Effects of carbon on charge loss in EPROM structures

Abstract

Charge loss failures on EPROM (erasable programmable read only memory) devices are conclusively linked to the presence of carbon in oxidizing ambients. Oxides grown in hydrogen chloride (HCl) and trichloroethane (TCA) are compared on polysilicon and single crystal substrates. Both product and test structures are used for evaluation oxide quality. Carbon dioxide (CO/sub 2/) injected into HCl oxidation cycles is used to isolate carbon as the cause of device yield degradation. TCA oxidations are shown to be similar in result to CO/sub 2/ enhanced HCl oxidations. Elemental analysis of silicon substrates oxidized in carbon bearing atmospheres reveals an accumulation of carbon at the oxide-silicon interface.<>