JPH1127015A - Superconductive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the Q value of a superconductive element which contains a superconductive resonance element, a dielectric member which is added to the resonance element and varies its dielectric constant according to the applied voltage and an electrode which applies the voltage to the dielectric member by setting the electrode and a strip conductor to satisfy a prescribed relation between them. SOLUTION: The YBCO superconductive films 12a and 12b are formed on both upper and rear side surfaces of an LaAlO3 monocrystal substrate 11. The film 12a formed on the upper surface of the substrate 11 is processed into a stripe shape as a strip conductor 12a. Then an SrTiO3 film 13 of 1 μm is formed on the upper surface of the substrate 11, and the conductive films are formed and processed into the comb-line electrodes 14a to 14d on the film 13. In such cases, the size of an area where the conductor 12a is overlapping the electrodes 14a to 14d is set less than 20% of the area size of the conductor 12a when viewed at a point set above a superconductive element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting element, and more particularly to a superconducting element such as a resonator and a filter constituted by a superconducting resonance element.

[0002]

2. Description of the Related Art A filter for extracting only a desired frequency band is one of important components in communication equipment for performing information communication regardless of whether it is wireless or wired. For effective use of frequency and energy saving, this type of filter is required to have excellent attenuation characteristics and small insertion loss. To construct such a filter, Q
A high value resonator is required.

One method of realizing a resonator having a high Q value is to use a superconductor as a metal conductor constituting the resonator and use a very low-loss material such as sapphire or MgO for a dielectric substrate. . The Q value obtained by this method is 10,000 or more, and the resonance characteristics are very sharp. Particularly, a resonator using an oxide superconductor having a low cooling cost as a superconductor has been developed.

Further, by using such a resonator having a high Q value and directly filtering a high frequency signal in the GHz band and eliminating the frequency converter, it is possible to reduce the cost of the filter. Further, if the resonance frequency of the resonator is positively changed and an arbitrary frequency is selectively extracted, the cost can be further reduced.

[0005] The following are known as resonators (filters) having a function of changing the resonance frequency.

For example, Japanese Patent Application Laid-Open No. 1-190001 discloses that a resonator is composed of a superconductor having two different values of a critical magnetic field, and the strength of a magnetic field applied to these superconductors is adjusted to adjust the superconductivity. A method is disclosed in which characteristics are broken and the resonance frequency is thereby changed.

However, this method requires a magnetic field generator for generating a strong magnetic field in order to change the superconducting characteristics, and has a problem that the device becomes large-scale and it is difficult to reduce the size.

[0008] Applied Physics
Letters Vol. 63 (1993) No. 6 830
The page discloses a method in which a heating element is provided in the vicinity of a resonator formed of a superconductor, and the superconducting characteristics are destroyed by heat. According to this method, the device configuration can be simplified as compared with the previous method.

[0009] However, there is a problem that the operating speed becomes slow because it is necessary to generate a heat by applying a current to the heating element. Here, in order to increase the operation speed, the environmental temperature of the resonator may be maintained near the critical temperature of the superconductor, but it is very difficult to maintain such an environmental temperature.

A common problem of the above two methods is that the low loss property, which is an advantage of the superconductor, is sacrificed. The reason is that the superconducting characteristics of the superconductor are broken in order to make the resonance frequency variable.

[0011] Also, IEEE MTT-S Digests
t (1993), p. 1421, a gap is provided at the center of the transmission line, a dielectric member whose permittivity changes according to the applied voltage is attached to the gap, and the resonance frequency is set by applying a voltage to the transmission line. A method of changing is disclosed.

However, in this method, since a gap must be provided at the maximum current point at the center of the transmission line serving as the resonance element, the Q value becomes 1000 or less, and there is a problem that a sharp resonator cannot be obtained. .

A dielectric member whose permittivity changes according to an applied voltage is attached near the resonator, and a metal thin film thinner than the penetration depth of the electromagnetic wave is provided above and below the dielectric member, or on the dielectric member. There has also been proposed a method in which interdigitated comb-shaped electrodes thinner than the penetration depth of an electromagnetic wave are provided, and a resonance frequency is changed by applying a voltage to the metal thin film or the comb-shaped electrodes.

However, even if the metal thin film and the comb-like electrode are thinner than the penetration depth of the electromagnetic wave, the metal thin film and the linear electrode are arranged so as to intersect with the strip conductor of the resonator, and the length of the intersecting portion is set. If the length exceeds one half of the length of the wavelength corresponding to the resonance frequency, there is a problem that resonance is not observed or the Q value is reduced.

[0015]

As described above, various resonators using a superconductor and having a variable resonance frequency have been proposed, but it is difficult to reduce the size of these resonators. And the operation speed is slow and the Q value is low.

The present invention has been made in consideration of the above circumstances, and has as its object to change a resonance frequency having a high Q value, which does not make it difficult to reduce the size or slow down the operation speed. It is an object of the present invention to provide a superconducting element comprising a superconducting resonance element.

[0017]

In order to achieve the above object, a superconducting element according to the present invention (Claim 1) comprises a substrate on which a strip conductor made of a superconductor is provided, and a strip conductor made of a superconductor is provided above or below the substrate. A superconducting resonant element provided with a ground, a dielectric member provided on the superconducting resonant element, the permittivity of which changes according to an applied voltage, and an electrode for applying a voltage to the dielectric member; When viewed from above, the area of the region where the strip conductor and the electrode overlap is not more than 20% of the area of the strip conductor.

With such a configuration, as will be described in detail later, the Q value of the superconductor resonant element can be sufficiently increased. Further, since the resonance frequency is changed by a voltage, a magnetic field generating means and a heating element are unnecessary. Therefore,
There is no problem that miniaturization is difficult or the operation speed is slow.

Further, another superconducting element according to the present invention (claim 2) is the superconducting element (claim 1), wherein the electrode is perpendicular to the longitudinal direction of the strip conductor and the superconducting element. When the wavelength exceeds 1/2 of the length of the wavelength (hereinafter referred to as L ₀ ) corresponding to the resonance frequency of the resonance element, the width thereof is 10% or less of L _0/2 , and when viewed from above the element. , the sum of the areas of those present on the strip conductors, the sum of the total area of those present in the region away to L _0/4 in a direction perpendicular to the longitudinal direction from said strip conductor, (L ₀
/ 2) 20% or less of ² .

With such a configuration, as described in detail later, the Q value of the superconductor resonance element can be made sufficiently high as in the case of the above-described superconductor element (claim 1). Similarly, there is no problem that downsizing becomes difficult or the operation speed becomes slow.

Further, another superconducting element according to the present invention (Claim 3) is the above-described superconducting element (Claims 1 and 2).
The electrode is constituted by a plurality of linear electrodes crossing the strip conductor in a direction perpendicular to a longitudinal direction of the strip conductor.

Conventionally, it was thought that if electrodes were arranged so as to intersect with the strip conductor, the Q value would be reduced and the required resonance characteristics would not be obtained. If it satisfies, the required resonance characteristics can be obtained even if the electrodes are arranged so as to intersect with the strip conductor (claim 3).

Further, another superconducting element according to the present invention (claim 4) is the superconducting element (claims 1 and 2)
The electrode has two sets of a pair of comb-shaped electrodes arranged so as to mesh with each other, and a linear electrode forming a tooth portion of the comb-shaped electrode is parallel to a longitudinal direction of the strip conductor. The pair of comb-shaped electrodes is arranged on each of both sides of the strip conductor so as not to contact the strip conductor.

Further, another superconducting element according to the present invention (claim 4) includes a first substrate, a ground provided on the first substrate, and a ground provided on the ground via a second substrate. A superconducting resonance element comprising a strip conductor made of a superconductor, and a dielectric member provided on the superconducting resonance element so as not to be in contact with the second substrate and the strip, and having a dielectric constant that changes in accordance with an applied voltage; It is for applying a voltage to the dielectric member, and is characterized by comprising an electrode not in contact with the second substrate and the strip.

With such a configuration, the area of the region where the strip conductor and the electrode overlap with each other is zero, so that the same operation and effect as the superconducting element (claim 1) can be obtained.

[0026]

Embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

First, experimental results and the like on which the present invention is based will be described. FIG. 1 is a sectional perspective view showing the structure of the microstrip resonator. The high-frequency signal is applied to a strip conductor 2 provided on the surface of the substrate 1 (ε _r > ε ₀ ).
(Width W, thickness t) and ground plane 3 on the back surface of substrate 1
And propagates while creating an electric field as shown in FIG.

At this time, if a conductive substance is present in the vicinity of the strip conductor 2, especially on the upper part of the strip conductor 2, even if an electromagnetic wave is transmitted through the conductive substance, the electromagnetic field is disturbed and the resonance characteristics, especially the Q value, are deteriorated. I do.

FIG. 3 shows an area ratio (S / S ₀ ) where the conductive film 4 covers the strip conductor 2 when the conductive film 4 having a thickness of 50 nm is disposed at a distance of 1 μm directly above the microstrip resonator. FIG. 4 is a diagram showing a relationship between the Q value. Here, S is the area of the conductive film 4 as viewed from above the resonator,
S ₀ is the area of the strip conductor 2 as viewed from above the resonator.

As shown in the figure, the smaller the area ratio (S / S ₀ ), that is, the conductive film 4 disposed on the strip conductor 2
It can be seen that the smaller the (conductive substance), the larger the Q value and the better the resonance characteristics.

From the figure, it can be seen that the area ratio of the conductive film 4 covering the strip conductor 2 is 20% or less, preferably 10% or less, more preferably 1% or less. By setting such a value, a Q value larger than 1 × 10 ³ can be realized.

FIG. 4 shows a linear electrode 5 made of a conductive material having a width of W1 and a length of L in the vicinity of the strip conductor, as shown in FIGS. 5 shows a relationship between the length L and the Q value when the strip conductor 2 is arranged in a direction perpendicular to the longitudinal direction. FIG.
, The linear electrode 5 intersects the strip conductor 2, and in FIG. 6, the linear electrode 5 does not intersect the strip conductor 2. When changing the resonance frequency, a voltage is applied so that the adjacent linear electrodes 5 have opposite polarities.

FIG. 4 shows that the linear electrode 5 is
, (FIG. 5), the length L of the linear electrode 5
Is 1 of the length L ₀ of the wavelength corresponding to the resonance frequency of the resonator.
It can be seen that a Q value as high as 1 × 10 ⁵ can be obtained at / 2 or less.

FIG. 4 shows that when the length L exceeds １ ／ of L ₀ , the Q value sharply decreases. The change is more remarkable as the number of the linear electrodes 5, that is, the total area of the linear electrodes increases.

[0035] That is, the sum of the areas of the linear electrode 5 present on the strip conductor 2, a region R away from the strip conductor 2 to L _0/4 in a direction perpendicular to the longitudinal direction
(See FIG. 7) When the sum (total area) with the total area of the linear electrodes 5 present in the area exceeds 20% of (L _0/2 ), Q
It can be seen that the value drops to around 10,000, above 30% to around 1000 and above 50% to around 100.

On the other hand, when the linear electrode 5 intersects the strip conductor 2 (FIG. 6), the Q value originally decreases depending on the area ratio (S / S ₀ ), but the length L is L _0. Of 1
It can be seen that when the value exceeds / 2, the Q value decreases more rapidly.

These phenomena are that the length of the linear electrode 5 in the direction perpendicular to the longitudinal direction of the strip conductor 2 is 1 / L of L ₀ .
It is considered that when the value exceeds 2, the electromagnetic wave leaks to the linear electrode 5 orthogonal to the strip conductor 2.

Therefore, to increase the Q value,
Basically, it can be seen that it is sufficient to use a linear electrode 5 having a length in a direction perpendicular to the longitudinal direction of the strip conductor 2 equal to or less than 1/2 of L ₀ .

However, when the linear electrodes 5 are arranged such that the length in the direction perpendicular to the longitudinal direction of the strip conductor 2 exceeds 1/2 of L ₀ , the length is simply reduced to L _0/2 or less. in sufficient Q value is not obtained, in order to suppress a decrease in the Q value, the width W1 of the linear electrodes 5 respectively (L _0/2)
10%, preferably set to be 1% or less, and comprehensive area of the linear electrode 5 (L _0/2) 20% of ² or less, preferably may be such that less than 1%.

Also, as shown in FIG. 8, the comb electrodes 6a to 6d are constituted by the linear electrodes 5, and the linear electrodes 5 are arranged so as to be parallel to the longitudinal direction of the strip conductor 2. good.

In this case, the width W1 of one linear electrode 5 is 1
It is desirable that the distance W2 between the linear electrodes is 1 μm or more and 1 mm or less. Further, the comb-shaped electrodes 6b, 6d
It is desirable that the interval between the linear electrode 5 closest to the strip conductor 2 and the strip conductor 2 be equal to or less than the interval W2, and preferably 1/2 of the interval W2.

In such a resonator, the strip conductor 2
When a voltage is applied between the linear electrodes 6a and 6d on both sides of the strip electrode, the electric field formed in the dielectric film in the vicinity is not the distance between the linear electrodes 6a and 6d, Is determined by the distance minus the width of
A strong electric field can be created.

In particular, when the distance between the strip conductor 2 and the nearest linear electrode 5 on both sides is set to 1/2 of the distance W2 as described above, the magnitude of the electric field is different from that of the other. The electric field becomes the same as that between the linear electrodes 5, and the electric field does not become non-uniform and the control of the dielectric constant becomes easy.

Further, the vicinity of both sides of the strip conductor 2 is where the propagated electromagnetic field becomes dense, and an electric field can be effectively applied to the dielectric film in this portion, so that the resonance frequency can be changed more effectively. Can be.

The area where the permittivity is changed may be only the area where the propagation electromagnetic field is distributed, and may be an area within 5 times the width of the strip conductor 2 from the strip conductor 2 to both sides.

Further, even if the electrodes are arranged so as not to be on the strip conductor, the influence of the electrodes cannot be reduced to zero.
An electrode near the strip conductor has a large effect on a change in the dielectric constant, that is, a change in the resonance frequency, but tends to cause a decrease in the Q value. Therefore, the arrangement of the electrodes should be considered in accordance with the amount of change in the resonance frequency and the Q value required for the application.

By setting the area ratio and the total area as described above, it is possible to make the resonance frequency variable while maintaining a high Q value. Further, since the resonance frequency is changed by a voltage, a magnetic field generating means and a heating element are unnecessary. Therefore, there is no problem that downsizing is difficult or the operation speed is slow.

(First Embodiment) FIGS. 9 and 10 are a plan view and a sectional view showing a method for manufacturing a superconductor resonator (hereinafter simply referred to as a resonator) according to a first embodiment of the present invention. is there. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view.

