Self-diffusion of Si in thermally grown SiO2 under equilibrium conditions

Self-diffusion coefficients of Si in thermally grown SiO2 on a semiconductor-grade silicon wafer have been determined at temperatures between 1150 and 1300 degreesC under equilibrium conditions using isotope heterostructures ((SiO2)-Si-nat/(SiO2)-Si-28). Si self-diffusion was induced by appropriate heat treatments, and the diffusion depth profiles of Si-30 isotope from (SiO2)-Si-nat to (SiO2)-Si-28 layers were determined by secondary ion mass spectrometry (SIMS). The diffusion coefficients found in the present study for 1150-1300 degreesC are more than two orders of magnitude smaller than the values measured with semiconductor-grade SiO2 in the presence of excess silicon, i.e., in nonequilibrium conditions, and agree very well with previously reported values of Si self-diffusion in fused silica under equilibrium conditions. (C) 2003 American Institute of Physics.