The Flash Memory Cell for the Nodes to Come: Material Requirements from a Device Perspective

Abstract

The quest for mass storage and the diversity of end-user applications led to an aggressive scaling of the NAND Flash memory. A key factor to its success is the high density integration potential, which allows fabrication of large memory arrays. Reduction of the feature size below 40 nm may, however, require modifications of the conventional floating gate cell architecture, due to lack of physical space between neighboring cells, which no longer allows wrapping of the control gate over the floating gate. This has consequences on both intra- as well as inter-cell levels, calling for the introduction of high-k dielectrics in Flash memory. In this paper, we take a top-down stance and translate device characteristics into material requirements and/or points of attention that need to be addressed in order to ensure a successful continued scaling of the Flash memory for the upcoming technology generations.

Atomic-Layer Deposition of Lutetium Aluminate Thin Films for Non-Volatile Memory Applications

“…In conclusion, we have demonstrated the atomic-layer deposition of Lu x Al 2−x O 3 thin films using Lu(thd) 3 and TMA in combination with O 3 as an oxidizer. Good control of the deposition process as well as of the Lu/(Lu+Al) composition was obtained.…”

“…To deposit ternary Lu x Al 2−x O 3 , an n:m ALD supercycle was defined, which consisted of n Lu(thd) 3 To study the saturation properties of the ALD process, the influence of Lu(thd) 3 on the growth per cycle was examined after deposition of Lu 2 O 3 . The data in Fig.…”

(Invited) Introducing Lanthanide Aluminates as Dielectrics for Nonvolatile Memory Applications: A Material Scientist's View

“…By contrast, crystalline oxides often show comparably narrow bands of deep traps, which affect leakage much less and are often even beneficial (10). A detailed assessment of trap spectra in rare earth aluminates is beyond the scope of this paper but the behavior was also found to apply to Gd x Al 2-x O 3 and Lu x Al 2-x O 3 (11). Since the physical properties of materials depend crucially on their crystallographic phase, the understanding of the crystallization properties of dielectric thin films is thus an important first step in their assessment.…”

“…Recently, this work has lead to the successful integration of HfO 2 -based dielectrics into commercial MOS devices (2). In addition, high-κ dielectrics are now also being evaluated for DRAM and nonvolatile memory (NVM) applications, such as NAND Flash devices (3). For NVM devices, high-κ dielectrics are of interest as replacements for the conventional oxide-nitrideoxide (ONO) stacks used as the interpoly dielectric (3)(4)(5)(6).…”

“…In addition, high-κ dielectrics are now also being evaluated for DRAM and nonvolatile memory (NVM) applications, such as NAND Flash devices (3). For NVM devices, high-κ dielectrics are of interest as replacements for the conventional oxide-nitrideoxide (ONO) stacks used as the interpoly dielectric (3)(4)(5)(6). High-κ dielectrics may also enable operation of NVM devices at lower voltages because of increased gate coupling (3,5,6).…”