JP3167454B2 - Superconducting element and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting element used for an electromagnetic wave sensor, a bolometer, and the like, and a method for manufacturing the same.

[0002]

BACKGROUND ART electromagnetic wave sensor, a sensor for particularly detecting electromagnetic waves of very high frequency band of several TH _Z tens GH _Z, one using a superconductor has attracted attention because they exhibit a very high sensitivity and low noise . In particular, rare earth oxide superconductors such as YBa ₂ Cu ₃ O _7-X (hereinafter abbreviated as YBCO) discovered several years ago are in a superconducting state at a relatively high temperature of about 77 K indicated by inexpensive liquid nitrogen. So
It is expected to have a wide range of applications.

[0003] A superconducting element using this superconductor is disclosed, for example, in Japanese Patent Application Laid-Open No. 3-79091 (H01L 3/18).

[0004]

Meanwhile [0008] As the electromagnetic wave sensor for generally detecting electromagnetic waves of very high frequency band of several TH _Z tens GH _Z, a good detection sensitivity the higher normal conductive resistance between the element terminals However, in a superconducting element using a grain boundary Josephson junction or a superconducting element in which a Josephson junction is formed using a step edge of a substrate as shown in the above publication, the resistance value of the element is low, and as an electromagnetic wave sensor, We couldn't expect very high sensitivity. Also,
Even in a bolometer composed of a superconducting element, if the element has a low normal conduction resistance, there is a problem that the detection sensitivity of infrared rays is reduced.

In superconducting elements such as an electromagnetic wave sensor and a bolometer, the sensitivity of the element is reduced by an excessive superconducting current, but it is difficult to control the superconducting current in the above-described superconducting element.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a superconducting element having a high normal conduction resistance and capable of controlling superconducting current, and a method of manufacturing the same. I do.

[0007]

The superconducting element of the present invention comprises:
An insulating substrate and an oxide superconductor thin film formed on the substrate are used as main components, and the oxide superconductor thin film is sandwiched between the electrode forming portions located on both sides and the electrode forming portions. And a sensor unit, wherein the sensor unit is divided into a lattice by a high-resistance member.

In particular, the oxide superconductor is a rare earth oxide superconductor LnBa ₂ Cu ₃ O _7-X (Ln is Y, Eu, G
d, Tb, Dy, Ho, Er, Tm or Yb), and the high-resistance member is made of BaBiO _{3 and} Ba ₂ LnBiO ₆ .

Further, the method for manufacturing a superconducting element of the present invention is characterized in that a rare earth oxide superconductor LnBa ₂ Cu ₃ O _7-X (Ln is Y, Y) having a sensor portion and electrode formation portions on both sides thereof on an insulating substrate. Eu, Gd, Tb, Dy, Ho, Er, Tm or Y
b) a step of forming a thin film, a step of forming a plurality of grooves in a lattice shape in a sensor portion of the rare earth oxide superconductor thin film, and a step of forming Bi in the grooves.
Forming a ₂ O _3, and wherein the step of creating a high-resistance member is reacted by the Bi ₂ O ₃ and heat treated with the rare earth-based oxide superconductor exposed in the groove, in that it consists of I do.

[0010]

According to the structure of the present invention, since the sensor portion made of the oxide superconductor thin film is divided into a lattice by the high resistance member, the superconductor is made of a high resistance member (normal conductor).
Since the Josephson junction having a high normal conduction resistance is provided in the form of a lattice, the normal conduction resistance of the element can be increased, and the superconducting current value can be controlled by the type of the high resistance member, the groove pitch, and the like. Is possible.

In particular, when the oxide superconductor is a rare earth oxide superconductor LnBa ₂ Cu ₃ O _7-X and the high resistance member is made of BaBiO _{3 and} Ba ₂ LnBiO ₆ , a more sufficient element Normal conduction resistance is obtained.

According to the manufacturing method of the present invention, the Bi ₂ O ₃ formed in the groove formed in the rare earth oxide superconductor thin film is formed.
And the rare earth-based oxide superconductor exposed in the groove is reacted by heat treatment to produce a high-resistance member. By this reaction, the superconductor and the high-resistance member are sufficiently bonded to each other, and Joseph having a large normal conduction resistance is used. A son junction can be formed, and the superconducting current value can be controlled by the heat treatment conditions.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of an electromagnetic wave sensor using the superconducting element of the present invention, and FIG. 2 is an enlarged perspective view of a sensor portion of the electromagnetic wave sensor described below.

