Kang Wangu, Ahn Ji Sang, Lee Jae Hyeon, Choi Byung Joon, Han Jeong Hwan
Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea.
ACS Appl Mater Interfaces. 2024 Oct 23;16(42):57446-57456. doi: 10.1021/acsami.4c14077. Epub 2024 Oct 14.
The continuous miniaturization of dynamic random-access memory (DRAM) capacitors has amplified the demand for electrode materials featuring specific characteristics, such as low resistivity, high work function, chemical stability, excellent interface quality with high-k dielectrics, and superior mechanical properties. In this study, molybdenum nitride (MoN) films were deposited using a plasma-enhanced atomic layer deposition (PEALD) employing bis(isopropylcyclopentadienyl)molybdenum(IV) dihydride and NH plasma for DRAM capacitor electrode applications. Depending on the deposition temperatures of the PEALD MoN films ranging from 200 to 400 °C, the Mo/N ratio and crystal structure varied, transitioning from the cubic NaCl-B1-type MoN phase with Mo/N ratio of 1.4 to the cubic γ-MoN phase with Mo/N ratio of 1.9. Notably, MoN films grown at 400 °C exhibited low resistivity (435 μΩ·cm), a high work function (5.28 eV), and superior mechanical hardness (11.3 GPa) compared to ALD TiN films. Despite these excellent properties, the PEALD MoN electrode demonstrated insufficient chemical stability, particularly in terms of oxidation resistance and interface quality with ALD HfZrO (HZO) films. This resulted in poor morphology and the formation of significant oxygen-deficient HZO layers (such as HfO), leading to considerable degradation in the electrical performance of metal-insulator-metal (MIM) capacitors. To mitigate this issue, a thin (2.5-14 nm) ALD TiN layer was introduced as a passivation layer between the MoN bottom electrode and HZO dielectric. The TiN-passivated MoN (TiN/MoN) electrode showed substantially enhanced oxidation resistance and reduced interfacial reactions with the HZO dielectric. Consequently, MIM capacitors with TiN/MoN bottom electrodes demonstrated outstanding electrical performance, including excellent dielectric properties, low leakage current density, and high mechanical strength. Hence, this study proposes a promising candidates for storage nodes in the next-generation DRAM capacitors.
动态随机存取存储器（DRAM）电容器的持续小型化增加了对具有特定特性的电极材料的需求，这些特性包括低电阻率、高功函数、化学稳定性、与高k电介质的优异界面质量以及卓越的机械性能。在本研究中，使用等离子体增强原子层沉积（PEALD）技术，以双（异丙基环戊二烯基）钼（IV）二氢化物和NH等离子体沉积氮化钼（MoN）薄膜，用于DRAM电容器电极应用。根据PEALD MoN薄膜在200至400°C范围内的沉积温度，Mo/N比和晶体结构会发生变化，从Mo/N比为1.4的立方NaCl-B1型MoN相转变为Mo/N比为1.9的立方γ-MoN相。值得注意的是，与ALD TiN薄膜相比，在400°C下生长的MoN薄膜表现出低电阻率（435μΩ·cm）、高功函数（5.28eV）和卓越的机械硬度（11.3GPa）。尽管具有这些优异性能，但PEALD MoN电极表现出不足的化学稳定性，特别是在抗氧化性和与ALD HfZrO（HZO）薄膜的界面质量方面。这导致了不良的形貌以及大量缺氧HZO层（如HfO）的形成，从而导致金属-绝缘体-金属（MIM）电容器的电性能显著下降。为了缓解这个问题，在MoN底部电极和HZO电介质之间引入了一层薄（2.5-14nm）的ALD TiN层作为钝化层。TiN钝化的MoN（TiN/MoN）电极表现出显著增强的抗氧化性，并减少了与HZO电介质的界面反应。因此，具有TiN/MoN底部电极的MIM电容器表现出出色的电性能，包括优异的介电性能、低漏电流密度和高机械强度。因此，本研究提出了一种用于下一代DRAM电容器存储节点的有前途的候选材料。
