JP2005252019A - Superconductive element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductive element low in conductivity and high in electric insulating property while having an interlayer insulating layer, low in dielectric constant and low in dielectric loss. <P>SOLUTION: The superconductive element is formed of a Y<SB>0.9</SB>Ba<SB>1.9</SB>La<SB>0.2</SB>Cu<SB>3</SB>O<SB>y</SB>layer 2, an MgO insulator layer 3 and the Y<SB>0.9</SB>Ba<SB>1.9</SB>La<SB>0.2</SB>Cu<SB>3</SB>O<SB>y</SB>layer 4, which are laminated sequentially on an MgO single crystal substrate 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a superconducting element, and in particular, an oxide superconductor that enables high-speed operation of the electronic device or the like and can significantly reduce power consumption of the electronic device or the like when mounted on the electronic device or the like. The present invention relates to a superconducting element.

Since the superconductor has a feature such as a Josephson effect in which the electric resistance disappears below the critical temperature, it is considered that an electronic device using the superconductor can operate at high speed with low power consumption. Among them, oxide superconductors are considered promising as practical materials because they have a high critical temperature of 80K or higher.Currently, YBa ₂ Cu ₃ O _y , Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y, etc. Research on electronic devices using representative oxide superconductors has been actively conducted.

  In conducting research on electronic devices using the above oxide superconductors, many of the superconductor devices such as single flux quantum (SFQ) devices are composed of multi-layer superconductor wiring structures. Therefore, research on interlayer insulation layers for the purpose of electrical insulation between upper and lower superconductor film layers of oxide superconductors has been actively conducted, for example, research on interlayer insulation films with high insulation properties, oxide superconductors, etc. Research on forming an interlayer insulating film with high crystallinity and surface flatness on the layer, or research on an interlayer insulating film capable of forming an oxide superconductor layer with high crystallinity and flatness on the surface, etc. Has been done.

To date, SrSnO ₃ and CaSnO ₃ (Katsuno et al., Proc. Of the 49th Applied Physics Related Conference 28a-ZD-2) , SrTiO ₃ and CeO ₂ (Soutome et al., IEICE TRANS. ELECTRON. Vol. E85-C, No3 March 2002), Sr ₂ AlTaO ₆ (Takahashi et al., IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, Vol. 11, No.1 March 2001), (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O 3) _0.7 and SrTiO ₃ laminated structure (Wakana et al., ASC 2002), etc. are being researched and developed.

However, the insulation structure of SrSnO ₃ , CaSnO ₃ , SrTiO ₃ and CeO ₂ shown above, Sr ₂ AlTaO ₆ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 and SrTiO ₃ While the film has low electrical conductivity and high electrical insulation, the film has a dielectric constant of about 17 to 30, so the capacitance component of the insulating film increases, which increases the dielectric loss and power consumption. There is a problem of inviting an increase in In addition, since the conventional insulating film has a dielectric constant of about 17 to 30, a high-frequency signal cannot be input, and the waveform of the high-frequency signal is disturbed due to an increase in delay time. There is a problem that circuit design becomes more difficult.
Proceedings of the 49th Joint Conference on Applied Physics 28a-ZD-2

  SUMMARY OF THE INVENTION An object of the present invention is to provide a superconducting element having an insulating layer with low conductivity and high electrical insulation, low dielectric constant and low dielectric loss.

  In order to solve the above problems, a superconducting element of the present invention includes a first oxide superconductor layer, an insulating layer made of MgO and formed on the first oxide superconductor layer. And a second oxide superconductor layer formed on the layer.

  According to the above invention, since the insulating layer made of MgO is formed on the first oxide superconductor layer, the electrical conductivity can be lowered and the electrical insulation can be enhanced. Therefore, it is possible to insulate between the first oxide superconductor layer and the second oxide superconductor layer.

  Further, according to the invention, since the insulating layer made of MgO is formed on the first oxide superconductor layer, the dielectric constant is changed from the conventional 17 to 30 to about 10 (MgO is bulky). Having a dielectric constant of about 10). Therefore, the capacitance of the capacitance component formed between the oxide superconductor layers can be made much smaller than before, so that the dielectric loss can be reduced and the disturbance of the waveform of the high-frequency signal can be prevented. And a circuit can be easily designed.

