Avalanche Breakdown in Polycrystalline Silicon Films

Electrons can flow from the field plate of a silicon gate MOS, through the gate oxide, to the contacts or the channel, if the field plate is brought into avalanche. This leads to shifts in the transistor threshold voltage, and premature discharge of floating nodes. The characteristics of p-type polycrystalline silicon films in MOS avalanche have been examined. Avalanche injected electron currents in the gate oxide up to 1 mA/cm2 have been measured at 500 KHz. Trapping of electrons occurs at a distance of 100 Ã… from the oxide interface, and appears to depend strongly on the boron content of the gate oxide.