In-situ Dispersion Characterization of CMP Slurries Using Low-Field NMR Relaxation Technology

CMP stands for Chemical Mechanical Polishing. It is a critical process in semiconductor wafer manufacturing, essential for producing high-precision, high-performance wafers. CMP slurry typically contains abrasive particles, pH adjusters, oxidizers, dispersants, and other additives. As a nanoscale suspension, the slurry requires highly controlled particle dispersion and size stability during polishing. Any fluctuation in particle size or agglomeration in the slurry can severely impact the final wafer quality.

Low-field NMR relaxation technology uses water molecules (solvent) as a probe to monitor real-time changes in molecular mobility within a suspension system.

It can sensitively distinguish the solvent molecules that form an interfacial layer between nanoparticles and the surrounding liquid. When particle size or dispersion changes, the behavior of these surface-bound solvent molecules also changes. Low-field NMR relaxation can accurately capture these dynamics, making it a powerful tool for evaluating particle dispersion and size variations in slurries such as CMP formulations or other nanosuspension systems.

Before the adoption of LF-NMR in CMP slurry analysis, nitrogen adsorption was the go-to method for determining specific surface area of particles. However, in R&D and manufacturing, it was observed that even when nitrogen adsorption results were stable, slurry performance could still fluctuate significantly. This is often caused by particle agglomeration in the liquid phase, leading to size changes that affect polishing performance. LF-NMR enables direct, in-situ assessment of dispersion in the original slurry—making it ideal for fast and accurate evaluation of CMP slurry stability in both development and production environments.

Beyond semiconductor CMP slurries, low-field NMR relaxation is widely applicable in emerging materials such as battery slurries for new energy systems, conductive silver pastes for photovoltaics, graphene dispersions, and electronic functional pastes. In all of these areas, LF-NMR provides essential insight into the dispersion and stability of raw slurry materials.

Low-Field NMR Relaxation Analyzer: