Influence of low temperature preanneals on dopant and defect behavior for low energy Ge preamorphized silicon

Abstract

The hold temperature of an anneal plays a crucial role in controlling the final activation and diffusion of dopants. A study on the influence of a variety of low temperature preanneals on the behavior of dopants and defects for low energy germanium preamorphization is conducted. Si wafers are preamorphized with 1×1015 cm−2 Ge+ at energies of 10, 12, 15, 20, and 30 keV and implanted with 1×1015 cm−2, 1 keV B+. Furnace preanneals are performed at 450, 550, 650, and 750 °C; the samples are subsequently subjected to a spike RTA at 950 °C. Defect analyses indicate an energy threshold above which the preanneal has an effect on the defect density. Further experiments are conducted on the 10 keV Ge+ preamorphizing implant in which the second anneal step is conducted at 750 °C for various times. An analysis of the defect evolution with time reveals that the evolution does not follow previously reported Ostwald ripening-type behavior. The microstructure is populated with very small dot-like defects, which simply dissolve with time, suggesting that the boron may play some role in the defect evolution.