JPH0613672A - Manufacture of josephson junction device - Google Patents
Manufacture of josephson junction deviceInfo
- Publication number
- JPH0613672A JPH0613672A JP4170841A JP17084192A JPH0613672A JP H0613672 A JPH0613672 A JP H0613672A JP 4170841 A JP4170841 A JP 4170841A JP 17084192 A JP17084192 A JP 17084192A JP H0613672 A JPH0613672 A JP H0613672A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- lower electrode
- film
- bridge
- josephson junction
- 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
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、生体磁界等の極微弱磁
界を計測するためのＳＱＵＩＤ等に用いられる、準平面
型のジョセフソン接合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 quasi-planar type Josephson junction element used for SQUID or the like for measuring an extremely weak magnetic field such as a biomagnetic field.
【０００２】[0002]
【従来の技術】ジョセフソン接合部を有する素子のう
ち、準平面型の素子は、図２にその斜視図を例示するよ
うに、基板１上に超電導体薄膜製の下部電極２を形成
し、その上に絶縁層５を介して超電導体薄膜製の上部電
極３を形成して、この上部電極３と下部電極２の表面の
双方に跨がるような超電導体薄膜製のブリッジ４を形成
し、このブリッジ４によって下部電極２と上部電極３と
をウィークに接合した構造を採る。2. Description of the Related Art Among devices having a Josephson junction, a quasi-planar device has a lower electrode 2 made of a superconductor thin film formed on a substrate 1 as shown in a perspective view of FIG. An upper electrode 3 made of a superconductor thin film is formed on the insulating layer 5, and a bridge 4 made of a superconductor thin film is formed so as to extend over both surfaces of the upper electrode 3 and the lower electrode 2. The structure in which the lower electrode 2 and the upper electrode 3 are weakly joined by the bridge 4 is adopted.
【０００３】このような準平面型のジョセフソン接合素
子では、極めて微小な長さを要求されるウィークリンク
長が、上部電極３と下部電極２の間に介在する絶縁層５
の膜厚によって決まるため、このウィークリンク長を平
面上での微細加工に頼る平面型のジョセフソン接合素子
に比して、再現性よく良好な性能のジョセフソン接合素
子が得られるという利点がある。In such a quasi-planar type Josephson junction element, the weak link length, which requires an extremely small length, has an insulating layer 5 interposed between the upper electrode 3 and the lower electrode 2.
Since it is determined by the film thickness of the, the weak link length has the advantage that a Josephson junction element with good reproducibility and good performance can be obtained compared to a planar Josephson junction element that relies on microfabrication on a plane. .
【０００４】以上のような準平面型のジョセフソン接合
素子の製造するときには、通常、基板１上に下部電極２
用の超電導体薄膜を成膜した後、例えばリフトオフ法等
によるパターニングで下部電極２を形成した後、その上
に絶縁層５および上部電極３を形成し、更にその上に超
電導体薄膜を成膜した後に、電子ビーム露光等によって
ブリッジ４のパターニングを行う等の方法が採用されて
いる。When manufacturing the quasi-planar type Josephson junction device as described above, the lower electrode 2 is usually formed on the substrate 1.
After forming a superconducting thin film for use as a film, a lower electrode 2 is formed by patterning by, for example, a lift-off method, an insulating layer 5 and an upper electrode 3 are formed thereon, and a superconducting thin film is further formed thereon. After that, a method of patterning the bridge 4 by electron beam exposure or the like is adopted.
【０００５】[0005]
【発明が解決しようとする課題】以上のような従来の製
造方法においては、下部電極２を形成するための超電導
体薄膜の成膜後、ブリッジ４を形成するための超電導体
薄膜を成膜するまでの間に多くの工程が入るため、下部
電極２用の超電導体薄膜の表面が酸化して酸化層が形成
される。このため、ブリッジ４と下部電極２との間の超
電導接合が困難となるという問題があった。In the conventional manufacturing method as described above, a superconductor thin film for forming the bridge 4 is formed after the superconductor thin film for forming the lower electrode 2 is formed. Since many steps are performed up to, the surface of the superconductor thin film for the lower electrode 2 is oxidized and an oxide layer is formed. Therefore, there is a problem that it becomes difficult to perform superconducting bonding between the bridge 4 and the lower electrode 2.
