Hideko Oodaira

A 4 Mb NAND EEPROM with tight programmed V/sub t/ distribution

Described is a 5-V-only 4-Mb (512K*8 b) NAND EEPROM (electrically erasable programmable ROM) with tight programmed threshold voltage (V/sub t/) distribution, controlled by a novel program-verify technique. A tight programmed V/sub t/ distribution width of 0.8 V for the 4 Mb cell array is achieved. By introducing a compact row-decoder circuit, a die size of 7.28 mm*15.31 mm is achieved using 1.0 mu m design rules. A unique twin p-well structure has made it possible to realize low-power 5 V-only erase/program operation easily and to achieve 100 K-cycle endurance. >

A high-density NAND EEPROM with block-page programming for microcomputer applications

A high-density, 5-V-only, 4-Mb CMOS EEPROM with a NAND-structured cell using Fowler-Nordheim tunneling for programming is discussed. The block-page mode is utilized for high-speed programming and easy microprocessor interface. On-chip test circuits for shortening test time and for evaluating cell characteristics yield highly reliable EEPROMs. The NAND EEPROM has many applications for microcomputer systems that require small size and large nonvolatile storage systems with low power consumption. >

A 35 ns cycle time 3.3 V only 32 Mb NAND flash EEPROM

A 32 Mb NAND type flash EEPROM in 0.425 /spl mu/m CMOS achieves 35 ns cycle time for data read-out and programming data load by adopting a pipeline scheme. Metal-strapped select gates and boosted word line reduce read-out access time. Tight-programmed cell Vth distribution can be realized by program verify, using a simplified data register circuit. Multiple blocks can be erased at the same time by adopting erase block registers for each block. Simultaneous-erase verify for one block reduces total erase time. All funtions require only 3.3 V power supply.

A quick intelligent program architecture for 3 V-only NAND-EEPROMs

A quick program/program verify architecture with an intelligent verify circuit for 3-V-only NAND-EEPROMs is described. The verify circuit, which is composed of two transistors, provides a simple, intelligent program algorithm for 3-V-only operation. The total programming time is reduced to 50%. By using intelligent verify circuits, the memory cells which require more time to reach the program state are automatically detected. Verify-read, the modification of program data, and data reload are performed simultaneously. The chip size penalty is estimated to be only 1% for a 16-Mb NAND-EEPROM.<<ETX>>

A 4-Mbit NAND-EEPROM with tight programmed V t distribution

The authors describe a 4-Mb NAND-EEPROM with tight Vt (threshold voltage) distribution which is controlled by a novel program verify technique. A tight Vt distribution width of 0.6 V for the entire 4-Mb cell array is achieved, and read margin is improved. A unique twin p-well structure has made it possible to realize low-power 5-V-only erase/program operation easily compared with the previous design

New device technologies for 5 V-only 4 Mb EEPROM with NAND structure cell

Novel device technologies for a 5-V-only EEPROM (electrically erasable programmable read-only memory) with a NAND structure cell are described. By applying half of the programming voltage to unselected bit lines and a successive programming sequence, the NAND structure cell keeps a wide threshold margin. A high-voltage CMOS process realizes reliable programming characteristics. The reliability of the cell has been confirmed experimentally. Using 1.0- mu m design rules, the unit cell area per bit is 12.9- mu m/sup 2/, which is small enough to realize a 4-Mb EEPROM.<<ETX>>