A NEW WRITE ERASE METHOD TO IMPROVE THE READ DISTURB CHARACTERISTICS BASED ON THE DECAY PHENOMENA OF STRESS LEAKAGE CURRENT FOR MASH MEMORIES/

This paper describes a new write/erase method for Flash memory to impr ove the read disturb characteristics by means of drastically reducing the stress leakage current in the tunnel oxide. This new write/erase o peration method is based on the newly discovered three decay character istics of the stress leakage current, The features of the proposed wri te/erase method are as follows: 1) the polarity of the additional puls e after applying write/erase pulse is the same as that of the control gate voltage in the read operation; 2) the voltage of the additional p ulse is higher than that of a control gate in a read operation, and lo wer than that of a control gate in a write operation; and 3) an additi onal pulse is applied to the control gate just after a completion of t he write/erase operation. With the proposed write/erase method, the de gradation of the read disturb life time after 10(6) write/erase cycles can be drastically reduced by 50% in comparison with the conventional bipolarity write/erase method used for NAND-type Flash memory. Furthe rmore, the degradation can be drastically reduced by 90% in comparison with the conventional unipolarity write/erase method for NOR-, AND-, and DINOR-type Flash memory. This proposed write/erase operation metho d has superior potential for applications to 256 Mb Flash memories and beyond.