First, as shown in FIG.
After forming YBCO superconducting films 12a and 12b each having a thickness of 300 nm on the front surface and back surface of a LaAlO ₃ single crystal substrate 11 having a thickness of 0.5 mm, the YBCO superconducting film 12a on the front surface is processed into a stripe shape, and strip conductor 12a is formed.
To form The YBCO superconducting film 12b is used as a ground plane.

Here, the YBCO superconducting films 12a and 12b
Examples of the film forming method include a sputtering method, a laser evaporation method, and a CVD method.

Next, as shown in FIG. 10, a 1 μm thick SrTiO ₃ film 13 is formed on the surface of the LaAlO ₃ single crystal substrate 11.
To form The method for forming the SrTiO ₃ film 13 is YBC
This is the same as that of the O superconducting films 12a and 12b.

[0052] Then, as shown in the figure, SrTiO ₃ film 1
After forming a conductive film having a thickness of 50 nm to be the comb-shaped electrodes 14a to 14d on the third electrode 3, the conductive film is processed by using lithography and etching, so that the comb-shaped electrode 14a is formed.
To 14d.

Here, the comb electrodes 14a and 14b are arranged so as to mesh with each other, and the pair of comb electrodes 14a and 14b
14b is arranged beside the strip conductor 12a so as not to contact it. The linear electrodes forming the comb electrodes 14a and 14b are arranged in parallel to the longitudinal direction of the strip conductor 12a. The comb electrodes 14c and 14d have the same configuration.

The material of the conductive film to be the comb electrodes 14a to 14d is, for example, Au, Ag, Pt, C
electrode materials such as u, Al, and conductive ceramics. The linear electrodes constituting the comb electrodes 14a to 14d have a width of 10 μm, the interval between the linear electrodes is 10 μm, and the distance between the strip conductor 12a and the nearest linear electrode is 5 μm.
μm.

Finally, as shown in FIG.
By forming pad electrodes 15a to 15d connected to a to 14d, a resonator having a resonance frequency of 4.3 GHz is completed.

When the Q value of the resonator thus formed was examined, a high value of 50,000 was obtained. Therefore, by using the resonator of the present embodiment, it is possible to realize a filter having excellent attenuation characteristics and small insertion loss. The reason why such a high Q value is obtained is that the comb-shaped electrodes 14a to 14d are arranged so as to avoid over the strip conductor 12a. Further, since the resonance frequency is changed by a voltage, a magnetic field generating means and a heating element are unnecessary. Therefore, there is no problem that downsizing is difficult or the operation speed is slow.

The same potential is applied to the pad electrode 15a and the pad electrode 15d so that a potential difference occurs between the comb electrodes 14b and 14d closer to both sides of the strip conductor 12a. Also 50
V higher voltage is applied, and the pad electrode 1c is applied to the pad electrode 15c.
A voltage of 50 V higher than 5d was applied. At this time, a similar potential difference occurs between the comb-like electrodes 14b and 14d.

When the above-mentioned voltage is applied, an electric field of 50 KV / cm is generated between the comb-shaped electrodes, and the SrTiO ₃ film 13
Changes. As a result, the resonance frequency becomes about 2.3.
% And resonates at 4.4 GHz.

(Second Embodiment) FIGS. 11 and 12 are a plan view and a sectional view showing a method for manufacturing a resonator according to a second embodiment of the present invention. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view. Since the basic structure is the same as that of the first embodiment, the same reference numerals as in FIGS. 9 and 10 are used.

First, as shown in FIG.
After the YBCO superconducting films 12a and 12b having a thickness of 300 nm are formed on the front and back surfaces of the LaAlO ₃ single crystal substrate 11 having a thickness of 0.5 mm, the YBCO superconducting film 12a on the front surface is processed into a stripe shape, and the strip conductor is formed. 1
2a is formed. The method of forming the YBCO superconducting films 12a and 12b is the same as in the first embodiment.

Next, as shown in FIG. 12, a 1 μm thick SrTiO ₃ film 13 is formed on the surface of the LaAlO ₃ single crystal substrate 11.
To form The method for forming the SrTiO ₃ film 13 is YBC
This is the same as that of the O superconducting films 12a and 12b.

The operation up to this point is the same as in the first embodiment.

[0063] Then, as shown in the figure, SrTiO ₃ film 1
After forming a conductive film having a thickness of 50 nm to be the comb-shaped electrodes 14a to 14d on the substrate 3, the conductive film is processed using lithography and etching, so that the interdigitated comb-shaped electrodes 14a and 14b and the comb-shaped electrode 14c are formed. , 14d
To form

Here, the linear electrodes constituting the comb-shaped electrodes 14a to 14d and the interval between the linear electrodes are each set to 10 μm as in the first embodiment, but the strip conductor 12a and the nearest comb-shaped The distance between the electrodes 14b and 14d to the linear electrodes is 100 μm, which is 20 times longer than in the first embodiment. The material of the conductive film is the same as that of the first embodiment.

Finally, as shown in FIG.
By forming pad electrodes 15a to 15d connected to a to 14d, a resonator having a resonance frequency of 4.3 GHz is completed.

When the Q value of the resonator thus formed was examined, a high value of 60000 was obtained. The reason why such a high Q value was obtained is that the comb electrodes 14a to 14a
This is because 14d is arranged so as not to be on the strip conductor 12a.

The same potential is applied to the pad electrode 15a and the pad electrode 15d so that a potential difference occurs between the comb electrodes 14b and 14d closer to both sides of the strip conductor 12a. Also 50
V higher voltage is applied, and the pad electrode 1c is applied to the pad electrode 15c.
A voltage of 50 V higher than 5d was applied. At this time, a similar potential difference occurs between the comb-like electrodes 14b and 14d.

When the voltage as described above is applied, an electric field of 50 KV / cm is generated between the comb electrodes, and the SrTiO ₃ film 13
Changes. As a result, the resonance frequency changes,
Resonates at 4.38 GHz.

(Third Embodiment) FIGS. 13 and 14 are a plan view and a sectional view showing a method for manufacturing a resonator according to a third embodiment of the present invention. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view.

First, as shown in FIG. 13, similarly to the first embodiment, a LaAl having a diameter of 30 mm and a thickness of 0.5 mm was used.
Each of the O ₃ single crystal substrate 21 has a thickness of 3
After forming the YBCO superconducting films 22a and 22b of 00 nm, the YBCO superconducting film 12a on the surface is processed into a stripe shape to form a strip conductor 22a. The YBCO superconducting film 22b is used as a ground plane. YB
The method of forming the CO superconducting film 22 is the same as in the first embodiment.

Next, as shown in FIG. 14, an SrTiO ₃ film 23 having a thickness of 1 μm is formed on the surface of the LaAlO ₃ single crystal substrate 21.
To form The method of forming the SrTiO ₃ film 23 is YBC
It is the same as that of the O superconducting film 22.

[0072] Then, as shown in the figure, SrTiO ₃ film 2
After forming a conductive film having a thickness of 50 nm to become the L-shaped electrodes 24a and 24b on the L-shaped electrode 3, the conductive film is processed using lithography and etching, thereby forming the L-shaped electrode 2
4a and 24b are formed.

Here, as the material of the conductive film to be the L-shaped electrodes 24a and 24b, for example, Au, Ag, P
Examples of the electrode material include t, Cu, Al, and conductive ceramics.

The width of the L-shaped electrodes 24a and 24b is 10
μm, L-shaped electrodes 24a, 24b and strip conductor 22a
Is 10 μm.