  In one embodiment, the superconducting element includes a first insulating thin film layer between the first oxide superconductor layer and the insulating layer.

  According to the above embodiment, since the first insulating thin film layer is provided between the first oxide superconductor layer and the insulating layer made of MgO, the first oxide superconductor layer and the above Undesirable reactions that may occur with the insulating layer can be prevented.

  Further, the superconducting element of one embodiment is characterized in that the first insulating thin film layer is composed of a plurality of layers.

  According to the embodiment, since the first insulating thin film layer is composed of a plurality of layers, the first insulating thin film layer is composed of one layer by appropriately selecting the plurality of layers. As compared with the case where the first insulating thin film layer is formed, the distortion of the first insulating thin film layer can be reduced. Therefore, since the crystallinity and surface flatness of the first insulating thin film layer can be increased, the crystallinity of the insulating layer formed on the first insulating thin film layer can be made excellent. .

  In one embodiment, the superconducting element includes a second insulating thin film layer between the insulating layer and the second oxide superconductor layer.

  According to the embodiment, since the second insulating thin film layer is provided between the insulating layer made of MgO and the second oxide superconductor layer, the insulating layer and the second oxide superconducting layer are provided. Undesirable reactions that may occur with the body layer can be prevented.

  The superconducting element of one embodiment is characterized in that the second insulating thin film layer is composed of a plurality of layers.

  According to the embodiment, since the second insulating thin film layer is composed of a plurality of layers, the second insulating thin film layer is configured as a single layer by appropriately selecting the plurality of layers. Compared to when the second insulating thin film layer is strained, the strain can be reduced. Therefore, since the crystallinity and surface flatness of the second insulating thin film layer can be increased, the crystallinity of the second oxide superconductor layer formed on the second insulating thin film layer is excellent. Can be a thing.

In one embodiment, the first insulating thin film layer has BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO _3. Or at least two of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO ₃ It is characterized by comprising.

According to the embodiment, the first insulating thin film layer is formed of BaZrO ₃ , SrHfO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrMoO ₃ and BaSnO ₃ . Since it is composed of any one or two or more, the element between the first insulating thin film layer, the MgO insulating layer, and the first (second) oxide superconductor layer Can prevent mutual diffusion. Therefore, it is possible to reliably prevent the insulating layer from causing an undesirable reaction when it comes into contact with the first oxide superconductor layer.

In one embodiment, the second insulating thin film layer includes BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO _3. Or at least two of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO ₃ It is characterized by comprising.

According to the embodiment, the second insulating thin film layer is formed of BaZrO ₃ , SrHfO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrMoO ₃ and BaSnO ₃ . The element between the second insulating thin film layer, the MgO insulating layer, and the first (second) oxide superconductor layer because it is composed of any one or two or more. Can prevent mutual diffusion. Therefore, it is possible to reliably prevent the insulating layer from causing an undesirable reaction when it comes into contact with the second oxide superconductor layer.

  In one embodiment, the superconducting element is characterized in that the insulating layer has a thickness of 30 nm or more.

  According to the embodiment, since the thickness of the insulator layer is 30 nm or more, sufficient insulation can be ensured.

  In one embodiment, the superconducting element is characterized in that the insulating layer has a thickness of 600 nm or less.

  According to the embodiment, since the thickness of the insulator layer is 600 nm or less, deterioration of the flatness of the surface of the insulator layer can be avoided.

  According to the superconducting element of the present invention, since the insulating layer made of MgO is formed on the first oxide superconductor layer, the electrical conductivity can be lowered, that is, the electrical insulation can be increased, and the first It is possible to insulate between the first oxide superconductor layer and the second oxide superconductor layer without any problem.

  According to the invention, since the insulating layer made of MgO is formed on the first oxide superconductor layer, the capacitance of the capacitance component formed between the oxide superconductor layers is It can be made much smaller than before, and the dielectric loss can be reduced. In addition, since an insulating layer made of MgO is used, the disturbance of the waveform of the high frequency signal can be prevented, and the circuit can be designed easily.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing the layer structure of the superconducting element of the first embodiment.

In the superconducting element of the first embodiment, on the MgO single crystal substrate 1 as an example of the substrate, the first Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 as an example of the first oxide superconductor layer 2 Then, an MgO insulator layer 3 made of MgO, and a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as an example of the second oxide superconductor layer are sequentially laminated.

  Hereinafter, a method for manufacturing the superconducting element of the first embodiment will be described with reference to FIG.

First, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 having a single orientation of (00l) and a layer thickness of 200 nm is formed on the MgO single crystal substrate 1. Specifically, Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y sintered body is adopted as the target, and the temperature of the MgO single crystal substrate 1 is raised to about 700 ° C., and the atmosphere is mixed with argon and oxygen. Off-axis DC magnetron sputtering (DC magnetron sputter deposition) was performed using a mixed gas with a ratio of Ar: O ₂ = 9: 1 and atmospheric pressure of 80 mTorr, and the plane orientation was (00 l) on the MgO single crystal substrate 1 A Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 having a single orientation of 200 nm and a layer thickness of 200 nm is formed.

Next, after the film formation of the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 is completed, the heating of the MgO single crystal substrate 1 is immediately stopped, and at the same time, O in the film formation chamber is maintained until the inside of the film formation chamber reaches 300 Torr. ₂ is introduced, and the temperature in the deposition chamber is lowered to room temperature over a period of about 20 minutes.

Subsequently, the MgO insulator layer 3 is formed on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2. Specifically, the MgO single crystal is adopted as a target, and the temperature of the MgO single crystal substrate 1 is raised to about 300 ° C., and the atmosphere is mixed with an argon / oxygen ratio of Ar: O ₂ = 1: 1. On-axis RF magnetron sputtering (RF magnetron sputter deposition) using a mixed gas with a pressure of 50 mTorr and a MgO insulator with a layer thickness of 200 nm on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 Layer 3 is formed.

Finally, similar to the cooling after the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 was formed, after the inside of the film forming chamber was cooled in an O ₂ atmosphere, the first oxide superconductor layer was formed. Similarly, Y _0.9 Ba _1.9 La _0.2 Cu having a single orientation of (00 l) and a layer thickness of 200 nm on the MgO insulator layer 3 as an example of the second oxide superconductor layer. ₃ O _y layer 4 is generated to complete the superconducting element.

(Second embodiment)
FIG. 2 is a cross-sectional view showing the layer structure of the superconducting element of the second embodiment.

The superconducting element of the second embodiment includes a BaZrO ₃ thin film layer as an example of the first insulating thin film layer between the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 and the MgO insulator layer 3 made of MgO. 5 is different from the superconducting element of the first embodiment. In the superconducting element of the second embodiment, the same effects and modifications as those of the superconducting element of the first embodiment are omitted, and only the actions and effects different from those of the superconducting element of the first embodiment are described.

  Hereinafter, a method for manufacturing the superconducting element of the second embodiment will be described with reference to FIG.

First, the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 as an example of the first oxide superconductor layer is formed on the MgO single crystal substrate 1 by the same method as the superconducting element of the first embodiment. .

Next, on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2, BaZrO ₃ as an example of a first insulating thin film layer having a single orientation of (k00) and a layer thickness of 20 nm is provided. A thin film layer 5 is formed. Specifically, a BaZrO ₃ sintered body is used as a target, and the temperature of the MgO single crystal substrate 1 is increased to about 720 ° C. to 740 ° C., and the atmosphere is pulsed using O ₂ with an atmospheric pressure of 50 mTorr. Using a laser deposition (PLD) method, a BaZrO ₃ thin film layer 5 having a single orientation of (k00) and a layer thickness of 20 nm is formed on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 Form. In the second embodiment, when performing pulsed laser deposition (PLD), an irradiation energy of 600 mJ was used as the irradiation energy of the laser, and a laser pulse having a frequency of 5 Hz was used as the frequency of the laser pulse.

Thereafter, in the first embodiment, after cooling similar to the cooling performed after the formation of the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2, the BaZrO ₃ thin film is formed by the same method as in the first embodiment. An MgO insulator layer 3 and a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as a second oxide superconductor layer are sequentially formed on the layer 5 to complete the superconducting element.

