JPH04317381A - Manufacture of barrier type electronic element - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a barrier type electronic element in which a function of a barrier junction can sufficiently be performed. CONSTITUTION:A YBaCuO oxide superconductor thin film 2 is formed on a substrate 11. This is formed by a CVD method, a sputtering method or a vapor- depositing method. Then, Fe ions are implanted to the film 2, the implanted ions are diffused inward of the film by heat treatment to form a barrier layer 3. Thereafter, a surface of the layer 3 physically damaged by the ion implantation is removed. Then, a YBaCuO oxide superconductor thin film 4 to become a counter electrode of the film 2 is formed on the layer 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing barrier type electronic devices such as Josephson junction devices and S/I/N (superconducting layer/insulating layer/normal conducting layer) junction devices.

0002

2. Description of the Related Art Conventionally, as a method for manufacturing a Josephson junction element, there is a technique disclosed in, for example, Japanese Unexamined Patent Publication No. 63-283179. The publication describes that ions are implanted into the surface of the first superconductor layer on the substrate to form a barrier layer,
A manufacturing method is shown in which a second superconductor layer is then formed on this barrier layer.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional method for manufacturing a Josephson junction element has the following problems. In other words, the surface of the first superconductor layer and the surface of the barrier layer laminated thereon may be significantly roughened, which may cause defects such as cracks and pinholes in the thinly formed barrier layer. . Furthermore, the surface of the first superconductor thin film on which the barrier layer is laminated has been physically damaged by the ion implantation. Therefore, the bonding function between the barrier layer and each layer may be significantly impaired. In order to prevent such defects and form a good barrier layer, an expensive vacuum evaporation apparatus for forming each layer is required, and moreover, advanced technology is required. Therefore, at present, no practical barrier-type electronic device with the expected performance has been realized.

0004

[Means for Solving the Problems] The present invention has been made to solve these problems, and includes forming a first superconducting layer and implanting the surface of the first superconducting layer by ion implantation. A predetermined element is added and heat treated to diffuse this element into the first superconducting layer to form a barrier layer on the surface layer of the first superconducting layer, and the surface of this barrier layer is formed to a predetermined thickness. After removing the barrier layer, a second superconducting layer or a normal conducting layer is formed on the removed barrier layer.

[0005] Also, a first superconducting layer is formed, and this first superconducting layer is formed.
A gas containing a predetermined element is brought into contact with the surface of the superconducting layer,
A heat treatment is applied to diffuse this element into the first superconducting layer to form a barrier layer on the surface layer of the first superconducting layer, and a predetermined thickness of the surface of this barrier layer is removed. A second superconducting layer or a normal conducting layer is formed on this barrier layer.

[0006] Also, a first superconducting layer is formed, and this first superconducting layer is formed.
Forming an element-added layer containing a predetermined element on the superconducting layer,
Heat treatment is applied to diffuse this element into the first superconducting layer to form a barrier layer on the surface layer of the first superconducting layer, and the addition of the element remaining on the first superconducting layer without being diffused is remove the layer,
A second superconducting layer or a normal conducting layer is formed on the exposed barrier layer.

[0007]

[Operation] The barrier layer is formed by altering the superconductor layer. Further, once the barrier layer is formed, the physically damaged surface of the barrier layer is removed and planarized.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process sectional view showing a method of manufacturing a barrier type electronic device using a superconductor according to a first embodiment of the present invention.

