The diffusion of these elements in films which were as thin as 3.5nm was studied by using doped poly-Si/SiO2/Si samples. The data for As diffusion could be described by the expression:

D (cm2/s) = 2300 exp[-5.3(eV)/kT]

while those for P were described by:

D (cm2/s) = 0.012 exp[-4.1(eV)/kT]

and those for B diffusion were described by:

D (cm2/s) = 0.31 exp[-4.2(eV)/kT]

It was found that a 2-boundary model could be used to characterize the As and P diffusion, and low-concentration B diffusion. At high B concentrations, an anomalous diffusion enhancement was detected with increasing annealing time and decreasing film thickness. The enhancement was attributed to the formation of a high-diffusivity layer.

T.Matsuura, J.Murota, N.Mikoshiba, I.Kawashima, T.Sawai: Journal of the Electrochemical Society, 1991, 138[11], 3474-80