Diffusivity measurements of silicon in silicon dioxide layers using isotopically pure material

We report measurement of the silicon diffusion coefficient in silicon dioxide films using isotopically enriched Si-28 silicon dioxide layers that enable relatively low Si-30 concentration measurements to be performed using secondary ion mass spectrometry. Two types of experiments are made. Si-30 atoms are introduced in excess in a stoichiometric isotopically pure silicon dioxide layer either by ion implantation or by a predeposition technique. These experiments are representative of any physical situation in which excess silicon atoms are introduced into silicon dioxide layers during silicon processing. The estimated diffusivity values are significantly higher than previously reported values for Si diffusion within a stoichiometric oxide and closer to reported values for excess Si diffusion within an oxide. The activation energy of the diffusivity is found to be 4.74 eV. (C) 2001 American Institute of Physics.