(Third embodiment)
FIG. 3 is a cross-sectional view showing the layer structure of the superconducting element of the third embodiment.

The superconducting element of the third embodiment is provided between the MgO insulator layer 3 made of MgO and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as an example of the second oxide superconductor layer. This is different from the superconducting element of the first embodiment in that a BaZrO ₃ thin film layer 6 is formed as an example of the insulating thin film layer. In the superconducting element of the third embodiment, the same operations and effects as those of the superconducting element of the first embodiment are omitted, and only the operations and effects different from those of the superconducting element of the first embodiment are described.

  Hereinafter, a method for manufacturing the superconducting element of the third embodiment will be described with reference to FIG.

First, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 as an example of the first oxide superconductor layer 2 on the MgO single crystal substrate 1 in the same manner as the superconducting element of the first embodiment, MgO insulation The body layer 3 is formed sequentially.

Next, a BaZrO ₃ thin film layer 6 as an example of a second insulating thin film layer having a single orientation with a plane orientation of (k00) and a layer thickness of 20 nm is formed on the MgO insulator layer 3. Specifically, a BaZrO ₃ sintered body is used as a target, and the temperature of the MgO single crystal substrate 1 is increased to about 720 ° C. to 740 ° C., and the atmosphere is pulsed using O ₂ with an atmospheric pressure of 50 mTorr. A BaZrO ₃ thin film layer 6 having a single orientation with a plane orientation of (k00) and a thickness of 20 nm is formed on the MgO insulator layer 3 using a laser deposition (PLD) method. In the third embodiment, when performing pulsed laser deposition (PLD), an irradiation energy of 600 mJ was used as the irradiation energy of the laser, and a laser pulse having a frequency of 5 Hz was used as the frequency of the laser pulse.

Finally, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as an example of the second oxide superconductor layer is formed on the BaZrO ₃ thin film layer 6 by the same method as in the first embodiment. To complete the superconducting element.

(Fourth embodiment)
FIG. 4 is a cross-sectional view showing the layer structure of the superconducting element of the fourth embodiment.

The superconducting element of the fourth embodiment is provided between the MgO insulator layer 3 made of MgO and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as an example of the second oxide superconductor layer. This is different from the superconducting element of the second embodiment in that a BaZrO ₃ thin film layer 6 is formed as an example of the insulating thin film layer.

  Hereinafter, a method of manufacturing the superconducting element of the fourth embodiment will be described with reference to FIG.

First, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2, a BaZrO ₃ thin film layer 5, and an MgO insulator layer 3 are sequentially formed on the MgO single crystal substrate 1 by the same method as the superconducting element of the second embodiment. To do.

Next, as in the third embodiment, a BaZrO ₃ thin film layer 6 and a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 are deposited on the MgO insulator layer 3 to complete the superconducting element.

FIG. 5 shows a surface scanning electron microscopic image of the surface of the MgO insulator layer 3 deposited on the BaZrO ₃ 5 thin film layer or the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 (surface SEM (scanning electron microscope) image).

From the surface scanning electron microscope image shown in FIG. 5, it was observed that the average surface roughness (Ra) in the range of 10 μm ² of the MgO insulator layer 3 was about 2 nm. For this reason, if you select a BaZrO ₃ thin film layer or Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y as the layer that forms the MgO insulator layer on its surface, MgO is extremely flat, has low distortion, and has excellent crystallinity. The insulator layer 3 can be formed, and the crystallinity of the layer formed on the MgO insulator layer 3 which is very flat and has low distortion and excellent crystallinity can be improved.

FIG. 6 is a diagram showing the relationship between the frequency of the applied voltage, the dielectric constant, and the conductivity in the insulator layer formed of the BaZrO ₃ thin film layer and the MgO insulator layer used in the second embodiment. is there.

  In FIG. 6, ● represents measured values of dielectric constant and conductivity when the temperature of the insulator layer is 4K, and ▲ represents measured values of dielectric constant and conductivity when the temperature of the insulator layer is 20K. ♦ indicates the measured values of dielectric constant and conductivity when the temperature of the insulator layer is 40K.

  As shown in FIG. 6, the dielectric constant of the insulator layer is about 11 without depending on the temperature of the insulator layer within the range of 4K to 40K which is the operating temperature of the device using the oxide superconductor. The dielectric constant is lower than the dielectric constant of 17 to 30 of the interlayer insulating film of the oxide superconductor layer that has been conventionally used.

Further, as shown in FIG. 6, the conductivity of the insulator layer tends to increase as the frequency increases, but is a value of about 10 ⁻⁷ S at the maximum. For this reason, when the insulator layer is composed of an MgO insulator layer and a BaZrO ₃ thin film layer, the conductivity can be made smaller than about 10 ⁻⁷ S, and there is no problem in terms of insulation.

In addition, when an insulator layer is formed with a single layer of MgO insulator layer, a dielectric constant substantially equivalent to the above could be obtained, while an insulator layer comprised of an MgO insulator layer and a BaZrO ₃ thin film layer and In comparison, there was a tendency that the surface roughness Ra of the MgO insulator layer surface was slightly deteriorated. Therefore, a superconducting element having excellent surface flatness can be formed by forming a BaZrO ₃ thin film layer on an oxide superconductor layer such as a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer.

As for the thickness of the MgO insulator layer, insulation was not ensured at a layer thickness of 30 nm or less. In addition, when the layer thickness is 600 nm or more, the phenomenon that the surface flatness of the MgO insulator layer deteriorates is observed, and the oxide superconductor layer such as Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer on the MgO insulator layer is observed. Lattice defects such as cracks occurred, and the device characteristics of the superconducting device were greatly deteriorated.

Furthermore, the present inventor observed the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer on the MgO insulator layer or on the BaZrO ₃ thin film layer as the second insulating thin film layer.

As a result, directly to the MgO insulator layer _{Y 0.9 Ba 1.9 La 0.2 Cu 3} O even when the _y layer is formed, the MgO insulator layer through a BaZrO ₃ film layer indirectly Y _0.9 Ba _1.9 La _{Even when the 0.2} Cu ₃ O _y layer was formed, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer was obtained as a second oxide superconductor layer that was generally good in terms of crystallinity and surface flatness.

However, in the case of the first and second embodiments in which the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer was formed directly on the MgO insulator layer, minute protrusions having a diameter of about 10 nm were observed on the surface. This does not seriously affect the superconducting element and can be used as it is. However, after the BaZrO ₃ thin film layer 6 is formed on the MgO insulator layer 3, the second oxidation is performed thereon. In the case of the third and fourth embodiments in which the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as a superconductor layer is formed, the above-mentioned protrusion is not seen, and Y _0.9 Ba _1.9 La _0.2 Cu ₃ O The flatness of the _y layer 6 was further improved.

From this, when the BaZrO ₃ thin film layer 6 is formed on the MgO insulator layer 3, the second oxide superconductor layer having excellent crystallinity can be formed on the BaZrO ₃ thin film layer 6.

According to the superconducting elements of the first to fourth embodiments, the MgO insulator layer 3 made of MgO is formed on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2. It can be lowered and the electrical insulation can be increased. Therefore, the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 can be insulated without problems.

Further, according to the superconducting elements of the first to fourth embodiments, since the MgO insulator layer 3 is formed on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2, the dielectric of the insulating layer The ratio can be greatly reduced from the conventional value of about 17-30 to about 10, and between Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 and Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 The capacitance of the capacitance component formed can be much smaller than before. Accordingly, the dielectric loss can be reduced, the disturbance of the waveform of the high frequency signal can be prevented, and the circuit can be easily designed.

  In addition, according to the superconducting elements of the first to fourth embodiments, the MgO insulator layer 3 is set to a thickness of 200 nm and set to 30 nm or more, so that sufficient insulation can be ensured. . Further, since the thickness of the MgO insulator layer 3 is 200 nm and 600 nm or less, deterioration of the flatness of the surface of the insulator layer can be avoided.

Further, according to the superconducting element of the second embodiment, between the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 as an example of the first oxide superconductor layer, and the MgO insulator layer 3, Since the BaZrO ₃ thin film layer 5 was formed as an example of the first insulating thin film layer, an undesirable reaction that may occur between the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 and the MgO insulator layer 3 Can be prevented. Therefore, the element characteristics of the superconducting element can be improved, and the life of the superconducting element can be extended. If an electronic device or the like is manufactured using this superconducting element, the operation of the electronic device or the like can be increased over a long period of time, and power consumption can be significantly reduced.

