JPS58141584A - Josephson junction element with conductive protective film - Google Patents

Abstract

PURPOSE:To realize connection between the Josephson junction element and another electrode without using a contact junction, and to improve the density of integration by coating an upper electrode with an intermetallic AuIn2 compound. CONSTITUTION:A lower electrode 1 consisting of an alloy of lead, indium and gold is oxidized and a tunnel barrier layer 3 is formed, the upper electrode 2 composed of lead or an alloy containing lead and the intermetallic AuIn2 compound 6 are laminated continuously, and the two layers are formed collectively through a soft-off method. The intermetallic AuIn2 compound 6 can be formed through the continuous evaporation of Au-In, the simultaneous evaporation of Au and In or the simultaneous sputtering of targets of Au and In or the like. The intermetallic AuIn2 compound 6 functions as the protective film by coating the upper electrode 2 because it has electrical conductivity and also has corrosion resistance while it is connected directly to another electrode 5 and can be connected electrically. The protective film consisting of the intermetallic AuIn2 compound 6 prevents intrusion of In from the electrode 5 to the upper electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a Noyosefson junction device with an electrically conductive protective film, which has a simple structure and is suitable for integrated circuits.

[Technical background of the invention and its problems]

Conventionally, in this type of element, a protective film was used to prevent the lead or lead-containing alloy of the upper electrode from being easily corroded.
Silicon Monokily f-do)? r-coated. S
Since iO is an insulator, it is not possible to connect directly between the upper electrode and other electrical conductors, and the electrical connection must be made through a Noyo1 Sefson junction element called a contact junction. Ta. (Reference R0F, Broom and
T”O, Mohr, J., Vac, Sci, Te.
chnol, 15.1166 (1978)) This drawback will be explained below with reference to FIG.

The figure is a schematic cross-sectional view of the lower electrode I and the upper electrode 2.
are connected to each other via a tunnel layer 3, and the upper electrode 2 is coated with a SiO retaining film 4 to a thickness of about 100 mm. The part A is a noyosefnon junction element. S40
Since the abscess 11!4 is an insulating film, it is impossible to directly connect the two-part electrode 2 and the other electrode 50 that is laminated after the formation of the protective film 4, as shown in the figure. Contact junction B2 through top to pole 2-tunnel clear 1-3
- I had no choice but to connect the lower part 'i4 to the pole I - the other v7L miscellaneous 5. One of the reasons why it was not possible to make such a connection is that the part 2 is easily corroded during the manufacturing process, so in order to prevent this, the insulating material S is used.
The other thing is to cover it with iO purulent membrane 4.
If the electrode 5 contains indium (In), if the electrode 5 and the upper electrode 2 are brought into direct contact, the In in the electrode 5 will spread into the upper electrode 4i@2 and destroy the tunnel barrier layer. This was to prevent the phenomenon. Therefore, as mentioned above, there is no choice but to use contact bonding, which has the disadvantage of occupying a large area.
It was 7.

[Purpose of writing]

In order to solve these drawbacks, the present invention uses AuIn2 intermetallic compound as an upper i! The electrode is coated to facilitate contact bonding, and the drawings will be described in detail below. , 2 is a dobe electrical connection, 3 is a tunnel barrier I, 5 is another electrode, 6 is an AuInz gold intermetallic compound as a protection electrode, and an example of one of the formation methods of the present invention is as follows. , a lower electrode made of an alloy of lead, indium, and gold is oxidized for 1 minute to form a tunnel barrier no. Compound 6 is continuously added to tm t-1, and the two layers are combined and collectively formed by a soft-off method.
] Intermetallic compound 6 is produced by continuous vapor deposition of Au-In, 8u, I
It can be formed by simultaneous vapor deposition of n, simultaneous sputtering of Au and In targets, etc.
The n2 intermetallic compound 6 has electrical conductivity of a normal conductor in the environment in which it is used (temperature 4.2 uK). It is also corrosion resistant, with a corrosion resistance of 7
By breaking the two upper electrodes made of lead or lead alloy, it acts as a single layer.In addition, it has conductivity (2), so it can be directly connected to the other electrodes 5. It can be connected and electrically connected.Also, AuIn
The protective layer consisting of the intermetallic compound 6 is isolated from the ML electrode by I
n is 4τ box.

It also makes a move to prevent it from entering Pole 2.

Therefore, there is no need for contact bonding, which was a cost in the past, and it is possible to save area and improve the stacking density If.

The above-mentioned effects are similar to Dobeden 4'dii 2,
Between the Au1n2 gold compound 6 and between the Au1n2 gold compound 6 and the other electrode 5, the 1'1 aluminum alloy S is thin enough that tunneling can occur between both.
However, the effects of the present invention will still be effective even if the

[My brother's effect was explained on the board]:') According to the present invention, the connection between the junction element and the +tl+ electrode can be fully realized with a small amount of effort, so it is possible to integrate it. It is possible to improve the density.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a conventional Noyosefson junction element, and FIG. 2 is a schematic Rr side view showing an embodiment of the present invention. ! . . . lower electrode, 2 . 5- Figure 1 Figure 2 j

Claims (1)

[Claims] A lower electrode made of an alloy of lead and gold, an upper electrode made of lead or a base metal containing lead, and a tunnel barrier layer interposed between them. A Josephson device with a conductive protective film, characterized in that an AuIn2 intermetallic compound is disposed in contact with an interface in contact with a tunnel barrier layer and an interface on the opposite side of ζ.