JPH0483383A - Manufacture of thin film superconducting element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a thin film superconducting element used in superconducting application technology. Ba-C
u-0'if, B1-3r-Ca-Cu-0 system TI
B A p-type oxide superconducting material such as the a-3r-Cu-0 system in which the charge transport carrier in the normal conduction state is a hole, and a Nd-Ce-Cu- material in which the charge transport carrier in the normal conduction state is an electron.
0L N-type oxide superconducting materials with a Nd2Cu○4 type crystal structure such as the Nd-Cu-OxF system have been discovered.9 The details of the superconducting mechanism of these materials are not clear. Applications are expected.

Some of these superconducting transition temperatures (Tc) exceed the liquid nitrogen temperature (77.3 Kelvin), greatly expanding the field of application of superconductors. Concerning conduction elements, there is a Josephson device in which an oxide superconductor is split in half and they are brought into slight contact again, a bridge-type Josephson device in which the oxide superconductor is made into a thin film and a small constriction is formed, and an oxide superconductor interlayer. Au, Ag
Previously, Josephson devices connected with precious metals such as In addition, the characteristics were very unstable.Furthermore, bridge-type devices connected by constricting the oxide superconducting thin film or connected with precious metals had the disadvantage of being damaged by a slight electrostatic shock. A superconducting element with a junction type structure using a superconducting thin film is desired.Since the deposition temperature of the oxide superconducting thin film must be approximately 600°C or higher, the temperature of the oxide superconducting thin film formed on the top is The barrier layer components may diffuse during film formation, or the thermal expansion coefficients of the material used for the oxide superconducting thin film and the material for the barrier layer may be different, which may cause stress to the thin film when it is returned to room temperature, causing the oxide formed on the top to There were problems such as the superconductivity of the superconducting thin film being significantly impaired and the presence of pinholes in the barrier layer.Furthermore, there were problems such as the presence of pinholes in the barrier layer.Furthermore, there were problems such as the presence of pinholes in the barrier layer.Furthermore, pinholes formed on the top due to the mismatch in lattice constant due to the difference in the crystal structure of the oxide superconducting thin film and the barrier layer. The problem is that the crystallinity of the oxide superconducting thin film is poor, and its superconductivity is inferior to that of the oxide superconducting thin film on the substrate. Controlling the crystallinity of a thin film and the amount of oxygen taken into it is not necessarily sufficient to obtain good superconducting properties, and in order to obtain the best superconducting properties, it is necessary to further improve crystallinity and release sufficient oxygen. The present invention solves the above-mentioned problems, and aims to provide a method for manufacturing a p-type or n-type thin film superconducting element with good crystallinity. Means for Solving the Problems In order to solve the above problems, a method for manufacturing a thin film superconducting element according to the present invention. An oxide superconducting thin film barrier layer and an oxide superconducting thin film are formed in this order on a substrate to form three layers. A thin film stack is formed, and X-rays are irradiated during or after thin film deposition.
The C-axis of the thin film is oriented perpendicular to the substrate, and if the oxide thin film is p-type, it is subsequently subjected to oxidation treatment to become a thin-film superconducting element, and if the thin film is n-type, it is directly used as a thin-film superconducting element. The oxide superconducting thin film and barrier layer in a p-type thin film superconducting element are oxides containing Bi, alkaline earth metals, and Cu as main components. In addition, the main component of the oxide superconducting thin film in an n-type thin film superconducting element is represented by F-G-Cu-X, and the main component of the barrier layer is represented by H-Cu-0. Here, '+' = F is one or more elements of neodymium (Nd), samarium (Sm), and plutonium (Pr); iG is cerium (Ce);
), one or more elements of thorium (Th) are one or more elements of oxygen (O) or fluorine (F). In the production of thin film superconducting devices, 1. By irradiating X-rays during or after thin film deposition, oxygen ions, which are anions in the crystal, can be removed from the crystal, and cations can be released by releasing potential energy. Crystallinity is improved by rearranging, growing a thin film with C-axis orientation, and performing an oxidation treatment after X-ray irradiation in the case of an Lp-type compound.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. Example 1 To manufacture the thin film superconductor of the present invention, for example, inside a thin film forming tank 1 as shown in FIG. M. Use a vapor deposition source 2 for thin film deposition, a device 3 for improving crystallinity and reduction treatment, and an oxidation treatment device 12 driven by a microwave power source. In this example, a high-frequency magnetron sputtering device driven by a high-frequency power source is used, and a Rh X-ray tube driven by a high-voltage power source is used as the device for crystallinity improvement and reduction treatment. FIG. 2, which was formed by sputtering on the top, is a process diagram showing an embodiment of the present invention.

