High yield method for contacting subsurface delta-doped phosphorus devices

Scanning tunneling microscopy enables the atom-scale fabrication of 2-D delta-doped structures in Si, with applications from high-performance computing to quantum information processing. However, device fabrication is extremely demanding with potential yield-limiting steps at each stage, and the efficient integration of these 2-D systems with 3-D contacts remains a challenge. Traditional device contact schemes involve back-filling etched vias with metal or leveraging the Kirkendall effect for Al spiking. Both result in irreproducibility associated with the erratic nature of Al spiking and the challenge of preserving clean interfaces during via etching and metallization. Here, we present a robust method for contacting delta-doped phosphorus devices that overcomes the shortcomings of the more common methods while also minimizing the thermal budget. We discuss this method in terms of yield and contact resistance, and as the latest addition to our complete process for fabricating, contacting, and testing STM patterned delta-doped devices.