JP2959439B2 - Method of forming multilayer high-temperature superconducting integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a method for forming a multilayer high-temperature superconducting integrated circuit, about the particular method of forming the high temperature superconducting integrated circuit using three or more high temperature superconducting film.

[0002]

2. Description of the Related Art Hitherto, a multilayer high-temperature superconducting integrated circuit in which a multi-layer high-temperature superconducting film and an insulating film are laminated has been known (for example, Applied Physics Letters, No. 59).
Vol., P. 3051 (1991)). FIG. 3 is a cross-sectional view illustrating a conventional method for forming a high-temperature superconducting integrated circuit including three layers of a high-temperature superconducting film and two layers of an insulating film.

In this conventional forming method, first, FIG.
As shown in FIG. 1A, after the first high-temperature superconducting film 11 is epitaxially grown on the substrate 10, the high-temperature superconducting film 11 is processed. The epitaxial growth of the high-temperature superconducting film or the insulating film is performed by a laser deposition method. Processing is performed using ion beam etching after forming a pattern with a photoresist. After processing, the photoresist is stripped using acetone. The method of epitaxial growth and processing is the same in the following processes.

Subsequently, as shown in FIG. 3B, a first insulating film 12 is grown on the processed first high-temperature superconducting film 11, and processing for forming a contact hole is performed. Subsequently, as shown in FIG. 3C, a second high-temperature superconducting film 13 and a second insulating film 14 are continuously epitaxially grown on the first insulating film 12 and then processed. By this step, the first high-temperature superconducting film 11 and the second high-temperature superconducting film 13 are connected.

[0005] The second high-temperature superconducting film 13 and the second insulating film 1
4 may be grown separately by epitaxial growth.
As shown in (c), when the patterns are the same, epitaxial growth can be performed continuously. Finally, FIG.
As shown in (d), processing is performed after the third high-temperature superconducting film 15 is epitaxially grown. Second high-temperature superconducting film 1
3 and the third high-temperature superconducting film 15
3 are connected at the edge portion 13a.

[0006]

The high-temperature superconducting film and the insulating film used in the high-temperature superconducting integrated circuit must be epitaxially grown on a lattice-matched substrate. The quality of a thin film epitaxially grown remarkably depends on the state of the substrate surface. For this reason, if the state of the substrate surface is not good,
The superconducting characteristics of the high-temperature superconducting film and the insulating characteristics of the insulating film are degraded, causing a fatal defect in circuit operation. In the case of an integrated circuit having a multilayer structure as shown in FIG. 3, an upper layer film is epitaxially grown on a lower high-temperature superconducting film or an insulating film. The high-temperature superconductor is at least a quaternary oxide, and its surface is easily affected by elimination of oxygen or the like.
In addition, it is easily affected by moisture and the like, and the epitaxial property is easily deteriorated due to surface damage in the processing step.

[0007] Since the crystal structure itself of the film having a deteriorated epitaxial property is disturbed, the epitaxial growth on the film having the deteriorated epitaxial property is more difficult than the epitaxial growth on the film having only the deteriorated surface. The disorder of crystallinity is further increased. Therefore, the effect of the disorder of the epitaxial property is accumulated as the number of layers increases.

[0010] In the conventional forming method shown in FIG. 3, a processing process is performed every time a substantially single layer is formed in order to connect the first high-temperature superconducting film 11 and the second high-temperature superconducting film 13. It is carried out. For this reason, the surface of each layer deteriorates, and the influence of the disorder of the epitaxial property increases toward the upper layer,
The degree of deterioration of the superconducting characteristics of the high-temperature superconducting film and the insulating characteristics of the insulating film increases. Therefore, it is difficult to form a multilayer high-temperature superconducting integrated circuit having excellent characteristics by the conventional forming method shown in FIG.

