Spassov Dencho, Paskaleva Albena
Institute of Solid-State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, 1784 Sofia, Bulgaria.
Nanomaterials (Basel). 2023 Aug 30;13(17):2456. doi: 10.3390/nano13172456.
The requirements for ever-increasing volumes of data storage have urged intensive studies to find feasible means to satisfy them. In the long run, new device concepts and technologies that overcome the limitations of traditional CMOS-based memory cells will be needed and adopted. In the meantime, there are still innovations within the current CMOS technology, which could be implemented to improve the data storage ability of memory cells-e.g., replacement of the current dominant floating gate non-volatile memory (NVM) by a charge trapping memory. The latter offers better operation characteristics, e.g., improved retention and endurance, lower power consumption, higher program/erase (P/E) speed and allows vertical stacking. This work provides an overview of our systematic studies of charge-trapping memory cells with a HfO/AlO-based charge-trapping layer prepared by atomic layer deposition (ALD). The possibility to tailor density, energy, and spatial distributions of charge storage traps by the introduction of Al in HfO is demonstrated. The impact of the charge trapping layer composition, annealing process, material and thickness of tunneling oxide on the memory windows, and retention and endurance characteristics of the structures are considered. Challenges to optimizing the composition and technology of charge-trapping memory cells toward meeting the requirements for high density of trapped charge and reliable storage with a negligible loss of charges in the CTF memory cell are discussed. We also outline the perspectives and opportunities for further research and innovations enabled by charge-trapping HfO/AlO-based stacks.
对不断增长的数据存储量的需求促使人们进行深入研究，以找到满足这些需求的可行方法。从长远来看，将需要并采用能够克服传统基于CMOS的存储单元局限性的新器件概念和技术。与此同时，当前的CMOS技术仍有创新之处，可以用来提高存储单元的数据存储能力，例如，用电荷俘获存储器取代当前占主导地位的浮栅非易失性存储器（NVM）。后者具有更好的操作特性，如改善的保持特性和耐久性、更低的功耗、更高的编程/擦除（P/E）速度，并允许垂直堆叠。这项工作概述了我们对通过原子层沉积（ALD）制备的具有HfO/AlO基电荷俘获层的电荷俘获存储单元的系统研究。证明了通过在HfO中引入Al来调整电荷存储陷阱的密度、能量和空间分布的可能性。考虑了电荷俘获层组成、退火工艺、隧穿氧化物的材料和厚度对存储窗口以及结构的保持特性和耐久性的影响。讨论了在优化电荷俘获存储单元的组成和技术以满足高俘获电荷密度和可靠存储的要求且电荷俘获闪存（CTF）存储单元中的电荷损失可忽略不计方面所面临的挑战。我们还概述了基于电荷俘获的HfO/AlO堆叠带来的进一步研究和创新的前景与机遇。
