Dipolar relaxation in the buried insulator of SIMOX structures

It is pointed out that the quality of the SIMOX (separation by implanted oxygen) insulator can be evaluated by a DLTS-like technique where fully integrated devices are not used. The method consists of polarizing the dipole-defects, which are present in the buried insulator, by electrical pulses applied to the silicon substrate, to accumulate mobile charges at each Si-SiO₂ interface. After each pulse the insulator polarization is compensated only by the mobile charges. The dipole relaxation of SIMOX buried oxide layers was studied using, alternatively, unprocessed material for the conductance method and MOS capacitors, formed by removing the Si overlayer, for the capacitance one. The spectra obtained from each method are not similar, indicating an absence of symmetry on the distribution of dipole defects on each side of the buried insulator