The present invention has been made in view of the above points, and has three or more layers of a high-temperature superconducting film having excellent superconductivity and an insulating film having excellent insulating properties while maintaining excellent epitaxial properties up to the upper layer. Method of forming multilayer high-temperature superconducting integrated circuit including at least structure consisting of superconducting film and two or more insulating films
Law aims to provide a Hisage.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a first method in which two or more high-temperature superconducting films and two or more insulating films are successively epitaxially grown on a substrate in the same vacuum. And a second step of performing a predetermined process on the film epitaxially grown, and a third step of epitaxially growing the uppermost high-temperature superconducting film on the film processed by the second step, A contact hole for the connection between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film using the uppermost high-temperature superconducting film and the connection between the lower high-temperature superconducting films is formed by the second step. It is to be formed.

In order to achieve the above object, the present invention provides a first step in which two or more high-temperature superconducting films and one or more insulating films are alternately epitaxially grown on a substrate in the same vacuum. A second step of subjecting the film formed by the continuous epitaxial growth to predetermined processing, a third step of epitaxially growing an insulating film immediately below the uppermost high-temperature superconducting film on the film processed by the second step, At least a fourth step of subjecting the insulating film immediately below the upper high-temperature superconducting film to a desired processing, and a fifth step of epitaxially growing the uppermost high-temperature superconducting film on the film having undergone the fourth step Contact holes for connection between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film using the uppermost high-temperature superconducting film and for connecting the lower high-temperature superconducting films to each other; In the process of It is a thing.

[0012]

In the present invention, except for the uppermost high-temperature superconducting film, another high-temperature superconducting film and an insulating film are continuously epitaxially grown on the substrate in the same vacuum. When continuous epitaxial growth is performed in the same vacuum, the next layer is epitaxially grown while maintaining the crystal structure of each layer surface, so that a film having excellent epitaxial properties is formed, and the superconducting properties and insulation of the high-temperature superconducting film are obtained. The degree of deterioration of the insulating properties of the film is small.

After processing the multilayer epitaxial film a plurality of times, the uppermost high-temperature superconducting film is epitaxially grown. Since the upper layer of the high-temperature superconducting film is a film that has been subjected to a plurality of processes, the crystallinity of the surface is slightly degraded, but this film is a film that has been continuously epitaxially grown. The crystallinity of the film itself is good. For this reason, the synergistic effect of the disorder of the epitaxial property, which is a problem in the conventional formation method, does not occur, and the superconducting property of the uppermost high-temperature superconducting film can be kept relatively good.

Although the lower high-temperature superconducting film of the present invention cannot be directly connected to each other, in the present invention, the contact hole is formed in the second step so that the uppermost high-temperature superconducting film and the lower high-temperature superconducting film are not connected. By performing the connection between the high-temperature superconducting films, the lower high-temperature superconducting films can be connected to each other via the uppermost high-temperature superconducting film.

According to the first aspect of the present invention, a structure in which the lower high-temperature superconducting film and the uppermost high-temperature superconducting film intersect without leak current cannot be realized. Therefore, in the invention according to claim 4, the film that is continuously epitaxially grown in the same vacuum is a film excluding the uppermost high-temperature superconducting film and the insulating film immediately thereunder, thereby forming a lower-layer high-temperature superconducting film as the insulating film. And covering the portion including the pattern edge of the above, and maintaining insulation between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film disposed thereon.

The connection between the uppermost high-temperature superconducting film and the lower-layer high-temperature superconducting film is made by contact holes only.
Alternatively, it can be performed only with an edge having an inclined surface, or a combination of both.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional process diagram of a high-temperature superconducting integrated circuit having an edge junction for explaining a first embodiment of the present invention. To explain the first embodiment of the present invention together with FIG. 1, first, as shown in FIG. 1A, strontium titanate (SrTiO ₃ , hereinafter “STO”)
Yttrium / barium / copper oxide on a substrate 20 composed of

[0019]

[Outside 1] A first high-temperature superconducting film 21 made of
The first insulating film 22 made of STO is formed to a thickness of 200 nm,
The thickness of the second high-temperature superconducting film made of YBCO 23 is 200 n.
m, the thickness of the second insulating film 24 made of STO is 200 n
The layers are sequentially deposited by using the laser deposition method at m.

The films 21 to 24 are formed continuously in the same vacuum without breaking the vacuum. The substrate temperature during this film formation is 700 ° C. and the oxygen pressure is 27 Pa. In this same vacuum, a film having good crystallinity and good characteristics can be grown up to the upper layer by continuous film formation.

