Upper yield point of large diameter silicon

The temperature and shear strain rate dependence of the upper yield point o f a few kinds of large diameter silicon crystals was studied. Crucial mater ial attributes, such as doping level, initial oxygen content, and the state of oxygen aggregation after thermal treatment, were taken into account. Ov erall experimental results show that the deformation behavior of the materi als studied here is similar; there is no difference observed between high a nd low boron-doped 200-mm-diameter and 300-mm-diameter silicon crystals. Fu rther, the right choice of sample orientation and shear strain rate used in experiments have been proved to be significant for the characterization of mechanical strength of silicon wafers subjected to process load. Very low strain rates and forces lying in crystallographic < 110 > directions genera te local regions of plastic flow caused by an extremely low yield stress. T he results allow the optimization of critical high temperature processes us ed for materials technology and device fabrication. (C) 2001 Elsevier Scien ce B.V. All rights reserved.