JPS59182586A - Josephson junction element - Google Patents

Abstract

PURPOSE:To obtain the excellent characteristics of element with good reproducibility without necessitating a special technique for forming fine patterns by a method wherein the junction length, thickness, etc. of the junction part which requires micro dimensions are determined by the thicknesses of an insulation thin film and a conductive thin film. CONSTITUTION:The first and second electrodes 1 and 2 made of superconductive thin films processed into desired shapes are formed in a Josephson element, said electrodes 1 and 2 are arranged in the same plane, and a thin film 5 composed of an insulation layer of the thickness L is formed on the surface of the end surface of the electrode 1. The conductive thin film 6 is formed on the planes of the electrodes 1 and 2, and the thin film 5 is sandwiched between both surfaces opposed to each other of the electrodes 1 and 2. The thickness L of the thin film 5 corresponding to this junction length is selected approximately to the coherent length of the superconductive material of which the electrodes 1 and 2 are formed, and said material of the thickness (t) of approximate coherent length is used as the material of said film 6. Thus, excellent characteristics of element are realized with good reproducibility without necessitating the special technique for forming fine patterns.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a Josephson junction device, particularly a planar bridge type Josephson junction device.

Conventionally, as shown in FIG. 1, for example, as shown in FIG. A bridge portion 3 made of W is formed, and the bridge portion 3
In 2003, it was proposed that a joint part ≠ is formed in which a groove having a width L is formed, leaving the remaining part having a film thickness t, and the joint length is t, and the joint part is t. The joining element is the joining length and the joining part! It acts as a weakly coupled Josephson junction element by selecting an extremely small dimension called the coherent length of a superconducting thin film, but by applying special processing techniques such as electron beam exposure, 'e / It was necessary to accurately produce the actual dimensions of about 1000 nm. Moreover, variations in element characteristics are extremely sensitive to this dimensional accuracy, so in order to manufacture the cord with good reproducibility, it was necessary to precisely produce the dimensions of several 11 m or less. Does it require precision?
Even with the use of electronic green exposure technology, it is extremely difficult to achieve this level of precision, and it has been difficult to obtain cords with uniform characteristics.

The present invention improves the structure of the joint that simulates this ultra-fine dimension, and achieves excellent cable characteristics with reproducibility (a new technology for Josephson dust elements that can be sown) without relying on special fine pattern forming technology. It proposes a structure.

FIG. 2 shows an embodiment of the present invention, in which the Josephnon bonded thread according to the present invention has first and second t-pole wires made of a superconducting thin film processed into a desired shape, and the above-mentioned first It consists of a thin film j, 8 made of an a-layer with a thickness L formed on the end surface of the electrode, and a conductive thin film 6 with a thickness t, and the first and second electrodes /, 2 are placed on the same plane, 1st above
A thin film j made of the above insulating layer is sandwiched between a pair of opposing end faces of the second electrode C2, and the above insulating layer
A first layer comprising a thin film 5 consisting of layers? The above-mentioned 4-conductor thin film 6 is disposed on the upper surface of the 1st and 2nd electrodes 1 and 2, and the 1st and 2nd electrodes are formed by the above-mentioned 4-conductivity thin film 6 on the top of the thin film 5 made of the above-mentioned insulating layer. C2 is electrically connected to form a joint ≠.

In the above configuration, the thickness L of the thin film j made of the insulating layer corresponding to the bonding length is selected to be about the coherent a of the superconducting material forming the first and first electrodes 7.2, and If a superconducting material with a four-herrent length of 8 degrees and a thickness of 1 (corresponding to the joint) is used as the material, the first and second elongated poles will be weakly coupled in a superconducting manner, forming a so-called planar bridge. It acts as a weakly bound Josephson zygote of the form or s-s'-s form. Furthermore, even if a conductive material such as a normal conducting material or a semiconductor material is used as the material of the above-mentioned thin conductive film B, the first and second electrodes 2 and 2 are weakly superconducting (coupled, so-called 5-N-8
Needless to say, it acts as a weakly coupled Josephnon element. At this time, the thickness of the conductive material is not limited to the coherent length, and may be thicker.

Next, 1 of the method for producing Joseph non-bonded confectionery according to the present invention.
An example is illustrated in FIG. That is, a superconducting thin film 15 for forming the first electrode is laminated on the surface ml of the substrate /≠ to form a mask pattern /l for provisional shape processing of the first electrode (step (1)).

Next, using the mask pattern l/ as a mask, superconducting thin film/
The area not restored by the mask pattern // of j is removed to form a mask pattern l.
After removing 1, a lift-off stencil 12 made of a normal resist is applied to the end surface of the second electrode 1 and the second electrode, which is a thin strip of insulating layer, on the temporary electrode 10 and the substrate 1. A notch is formed so as to have a window for positioning the end (2) opposite to the surface facing the first electrode (step (2)).Next, the lift-off stencil 12 of the temporary electrode rO is used to After forming the Bt electrode 1 by removing the uncoated region, the sample is placed in an oxygen gas atmosphere, an oxygen plasma atmosphere, an anodizing medium, etc., and the end surface of the first electrode 1 that is not covered with the lift-off stencil 12 is removed. oxidation to form a thin film j made of an insulating layer at the end of the first electrode l (step (3)).

If we use the anodic oxidation method to form a single line of film made of this insulating layer, the oxidation rate is approximately 7/nm, so it is easy to create a thin film made of a single piece of wire with a narrow width. Since it can be controlled, it is possible to form a shape with high precision. Next, a superconducting thin film 13 to be applied as a second electrode is laminated by vertical vapor deposition (Step (4)) The lift-off stencil 12 is removed by an ordinary person, and the superconducting thin film 13 laminated on the lift-off stencil 12 is removed. is also removed to form a second electrode 2 whose -i plane is in contact with the end surface of the thin film j made of the insulating layer (rla (5J). This is a normal lift-off technique.

Thereafter, a conductive thin film (including a superconducting thin film T2V) is formed using a normal vacuum evaporation method, and then a torporically conductive thin film having a width that reaches part of the surfaces of the first and second electrodes is formed. Then, a Joseph non-junction element having the structure shown in FIG. 2 is obtained (step (6)). Here, the thickness of the isoelectric thin film can generally be controlled at a deposition rate of several iooλ/min even when laminated using a normal method, so it is not possible to control the thickness of a film of several nanometers. Colander.

As seen in the above manufacturing method, the ultrafine dimension portion of the Joseph non-junction element according to the present invention has a junction length of Depending on the thickness of the specialized thin film formed in step 6), the thickness is determined to be 8 or Φ, respectively.

Further, it goes without saying that the uninvented use of the Josephson fittings is not limited to the manufacturing method illustrated with reference to FIG.

As explained above, the uninvented Josephson Nukikai Seiko is that the amount of bonding and the amount of bonding of the bonding portion that simulates extremely small dimensions is the same as that of a thin film made of an insulating layer or a thin film made of an insulating layer. It is determined by the thickness, etc., and each of these 1" can be realized using broadcasting technology. For this reason, it is possible to significantly suppress the variation in the characteristics of individual pieces when producing a large number of pieces. It also has various effects such as greatly improving controllability of system properties and manufacturing reproducibility.

44. Brief description of the drawings Figure 1 shows the structure of a conventional Josennon spliced thread.
FIG. 2 is a purchasing diagram of the Joseph non-junction device according to the present invention.
FIG. 3 is a process diagram illustrating an example of a method for manufacturing a Joseph non-junction element according to the present invention.

l.../th electrode, 10... provisional electrode,! ...Second basket/parent, //...Mask pattern, 3...Bridge part, /2...Lift Metsu stencil, Hiro...
/3...Second superconductive thin film, j...Thin film made of loquat jψ, /≠...Substrate,
2 . . . 1. /j . . . superconductive thin film for the /th electrode.

designated agent ke/close OZ Sen Figure 3

Claims (2)

[Claims] (1) The force of the l-th and co-th electrodes made of a superconducting thin film is applied to a thin film made of an insulating layer having i in a dimension I of approximately the coherent size of the superconducting thin films constituting the first and second electrodes. The above-mentioned 7.
The entire width of the self-abrasive layer scratched by the conductive thin film on the surface of the thin film made of the first and second electrodes and the insulating layer, which are physically shaped, and at least the first and second scratches marked b1. A Josephson junction element, characterized in that it is formed in a shape that covers a part of the element, and has a structure in which the first and second electrodes are electrically connected to form a junction ball. (2) The scope of the patent claims that the conductive thin film is a superconducting thin film having a thickness approximately equal to the coherent length of the superconducting thin films constituting the first and second electrodes. The Josephson junction device according to item 1.