【０００６】本発明の目的は、下部電極２とブリッジ４
とを確実に超電導接合することのできるジョセフソン接
合素子の製造方法を提供することにある。The object of the present invention is to provide a lower electrode 2 and a bridge 4.
It is an object of the present invention to provide a method of manufacturing a Josephson junction element capable of reliably superconducting and.
【０００７】[0007]
【課題を解決するための手段】上記の目的を達成するた
め、本発明のジョセフソン接合素子の製造方法は、下部
電極を形成するための超電導体薄膜を成膜後、同一真空
中でその薄膜の表面に金属薄膜を連続成膜し、この金属
薄膜の露出部分を、ブリッジ用の超電導体薄膜を成膜す
る直前にエッチングすることによって特徴づけられる。In order to achieve the above object, a method for manufacturing a Josephson junction element according to the present invention comprises a superconducting thin film for forming a lower electrode, which is then formed in the same vacuum. It is characterized in that a metal thin film is continuously formed on the surface of and the exposed portion of the metal thin film is etched immediately before forming a superconducting thin film for a bridge.
【０００８】[0008]
【作用】下部電極用の超電導体薄膜を成膜した後、次の
工程に入る前に、この超電導体薄膜を成膜した同一真空
中での連続成膜により、その表面を金属薄膜で覆ってお
くことで、この金属薄膜は下部電極用の超電導体薄膜の
表面の酸化防止膜として機能する。この金属薄膜とし
て、例えばAl等、酸化が進みにくく、エッチングにより
簡単に剥離できる金属材料を用い、ブリッジ用の超電導
体薄膜の成膜の直前にこの金属薄膜を除去することによ
り、下部電極はその表面に酸化膜が形成されていない状
態でブリッジに対して接合される。After the superconductor thin film for the lower electrode is formed, before the next step, the surface of the superconductor thin film is covered with a metal thin film by continuous film formation in the same vacuum. By leaving this, the metal thin film functions as an antioxidant film on the surface of the superconductor thin film for the lower electrode. As the metal thin film, for example, a metal material such as Al that is hard to oxidize and can be easily peeled off by etching is used.By removing the metal thin film immediately before forming the superconducting thin film for the bridge, the lower electrode is It is joined to the bridge in the state where no oxide film is formed on the surface.
【０００９】[0009]
【実施例】図１は模式的断面図で示す本発明実施例の手
順説明図である。基板１を洗浄後、（Ａ）に示すように
下部電極２を作成するためのフォトレジスト（例えば商
品名ＡＺ１５４３Ｅ）６０をパターニングする。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a procedure explanatory view of an embodiment of the present invention shown in a schematic sectional view. After cleaning the substrate 1, a photoresist (for example, trade name AZ1543E) 60 for forming the lower electrode 2 is patterned as shown in FIG.
【００１０】次に、基板１を成膜用の真空チャンバ内に
配置し、フォトレジスト６０の上方から、下部電極用の
超電導体薄膜２０（例えばNb）を２５００Å程度の厚さ
で成膜した後、同一の真空中で、Al薄膜７０を５０Å程
度の厚さで連続成膜する。この状態を（Ｂ）に示す。Then, the substrate 1 is placed in a vacuum chamber for film formation, and a superconductor thin film 20 (for example, Nb) for the lower electrode is formed from above the photoresist 60 to a thickness of about 2500 Å. In the same vacuum, the Al thin film 70 is continuously formed to a thickness of about 50Å. This state is shown in (B).
【００１１】その後、アセトン中でのリフトオフ法によ
り、（Ｃ）に示すようにフォトレジスト６０およびその
上方の超電導体薄膜２０およびAlを除去することより、
表面がAl薄膜製の酸化防止膜７で覆われた下部電極２を
形成する。Thereafter, by removing the photoresist 60 and the superconductor thin film 20 and Al above it by a lift-off method in acetone as shown in FIG.