In addition, according to the superconducting element of the third embodiment, the second layer is provided between the MgO insulator layer 3 and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 as the second oxide superconductor layer. Since the BaZrO ₃ thin film layer 6 is formed as an insulating thin film layer, an undesirable reaction that may occur between the MgO insulator layer 3 and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 is prevented. can do. Therefore, the element characteristics of the superconducting element can be improved, and the life of the superconducting element can be extended. If an electronic device or the like is manufactured using this superconducting element, the operation of the electronic device or the like can be increased over a long period of time, and power consumption can be significantly reduced.

Further, according to the superconducting element of the fourth embodiment, between the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 as an example of the first oxide superconductor layer, and the MgO insulator layer 3, A BaZrO ₃ thin film layer 5 is formed as an example of the first insulating thin film layer, and an Mg _0.9 insulator layer 3 and a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer as an example of the second oxide superconductor layer are formed. Since the BaZrO ₃ thin film layer 6 as the second insulating thin film layer is formed between the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 2 and the MgO insulator layer 3 And undesirable reactions that may occur between the MgO insulator layer 3 and the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 4 can be prevented. . Therefore, the element characteristics of the superconducting element can be improved, and the life of the superconducting element can be extended. In addition, the operation of an electronic device or the like having this superconducting element can be increased in speed over a long period of time, and power consumption can be significantly reduced.

  In the superconducting elements of the first to fourth embodiments, the thickness of the MgO insulator layer 3 is set to 200 nm. However, if the thickness of the MgO insulator layer is set to 30 nm or more and 600 nm or less, The same effects as the superconducting elements of the first to fourth embodiments can be obtained.

(Fifth embodiment)
FIG. 7 is a cross-sectional view showing the layer structure of the superconducting element of the fifth embodiment of the present invention.

  The superconducting element of the fifth embodiment is a so-called ramp edge type Josephson junction element applied in an electronic circuit using an oxide superconductor.

In the fifth embodiment, a MgO insulator layer made of MgO, a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 32 called a ground plane as an example of the first oxide superconductor layer on the MgO single crystal substrate 31. 33, an insulator such as a Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 34 called a base electrode as an example of the second oxide superconductor layer, and an SrSnO ₃ insulating layer conventionally used as an insulator Layers 35 are sequentially stacked.

In addition, the layer is etched obliquely from the insulator layer 35 as an upper layer to a part of the insulator layer 33 as a lower layer to form a slope. Then, on the surface of the insulator layer 35, on the slope, and on the surface of the insulator layer 33 that is connected to the slope and exposed by the etching, called a counter electrode that is a third oxide superconductor layer Yb _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 36 is deposited.

In addition, an extremely thin insulator is formed between the slope of the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 34 and the Yb _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 36 layer. The Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 34, the ultrathin insulator, and the Yb _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer 36 constitute a Josephson junction 37.

  According to the superconducting element of the fifth embodiment, since the MgO insulator layer 33 made of MgO is employed as the insulator layer between the ground plane and the base electrode layer, the insulator between the ground plane and the base electrode layer. The dielectric constant of the layer can be made smaller than before. Therefore, the capacitance component can be reduced, so that the dielectric loss can be reduced and the disturbance of the waveform of the high frequency signal can be prevented.

In the superconducting element of the fifth embodiment, the MgO insulator layer 33 is employed as the insulator layer between the ground plane and the base electrode layer. However, in the superconducting element of the present invention, the ground plane and the base electrode layer are separated from each other. An insulator layer composed of an MgO insulator layer and one BaZrO ₃ thin film layer may be adopted as the insulator layer between them. In the superconducting element of the present invention, an insulator layer having a structure in which an MgO insulator layer is sandwiched between two BaZrO ₃ thin film layers may be adopted as an insulator layer between a ground plane and a base electrode layer. good. When an insulator layer composed of an MgO insulator layer and one or two BaZrO ₃ thin film layers is used as an insulator layer between the ground plane and the base electrode layer, the crystallinity is excellent on the insulator layer. A base electrode can be formed.

