidizers, corrosion inhibitors, surfactants, and polymeric additives. The interplay between chemistry and mechanical abrasion governs the material removal process, making precise control of slurry composition essential to yield.
At the heart of that control is the abrasive particle size distribution (PSD): it is a key factor influencing the material removal rate (MRR), within-wafer non-uniformity (WIWNU), surface roughness, and defect density, making it an important parameter in CMP process optimization. Yet the most widely used characterization technique — dynamic light scattering (DLS) — cannot reliably measure sub-30 nm fines, and resolve multimodal distributions, . TSI's Atomizer and Scanning Mobility Particle Sizer (SMPS) system changes that.
The Limits of Conventional Optical Measurement
Dynamic light scattering (DLS) has long been the default tool for CMP slurry characterization, but its fundamental physics work against accurate measurement in polydisperse systems. Because scattered light intensity scales with particle diameter to the sixth power, DLS is inherently biased toward larger particles - a single 200 nm agglomerate can overwhelm the signal from millions of 20 nm primary particles. The result is a volume-weighted distribution that masks the true multimodal structure of the abrasive phase. DLS also relies on assumptions about particle refractive index, making cross-material comparisons less reliable, and struggles to detect particles below approximately 30 nm - precisely the size range where fines can influence slurry chemistry, surface reactivity, and planarization performance. For next-generation devices with shrinking process margins, these blind spots can increase yield risk.
The TSI® Solution: Atomizer + SMPS
TSI's Atomizer and Scanning Mobility Particle Sizer (SMPS) system provides a fundamentally different approach to CMP slurry metrology. A slurry sample is introduced into the Atomizer, which creates fine droplets using an atomization nozzle. After the droplets are dried, only the non-volatile abrasive particles remain as dry aerosol particles. The airflow containing these dry aerosol particles is then drawn to the SMPS, where a differential mobility analyzer (DMA) separates particles by electrical mobility and a condensation particle counter (CPC) measures each size-segregated fraction. The result is a true, number-based particle size distribution, without relying on optical properties or refractive index assumptions. By counting individual particles rather than measuring scattered light intensity, the system accurately characterizes both sub-30 nm particles and larger agglomerates, revealing the full multimodal particle size distribution.
From Slurry Development to Process Control
Whether you're developing the next generation of CMP slurries or ensuring consistent polishing performance in high-volume semiconductor manufacturing, aerosolization + SMPS provides the high-resolution particle characterization needed for confident decision-making. Use it to qualify incoming slurry lots by detecting agglomerates and oversized particles before they impact wafer quality, continuously monitor particle size distributions to identify process deviations in real time, or optimize slurry formulations by understanding the complete abrasive particle population rather than a volume-weighted average. The result is better-informed process control, reduced defectivity, improved slurry consistency, and higher manufacturing yield.
Accurate Abrasive Particle Size Distributions
Resolve the full multimodal distribution — including sub-20 nm fines and large-particle agglomerate tails — that conventional optical methods cannot detect. Number-based sizing ensures every particle population is represented proportionally, giving formulators and process engineers a true picture of slurry composition rather than an intensity-weighted average dominated by the largest particles present.
Independent of Refractive Index
Unlike DLS, TSI's electrical mobility measurement is entirely unaffected by the optical properties of the particles being measured. This means the same system delivers equally accurate results across silica, ceria, copper, and alumina abrasive slurries — with no material-specific calibration, refractive index inputs, or optical model assumptions required.
Improved Data to Optimize Planarization
Gain more accurate, high-resolution particle size distribution (PSD) data to better understand and optimize CMP slurry performance. By characterizing the complete abrasive particle population—from sub-20 nm fines to oversized particles and agglomerates—you can make more informed decisions when optimizing slurry formulations, filtration strategies, dispersant loading, and qualification criteria. Detecting particle population changes before slurry reaches the polisher supports proactive process control, improves slurry consistency, and helps reduce the risk of particle-related defects throughout qualification and production.
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