电荷俘获存储器数据保持特性第一性原理研究

本文研究HfO₂掺入Al替位Hf杂质和氧空位共同掺杂对电荷俘获型存储器存储特性的影响. HfO₂作为高介电常数材料由于具有缩小器件尺寸、提高器件性能等优势, 被广泛用于CTM的俘获层. 采用MS和VASP研究了HfO₂俘获层中掺入Al对氧空位形成能的影响. 同时计算了两种缺陷在不同距离下的相互作用能. 计算结果表明在HfO₂中掺入Al使得氧空位的形成能降低, 并且三配位氧空位的形成能比四配位氧空位的形成能降低的更多. 通过研究Al和三配位氧空位两种缺陷间不同距离的三种情况, 计算结果表明当缺陷间距为2.107 Å时, 体系的电荷俘获能最大; 量子态数最多; 布居数最小、Al–O键最长. 通过研究三种体系写入空穴后键长的变化, 得出当缺陷间距为2.107 Å时, 写入空穴后体系的Al–O键长变化最小. 以上研究结果表明, 掺入Al后可以有效提高电荷俘获型存储器的数据保持能力. 因而本文的研究为改善电荷俘获型存储器数据保持特性提供一定的理论指导.

Research of data retention for charge trapping memory by first-principles

In this paper, the influence of charge trapping memory storage feature is studied by doping the substitutional impurity Al and introducing oxygen vacancy within HfO₂. HfO₂ is widely used in trapping layer of charge trapping memory, for it belongs to high dielectric constant materials with the abilities to shrink the device size and improve the device performance. Materials studio and Vienna Ab-initio Simulation Package are used to investigate the influence of doping Al on the formation of the oxygen vacancy in HfO₂ as a trapping layer. At the same time, the interaction energy of two defects at different distances is calculated. Results show that doping the substitutional impurity Al reduces the formation energy of oxygen vacancies in HfO₂, and the reduced formation energy of the three-fold-coordinated O vacancy is larger than that of the four-fold-coordinated O vacancy. After having studied three different defect distances between the substitutional impurity Al and the three-fold-coordinated O vacancy, the results indicate that the system acquires the largest charge trapping energy, the most of quantum states, the smallest population number, and the longest Al–O bond length when the distance between the defects is 2.107 Å. Studying the bond length changes of the three systems after writing a hole, we obtain a result that the change of Al–O bond length is the smallest when the distance between defects is 2.107 Å. In conclusion, the data retention in the trapping layer of monoclinic HfO₂ can be improved by doping the substitutional impurity Al. This work will provide a theoretical guidance for the performance improvement in the data retention of charge trapping memory.