Hi-MNOS II Technology for a 64-kbit Byte-Erasable 5-V-Only EEPROM

Improved high-performance MNOS (HiMNOS II) technology has been developed for application to a byte-erasable 5-V only 64-kbit EEPROM. A minimum feature size of 2 μm and scaling theory implementation for the MNOS device have led to the realization of a small cell size of 180μm2, a low programming voltage of 16 V, and a high packing density of 64 kbits. The high-voltage structure of the MNOS device, as well as the high-voltage circuit technology, has been developed to eliminate dc programming current in the memory array and the high-voltage switching circuits for the use of on-chip generated programming voltage. This voltage is regulated with an accuracy of ±1 V by using a Zener diode formed in a p-type well. Moreover, in order to accomplish reliable byte erasing, high-voltage switching circuits and their control logic have been carefully designed so as to eliminate the possibility of erroneous writing or erasing due to a timing skew of the high-voltage application to the memory cells. The obtained 64K EEPROM chip shows such superior characteristics as a fast access time of 150 ns, low power dissipation of 55 mA, high-speed write and erase times of less than 1 ms, and high endurance of less than 1-percent failure after 10⁴ write/erase cycles.