Abstract
Diffusion characteristics of As, P, and B in 
films as thin as 35 Å have been studied using doped 
structure samples. A two‐boundary model can well characterize the As and P diffusion and low concentration 
diffusion, where the derived diffusion coefficients and segregation coefficients are given by 
, 
, 
, 
, 
, 
. For diffusion of high 
concentrations, anomalous enhancement of diffusion has been observed at long diffusion times 
, and thin 
film thickness. Based on the change of bond characteristics in 
observed by SIMS and ESCA, the enhancement has been explained by assuming that the changed layer with a high diffusion coefficient grows in 
with a thickness 
, where the rate constant
is given typically by 
for a 
concentration in polysilicon
.