Ion implantation and diffusion of Al in a SiO2/Si system

The diffusion and segregation of ion implanted Al in SiO2 and Si layers were studied for several experimental conditions. Al ions were implanted into SiO2, Si and through a SiO2 layer into Si substrates at several energies (80, 300, 650 and 6000 keV) and doses (3.4.1014-1.1015 cm-2). The Al diffusion coefficient in SiO2 was measured at 1200 C for times up to 5 days, and it results five orders of magnitude lower than in Si. The experiments show that the Al atoms implanted into Si do not out-diffuse during thermal treatments from the SiO2 capping layer, but segregate at the SiO2/Si interface. The high segregation coefficient gives rise to a trapping of Al into the oxide layer comparable to the out-diffusion of Al from uncapped Si substrates. The determined parameters for Al diffusion and segregation in the SiO2/Si system were introduced in a simulation code to calculate the Al diffusion profiles which result in agreement with the experimental data. (orig.)