Subsequently, after patterning is performed on these films using a positive photoresist, processing using an ion beam etching apparatus is performed to form a first high-temperature superconducting film 21 and a first insulating film 22. Then, the second high-temperature superconducting film 23 and the second insulating film 24 are continuously processed, and after the completion of the ion beam etching, the photoresist is removed using acetone and oxygen ashing is performed, as shown in FIG. Groove 25 is formed as described above.

Subsequently, after patterning using a photoresist, the second insulating film 1 is formed by ion beam etching.
4 is performed, and after the processing, the photoresist is removed by acetone and oxygen ashing to form the inclined portion 26 in the second insulating film 14 as shown in FIG. 1C.

Next, after patterning using a photoresist, the second insulating film 2 is formed by ion beam etching.
4. Continuous processing of the second high-temperature superconducting film 23, and FIG.
As shown in FIG. 7, the edge 27 of the second high-temperature superconducting film 23 used for edge bonding is exposed. At this time, if the portion where the second insulating film 24 has been processed in the step of FIG. 1C is not covered with the photoresist, as shown in FIG. The film 23 and the first insulating film 22 are continuously processed to form a first contact hole 28 for the first high-temperature superconducting film 21. On the other hand, in the portion where the second insulating film 24 has been processed in FIG. 1C covered with the photoresist, a second contact hole 29 for the second high-temperature superconducting film 23 is formed. Thereafter, the photoresist is stripped.

Subsequently, the tunnel barrier 30 of the edge junction is used.
Praseodymium / barium / copper oxide

[0025]

[Outside 2] Is formed to a thickness of 20 nm, and YBCO is formed as a third high-temperature superconducting film 31 of the uppermost layer by a laser evaporation method under the conditions of a substrate temperature of 700 ° C. and an oxygen pressure of 27 Pa, respectively.

Thereafter, patterning with a photoresist, processing by ion beam etching, and stripping of the photoresist with acetone are performed to complete the structure shown in FIG.

The two layers of the high-temperature superconducting film shown in FIG.
Since the four epitaxial films including the two insulating films are continuously formed in the same vacuum, the second epitaxial film is formed last.
The good epitaxial property is maintained up to the insulating film 24. At the end of the forming method, as shown in FIG. 1E, a third high-temperature superconducting film 31 to be the uppermost high-temperature superconducting film is epitaxially grown on the processed continuous epitaxial film. However, the epitaxial property of the third high-temperature superconducting film 31 is slightly deteriorated due to disorder of crystallinity caused by processing of the surface of the underlying continuous epitaxial film.

However, the degree of this deterioration is determined by the conventional method of forming a multilayer superconducting integrated circuit described with reference to FIG.
It is much smaller than when epitaxial growth is performed after processing each layer. For this reason, the superconductivity of the third high-temperature superconducting film 31 is relatively good, and sufficiently satisfies the conditions as a component of the high-temperature superconducting integrated circuit.

As shown in FIG. 1E, the third high-temperature superconducting film 31 and the first high-temperature superconducting film 21 are provided in the first contact hole 28 and in the third high-temperature superconducting film 31.
And the second high-temperature superconducting film 23 are formed in the second contact hole 2.
9 and the edge joint 27. In addition, the first high-temperature superconducting film 21 and the second high-temperature superconducting film 23 are formed, for example, with first and second contact holes 28,
At 29, the connection is made via the third high-temperature superconducting film 31 by being connected to the third high-temperature superconducting film 31.

Further, the separated first high-temperature superconducting film 21
Alternatively, the second high-temperature superconducting films 23 can be connected to each other via the third high-temperature superconducting film 31 using contact holes. As described above, when the formation method according to the embodiment shown in FIG. 1 is used, the connection between the high-temperature superconducting films in the same layer and the connection between the high-temperature superconducting films in different layers is performed by forming the uppermost high-temperature superconducting film. It can be performed using:

As described above, in this embodiment, a high-temperature superconducting film having excellent superconducting properties and an insulating film having excellent insulating properties can be obtained up to the uppermost layer. Further, a multilayer high-temperature superconducting integrated circuit in which high-temperature superconducting films in the same layer or between different layers are connected to each other can be formed.

In the embodiment of the present invention, the processing of the continuous epitaxial film is performed as shown in FIGS. 1 (b), 1 (c) and 1 (d).
Are performed in the order of (c), (c), (d) and (b) in FIG. Also, the case of three high-temperature superconducting films and two insulating films has been described, but when the number of layers further increases, the film excluding the uppermost high-temperature superconducting film is similarly placed on the substrate in the same vacuum. The same effect as in the above-described embodiment can be obtained by continuous epitaxial growth.

Next, a second embodiment of the present invention will be described with reference to a sectional process diagram of the high-temperature superconducting integrated circuit shown in FIG. First, as shown in FIG. 2A, a first high-temperature superconducting film 21 made of YBCO is formed on a substrate 20 made of STO.
With a thickness of 200 nm, the first insulating film 22 made of STO with a thickness of 200 nm, and the second high-temperature superconducting film 23 made of YBCO with a thickness of 200 nm, respectively, using a laser deposition method. To form a film. These films 21 and 2
The film formation of No. 3 is performed continuously in the same vacuum without breaking the vacuum. The substrate temperature during film formation was 700 ° C. and the oxygen pressure was 2
7 Pa. In this same vacuum, a film having good crystallinity and good characteristics can be grown up to the upper layer by continuous film formation.

After patterning using a positive photoresist on these films, processing using an ion beam etching apparatus is performed, and the first high-temperature superconducting film 21, the first insulating film 22, and the second Is continuously processed. After the ion beam etching is completed, the photoresist is stripped using acetone and oxygen ashing is performed to form a groove 33 in the vertical direction as shown in FIG.

Subsequently, after patterning is again performed using a photoresist, ion beam etching is performed.
The second high-temperature superconducting film 23 is processed. After the processing, the photoresist is removed by acetone and oxygen ashing, so that the trapezoidally processed second high-temperature superconducting film 23 is left as shown in FIG.

Subsequently, after patterning is again performed using a photoresist, ion beam etching is performed.
The first insulating film 22 is processed. Thereafter, by peeling the photoresist, a contact hole 34 exposing the first high-temperature superconducting film 21 is formed in the first insulating film 22 as shown in FIG.

Next, as the second insulating film 35, which is the uppermost insulating film for directly converting the high-temperature superconducting film, STO is applied at a substrate temperature of 700.
A film is formed to a thickness of 200 nm by a laser vapor deposition method at a temperature of 27 ° C. and an oxygen pressure of 27 Pa, and steps of patterning, processing, and photoresist peeling are performed to form an insulating film 35 having a shape as shown in FIG. The contact hole 3 exposing the second high-temperature superconducting film 23 is formed in one of the second insulating films 35.
6 are formed.

Finally, the third layer, which is the uppermost high-temperature superconducting film,
YBCO at a substrate temperature of 700
A film having a thickness of 400 nm is formed by a laser deposition method at a temperature of 27 ° C. and an oxygen pressure of 27 Pa, and steps of patterning, processing, and photoresist peeling are performed to complete a structure having a shape as shown in FIG.

The two layers of the high-temperature superconducting film shown in FIG.
Three epitaxial films 21 to 2 in total including one insulating film
Since No. 3 is continuously formed in the same vacuum, good epitaxialness is maintained up to the second high-temperature superconducting film 23 formed last. Subsequently, in this example, FIG.
As shown in (f), on the processed continuous epitaxial film, the second insulating film 35, which is an insulating film immediately below the uppermost high-temperature superconducting film, A third high-temperature superconducting film 37 serving as a superconducting film is epitaxially grown.

