The Effect of Mechanical Stress on Cell Characteristics in MONOS Structures

Abstract

We investigated the impact of mechanical stress on the cell characteristics of metal–oxide–nitride–oxide–semiconductor (MONOS) structures through experimental observations based on a curvature method for residual stress extraction and an analysis of the interface state. Residual stress induced on a substrate was observed to change from compressive to tensile depending on the tungsten process conditions; a high interface trap density was extracted under a high compressive stress environment based on a silicon bonding model. These interface trap densities were suggested as being attributable to a critical factor weakening the leakage characteristics of the MONOS structure. Besides, interface traps interrupted electron tunneling due to unintended charge trapping at the interface, which deteriorated memory characteristics indicated by a reduction in trap density. These results experimentally supported the effects of mechanical stress on device characteristics and reliability, which could be a straightforward way toward understanding the impact of stress for improved future flash memory applications.