A FRACTURE CRITERION FOR GALLIUM-ARSENIDE WAFERS

The fracture of single crystal gallium arsenide (GaAs) semi-conducting wafers was studied. Prismatic beam specimens, cut at different crysta llographic orientations from thin wafers, were loaded to failure in fo ur-point bending. Fracture in these crystals occurred predominantly on the {110} family of crystallographic planes. The critical normal and shear stresses on the primary {110} failure planes of the specimens at failure were calculated and a plane stress failure envelope was deter mined. A model to predict the likelihood of failure at any stress stat e was developed. Scanning electron microscopic analysis revealed that failure in bending was initiated from surface defects that approximate semi-elliptical cracks on the tension side.