Low-Frequency Noise Characteristics in SONOS Flash Memory with Vertically Stacked Nanowire FETs

Abstract

Low-frequency (LF) noise in a vertically stacked nanowire (VS-NW) memory device which is based on the silicon-oxide-nitride-oxide-silicon (SONOS) configuration is characterized in two different operational modes, an inversion-mode (IM) and a junctionless-mode (JM). The LF noise showed 1/f shape behavior re-gardless of the operational mode and followed the carrier number fluctuation (CNF) model. The CNF model can be described as the interaction between traps in the gate dielectric and the carriers. The LF noise mainly results the trapping/detrapping events caused by the tunneling of charge carriers to and from traps, which are located near the gate dielectric. With regard to the device-to-device variation and quality degradation of the LF noise after iterative program/erase operations, the five-story JM SONOS memory showed comparatively high immunity arising from its inherent bulk conduction and no-junction feature. Despite the harsh fabrication condition used to construct five-story VS-NW, even the five-story JM SONOS memory exhibited LF noise characteristics comparable to those of one-story JM SONOS memory. Thus, the five-story JM SONOS memory is attractive due to its high-performance capabilities and good scalability.