OPTICAL CHARACTERIZATION OF SIMOX STRUCTURES FORMED BY SUCCESSIVE IMPLANTATION AND ANNEALING

The analysis of SIMOX structures obtained after successive implantatio n and annealing processes has been performed by Raman scattering and F TIR spectroscopy measurements. The experimental data show the presence of tensile stress in the top Si layer of the SIMOX structure, as well as likely compressive stress below the buried oxide layer. Tensile st ress in the top Si layer is higher after the third implantation step, which correlates with the lower concentration of structural defects ob served by TEM. Annealing this sample leads to an essentially stress-fr ee Si structure. Measurements performed directly on the BOX suggest co mpressive stress below this layer, which is also relieved after anneal ing. FTIR data also confirms the formation of a stoichiometric buried oxide which shows some structural differences when compared to a therm al oxide.