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Professor Peter Ashburn, Director & Technical Advisor, Innos, Southampton, UK

ABSTRACT

Boron diffuses relatively quickly in silicon at temperatures typically used for anneals in CMOS and bipolar technologies making it hard to precisely control the location of the doping profiles and very difficult to form very shallow boron-doped junctions. This problem is much worse when anneals are carried out after ion implantation because of transient enhanced diffusion, which is caused by damage introduced during ion implantation, and arises because dopants diffuse with the aid of point defects, interstitials in the case of boron. Transient enhanced diffusion can enhance the diffusion coefficient of boron by as much as an order of magnitude during the short anneals typically used in rapid thermal annealing.