Mechanical properties of nitrogen-doped CZ silicon crystals

We investigated the effect of the nitrogen doping level on plastic properties of 300 mm silicon material in the temperature range between 650degreesC and 1000degreesC. Undoped, low N-doped, and high N-doped materials were examined. The dependence of the upper and lower yield point and the size dependence of indentation related dislocation rosettes on temperature were obtained. An increase in the nitrogen concentration leads to enhanced upper and lower yield points. Possible mechanisms of interaction of dislocations with impurities resulting in hardening of silicon single crystals are discussed. Finite element method (FEM) calculated data of bearing stress observed in 300 mm Si wafers annealed in a vertical furnace are compared with measured upper yield point values. At high nitrogen concentration the tolerable process temperatures, where plastic flow of Si wafers under load can be avoided, are significantly increased. (C) 2003 Elsevier Science Ltd. All rights reserved.