At this time, the epitaxialness of the second insulating film 35 is slightly deteriorated due to disorder in crystallinity caused by processing the surface of the underlying continuous epitaxial film. In addition, due to the disorder of the surface of the continuous epitaxial film, the deterioration of the epitaxial property of the second insulating film 35, and the disorder of the crystallinity of the surface of the second insulating film 35, the epitaxial property of the third high-temperature superconducting film 37 is further reduced. to degrade. However, the degree of the deterioration is much smaller than the case where the layers are processed one by one and then epitaxially grown as in the conventional method for forming a multilayer high-temperature superconducting integrated circuit described with reference to FIG. Therefore, the insulating properties of the second insulating film 35 and the superconducting properties of the third high-temperature superconducting film 37 are relatively good, and sufficiently satisfy the conditions as components of the high-temperature superconducting integrated circuit.

As shown in FIG. 2F, the third high-temperature superconducting film 37 and the first high-temperature superconducting film 21 are provided in the first contact hole 34 and in the third high-temperature superconducting film 37.
And the second high-temperature superconducting film 23 are formed in the second contact hole 3.
6 are connected. Further, the first high-temperature superconducting film 21 and the second high-temperature superconducting film 23 are connected to the third high-temperature superconducting film 37 at the first and second contact holes 34 and 36, respectively, thereby forming the third high-temperature superconducting film 37. They are connected via a high-temperature superconducting film 37. Further, the separated first high-temperature superconducting film 21 or second high-temperature superconducting film 23 can be connected to each other via a third high-temperature superconducting film 37 using a contact hole.

On the other hand, the second high-temperature superconducting film 23 at the wiring intersection 38 is covered with a second insulating film 35, on which a wiring composed of a third high-temperature superconducting film 37 is formed. This allows the insulated intersection of the second high-temperature superconducting film 23 and the third high-temperature superconducting film 37. As described above, when the formation method according to the embodiment shown in FIG. 2 is used, the connection between the high-temperature superconducting films in the same layer and between the high-temperature superconducting films in different layers is performed using the uppermost high-temperature superconducting film. And the intersection of the uppermost high-temperature superconducting film and the lower-layer high-temperature superconducting film without current leakage becomes possible.

As described above, by using this embodiment, a high-temperature superconducting film having excellent superconducting properties and an insulating film having excellent insulating properties can be used in the same layer or between different layers by using the uppermost layer. A multi-layer high-temperature superconducting integrated circuit in which the high-temperature superconducting films are connected to each other and the uppermost high-temperature superconducting film and the lower high-temperature superconducting film intersect in an insulated state can be formed.

It should be noted that the present invention is not limited to the above embodiment, and the processing of a continuous epitaxial film
Although the steps are performed in the order of (b), (c) and (d), the steps may be performed in the order of (c), (d) and (b) in FIG.
Although the intersection of the third high-temperature superconducting film 37 and the lower high-temperature superconducting film is shown only between the second high-temperature superconducting film 23, the first high-temperature superconducting film is formed by the same forming method. A current-free intersection with the film 21 can also be performed.

In the embodiment formed by the forming method shown in FIG. 2, the case of three high-temperature superconducting films and two insulating films has been described. However, when the number of layers is further increased, the uppermost layer is similarly formed. The same effects as in the above embodiment can be obtained by continuously epitaxially growing a film excluding the insulating film immediately below the high-temperature superconducting film and the uppermost high-temperature superconducting film on the substrate in the same vacuum.

Further, when the epitaxial film is processed, since the disorder of the crystallinity on the surface is more remarkable in the high-temperature superconducting film than in the insulating film, a protective layer is formed on the second epitaxially grown high-temperature superconducting film 23. Thin (eg 100n
By forming the STO film of m) in the same vacuum, the crystallinity of the second insulating film 35 and the third high-temperature superconducting film 37 is further improved.

Further, also in the embodiment shown in FIG. 2, an edge having an inclined surface is formed together with the contact holes 34 and 36 to form the uppermost high-temperature superconducting film 37 and the lower high-temperature superconducting film 23, 21 can also be connected.
Furthermore, in the present invention, the connection between the uppermost high-temperature superconducting film and the lower-layer high-temperature superconducting film can be performed only by the edge having the inclined surface instead of the contact hole.