Reference numeral 1 denotes an insulating substrate of MgO single crystal or SrTiO ₃ single crystal or the like, and 2 denotes a rare-earth oxide superconducting thin film formed on the surface of the substrate 1, for example, a thin film obtained by epitaxially growing a YBCO-based oxide superconducting material. It is configured. The superconducting thin film 2 has a width of 30 μm and a length of 10 μm which functions as an electromagnetic wave sensor by reducing the width of the central portion.
A sensor section 3a having a size of about 0 μm and a thickness of about 0.3 μm is provided with a wider electrode forming section 3 on both sides thereof.
Output electrodes (inside) 4a, 4a and electrodes (outside) 4b, 4b made of Au or the like having a thickness of about 0.1 to 1 [mu] m are respectively formed in b and 3b.

The sensor section 3a has concave grooves 5, 5,... Having a width W of 0.3 μm and a depth H of 0.3 μm for dividing the superconducting thin film 2 of the sensor section 3a, as shown in FIG.
However, the pitch Pa in the longitudinal direction of the sensor portion 3a is 10
The substrate 1 is formed in a lattice shape such that the substrate 1 is exposed at intervals of about μm and a pitch Pb in the width direction of about 10 μm.
In the grooves 5, 5..., A high-resistance material BaBiO _{3 and a} high-resistance material Ba ₂ YBiO for increasing the normal conduction resistance between element terminals and controlling the superconducting current of the sensor section 3a.
_A high resistance member 6 composed of 6 is embedded.

Next, a method for manufacturing such an electromagnetic wave sensor will be described in detail.

First, as shown in FIG.
An insulating substrate 1 made of MgO single crystal having dimensions of about 6 mm × about 1 mm in thickness is prepared. Next, on the upper surface of the insulating substrate 1 which is a (100) crystal plane, a sensor portion 3a having a narrow central portion by a sputtering method or a CVD method or the like via a metal mask and electrode forming portions on both sides thereof. 3
A superconducting thin film 2 made of YBCO having a thickness of about 0.3 μm and having b and 3b is epitaxially grown. Here, the deposition of superconducting thin film 2 of the present embodiment, by rf magnetron sputtering using a target made of YBa ₂ Cu ₄ O _y, for example, a mixed gas atmosphere of Ar gas and O ₂ gas,
The total gas pressure is 4 Pa (flow ratio Ar gas: O ₂ gas =
1: 1), the substrate temperature was 650 ° C., and the film formation rate was 40 ° / min.

Subsequently, as shown in FIG. 3B, the sensor unit 3 is scanned while being irradiated with a focused ion beam, and is scanned to have a width W of 0.3 μm, a depth H of 0.3 μm, and a pitch Pa, Pb.
(See FIG. 2) each have a groove 5, 5.
To form Next, Bi ₂ by via the grooves 5, 5 comb metal mask corresponding to the shape of the (not shown), a sputtering method, an evaporation method, or the like vertically and horizontally the respective grooves 5,5 in.. O ₃ is filled and formed. Here, Bi of the present embodiment
₂ O ₃ was formed by an ion beam sputtering method using a target made of bismuth oxide, for example, at an Ar gas pressure of 1 Pa, a substrate temperature of room temperature, and a film formation rate of 80 ° / min.

Thereafter, the temperature of the superconducting thin film 2 is raised from room temperature to 870 ° C. for about 3 hours in an oxygen atmosphere, maintained at this temperature for about 3 to 5 hours, and then gradually cooled to room temperature at about 100 ° C./hour. I do. By the heat treatment, Bi ₂ O ₃ formed in the grooves 5, 5,... And Y exposed in the grooves 5, 5,.
BCO reacts and both are cubic crystals of a simple perovskite structure, BaBiO ₃ (specific resistance is 10 ⁴ Ω · cm or more) and B
A high-resistance member 6 mainly composed of a ₂ YBiO ₆ (specific resistance is 10 ⁴ Ω · cm or more) is formed in the grooves 5. Here, the holding temperature is set to the YBCO of the superconducting thin film 2.
BaBiO ₃ by reaction of Bi ₂ O ₃ in the groove 5, 5 and
And the temperature at which Ba ₂ YBiO ₆ starts to form (650 ° C.)
At a higher temperature at which the superconductivity of YBCO is lost (100
0 ° C.), and the heat treatment is desirably performed at a temperature of 900 ° C. or less as described above, in which the superconducting thin film does not peel off and the superconducting thin film does not partially melt.

In the above description, (10) of the MgO insulating substrate 1
Although the superconducting thin film 2 is formed on the (0) plane, another insulating substrate may be used as appropriate. For example, the superconducting thin film 2 may be formed on the (110) plane of a SrTiO ₃ insulating substrate.

Such an electromagnetic wave sensor has a
BaBiO with superconducting thin film 2 of high resistance _ThreeAnd Ba_TwoYBi
O₆Is divided into a lattice by the high resistance member 6 whose main component is
So many superconductors and normal conductors are in contact with each other.
Having a network-like Josephson junction
Shows the characteristics of a Sefson element and an electromagnetic wave sensor element
Had a normal conduction resistance Rn of about 20Ω. As a result,
Child sensitivity R_VShows good characteristics of about 1000 V / W
Was.

