Polishing Glass-Ceramics with Ceria

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Dramatic increases in data-storage capacity have changed how we use computers. Ceramic platters offer significant advantages over current Aluminum-based technology. They are more rigid, while still light, and can be rotated faster, or simply moved, without increased fluctuations normal to the platter that would cause a head crash and drive failure. Glass platters are now in production but glass-ceramic platters would offer even greater performance. Polishing ceramic platters is difficult because the material is hard, and in the case of glass-ceramics, it is chemically inhomogeneous. Chemical-mechanical polishing (CMP) involves fracturing the material at the surface while not creating subsurface damage and smoothing the surface to produce a finish that is 100 times smoother than the size of the particles in the polishing medium. Ceria currently give the best results when polishing glass, not because it is particularly hard, but because it gives the best combination of hardness and chemistry. It is known that the chemistry at the point of contact is a critical factor-ceria polishing always involves water. Methods for polishing glass-ceramics are still being developed with ceria being the primary candidate. In this program, students work with cutting-edge techniques including electron microscopy, atomic-force microscopy and spectroscopy at the near-atomic scale. They apply their training in chemistry and mechanics to today's critical technology. Actually, there are many aspects of device fabrication which involve producing a smooth flat surface. For example, CMP is also used to planarize layers while building multilayer chips and to prepare the ends of optical fibers for optimizing interconnections. In the new high-speed hard-drives, the glass platters which support the magnetic storage media must be polished so flat that bumps are less than 10's of atoms high on a three-inch disk; compare this to smoothing the USA so no hill is higher than a few inches! Polishing has developed as an art but we need now to understand the science and to train students in both the art and the science. Our program addresses two problems: a lack of basic knowledge and the shortage of trained scientists who understand the art and science of CMP. This project shows students in materials science why they need those basic courses in chemistry, mechanical engineering and electrical engineering and how these disciplines combine in an industrial setting, not just for this project but for many applications of CMP. Our interdisciplinary research program brings together a diverse group of graduate and undergraduate students from different disciplines. The students meet our industrial colleagues, and visit the companies working with this technology. Skilled scientists who understand CMP and can fuller utilize the state-of-the-art instrumentation are a national need in the industrial workplace.