JPS63301576A - Manufacture of superconducting circuit - Google Patents

Abstract

PURPOSE:To facilitate obtaining flat electric circuits by a method wherein a plurality of super-lattice layers of oxide superconductor and super-lattice layers of insulator or semiconductor are alternately laminated and the parts of the super-lattice layers which do not constitute electric circuits are subjected to a heat treatment so as to disorder the super-lattice structures of those parts. CONSTITUTION:Oxide superconductor crystals are made to grow on the surface of a substrate 1 to form super-lattice layers 2 and insulator crystals are made to grow on the surfaces of the super-lattice layers 2 to form super-lattice layers 3. If the parts of the super-lattice layers 2 and 3 which do not constitute electric circuits are subjected to a heat treatment, atoms constituting the superconductor of the super-lattice layers 2 and atoms constituting the insulator of the super- lattice layers 3 are diffused and mixed with each other and the super-lattice structures of those parts are disordered. Therefore, the parts subjected to the heat treatment are converted into metal oxide insulators 4. The parts which are not subjected to the heat treatment show excellent superconducting properties by the existence of the super-lattice layers 2 and constitute electric circuits 5. The surface of such electric circuits 5 coincide with the surfaces of the insulators and do not protrudes like the surfaces formed by deposition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a logic circuit composed of Josephson elements, three-terminal elements, etc. by forming a superlattice layer of an oxide superconductor on the surface of a substrate. , relates to a method of manufacturing a superconducting circuit for forming a memory circuit or the like.

[Prior art] Recently, Y-Ba-Cu-0 systems with a critical temperature of 50 or higher,
Generally chemical formula A-B-Cu such as Y-Ba-Cu-0 system
-0 (A: S c, Y, La- Periodic Table ■1
Oxide-based superconductors represented by group metal elements, B: B2L, Sr, Be- alkaline earth metals) are being discovered one after another, and furthermore, it is possible to fabricate such oxide-based superconductors on a substrate. Attempts have been made to form it as an electrical circuit and manufacture integrated circuits.

To form such a superconducting circuit, a superconducting raw material layer made of the above-mentioned oxide-based superconducting material is uniformly formed on the weir plate 1- by sputtering or the like, and then a desired layer is formed through processes such as dry etching and deposition. Methods for obtaining superconductor circuits are currently in use.

[Problems to be Solved by the Invention] However, in the superconducting circuit obtained as described above, since the surface thereof has severe unevenness formed by debonding, it is difficult to bond with the superconductor. Insulating layers with poor quality are likely to peel off, making it difficult to integrate circuits. Therefore, there is currently a need for a circuit manufacturing method that can form a flat circuit and improve the bonding properties between a superconductor and an insulating layer.

[Object of the Invention] This invention was made in view of the above circumstances, and has the following objects: - To provide a method for manufacturing a superconducting circuit that can obtain a V-flat electric circuit and, therefore, can highly integrate the circuit. The purpose is

[Means for Solving the Problems] The method for manufacturing a superconducting circuit of the present invention includes alternating multiple layers of superlattice layers made of an oxide superconductor and superlattice layers of an insulator or semiconductor on the surface of a base material. The method is characterized in that the superlattice layers are formed, and heat treatment is applied to portions of these superlattice layers other than the portions constituting the current circuit to disorder the superlattice structure of the superlattice layers laminated at those portions.

[Operation] In the superlattice layer subjected to the heat treatment, atoms of the superconductor and the insulator diffuse and mix with each other, and the structure becomes disordered, and becomes an insulator or a semiconductor. On the other hand, the portion that is not subjected to heat treatment exhibits extremely good superconductivity due to the presence of a superlattice layer of a superconductor having a perfect single crystal structure, and forms a predetermined current circuit.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. First, a superlattice layer 2 is formed by growing crystals of an oxide superconductor on the surface of the substrate I. Here, the material of the substrate 1 is Si, Al2O3
, Ti5rOa, LiNbo3. GaAs or the like is used. Moreover, the superlattice layer 2 is based on AB-Cu-0 (however,
A is Y, La, Ce, Sc, Yb, Pr, Nd, Pm
, Sm.

[[A group metal elements such as Eu, Gd, Tb, Dy, Ha, Er, Tm, LU, B is Ba, Sr, Ca.

An oxide superconductor of alkaline earth metal elements such as Be, Ra, Mg, etc.

When forming the superlattice layer 2, MBE method, MOCVD method, MOMBE method, LPE method (liquid phase epitaxy),
Although sputtering method etc. are used, MOCVD method and MOMB
If used in combination with the E method, a good superlattice structure can be obtained. In addition, if the raw material used in this case is an organic compound of the metal element constituting the oxide superconductor (e.g., alkokid compound, acedelacetone compound, ncrope/tanoenyl compound, etc.), the amount of evaporation of the raw material can be reduced. Control can be facilitated.

