CHARACTERIZATION OF SLURRY PARTICLES USED IN CHEMICAL MECHANICAL POLISHING (CMP) OF WAFERS

摘要

The slurries used in chemical and mechanical polishing (CMP) contain highly concentrated nanometer-sized particles under varying degrees of agglomeration. The usual instrumentation methods for particle size measurement do not provide sufficient information on the degree of such particle agglomeration in a slurry. In this paper a new size measurement method based on filtration is described. The measured size is compared with those given by standard dynamic light scattering and electrokinetic sonic amplitude (ESA) methods. In addition, an electrospray/mobility analysis method has been developed to measure the primary particle size in a slurry. The primary particle size in the CMP slurry has also been measured. Dielectric and metal layer polishing slurries are studied and they cover a ranges of pH and solid concentrations. The mass distributions measured by filtration can be fitted with either a unimodal or a bimodal lognormal distribution, the mean particle size being considerably larger than those given by the instrumental methods. The difference is believed to be due to particle agglomeration in the slurry. The degree of agglomeration has been found to be time dependent during storage. The electrospray/mobility analysis method has yielded primary slurry particle sizes for the six slurries from 5.4 nm to 20.5 nm.