Finally, pad electrodes (not shown) connected to the L-shaped electrodes 24a and 24b are formed, and a resonator having a resonance frequency of 4.3 GHz is completed.

When the Q value of the resonator thus formed was examined, a high value of 50,000 was obtained.
Therefore, by using the resonator of the present embodiment,
A filter having excellent attenuation characteristics and low insertion loss can be realized. The reason why such a high Q value was obtained is that
This is because the L-shaped electrodes 24a and 24b are arranged so as not to be on the strip conductor 22a.

Further, the L-shaped electrode 24 is connected via a pad electrode.
A voltage of 100 V was applied between a and 24b.

At this time, the SrT near the L-shaped electrode 24
The electric field formed in the iO ₃ film 23 has L-shaped electrodes 24a,
24b, not the distance between the strip conductors 22
a is determined by the distance (in this case, 20 μm) after subtracting the width of a, so that a strong electric field (in this case, 50 kV /
cm). As a result, the resonance frequency changed, and resonance occurred at a resonance frequency of 4.38 GHz.

(Fourth Embodiment) FIGS. 15 and 16 are a plan view and a sectional view showing a method for manufacturing a resonator according to a fourth embodiment of the present invention. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view.

First, as shown in FIG. 15, similarly to the first embodiment, a LaAl having a diameter of 30 mm and a thickness of 0.5 mm was used.
A thickness of 3 on each of the front and back surfaces of the O ₃ single crystal substrate 31
A 00 nm YBCO superconducting film 32 is formed. YBCO
The method of forming the superconducting film 32 is the same as in the first embodiment.

Next, as shown in FIG.
The superconducting film 32 is processed into a stripe shape and a comb shape to form comb electrodes 32a to 32d and a strip conductor 32e. The YBCO superconducting film 32 on the back surface is used as a ground plane.

The comb-shaped electrodes 32a and 32b are arranged so as to mesh with each other, and the pair of comb-shaped electrodes 32a and 32b are arranged beside the strip conductor 32e so as not to be in contact with the strip conductor 32e. The linear electrodes forming the comb electrodes 32a and 32b are arranged in parallel to the longitudinal direction of the strip conductor 32e. The comb electrodes 32c and 32d have the same configuration.

The width of the linear electrodes forming the comb electrodes 32a to 32d is 10 μm, and the interval between the linear electrodes is 10 μm. The distance between the strip conductor 32e and the closest linear electrode is 5 μm.

Finally, after a pad electrode (not shown) connected to each of the comb electrodes 32a to 32d is formed, a 1 μm thick SrTiO ₃ film (not shown) is formed on the entire surface, and a contact hole (not shown) for the pad electrode is formed. (Not shown), and a resonator having a resonance frequency of 4.3 GHz is completed.

When the Q value of the resonator thus formed was examined, a high value of 50,000 was obtained. Therefore, by using the resonator of the present embodiment, it is possible to realize a filter having excellent attenuation characteristics and small insertion loss. The reason why such a high Q value is obtained is that the comb-shaped electrodes 32a to 32d are arranged so as to avoid over the strip conductor 32a.

The same voltage is applied to the pad electrode 33a and the pad electrode 33d so that a potential difference occurs between the comb electrodes 24b and 24d closer to both sides of the strip conductor 32e. Also 50
V higher voltage is applied, and the pad electrode 3c is applied to the pad electrode 33c.
A voltage of 50 V higher than 3d was applied. At this time, a similar potential difference occurs between the comb-shaped electrodes 34b and 34d.

When the above voltage is applied, an electric field of 50 KV / cm is generated between the comb-shaped electrodes, and the dielectric constant of the SrTiO ₃ film changes. As a result, the resonance frequency increases by about 2.3% and resonates at 4.4 GHz.

Note that the comb-shaped electrode (YBCO superconducting film)
Since 2a to 32d are preferably thinner, the strip conductor 32e is formed before forming an SrTiO ₃ film (not shown) on the entire surface.
Is masked using a resist or metal mask,
The comb-shaped electrodes 32a to 32d have a thickness of 50 nm or less, preferably 10 nm or less.
It is more preferable that 2d be subjected to ion milling or sputter etching. Here, the sputter etching
For example, about 0.1 Torr to about 1.0 Torr of Ar
In the atmosphere, the LaAlO ₃ single crystal substrate 31
It is preferable to apply a high frequency power of 3.56 MHz to form Ar plasma.

Although the superconducting characteristics of the comb-shaped electrodes 32a to 32d which are thinly cut by these methods are deteriorated, the conductivity is not lost. In this state, the adverse effect on the electromagnetic field is small, which is convenient. That is, when the YBCO superconducting film is used as an electrode, it is preferable to degrade the superconducting characteristics and use a normal conducting material.

Further, as a base for forming the SrTiO ₃ film,
Such comb-like electrodes (YBCO superconducting films) 32a to 32
The use of d has the following advantages.

The SrTiO ₃ film is formed by sputtering, CV
D, and can be formed by a film forming method such as a laser vapor deposition method.
The LaAlO ₃ single crystal substrate 31 is heated from 300 ° C. to 700 ° C. in an oxygen atmosphere of about 10 Torr to about 10 Torr or less.
Heat to about ° C.

At this time, if there is a metal film on the LaAlO ₃ single crystal substrate 31, these are generally oxidized, or the thin metal film is aggregated into a spherical shape, resulting in a film in which the metal is scattered in an island shape. . The required function cannot be obtained because the conductivity of such a metal film is low.

However, the YBCO superconducting film is damaged by ion milling or the like, and does not lose its conductivity even if it is thinned or heated to the above temperature in an oxygen atmosphere. There is.

(Fifth Embodiment) FIGS. 17 to 19 are a plan view and a sectional view showing a method for manufacturing a resonator according to a fifth embodiment of the present invention. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view.

First, as shown in FIG.
After the YBCO superconducting films 42a and 42b having a thickness of 300 nm are formed on the front and back surfaces of the LaAlO ₃ single crystal substrate 41 having a thickness of 0.5 mm, the YBCO superconducting film 42a on the front surface is processed into a striped shape. 4
2a is formed. The YBCO superconducting film 42b on the back surface is used as a ground plane. YBCO superconducting film 42
The film forming methods a and b are the same as those in the first embodiment.

Next, as shown in FIG. 18, a 2 μm thick SrTiO ₃ film 43 is formed on the surface of the LaAlO ₃ single crystal substrate 41.
Is formed, the SrTiO ₃ film 43 is processed by lithography and etching to reach the substrate surface and form an electrode groove having a pitch of 10 μm and a width of 2 μm. That is, an electrode groove having the same pattern as the comb-shaped electrodes 44a to 44d to be formed in a later step is formed. The method of forming the SrTiO ₃ film 43 is the same as that of the YBCO superconducting film.

Next, as shown in FIG. 19, after a conductive film having a thickness of 10 nm to be the comb electrodes 44a to 44d is formed on the entire surface, the conductive film is subjected to chemical polishing, mechanical polishing, or chemical mechanical polishing. After grinding, the comb-like electrode 44a is placed in the electrode groove.
To 44d are buried.

The comb-shaped electrodes 42a and 42b are arranged so as to mesh with each other, and the pair of comb-shaped electrodes 42a and 42b are arranged beside the strip conductor 42a so as not to contact the strip conductor 42a. The linear electrodes forming the comb electrodes 42a and 42b are arranged in parallel with the longitudinal direction of the strip conductor 42a. The comb-shaped electrodes 42c and 42d have the same configuration.