Next, an insulator crystal is grown on the surface of the superlattice layer 2 by MBE method or the like to form a superlattice layer 3. For example, a metal oxide is used as the material for the superlattice layer 3, but if an oxide of a metal element included in the composition of the superlattice layer 2 is used, diffusion mixing with the superlattice layer 2 by heat treatment can be improved. can be done. Also, B2O3, P2O5
You may use the material which spreads easily, such as. In this way, a plurality of superlattice layers 2 and 3 are alternately formed (see FIG. 2). Here, the thickness of the superlattice layer 2.3 is 20 to 200
Be with people. Further, about 5 to 100 superlattice layers 2 and 3 are formed.

Next, of the superlattice layers 2 and 3 configured as described above, portions that do not constitute an electric circuit are subjected to heat treatment. The heat treatment is performed by irradiating the corresponding portion of the superlattice layer 2.3 with an electron beam, an ion beam, a laser beam, or the like. Then, the atoms constituting the superconductor of the superlattice layer 2 and the atoms constituting the insulator of the superlattice layer 3 are diffused and mixed with each other, and the superlattice structure becomes disordered. Therefore, the portion subjected to the heat treatment becomes an insulator 4 of metal oxide. On the other hand, the areas that are not subjected to heat treatment exhibit extremely good superconductivity due to the presence of the superlattice layer 2 of the superconductor, which is a perfect single crystal structure, and form a predetermined current circuit 5 (see Figure 1). . The surface of such an electric circuit 5 is coincident with the surface of the insulator 4, and does not have a convex shape unlike that formed by divination. In the above embodiment, the insulator 4 is formed at a location other than the electric circuit 5, but a semiconductor may be formed by appropriately selecting the material of the superlattice layer 3.

According to such a method of manufacturing a superconducting circuit, it is possible to obtain a flat electric circuit 5 without any unevenness, and thus the bondability with an insulating layer formed on the surface thereof is greatly improved. Therefore, even if an insulating layer is formed in an extremely small portion, the insulating layer will not peel off, making it possible to highly integrate the circuit. Further, an electric circuit can be further formed on the surface of the electric circuit 5 formed in this way via an insulating layer, and a superconducting circuit can be easily made three-dimensional. Furthermore, by forming the superlattice layer 3 from a semiconductor, it is also possible to form a switching element such as a Noyosefson element, which is extremely promising in practice.

[Manufacturing Example] A superlattice layer was formed on the surface of a substrate made of Si or the like heated to about 800° C. using a gas source MBE apparatus. Here, the raw material gases include barium acetylacetonate (B a (CtH70*)t), ncropentadienyl yttrium (Y (C5H,)3), and ncropentadienyl copper triethylphosphorus (Cu (CsHs)).
) ·P (CtHs)3 was used. These raw material gases were maintained at 150° C., and molecular beam electrolysis was performed in a slightly oxygen atmosphere of 10-' Torr. As a result, a thickness of 100 mm of B2Lo8Yo4Cu is applied to the surface of the substrate.
20 O4 superlattice layers and 60 Y, 03 superlattice layers were alternately formed.

Next, a predetermined portion of the superlattice layer was subjected to heat treatment using an NdYAG laser. The output of the NdYAG laser is 10
The power was 0W, the laser beam diameter was 3μm, and the scanning speed was 10
Cm/min. The temperature of the heat-treated superlattice layer was estimated to be 1100°C. The superconducting circuit thus obtained was extremely flat, and its critical temperature was 93 when measured by the four-terminal method. Moreover, the critical current was 500 A/Cm''.

[Effects of the Invention] As explained above, according to the method for manufacturing a superconducting circuit of the present invention, a superlattice layer made of an oxide superconductor and a superlattice layer made of an insulator or semiconductor are alternately formed on the surface of a base material. Multiple layers are formed, and heat treatment is applied to parts of these superlattice layers other than the parts that constitute the current circuit to disorder the superlattice structure of the superlattice layers stacked at that part, so a flat electric circuit can be created. Therefore, the circuit can be highly integrated, and it is extremely promising in practice as a method for manufacturing superconducting circuits.

[Brief explanation of the drawing]

1 and 2 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a side sectional view showing a superconductor circuit, and FIG. 2 is a side sectional view showing a state before heat treatment. It is. ■...Substrate, 2...Superlattice layer, 3...
...Superlattice layer.

Claims (2)

[Claims] (1) Multiple layers of superlattice layers made of oxide superconductors and superlattice layers of insulators or semiconductors are alternately formed on the surface of the base material, and the portions of these superlattice layers other than those constituting the current circuit are 1. A method for manufacturing a superconducting circuit, comprising subjecting a portion to heat treatment to disorder the superlattice structure of a superlattice layer laminated at that portion. (2) The method for manufacturing a superconducting circuit according to claim 1, characterized in that an organometallic compound is used as a material for the superlattice layer.