Structural dynamics of amorphous functional oxides - the role of morphology and electrical stress

非晶功能氧化物的结构动力学 - 形态和电应力的作用

基本信息

批准号：
EP/P013503/1
负责人：
Anthony Kenyon
金额：
$ 93.64万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FP013503%2F1
关键词：
Structural dynamics amorphous functional oxides

项目摘要

Thin oxide films are critical components in a very wide range of electronic devices, including CMOS transistors in microprocessors and memory, piezoelectric and thermoelectric devices and electroluminescent devices. In most cases we assume that the oxide itself is stable under the levels of electrical stress encountered during normal device operation, and a great deal of work has gone into growing extremely high quality films. Nevertheless, recent developments in devices and materials have led to the growing use of amorphous and polycrystalline sub-stoichiometric oxide thin films (SSOTFs). These materials are fundamentally different to their stoichiometric and crystalline cousins - a fact that can have very important consequences for their use in electronic devices - but it is usually assumed that they behave in the same way. It is increasingly clear that this assumption is incorrect.Recent studies, some performed by us, have demonstrated that amorphous sub-stoichiometric oxides are surprisingly dynamic under device-level electrical stress. In the case of silicon oxide, for example, we have shown that electrical stress drives the segregation of the oxide into regions with varying oxygen deficiency, and that such changes can be precursors to major changes in the electrical properties of the material. Our initial results suggest that oxide microstructure determines the ease with which oxygen can segregate, and we have seen, in extreme cases, emission of oxygen from the thin films. These changes can be permanent or they can be reversible, enabling cycling between two or more resistance states. Ultimately, such large-scale changes can lead to device failure. Consequently, by understanding how to control their dynamics we can both understand the early stages of oxide failure, and develop exciting new technologies that exploit the dynamic nature of functional oxides.In this study we propose to investigate these changes using a combination of high resolution experimental characterisation and atomistic modelling of oxygen movement. Studying sub-stoichiometric amorphous oxide thin films is a considerable challenge, both for experiment and for modelling, which is partly why these materials are poorly understood. We will rely on close interaction between experiment and theory to develop, in an iterative process, new models for the structure of substoichiometric amorphous oxides of varying morphology, and their dynamic response to electrical stress. These models will shed light on the physical processes governing electrical changes, and we will use them to generate a set of design rules for material and device optimisation.We have chosen a representative set of materials to study, each of which has important applications in microelectronics. We will grow the materials in-house, giving us control over their composition and structure and enabling rapid feedback from characterisation and modelling. The majority of our characterisation will also be performed at UCL, but we have long-standing and fruitful collaborations with two leading Transmission Electron Microscopy centres - Forschungszentrum Jülich and the Institute of Materials Research and Engineering in Singapore - which will give us access additional world-leading microscopy techniques to study these challenging materials. Our close collaboration with other leading research and development institutions, including our industrial partners, gives us access to further state-of-the-art facilities and industrially relevant samples.

薄氧化物膜是非常广泛的电子设备中的关键组件，包括微处理器和记忆中的CMOS晶体管，压电和热电设备以及电致发光设备。在大多数情况下，我们假设在正常设备操作过程中遇到的电应力水平下，氧化物本身是稳定的，并且在增长极高质量的薄膜方面已大量工作。尽管如此，设备和材料的最新发展导致使用了无定形和多晶亚岩化氧化物氧化物薄膜（SSOTFS）的使用日益增长。这些材料从根本上与其化学计量和结晶表亲不同 - 这一事实可能对它们在电子设备中的使用产生非常重要的后果 - 但通常假定它们以相同的方式行为。越来越明显的是，这一假设是不正确的。我们进行的一些研究表明，在设备级的电应力下，无定形的亚雪白氧化氧化物令人惊讶地动态性。例如，在氧化硅的情况下，我们已经表明，电应力将氧化物的分离驱动到具有不同氧缺乏的区域，并且这种变化可以是材料电性能的重大变化的前体。我们的最初结果表明，氧化物微观结构决定了氧气可以分离的易度性，并且在极端情况下，我们已经看到了从薄膜中排出氧气。这些变化可以是永久性的，也可以是可逆的，从而使两个或多个阻力状态之间骑自行车。最终，这样的大规模更改会导致设备故障。因此，通过了解如何控制其动力学，我们既可以理解氧化物失败的早期阶段，又可以开发令人兴奋的新技术来利用功能氧化物的动态性质。在这项研究中，我们建议使用高分辨率实验表征和原子模型的组合来研究这些变化。在实验和建模方面，研究亚化学计量学无定形氧化物薄膜是一个考虑挑战，这就是为什么这些材料对这些材料的了解不足的原因。我们将依靠实验与理论之间的紧密相互作用，以在迭代过程中发展，这是用于变化形态的化学计量数非晶氧化物结构的新模型，以及它们对电气应力的动态反应。这些模型将阐明有关电气更改的物理过程，我们将使用它们来生成一组材料和设备优化的设计规则。我们选择了一组代表性的材料进行研究，每种材料都在微电机中具有重要的应用。我们将在内部种植材料，使我们可以控制其组成和结构，并从表征和建模中快速反馈。我们的大部分表征也将在UCL上进行，但是我们与两个领先的传输电子显微镜中心（ForschungszentrumJülich）和新加坡的材料研究所和工程研究所进行了长期和富有成果的合作 - 这将使我们访问其他世界领先的显微镜技术来研究这些挑战材料。我们与包括工业合作伙伴在内的其他领先的研究和发展机构的密切合作使我们获得了进一步的最先进的设施和与工业相关的样本。