The redistribution of Fe which had been implanted into the oxide layer of Si-on-insulator structures was measured by means of secondary ion mass spectroscopy after annealing at 900 to 1050C. The diffusion of Fe was found to be much faster in the oxide which had been prepared using the separation-by-implantation procedure than in the thermally grown oxide of bonded and etched-back structures (figure 36). In the latter case, the Fe diffusivity exhibited an activation energy of 2.8eV. In the other oxide, the diffusivity depended only weakly upon temperature; thus indicating an essentially activation-free diffusion mechanism. The gettering of Fe at defects in these wafers was observed. No segregation of Fe was detected at the SiO2/Si interface.

Diffusion of Iron in the Silicon Dioxide Layer of Silicon-on-Insulator Structures. O.Kononchuk, K.G.Korablev, N.Yarykin, G.A.Rozgonyi: Applied Physics Letters, 1998, 73[9], 1206-8