ZrO₂ films with ultrathin Al₂O₃ layers have effectively contributed to the miniaturization of dynamic random access memory (DRAM) capacitors for many years. However, as memory devices continue to shrink, higher dielectric constants are required to maintain cell capacitance. To address this challenge, research has explored the use of tetragonal HfO₂ layers, which theoretically possess a higher dielectric constant than ZrO₂, as dielectrics. However, the thermodynamically stable phase of HfO₂ is monoclinic with a lower dielectric constant, necessitating a phase transition to the tetragonal form for DRAM capacitor applications. Although attempts have been made to induce this phase transition to achieve high dielectric constants by applying an HfO₂/ZrO₂ layered structure or doping HfO₂ with elements such as Zr, Al, and Si, significant challenges remain in completely eliminating the monoclinic phase or implementing a pure tetragonal phase of HfO₂. In this study, we systematically investigated the crystallinity changes and improved the electrical properties of HfO₂/ZrO₂ layered structures with Al doping in the HfO₂ layers. Our findings demonstrate that optimizing the partitioning of the ZrO₂ and HfO₂ layers, combined with Al doping, effectively achieves equivalent oxide thickness scaling.

中文翻译：

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Al 掺杂对高 k 应用中 HfO2/ZrO2 层状结构的结构和电学性能的影响


多年来，具有超薄 Al₂O₃ 层的 ZrO₂ 薄膜有效地促进了动态随机存取存储器 （DRAM） 电容器的小型化。然而，随着存储器件的不断缩小，需要更高的介电常数来维持电池电容。为了应对这一挑战，研究探索了使用四方 HfO₂ 层作为电介质，理论上它具有比 ZrO₂ 更高的介电常数。然而，HfO₂ 的热力学稳定相是单斜相，具有较低的介电常数，因此 DRAM 电容器应用需要相变为四方形式。尽管已经尝试通过应用 HfO₂/ZrO₂ 层状结构或用 Zr、Al 和 Si 等元素掺杂 HfO₂ 来诱导这种相变以实现高介电常数，但在完全消除单斜相或实现 HfO₂ 的纯四方相方面仍然存在重大挑战。在这项研究中，我们系统地研究了 HfO 2/ZrO₂ 层状结构的结晶度变化并改善了 HfO₂/ZrO₂ 层状结构的电性能。我们的研究结果表明，优化 ZrO₂ 和 HfO₂ 层的分配，结合 Al 掺杂，可以有效地实现等效的氧化物厚度缩放。