Browse Prior Art Database

CONDUCTING OXIDE PASSIVATION OF HIGH Tc SUPERCONDUCTING OXIDE FILMS

IP.com Disclosure Number: IPCOM000036944D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Krusin-Elbaum, L: AUTHOR

Abstract

The discovery of superconductivity above liquid nitrogen temperatures may become of extreme importance in the wiring in VLSI circuits, as well as in the semiconducting and in superconducting devices. 77K operation of Si-based FETs is inevitable for fine line dimensions below 0.5 mm, and CMOS process for liquid nitrogen operation has been tested already. The lowering of the temperature is important in significantly reducing RC losses in the interconnects when they are patterned out of normal metal. If the interconnect metal undergoes a resistive transition into a superconducting state above 77K, the delays due to the resistive voltage drop in the transmission lines would be zero.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 51% of the total text.

Page 1 of 3

CONDUCTING OXIDE PASSIVATION OF HIGH Tc SUPERCONDUCTING OXIDE FILMS

The discovery of superconductivity above liquid nitrogen temperatures may become of extreme importance in the wiring in VLSI circuits, as well as in the semiconducting and in superconducting devices. 77K operation of Si-based FETs is inevitable for fine line dimensions below 0.5 mm, and CMOS process for liquid nitrogen operation has been tested already. The lowering of the temperature is important in significantly reducing RC losses in the interconnects when they are patterned out of normal metal. If the interconnect metal undergoes a resistive transition into a superconducting state above 77K, the delays due to the resistive voltage drop in the transmission lines would be zero.

The most studied high Tc superconductor so far is the Y-Ba-Cu-O system. Transition temperatures as high as 98K were reported for this material, with the transition widths of only a few degrees. This Tc can be maintained if yttrium is replaced by a variety of rare earths, such as europium, gadolinium, neodymium, etc. The materials with sharp resistive transitions are mostly prepared as ceramics. Recently, however, films of Y1Ba2Cu3O9-x (1-2-3 compound) were prepared by triple gun evaporation and by sputtering from a single hot pressed target. Good quality films are, of course, essential for VLSI applications.

At the present time, one of the most severe problems in the preparation of good quality films is the fact that they lose oxygen when exposed to air at room temperature after a high temperature (900oC) anneal in oxygen. The amount of loss depends on the warm-down time and the ambient in which it takes place. Nevertheless, the loss is always there, and it is in part responsible for the decreased value of superconducting transition temperature. Moreover, it is observed that a thin insulating overlayer is formed, which is likely due to the surface depletion of oxygen. This layer makes the electrical contact to the film very difficult. Clearly, a scheme to lock the oxygen in high Tc films would be extremely valuable.

In this disclosure, we propose to deposit thin films of oxides of platinum group metals, which possess tetragonal rutile structure, such as dioxides of Ru, Ir, or Rh. These materials are all conducting with resistivities that can be as low as 30 mL-cm at room temperature and a factor of two lower at 77K. We have shown these conducting oxides to be extremely effective as diffusion barriers, withstanding temperatures higher than the thermal limit of such well-known barriers as transition metal nitrides (e.g., ZrN or TiN). They are also extremely stable in air as well as in the oxygen environment. Indeed, their resistivity decreases after oxygen anneal. Most importantly, they do not lose oxygen. A thin layer of such conducting binary oxide should prevent escape of oxygen from the superconducting underlayer. Any diffusion of oxygen from the high Tc film into a binary oxide will be...