A lower electrode 2 whose surface is covered with an antioxidation film 7 made of an Al thin film is formed.
【００１２】次に、上部電極３を形成するためのフォト
レジスト８０をパターニングの後、絶縁層５および上部
電極３を形成するため、Al薄膜５０を２００Å程度の厚
さで成膜するとともに、その上に超電導体薄膜３０（同
じくNb等）を２５００Å程度の厚さで成膜する。この状
態を（Ｄ）に示す。Next, after patterning the photoresist 80 for forming the upper electrode 3, an Al thin film 50 is formed with a thickness of about 200 Å in order to form the insulating layer 5 and the upper electrode 3. A superconducting thin film 30 (also Nb or the like) is formed thereon with a thickness of about 2500Å. This state is shown in (D).
【００１３】その後、アセトン中でのリフトオフ法によ
りフォトレジスト８０とその上のAl薄膜５０および超電
導体薄膜３０を除去し、（Ｅ）に示すように絶縁層５お
よび上部電極３を形成する。ここで、Al薄膜５０は、こ
の工程に至るまでの工程、あるいは大気中における放置
により、その表面が所定深で酸化して AlOX となってお
り、絶縁層５としての機能を持つに至る。このような酸
化は、上述のAl薄膜７０についても同様であるが、いず
れの膜についても酸化は進みにくく、膜全体にまでは至
らない。なお、絶縁層５ようのAl薄膜５０については、
酸化をより完全なものとするために、別途、他部を覆っ
た状態でのプラズマ酸化等の工程を追加することは妨げ
ない。After that, the photoresist 80, the Al thin film 50 and the superconductor thin film 30 thereon are removed by a lift-off method in acetone, and the insulating layer 5 and the upper electrode 3 are formed as shown in FIG. Here, the surface of the Al thin film 50 is oxidized to a predetermined depth and becomes AlO X by the steps up to this step or left in the atmosphere, and the Al thin film 50 has a function as the insulating layer 5. Such oxidation is the same for the above-mentioned Al thin film 70, but it is difficult for any of the films to proceed and the oxidation does not reach the entire film. Regarding the Al thin film 50 such as the insulating layer 5,
In order to make the oxidation more complete, it is not hindered to additionally add a process such as plasma oxidation in a state where the other part is covered.
【００１４】さて、次に、基板１の上方からのArを用い
た逆スパッタによるドライエッチング、あるいはリン酸
中でのウェットエッチングにより、（Ｆ）に示すよう
に、下部電極２の表面に露出している酸化防止膜７０を
除去する。Next, as shown in (F), the surface of the lower electrode 2 is exposed by dry etching by reverse sputtering using Ar from above the substrate 1 or wet etching in phosphoric acid. The antioxidant film 70 that has been removed is removed.
【００１５】そして、その上から、Nb等の超電導体薄膜
を例えば１３０Å程度の厚さで成膜し、電子ビーム露光
によりブリッジパターンを描画し、他部分を逆スパッタ
等によってエッチングして、（Ｇ）に示すようにブリッ
ジ４を形成する。Then, a superconducting thin film of Nb or the like is formed thereon with a thickness of, for example, about 130 Å, a bridge pattern is drawn by electron beam exposure, and the other part is etched by reverse sputtering or the like (G The bridge 4 is formed as shown in FIG.
【００１６】以上の本発明実施例による工程において
は、超電導体薄膜２０は成膜後、ブリッジ４用の超電導
体薄膜を形成するまでの間、酸化防止膜７によってその
表面が覆われているため、他工程や大気中に曝されるこ
とによる酸化が防止される。In the process according to the embodiment of the present invention described above, the surface of the superconductor thin film 20 is covered with the anti-oxidation film 7 after the film formation until the formation of the superconductor thin film for the bridge 4. Oxidation due to exposure to other processes or the atmosphere is prevented.
【００１７】なお、酸化防止膜７の材質としてはAl以外
の金属材料を使用することができるが、酸化が進みにく
く、しかもドライまたはウェットエッチングにより剥離
しやすい材料を用いることが望ましく、特にAlはこのよ
うな条件に叶っており、好適である。Although a metal material other than Al can be used as the material of the anti-oxidation film 7, it is desirable to use a material that is hard to oxidize and easily peels off by dry or wet etching. Such conditions are satisfied, which is preferable.
【００１８】[0018]
【発明の効果】以上説明したように、本発明によれば、
下部電極用の超電導体薄膜の表面を、その薄膜の成膜と
同一の真空中において金属薄膜で被覆するとともに、そ
の状態で絶縁層および上部電極を形成し、ブリッジ形成
用の超電導体薄膜の形成直前に金属薄膜の露出部分をエ
ッチングするから、ブリッジと接合すべき下部電極の表
面に酸化膜が生成されることが防止される。その結果、
下部電極とブリッジとの超電導接合が確実なものとな
り、素子の製造歩留りが向上する。As described above, according to the present invention,
Form the superconductor thin film for bridge formation by covering the surface of the superconductor thin film for the lower electrode with a metal thin film in the same vacuum as the film formation, and then forming the insulating layer and the upper electrode in that state. Since the exposed portion of the metal thin film is etched immediately before, formation of an oxide film on the surface of the lower electrode to be joined to the bridge is prevented. as a result,
The superconducting junction between the lower electrode and the bridge becomes reliable, and the manufacturing yield of the device is improved.
【図１】模式的断面図で示す本発明実施例の手順説明図FIG. 1 is a procedure explanatory view of an embodiment of the present invention shown in a schematic sectional view.
【図２】準平面型ジョセフソン接合素子の構造説明図FIG. 2 is a structural explanatory view of a quasi-planar Josephson junction element.
１ 基板 ２ 下部電極 ３ 上部電極 ４ ブリッジ ５ 酸化膜 ７ 酸化防止膜（Al薄膜) 1 Substrate 2 Lower electrode 3 Upper electrode 4 Bridge 5 Oxide film 7 Antioxidation film (Al thin film)
Claims (1)
成した後、その上方に絶縁層を介して超電導体薄膜製の
上部電極を形成し、次いで上記下部電極と上部電極の双
方の表面に跨がるよう超電導体薄膜製のブリッジを形成
することによって、このブリッジで上記上部電極と下部
電極がウィークに接合された素子を製造する方法におい
て、下部電極を形成するための超電導体薄膜を成膜後、
同一真空中でその薄膜の表面に金属薄膜を連続成膜し、
この金属薄膜の露出部分を、上記ブリッジ用の超電導体
薄膜を成膜する直前にエッチングすることを特徴とする
ジョセフソン接合素子の製造方法。1. A lower electrode made of a superconductor thin film is formed on a substrate, and then an upper electrode made of a superconductor thin film is formed thereabove with an insulating layer interposed therebetween. Then, the surfaces of both the lower electrode and the upper electrode are formed. By forming a bridge made of a superconductor thin film so as to straddle the above, in the method for manufacturing an element in which the upper electrode and the lower electrode are weakly joined by this bridge, a superconductor thin film for forming the lower electrode is formed. After film formation,
A thin metal film is continuously formed on the surface of the thin film in the same vacuum,
A method for manufacturing a Josephson junction device, characterized in that the exposed portion of the metal thin film is etched immediately before the superconducting thin film for the bridge is formed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4170841A JPH0613672A (en) | 1992-06-29 | 1992-06-29 | Manufacture of josephson junction device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4170841A JPH0613672A (en) | 1992-06-29 | 1992-06-29 | Manufacture of josephson junction device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0613672A true JPH0613672A (en) | 1994-01-21 |
Family
ID=15912324
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4170841A Pending JPH0613672A (en) | 1992-06-29 | 1992-06-29 | Manufacture of josephson junction device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0613672A (en) |
-
1992
- 1992-06-29 JP JP4170841A patent/JPH0613672A/en active Pending
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