PINNING EFFECT ON PUNCHED-OUT DISLOCATIONS IN SILICON-WAFERS INVESTIGATED USING INDENTATION METHOD

The mechanical strength of silicon wafers was investigated using the i ndentation method. Sizes of rosette patterns L, generated during annea ling at 900 degrees C for 3 min, were measured for as-grown floating z one (FZ) and Czochralski (CZ) silicon wafers. It was found that (1) th e 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 c oncentration ([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, i n 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 di slocations by oxide precipitates or stacking faults was also investiga ted using the indentation method. It was found that precipitates, of w hich the density was approximately 1 x 10(9)/cm(3) and the average siz e Aias lower than approximately 500 nm; did not affect the rosette siz es L. On the other hand, stacking faults, of which the density was app roximately I x 10(7)/cm(3) and the average size was approximately 50 m u m, have shown the pinning effect.