Differential Hall characterisation of ultrashallow doping in advanced Si-based materials

Strained Si channels are commonly used by manufacturers to enhance CMOS performance and research into novel channel materials (SiGe and Ge) is well underway. How these materials affect the electrical properties of the impurities used to dope them is largely unclear and the ability to accurately characterise dopant activation is key to finding this out. In the case of Si, since much is known about the relationship between carrier concentration and mobility, dopant activation can be assessed by competing techniques, however for the newer materials this information is not available. This paper demonstrates the differential Hall technique as a method capable of satisfying these gaps in our knowledge of dopant activation and mobility. Previously we have shown the technique, which combines Hall effect measurements with successive native oxide removal, can measure independent carrier and mobility profiles with resolution better than 1 nm for B-implanted Si and SOI. Presently we show the technique is extendable to characterise n-type dopants (Sb and As) and importantly, can be applied to novel substrates (focussing here on strained Si). In addition, the inherent assumption of the technique – uniform layer removal – is investigated and shown reasonable. Complementary ion beam analysis is used to show how we investigate and correct for Hall scattering effects and designated software is used to apply necessary corrections, transforming raw data into reproducible and highly resolved, carrier and mobility profiles.