Double-masking technique for increasing fabrication yield in superconducting electronics

Abstract

An improved microfabrication technique for Josephson junctions in superconducting integrated circuits, based on the use of a double-layer lithographic mask for partial anodization of the side-walls and base electrode of the junctions. The top layer of the mask is a resist material, and the bottom layer is a dielectric material chosen so to maximize adhesion between the resist and the underlying superconducting layer, be etch-compatible with the underlying superconducting layer, and be insoluble in the resist and anodization processing chemistries. The superconductor is preferably niobium, under a silicon dioxide layer, with a conventional photoresist or electron-beam resist as the top layer. This combination results in a substantial increase in the fabrication yield of high-density superconducting integrated circuits, increase in junction uniformity and reduction in defect density. A dry etch more compatible with microlithography may be employed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a Continuation / Division of Ser. No. 11 / 616,382, filed Dec. 27, 2006, which is expressly incorporated herein by reference. This application is related to and claims priority to Provisional Application 60 / 826,262 filed Sep. 20, 2006 by inventor Sergey K. Tolpygo entitled A Double-Masking Technique for Increasing Fabrication Yield and Josephson Junction Quality in Superconducting Electronics, the contents of which are incorporated herein by reference in its entirety.STATEMENT OF GOVERNMENT RIGHTS[0002]This invention was developed in part under contract number N0014-03-C-0370 from the Office of Naval Research.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The invention is directed to fabrication of electronic devices and more particularly to the fabrication of superconducting electronic devices such as Josephson junctions.[0005]2. Description of the Prior Art[0006]Superconducting integrated circuits (ICs) ...

AI Technical Summary

Benefits of technology

This approach significantly increases the yield and quality of superconducting ICs by preventing defects during anodization and improving junction uniformity, enabling the reliable manufacturing of high-density, high-speed superconducting circuits.

Problems solved by technology

During this step, penetration of the anodization solution (the electrolyte) under the resist would cause major fabrication defects.

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