Using MgO single crystal as the substrate 51. z X-ray irradiation and xRF magnetron sputtering method revealed that the crystal phase was mainly 2212 phase and the chemical formula was (B i 5-I
IP bII) 2-8 rs-Cat-Cua-Ox
(however, 0≦y<0.5), a 300 nm thick oxide superconducting thin film A was formed as 6, and in the same thin film formation tank for 9 consecutive times, the crystal phase was mainly 2201 phase, and the chemical formula was Biz. -Sr2-Ca2O
A barrier layer 7 of 3 nm thick is deposited with a thickness of 3 nm [step (a) in Figure 2], and an oxide superconducting thin film B is formed thereon as 8. The crystal phase of this thin film is mainly 2212, and the chemical formula is ( B i +--P bv) e-Sr2-Cat-C
Thickness of a2-Ox (0≦y<0.5) 200 n
m [Fig. 2, step (b)].

The above three thin films were all formed at a substrate temperature of 500 t, and the barrier layer 7 and the oxide superconducting thin film B were patterned into a tunnel junction shape by photolithography using a resistor resist 9 and ion milling. (C)].

The result is that without removing the negative resist 9, the inter-electrode separation layer 1
After depositing 250 nm of CaFs as 0 by vacuum evaporation [Step (d) in Figure 2], ultrasonic cleaning with trichloroethane and oxidation treatment equipment (ECR oxygen (O) gas plasma equipment) 12 (ITorr,
13. The surface of the oxide superconducting thin film B was exposed by a lift-off method using 56 MHz, 400 W [Step in Figure 2 (
e)].

To the end Platinum (Pt) with a thickness of 200 nm was deposited by RF magnetron sputtering method as a contact electrode 11 in contact with a part of the oxide superconducting thin film B using a metal mask to complete the thin film superconducting element 14 [Steps in Figure 2] (
f)].

It was confirmed that the thin film superconducting device 14 produced by this manufacturing method exhibits good superconducting tunneling properties and the Josephson effect at liquid nitrogen temperatures. Figure 3 is an X-ray diffraction pattern diagram of the three-layer film of this thin film superconducting device. It is. according to this,
At a film formation temperature of 500°C, each layer showed C-axis orientation, and RHEED observation confirmed epitaxial growth.The characteristics of this thin film superconducting element are 15
A superconducting current of 0 microampere flowed (DC Josephson effect), and the operation had hysteresis. -An annealing treatment in oxygen at a temperature below 700°C was applied to a three-layer film similar to that used in the old book example. It was confirmed that the superconductivity of both A and B oxide superconducting thin films was improved, and the properties of junction-type superconducting devices using these three-layer films could be improved. Crystallinity improvement and reduction treatment by X-ray irradiation can be efficiently and easily carried out by performing the film at room temperature for a certain period of time after film formation. In other words, the present inventors confirmed that this phenomenon also occurs when the thin film deposition process, crystallinity improvement, and reduction treatment are alternately repeated at the film formation temperature. Rough polishing of a thin film varies depending on the surface condition, and the strength must be selected optimally for each case.
It has been confirmed that the temperature range is 500℃ or higher.Regarding treatment time L Rough polishing of thin film There is a minimum value required depending on the surface condition of the film.From the point of view of improving crystallinity and performing reduction treatment. However, it is most desirable to perform this treatment simultaneously with thin film deposition (depending on the type of thin film deposition process, sufficient effects may not be obtained because the surface treatment temperature is limited to the deposition substrate temperature). The present inventors and others have confirmed that the results are equivalent to or similar to the case where the crystallinity improvement and reduction treatment are performed by interrupting the thin film deposition, that is, the thin film deposition process, the crystallinity improvement and reduction treatment are alternately repeated. We have confirmed that the above effects can be obtained.In the thin film deposition process, each constituent element is in an excited state immediately after deposition, and in some cases it often takes several minutes to stabilize. (Especially for those with a laminated structure, there are cases where stabilization is achieved by interrupting the deposition every time one periodic structure is deposited. If the crystallinity is improved and the reduction treatment is performed during such a deposition interruption time, Although it is thought that ideal crystallinity improvement and reduction treatment can be performed in a short period of time, the present inventors succeeded in creating a superconducting thin film with excellent properties by interrupting the deposition at appropriate intervals and performing crystallinity improvement and reduction treatment. Furthermore, the present inventors confirmed that it is effective to set the thickness of the film deposited between 10 Å and 100 Å during the deposition time interval.41 Crystallinity Improvement Treatment and Oxidation The oxidation treatment method used when the treatment is performed simultaneously with thin film deposition, or when the thin film deposition is interrupted, that is, when the thin film deposition process, crystallinity improvement treatment, and oxidation treatment process are repeated alternately, is ζ. We discovered that it is effective and simple to treat with oxygen ions generated by the discharge of oxygen-containing gas, or to irradiate neutral oxygen atoms in an excited state. When using the apparatus 12, oxygen gas or a mixed gas containing oxygen is introduced into the plasma generation chamber 13 connected to the thin film forming tank 1, and this gas is irradiated with microwaves to generate discharge plasma, which is then attached to a magnet. 15 found that high-energy oxygen ions and neutral oxygen atoms efficiently oxidize p-type superconducting thin films by applying a magnetic field and increasing the probability of ionization. Superconducting thin film B is mainly (B i +-, P tz) 2-8
r2Ca+-Cu2-Ox (O≦y<0.5)
2212 crystal phase, the barrier layer is mainly Blp-S
The thin film superconducting element, oxide superconducting thin film A and oxide superconducting thin film B, which are 2201 crystal phases consisting of ra-Cu+-0, are mainly (B i +-, P b M) 2-
S r 2-Ca2-Cus-OX (O≦y<0
．． 5) 2223 crystal phase, the barrier layer is mainly (B
i +-, P bν)2-Srs-Cae Cus
A thin film superconducting element having a 2201 crystal phase called OX exhibits excellent superconducting properties.Example 2 Next, another example of the present invention will be described with reference to the drawings.

