Elimination of Defects in Laser-Recrystallized SOI by Stress Relief

Abstract

AbstractWe report the application of a stress-relief technique aimed at reducing the density of dislocations and subgrain boundaries in laser-recrystallized Silicon-On-Insulator (SOI) material. By providing alternate mechanisms for relieving the stresses responsible for defect generation in the Si film, it is possible to exercise a large degree of control over the subgrain boundary density. Large areas of SOI material completely free of dislocations and subgrain boundaries have been obtained by inserting a low-viscosity layer under the silicon film and using an appropriately shaped cw laser beam as the heat source. During the process of zone-melt recrystallization this layer softens and provides an alternative stress relief mechanism, thus reducing the mechanical constraint on the growing crystal. Several examples of subgrain boundary control are described, which have resulted in crystalline regions in excess of 300 μm by several millimeters completely free of low-angle grain boundaries and dislocations.