This electromagnetic wave sensor has a lattice-shaped groove 5,
By controlling the number, size, or holding temperature when producing the high-resistance member 6 of 5..., The superconducting current value can be controlled to a small superconducting current value on the order of μA. did it.

In the embodiment, YBa is used as the superconducting thin film._Two
Cu_ThreeO_7-XWas used, but YBa_TwoCu _ThreeO_7-XLimited to
, LnBa in which Y is replaced by another rare earth element_TwoCu_ThreeO
_7-X(Ln is Y, Eu, Gd, Tb, Dy, Ho, E
at least one element selected from r, Tm and Yb
Element) rare earth element oxide superconductor
Can also be formed in the grooves 5, 5,.
Bi_TwoO_ThreeBy heat treatment_TwoCu_ThreeO_7-XWhen
BaBiO which reacts and has high resistance_ThreeAnd Ba_TwoLnBiO
₆Are formed in the grooves 5, 5...
It is possible.

In the above description, the grooves 5, 5... Are formed so that the insulating substrate 1 is exposed.
May be divided so that the superconducting thin film 2 having a thickness of about 0.1 μm or less remains at the bottom.

Further, Bi ₂ O ₃ is filled and formed in the grooves 5, 5... To form a high-resistance member by heat treatment. Instead of Bi ₂ O ₃ , PbO, Sb ₂ O ₃ , B ₂ O ₃ , Mo
O ₃ , PtO ₂ , Na ₂ O ₂ etc. could be used as well.

The present invention is not limited to the above electromagnetic wave sensor,
It can also be used for a superconducting element such as a bolometer and can increase the normal conduction resistance of the element, so that a highly sensitive superconducting element can be obtained.

[0027]

According to the superconducting element of the present invention, since the sensor portion made of the oxide superconducting thin film is divided into a lattice by the high-resistance member, the superconductor forms the high-resistance member (normal conductor). Since the Josephson junction having a high normal conduction resistance is provided in a lattice shape, the normal conduction resistance of the element is increased, and the superconducting current value can be controlled by the type of the high resistance member, the groove pitch, and the like. . As a result, by using this device, several tens GH _Z T
The highly sensitive electromagnetic sensor or an infrared detecting an electromagnetic wave of very high frequency band of H _Z it is possible to realize a bolometer which can be detected with high sensitivity.

According to the manufacturing method of the present invention, Bi ₂ O ₃ formed in a lattice-shaped groove formed in the sensor portion of the rare-earth oxide superconductor LnBa ₂ Cu ₃ O _7-X thin film and the groove are formed. Since the high-resistance member is created by reacting the rare-earth-based oxide superconductor exposed inside by heat treatment, the reaction sufficiently joins the superconductor and the high-resistance member, and a Josephson junction having a large normal conduction resistance is formed. The superconducting current value can be controlled by the heat treatment conditions.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a superconducting element according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a sensor part of the superconducting element of the embodiment.

FIG. 3 is a manufacturing process diagram of the superconducting element of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Rare-earth oxide superconducting thin film 3a Sensor part 3b Electrode formation part 5 Groove 6 High resistance member

Continuation of front page (56) References JP-A-60-130182 (JP, A) JP-A-1-138770 (JP, A) JP-A-2-260472 (JP, A) JP-A 1-260868 (JP) , A) JP-A-3-4574 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 38/22-39/24 H01L 39/00

Claims (3)

(57) [Claims] An insulative substrate and an oxide superconductor thin film formed on the substrate are main components, and the oxide superconductor thin film has electrode forming portions located on both side portions; And a sensor part sandwiched between the parts, wherein the sensor part is divided into a lattice by a high-resistance member. 2. The oxide superconductor is a rare earth oxide superconductor LnBa ₂ Cu ₃ O _7-X (Ln is Y, Eu, Gd,
2. The high-resistance member is made of BaBiO _{3 and} Ba ₂ LnBiO ₆ , at least one element selected from the group consisting of Tb, Dy, Ho, Er, Tm, and Yb. Superconducting element. 3. A rare earth oxide superconductor LnBa ₂ having a sensor portion and electrode formation portions on both sides thereof on an insulating substrate.
Cu ₃ O _7-X (Ln is Y, Eu, Gd, Tb, Dy, H
at least one element selected from the group consisting of o, Er, Tm, and Yb); and forming a plurality of grooves in a lattice pattern in a sensor portion of the rare-earth oxide superconductor thin film; Forming Bi ₂ O ₃ in the groove;
Reacting ₂ O ₃ and the rare earth oxide superconductor exposed in the groove by heat treatment to form a high resistance member;
A method for manufacturing a superconducting element, comprising: