Silicon wafer oxygenation from SiO2 layers for radiation hard detectors

Abstract

Radiation produces lattice damage in silicon by displacing the atoms from their original positions and thereby generating the corresponding defects. As a result, new states are created in the semiconductorforbidden band gap, negatively affecting the electrical performance of the devices. Endurance to radiation can be improved by having a high oxygen concentration in the silicon. For detector fabrication, high resistivity silicon is also needed, thus float zone wafers are preferred; however, this kind of material exhibits a low oxygen concentration. Although different ways to incorporate oxygen in float zone silicon have been proposed, all of them imply modifications during the ingot growth. Thermal diffusion from SiO2 layers on polished wafers is an interesting alternative to improve their oxygen content. Different thermal processes aimed at obtaining oxygen enriched silicon for the fabrication of radiation hard detectors have been tested. Attention has also been paid to carbon introduction during processing since, high concentrations of this element has been proved deleterious.