First, an oxide single crystal or polycrystalline substrate 1 is prepared.
A YBaCuO oxide superconductor thin film 2 is formed thereon (see FIG. 1(a)). This formation is performed by a CVD method, a sputtering method, or a vapor deposition method. Next, Fe ions are implanted into the surface of the oxide superconductor thin film 2 using an ion implantation device (see FIG. 3(b)). Next, the ion-implanted substrate 1
The above oxide superconductor thin film 2 is subjected to heat treatment at 800° C. for 1 hour in a tube furnace in an oxygen or low partial pressure oxygen atmosphere. By this heat treatment, the Fe ions implanted into the surface of the oxide superconductor thin film 2 diffuse into the thin film 2, and as a result, the normal conductor YBaCuFeO
A layer is formed, which becomes the barrier layer 3 (see figure (c)). The surface of this barrier layer 3 has been physically damaged by the ion implantation, such as destruction of the crystal lattice, and does not exhibit stable barrier properties. Therefore, the physically damaged surface of the barrier layer 3 is removed by RIE (reactive ion etching). This etching is performed under conditions of a pressure of 0.6 mTorr and a high frequency power of 170 W in an Ar atmosphere. After that, YBa, which will become the counter electrode of the oxide superconductor thin film 2, is placed on the barrier layer 3 whose surface has been removed.
A CuO oxide superconductor thin film 4 is formed (see figure (d)). This formation method is the same as that for the oxide superconductor thin film 2. As a result, a Josephson junction type device is completed.

According to the method for manufacturing a barrier type electronic device according to this embodiment, as described above, the barrier layer 3 is formed by thermal diffusion of ions implanted into the oxide superconductor thin film 2. Furthermore, the physically damaged surface of the barrier layer 3 is removed and planarized by etching. Therefore, the conventional problem of defects occurring in the barrier layer due to the surface roughness of each laminated layer is solved. Moreover,
The surface of the barrier layer 3 that has been physically damaged by the ion implantation is removed by etching. As a result, the Josephson junction that is formed will be able to fully demonstrate its function, and a barrier type device with the expected characteristics can be obtained. Moreover, it can be easily manufactured without requiring sophisticated technology and advanced manufacturing equipment as in the past.

Further, in the above manufacturing method, the YBaCuO oxide superconductor thin film 2 is formed on the substrate 1, and the barrier layer 3 is formed on this oxide superconductor thin film 2. It may be manufactured in In other words, a method may be adopted in which a superconductor substrate is separately prepared and a barrier layer is directly formed on the superconductor substrate by a method similar to the above method, and the same effects as in the above embodiments can be obtained.

Further, in the above embodiment, a case has been described in which Fe ions are implanted into the superconductor thin film 2, but the ion element to be implanted may be Al, Zn, Ni, or Co in addition to Fe. Elements that are generally implanted include, firstly, material components constituting the superconductor thin film in which the barrier layer is formed. For example, if the superconductor thin film is an oxide superconductor, oxygen is used, and if the superconductor thin film is a bismuth-based superconductor, strontium or lead is used. Secondly, it is an element that is highly reactive with the superconductor thin film on which the barrier layer is formed. For example, if the superconductor thin film is an oxide superconductor, indium or the like is applicable. No matter which of these elements is implanted, the same effects as in the above embodiments can be achieved.

Furthermore, in the above embodiment, if the superconductor thin film 2 is made to have a polycrystalline structure and a Josephson junction element is formed in the same manner as the above manufacturing method, the junction state will be as follows. In other words, as shown in Figure 2, polycrystalline YB
The thickness of the insulating layer 22 as a barrier layer formed on the aCuO superconductor thin film 21 is not uniform due to the surface roughness of the polycrystalline superconductor thin film 21. At this time, what actually functions as a junction barrier is a locally thinned minute portion. Therefore, the formed junctions (the □ portions in the figure) are scattered on the surface of the element, and these scattered junctions are connected in parallel in the entire element. In other words, the polycrystalline superconductor thin film 21 has grain boundary weak bonds (circle in the figure) that act as Josephson junctions, and there are scattered areas that act as barriers, allowing current to flow within the grain boundary weak bonds. It is possible to limit the parts. Therefore, weak bonds at grain boundaries can be used as Josephson junctions. In this case, the Josephson junction at the grain boundary is connected in series to the junction formed by the barrier layer formed by thermal diffusion.

