Optical measurement of the CMP slurry particle size distribution with undiluted, continuous, on-line sampling

摘要

This paper describes implementation of a very sensitive technique for measuring the CMP slurry particle size distribution (PSD) and small changes to that distribution. The method has been adapted for undiluted, continuous, on-line sampling,suitable for real time process control. Measurement of the slurry PSD is accomplished by inventing spectral transmission (or extinction) data from the ultraviolet, visible and near infrared. The method utilizes chemically resistant sample cells of smalloptical depth, plus miniature, fixed grating, linear detector array spectrometers. It also utilizes multiple sample cells of different optical depths, where optical depth is optimized for a specific spectral range, and multiple optical paths, whichcorrect for time and temperature drift of multiple radiation sources and multiple linear detector arrays. Continuous, volumetric (100%) sampling of 100 - 300 milliliters per minute of slurry provides superior sample statistics when compared to batchsamplers and alternative measurement techniques which require large amounts of dilution.