Hot Wire Chemical Vapor Deposition Chemistry in the Gas Phase and on Surfaces

拟议的研究重点是气相反应化学和动力学参与碳化硅和氮化物薄膜的生长使用热线化学气相沉积（HWCVD），并涉及表征自由基中间体的结构和能量特性，并了解发生在金属丝和衬底表面的化学过程。HWCVD已被广泛用于制备Si基薄膜、金刚石涂层、纳米颗粒和有机聚合物涂层。碳化硅是蓝色发光二极管（LED）和太阳能电池中宽带隙窗口材料的优秀候选者，而氮化硅可用作薄膜晶体管中的钝化层、太阳能电池中的减反射涂层和扩散阻挡层。在拟议的研究中，激光电离质谱，配备了免费的“软”单光子真空紫外激光电离和高效的激光诱导电子电离方法，将被用作一个强大的诊断工具，用于检测气相化学物种。这些方法，支持同位素标记，化学捕获和从头计算，将有助于解开复杂的反应化学在气相中，是负责气相薄膜生长前体的形成。利用共振增强多光子电离（REMPI）光谱技术结合高压脉冲放电和脉冲激光烧蚀技术，将研究重要自由基物种的结构和能量特性。这些研究将为难以分离的自由基物种开发高灵敏度和选择性的检测方法。我们的表面化学研究将集中在金属合金的热灯丝和硅基薄膜的生产上的衬底。金属丝在HWCVD中是必不可少的，因为它们用作催化剂来分解源气体以形成引发气相反应化学的反应性物质。金属丝暴露于气相反应性物质导致金属硅化物和碳化物的形成。这些合成合金导致灯丝老化并影响沉积膜的性能。我们将系统地研究暴露于对碳化硅和氮化物膜生长重要的各种有机硅源气体后金属线上硅化物和碳化物的形成。这将有助于解决灯丝老化的问题，并允许控制沉积过程。最后，在各种生长条件下产生的最终Si基薄膜材料的结构和光学性质的表征将与来自气相反应化学和细丝合金化的科学发现相关。总体而言，拟议的研究将推进我们目前对HWCVD化学的理解，并有助于合理改进HWCVD工艺，从而为工业应用提供优质薄膜。这将极大地有利于加拿大的半导体、替代能源和微电子工业领域。

The proposed research focuses on the gas-phase reaction chemistry and kinetics involved in the growth of silicon carbide and nitride thin films using hot wire chemical vapor deposition (HWCVD), and involves characterizing the structural and energetic properties of radical intermediates, and understanding the chemical processes taking place on the metal wire and substrate surfaces. HWCVD has been widely used to produce Si-based thin films, diamond coatings, nanoparticles and organic polymer coatings. Silicon carbides are excellent candidates for blue light-emitting diodes (LEDs) and wide bandgap window materials in solar cells, while silicon nitrides can be used as passivation layers in thin film transistors, anti-reflection coatings and diffusion barriers in solar cells. In the proposed research, laser ionization mass spectrometry, equipped with complimentary "soft" single photon vacuum UV laser ionization and efficient laser-induced electron ionization methods, will be used as a powerful diagnostic tool for the detection of gas-phase chemical species. These approaches, supported by isotope labeling, chemical trapping and ab initio calculations, will help unravel the complex reaction chemistry in the gas phase that is responsible for the formation of gas-phase thin film growth precursors. The structures and energetic properties of important radical species will be investigated using resonance enhanced multiphoton ionization (REMPI) spectroscopy combined with the techniques of high-voltage pulsed electric discharge and pulsed laser ablation. Highly sensitive and selective detection methods for the hard-to-isolate radical species will be developed from these studies. Our studies of the surface chemistry in HWCVD will be centered on metal alloy formation on the hot filament and Si-based thin film production on the substrate. Metal filaments are essential in HWCVD as they serve as catalysts to decompose source gases to form reactive species which initiates the gas-phase reaction chemistry. Exposure of metal filaments to the gas-phase reactive species leads to the formation of metal silicides and carbides. These resultant alloys cause the filament to age and affects the deposited film properties. We will systematically study the silicide and carbide formation on the metal wire upon exposure to various organosilicon source gases important for silicon carbide and nitride film growth. This will help solve the problem of filament aging and allow the deposition process to be controlled. Finally, characterization of the structural and optical properties of the ultimate Si-based thin film materials produced under various growth conditions will be correlated to the scientific findings from the gas-phase reaction chemistry and filament alloying. Overall, the proposed research will advance our current understanding of HWCVD chemistry and contribute to a rational improvement of the HWCVD process that will lead to superior-quality thin films for industrial applications. It will benefit greatly the industrial areas of semiconductors, alternative energy sources and microelectronics in Canada.