JPH06338639A - Manufacture of josephson element - Google Patents
Manufacture of josephson elementInfo
- Publication number
- JPH06338639A JPH06338639A JP5128753A JP12875393A JPH06338639A JP H06338639 A JPH06338639 A JP H06338639A JP 5128753 A JP5128753 A JP 5128753A JP 12875393 A JP12875393 A JP 12875393A JP H06338639 A JPH06338639 A JP H06338639A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- metal oxide
- oxide superconducting
- superconducting thin
- hydrogen ions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 26
- 239000010409 thin film Substances 0.000 claims abstract description 60
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 56
- -1 hydrogen ions Chemical class 0.000 claims abstract description 29
- 239000001257 hydrogen Substances 0.000 claims abstract description 28
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 26
- 239000000758 substrate Substances 0.000 claims abstract description 14
- 150000004706 metal oxides Chemical class 0.000 claims description 54
- 229910002480 Cu-O Inorganic materials 0.000 claims description 7
- 239000002131 composite material Substances 0.000 claims description 6
- 150000001875 compounds Chemical class 0.000 claims description 6
- 229910052746 lanthanum Inorganic materials 0.000 claims description 6
- 229910052727 yttrium Inorganic materials 0.000 claims description 3
- 229910052706 scandium Inorganic materials 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 abstract description 17
- 238000007254 oxidation reaction Methods 0.000 abstract description 17
- 239000000463 material Substances 0.000 abstract description 16
- 150000002500 ions Chemical class 0.000 abstract description 10
- 238000004544 sputter deposition Methods 0.000 abstract description 3
- 229910002244 LaAlO3 Inorganic materials 0.000 abstract 1
- 238000005299 abrasion Methods 0.000 abstract 1
- 239000002887 superconductor Substances 0.000 description 13
- 239000002184 metal Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000010955 niobium Substances 0.000 description 5
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 238000000137 annealing Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000005668 Josephson effect Effects 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 238000010884 ion-beam technique Methods 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 229920002120 photoresistant polymer Polymers 0.000 description 2
- 229910015901 Bi-Sr-Ca-Cu-O Inorganic materials 0.000 description 1
- 241000238366 Cephalopoda Species 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 229910009203 Y-Ba-Cu-O Inorganic materials 0.000 description 1
- 238000002679 ablation Methods 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- CFJRGWXELQQLSA-UHFFFAOYSA-N azanylidyneniobium Chemical compound [Nb]#N CFJRGWXELQQLSA-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000000608 laser ablation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、超伝導素子、特に接合
部を有する金属酸化物超伝導薄膜を用いたジョセフソン
素子の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a superconducting device, particularly a Josephson device using a metal oxide superconducting thin film having a junction.
【０００２】[0002]
【従来の技術】従来、超伝導体としては、鉛（Ｐｂ）も
しくはニオブ（Ｎｂ）等の金属超伝導体、窒化ニオブ
（ＮｂＮ）、ニオブ３ゲルマニウム（Ｎｂ3 Ｇｅ）もし
くはシェブレル（ＰｂＭｏ6.4 Ｓ8 ）などの金属化合
物、又は金属酸化物のＢＰＢＯ（Ｂａ−Ｐｂ−Ｂｉ−
Ｏ）に限られていた。また、最近、ＢＫＢＯ（Ｂａ−Ｋ
−Ｂｉ−Ｏ）の金属酸化物も超伝導体であることが発見
された。これらの超伝導体において、その超伝導臨界温
度（Ｔc ）は、合金系では最高でもＮｂ3 Ｇｅの２３．
６ケルビンであり、ＢＰＢＯ、ＢＫＢＯ等の金属酸化物
でも３０ケルビン程度であり、超伝導装置として動作さ
せるためには、冷却材として高価で取扱いの難しい液体
ヘリウム（沸点４．２ケルビン）を用いなくてはならな
かった。これに対し、近年発見されたＣｕを含む酸化物
超伝導体の中にはＴc が１００ケルビンを超えるものも
あり、これらの超伝導体は安価で取扱いの容易な小型冷
凍機で冷却するだけで超伝導状態に遷移する。代表的な
物質としては、Ｙ−Ｂａ−Ｃｕ−Ｏ系、Ｂｉ−Ｓｒ−Ｃ
ａ−Ｃｕ−Ｏ系、Ｔｉ−Ｂａ−Ｃａ−Ｃｕ−Ｏ系の材料
が知られており、超伝導臨界温度（Ｔc ）はそれぞれ約
９２ケルビン、１１５ケルビン、１２５ケルビンであ
る。このＣｕを含む酸化物超伝導体を用いれば、冷却材
として安価で取扱いの容易な小型冷凍機によって動作可
能な超伝導装置を作製することが可能となり、応用範囲
の拡大を図ることができる。2. Description of the Related Art Conventionally, as a superconductor, a metal superconductor such as lead (Pb) or niobium (Nb), niobium nitride (NbN), niobium 3 germanium (Nb 3 Ge) or chevrel (PbMo 6.4 S 8 ) Or the like, or a metal oxide such as BPBO (Ba-Pb-Bi-).
It was limited to O). Recently, BKBO (Ba-K
It has been discovered that the metal oxide (-Bi-O) is also a superconductor. In these superconductors, the superconducting critical temperature (T c ) of the alloy system is at most 23.Nb 3 Ge.
It is 6 Kelvin, and even metal oxides such as BPBO and BKBO are about 30 Kelvin. To operate as a superconducting device, liquid helium (boiling point 4.2 Kelvin) that is expensive and difficult to handle is used as a coolant. I shouldn't have. On the other hand, some recently discovered oxide superconductors containing Cu have a T c of over 100 Kelvin, and these superconductors can be cooled in a small refrigerator that is inexpensive and easy to handle. Makes a transition to the superconducting state. Typical materials are Y-Ba-Cu-O system and Bi-Sr-C.
Materials of a-Cu-O type and Ti-Ba-Ca-Cu-O type are known, and their superconducting critical temperatures ( Tc ) are about 92 Kelvin, 115 Kelvin, and 125 Kelvin, respectively. If this oxide superconductor containing Cu is used, it becomes possible to manufacture a superconducting device that can be operated by a small refrigerator that is inexpensive and easy to handle as a coolant, and the range of applications can be expanded.
【０００３】[0003]
【発明が解決しようとする課題】上記のような超伝導材
料を用いて有効なデバイスを作製するためには、ジョセ
フソン接合の形成が不可欠である。そして、ジョセフソ
ン接合を用いれば、高周波ミキサーや高周波検波器、超
高感度磁気センサー、その他高性能な機能素子を実現す
ることが可能となる。Formation of a Josephson junction is indispensable in order to manufacture an effective device using the above-mentioned superconducting material. Then, by using the Josephson junction, it becomes possible to realize a high-frequency mixer, a high-frequency detector, an ultra-sensitive magnetic sensor, and other high-performance functional elements.
【０００４】ところで、ジョセフソン接合を形成するに
当たって、超伝導体のコヒーレンス長程度のサイズの接
合部分を形成する必要がある。しかし、近年発見された
金属酸化物超伝導体のコヒーレンス長は数ｎｍ程度と非
常に短く、ジョセフソン接合を形成するには非常に微細
な接合部分を形成する必要がある。このため、従来の金
属系超伝導体に用いられてきた方法をそのまま適用する
ことは困難であり、ジョセフソン接合を形成する新たな
方法が要望されている。By the way, in forming the Josephson junction, it is necessary to form a junction portion having a size about the coherence length of the superconductor. However, the coherence length of a metal oxide superconductor discovered in recent years is as short as several nanometers, and it is necessary to form a very fine junction to form a Josephson junction. Therefore, it is difficult to directly apply the method used for the conventional metal-based superconductor, and a new method for forming a Josephson junction is desired.
【０００５】本発明は、前記従来技術の課題を解決する
ため、制御性良く簡単にジョセフソン接合を形成するこ
とのできる金属酸化物超伝導体を用いたジョセフソン素
子の製造方法を提供することを目的とする。In order to solve the above-mentioned problems of the prior art, the present invention provides a method for manufacturing a Josephson device using a metal oxide superconductor which can form a Josephson junction with good controllability. With the goal.
【０００６】[0006]
【課題を解決するための手段】前記目的を達成するた
め、本発明に係るジョセフソン素子の第１の製造方法
は、基板上に金属酸化物超伝導薄膜を形成し、前記金属
酸化物超伝導薄膜上の微小な間隙部で分離された２つの
端子部に選択的に水素イオンを照射し、前記金属酸化物
超伝導薄膜に酸化処理を施すことを特徴とする。In order to achieve the above object, a first method for manufacturing a Josephson device according to the present invention is to form a metal oxide superconducting thin film on a substrate, It is characterized in that two terminal portions separated by a minute gap portion on the thin film are selectively irradiated with hydrogen ions to oxidize the metal oxide superconducting thin film.
【０００７】また、本発明に係るジョセフソン素子の第
２の製造方法は、表面に段差部分と、前記段差部分によ
って分離された２つの平面部分とを有する基板上に、前
記段差部分及び前記２つの平面部分を含む領域に金属酸
化物超伝導薄膜を形成し、前記２つの平面部分上の金属
酸化物超伝導薄膜を端子部とし、前記段差部分上の金属
酸化物超伝導薄膜を接合部とするジョセフソン素子の製
造方法であって、少なくとも前記接合部に水素イオンを
照射し、前記金属酸化物超伝導薄膜に酸化処理を施すこ
とを特徴とする。According to a second method of manufacturing a Josephson device according to the present invention, the step portion and the step 2 are formed on a substrate having a step portion on the surface and two plane portions separated by the step portion. A metal oxide superconducting thin film is formed in a region including two plane portions, the metal oxide superconducting thin film on the two plane portions serves as a terminal portion, and the metal oxide superconducting thin film on the step portion serves as a joint portion. The method of manufacturing a Josephson device according to claim 1, wherein at least the junction is irradiated with hydrogen ions, and the metal oxide superconducting thin film is oxidized.
