Low energy implantation and transient enhanced diffusion: a reliable approach to secondary defect profile measurements

It is well known that low energy implantation is the most promising option for ultra shallow junction formation in the next generation of silicon BiCMOS technology. Among the dopants that have to be implanted, boron is the most problematic because of its low stopping power and its tendency to undergo transient enhanced diffusion and clustering during thermal activation. This paper reports an experimental contribution with the help of secondary defect profiles to our understanding of low energy B implants in crystalline silicon. Shallow p ⁺n junctions were formed by low energy B implantation-10¹⁵ cm^-2 at 3 keV-into a n-type monocrystalline silicon preamorphized with germanium. Rapid thermal annealing for 15 s at 950°C was then used for dopant electrical activation and implantation damage removal. A reliable approach using the secondary defect profiles induced by this process, measured with isothermal transient capacitance in association with deep level transient spectroscopy is proposed. A relatively high concentration of B-related electrically active defects have been obtained up to 3.5 μm into the crystalline silicon bulk