Measurements were made of the Si diffusivity, in film samples, by using isotopically enriched 28Si dioxide layers which permitted relatively low 30Si concentration measurements to be performed by using secondary ion mass spectrometry. Two types of experiment were performed. An excess of 30Si atoms was introduced into a stoichiometric isotopically pure dioxide layer by using ion implantation or a pre-deposition technique. The experiments were representative of any situation in which excess Si atoms were introduced into dioxide layers during Si processing. The estimated diffusivity values were significantly higher than the previously reported values for Si diffusion in a stoichiometric oxide, and were closer to the reported values for excess Si diffusion in an oxide. The results (figure 37) could be described by:

D (cm2/s) = 1.378 x 100 exp[-4.74(eV)/kT]

Diffusivity Measurements of Silicon in Silicon Dioxide Layers using Isotopically Pure Material. D.Tsoukalas, C.Tsamis, P.Normand: Journal of Applied Physics, 2001, 89[12], 7809-13

Figure 38

Diffusion of Si in SiO2