Radiation hard LOCOS field oxide

It is known that radiation hard field oxides (FOX) can be produced by combination of a thin thermal oxide and a thick P- or As-doped deposited oxide. The doping atoms serve as recombination centers and electron traps for radiation induced charges. This results in a distinctly lower oxide charge at the Si/SiO/sub 2/ interface compared to conventional thermal oxides and, therefore, higher radiation hardness. The radiation resistance of thermally grown FOX for LOCOS isolation cannot be improved much by changes in oxidation parameters. The newly developed radiation hard FOX is produced by local oxidation of P-doped poly-Si. This method preserves the advantages of the LOCOS technology. To distinguish this process from the regular LOCOS process we termed it LOPOX (Local Polysilicon Oxidation). Even with low doping concentrations radiation hardness is improved considerably compared to conventional thermal oxides.<
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