Diffusion characteristics of As, P, and B in SiO2 films as thin as 35 A have been studied using doped polysilicon/ Si02/Si structure samples. A two-boundary model can well characterize the As and P diffusion and low concentration B diffusion, where the derived diffusion coefficients and segregation coefficients are given by DSiO2 as (cm2 s-l) = 2.3 x 103 exp (-5.3 eV/kT), mAs = 1.8 x 107 exp (-1.3 eV/fcT), Dsio2-p (cm2 s_1) = 1.2 x 102 exp (-4.1 eV/kT), mP = 9.2 x 105 exp (-1.0 eV/kT), DSio2-B (cm2s-1) = 0.31 exp (-4.2 eV/kT), mB = 30 exp (-0.33 eV/kT). For diffusion of high B concentrations, anomalous enhancement of diffusion has been observed at long diffusion times t, and thin Si02 film thickness. Based on the change of bond characteristics in Si02 observed by SIMS and ESCA, the enhancement has been explained by assuming that the changed layer with a high diffusion coefficient grows in Si02 with a thickness dF = V/ct, where the rate constant k is given typically by fc(cm2 s’1) = 2.5 x 107 exp (—6.4 eV/kT) for a B concentration in polysilicon Cpoly = 2.5 X 1020cm-3.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry