An electron paramagnetic resonance study of defects in PECVD silicon oxides

Electron paramagnetic resonance (EPR) has been used to determine how the type and population of paramagnetic defects are altered firstly by changes to the composition of oxides grown on silicon by plasma enhanced chemical vapor deposition (PECVD) and secondly by subsequent anneal treatments of the various oxide films. Silicon oxide films with refractive index, n, of 1.464, 1.487, 1.508 and 1.536 and thickness of 1 μm to 3 μm were studied; those of higher index have a higher silicon content. Only E′ centers are detected in films with n=1.464 and 1.487. Raising n to 1.508 leads to the introduction of other types of paramagnetic centers and a large increase in the average total spin concentration. Increasing n further to 1.536 produces a further small increase in average spin concentration. Identities are proposed for the additional types of defect and the dependence of their population on anneal temperature is also reported.