New Metallization Precursors for Microelectronic applications

微米和纳米制造是微电子、光伏和显示技术的基石，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学中使用的布线（即金属互连）特别重要，而且还作为电接触和光电子学。 随着微电子技术进一步小型化，ALD 变得越来越重要：它可以比包括 CVD 在内的其他制造技术更好地处理现代电子产品的长度尺度 (10 nm)。 ALD 沉积工艺在很大程度上依赖于挥发性含金属“前体”化合物的化学性质，以气相提供目标薄膜的成分。人们不断需要新型化学前体来满足 ALD 所需的挥发性和热稳定性。 自 1997 年以来，铜一直是微电子领域首选的互连金属，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器件，铜已经开始失效。在小互连尺寸下，铜金属很容易在电流通量中发生电迁移，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，在该框架中准确且可重复地测量这两个关键热参数（挥发和热分解），并建议使用它们来定义前驱体的“热范围”：在该温度范围内，前驱体具有足够高的蒸气压，可用于 ALD 工艺，而不会在蒸气前驱体的输送或气体表面界面发生热分解。 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；开发镍和钴前体作为铜的近期替代品作为互连材料；以及钨和钼前体的开发，作为未来互连技术的高温、高内聚金属。 这些前体将设计为具有单阴离子螯合配体（脒酸盐、胍盐、亚氨基吡咯烷酸盐、二酮亚胺盐）、单阴离子单齿配体（酰胺、烷基）和配位配体（膦、卡宾）。将使用其有效“热范围”对设计进行比较，并进行比较以研究设计中每个配体的有效性。 “挥发开始”和“热分解”温度的标准定义将用于对它们进行比较。迭代前体设计将用于开发和改进候选前体，最有希望的候选者将用于开发 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.