【０００８】また、前記本発明の第１又は第２の製造方
法の構成においては、金属酸化物超伝導薄膜としてＡ−
Ｂ−Ｃｕ−Ｏ複合化合物を用いるのが好ましい。但し、
ＡはＳｃ、Ｙ、Ｌａ及びＬａ系列元素（原子番号５７、
５９〜６０、６２〜７１）から選ばれる少なくとも１種
の元素、Ｂは６ａ族元素から選ばれる少なくとも１種の
元素であり、Ａ、Ｂ元素とＣｕ元素の濃度比は前記（数
１）によって表記される。Further, in the structure of the first or second manufacturing method of the present invention, the metal oxide superconducting thin film is formed of A-
It is preferable to use a B-Cu-O composite compound. However,
A is Sc, Y, La and La series elements (atomic number 57,
59-60, 62-71), B is at least one element selected from the 6a group elements, and the concentration ratio of A, B elements and Cu elements is determined by the above (Equation 1). It is written.
【０００９】また、前記本発明の第１又は第２の製造方
法の構成においては、金属酸化物超伝導薄膜としてＢｉ
−Ｓｒ−Ｃａ−Ｃｕ−ＯもしくはＴｌ−Ｂａ−Ｃａ−Ｃ
ｕ−Ｏ複合化合物を用いるのが好ましい。In addition, in the structure of the first or second manufacturing method of the present invention, the metal oxide superconducting thin film is made of Bi.
-Sr-Ca-Cu-O or Tl-Ba-Ca-C
It is preferable to use a u-O composite compound.
【００１０】[0010]
【作用】前記本発明の第１又は第２の製造方法によれ
ば、均一に薄膜化した金属酸化物超伝導薄膜を用い、水
素イオンの照射と酸化処理を基本とするプロセスによっ
てジョセフソン接合を形成することができる。水素イオ
ンの照射による金属酸化物超伝導薄膜の処理は制御性が
良く、しかも簡単であるため、従来行われてきた積層構
造を利用して作製する方法に比べ、極めて簡単なプロセ
スで再現性良くジョセフソン素子を作製することができ
る。また、基本的に平面構造によってジョセフソン接合
が形成されるので、他の電子デバイスや他の材料との集
積化の際などに特に有効である。According to the first or second manufacturing method of the present invention, a Josephson junction is formed by a process based on irradiation of hydrogen ions and oxidation treatment using a metal oxide superconducting thin film that is uniformly thinned. Can be formed. The treatment of metal oxide superconducting thin films by irradiation with hydrogen ions has good controllability and is simple. Therefore, compared to the conventional method using a laminated structure, the process is extremely simple and reproducible. Josephson devices can be manufactured. In addition, since the Josephson junction is basically formed by the planar structure, it is particularly effective for integration with other electronic devices and other materials.
【００１１】[0011]
【実施例】以下、実施例を用いて本発明をさらに具体的
に説明する。 （実施例１）図１（ａ）は本発明に係るジョセフソン素
子の製造方法を示す平面図、図１（ｂ）はその要部断面
図である。EXAMPLES The present invention will be described in more detail below with reference to examples. (Embodiment 1) FIG. 1A is a plan view showing a method of manufacturing a Josephson device according to the present invention, and FIG.
【００１２】図１に示すように、例えばＭｇＯ、ＬａＡ
ｌＯ3 等の誘電体基板１の上に、金属酸化物超伝導薄膜
２を形成する。金属酸化物超伝導薄膜２としてＹＢａ2
Ｃｕ 3 Ｏx 系やＢｉ2 Ｓｒ2 Ｃａ2 Ｃｕ3 Ｏx 系の超伝
導材料を用いれば、高周波スパッタリング法、レーザー
アブレーション法などによって高品質な薄膜を容易に形
成することができる。As shown in FIG. 1, for example, MgO, LaA
103On the dielectric substrate 1 such as a metal oxide superconducting thin film
Form 2. YBa as the metal oxide superconducting thin film 22
Cu 3OxSystem and Bi2Sr2Ca2Cu3OxSuper Biography
If conductive material is used, high frequency sputtering method, laser
Easy to form high quality thin film by ablation method
Can be made.
【００１３】以上のようにして金属酸化物超伝導薄膜２
を形成し、微小な間隙部３によって２つに分離された端
子部４、４（図１（ａ）の斜線部分）に水素イオンを照
射した後、金属酸化物超伝導薄膜２に酸化処理を施す。
水素イオンの照射は、例えば、カウフマン型イオン源を
用い、イオン加速電圧；１ｋＶ、イオン電流密度；１０
-4Ａ／ｃｍ2 程度で、真空中において約２０分間行えば
効果が生じる。尚、図１（ａ）のように必要な部分（斜
線部分）のみに水素イオンを照射するには、金属酸化物
超伝導薄膜２の上にメタルマスク等を置くか、又はパタ
ーン化されたエポキシ系等の紫外線フォトレジストやＰ
ＭＭＡ、ＣＭＳ等の電子ビームレジストなどを用いれば
よい。但し、水素イオンは材料を透過する割合が大きい
ため、レジストの厚さは十分厚くするのが好ましい。ま
た、水素イオンによる集束イオンビームを用いれば、マ
スク等を用いなくても、図１（ａ）のパターン部分（斜
線部分）に水素イオンを選択的に照射することができ
る。この方法は、非常に高精度に照射することができ最
も有効性が高いが、装置が非常に大がかりとなり高価で
ある。As described above, the metal oxide superconducting thin film 2
And irradiating the terminal portions 4 and 4 (hatched portions in FIG. 1A) separated into two by the minute gap portion 3 with hydrogen ions, the metal oxide superconducting thin film 2 is oxidized. Give.