[0014] Furthermore, Josephson coupling has a structure in which two superconductors are extremely weakly coupled, but when an insulating film is sandwiched between two superconductors, superconducting carriers tunnel through the insulating film, causing Two superconductors are in a bonded state. Therefore, the current-voltage characteristics had hysteresis. On the other hand, depending on the application, hysteresis may not be desired, and in this case, the following structure may be used. In other words, by adopting a structure in which a metal or semiconductor is sandwiched instead of an insulating film sandwiched between two superconductors, a proximity effect occurs in which the superconductivity on both sides of the metal or semiconductor oozes out. Due to this proximity effect, the two superconductors on both sides become superconductingly coupled, and their current-voltage characteristics no longer have hysteresis, as shown in FIG.

Furthermore, in the method for manufacturing the barrier type electronic device shown in FIG. 1, a Josephson junction device has been described, but an S/I/N junction device can also be manufactured by a similar method. That is, as in the above embodiment, an oxide superconductor thin film 2 is formed on a substrate 1, and a barrier layer 3 is formed on the surface layer thereof. After that, the surface of the barrier layer 3 is subjected to RIE.
and remove Nb, Au, Pt on this barrier layer 3.
, Ag are deposited by sputtering or vapor deposition to form a normal conductive layer. Then, this normal conductive layer is formed into a superconductor thin film 2.
The electrode is opposite to the Even in this method of manufacturing an S/I/N junction element, the same effects as in the above embodiment can be achieved.

According to this embodiment, by implanting ions into the surface layer of the superconductor thin film 2 and diffusing the implanted ions, this surface layer becomes normal conductive and becomes a barrier layer, as described above. It is possible to Furthermore, by controlling the amount of ions to be implanted, the carrier concentration of the formed barrier layer can be controlled, and the state of the barrier layer can be freely selected from an insulating state to a metallic state. Therefore, the formed junction can be either a junction that utilizes the proximity effect or a junction that utilizes the tunnel effect. FIG. 4 is a process cross-sectional view showing a method of manufacturing a barrier type electronic device using a superconductor according to a second embodiment of the present invention.

First, in the same manner as in the first embodiment above,
YBaCuO on an oxide single crystal or polycrystalline substrate 11
Form oxide superconductor thin film 12 (see FIG. 4(a))
. Next, the oxide superconductor thin film 1 formed on the substrate 11
2 is placed in a tube furnace, and an organometallic gas containing Al is introduced into the furnace. As such organometallic gases,
For example, there is tris(dipivaloylmethanato)aluminum Al(C11H9O2)3. Next, the inside of the furnace is heated to 500°C using an infrared lamp, and the gas is thermally decomposed to form an Al film 1 on the oxide superconductor thin film 12 inside the furnace.
3 to a thickness of 0.1 μm (see figure (b))
. At the same time, the Al element is diffused from the Al film 13 toward the inside of the oxide superconductor thin film 12 by heat treatment. As a result, a barrier layer 14, which is a normal conductor, is formed on the surface layer of the oxide superconductor thin film 12 (see FIG. 3(c)). Next, the Al film 1 that was not completely diffused by this heat treatment
3 is removed by RIE to expose the barrier layer 14 (
(See figure (d)). This RIE is performed under the same processing conditions as in the first embodiment. Next, a YBaCuO oxide superconductor thin film 15 is formed on this exposed barrier layer 14 to become a counter electrode of the oxide superconductor thin film 12 (
(See figure (e)). This results in the formation of a Josephson junction element.

The second embodiment also provides the same effects as the first embodiment described above.

In the explanation of the above embodiment, the organometallic gas was explained as containing Al, but Fe, Ni, Z
An organometallic gas containing n, Co may be used, and the same effects as in the above embodiments can be obtained.

Furthermore, in the above embodiment, if the oxide superconductor thin film 12 is made to have a polycrystalline structure, the structure will be similar to that shown in FIG. A similar argument can be made. In addition, the barrier layer 14
S/I/N with a normal conductor formed on top instead of a superconductor
The same effects as in the above embodiments can also be achieved with respect to the structural elements.

Furthermore, in the above embodiment, the case where the Al film 13 was formed on the oxide superconductor thin film 12 using an organometallic gas was explained, but a similar Al film could be formed by sputtering or vacuum evaporation. Alternatively, the same effect as in the above embodiment can be obtained. In this case, instead of Al, Fe, Ni, or Zn may be deposited by sputtering or vacuum evaporation.

