High dielectric constant materials such as Barium Strontium Titanate (BST) will be necessary for future (>1 gigabit) high-density memories. The integration of a new material into well-established silicon processing facilities is a complex task. Through this work, we hope to take a step towards that end.; Special electrode materials are necessary to withstand the severe conditions required for BST processing. Platinum (Pt) has been the material of choice for this purpose. However, the poor diffusion barrier properties and alpha particle emission problem with Pt prompted the search for alternate electrode materials. We propose using Ir electrodes to overcome the difficulties associated with platinum.; High quality Ir (ρ = 7μΩ-cm) and IrO2 (75μΩ-cm) films were deposited using DC magnetron sputtering. The thermal stability of these films under oxidizing, reducing and neutral conditions was studied. While IrO2 may not be a suitable electrode material due to its instability in forming gas (N2/H2), Ir appears to be a promising candidate. Hence, we studied the effect of processing parameters on the electrical characteristics of RF sputtered BST thin films on Ir electrodes. Three different film compositions Ba0.5Sr0.5TiO 3, Ba0.4Sr0.6TiO3 and SrTiO3 were studied. Dielectric films (400Å–500Å thick) with high dielectric constant (ϵr = 350) and low leakage currents (J = 5 × 10−8 A/cm2) were obtained. However, the dielectric dispersion (frequency dependent loss in capacitance) for BST films with Ir electrodes was high (2.65% loss per decade of frequency).; The dielectric dispersion in BST films was studied in detail. A model was developed to separate the electrode-dielectric interface effects from that of the film itself. Based on the results, a new multi-layer capacitor structure was proposed and successfully fabricated to yield a combination of high dielectric constant and low dielectric dispersion. We also studied the effect of external mechanical stress on the electrical characteristics of BST thin films. We find that unlike in the case of materials with a large piezoelectric coefficient e.g. Pb(Zr,Ti)O3, BST thin films respond differently to external mechanical stress. The mechanism may be related to the electrode-dielectric interface rather than piezoelectricity.
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机译：高介电常数材料，例如钛酸锶钡（BST），对于将来（> 1吉比特）的高密度存储器将是必需的。将新材料集成到完善的硅加工设备中是一项复杂的任务。通过这项工作，我们希望朝着这一目标迈出一步。必须使用特殊的电极材料才能承受BST处理所需的严酷条件。为此，铂金（Pt）已成为首选材料。然而，不良的扩散阻挡性能和Pt的α粒子发射问题促使人们寻找替代电极材料。我们建议使用铱电极来克服与铂相关的困难。使用直流磁控溅射沉积高质量的Ir（ρ=7μΩ-cm）和IrO 2 （75μΩ-cm）膜。研究了这些膜在氧化，还原和中性条件下的热稳定性。尽管IrO 2 由于其在气体形成中的不稳定性（N 2 / H 2 ）可能不是合适的电极材料，但Ir似乎是有前途的候选人。因此，我们研究了工艺参数对Ir电极上RF溅射BST薄膜电学特性的影响。三种不同的薄膜成分Ba 0.5 Sr 0.5 TiO 3 ，Ba 0.4 Sr 0.6 研究了TiO 3 和SrTiO 3 。具有高介电常数（＆epsiv; r = 350）和低泄漏电流（J = 5×10 -8 A / cm 2 ）。但是，带有Ir电极的BST膜的介电色散（电容的频率相关损耗）很高（每十倍频损耗2.65％）。详细研究了BST膜中的介电弥散。开发了一种模型来将电极-电介质界面效应与薄膜本身的效应分开。根据结果，提出了一种新型的多层电容器结构，并成功地制造出了高介电常数和低介电色散的组合。我们还研究了外部机械应力对BST薄膜电学特性的影响。我们发现，这与压电系数大的材料不同。 Pb（Zr，Ti）O 3 ，BST薄膜对外部机械应力的反应不同。该机制可能与电极-介电界面有关，而不是与压电有关。
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