A convergence scheme for over-erased flash EEPROM's usingsubstrate-bias-enhanced hot electron injection

A novel convergence scheme using substrate-bias-enhanced hot electron injection is proposed to tighten the cell threshold voltage distribution after erasure for stacked gate flash EEPROM's. By lowering the drain voltage and increasing the magnitude of the negative substrate bias voltage, the substrate current is reduced but the hot electron gate current is enhanced significantly, and the convergence time is shown to be more than a hundred times shorter than the previous scheme. With the convergence operation performed near the ON-OFF transition region of the cells, the total drain current for all the converged cells is reduced and low power consumption is achieved