[0022]

As explained above, according to the present invention, the barrier layer is formed by altering the superconductor layer. Further, once the barrier layer is formed, the physically damaged surface of the barrier layer is removed and planarized.

[0023] Therefore, defects such as cracks and pinholes do not occur in the thin barrier layer as in the prior art, and the function of the formed bond can be fully demonstrated. Further, it becomes possible to realize a barrier type electronic device without requiring expensive equipment or using advanced technology.

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing a method of manufacturing a barrier type electronic device using a superconductor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a barrier-type electronic device formed using a polycrystalline superconductor.

FIG. 3 is a graph showing current-voltage characteristics when a metal or a semiconductor is used for the barrier layer sandwiched between two superconductors.

FIG. 4 is a process cross-sectional view showing a method for manufacturing a barrier type electronic device using a superconductor according to a second embodiment of the present invention.

[Explanation of symbols]

1...Substrate 2...First YBaCuO oxide superconductor thin film 3...Barrier layer

Claims (9)

[Claims] 1. A first superconducting layer is formed, a predetermined element is added to the surface of the first superconducting layer by ion implantation, and heat treatment is applied to add the element to the first superconducting layer. A barrier layer is formed on the surface layer of the first superconducting layer by diffusion into the interior, the surface of this barrier layer is removed by a predetermined thickness, and a second superconducting layer is formed on the removed barrier layer. 1. A method of manufacturing a barrier type electronic device, comprising: forming a barrier-type electronic device. 2. A first superconducting layer is formed, a gas containing a predetermined element is brought into contact with the surface of the first superconducting layer, and a heat treatment is applied to bring the element into the inside of the first superconducting layer. to form a barrier layer on the surface layer of the first superconducting layer;
A method for manufacturing a barrier type electronic device, comprising removing the surface of the barrier layer by a predetermined thickness, and forming a second superconducting layer on the removed barrier layer. 3. Forming a first superconducting layer, forming an element-added layer containing a predetermined element on the first superconducting layer, and applying heat treatment to add the element to the first superconducting layer. forming a barrier layer on the surface layer of the first superconducting layer by diffusing it inside;
Manufacturing a barrier type electronic device, characterized in that the element-added layer remaining on the first superconducting layer without being diffused is removed, and a second superconducting layer is formed on the exposed barrier layer. Method. 4. The method of manufacturing a barrier type electronic device according to claim 1, wherein the first superconducting layer is formed to have a polycrystalline structure. 5. The method for manufacturing a barrier type electronic device according to claim 3, wherein the element-added layer is formed by a sputtering method or a vacuum evaporation method. 6. A superconducting layer is formed, a predetermined element is added to the surface of the superconducting layer by ion implantation, and heat treatment is applied to diffuse the element into the superconducting layer to form the superconducting layer. A method for manufacturing a barrier-type electronic device, characterized by forming a barrier layer on the surface layer of the barrier layer, removing a predetermined thickness of the surface of the barrier layer, and forming a normal conductive layer on the removed barrier layer. . 7. A superconducting layer is formed, a gas containing a predetermined element is brought into contact with the surface of the superconducting layer, and a heat treatment is applied to diffuse the element into the superconducting layer. 1. A method for manufacturing a barrier type electronic device, which comprises forming a barrier layer on a surface layer, removing a predetermined thickness of the surface of the barrier layer, and forming a normal conductive layer on the removed barrier layer. 8. Forming a superconducting layer, forming an element-added layer containing a predetermined element on the superconducting layer, and applying heat treatment to diffuse the element into the superconducting layer. A barrier type characterized in that a barrier layer is formed on the surface layer of the superconducting layer, the element-added layer remaining on the superconducting layer without being diffused is removed, and a normal conducting layer is formed on the exposed barrier layer. Method of manufacturing electronic devices. 9. The method of manufacturing a barrier type electronic device according to claim 6, wherein the superconducting layer is formed to have a polycrystalline structure.