Sensitive optical probes for low pressure plasmas

该项目属于EPSRC等离子体和激光研究领域。它将利用腔衰荡光谱(CRDS)作为一种高分辨率的实验技术来研究低压等离子体中的痕量物种。低压等离子体在微纳电子学、半导体和催化方面具有很高的技术价值，并在医学和农业中有二次多学科的应用。在微纳电子和半导体行业中，对具有原子级精度和高材料选择性的蚀刻工艺的需求只有通过等离子体增强工艺才能实现。离子向表面的加速是高速化学气相沉积和精确蚀刻过程的关键。在这些技术应用中利用等离子体，可以获得原本无法达到的条件，并显著降低维持所需条件的能源成本，有助于提高环境的可持续性。对等离子体处理背后的基本原理的研究仍然有限，需要加强对离子能量和速度角分布的了解。特别是，《2022年等离子体路线图》突出了对中性和离子物种通量知识的缺乏，并强调了获得这一知识的重要性。因此，该项目将提供对等离子体特性和表面附近离子空间分布的更全面的了解，这将对这些技术领域的进步至关重要。在过去的一年里，这个项目的先前工作已经研究了氮等离子体的特性。特别是，建立了新的实验方法来量化等离子体中物种数密度的空间变化，包括在鞘和鞘前区域内。该项目将继续这项工作，优化这些方法，并包括对其他具有重要技术意义的加工气体，如Ar和氧气的调查。此外，还将通过在等离子室中应用新的射频波形和电极偏置来研究操纵等离子体鞘和预熔区的能力，这也将导致更好地控制撞击到关键表面的离子能量。获得的实验结果将与在工业合作伙伴LAM Research Inc.(美国)的帮助下在集团内建立的理论模型进行比较。LAM Research Inc.(美国)是半导体行业的全球专家，积极参与开发用于纳米级3D建筑的下一代制造工艺。LAM是世界领先的半导体铸造设备开发商，利用等离子体增强工艺的知识，包括化学气相沉积、原子层沉积和等离子体蚀刻，生产具有高性能的精密设备，能够实现行业内微型机电应用所需的高深宽比特征。这项研究与EPSRC作为数学和物理科学中的发现研究项目的战略一致。该项目的成果不仅将改变我们对低压等离子体，特别是流向表面的离子和自由基通量的理解，还将使等离子体增强过程得到优化。一旦在工业规模上实施优化，可以预期能源效率的大幅提高和成本的降低，这两者都有助于更绿色的未来，并支持行业内的经济增长。

This project falls within the EPSRC Plasma and Lasers research area. It will utilise cavity ringdown spectroscopy (CRDS) as a high-resolution experimental technique to investigate trace species within low pressure plasmas. Low pressure plasmas are of high technological interest for micro/nanoelectronics, semiconductors and catalysis, and have secondary multidisciplinary applications in medicine and agriculture. Within the micro/nanoelectronics and semiconductor industries, there is demand for etch processes with atomic level precision and high material selectivity, only possible with plasma enhanced processes. The acceleration of ions towards surfaces is key to high speed chemical vapour deposition and precise etching processes. Utilising plasmas in these technological applications allows otherwise inaccessible conditions to be acheived and significantly reduces the energy cost of maintaining the required conditions, contributing to improved environmental sustainability. Research on the fundamentals behind plasma processing is still limited and enhanced knowledge of ion energy and velocity angular distribution is needed. In particular, the 2022 Plasma Roadmap highlights the lack of knowledge of neutral and ionic species fluxes and emphasises the importance that this knowledge is gained. Therefore, the more complete understanding of plasma characteristics and ion spatial distributions near surfaces which this project will provide will be paramount to advancements within these fields of technology. Previous work on this project within the last year has investigated characteristics of nitrogen plasma. In particular, novel experimental methods were established to quantify the spatial variation of species number densities within the plasma, including within the sheath and pre-sheath regions. This project will continue this work, optimising these methods, and including investigations into other technologically important processing gases such as argon and oxygen. In addition, the ability to manipulate the sheath and presheath regions of the plasma will be investigated through the application of novel rf waveforms and electrode biasing in the plasma chamber, which will also lead to better control of the ion energies impinging on key surfaces. Experimental results obtained will be compared to theoretical models established within the group with the assistance of knowledge from industrial partners, Lam Research Inc. (US), who are global experts within the semiconductor industry and are heavily involved in developing the next generations of fabrication processes for 3D architecture on the nanometre scale. Lam are world leading semiconductor foundry equipment developers, using knowledge of plasma enhanced processes, including chemical vapour deposition, atomic layer deposition, and plasma etching, to produce precise, high performance equipment with the ability to achieve high-aspect ratio features required for micro-electromechanical applications within the industry. This research aligns with the EPSRC's strategies as a discovery research project within mathematical and physical sciences. The outcomes of this project not only will transform our understanding of low pressure plasmas, particularly ion and radical fluxes towards surfaces, but also enable the optimisation of plasma enhanced processes. Once optimisations are implemented on an industrial scale, substantial energy efficiency improvements and cost reductions could be expected, both contributing to a greener future and supporting economic growth within the industry.