Oxide charges induced in thermal silicon dioxide by scanning electron and laser beam annealing

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Abstract
Oxide charge generation resulting from the exposure of Si/SiO2 structures to scanning electron and laser beams during the anneal of ion implantation damage was investigated. Fixed oxide charge, interface trapped charge, and oxide trapped charge densities were measured by use of high-frequency, quasistatic C-V, and avalanche carrier injection techniques. The effective density of traps induced by the exposure of thin oxides to electron beam fluences of 0.39–3.10×10−2 C/cm2 at 5 kV was found to be an order of magnitude larger than in control wafers. This effect was primarily due to neutral trap formation. Although interface charges could be reduced to an acceptable level by a post-irradiation anneal (400 to 500 °C) in forming gas, neutral traps could not be annealed satisfactorily. It was also found that scanned electron-beam annealing from the backside of the wafer or laser annealing constitute viable alternatives with minimal effects on the densities of fixed oxide charges in the silicon dioxide layer.