EXPERIMENTAL ULTRASONIC CHARACTERIZATION OF MACHINING DAMAGE FROM LOOSE ABRASIVE PROCESSES

Abstract

Currently there is a need for a non-destructive technique. which can characterize surface damage in loose abrasive machining processes such as chemical-mechanical planarization (CMP). CMP is used in the manufacturing of semi-conductors for interconnect structures. The ability of plate modes with surface displacements (PMSD), or surface acoustic waves (SAW), to penetrate to a fixed depth in the material, makes the technique well suited to characterize surface damage and near-surface properties. Modeling has been performed by a number of other investigators for which limited experimental comparison data has been available. The models show that surface damage for one-dimensional parallel surface-breaking cracks may be characterized by measuring the dispersion of SAW. Data on measured dispersion of PMSD and SAW associated with surface damage suggests that ultrasonic methods may be suitable for detection of surface damage. While a number of practical difficulties remain before a method can be in general use, results show that sensitivity exists both to the existence and scale of the surface damage.