Surface Segregation and Electrical Studies of Heavily Arsenic and Phosphorus in situ Doped Epi and Poly Silicon

Increasing needs of high dynamic performances for heterojunction bipolar transistors led to the use of heavily-doped high quality films. An elegant way to obtain such layers is to use low pressure chemical vapour deposition (CVD) allowing in situ doping. But obtaining well controlled dopant profiles is not easy with n-type dopants that are well known to segregate during heavily-doped silicon epitaxial growth. This phenomenon, linked to the high affinity between n-type dopants and Si surface, lead to important growth rate (GR) reduction and high surface concentration. In this paper, we study this phenomenon for epi and poly Si films and we demonstrate correlation between surface saturation and the poly vs. epi GR evolution for both arsenic and phosphorus doped silicon (Si:As and Si:P). On one hand the bulk concentration is determined via X-ray fluorescence (XRF), after surface parasitic dose elimination. On the other hand electrical parameters are measured via Hall effect technique, we can therefore compare chemical and active dopant concentrations