The material of the conductive film to be the comb electrodes 42a to 42d is, for example, Au, Ag, Pt, C
electrode materials such as u, Al, and conductive ceramics. Further, instead of polishing, the conductive film may be removed by etching. For example, from 0.1 Torr to 1.
In an Ar atmosphere of about 0 Torr, LaAlO ₃
By applying 13.56 MHz high-frequency power to the single crystal substrate 41 to form Ar plasma, the conductive film on the surface can be removed.

When the conductive film is on the same plane, the entirety is removed by this method. However, in this embodiment, an electrode groove is formed on the substrate surface, and ions do not reach the bottom of the electrode groove. Only the surface of the film is shaved, not all.

Finally, similarly to the first embodiment, a pad electrode (not shown) is formed to complete the resonator.

In this embodiment, the comb-shaped electrodes 44a to 44d
Are formed directly on the surface of the LaAlO ₃ single crystal substrate 41, the following effects can be obtained.

Normally, the surface of the SrTiO ₃ film formed on a substrate such as the LaAlO ₃ single crystal substrate 41 has several tens to 10
Unevenness of about 0 nm is formed. When forming a conductive film to be the comb electrode 44a~44d such a SrTiO ₃ film, Where thin thickness of the conductive film, SrTiO ₃
Shredding occurs due to irregularities on the surface of the film.

As a result, a problem arises in that the conduction of the comb electrodes 44a to 44d cannot be sufficiently obtained. Resistivity 1
× 10 ^-1 ohm. cm or less, the thickness of the conductive film needs to be about 50 nm.

However, in this embodiment, a conductive film to be the comb-shaped electrodes 44a to 44d is directly formed on the surface of the LaAlO ₃ single crystal substrate 41 having a high surface flatness (roughness of at most several nm). Therefore, a smaller film thickness is required to obtain the same resistivity.

The smaller the thickness of the linear electrode near the YBCO superconducting film 42a, the higher the Q value. In the present embodiment, the thickness of the conductive film was 10 nm, and thereby a higher Q value (60000) was obtained. Therefore, by using the resonator of the present embodiment, it is possible to realize a filter having excellent attenuation characteristics and small insertion loss.

When no voltage is applied to the comb-shaped electrodes 44a to 44d, resonance occurs at 4.3 GHz. However, when a voltage of 100 V is applied to the comb-shaped electrodes 44a to 44d, the resonance frequency becomes 4. It changed to 38 GHz. Note that the magnitude relationship between the comb-shaped electrodes 44a to 44d when applying a voltage is the same as in the first embodiment.

(Sixth Embodiment) FIGS. 20 and 21 are a plan view and a sectional view showing a method for manufacturing a resonator according to a sixth embodiment of the present invention. (A) of each figure is a plan view, and (b) of each figure is a cross-sectional view taken along the line AA 'of the plan view.

First, as shown in FIG.
After the YBCO superconducting films 52a and 52b having a thickness of 300 nm are respectively formed on the front and back surfaces of the LaAlO ₃ single crystal substrate 51 having a thickness of 0.5 mm, the YBCO superconducting film 52a on the front surface is processed into a stripe shape and strip conductors are formed. 5
2a is formed. The YBCO superconducting film 52b on the back surface is used as a ground plane. YBCO superconducting film 52
The method for forming the films a and 52b is the same as in the first embodiment.

Next, as shown in FIG. 21, a 1 μm thick SrTiO ₃ film 53 is formed on the surface of the LaAlO ₃ single crystal substrate 51.
To form The method of forming the SrTiO ₃ film 53 is YBC
This is the same as that of the O superconducting films 52a and 52b.

[0111] Then, as shown in the figure, SrTiO ₃ film 5
After a conductive film having a thickness of 50 nm to be the comb-shaped electrodes 54a and 54b is formed on 3, the conductive film is processed by using lithography and etching to form the comb-shaped electrodes 54a and 54b that mesh with each other.

Here, the linear electrodes constituting the comb electrodes 54a and 54b are formed so as to be orthogonal to the strip conductor 52a. The length of the linear electrodes is 1 μm, the width is 10 μm, and the interval between the linear electrodes is 90 μm. Also,
As the material of the conductive film, for example, Au, Ag, P
Examples of the electrode material include t, Cu, Al, and conductive ceramics.

Finally, similarly to the first embodiment, a pad electrode is formed to complete the resonator. When the Q value of the resonator thus formed was examined, a high value of 50,000 was obtained. Therefore, by using the resonator of the present embodiment, it is possible to realize a filter having excellent attenuation characteristics and small insertion loss.

Further, a voltage of 200 between the comb electrodes 54a and 54b is set.
When a voltage of V was applied, the resonance frequency was 4.35 GHz.
Resonated.

The resonator of this embodiment was evaluated by comparing it with the following two resonators (Comparative Examples 1 and 2).

FIG. 22 is a plan view of the resonator of Comparative Example 1. FIG. 20 and FIG. 21 are denoted by the same reference numerals as those in FIG. 20 and FIG. 21, and detailed description is omitted.

The difference between the resonator of Comparative Example 1 and that of the present embodiment is the dimensions of the comb electrodes 54a and 54b. In the resonator of Comparative Example 1, the linear electrodes forming the comb electrodes 54a and 54b are different. Has a length of 10 μm, a width of 10 μm, and an interval between linear electrodes of 40 μm.

That is, although the area ratio of the comb-shaped electrodes 54a and 54b covering the strip conductor 52a is about 20%, of the comb-shaped electrodes 54a and 54b,
2a, which is perpendicular to the longitudinal direction and whose length is L ₀ /
For more than two linear electrodes, strip conductors 52a
The sum of the sum of the areas of the linear electrode present above the sum of the areas of the linear electrode present in distant regions to L _0/4 in a direction perpendicular to the longitudinal direction of the strip conductor 52a (Overall Area) is about 20% of (L _0/2 ) ² (less than 20% in the present embodiment). As a result, the Q value was about 80, which is much smaller than that of the present embodiment.

Comparative Example 2 FIG. 23 is a plan view of a resonator of Comparative Example 1. 20 and FIG. 21 are denoted by the same reference numerals as those in FIG. 20 and FIG. 21, and detailed description is omitted.

The difference between the resonator of Comparative Example 2 and that of the present embodiment is the dimensions of the comb electrodes 54a and 54b. In the resonator of Comparative Example 2, the linear electrodes forming the comb electrodes 54a and 54b are different. Has a length of 10 μm, a width of 10 μm, and an interval between the linear electrodes is 10 μm.

That is, although the comb-shaped electrodes 54a and 54b do not cross the strip conductor 52a, that is, the area ratio is zero, but the comb-shaped electrodes 54a and 54b are perpendicular to the longitudinal direction of the strip conductor 52a. and for the linear electrodes whose length exceeds L _0/2, L in a direction perpendicular to the longitudinal direction of the strip conductor 52a ₀ /
The sum of the area of the linear electrodes existing in the region up to 4
It is about 50% of (L _0/2 ) ² . As a result, the Q value was about 50, which is much smaller than that of the present embodiment.

(Seventh Embodiment) FIGS. 24A and 24B are a plan view and a sectional view showing a resonator according to a seventh embodiment of the present invention. FIG. 3A is a plan view, and FIG.
It is sectional drawing.

This will be described according to the manufacturing process.
A YBCO superconductor film 6 having a thickness of 300 nm is formed on the back surface of a first LaAlO ₃ substrate 61 having a diameter of 30 mm and a thickness of 0.1 mm.
2 is formed by a film formation method such as a sputtering method, a laser evaporation method, or a CVD method. YBCO superconductor film 6
2 is used as a ground plane.

Next, the thickness of the LaAlO ₃ substrate 61 is
μm SrTiO ₃ film 63, 50 nm thick Au, A
A conductive film 64 made of a metal such as g, Pt, Cu, or Al or a conductive ceramic is formed sequentially. SrTi
The method of forming the O ₃ film 63 and the conductive film 64 is the same as that of the YBCO superconductor film 62.

After forming the SrTiO ₃ film 63 and the conductive film 64, the YBCO superconductor film 62 may be formed.

On the other hand, a rectangular second LaAlO ₃ substrate 65 having a YBCO superconductor film (strip conductor) 66 having a thickness of 300 nm formed on the surface is prepared. This second L
a The dimensions of the AlO ₃ substrate 65 are 1 mm in width and 30 m in length.
m, thickness 0.4 mm.

Next, the conductive film 64 and the SrTiO ₃ film 63 formed on the first LaAlO ₃ substrate 61 are etched to form an electrode 64 having a rectangular shape formed of the conductive film 64 and the first LaAlO ₃ substrate. A groove reaching 61 is formed.

[0128] Finally, the second LaAlO ₃ substrate 65 in the groove embedding the second LaAlO ₃ substrate 65 first
A LaAlO ₃ substrate 61 and bonded using an epoxy adhesive, the resonator is completed.

At this time, the SrT
The iO ₃ film 63, the electrode 64, or both of them may remain, but from the viewpoint of preventing the deterioration of the resonance characteristics,
It is preferable to remove it using lithography.

In the resonator obtained in this manner, a power source is connected between the YBCO superconducting film 62 and the electrode 64 as shown in FIG.
The dielectric constant of the O ₃ film 63 can be changed. In this case, since a voltage is applied in the thickness direction, there is an advantage that the change in the dielectric constant is large and the resonance band is widened.

The electrode 64 is made of YBCO which determines the resonance frequency.
Next to the superconducting film 66, that is, the second LaAlO ₃ substrate 65
And if the distance d between them is short, a wide variable range can be obtained with a low voltage, but the Q value tends to decrease. on the other hand,
If the distance d is long, the Q value does not decrease much, but a high voltage is required to obtain a wide variable range.

If the area S _{2 of the} region where the electrode 64 is provided is large, a wide variable range can be obtained with a low voltage.
The value tends to decrease. On the other hand, the reduction of narrow and Q value area S ₂ smaller, it requires a higher voltage to obtain a wide variable range.

FIG. 25 and FIG. 26 show these relationships. FIG. 25 is a characteristic diagram illustrating the dependence of the Q value and the distance d of the variable band. FIG. 26 is a characteristic diagram showing the dependency of the Q value and the area ratio of the variable band (S ₂ / S ₁ ). Here, S ₁ is the area of the YBCO superconducting film 66.

From FIG. 25, it can be seen that the distance d is required to be 10 μm or more (the minimum distance required for insulation) and 5 mm or less, preferably 50 μm or more and 1 mm or less. From FIG. 26, the area ratio is 0.5 times or more and 100 times or less,
It is understood that the ratio is preferably 1.0 times or more and 50 times or less.

By the way, the YBCO superconducting film 62 and the electrode 6
In order to lower the voltage applied between the first AlAlO ₃ substrate 4 and the electric field in the SrTiO ₃ film 63, it is necessary to reduce the thickness of the first LaAlO ₃ substrate 61 as much as possible.

In this case, the mechanical strength is weakened, so that the whole is molded with a resin, or a material having high insulation properties and low dielectric loss, for example, La on either or both surfaces is used.
It is desired to adhere a support made of a material such as AlO ₃ , YAlO ₃ , Al ₂ O ₃ . However, the material used at this time does not necessarily have to be a single crystal.

The resonator according to the present embodiment has a fundamental frequency of 1.5 G
Hz for mobile communication base station filters,
It was confirmed that even if 100 or more channels were provided in a 100 MHz bandwidth, communication without crosstalk could be performed.

(Eighth Embodiment) FIG. 27 is a plan view and a sectional view showing a resonator according to an eighth embodiment of the present invention. FIG. 3A is a plan view, and FIG.
It is sectional drawing. Note that parts corresponding to the resonators in FIG. 24 are denoted by the same reference numerals as in FIG. 24, and detailed descriptions thereof will be omitted.

This embodiment is different from the seventh embodiment in the shape of the electrode 64. That is, in the first embodiment, the shape of the electrode 64 is planar (rectangular), but in the present embodiment, the electrode 64 is comb-shaped composed of a plurality of fine wires (linear electrodes 64a). This is preferable because the deterioration of the resonance characteristics is small.

Further, the linear electrode 64a constituting the electrode 64
Is 0.5 mm, and the distance between the linear electrodes 64a is 1 mm. In this case, the area ratio (the area of the electrode 64 / the area of the YBCO superconducting film 66) is about 35%.

Table 1 shows the area ratio (area of electrode 64 / area of YBCO superconducting film 66) in the resonator shown in FIG.
And the relationship between the Q value.

Table 1 Area ratio 0.5% 1% 5% 10% 20% 30% 50% Q value 80000 70000 40000 30000 20000 15000 10000 Area ratio 60% 70% 80% 90% 100% Q value 6000 2000 1000 500 300 Table From 1 it can be seen that the area ratio is desirably 50% or less, preferably 10% or less.

Table 2 shows the relationship between the area ratio and the variable width. The applied voltage is 100V.

Table 2 Area ratio 0.5% 1% 5% 10% 20% 30% 50% Variable width 1 20 50 60 80 100 150 (MHz) Area ratio 60% 70% 80% 90% 100% Variable width 200 250 300 350 400 (MHz) From Table 2, the larger the area ratio, the lower the voltage of SrTiO ₃
It can be seen that the dielectric constant of the film 63 can be greatly changed, and the variable width of the resonance frequency can be widened.

According to these results, the area ratio was 1% or more and 60% or more.
%, Preferably 5% or more and 20% or less.

Further, by using the resonator of this embodiment as a filter for a mobile communication base station having a fundamental frequency of 1.5 GHz, communication without crosstalk can be performed even when 200 or more channels are provided in a 100 MHz bandwidth. I confirmed that I could do it.

FIG. 28 shows a modification of this embodiment. This is because the conductive film serving as the electrode 64 is etched and the exposed S
A second LaAlO ₃ substrate 65 is provided on the surface of the rTiO ₃ film 63.
Is adhered.

In this case, the following effects can be obtained.

When a voltage is applied between the YBCO superconducting film 62 and the conductive film 64, a voltage is also applied to the SrTiO ₃ film 63 under the second LaAlO ₃ substrate 65, and the dielectric constant changes. Since the change in the dielectric constant in this region greatly affects the change in the resonance frequency, it is suitable for widening the variable width.

Incidentally, such a modification can be applied to the seventh embodiment, and a similar effect can be obtained. Also, this embodiment can be variously modified similarly to the seventh embodiment.

(Ninth Embodiment) FIG. 29 is a plan view and a sectional view showing a resonator according to a ninth embodiment of the present invention. FIG. 3A is a plan view, and FIG.
It is sectional drawing.

This will be described in accordance with the manufacturing process.
On a surface of a first LaAlO ₃ substrate 71 having a diameter of 30 mm and a thickness of 0.5 mm, a YBCO superconductor film 72 having a thickness of 300 nm, an SrTiO ₃ film 73 having a thickness of 1 μm, and a thickness of 50 nm
A conductive film 74 made of a metal such as Au, Ag, Pt, Cu, or Al, or a conductive ceramic is sequentially formed. The YBCO superconductor film 72 is used as a ground plane.

On the other hand, a rectangular second LaAlO ₃ having a YBCO superconductor film 76 having a thickness of 300 nm formed on the surface thereof
A substrate 75 is prepared. This second LaAlO ₃ substrate 75
Are 1 mm in width, 30 mm in length, and 0.4 mm in thickness.

Next, the conductive film 74 and the SrTiO ₃ film 73 formed on the first LaAlO ₃ substrate 71 are etched to form a rectangular electrode formed of the conductive film 74 and reach the YBCO superconductor film 72. Form a groove.

Finally, a second LaAlO ₃ substrate 75 is buried in the groove, and the YBCO superconductor film 72 and the first L
The resonator is completed by bonding the aAlO ₃ substrate 71 with an epoxy-based adhesive.

At this time, in order to reduce the deterioration of the resonance characteristics, it is necessary to remove the conductive film 74 remaining at the bottom of the groove as the bonding surface by using lithography.

In order to reduce the deterioration of the resonance characteristics, it is preferable that the SrTiO ₃ film 73 does not remain at the bottom of the groove. However, the SrTiO ₃ film 73
YBCO superconductor film 72 and first LaAlO ₃ substrate 71
It is not necessary to remove the YBCO superconductor film 72 because it also has a role of protecting the YBCO superconductor film 72 from being scratched when it is bonded. However, the SrTiO in the area to connect the power supply
_{The three} films 73 need to be removed.

In the thus obtained resonator, a power supply is connected between the YBCO superconducting film 72 and the electrode 74 as shown in FIG.
The dielectric constant of the O ₃ film 73 can be changed.

Also in this case, as in the seventh embodiment, since a voltage is applied in the film thickness direction, there is an advantage that the change in the dielectric constant is large and the resonance band is widened.

In this embodiment, the first LaAlO ₃ substrate 71 is provided between the YBCO superconducting film 72 and the electrode 74.
Does not exist, the electric field of the SrTiO ₃ film 73 can be increased even at a lower voltage than in the seventh embodiment.
This makes it possible to change the resonance frequency with a power supply having a small capacity.

Further, by using the resonator of this embodiment as a filter for a mobile communication base station having a fundamental frequency of 1.5 GHz, communication without crosstalk can be performed even when 100 or more channels are provided in a 100 MHz bandwidth. I confirmed that I could do it.

(Tenth Embodiment) FIG. 30 is a plan view and a sectional view showing a resonator according to a tenth embodiment of the present invention. FIG. 3A is a plan view, and FIG.
It is sectional drawing. Note that parts corresponding to the resonators in FIG. 29 are denoted by the same reference numerals as in FIG. 29, and detailed description will be omitted.

The present embodiment differs from the ninth embodiment in the shape of the electrode 74. That is, in the eighth embodiment, the shape of the electrode 74 is planar (rectangular), but in the present embodiment, the electrode 74 is comb-shaped composed of a plurality of fine wires (linear electrodes 74a).

Here, the linear electrode 74 constituting the electrode 74
The width of a is 0.5 mm, and the distance (pitch) between the linear electrodes 74a is 1 mm. In this case, the area ratio (the area of the electrode 74 / the area of the YBCO superconducting film 76) is about 35%.

In this embodiment, the same effects as those of the ninth embodiment can be obtained. However, in the present embodiment, since the shape of the electrode 74 is comb-shaped, the deterioration of the resonance characteristics is further reduced.
The effect is higher.

Further, by using the resonator of the present embodiment as a filter for a mobile communication base station having a fundamental frequency of 1.5 GHz, communication without crosstalk can be performed even when 150 or more channels are provided in a 100 MHz bandwidth. I confirmed that I could do it.

FIG. 31 shows a modification of the present embodiment. This is because the conductive film serving as the electrode 74 is etched and exposed S
A second LaAlO ₃ substrate 55 is provided on the surface of the rTiO ₃ film 73.
Is adhered.

To reduce the deterioration of the resonance characteristics, S
It is preferable that the rTiO ₃ film 73 also does not remain at the bottom of the groove. However, the SrTiO ₃ film 73 also has a function of protecting the YBCO superconductor film 72 from being damaged when the YBCO superconductor film 76 is provided on the first LaAlO ₃ substrate 71, as shown in FIG. However, it is not necessary to remove it.

This embodiment can be variously modified in the same manner as the seventh embodiment.

Note that the present invention is not limited to the above embodiment. For example, the substrate material is not limited to LaAlO _3.
Low dielectric constant materials such as 10 ₃ , MgO, and sapphire can be used.

The superconducting film is not limited to the YBCO film, but may be any oxide superconducting film.

The dielectric material is not limited to SrTiO ₃ , but may be any material as long as its dielectric constant changes when an electric field is applied. For example, BaxSr1-xTiO ₃ (x is based on SrTiO ₃ or BaTiO ₃₎ 0 to 1) and PSZT.

The structure of the resonator is not limited to the microstrip line structure. Other structures include, for example, a coplanar waveguide structure, a strip line structure, a suspended line structure, and a slot line structure. .

FIG. 32 is a perspective view of a resonator having a coplanar waveguide structure. This has a fixed resonance frequency. FIG. 33 is a perspective view of a resonator having a coplanar waveguide structure to which the present invention is applied. This can change the resonance frequency. In the figure, 81 is a substrate, 82 is a superconducting strip conductor, 83 is a ground plane, 84 is a dielectric film, and 85 is an electrode satisfying the conditions of the present invention.

As shown in FIGS. 34 and 35, the second
The width of the LaAlO ₃ substrate 75 of Y
The width may be different from the width of the BCO superconductor film 76, and may be 100 times or less, preferably 10 times or less the width of the line forming the resonator. Above this, the power supply for power supply for changing the dielectric constant of the dielectric is undesirably separated from the stripline resonator and the variable width becomes narrow.

For example, when a 0.1 mm line is formed on a substrate having a width of 1 mm, a bandwidth of about 90 MHz can be obtained from the data shown in FIG. The same applies to the case where a line having a width of 0.01 mm is formed on a substrate having a width of 1 mm.

However, it is not preferable to form a substrate having a width of 2 mm or more, since the bandwidth is reduced to 10 MHz or less.
However, as shown in FIG. 36, when the conductive film 74 is provided under the second LaAlO ₃ substrate 75, the width of the substrate is not limited. However, it is necessary to remove the conductive film 74 immediately below the YBCO superconductor film 76 and in the vicinity thereof. It is desirable that the width be at least 5 times, preferably at least 50 times, the width of the line forming the resonator, since the deterioration of the Q value is small.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0179]

As described above in detail, according to the present invention, a superconducting resonance element in which a strip conductor made of a superconductor is provided on a substrate, and a ground is provided on or under the substrate, Provided, in a superconducting element having a dielectric member whose permittivity changes according to an applied voltage, and an electrode for applying a voltage to the dielectric member,
By setting the electrode and the strip conductor so as to satisfy a predetermined relationship, the Q value of the superconducting resonance element can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing the structure of a microstrip resonator.

FIG. 2 is a diagram showing an electric field due to a high-frequency signal flowing through a microstrip resonator.

FIG. 3 is a diagram showing a relationship between an area ratio (S / S ₀ ) and a Q value.

FIG. 4 is a diagram showing a relationship between a length L and a Q value.

FIG. 5 is a plan view showing a resonator in which a linear electrode and a strip conductor intersect.

FIG. 6 is a plan view showing a resonator in which a linear electrode and a strip conductor do not intersect.

FIG. 7 is a diagram showing a region away from the strip conductor in a direction perpendicular to its longitudinal direction to L _0/4 .

FIG. 8 is a plan view showing a resonator in which a comb electrode and a strip conductor do not intersect.

FIG. 9 is a plan view and a cross-sectional view illustrating a method of manufacturing the resonator according to the first embodiment of the present invention.

FIGS. 10A and 10B are a plan view and a cross-sectional view illustrating the method of manufacturing the resonator according to the first embodiment of the invention.

FIG. 11 is a plan view and a cross-sectional view illustrating a method of manufacturing a resonator according to a second embodiment of the present invention.

FIG. 12 is a plan view and a cross-sectional view illustrating a method of manufacturing a resonator according to the second embodiment of the present invention.

FIG. 13 is a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to the third embodiment of the present invention.

14A and 14B are a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to the third embodiment of the present invention.

FIG. 15 is a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to a fourth embodiment of the present invention.

FIG. 16 is a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to a fourth embodiment of the present invention.

17A and 17B are a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to a fifth embodiment of the present invention.

FIGS. 18A and 18B are a plan view and a cross-sectional view illustrating a method of manufacturing a resonator according to a fifth embodiment.

FIG. 19 is a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to a fifth embodiment of the present invention.

FIG. 20 is a plan view and a cross-sectional view illustrating a method for manufacturing a resonator according to the sixth embodiment of the present invention.

FIG. 21 is a plan view and a cross-sectional view illustrating a method of manufacturing a resonator according to a sixth embodiment of the present invention.

FIG. 22 is a plan view showing the resonator of Comparative Example 1.

FIG. 23 is a plan view showing the resonator of Comparative Example 1.

FIG. 24 is a plan view and a sectional view showing a resonator according to a seventh embodiment of the present invention.

FIG. 25 is a characteristic diagram showing the dependency of the Q value and the distance d of the variable band.

FIG. 26 is a characteristic diagram showing the dependence of the value and the area ratio of the variable band (S ₂ / S ₁ ).

FIG. 27 is a plan view and a sectional view showing a resonator according to an eighth embodiment of the present invention.

FIG. 28 is a plan view and a cross-sectional view showing a modification of the resonator according to the eighth embodiment.

FIG. 29 is a plan view and a sectional view showing a resonator according to a ninth embodiment of the present invention.

FIG. 30 is a plan view and a sectional view showing a resonator according to a tenth embodiment of the present invention.

FIG. 31 is a plan view and a cross-sectional view showing a modification of the resonator according to the tenth embodiment.

FIG. 32 is a perspective view showing a resonator having a coplanar waveguide structure (fixed resonance frequency).

FIG. 33 is a perspective view showing a resonator having a coplanar waveguide structure (variable resonance frequency).

FIG. 34 is a plan view and a sectional view showing a resonator according to a modification of the present invention.

FIG. 35 is a plan view and a sectional view showing a resonator according to another modification of the present invention.

FIG. 36 is a plan view and a sectional view showing a resonator according to yet another modification of the present invention.

[Explanation of symbols]

1 ... substrate 2 ... strip conductors 3 ... ground plane 4 ... conductive film 5 ... linear electrodes 6 a to 6 d ... comb-shaped electrodes 11 ... LaAlO ₃ single crystal substrate 12a ... YBCO superconducting film (strip conductors) 12b ... YBCO superconducting film (ground plane) 13 ... SrTiO ₃ film (dielectric member) 14a to 14d ... comb-shaped electrodes 15 a to 15 d ... pad electrodes 21 ... LaAlO ₃ single crystal substrate 22a ... YBCO superconducting film (strip conductors) 22b ... YBCO superconducting film (ground plane) 23: SrTiO ₃ film (dielectric member) 24a, 24b: L-shaped electrode 31: LaAlO ₃ single crystal substrate 32: YBCO superconducting film (ground plane) 32a to 32d: YBCO superconducting film (comb-shaped electrode) 32e: YBCO superconducting Films (strip conductors) 33a to 33d: pad electrodes 41: LaA O ₃ single crystal substrate 42a ... YBCO superconducting film (strip conductors) 42b ... YBCO superconducting film (ground plane) 43 ... SrTiO ₃ film (dielectric member) 44 a to 44 d ... comb-shaped electrodes 51 ... LaAlO ₃ single crystal substrate 52a ... YBCO superconducting film (strip conductors) 52 b ... YBCO superconducting film (ground plane) 53 ... SrTiO ₃ film (dielectric member) 54a, 54b ... comb-shaped electrodes 61 ... LaAlO ₃ substrate 62 ... YBCO superconducting film (ground plane) 63 ... SrTiO ₃ Film (dielectric member) 64 Conductive film (electrode) 65 LaAlO ₃ substrate 66 YBCO superconductor film (strip conductor) 71 LaAlO ₃ substrate 72 YBCO superconducting film (ground plane) 73 SrTiO ₃ film (dielectric) member) 74 ... conductive film (electrode) 75 ... LaAlO ₃ substrate 76 ... BCO superconductor film (strip conductors)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuki Kudo 1st address, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside of Toshiba Research & Development Center Co., Ltd. No. 1 town Toshiba R & D Center

Claims (5)

[Claims] 1. A superconducting resonance element in which a strip conductor made of a superconductor is provided on a substrate, and a ground is provided on or below the substrate. A superconducting element comprising a variable dielectric member and an electrode for applying a voltage to the dielectric member, wherein a region where the strip conductor and the electrode overlap when viewed from above the element. Is less than 20% of the area of the strip conductor. 2. A length (hereinafter, referred to as L ₀ ) of a wavelength of the electrode, which is perpendicular to a longitudinal direction of the strip conductor and corresponds to a resonance frequency of the superconducting resonance element.
For those exceeding 2, the width is L _0/2, respectively.
10% or less, and the total area of the elements present on the strip conductor when viewed from above the element, and the area perpendicular to the longitudinal direction of the strip conductor to L _0/4 . 2. The superconducting element according to claim 1, wherein the sum of the total area of the elements existing in the superconductor is not more than 20% of (L _0/2 ) ² . 3. The electrode according to claim 1, wherein the electrode comprises a plurality of linear electrodes intersecting the strip conductor in a direction perpendicular to a longitudinal direction of the strip conductor.
3. The superconducting element according to claim 1. 4. The electrode has two pairs of comb-shaped electrodes arranged so as to mesh with each other, and the linear electrodes forming the teeth of the comb-shaped electrodes are arranged in the longitudinal direction of the strip conductor. The pair of comb-shaped electrodes are arranged on each of both sides of the strip conductor so as not to be in contact with the strip conductor. 3. The superconducting element according to claim 1. 5. A superconducting resonance element comprising: a first substrate; a ground provided on the first substrate; and a strip conductor composed of a superconductor provided on the ground via a second substrate. A dielectric member provided on the superconducting resonance element so as not to be in contact with the second substrate and the strip, and having a dielectric constant that changes according to an applied voltage; and for applying a voltage to the dielectric member. ,
A superconducting element comprising: the second substrate and an electrode not in contact with the strip.