Abstract
We report the effects of surface damage and crystal orientation on fracture strength of single crystal silicon (SCS) by means of tensile test using electrostatic-force grip. The specimens of three major crystal orientations fabricated from (110) SOI wafer were characterized with different surface morphologies prepared by the specimen patterning process. Our specimen patterning process was composed of Bosch process and wet etching process for surface residue removal. We changed processing time and sequence of the two processes to get different surface morphologies. As result of uni-axial tensile test of 9 types of specimens (length: 120 μm, width: 5 μm, thickness: 5 μm), i.e. specimens of 3 crystal orientations with 3 different surface morphologies, improvement of surface morphology doubled average tensile strength: e.g. <110> strength varied from 1.8 GPa to 3.6 GPa, while average tensile strength difference among crystal orientations was less than 20 % on each fabrication conditions. The fracture surfaces mainly consisted of (111) plane. We found tensile fracture characteristics of 3 crystal orientations: in <100> specimens the fracture origin location changed by the fabrication conditions, while <110> and <111> specimens respectively showed quantitative relationships between surface morphology and tensile strength common to different fabrication conditions. These results are beneficial for tensile strength prediction from surface morphology.
