New Metallization Precursors for Microelectronic applications

作为微电子、光伏和显示技术的基石，微纳米制造在很大程度上依赖于化学气相沉积（CVD）和原子层沉积（ALD）的薄膜沉积。金属薄膜作为微电子中使用的布线（即金属互连）特别重要，但也作为电触点和光电子学。随着微电子技术的进一步小型化，ALD变得越来越重要：它可以处理现代电子器件的长度尺度（10纳米），比其他制造技术（包括CVD）要好得多。ALD的沉积过程在很大程度上依赖于挥发性、含金属的“前驱体”化合物的化学性质，以汽相形式传递目标膜的成分。不断需要新的化学前体来匹配ALD所需的挥发性和热稳定性。自1997年以来，铜一直是微电子互连金属的首选，但随着这种布线的横截面缩小，以容纳更小、更密集的晶体管和其他设备，铜已经开始失效。在较小的互连尺寸下，铜金属在电流通量下容易发生电迁移，导致导电性差，最终导致可靠性差。拟议的研究将探索一个框架，在这个框架中，精确地、可重复地测量这两个关键的热参数（挥发和热分解），并建议使用这些来定义前驱体的“热范围”：前驱体具有足够高的蒸汽压力，可以在ALD过程中使用，而不会在蒸汽前驱体的输送或在气体表面界面上热分解。提出了三个中期项目：开发用于传感和光谱学等光子应用的金和银薄膜前体；镍和钴前体的发展，作为铜作为互连材料的近期替代品；并开发了钨和钼的前驱体，作为高温、高凝聚力的金属，用于未来的互连技术。这些前体将由单阴离子、螯合配体（酰胺酸盐、胍酸盐、亚氨基吡啶酸盐、双酮酸盐）、单阴离子、单齿配体（酰胺、烷基）和配位配体（膦、羰基）设计。这些设计将使用它们的有效“热范围”进行比较，并比较研究设计中每个配体的有效性。将使用“挥发开始”和“热分解”温度的标准定义对它们进行比较。迭代前体设计将用于开发和改进候选前体，最有希望的候选前体将用于开发ALD工艺。

Micro- and nano-fabrication, the cornerstone of microelectronics, photovoltaics, and display technology relies greatly on the deposition of thin films using chemical vapour deposition (CVD) and atomic layer deposition (ALD). Metal thin films are particularly important as the wiring (i.e., metal interconnects) used in microelectronics, but also as electrical contacts and for optoelectronics. As microelectronics becomes further miniaturised, ALD has become increasingly important: it can handle the length scales (10 nm) of modern electronics much better than other fabrication techniques including CVD. Deposition processes by ALD rely heavily on the chemistry of volatile, metal-containing "precursor" compounds to deliver the components of the target film in the vapour phase. Novel chemical precursors are continually required to match the volatility and thermal stability required by ALD. Copper has been the interconnect metal of choice in microelectronics since 1997, but as the cross-section of this wiring has shrunk to accommodate smaller, more densely packed transistors and other devices, copper has started to fail. Copper metal will easily electromigrated in a current flux at small interconnect dimensions, causing poor conductivity and ultimately poor reliability. The proposed research will explore a framework in which to accurately and reproducibly measure these two key thermal parameters (volatilization and thermal decomposition) and proposes to use these to define the "thermal range" of a precursor: the temperature range over which the precursor has a high enough vapour pressure to be useful in ALD processes without thermally decomposing either in the delivery of the vapour precursor or at the gas-surface interface. Three medium-term projects are proposed: the development of precursors for gold and silver thin films for use in photonic applications like sensing and spectroscopy; the development of nickel and cobalt precursors as near-term replacements for copper as an interconnect material; and the development of precursors for tungsten and molybdenum, as high-temperature, high cohesion metals for future interconnect technology. These precursors will be designed with monoanionic, chelating ligands (amidinates, guanidinates, iminopyrrolidinates, diketiminates), monoanionic, monodentate ligands (amides, alkyls) and coordinative ligands (phosphines, carbenes). The designs will be compared using their effective "thermal range" and compared to investigate the effectiveness of each ligand in the design. Standard definitions of the temperatures for the "onset of volatility" and "thermal decomposition" will be used to compare them. Iterative precursor design will be used to develop and improve candidate precursors, and the most promising candidates will be used to develop ALD processes.