Chemical Kinetics of Hydrogen and Pb Centers
Electron paramagnetic resonance (EPR) measurements indicate that Pb centers, which are a dangling-bond type of defect at the (111) Si-Si02 interface, can be passivated with H2 at a rate which is proportional to the H2 concentration in the thermal oxide and the interfacial density of Pb centers. This process is characterized by an activation energy, Ef, of 1.66 ± 0.06 eV with a second-order pre-exponential factor, k(2)of, of 1.94 (+2./-1.) x 10−6 cm3/sec for temperatures between 230 and 260°C. The passivation process is demonstrated to be consistent with a chemical process in which H2 molecules, during the course of their diffusional motion among the accessible interstices of the Si02 network and the reaction site at Pb centers, react directly with Pb centers. EPR measurements indicate that passivated Pb centers, denoted as HPb, in effect dissociate in vacuum above 550°C.
KeywordsElectron Paramagnetic Resonance Thermal Oxide Passivation Process Interfacial Density Vitreous Silica
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