Pinning effect on punched-out dislocations in silicon wafers investigated using indentation method

The mechanical strength of silicon wafers was investigated using the indentation method. Sizes of rosette patterns L, generated during annealing at 900 degrees C for 3 min, were measured for as-grown floating zone (FZ) and Czochralski (CZ) silicon wafers. It was found that (1) the rosette size L of FZ wafers was larger than that of CZ wafers and (2) L decreases in proportion to the -2/3 power of interstitial oxygen concentration ([Oi]) for CZ wafers ([Oi] = 3.7-15.5 x 10(17) atoms/cm(3)). From the experimental results, it was concluded that the wafers, in which [Oi] was larger than approximately 2 x 10(17) atoms/cm(3), had the ability to pin on dislocation movements. The pinning effect on dislocations by oxide precipitates or stacking faults was also investigated using the indentation method. It was found that precipitates, of which the density was approximately 1 x 10(9)/cm(3) and the average size Aias lower than approximately 500 nm; did not affect the rosette sizes L. On the other hand, stacking faults, of which the density was approximately I x 10(7)/cm(3) and the average size was approximately 50 mu m, have shown the pinning effect.