For the irradiation of hydrogen ions, for example, using a Kauffman type ion source, an ion acceleration voltage; 1 kV, an ion current density; 10
-4 A / cm 2 is effective for about 20 minutes in vacuum. Incidentally, in order to irradiate only necessary portions (hatched portions) with hydrogen ions as shown in FIG. 1A, a metal mask or the like is placed on the metal oxide superconducting thin film 2, or a patterned epoxy is used. UV photoresists such as system and P
An electron beam resist such as MMA or CMS may be used. However, it is preferable that the thickness of the resist be sufficiently thick because hydrogen ions have a high rate of permeating the material. If a focused ion beam of hydrogen ions is used, hydrogen ions can be selectively irradiated to the pattern portion (hatched portion) of FIG. 1A without using a mask or the like. This method can irradiate with extremely high accuracy and is most effective, but the apparatus is very large and expensive.
【００１４】酸化処理の方法として最も簡便で確実な方
法は、酸素中でアニール処理を施す方法である。例え
ば、Ｂｉ2 Ｓｒ2 Ｃａ2 Ｃｕ3 Ｏx 系の材料を用いる場
合には、８５０℃前後の温度でアニール処理を施せばよ
く、他の材料を用いる場合であっても、多少の差はある
ものの、それに近い温度でアニール処理を施せばよい。
また、照射後の試料を酸素プラズマ中に置くことによっ
ても酸化処理を実現することができる。The simplest and most reliable method of oxidation treatment is to perform annealing treatment in oxygen. For example, when a Bi 2 Sr 2 Ca 2 Cu 3 O x type material is used, annealing treatment may be performed at a temperature of about 850 ° C. Even if another material is used, there is a slight difference. However, it may be annealed at a temperature close to it.
The oxidation treatment can also be realized by placing the irradiated sample in oxygen plasma.
【００１５】以上のようにして金属酸化物超伝導薄膜２
に水素イオンを照射した後、酸化処理を施すことによっ
て、その超伝導特性を制御することができる。図２は、
この効果を明らかにするための実験結果の一例である。
この実験においては、ＭｇＯ単結晶基板を約６５０℃に
加熱し、高周波マグネトロンスパッタリング法によって
膜厚２５０ｎｍのＢｉ2 Ｓｒ2 Ｃａ2 Ｃｕ3 Ｏx 薄膜を
堆積させたものを用いた。そして、このＢｉ2 Ｓｒ2 Ｃ
ａ2 Ｃｕ3 Ｏx 薄膜に水素イオンを照射した後、酸化処
理を施したものの臨界電流密度の温度変化を示したもの
が図２である。ここで、水素イオンの照射は、イオン加
速電圧；１ｋＶ、イオン電流密度；８×１０-5Ａ／ｃｍ
2 で、真空中において１５００秒間行った。その後、８
５５℃の温度で５時間にわたって酸素アニールを施し
た。図２において、Ａは水素イオンを照射した後に酸化
処理を施した試料の特性を示し、Ｂ（比較例）は水素イ
オンを照射せずに酸化処理のみを施した試料の特性を示
す。図２から明らかなように、Ａにおいては、超伝導特
性を示す一つの指標である臨界電流密度が約１桁上昇し
ている。この原因は、水素イオンの照射及び酸化処理に
よって材料中のイオン、特に酸素イオンの結合状態が変
化し、材料中にピンニングセンターが導入され、また、
材料の結晶性が向上したことによるものと考えられる。
尚、本発明者等は、図２に示したような超伝導特性の向
上の程度は、イオン照射の条件及び酸化処理の条件を調
節することにより、極めて再現性良く制御できることを
見い出した。これにより、金属酸化物超伝導薄膜に部分
的に水素イオンを照射すれば、部分的に超伝導特性を生
じさせたり、部分的に超伝導特性を消失させることも可
能である。As described above, the metal oxide superconducting thin film 2
The superconducting properties can be controlled by irradiating the substrate with hydrogen ions and then subjecting it to oxidation treatment. Figure 2
It is an example of an experimental result for clarifying this effect.
In this experiment, a MgO single crystal substrate was heated to about 650 ° C. and a Bi 2 Sr 2 Ca 2 Cu 3 O x thin film having a film thickness of 250 nm was deposited by a high frequency magnetron sputtering method. And this Bi 2 Sr 2 C
After irradiation with hydrogen ions in a 2 Cu 3 O x thin film, shows the temperature variation of the critical current density but subjected to oxidation treatment is FIG. Here, the irradiation of hydrogen ions is performed by using an ion acceleration voltage of 1 kV and an ion current density of 8 × 10 −5 A / cm.
2 , 1500 seconds in vacuum. Then 8
Oxygen annealing was performed at a temperature of 55 ° C. for 5 hours. In FIG. 2, A shows the characteristics of the sample that was subjected to the oxidation treatment after being irradiated with hydrogen ions, and B (Comparative Example) shows the characteristics of the sample that was subjected to only the oxidation treatment without being irradiated with hydrogen ions. As is clear from FIG. 2, in A, the critical current density, which is one index showing superconducting properties, is increased by about one digit. This is because the bonding state of ions in the material, especially oxygen ions, is changed by the irradiation of hydrogen ions and oxidation treatment, and pinning centers are introduced into the material.
This is probably because the crystallinity of the material was improved.
Note that the present inventors have found that the degree of improvement in superconducting properties as shown in FIG. 2 can be controlled extremely reproducibly by adjusting the conditions of ion irradiation and conditions of oxidation treatment. Accordingly, if the metal oxide superconducting thin film is partially irradiated with hydrogen ions, it is possible to partially generate the superconducting property or to partially disappear the superconducting property.
【００１６】図１に示すような本発明の方法で作製した
素子においては、金属酸化物超伝導薄膜２の形成条件や
水素イオンの照射条件、又は酸化処理の条件を適当に設
定することにより、水素イオンを照射した端子部４の領
域だけが超伝導特性を示し、照射しなかった他の部分は
超伝導特性を有しないか又は超伝導特性の劣った状態に
することができる。このことは、金属酸化物超伝導薄膜
２の疑似的なパターン化を行ったことになる。このた
め、超伝導状態にある２つの端子部４、４が、超伝導特
性を有しないか又は超伝導特性の劣った間隙部３を介し
て互い非常に接近した状態となる。従って、間隙部３の
幅を十分小さくすれば、２つの端子部４、４は間隙部３
を介して互いに弱く結合することとなり、間隙部３の両
端ではジョセフソン接合特性を示すことになる。実際、
本発明者等は、２つの端子部４、４に引き出し電極を接
続し、２つの端子部４、４間の電流電圧特性を測定した
結果、ジョセフソン特性を示すことを確認した。さら
に、本発明のジョセフソン素子の製造方法においては、
水素イオンの照射条件や酸化処理の条件を変えることに
よって間隙部３での結合状態を変化させることができる
ことから、このような条件を調節することにより、所望
のジョセフソン接合を制御性良く、しかも再現性良く作
製することが可能となる。In the device manufactured by the method of the present invention as shown in FIG. 1, by appropriately setting the conditions for forming the metal oxide superconducting thin film 2, the irradiation conditions of hydrogen ions, or the conditions of oxidation treatment, Only the region of the terminal portion 4 which is irradiated with hydrogen ions exhibits superconducting properties, and the other part which is not irradiated has no superconducting properties or is inferior in superconducting properties. This means that the metal oxide superconducting thin film 2 is pseudo-patterned. For this reason, the two terminal portions 4 and 4 in the superconducting state are in a state of being very close to each other via the gap portion 3 having no superconducting property or inferior superconducting property. Therefore, if the width of the gap 3 is made sufficiently small, the two terminals 4 and 4 will be
Thus, they are weakly coupled to each other through, and Josephson junction characteristics are exhibited at both ends of the gap 3. In fact
The present inventors have confirmed that they show Josephson characteristics as a result of measuring the current-voltage characteristics between the two terminal portions 4 and 4 by connecting the lead electrodes to the two terminal portions 4 and 4. Furthermore, in the method for manufacturing the Josephson device of the present invention,
Since it is possible to change the bonding state in the gap 3 by changing the hydrogen ion irradiation conditions and the oxidation treatment conditions, it is possible to control the desired Josephson junction with good controllability by adjusting such conditions. It can be manufactured with good reproducibility.
【００１７】（実施例２）図３（ａ）は本発明に係るジ
ョセフソン素子の製造方法の他の実施例を示す平面図、
図２（ｂ）はその要部断面図である。(Embodiment 2) FIG. 3A is a plan view showing another embodiment of the method for manufacturing a Josephson device according to the present invention,
FIG. 2B is a sectional view of the main part.
【００１８】図３に示すように、例えばＭｇＯ、ＬａＡ
ｌＯ3 等の誘電体基板５を用い、その表面に部分的にエ
ッチング等を施すことにより、段差部分６によって２つ
の平面部分７、７が分離されるように表面加工を行う。
そして、この表面上に金属酸化物超伝導薄膜８を形成す
る。金属酸化物超伝導薄膜８としてＹＢａ2 Ｃｕ3 Ｏ x
系やＢｉ2 Ｓｒ2 Ｃａ2 Ｃｕ3 Ｏx 系の超伝導材料を用
いれば、高周波スパッタリング法、レーザーアブレーシ
ョン法などによって高品質な薄膜を容易に形成すること
ができる。As shown in FIG. 3, for example, MgO, LaA
103Dielectric substrate 5 such as
2 by the step portion 6 by applying
The surface processing is performed so that the flat surface portions 7, 7 are separated.
Then, the metal oxide superconducting thin film 8 is formed on this surface.
