Chapter 12: Tribology in Ultra-Smooth Surface Polishing

Abstract

ULTRA-SMOOTH SURFACES HAVE BEEN WIDELY used in many areas, e.g., large scale integration (LSI), computer hard disk driver (HDD), optic lenses, connectors of optic fibers, and so on. These surfaces should be of very low roughness and waviness, very high flatness, and very few defects. In order to achieve these requirements, many kinds of planarization techniques have been developed in the past 15 years, e.g., ultra-fine diamond (UFD) powder polishing [1] which has been used in the manufacturing of magnetic heads, chemical mechanical polishing (CMP) [2] which is recognized as the best method of achieving global planarization in ultra-smooth surface fabrication and also widely used in ultra-large scale integration fabrication, electric chemical polishing (ECP) and electric chemical mechanical polishing (ECMP) [3] which has also been used in global planarization of LSI fabrication, abrasive-free polishing [4], magnetofluid polishing [5], ultrasonic polishing [6], etc. These polishing techniques can be divided into three groups, one is the mechanical process, including UFD powder polishing, magnetofluid polishing, and ultrasonic polishing, where the polished surface cannot be used under erosion circumstance; another is the chemical process, including ECP, where chemical dissolving takes a major role; and the other is the chemical-mechanical process, including CMP and abrasive-free polishing, where the balance of chemical effect and mechanical removal is very important. During these polishing processes, tribology is one of the important factors. Good lubrication during the polishing process is the key factor to get an ultra-smooth surface, as severe wear related to the material removal rate (MRR) will cause scratches on the surface. Therefore, a better understanding of tribological behaviors between slurry, pad, and polished materials is helpful for the improvements of a polished surface. In this chapter, an introduction of experimental and theoretical studies on nanoparticles collision has been made, as nanoparticles impact on an ultra-smooth surface always occur in the ultra-smooth surface manufacturing. Then the development of CMP technology is introduced. And at last, the polishing of magnetic head surface is discussed.