Effect of the Ge preamorphisation dose on the thermal evolution of End of Range defects

Abstract

In this paper, we study the effect of the Ge⁺ preamorphisation dose on the thermal evolution of End of Range (EOR) defects upon annealing. Amorphisations were carried out by implanting Ge⁺ at 150 keV to doses ranging from 1×10¹⁵ ions/cm² to 8×10¹⁵ions/cm². Rapid Thermal Annealing (RTA) was performed for various time/temperature combinations in nitrogen ambient. Plan view transmission electron microscopy under specific imaging conditions was used to measure the size distributions and densities of the EOR defects. We found that for a fixed thermal budget, the increase in the Ge ion dose results in an increase in the defect density but has no effect on the defect size distribution. This invariance of the mean size of defects with respect to the initial supersaturation introduced in the matrix is an expected characteristic of a conservative Ostwald ripening mechanism. Moreover, the total number (N_b) of Si interstitial atoms bound to the EOR defects is a monotonically increasing function of the Ge ion dose. Furthermore, we found that N_b is directly proportional to the number of Si atoms in excess of the vacancies found below the a/c interface as calculated by MonteCarlo simulations. This is consistent with the “excess interstitial” model which explains the origin of the EOR defects.