It YBa as the metal oxide superconducting thin film 82Cu3O x
System and Bi2Sr2Ca2Cu3OxFor superconducting materials
High frequency sputtering method, laser ablation
Easy to form high quality thin film
You can
【００１９】以上のようにして金属酸化物超伝導薄膜８
を形成した後、例えば、紫外線フォトレジストを用いた
フォトリソグラフィーとイオンビームエッチングとを組
み合わせて、２つの端子部９、９が段差部分６で接続さ
れるような形状にパターン化する（図３（ａ）の斜線部
分）。このように段差部分６を介して形成した金属酸化
物超伝導薄膜８においては、段差部分６の上に堆積した
部分は、段差部分６の基板表面が傾斜しているために他
の部分に比べて膜厚が薄くなる。また、特に基板５が単
結晶の場合には、段差部分６の基板表面での原子の並び
が不規則となるため、その上に形成された金属酸化物超
伝導薄膜８の結晶性は、平面部分７、７に形成された金
属酸化物超伝導薄膜８の結晶性よりも劣る。このため、
超伝導状態にある２つの端子部９、９が、超伝導特性を
有しないか又は超伝導特性の劣った接合部１０を介して
互い非常に接近した状態となる。As described above, the metal oxide superconducting thin film 8
After the formation of, the photolithography using an ultraviolet photoresist and the ion beam etching are combined to form a pattern in which the two terminal portions 9 and 9 are connected at the step portion 6 (see FIG. 3 ( The shaded area in a)). In the metal oxide superconducting thin film 8 thus formed via the step portion 6, the portion deposited on the step portion 6 is more inclined than the other portions because the substrate surface of the step portion 6 is inclined. And the film thickness becomes thinner. In particular, when the substrate 5 is a single crystal, the arrangement of atoms on the substrate surface of the step portion 6 becomes irregular, so that the crystallinity of the metal oxide superconducting thin film 8 formed thereon is flat. It is inferior to the crystallinity of the metal oxide superconducting thin film 8 formed in the portions 7, 7. For this reason,
The two terminal portions 9, 9 in the superconducting state are in a state of being very close to each other via the joint 10 having no superconducting property or poor superconducting property.
【００２０】しかし、接合部１０にジョセフソン効果を
発揮させるためには、段差部分６の幅をコヒーレンス長
程度に十分狭くするか、又は段差部分６の幅がある程度
広いときには、接合部１０の超伝導特性を精度良く制御
しなければならない。金属酸化物超伝導薄膜８のコヒー
レンス長は通常数ｎｍ程度であるから、段差部分６をコ
ヒーレンス長程度の幅で形成することは実際上非常に困
難である。従って、ジョセフソン素子を作製するに当た
っては、段差部分６の上の接合部１０の超伝導特性を精
度良く制御する必要がある。However, in order to exert the Josephson effect on the joint portion 10, the width of the step portion 6 is made sufficiently narrow to the coherence length, or when the width of the step portion 6 is wide to some extent, the superposition of the joint portion 10 is increased. The conduction characteristics must be controlled accurately. Since the metal oxide superconducting thin film 8 usually has a coherence length of about several nm, it is actually very difficult to form the step portion 6 with a width of about the coherence length. Therefore, in manufacturing the Josephson element, it is necessary to accurately control the superconducting property of the junction 10 on the step portion 6.
【００２１】そこで、図３に示す素子構造を作製した後
に、金属酸化物超伝導薄膜８の表面に水素イオンを照射
すると共に、金属酸化物超伝導薄膜８に酸化処理を施し
た。水素イオン照射及び酸化処理の方法は実施例１に記
載したものと同様である。また、水素イオン照射及び酸
化処理の条件は、実施例１と多少の差異はあるが、基本
的には同程度で有効である。この処理によって、接合部
１０を含む金属酸化物超伝導薄膜８の超伝導特性が向上
するが、照射条件又は酸化処理の条件を変えることによ
り、その特性を精度良く制御することが可能となる。従
って、所望のジョセフソン特性を制御性良く、しかも再
現性良く実現することができる。Therefore, after the element structure shown in FIG. 3 was produced, the surface of the metal oxide superconducting thin film 8 was irradiated with hydrogen ions and the metal oxide superconducting thin film 8 was subjected to an oxidation treatment. The methods of hydrogen ion irradiation and oxidation treatment are the same as those described in Example 1. The conditions of the hydrogen ion irradiation and the oxidation treatment are basically the same but effective, although there are some differences from those of the first embodiment. By this treatment, the superconducting property of the metal oxide superconducting thin film 8 including the joint portion 10 is improved, but by changing the irradiation condition or the oxidizing condition, the property can be controlled with high accuracy. Therefore, desired Josephson characteristics can be realized with good controllability and reproducibility.
【００２２】尚、水素イオンは、少なくとも接合部１０
に照射すればよく、必ずしも端子部９、９を含めた金属
酸化物超伝導薄膜８の全面に照射する必要はない。ま
た、本実施例２においては、端子部９、９をパターン化
した場合について説明したが、必ずしもこのようにパタ
ーン化して端子部９を形成する必要はなく、金属酸化物
超伝導薄膜８を形成する際に基板５の表面にメタルマス
クなどを置いて薄膜を形成してもよい。また、全くパタ
ーン化せずに、平面部分７、７の全体を端子部９、９と
して、作製プロセスの簡略化を図ることもできる。但
し、接合部１０の横方向の幅が非常に大きくなるので、
所望のジョセフソン効果を得るためには、水素イオンの
照射条件や酸化処理の条件をより精度良く設定する必要
がある。The hydrogen ions are at least bonded to the joint 10.
