Modelling the upper yield point and the brittle-ductile transition of silicon wafers in three-point bend tests

Steve G Roberts (1) , Peter B Hirsch (2)

1 Materials Science
2 Materials

Three point bend tests carried out by Folk [1] on initially dislocation-free specimens of semiconductor-grade single crystals of Si showed that, for a given strain-rate, above a critical temperature, T_c, and at a certain stress, a large load drop occurs upon yielding and the sample deforms plastically. Below T_c specimens fail by brittle fracture after a small load drop, or at even lower temperatures without apparent prior plastic flow. This paper describes a simple dislocation model and computer simulation to explain the occurrence of a yield drop, the strain-rate dependence of T_c and Folk's etch pit observations of the plastic zone. Good agreement is obtained between the temperature dependence of the upper yield stress and the strain-rate dependence of T_c with the predictions of the model. These parameters are controlled by dislocation velocity.

Mots clés: Physical Sciences

Steve G Roberts, Peter B Hirsch. Modelling the upper yield point and the brittle-ductile transition of silicon wafers in three-point bend tests. Philosophical Magazine, 2006, 86 (25-26), pp.4099-4116. ⟨10.1080/14786430600643308⟩. ⟨hal-00513679⟩