Gettering of Cu by He-induced cavities in SIMOX materials

Gettering of Cu impurities to He-implantation induced cavities in separation by implantation of oxygen (SIMOX) materials has been investigated by means of cross-sectional transmission electron microscopy and secondary ion mass spectroscopy. The cavities were introduced beneath the buried oxide layer (BOX) in SIMOX substrates by He⁺ implantation (9 × 10¹⁶/cm², 60 keV) and subsequent annealing7 The results indicate that these cavities are strong gettering sites for Cu impurities which have been implanted into the top Si layer of SIMOX. After a 1000 °C annealing, 80% of the initially implanted Cu impurities in the top layer have diffused through the buried oxide layer to be captured by the cavities. The gettering effect of these He-induced cavities is much stronger than the damage region beside the BOX. The buried oxide in SIMOX does not appear to prevent the movement of Cu at 1000 °C. He⁺ implantation-induced cavity has been demonstrated to be an attractive method to remove Cu impurities away from the top Si layer in SIMOX wafers.