Failure Mechanism in MOS Gates Resulting from Particulate Contamination

Particulate contamination present on the silicon surface was found to react or flux with the growing SiO2 during oxidation, creating localized regions high in ionic contamination. These regions, which are typically one micrometer or less in diameter, show up readily in the SEM due to their high conductivity. During electrical stressing, these regions give rise to a thermal breakdown, which is voltage, temperature, and time dependent. X-ray microanalysis has shown that these defect regions typically contain sodium and calcium, and experiments have shown that the chemicals used during processing are a major source of this particulate contamination.