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Single-charge Circuits

Working Group 2.42

Fabrication of metallic sub-µm devices

Methods of Planarization

1.) Niobium trilayer technique with "Spin-on-Glass" planarization

This technique uses large area Nb/AlOx/Nb-trilayers. Small patterns are created by etching processes and subsequently planarized.





SEM-micrograph of a Nb/AlOx/Nb-transistor in SOG-technique



2.) Niobium trilayer technique with "CMP" planarization

This technique uses SiO2 to replace the "Spin-on-Glass". The circuit is planarized by chemical-mechanical polishing (CMP).

SEM-micrograph of a Nb/AlOx/Nb-transistor in CMP-technique



Literature:

A. B. Pavolotsky, T. Weimann, H. Scherer, J. Niemeyer, and A. B. Zorin, "Novel Method for Fabricating Deep Submicron Nb/AlOx/Nb Tunnel Junctions Based on Spin-on Glass Planarization", IEEE Trans. Appl. Supercond. 9 (2), 3251 (1999).

R. Dolata, H. Scherer, A. B. Zorin and J. Niemeyer, "Single-charge devices with ultrasmall Nb/AlOx/Nb trilayer Josephson junctions", J. Appl. Phys. 97, 054501 (2005).