Study of superconducting Josephson junctions fabricated using a novel nanodamascene process for quantum computing and RSFQ application

2007年，舍布鲁克大学的一个研究小组报告了一种创新的隧道势垒制造方法，该方法可以更好地控制金属单电子晶体管（SET）的尺寸。这一突破性创新现在被半导体行业的路线图（ITRS 2007）所提及。拟议的研究计划将使用这种新的制造技术来实现纳米超导约瑟夫森结（JJ）。低温超导体JJ主要使用两种方法制造：阴影蒸发（例如基于Al的量子计算）;平面金属-势垒-金属（例如基于Nb的快速单通量量子电子学，RSFQ）。这种新技术将是约瑟夫森结制造方法在过去20年中的第一次重大变革。这种新技术预计会产生两个重要成果：铌中可以实现更小面积的结，从而在量子位设计（量子计算位）中提供更大的自由度来平衡充电和约瑟夫森能量; RSFQ大规模电路的更高工作频率（~ 500 GHz）和集成密度，如RSFQ路线图所预期的那样。此外，这种技术将允许隧道势垒工程，即使在超小面积的结，这是几乎不可能与传统的方法。该计划的第一阶段是探索与制造相关的材料问题以及由此产生的JJ的超导特性。铌将是一个候选者的选择，但其他材料将被考虑。第二阶段将实施屏障工程，并研究其对结特性的影响。第三阶段的目标是基于开发的技术制造小型超导电路。量子计算量子位设计和RSFQ的应用被认为是。该研究计划通过挑战传统的制造方法具有独特的创新潜力。所需的纳米制造环境已经可用，并得到了很好的支持。该计划也将大大受益于我在超导纳米结构方面的广泛专业知识，以及我在该领域的扩展本地和国际网络。

In 2007, a Université de Sherbrooke team reported an innovative new tunnel barrier fabrication method that allows greater dimensional control on metallic single electron transistor (SET). This breakthrough innovation is now referred to by the semiconductor industry's roadmap (ITRS 2007). The proposed research program will use this novel fabrication technique to realize nanoscale superconducting Josephson junctions (JJ). Low temperature superconductor JJs have been made using mainly 2 methods: shadow evaporation (e.g. Al based quantum computing); planar metal-barrier-metal (e.g. Nb based rapid single flux quanta electronics, RSFQ). This novel technique will be the first major change in Josephson junction fabrication methods in the last 2 decades. Two significant outcomes are expected from this new technique: smaller area junctions could be achieved in niobium thus giving a greater freedom to balance charging and josephson energy in qubit designs (quantum computing bit); higher operation frequency (~500GHz) and integration density for RSFQ large scale circuits as expected by the RSFQ roadmap. Furthermore, this technique will allow tunnel barrier engineering even at ultra small area junctions, which is hardly possible with the conventional methods. The 1st phase of the program is to explore material issues related to fabrication and to superconducting properties of the resulting JJs. Niobium will be a candidate of choice but other materials will be considered. The 2nd phase will be to implement barrier engineering and study its effect on junction properties. The 3rd phase will aim at fabrication small scale superconducting circuits based on the developed technology. Applications to quantum computing qubit designs and RSFQ are considered. This research program has a unique potential for innovation by challenging the conventional fabrication methods. The required nanofabrication environment is already available and well supported. The program will also greatly benefit from my extensive expertise in superconducting nanostructures and from my extended local and international network in the field.