Programming mechanism of polysilicon resistor fuses

The programming characteristics of polysilicon resistor fuses were investigated. It was found that an open circuit occurs only after the fuse makes a transition to a second-breakdown state in which the current flow is mainly through a molten filament. Filamentary current flow is stable since the resistivity of silicon decreases abruptly upon melting. A simple model was developed which explains the observed characteristics. Fuse opening occurs when the current in second breakdown exceeds a critical current Iminwhich depends strongly on the fuse thickness and the presence or absence of a passivation layer over the fuse. The gap forms at the positive end, suggesting that the silicon ions move by drift in the applied electric field.