Direct Field Effect of Neighboring Cell Transistor on Cell-to-Cell Interference of nand Flash Cell Arrays

We introduce the concept of the direct field effect of a neighboring cell transistor on the cell-to-cell interference of NAND Flash cell memory. As the cell size reduces to below 50 nm, the electric field of the adjacent cell transistor directly influences the shallow-trench isolation corner of a selected cell transistor, provoking a significant cell V _TH shift. In a way different from how conventional parasitic capacitance-coupling effect alters only the floating gate voltage, the direct field effect changes the cell V _TH intrinsically and provokes an intense V _TH shift, particularly in word-line direction (x-direction), due to severe boron segregation on a channel edge. In a 45-nm design-rule nand Flash cell, this effect provokes 0.67 V of the V _TH shift in the x-direction, while a conventional capacitance-coupling effect yields 0.28 V.