JPH02249284A - Josephson element - Google Patents
Josephson elementInfo
- Publication number
- JPH02249284A JPH02249284A JP1069925A JP6992589A JPH02249284A JP H02249284 A JPH02249284 A JP H02249284A JP 1069925 A JP1069925 A JP 1069925A JP 6992589 A JP6992589 A JP 6992589A JP H02249284 A JPH02249284 A JP H02249284A
- Authority
- JP
- Japan
- Prior art keywords
- small hole
- al8o3
- thin film
- film
- forming
- 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
- 239000010409 thin film Substances 0.000 claims abstract description 27
- 239000010408 film Substances 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000001312 dry etching Methods 0.000 abstract description 2
- 241000238366 Cephalopoda Species 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 5
- 229910052593 corundum Inorganic materials 0.000 description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 description 5
- BYFGZMCJNACEKR-UHFFFAOYSA-N aluminium(i) oxide Chemical compound [Al]O[Al] BYFGZMCJNACEKR-UHFFFAOYSA-N 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Chemical compound O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 235000012149 noodles Nutrition 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 239000002887 superconductor Substances 0.000 description 1
Landscapes
- Measuring Magnetic Variables (AREA)
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
本発明は１例えばスクイド（ＳＱＵＩＤ ）に設けられ
るＮｂ薄膜ポイントコンタクト形のジョセフソン素子に
関するものであり、更に詳しくはコンタクト部の改良に
関するものである。[Detailed Description of the Invention] <Field of Industrial Application> The present invention relates to an Nb thin film point contact type Josephson element provided in, for example, a SQUID, and more specifically relates to improvement of the contact portion. be.
〈従来の技術〉
超伝導体間の弱い接合部分をジョセフソン接合といい、
この弱い部分を含んで構成したリングを一般的にスクイ
ドと呼んでいる。スクイドは高感美ヤ
度の磁束計、磁束勾配凰、電流計、低温用温度計など各
種の分野に応用が可能である。<Conventional technology> The weak junction between superconductors is called a Josephson junction.
A ring made up of this weak part is generally called a SQUID. SQUID can be applied to various fields such as high-sensitivity magnetometers, magnetic flux gradient screens, ammeters, and low-temperature thermometers.
この様な薄膜スクイドに用いられるジョセフソン素子と
してはマイクロブリッジ型やトンネル接合型、ポイント
コンタクト型と呼ばれるものがあるが、マイクロブリッ
ジ型は微細加工技術による制約、平面構造上の理由等に
より良好なジョセフソン素子を得るのが困雑であり、ま
た、トンネル接合型は接合間の容量の為にスクイド動作
に有害となる接合のＩ−Ｖ特性ヒステリシスか現われこ
のヒステリシスを打消すためのシャント抵抗が必要とな
るので製造工程が複雑になる。Josephson elements used in such thin-film SQUIDs include microbridge type, tunnel junction type, and point contact type, but the microbridge type is not suitable due to restrictions due to microfabrication technology and due to reasons such as planar structure. It is difficult to obtain a Josephson element, and in the tunnel junction type, due to the capacitance between the junctions, I-V characteristic hysteresis of the junction appears, which is harmful to SQUID operation, and a shunt resistor is required to cancel this hysteresis. This complicates the manufacturing process.
ポイントコンタクト型は上記の欠点を解決したもので１
例えば第３図に示すものが知られている。The point contact type solves the above drawbacks.1
For example, the one shown in FIG. 3 is known.
（ａ）は斜視図、（ｂ）は（ａ）のＡ−Ａ断面図である
。これらの図において１はサファイア（Ａ１２０３ ）
等の単結晶基板、２は下部電極としてのＮｂ薄膜、３は
同材質の上部電極、４はＮｂ薄膜の表面を酸化させて形
成した絶縁膜、５は酸化膜に形成した小穴を結合して設
けられたポイントコンタクト部（ジョセフソン結合）で
ある。(a) is a perspective view, and (b) is a sectional view taken along the line AA in (a). In these figures, 1 is sapphire (A1203)
2 is a Nb thin film as a lower electrode, 3 is an upper electrode made of the same material, 4 is an insulating film formed by oxidizing the surface of the Nb thin film, and 5 is a small hole formed in the oxide film. This is a point contact section (Josephson connection) provided.
上記構成によれば結合部の長さ０４ｅａｋ Ｌｉｎｋ長
）をＮｂの酸化膜の厚さで決めることが出来るので酸化
時間を調整する事によりその厚さを任意の寸法に精度よ
く形成することが出来る。According to the above structure, the length of the bonding part (04eak Link length) can be determined by the thickness of the Nb oxide film, so by adjusting the oxidation time, the thickness can be precisely formed to any dimension. .
〈発明が解決しようとする課題〉
しかしながら、上記構成においては小穴の径が０．５〜
１μｍ程度と極めて小さな寸法であるため１接合部の周
囲（Ｂで示す部分〉に存在するＮｂ２Ｏ５やＮｂ低級酸
化物により接合部近傍の酸化状態により、接合特性がば
らついてしまうという問題点があった。<Problem to be solved by the invention> However, in the above configuration, the diameter of the small hole is 0.5~
Since the size is extremely small, approximately 1 μm, there was a problem in that the bonding characteristics varied depending on the oxidation state near the bond due to Nb2O5 and Nb lower oxides present around the bond (the area indicated by B). .
本発明は上記従来技術の問題点に鑑みて成されたもので
、絶縁層としてＡｊ’２０３を用いる事によりＮｂ酸化
物の影響をなくシ、製作時の再現性および安定性の向上
をはかったものである。The present invention was made in view of the problems of the prior art described above, and by using Aj'203 as an insulating layer, the influence of Nb oxide is eliminated, and the reproducibility and stability during manufacturing are improved. It is something.
〈課題を解決するための手段〉
上記課題を解決するための本発明の構成は、基板と、こ
の基板上に形成された第１のＮｂ薄膜と。<Means for Solving the Problems> The structure of the present invention for solving the above problems includes a substrate and a first Nb thin film formed on the substrate.
このＮｂ薄膜の上に積層されたＡｌおよび第１のＡ１２
０３薄膜と、前記Ａ１および第１のＡｌ２Ｏ３を貫通し
て形成された小穴と、前記小穴の内面に形成された第２
のＡ １２０３膜と１前記小穴を含む第１のＡｌ ２０
３膜上に第２のＮｂ層を形成した事を特徴とするもので
ある。Al and first A12 layered on this Nb thin film
03 thin film, a small hole formed through the A1 and the first Al2O3, and a second hole formed on the inner surface of the small hole.
A first Al 20 film containing an A 1203 membrane and one small hole.
This is characterized in that a second Nb layer is formed on the three films.
く実方麺例〉
第１図は本発明の一実施例を示す斜視図（ａ）（ａ＞の
Ａ−Ａ″断面図（ｂ）である。図において第３図と同一
要素には同一符号を付して説明は省略するが、１０はＡ
ｌ膜、１１は第１のＡｌ２Ｏ３膜、１２は第２のＡｌ２
Ｏ，＠である。Example of Kujikata Noodles> Fig. 1 is a perspective view (a) and a sectional view (b) of A-A'' of (a) showing an embodiment of the present invention. In the figure, the same elements as those in Fig. Although the explanation will be omitted by adding a symbol, 10 is A.
1 film, 11 is the first Al2O3 film, 12 is the second Al2 film.
O, @.
第２図（ａ）〜（ｅ）は上記ジョセフソン素子の製作工
程の概略を示すものである。FIGS. 2(a) to 2(e) schematically show the manufacturing process of the Josephson element.
工程（ａ）
基板上に第１のＮｂ、Ａｌおよび第１のＡｌ２Ｏコの薄
膜を順次スパッタ装置により積層する。Step (a) First thin films of Nb, Al, and first Al2O are sequentially laminated on a substrate using a sputtering device.
ここでＮｂとＡｌ２Ｏ３の間にＡ１層を設けたのは両層
の親和性をはかる為である。各層の膜厚は５０〜１１０
０ｎ程度とする。The reason why the A1 layer is provided between Nb and Al2O3 is to measure the affinity of both layers. The thickness of each layer is 50 to 110
It is set to about 0n.
工程（ｂ）
前記Ａｌおよび第１のＡ１２０ｚ膜を貫通してＮｂ１１
ｇに達する小穴を形成する。この小穴はフォトリソグラ
フィの技術や電子ビーム露光装置を用いて膜厚とエツチ
ング速度との関係を考慮しながら穴の底部がＮｂ膜に達
するまで行い０．５〜１μｍ程度の径に形成する。Step (b) Penetrating the Al and first A120z films to form Nb11
Form a small hole reaching g. This small hole is formed to a diameter of about 0.5 to 1 .mu.m using a photolithography technique or an electron beam exposure device, taking into consideration the relationship between film thickness and etching rate, until the bottom of the hole reaches the Nb film.
