DAMAGE ACCUMULATION DURING HIGH-DOSE, O+ IMPLANTATION IN SI

High-dose O+ implantation of Si between 450 and 500 keV is investigated to better understand the mechanisms responsible for ion-induced growth of damage, especially in the top Si layer ahead of the region where a buried oxide forms. Two distinct states are identified in this Si layer over an extended range of fluence (greater-than-or-equal-to 10(18) cm-2): a low-density defect state and a high-density one. These states are observed at all irradiation temperatures, including ambient temperature. The transition between the states is rather abrupt with the onset at a high fluence, which decreases with decreasing temperature. The existence of the low-density state offers a possibility of forming dislocation-free silicon-on-insulator wafers, even for ambient temperature irradiations. A processing method for achieving such wafers is discussed.