It is sufficient to irradiate the entire surface of the metal oxide superconducting thin film 8 including the terminal portions 9 and 9. Further, although the case where the terminal portions 9 are patterned is described in the second embodiment, it is not always necessary to form the terminal portion 9 by patterning in this way, and the metal oxide superconducting thin film 8 is formed. At this time, a metal mask or the like may be placed on the surface of the substrate 5 to form a thin film. Further, it is also possible to simplify the manufacturing process by using the entire plane portions 7 and 7 as the terminal portions 9 and 9 without patterning at all. However, since the lateral width of the joint portion 10 becomes extremely large,
In order to obtain the desired Josephson effect, it is necessary to more accurately set the hydrogen ion irradiation conditions and the oxidation treatment conditions.
【００２３】また、上記実施例１、２においては、金属
酸化物超伝導体としてＹＢａ2 Ｃｕ 3 Ｏx 系やＢｉ2 Ｓ
ｒ2 Ｃａ2 Ｃｕ3 Ｏx 系の材料を例に挙げて説明した
が、必ずしもこれらの材料に限定されるものではなく、
金属酸化物超伝導薄膜としては、Ａ−Ｂ−Ｃｕ−Ｏ複合
化合物であれば同様に有効である。但し、ＡはＳｃ、
Ｙ、Ｌａ及びＬａ系列元素（原子番号５７、５９〜６
０、６２〜７１）から選ばれる少なくとも１種の元素、
ＢはＢａ、Ｓｒなどの６ａ族元素から選ばれる少なくと
も１種の元素である。また、Ａ、Ｂ元素とＣｕ元素の濃
度比としては、前記（数１）で示す範囲内にあれば、多
少の超伝導特性の差はあるものの、基本的には本発明に
おいて有効である。また、金属酸化物超伝導薄膜として
Ｂｉ−Ｓｒ−Ｃａ−Ｃｕ−Ｏ又はＴｌ−Ｂａ−Ｃａ−Ｃ
ｕ−Ｏ複合化合物を用いても、同様に有効である。これ
らの超伝導材料の中には、超伝導臨界温度（Ｔc ）が１
００ケルビンを超えるものも含まれており、実用上も有
効性が高い。Further, in the above-mentioned first and second embodiments, the metal
YBa as an oxide superconductor2Cu 3OxSystem and Bi2S
r2Ca2Cu3OxI explained by taking the material of the system as an example
However, it is not necessarily limited to these materials,
As a metal oxide superconducting thin film, an AB-Cu-O composite
Compounds are similarly effective. However, A is Sc,
Y, La and La series elements (atomic number 57, 59 to 6)
0, 62-71), at least one element selected from
B is at least selected from the 6a group elements such as Ba and Sr.
Is also an element. Also, the concentration of A and B elements and Cu element
If the degree ratio is within the range shown in (Equation 1), the
Although there is a slight difference in superconducting properties, the present invention is basically
Is effective. Also, as a metal oxide superconducting thin film
Bi-Sr-Ca-Cu-O or Tl-Ba-Ca-C
The same effect is obtained by using the u-O composite compound. this
Among these superconducting materials, the superconducting critical temperature (Tc) Is 1
Some of them exceed 00 Kelvin, which is also practical
Highly effective.
【００２４】[0024]
【発明の効果】以上説明したように、本発明に係るジョ
セフソン素子の第１又は第２の製造方法によれば、均一
に薄膜化した金属酸化物超伝導薄膜を用い、水素イオン
の照射と酸化処理を基本とするプロセスによってジョセ
フソン接合を形成することができる。水素イオンの照射
による金属酸化物超伝導薄膜の処理は制御性が良く、し
かも簡単であるため、従来行われてきた積層構造を利用
して作製する方法に比べ、極めて簡単なプロセスでジョ
セフソン素子を作製することができる。また、基本的に
平面構造によってジョセフソン接合が形成されるので、
他の電子デバイスや他の材料との集積化の際などに特に
有効である。また、本発明のジョセフソン素子の製造方
法はＳＱＵＩＤ（磁界検出素子）や高周波ミキサー等の
各種の超伝導デバイスの製造に応用することができる。
特に、この種の金属酸化物超伝導体の超伝導臨界温度
（Ｔc ）が室温になる可能性もあるため、実用の範囲が
広く本発明の工業的価値は高い。As described above, according to the first or second method of manufacturing a Josephson device according to the present invention, a uniform thin metal oxide superconducting thin film is used and irradiation with hydrogen ions is performed. A Josephson junction can be formed by an oxidation-based process. Since the treatment of the metal oxide superconducting thin film by irradiation of hydrogen ions has good controllability and is simple, the Josephson device can be manufactured by an extremely simple process as compared with the conventional method using the laminated structure. Can be produced. Also, since the Josephson junction is basically formed by the planar structure,
It is particularly effective when integrated with other electronic devices and other materials. Further, the method for manufacturing the Josephson device of the present invention can be applied to the manufacture of various superconducting devices such as SQUID (magnetic field detection device) and high frequency mixer.
In particular, since the superconducting critical temperature (T c ) of this kind of metal oxide superconductor may be room temperature, the practical range is wide and the industrial value of the present invention is high.
【図面の簡単な説明】[Brief description of drawings]
【図１】（ａ）は本発明に係るジョセフソン素子の製造
方法の一実施例を示す平面図、（ｂ）はその要部断面図
である。FIG. 1A is a plan view showing an embodiment of a method for manufacturing a Josephson device according to the present invention, and FIG.
【図２】同じ金属酸化物超伝導薄膜に対して、水素イオ
ンの照射を行った場合（Ａ）と、行わなかった場合
（Ｂ）の臨界電流密度の温度変化を示す図である。FIG. 2 is a diagram showing a temperature change of the critical current density when the same metal oxide superconducting thin film is irradiated with hydrogen ions (A) and when not irradiated (B).
【図３】（ａ）は本発明に係るジョセフソン素子の製造
方法の他の実施例を示す平面図、（ｂ）はその要部断面
図である。FIG. 3A is a plan view showing another embodiment of the method for manufacturing a Josephson device according to the present invention, and FIG.
１、５ 基板 ２、８ 金属酸化物超伝導薄膜 ３ 間隙部 ４、９ 端子部 ６ 段差部分 ７ 平面部分 １０ 接合部 1, 5 Substrate 2, 8 Metal oxide superconducting thin film 3 Gap 4, 9 Terminal part 6 Step part 7 Plane part 10 Joint part
Claims (4)
し、前記金属酸化物超伝導薄膜上の微小な間隙部で分離
された２つの端子部に選択的に水素イオンを照射し、前
記金属酸化物超伝導薄膜に酸化処理を施すジョセフソン
素子の製造方法。1. A metal oxide superconducting thin film is formed on a substrate, and two terminal portions separated by a minute gap on the metal oxide superconducting thin film are selectively irradiated with hydrogen ions. A method for manufacturing a Josephson device in which a metal oxide superconducting thin film is oxidized.
て分離された２つの平面部分とを有する基板上に、前記
段差部分及び前記２つの平面部分を含む領域に金属酸化
物超伝導薄膜を形成し、前記２つの平面部分上の金属酸
化物超伝導薄膜を端子部とし、前記段差部分上の金属酸
化物超伝導薄膜を接合部とするジョセフソン素子の製造
方法であって、少なくとも前記接合部に水素イオンを照
射し、前記金属酸化物超伝導薄膜に酸化処理を施すこと
を特徴とするジョセフソン素子の製造方法。2. A metal oxide superconducting thin film is formed in a region including the step portion and the two plane portions on a substrate having a step portion on the surface and two plane portions separated by the step portion. A method for manufacturing a Josephson device, wherein the metal oxide superconducting thin film on the two plane portions serves as a terminal portion and the metal oxide superconducting thin film on the step portion serves as a joint portion, and at least the joint portion. A method for manufacturing a Josephson device, characterized in that the metal oxide superconducting thin film is irradiated with hydrogen ions to oxidize the metal oxide superconducting thin film.
ｕ−Ｏ複合化合物を用いる請求項１又は２に記載のジョ
セフソン素子の製造方法。但し、ＡはＳｃ、Ｙ、Ｌａ及
びＬａ系列元素（原子番号５７、５９〜６０、６２〜７
１）から選ばれる少なくとも１種の元素、Ｂは６ａ族元
素から選ばれる少なくとも１種の元素であり、Ａ、Ｂ元
素とＣｕ元素の濃度比は下記（数１）によって表記され
る。 【数１】 3. A ABC as a metal oxide superconducting thin film.
The method for manufacturing a Josephson device according to claim 1, wherein a u-O composite compound is used. However, A is Sc, Y, La and La series elements (atomic number 57, 59-60, 62-7).
At least one element selected from 1), B is at least one element selected from Group 6a elements, and the concentration ratio of the A and B elements to the Cu element is expressed by the following (Equation 1). [Equation 1]
−Ｃａ−Ｃｕ−ＯもしくはＴｌ−Ｂａ−Ｃａ−Ｃｕ−Ｏ
複合化合物を用いる請求項１又は２に記載のジョセフソ
ン素子の製造方法。4. A Bi-Sr as a metal oxide superconducting thin film.
-Ca-Cu-O or Tl-Ba-Ca-Cu-O
The method for producing a Josephson device according to claim 1, wherein a composite compound is used.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5128753A JPH06338639A (en) | 1993-05-31 | 1993-05-31 | Manufacture of josephson element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5128753A JPH06338639A (en) | 1993-05-31 | 1993-05-31 | Manufacture of josephson element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06338639A true JPH06338639A (en) | 1994-12-06 |
Family
ID=14992618
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5128753A Pending JPH06338639A (en) | 1993-05-31 | 1993-05-31 | Manufacture of josephson element |
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| Country | Link |
|---|---|
| JP (1) | JPH06338639A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2717253C1 (en) * | 2019-09-18 | 2020-03-19 | Федеральное государственное бюджетное учреждение науки Институт физики твердого тела Российской академии наук (ИФТТ РАН) | Superconducting circuit with weak coupling section |
-
1993
- 1993-05-31 JP JP5128753A patent/JPH06338639A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2717253C1 (en) * | 2019-09-18 | 2020-03-19 | Федеральное государственное бюджетное учреждение науки Институт физики твердого тела Российской академии наук (ИФТТ РАН) | Superconducting circuit with weak coupling section |
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