Production and characterization of microcapsules consisting of melamine-formaldehyde wall material

Semiconductor integrated circuits use ultra-flat substrates called wafers, in which minute irregularities are eliminated to the utmost limit. To produce such a flat substrate, a polishing technique called chemical mechanical polishing (CMP) is used. In particular, polymeric polishing pads used for CMP facilitate the retention of polishing slurry material and the discharge of polishing products. The objective of this study was to develop hollow microcapsules to form polymer-based CMP polishing pads with superior strength. Hollow microcapsules were prepared with chlorobenzene as the core material and a melamine-formaldehyde skeleton as the wall material, and then removing the chlorobenzene by a subsequent drying process. Specifically, this study examined the effects of microcapsule preparation conditions (stirring speed during emulsification, concentration of capsule wall material, and volume ratio of dispersed phase to continuous phase) on capsule morphology and average particle diameter, the relationship between average particle diameter and bulk density, and drying methods to maintain a hollow structure. As a result, hollow microcapsules with an average particle size of 5-30 μm and a bulk density of less than 0.3 g/cm3 were achieved.