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Studies of the interactions of silicon with H, H2 and O using a novel RF probe technique Li, Hongjun


A radio frequency technique was developed for measuring steady state, photo-induced, free carrier densities in indirect-bandgap semiconductors. This new in situ technique was then used to study the effects of H-atoms on the SiO₂/Si interfacial trap densities and to study the silicon surface and bulk chemistry during gate oxide growth with a remote O₂ plasma, annealing in H₂ , and the effect of the exposure of silicon substrates to atomic hydrogen. It is found that: (1) Gate oxides with interface trap levels that are as low as those present in thermally grown oxides can be grown at temperatures below 450 °C with atomic oxygen and subsequent annealing in the presence of H2. (2) Boron in p-type silicon can be passivated by hydrogen, which is present in the1 bulk when the crystal is annealed at temperatures between 360 and 450 °C, forming a B-H complex. Dissociation of the B-H complex at temperatures above 450 °C re-activates the boron as an acceptor. (3) Adsorption of O₂ and H₂ on freshly cleaned p-type silicon surfaces decreased the photo-generated carrier concentration which is interpreted in terms of an increase in the width of the depletion layer at the surface. (4) Exposure of a SiO₂/Si interface to H-atoms resulted in the formation of carrier traps other than Pb centers. At temperatures below 100 °C trap formation rates were found to show a first order dependence on the H-atom concentration with an activation energy of 0.15 ± 0.02 eV. 1 At higher temperatures, the reverse reaction and another process, which also reduces the traps formed by H-atoms, were observed. The kinetics and mechanisms of these processes are discussed in detail

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