Abstract
NAND Flash memories have gained tremendous attention owing to the increasing demand for storage capacity. This implies that NAND cells need to scale continuously to maintain the pace of technological evolution. Even though NAND Flash memory technology has evolved from a traditional 2D concept toward a 3D structure, the traditional reliability problems related to the tunnel oxide continue to persist. In this paper, we review several recent techniques for separating the effects of the oxide charge and tunneling current flow on the endurance characteristics, particularly the transconductance reduction (ΔGm,max) statistics. A detailed analysis allows us to obtain a model based on physical measurements that captures the main features of various endurance testing procedures. The investigated phenomena and results could be useful for the development of both conventional and emerging NAND Flash memories.
Highlights
Technique for Profiling theThe emergence of NAND Flash memories has revolutionized the data storage industry over the last few decades
The midgap voltage (∆VMG ) during programming and erasing (P/E) operations is described by a set of two components [32]: the first is the electrostatic shift (ES) that is caused by the creation of oxide trapped charges (Q T ), and the other is the tunneling shift (TS) that is related to the change in the number of floating-gate charges (Q floating gate (FG) )
To overcome the limitations of the above-mentioned approaches, we proposed a statistical transconductance reduction (∆Gm,max ) method [39], which enables the extraction of Q T from Q FG in both 2D and 3D NAND memories
Summary
The emergence of NAND Flash memories has revolutionized the data storage industry over the last few decades. Its application range has been expanded such that it has become the main storage element, in that solid-state drives (SSDs) are gradually replacing hard disk drives (HDDs) [8,9]. It is increasingly adopted for enterprise-class storage systems. NAND cells during programming and erasing (P/E) operations [31] This mechanism leads to the formation of trap states in the tunneling oxide, and degrades the oxide reliability. Overcoming the reliability problems related to the oxide trap is critically important for the development of future advanced NAND Flash memories
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