Cluster computations, using density functional theory, were performed in order to clarify the diffusion mechanism of an O atom which was adsorbed on a Si surface. The activation energy which was required for O diffusion into the Si substrate was estimated to be equal to 1.6eV. This was relatively small when compared to the value for O diffusion within a Si crystal. The presence of a surface dangling bond was responsible for the lowering of the activation energy, by assisting the generation of an intermediate which was involved in the rearrangement of the Si-O connections. Adsorption of another O atom on the Si surface appeared to enhance further the inward O diffusion.
Inward Diffusion of Oxygen on a Silicon Surface T.Hoshino, Y.Nishioka: Physical Review Letters, 2000, 84[20], 4633-6
Table 12
Out-Diffusion Coefficients for O in Si
O (/cm3) | Dopant | Concentration (/cm3) | Temperature (C) | D (cm2/s) |
1.58 x 1018 | B | 1.8 x 1015 | 800 | 2.45 x 10-13 |
1.58 x 1018 | B | 1.8 x 1015 | 1050 | 3.9 x 10-11 |
1.13 x 1018 | B | 9.2 x 1017 | 800 | 2.44 x 10-13 |
1.13 x 1018 | B | 9.2 x 1017 | 1050 | 4.5 x 10-11 |
1.11 x 1018 | B | 8.0 x 1018 | 800 | 6.8 x 10-14 |
1.08 x 1018 | B | 1.2 x 1019 | 800 | 4.5 x 10-14 |
1.08 x 1018 | B | 1.2 x 1019 | 1050 | 3.9 x 10-11 |
1.52 x 1018 | Sb | 5.0 x 1017 | 800 | 2.45 x 10-13 |
1.52 x 1018 | Sb | 5.0 x 1017 | 1050 | 3.9 x 10-11 |
1.95 x 1018 | As | 1.1 x 1019 | 800 | 1.0 x 10-13 |
1.95 x 1018 | As | 1.1 x 1019 | 1050 | 4.5 x 10-11 |