Impact sound stressing for semiconductors

Abstract

Apparatus for acoustical stressing of semiconductor wafers is disclosed, utilizing a number of small tungsten balls which are bounced on the surface of the wafer to be stressed. The movement of the tungsten balls is effectuated by clamping a wafer at one end of a conduit, the other end being attached to a high intensity loudspeaker. The loudspeaker is driven at resonant frequency of the clamped wafer and accordingly the tungsten balls bounce on the surface. This impact creates micro-cracks on the surface of the wafer and number and depth of these cracks can be controlled by power input and the number of tungsten balls utilized. Controlled stressing can thereby be accomplished both in terms of density of micro-cracks and location on the wafer. Impact sound stressing finds utilization in the study of semi-conductor surfaces to determine effects of dislocations and micro-splits and in the evaluation of wafer polishing techniques. Structural changes in the original defect pattern due to oxidation can be studied and a cause and effect relationship between damage and oxidation established. The study of surface characteristics affecting many semi-conductor phenomena such as effective lifetime, noise, and contact potentials can be made in a controlled manner. Modern wafer polishing methods such as the cupric ion or silicon dioxide technique and others can be evaluated in terms of effectiveness of damage removal.