Dependence of strain at the (111)Si/SiO2 interface on interfacial Si dangling-bond concentration

Thermal oxidation of Si intrinsically gives rise to the generation of defects at the Si/SiO2 interface as a result of mismatch induced stress. In standard thermal (111)Si/SiO2, the dominant paramagnetic defect observed by electron spin resonance (ESR) is the Pb centre (interfacial ·Si≡Si3). In the present study, the inherently incorporated as-grown Pb density (∼4.9×1012 cm−2) was significantly enhanced to various levels, up to 3.1×1013 cm−2, by means of the previously unveiled method for Pb creation through appropriate postoxidation annealing in H2. This resulted, among others, in the observation of a Pb dependent anisotropic broadening of the ESR signal, partially arising from dipolar interaction within the essentially two-dimensional spin system. Successful quantitative simulation by a computational model has enabled detailed analysis of the line broadening mechanisms. The simulations reveal concentration related variations in the strain broadening contribution indicating a growing relaxation of the interfacial stress with increasing [Pb]. The results are discussed in the light of the connection between defect generation and the relaxation of stress.