The thin film forming apparatus and substrate were the same as those in the previous example.
An oxide thin film containing u 04 (x=0.15) as a main component was deposited to a thickness of 300 nm.9 Subsequently, in the same thin film forming tank I, N de-tc e *C, u Oa
In step (a) of FIG. 2, a barrier layer 7 of (X=0) was deposited to a thickness of 3 nm.

Next, an oxide superconducting thin HD of N da-CeXCu 04 (X=0.15) was deposited to a thickness of 200 nm (step (b) in FIG. 2).

The substrate temperature was 500° C. in both cases.

Thereafter, the barrier layer 7 and the oxide superconducting thin film 8 were patterned into a tunnel junction shape by photolithography using a negative resist 9 and ion milling [Step (C) in FIG. 2].

Interelectrode separation layer 1 without removing the resistor 9
After depositing 250 nm of CaFe as 0 by vacuum evaporation [step (d) in FIG. 2], ultrasonic cleaning with trichloroethane and oxidation treatment apparatus 12 (
The oxide superconducting thin film 8 was exposed by a lift-off method using ITorr, 13.56 MHz, 400 W (Step (e) in Figure 2).

Finally, use a metal mask to contact a part of 8, which is an oxide superconducting thin film, to form a contact electrode of 200 nm.
The superconducting element 14 was completed by depositing Pt by RF magnetron sputtering method [Step (f) in FIG. 2].

It was confirmed that the superconducting device produced by this manufacturing method shows good superconducting tunneling properties and Josephson effect at liquid nitrogen temperature. Pattern diagram a According to this, each layer has a C
It has been confirmed that epitaxial growth has occurred through RHEED observation, etc. As a resistive substrate 5, a single-crystal substrate is effective for depositing a highly crystalline oxide thin film, and Mg fart
Single crystals such as LaAl0a, LaGaO3, and strontium titanate may be used.Furthermore, metals such as Au, Ag, Pd, and Cu may be used as contact electrodes. The following effects can be obtained according to the method for manufacturing a conductive element: (a) When manufacturing a p-type thin film superconducting element on a substrate, Since the thin film is subjected to C-axis orientation and crystallinity is improved, a thin film superconducting element with good superconducting properties can be obtained.