(Sixth embodiment)
FIG. 8 is a cross-sectional view showing the layer structure of the superconducting element of the sixth embodiment of the present invention.

In the superconducting element of the sixth embodiment, the insulator layer between the ground plane and the base electrode layer is composed of a conventionally used insulating layer 43 such as an SrSnO ₃ insulating layer, and the base electrode layer and the counter electrode layer The difference between the superconducting element of the fifth embodiment is that the intermediate insulator layer is composed of an MgO insulator layer 45 made of MgO.

  According to the superconducting element of the sixth embodiment, since the MgO insulator layer 45 made of MgO is employed as the insulator layer between the base electrode layer and the counter electrode layer, the insulator layer of the base electrode layer and the counter electrode layer The dielectric constant can be made smaller than before. Therefore, the capacitance component can be reduced, so that the dielectric loss can be reduced and the disturbance of the waveform of the high frequency signal can be prevented.

In the superconducting element of the sixth embodiment, the MgO insulator layer 45 is employed as the insulator layer between the base electrode layer and the counter electrode layer. However, in the superconducting element of the present invention, the base electrode layer and the counter electrode are used. As an insulator layer between the layers, an insulator layer composed of an MgO insulator layer and one BaZrO ₃ thin film layer may be adopted. In the superconducting element of the present invention, an insulator layer having a structure in which an MgO insulator layer is sandwiched between two BaZrO ₃ thin film layers is employed as an insulator layer between a base electrode layer and a counter electrode layer. Also good. When an insulator layer composed of an MgO insulator layer and one or two BaZrO ₃ thin film layers is used as an insulator layer between the base electrode layer and the counter electrode layer, the crystallinity is excellent on the insulator layer. Counter electrodes can be formed.

In the superconducting element of the sixth embodiment, the conventionally used insulating layer 43 such as SrSnO ₃ insulating layer is employed as the insulator layer between the ground plane and the base electrode layer. Then, as an insulator layer between the ground plane and the base electrode layer, an MgO insulator layer composed of MgO, an insulator layer composed of an MgO insulator layer and one BaZrO ₃ thin film layer, or two BaZrO ₃ thin films Of course, an insulator layer of a type in which an MgO insulator layer is sandwiched between layers may be adopted. In addition to the insulator layer between the base electrode layer and the counter electrode layer, when these insulator layers are employed as the insulator layer between the ground plane and the base electrode layer, superconductivity with even faster operation is achieved. An element can be formed.

In the superconducting elements of the first to sixth embodiments and all the modifications described above, the MgO insulator layer is composed of one continuous layer. However, in the superconducting element of the present invention, the MgO insulator layer is A plurality of discrete layers may be arranged, and a BaZrO ₃ thin film layer may be formed between the discrete MgO insulator layers.

Further, in the superconducting elements of the first to sixth embodiments and all the modifications described above, the BaZrO ₃ thin film layer is employed as the first or second insulating thin film layer. However, in the superconducting element of the present invention, , SrMoO ₃ thin film layer, Ba ₂ NdTaO ₆ thin film layer, (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 thin film layer, SrHfO ₃ thin film layer, BaSnO ₃ thin film layer as the first or second insulating thin film layer Even in this case, it is possible to obtain the same function and effect as the case where the BaZrO ₃ thin film layer is employed as the first or second insulating thin film layer. In the superconducting element of the present invention, the first or second insulating thin film layer is formed of a BaZrO ₃ thin film layer, (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 thin film layer, Ba ₂ NdTaO ₆ thin film layer, SrHfO ₃ thin layer, SrMoO ₃ thin film layer may be formed an insulating thin film layer by laminating two or more thin layers of the BaSnO ₃ thin layer. In this case, by appropriately selecting two or more thin film layers, the lattice matching between the first or second insulating thin film layer and the insulating layer made of MgO can be improved, so that the insulating material made of MgO can be improved. It is possible to effectively prevent an undesirable reaction from occurring due to contact between the layer and the first or second oxide superconductor layer.

In the superconducting elements of the first to sixth embodiments and all the modifications described above, Yb _0.9 Ba _1.9 La _0.2 Cu ₃ O _y is used as the first, second, or third oxide superconductor layer. Layer, or Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer was adopted, but in the superconducting element of the present invention, YBa ₂ Cu ₃ O _y layer was adopted as the first, second or third oxide superconductor layer Alternatively, an oxide superconductor layer using an oxide superconductor material in which Y of YBa ₂ Cu ₃ O _y is substituted with a rare earth element other than Y may be employed. In these cases, the same effects as the superconducting elements of the first to sixth embodiments can be obtained. Here, the following 12 elements exhibiting superconducting characteristics when the rare earth element is replaced with Y in the rare earth, that is, Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, It shall be defined by Yb and Lu.

In the superconducting elements of the first to sixth embodiments and all the modifications described above, an MgO single crystal substrate is employed as the substrate. However, in the superconducting element of the present invention, SrToO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7, etc. A substrate other than the MgO single crystal substrate that is usually used for manufacturing an oxide superconductor device may be used.

  Of course, the layer thickness of each layer of the superconducting element of the present invention is not limited to the numerical value of the layer thickness of each layer specifically described in the superconducting element of the above embodiment.

  The first oxide superconductor layer is formed on the first oxide superconductor layer, and at least partly includes an MgO insulating layer, and is formed on the insulating layer. Of course, all superconducting elements partially having a structure composed of the second oxide superconductor layer fall within the scope of the present invention. For example, superconducting elements such as all ramp edge type Josephson junction elements partially having the above structure and all layered type Josephson junction elements partially having the above structure fall within the scope of the present invention. is there.

1 is a schematic cross-sectional view showing a layer configuration of a superconducting element according to a first embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a layer configuration of a superconducting element according to a second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a layer configuration of a superconducting element of a third embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing a layer configuration of a superconducting element of a fourth embodiment of the present invention. Surface SEM of the MgO insulator layer surface deposited on the BaZrO ₃ thin film layer as the first insulating thin film layer or on the Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer as the first oxide superconductor layer It is a figure which shows an image. In BaZrO ₃ film layer and the MgO insulator layer and the insulator layer formed at the frequency of the applied voltage is a diagram showing the relationship between the dielectric constant and conductivity. FIG. 7 is a schematic cross-sectional view showing a layer configuration of a superconducting element according to a fifth embodiment of the present invention. FIG. 10 is a schematic cross-sectional view showing a layer configuration of a superconducting element according to a sixth embodiment of the present invention.

Explanation of symbols

1 MgO single crystal substrate
2,32,34 Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer
3,33,45 MgO insulator layer
4 Y _0.9 Ba _1.9 La _0.2 Cu ₃ O _y layer
5,6 BaZrO ₃ thin film layer

Claims (9)

A first oxide superconductor layer;
An insulating layer formed on the first oxide superconductor layer and made of MgO;
A superconducting element comprising: a second oxide superconductor layer formed on the insulating layer. In the superconducting device according to claim 1,
A superconducting element comprising a first insulating thin film layer between the first oxide superconductor layer and the insulating layer. In the superconducting element according to claim 2,
The superconducting element, wherein the first insulating thin film layer is composed of a plurality of layers. In the superconducting device according to claim 1,
A superconducting element comprising a second insulating thin film layer between the insulating layer and the second oxide superconductor layer. In the superconducting element according to claim 4,
The superconducting element, wherein the second insulating thin film layer is composed of a plurality of layers. In the superconducting element according to claim 2,
Whether the first insulating thin film layer is made of any one of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO ₃ Or a superconducting element comprising two or more of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO ₃ . In the superconducting element according to claim 4,
Whether the second insulating thin film layer is made of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO _3, or BaSnO ₃ Or a superconducting element comprising two or more of BaZrO ₃ , (LaAlO ₃ ) _0.3 (SrAl _0.5 Ta _0.5 O ₃ ) _0.7 , Ba ₂ NdTaO ₆ , SrHfO ₃ , SrMoO ₃ and BaSnO ₃ . In the superconducting device according to claim 1,
A superconducting element, wherein the insulating layer has a thickness of 30 nm or more. In the superconducting device according to claim 1,
A superconducting element, wherein the insulating layer has a thickness of 600 nm or less.