An investigation was made of B out-diffusion under various ambient conditions. It was found that the B out-diffusion was significant in an H2 ambient, whereas the out-diffusion was negligible in an N2 or He ambient. By comparing analytical models and experimental data, the diffusivity of B in an H2 ambient was found to be lower than that in an N2 ambient. A significant B out-diffusion in an H2 ambient was attributed to an enhancement of the B transport coefficient at the Si surface. The diffusivity of B in an H2 ambient could be described by:

D (cm2/s) = 9.07 x 102exp[-4.4(eV)/kT]

Negligible out-diffusion in an N2 or He ambient was attributed to a negligible transport coefficient at the surface.

Boron Out-Diffusion from Si Substrates in Various Ambients. K.Suzuki, H.Yamawaki, Y.Tada: Solid-State Electronics, 1997, 41[8], 1095-7

Table 31

Diffusivity of B in Poly-Si Layers