工程（ｃ）
前記小穴を含む第１のＡｌ２Ｏ３薄膜上に１゜Ｏｎｍ程
度に第２のＡｌ２Ｏ，薄膜を形成する。Step (c) A second Al2O thin film is formed to a thickness of about 1° Onm on the first Al2O3 thin film including the small holes.
この工程もスパッタ装置により行う。This step is also performed using a sputtering device.
工程（ｄ）
前記第２のＡ１２０ｗ薄膜を異方性ドライエツチングの
技術を用いて小穴の側面に形成された第２のＡ ｌ ２
０３のみを残して除去する。この加工により小穴の側壁
には９０ｎｍ程度のＡｌ２Ｏ３が形成される。Step (d) A second A120w thin film is formed on the side surface of the small hole using an anisotropic dry etching technique.
Remove, leaving only 03. By this processing, Al2O3 with a thickness of about 90 nm is formed on the side wall of the small hole.
工程（ｅ）
前記小穴を含む第１のＡｌ ２０３薄膜上に３゜Ｏｎｍ
程度のＮｂの薄膜をスパッタにより形成する。Step (e) 3° Onm on the first Al 203 thin film including the small hole.
A thin Nb film of about 100% is formed by sputtering.
〈発明の効果〉
以上実施例とともに具体的に説明したように本発明によ
れば、絶縁層としてのＡｉ’２０３薄膜を小穴の側面に
も形成したので
■ Ｎｂ膜の酸化膜を用いた場合に比較して製作時の再
現性や特性の安定したジョセフソン結合を得ることが出
来る。<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the Ai'203 thin film as an insulating layer is also formed on the side surface of the small hole. In comparison, a Josephson coupling with stable reproducibility and characteristics during fabrication can be obtained.
■ 小穴に側壁を形成した後第２のＮｂ薄膜を形成して
いるのでセルファライン加工となり、接合部の面積を小
さくすることが出来る。(2) Since the second Nb thin film is formed after forming the side wall in the small hole, self-line processing is performed, and the area of the joint can be reduced.
第１図は本発明のジョセフソン素子の一実施例を示す斜
視図（ａ）および（ａ＞のＡ−Ａ″断面図、第２図は概
略製作工程を示す説明図、第３図は従来例を示す斜視図
（ａ）および（ａ）のＡ−Ａ”断面図である。
１・・・基板、２・・・第１のＮｂＮＨ，３・・・第２
のＮｂ薄Ｍ、４・・・小穴、１０・・・Ａ／薄膜、１１
・・・第１のＡ Ｉ ２０３ Ｍ、 １２−第２のＡｌ
２Ｏ３゜第
図
第
図Fig. 1 is a perspective view (a) and a sectional view taken along line A-A'' of (a) showing one embodiment of the Josephson element of the present invention, Fig. 2 is an explanatory diagram showing a schematic manufacturing process, and Fig. 3 is a conventional They are a perspective view (a) and a cross-sectional view taken along line A-A” of (a) showing an example. 1...Substrate, 2...First NbNH, 3...Second
Nb thin M, 4...small hole, 10...A/thin film, 11
...first AI 203 M, 12-second Al
2O3゜Fig.Fig.
Claims (1)
のＮｂ薄膜の上に積層されたＡｌおよび第１のＡｌ＿２
Ｏ＿３薄膜と、前記Ａｌおよび第１のＡｌ＿２Ｏ＿３を
貫通して形成された小穴と、前記小穴の内面に形成され
た第２のＡｌ＿２Ｏ＿３膜と、前記小穴を含む第１のＡ
ｌ＿２Ｏ＿３膜上に第２のＮｂ層を形成した事を特徴と
するジョセフソン素子。A substrate, a first Nb thin film formed on this substrate, Al laminated on this Nb thin film, and a first Al_2
an O_3 thin film, a small hole formed through the Al and the first Al_2O_3, a second Al_2O_3 film formed on the inner surface of the small hole, and a first Al_2O_3 film including the small hole.
A Josephson device characterized by forming a second Nb layer on an l_2O_3 film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1069925A JPH02249284A (en) | 1989-03-22 | 1989-03-22 | Josephson element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1069925A JPH02249284A (en) | 1989-03-22 | 1989-03-22 | Josephson element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02249284A true JPH02249284A (en) | 1990-10-05 |
Family
ID=13416753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1069925A Pending JPH02249284A (en) | 1989-03-22 | 1989-03-22 | Josephson element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02249284A (en) |
-
1989
- 1989-03-22 JP JP1069925A patent/JPH02249284A/en active Pending
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