AVS 45th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM-WeM

Paper EM-WeM9
Nanoscale Corrosive Wear of Ionic Materials: A Model System for Chemical Mechanical Polishing

Wednesday, November 4, 1998, 11:00 am, Room 316

Session: Fundamentals of Si Cleaning and CMP
Presenter: J.T. Dickinson, Washington State University
Authors: J.T. Dickinson, Washington State University
L. Scudiero, Washington State University
S.C. Langford, Washington State University
Correspondent: Click to Email
Fundamental studies of chemical mechanical polishing (CMP) are needed to improve and extend CMP to new applications. In CMP, surfaces experience simultaneous tribological loading and corrosive chemical exposure, which together produce high wear rates and favorable topography. We employ scanning probe microscopy (SPM) of single crystal surfaces in mildly corrosive solutions, where the SPM tip provides the mechanical stimulation in a controlled fashion. The applied normal force, the location of the contact, and lateral motion are readily controlled. For simplicity we choose model systems where the corrosive agent is water (properly buffered) and the single crystals are slightly soluble. These include calcite [CaCO@sub 3@] and brushite [CaHPO@sub 4@ 2H@sub 2@O] (a model biomaterial). Silicon nitride tips are used with applied normal loads from 0-300 nN, tip radii 30 nm and tip velocities from 1-200 µm/s. Quantitative data on the role of normal force, lateral velocity, surrounding surface topography, and solution chemistry can be obtained from images of the wear of atomic steps. The wear rate is a highly non-linear function of applied normal force (essentially exponential). Our results are interpreted in terms of stressed enhanced dissolution of steps, where double kink nucleation is the rate limiting process. We present a model which fits data for all systems examined to date. Careful analysis of step stability explain the observed sensitivity of certain step orientations to the enhanced wear induced by stress. Studies of atomically flat planarization of surfaces produced by controlled scanning are presented. This work is supported in part by the National Science Foundation under Grant CMS-9414405.