Giuseppe Crisenza

Multilevel flash cells and their trade-offs

In this paper we compare six different multilevel flash cells, viz., common ground, DINOR, AND, AMG, split gate and NAND. The key conclusions are that the hot electron effect lends itself better than tunneling as the multilevel programming mechanism. The common ground cell is the most suitable for multilevel flash cells. The NAND architecture is the least favorable.

A novel method for the experimental determination of the coupling ratios in submicron EPROM and flash EEPROM cells

A novel method for evaluating the coupling ratios alpha /sub G/ and alpha /sub D/ of hot-electron programmable memory cells has been developed. The evaluation is based only on measurements performed on the cell and does not rely on the comparison of the cell with the equivalent MOS transistor. The sensitivity to slight differences between the two structures, which becomes more severe as the scaling-down continues, is thus eliminated. The method allows the coupling ratios to be determined also in those new high-density memory array designs in which it is impossible to obtain the equivalent transistor. The method has been validated on a 0.8 mu m technology EPROM and on a 1.0 mu m technology flash-EEPROM.<<ETX>>