(b) When manufacturing an n-type thin film superconducting device on a substrate, X-rays are irradiated during or after thin film deposition to orient the thin film along the C axis, improving crystallinity and ensuring good superconducting properties. (c) Since the thin film superconducting device produced by the manufacturing method of the present invention has good superconducting properties, it can be applied to superconducting quantum interferometers, computer memory, computer logic, etc., and has practical effects. Deam

[Brief explanation of drawings]

Figure 1 shows the basic configuration of the manufacturing equipment used to carry out the method for manufacturing thin film superconductor elements of the present invention.
(f) is a process diagram of the method for manufacturing a thin film superconducting device according to the present invention. This is an X-ray diffraction pattern diagram of the three-layer film of Example 2. 4... Oxide thin 11U5... Substrate 6, 8... Oxide superconducting thin ji, 7... Barrier film 9. ... Photoresist, 10 ... Inter-electrode separation layer 11 ... Contact electrode 14 ... Thin film superconducting material Name of agent Patent attorney Shigetaka Awano

Claims (7)

[Claims] (1) Form an oxide superconducting thin film A on a substrate, form a barrier layer on the oxide superconducting thin film A, and form an oxide superconducting thin film B on the barrier layer L. The superconducting thin film A, the barrier layer, and the oxide superconducting thin film B are irradiated with X-rays to align the c-axis and subjected to oxidation treatment, and then a photoresist film is formed on the oxide superconducting thin film B and patterned. forming an interelectrode separation layer thicker than the barrier layer thereon, exposing the oxide superconducting thin film B by a lift-off method, and forming a contact electrode on the exposed oxide superconducting thin film B. Method for manufacturing superconducting elements. Here, the oxide superconducting thin film A, the barrier layer, and the oxide superconducting thin film B are oxides containing bismuth (Bi), alkaline earth metals, and copper (Cu) as main components, or Bi, lead (Pb).
b) is an oxide whose main components are an alkaline earth metal and copper (Cu). (2) Oxide superconducting thin film A and oxide superconducting thin film B are mainly (Bi_1_-_yPb_y)_2-Sr_2
-Ca_1-Cu_2-O_x, 2 where 0≦y<0.5
212 crystal phase, barrier layer is mainly Bi_2-Sr_2
-Cu_1-O_x 2201 crystal phase Claim 1
A method for manufacturing the thin film superconducting device described above. (3) Oxide superconducting thin film A and oxide superconducting thin film B are mainly (Bi_1_-_yPb_y)_2-Sr_2
-Ca_2-Cu_3-O_x, 2 where 0≦y<0.5
223 crystal phase, the barrier layer is mainly (Bi_1_-_y
Pb_y)_2-Sr_2-Ca_2-Cu_3-O_
2. The method for manufacturing a thin film superconducting device according to claim 1, wherein the thin film superconducting device has a 2201 crystal phase of x. (4) Claim 1, wherein the thin film after X-ray irradiation is oxidized by irradiating oxygen ions or metastable oxygen atoms in an excited state.
A method for manufacturing the thin film superconducting device described above. (5) Forming an oxide superconducting thin film C on a substrate, forming a barrier layer on the oxide superconducting thin film C, forming an oxide superconducting thin film D on the barrier layer, and forming the oxide superconducting thin film C on the substrate. The oxide superconducting thin film C, the barrier layer and the oxide superconducting thin film D are irradiated with X-rays to align the c-axis, and then a photoresist film is formed on the oxide superconducting thin film D and patterned,
After that, forming an interelectrode separation layer thicker than the barrier layer,
A method for manufacturing a thin film superconducting element, in which an oxide superconducting thin film D is exposed by a lift-off method, and a contact electrode is formed on the exposed oxide superconducting thin film D. Here, oxide superconducting thin film C and oxide superconducting thin film D
is mainly represented by FG-Cu-X, and the barrier layer is mainly represented by H-Cu-O. Here, F is neodymium (Nd), samarium (Sm)
, one or more elements of plutonium (Pr), G is one or more elements of cerium (Ce) or thorium (Th), X is one or more elements of oxygen (O) or fluorine (F) It is. (6) The oxide superconducting thin film C, the barrier layer and the oxide superconducting thin film D are Nd_2_-_xCe_xCuO_4 (x=
6. The method for manufacturing a thin film superconducting element according to claim 5. (7) The method for manufacturing a thin film superconducting device according to claim 1 or 5, characterized in that during the step of forming the oxide superconducting thin film and the barrier layer, thin film deposition and X-ray irradiation are alternately repeated.