[0048]

As described above, according to the present invention,
In a multi-layer high-temperature superconducting integrated circuit including at least a structure in which three or more high-temperature superconducting films and two or more insulating films are alternately laminated, a continuous epitaxially grown film is formed as a base of the uppermost high-temperature superconducting film. Therefore, the synergistic effect of disorder of epitaxial properties, which was a problem in the conventional formation method, does not occur, and a high-temperature superconducting film having excellent superconducting properties and an insulating film having excellent insulating properties are formed up to the uppermost layer. Can be. Further, connection between high-temperature superconducting films in the same layer and between different layers can be performed.

Further, according to the present invention, the film which is continuously epitaxially grown in the same vacuum is a film excluding the uppermost high-temperature superconducting film and the insulating film immediately thereunder, so that the lower layer of the high-temperature superconducting film is formed by the insulating film. Because the portion including the pattern edge of the film is covered and the insulation between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film disposed thereon is maintained, the uppermost high-temperature superconducting film is formed. And the lower high-temperature superconducting film can intersect in an insulated state.

Further, according to the present invention, since the uppermost high-temperature superconducting film is connected to the lower high-temperature superconducting film, the lower high-temperature superconducting films are connected to each other via the uppermost high-temperature superconducting film. Can be connected.

[Brief description of the drawings]

FIG. 1 is a sectional process view of a first embodiment of a forming method of the present invention.

FIG. 2 is a sectional process view of a second embodiment of the forming method of the present invention.

FIG. 3 is a sectional process view of an example of a conventional forming method.

[Explanation of symbols]

Reference Signs List 20 substrate 21 first high-temperature superconducting film 22 first insulating film 23 second high-temperature superconducting film 24, 35 second insulating film 27 edge junction 28, 29, 34, 36 contact hole 30 tunnel barrier 31, 37 Third high temperature superconducting film

Claims (6)

(57) [Claims] 1. A first step in which two or more high-temperature superconducting films and two or more insulating films are alternately epitaxially grown on a substrate in the same vacuum, and a predetermined processing is performed on the continuously epitaxially grown film. A second step; and a third step of epitaxially growing an uppermost high-temperature superconducting film on the film processed in the second step, wherein the uppermost layer uses the uppermost high-temperature superconducting film. Forming a contact hole for connection between the high-temperature superconducting film and the lower high-temperature superconducting film and for connecting the lower high-temperature superconducting film by the second step. A method for forming a superconducting integrated circuit. 2. The method according to claim 1, wherein the step (b) includes placing an edge having an inclined surface for connection between the uppermost high-temperature superconducting film and a lower-layer high-temperature superconducting film at a position different from the contact hole. 2. The method for forming a multi-layer high-temperature superconducting integrated circuit according to claim 1, wherein the integrated circuit is formed. 3. The second step is to form only an edge having an inclined surface for connection between the uppermost high-temperature superconducting film and the lower-layer high-temperature superconducting film instead of the contact hole. The method for forming a multilayer high-temperature superconducting integrated circuit according to claim 1, wherein: 4. A first step in which two or more high-temperature superconducting films and one or more insulating films are alternately epitaxially grown on a substrate in the same vacuum, and a predetermined processing is performed on the continuously epitaxially grown film. A second step, a third step of epitaxially growing an insulating film immediately below the uppermost high-temperature superconducting film on the film processed in the second step, and a third step immediately below the uppermost high-temperature superconducting film. A fourth step of subjecting the insulating film to desired processing, and a fifth step of epitaxially growing the uppermost high-temperature superconducting film on the film after the fourth step. The second and fourth contact holes for connection between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film using a superconducting film and for connection between the lower high-temperature superconducting films are formed by the second and fourth superconducting films. Forming by process Method for forming a multilayer high-temperature superconducting integrated circuit of symptoms. 5. The method according to claim 1, wherein the second and fourth steps include forming an edge having an inclined surface for connection between the uppermost high-temperature superconducting film and the lower high-temperature superconducting film separately from the contact hole. 5. The method for forming a multilayer high-temperature superconducting integrated circuit according to claim 4, wherein: 6. The method according to claim 6, wherein the second step and the fourth step include replacing only the edge having an inclined surface for connection between the uppermost high-temperature superconducting film and the lower-layer high-temperature superconducting film with the contact hole. 5. The method for forming a multilayer high-temperature superconducting integrated circuit according to claim 4, wherein: