JPH0517714B2 - - Google Patents
Info
- Publication number
- JPH0517714B2 JPH0517714B2 JP61229536A JP22953686A JPH0517714B2 JP H0517714 B2 JPH0517714 B2 JP H0517714B2 JP 61229536 A JP61229536 A JP 61229536A JP 22953686 A JP22953686 A JP 22953686A JP H0517714 B2 JPH0517714 B2 JP H0517714B2
- Authority
- JP
- Japan
- Prior art keywords
- layer
- superconductor
- tunnel barrier
- nbn
- barrier layer
- 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.)
- Expired - Lifetime
Links
- 239000002887 superconductor Substances 0.000 claims description 79
- 230000004888 barrier function Effects 0.000 claims description 50
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 23
- 229910052751 metal Inorganic materials 0.000 claims description 21
- 239000002184 metal Substances 0.000 claims description 21
- 239000004065 semiconductor Substances 0.000 claims description 18
- 238000000151 deposition Methods 0.000 claims description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims description 13
- 239000000758 substrate Substances 0.000 claims description 13
- 230000001590 oxidative effect Effects 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000005121 nitriding Methods 0.000 claims description 8
- 230000035515 penetration Effects 0.000 claims description 8
- 230000003647 oxidation Effects 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 7
- 238000004544 sputter deposition Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000012298 atmosphere Substances 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims description 2
- 238000003682 fluorination reaction Methods 0.000 claims description 2
- 229910052731 fluorine Inorganic materials 0.000 claims description 2
- 239000011737 fluorine Substances 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 175
- 238000000034 method Methods 0.000 description 10
- 239000000470 constituent Substances 0.000 description 6
- 238000005530 etching Methods 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- 125000004429 atom Chemical group 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 125000004433 nitrogen atom Chemical group N* 0.000 description 4
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 4
- PWKWDCOTNGQLID-UHFFFAOYSA-N [N].[Ar] Chemical compound [N].[Ar] PWKWDCOTNGQLID-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 239000012212 insulator Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 238000001755 magnetron sputter deposition Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- AFYPFACVUDMOHA-UHFFFAOYSA-N chlorotrifluoromethane Chemical compound FC(F)(F)Cl AFYPFACVUDMOHA-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- PXBRQCKWGAHEHS-UHFFFAOYSA-N dichlorodifluoromethane Chemical compound FC(F)(Cl)Cl PXBRQCKWGAHEHS-UHFFFAOYSA-N 0.000 description 1
- 235000019404 dichlorodifluoromethane Nutrition 0.000 description 1
- 238000001941 electron spectroscopy Methods 0.000 description 1
- 238000004334 fluoridation Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/10—Junction-based devices
- H10N60/12—Josephson-effect devices
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、トンネル型ジヨセフソン接合素子及
びその製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tunnel type Josephson junction device and a method for manufacturing the same.
（従来の技術）
ジヨセフソン接合素子で構成される論理回路や
記憶回路は半導体回路に比べ消費電力が小さく、
高速で動作するという大きな利点を有している。
回路の集積化に伴ない、こうした利点を最大限に
活用できるジヨセフソン接合素子の開発が求めら
れている。高速動作のためにジヨセフソン接合素
子に要求される主な特性として、ギヤツプ電圧が
大きいこと、接合容量が小さいこと、サブギヤツ
プリーク電流が小さいことがあげられる。これら
の特性はエネルギーギヤツプの大きな超伝導体
層、すなわち超伝導転移温度Tcの大きな超伝導
体層と誘電率の小さいトンネル障壁層を用いて、
しかも超伝導体層とトンネル障壁層との間の低
Tcまたはノーマルな性質を示す遷移領域をでき
るだけ薄くすることによつて実現される。こうし
た目的に最適なジヨセフソン接合素子として、超
伝導体層にNbN膜を用い、トンネル障壁層に金
属または半導体の酸化膜を用いたものが注目され
ている。NbN膜の場合、各種スパツタ法により
Tcの高い膜（Tc＝15K）が100℃以下の比較的低
い基板温度で得られることから、トンネル障壁層
の形成後に超伝導体層を被着する際にも、超伝導
体層とトンネル障壁層との熱反応が他の高TC超
伝導体膜に比べて進行しにくく、良好な接合特性
が期待できる。(Prior art) Logic circuits and memory circuits composed of Josephson junction elements consume less power than semiconductor circuits.
It has the great advantage of operating at high speed.
As circuits become more integrated, there is a need to develop Josephson junction devices that can take full advantage of these advantages. The main characteristics required of Josephson junction devices for high-speed operation are high gap voltage, low junction capacitance, and low sub-gap leakage current. These characteristics can be achieved by using a superconductor layer with a large energy gap, that is, a superconductor layer with a large superconducting transition temperature Tc and a tunnel barrier layer with a small dielectric constant.
Moreover, the low temperature between the superconductor layer and the tunnel barrier layer
This is achieved by making the transition region exhibiting Tc or normal properties as thin as possible. A Josephson junction device that uses an NbN film for the superconductor layer and a metal or semiconductor oxide film for the tunnel barrier layer is attracting attention as the ideal Josephson junction device for this purpose. In the case of NbN film, various sputtering methods are used to
Since a film with a high Tc (Tc = 15K) can be obtained at a relatively low substrate temperature of 100°C or less, when depositing the superconductor layer after forming the tunnel barrier layer, the superconductor layer and the tunnel barrier Thermal reaction with the layer is less likely to proceed than with other high TC superconductor films, and good bonding properties can be expected.
従来例として、上田らによつて1985年に発表さ
れた電子通信学会技術報告のCPM85−２，７〜
12ページの論文などがある。ここで提案されたジ
ヨセフソン接合素子は、第３図に示すように、基
板３１上に形成されたNbNでなる第１の超伝導
体層３２と、この第１の超伝導体層３２上に形成
されたトンネル障壁層３３と、このトンネル障壁
層３３を介して第１の超伝導体層３２と対向して
形成されたNbNでなる第２の超伝導体層３４と
で構成されている。トンネル障壁層３３はまず数
10ÅのAl膜を被着した後、その表面を酸化して
形成される。このように、第１の超伝導体層３２
上に金属層を被着した後、その表面を酸素を含む
ガス雰囲気で熱酸化やプラズマ酸化してトンネル
障壁層３３を形成する方法は、酸化膜そのものを
被着する方法に比べて基板面内での酸化膜厚の均
一性及び制御性が優れていることから一般によく
用いられる。 As a conventional example, CPM85-2,7~ of the Institute of Electronics and Communication Engineers technical report published in 1985 by Ueda et al.
It includes a 12-page paper. As shown in FIG. 3, the Josephson junction device proposed here includes a first superconductor layer 32 made of NbN formed on a substrate 31, and a superconductor layer 32 formed on this first superconductor layer 32. A second superconductor layer 34 made of NbN is formed to face the first superconductor layer 32 with the tunnel barrier layer 33 in between. The tunnel barrier layer 33 is first made of a number
It is formed by depositing a 10 Å Al film and then oxidizing its surface. In this way, the first superconductor layer 32
The method of depositing a metal layer thereon and then thermally oxidizing or plasma oxidizing its surface in an oxygen-containing gas atmosphere to form the tunnel barrier layer 33 is more effective than depositing an oxide film itself on the surface of the substrate. It is commonly used because of its excellent uniformity and controllability of the oxide film thickness.
（発明が解決しようとする問題点）
しかしながら、上記ジヨセフソン接合素子の構
造では、NbNでなる第１の超伝導体層３２とト
ンネル障壁層３３となるAl膜が直接接触してい
る。そのため窒化の生成エネルギーの小さいAl
がNbNからＮ原子を奪う反応が起こり、第１の
超伝導体層３２表面に化学量論的組成よりもＮ原
子の少ない低Tc層またはノーマス層が形成され
る。(Problems to be Solved by the Invention) However, in the structure of the Josephson junction element described above, the first superconductor layer 32 made of NbN and the Al film serving as the tunnel barrier layer 33 are in direct contact. Therefore, Al has low nitriding energy.
A reaction occurs in which NbN is deprived of N atoms, and a low Tc layer or a normal layer containing fewer N atoms than the stoichiometric composition is formed on the surface of the first superconductor layer 32.
このようにして、第１の超伝導体層３２とトン
ネル障壁層３３との間の遷移領域が広がる結果、
ジヨセフソン接合素子のギヤツプ電圧が減少する
という問題やサブギヤツプリーク電流が増加する
という問題が生じる。また、トンネル障壁層３３
と第２の超伝導体層３４との間でもNbNの被着
条件次第で前述と同様なAlの窒化反応を生じ、
接合特性を劣化させる。前述の従来例と同様な目
的でトンネル障壁層に適用される金属の多くは窒
化の生成エネルギーがNbの値よりも小さいため
にAlの場合と同じ問題を生じる。 In this way, the transition region between the first superconductor layer 32 and the tunnel barrier layer 33 widens, resulting in
Problems arise in that the gap voltage of the Josephson junction element decreases and that the sub-gear leakage current increases. In addition, the tunnel barrier layer 33
Depending on the NbN deposition conditions, the same nitriding reaction of Al as described above occurs between the NbN layer and the second superconductor layer 34.
Deteriorates bonding properties. Many of the metals applied to the tunnel barrier layer for the same purpose as the conventional example described above have a nitriding energy smaller than that of Nb, and therefore suffer from the same problem as Al.
本発明の目的は、このような従来の欠点を取り
除いたジヨセフソン接合素子及びその製造方法を
提供することにある。 SUMMARY OF THE INVENTION An object of the present invention is to provide a Josephson junction device and a method for manufacturing the same, which eliminates such conventional drawbacks.
（問題点を解決するための手段）
本発明によれば、基板上に形成されたNbNで
なる第１の超伝導体層と、この第１の超伝導体層
上に形成されたトンネル障壁層と、このトンネル
障壁層を介して前記第１の超伝導体層と対向して
形成されたNbNでなる第２の超伝導体層とを基
本構成要素とするジヨセフソン接合素子におい
て、前記第１の超伝導体層と前記トンネル障壁層
との間または前記トンネル障壁層と前記第２の超
伝導体層との間に少なくとも一方にクーパー対の
侵入深さ以下の膜厚のNbでなる補助層を介在さ
せたことを特徴とするジヨセフソン接合素子が得
られる。(Means for Solving the Problems) According to the present invention, a first superconductor layer made of NbN formed on a substrate, and a tunnel barrier layer formed on the first superconductor layer. and a second superconductor layer made of NbN formed opposite to the first superconductor layer with the tunnel barrier layer in between. An auxiliary layer made of Nb having a thickness equal to or less than the penetration depth of the Cooper pair is provided between the superconductor layer and the tunnel barrier layer or between the tunnel barrier layer and the second superconductor layer. A Josephson junction element is obtained, which is characterized in that it is interposed.
更に、本発明によれば、アルゴンと窒素との混
合ガス雰囲気中でNbターゲツトをスパツタして
基板上にNbNでなる第１の超伝導体層を被着す
る工程と、前記第１の超伝導体層表面の窒素過剰
な層を除去した後、クーパー対の侵入深さ以下の
膜厚のNbでなる補助層と金属または半導体層を
連続被着する工程と、この金属または半導体層を
酸化、窒化またはフツ化してトンネル障壁層を形
成する工程と、このトンネル障壁層上に前記第１
の超伝導体層と同様な方法でNbNでなる第２の
超伝導体層を形成する工程とを含むことを特徴と
するジヨセフソン接合素子の製造方法が得られ
る。 Further, according to the present invention, the step of depositing a first superconductor layer made of NbN on the substrate by sputtering a Nb target in a mixed gas atmosphere of argon and nitrogen; After removing the nitrogen-excessive layer on the surface of the body layer, a step of successively depositing an auxiliary layer made of Nb and a metal or semiconductor layer with a thickness less than the penetration depth of the Cooper pair, and oxidizing this metal or semiconductor layer. a step of forming a tunnel barrier layer by nitriding or fluoridating;
forming a second superconductor layer made of NbN in the same manner as the superconductor layer of .
（作用）
本発明による構造では、NbNでなる第１の超
伝導体層とトンネル障壁層との間、またはトンネ
ル障壁層とNbNでなる第２の超伝導体層との間
の少なくとも一方にクーパー対の侵入深さ以下の
膜厚をもつNbでなる補助層が設けられている。
そのため、トンネル障壁層の構成原子である金属
または半導体の方がNbより窒素一原子当りの窒
化の生成エネルギーが小さい場合でも、上記金属
または半導体が第１、第２の超伝導体層からＮ原
子を奪う反応は補助層によつて防止される。ま
た、補助層には第１、第２の超伝導体層の構成原
子であるNbを用いているため両者間の反応は進
行しにくい。さらに、補助層がクーパー対の侵入
深さ以下の膜厚の超伝導体層であることから、プ
ロキシミテイ効果により第１、第２の超伝導体層
材料でありNbNの超伝導特性が保持され、しか
もサブギヤツプリーク電流の小さいジヨセフソン
接合素子が形成できる。(Function) In the structure according to the present invention, there is a cooper between at least one of the first superconductor layer made of NbN and the tunnel barrier layer, or between the tunnel barrier layer and the second superconductor layer made of NbN. An auxiliary layer of Nb having a thickness less than the penetration depth of the pair is provided.
Therefore, even if the metal or semiconductor that is the constituent atom of the tunnel barrier layer has a lower nitridation energy per nitrogen atom than Nb, the metal or semiconductor will be able to absorb the N atoms from the first and second superconductor layers. Reactions that take away are prevented by the auxiliary layer. Furthermore, since Nb, which is a constituent atom of the first and second superconductor layers, is used in the auxiliary layer, the reaction between them is difficult to proceed. Furthermore, since the auxiliary layer is a superconductor layer with a thickness less than the penetration depth of Cooper pairs, the superconducting properties of NbN, which is the material of the first and second superconductor layers, are maintained due to the proximity effect. Moreover, a Josephson junction element with small sub-gear leakage current can be formed.
第１の超伝導体層上に金属または半導体を被着
した後、その酸化、窒化、フツ化のいずれかの化
学反応によつて形成されたトンネル障壁層は基板
面内での膜厚の均一性及び制御性が優れている。
また、上記化学反応における酸素、窒素、フツ素
一原子当りの生成エネルギーがNbに対する同一
反応の値よりも小さい値をもつ金属や半導体の化
合物を用いることによつて補助層とトンネル障壁
層との反応を大幅に軽減することができる。 After depositing a metal or semiconductor on the first superconductor layer, the tunnel barrier layer is formed by a chemical reaction of oxidation, nitridation, or fluorination, and has a uniform thickness within the substrate surface. Excellent performance and controllability.
In addition, by using a metal or semiconductor compound whose production energy per atom of oxygen, nitrogen, or fluorine in the above chemical reaction is smaller than that of the same reaction with Nb, the auxiliary layer and the tunnel barrier layer can be combined. Reactions can be significantly reduced.
更に本発明による製造方法では、第１の超伝導
体層はアルゴン一窒素雰囲気中でNbターゲツト
をスパツタしてNbN膜を被着した後、窒素過剰
な表面層を除去して形成される。スパツタ法は高
TcのNbN膜の作成には優れているが、スパツタ
終了直後NbN膜表面に窒素が吸着して窒素過剰
な低Tc層が形成され易い。従つて、この層を除
去することにより、第１の超伝導体層と補助層と
の間の遷移領域を薄くすることができる。その結
果、NbN本来のギヤツプ電圧をもち、サブギヤ
ツプリーク電流の小さいジヨセフソン接合素子が
得られる。 Furthermore, in the manufacturing method according to the present invention, the first superconductor layer is formed by depositing a NbN film by sputtering an Nb target in an argon-nitrogen atmosphere, and then removing the nitrogen-rich surface layer. Spatsuta method is high
Although it is excellent for creating a Tc NbN film, nitrogen is adsorbed on the NbN film surface immediately after sputtering, and a low Tc layer with excessive nitrogen is likely to be formed. By removing this layer, the transition region between the first superconductor layer and the auxiliary layer can therefore be thinned. As a result, a Josephson junction element with a gap voltage inherent to NbN and a small sub-gear leakage current can be obtained.
（実施例）
本発明のジヨセフソン接合素子の実施例を図面
を参照して詳細に説明する。(Example) Examples of the Josephson junction device of the present invention will be described in detail with reference to the drawings.
このジヨセフソン接合素子は第１図に示すよう
に、絶縁体基板あるいは表面に絶縁体を有する基
板１１上に形成されたNbNでなる第１の超伝導
体層１２と、この第１の超伝導体層１２上に形成
されたNbでなる第１の補助層１３と、この第１
の補助層１３上に形成されたトンネル障壁層１４
と、このトンネル障壁層１４を介して第１の補助
層１３と対向して形成されたNbでなる第２の補
助層１５と、この第２の補助層１５上に形成され
たNbNでなる第２の超伝導体層１６とで構成さ
れている。第１、第２の超伝導体層１２，１６は
アルゴン一窒素雰囲気中でNbターゲツトをスパ
ツタして得られた膜厚2000ÅのNbN膜である。
この膜のTcは15〜16Kである。第１、第２の補
助層１３，１５は膜厚約50Åのスパツタ膜であ
る。トンネル障壁層１４には、まず厚さ数10Åの
Al膜をスパツタした後、その表面を純酸素雰囲
気中で熱酸化して形成されたAl2O3膜が用いられ
る。 As shown in FIG. 1, this Josephson junction element includes a first superconductor layer 12 made of NbN formed on an insulating substrate or a substrate 11 having an insulator on the surface, and a first superconductor layer 12 made of NbN. A first auxiliary layer 13 made of Nb formed on the layer 12;
A tunnel barrier layer 14 formed on the auxiliary layer 13 of
A second auxiliary layer 15 made of Nb is formed opposite to the first auxiliary layer 13 with this tunnel barrier layer 14 in between, and a second auxiliary layer 15 made of NbN is formed on this second auxiliary layer 15. It is composed of two superconductor layers 16. The first and second superconductor layers 12 and 16 are NbN films with a thickness of 2000 Å obtained by sputtering a Nb target in an argon-nitrogen atmosphere.
The Tc of this film is 15-16K. The first and second auxiliary layers 13 and 15 are sputtered films with a thickness of about 50 Å. The tunnel barrier layer 14 is first formed with a thickness of several tens of Å.
An Al 2 O 3 film is used, which is formed by sputtering an Al film and then thermally oxidizing its surface in a pure oxygen atmosphere.
本実施例によれば、第１、第２の超伝導体層１
２，１６とトンネル障壁層１４との間にそれぞれ
第１、第２の補助層１３，１５が設けてあるた
め、第１、第２の超伝導体層１２，１６とトンネ
ル障壁層１４との反応は第１、第２の補助層１
３，１５によつて防止される。また、第１、第２
の補助層１３，１５には第１、第２の超伝導体層
の構成原子であるNbを用いているため両者間の
反応は進行しにくい。さらに、第１、第２の補助
層がクーパー対の侵入深さ以下（約50Å）の超伝
導体であることから、NbN本来のギヤツプ電圧
をもちサブギヤツプリーク電流の小さいジヨセフ
ソン接合素子が得られる。 According to this embodiment, the first and second superconductor layers 1
Since the first and second auxiliary layers 13 and 15 are provided between the first and second superconductor layers 12 and 16 and the tunnel barrier layer 14, respectively, the relationship between the first and second superconductor layers 12 and 16 and the tunnel barrier layer 14 is The reaction occurs in the first and second auxiliary layers 1
3,15. Also, the first and second
Since Nb, which is a constituent atom of the first and second superconductor layers, is used in the auxiliary layers 13 and 15, the reaction between them is difficult to proceed. Furthermore, since the first and second auxiliary layers are superconductors with a depth below the Cooper pair penetration depth (approximately 50 Å), a Josephson junction element with a gap voltage inherent to NbN and a small sub-gear leakage current is possible. can get.
本実施例でトンネル障壁層１４を形成するため
に用いたAlは、酸化の生成エネルギーがNbより
も小さく、酸化膜形成後も第１、第２超伝導体層
１２，１６とトンネル障壁層１４との反応を生じ
ない。また、AlはNbへのぬれ性が良好で、熱酸
化によつて均質な酸化膜が制御性良く形成され
る。 Al, which was used to form the tunnel barrier layer 14 in this example, has a lower oxidation energy than Nb, and even after the oxide film is formed, the first and second superconductor layers 12, 16 and the tunnel barrier layer 14 No reaction occurs. Furthermore, Al has good wettability to Nb, and a homogeneous oxide film can be formed with good controllability through thermal oxidation.
本実施例では、補助層を第１の超伝導体層１２
とトンネル障壁層１４との間、トンネル障壁層１
４と第２の超伝導体層１６との間の双方に設けた
が、成膜条件に応じてどちらか一方でもその効果
は大きい。特に、トンネル障壁層１４を金属また
は半導体の被着後の酸化、窒化またはフツ化によ
つて形成する場合には、第１の超伝導体層１２と
トンネル障壁層１４との間に補助層を設けること
は両者間の反応を防ぐのに非常に有効である。さ
らに、本実施例では、トンネル障壁層１４にAl
の被着後酸化して形成したAl酸化膜を用いたが、
他の金属や半導体を酸化、窒化またはフツ化の各
反応により形成した絶縁膜、被着した絶縁膜や半
導体膜でも同様な効果が得られる。ただし、トン
ネル障壁層１４の構成原子である金属または半導
体の方がNbよりも上記各反応に対する生成エネ
ルギーが小さい場合にはトンネル障壁層１４はよ
り安定である。 In this example, the auxiliary layer is the first superconductor layer 12.
and tunnel barrier layer 14, tunnel barrier layer 1
4 and the second superconductor layer 16, but depending on the film-forming conditions, the effect is great even with either one. In particular, when the tunnel barrier layer 14 is formed by oxidation, nitridation or fluoridation after deposition of a metal or semiconductor, an auxiliary layer is provided between the first superconductor layer 12 and the tunnel barrier layer 14. This is very effective in preventing reactions between the two. Furthermore, in this embodiment, the tunnel barrier layer 14 is made of aluminum.
We used an Al oxide film formed by oxidation after deposition.
Similar effects can be obtained with insulating films formed by oxidizing, nitriding, or fluoriding reactions of other metals or semiconductors, or with deposited insulating films or semiconductor films. However, if the constituent atoms of the tunnel barrier layer 14, such as metal or semiconductor, have a smaller production energy for each of the reactions described above than Nb, the tunnel barrier layer 14 will be more stable.
次に本発明のジヨセフソン接合素子の製造方法
の実施例を図面を用いて詳細に説明する。 Next, an embodiment of the method for manufacturing a Josephson junction element of the present invention will be described in detail with reference to the drawings.
まず、第２図ａに示すように、絶縁基板あるい
は表面に絶縁体を有する基板２１上に、高周波マ
グネトロンスパツタ法によりアルゴン一窒素雰囲
気中でNbターゲツトをスパツタして膜厚2000Å
のNbNでなる第１の超伝導体層２２を形成する。
この際、第１の超伝導体層２２表面に多量の窒素
が吸着して窒素過剰な低Tc層２３が形成される。
オージエ電子分光分析による第１の超伝導体層２
２の組成の深さ分析によれば、窒素過剰な低Tc
層２３の組成は化学量論量的値よりも窒素が約50
％過剰で、この層の厚さは10Å程度である。その
ため、窒素過剰な層２３をアルゴンを用いたスパ
ツタクリーニングにより除去し、その後高周波マ
グネトロンスパツタ法により厚さ約50ÅのNbで
なる補助層２４と約100ÅのAlでなる金属層２５
を連続被着すると第２図ｂのような構造が得られ
る。 First, as shown in FIG. 2a, an Nb target is sputtered to a thickness of 2000 Å on an insulating substrate or a substrate 21 having an insulator on its surface in an argon-nitrogen atmosphere by high-frequency magnetron sputtering.
A first superconductor layer 22 made of NbN is formed.
At this time, a large amount of nitrogen is adsorbed on the surface of the first superconductor layer 22, forming a nitrogen-excess low Tc layer 23.
First superconductor layer 2 by Augier electron spectroscopy
According to the depth analysis of the composition of 2, low Tc with excess nitrogen
The composition of layer 23 is approximately 50% nitrogen below the stoichiometric value.
% excess, the thickness of this layer is on the order of 10 Å. Therefore, the nitrogen-excessive layer 23 is removed by sputter cleaning using argon, and then the auxiliary layer 24 made of Nb with a thickness of about 50 Å and the metal layer 25 made of Al with a thickness of about 100 Å are removed by high-frequency magnetron sputtering.
When continuously deposited, a structure as shown in FIG. 2b is obtained.
次に、第２図ｃに示すように、Al層２５の表
面を純酸素雰囲気中で熱酸化してトンネル障壁層
２６を形成する。第２図ｄに示すように、第１の
超伝導体層２２の場合と同様な方法で膜厚2000Å
のNbNでなる第２の超伝導体層２７を被着して
接合構成層の形成を完了する。本ジヨセフソン接
合素子の製造方法の特徴は上述の接合構成層の形
成方法にあるが、実際の素子を実現するためには
一例として以下に述べるよなプロセスを追加しな
ければならない。まず、フロン12（CCl2F2）やフ
ロン13（CF4）をエツチングガスとする反応性ス
パツタエツチング法で第２図ｄに示すような接合
構成層をパターニングして下部配線を形成した
後、第２図ｅに示すように第２の超伝導体層２７
上の接合部となる場所にエツチングマスク２８を
形成し、CCl2F2やCF4による反応性エツチング法
により第２の超伝導体層２７をパターニングして
接合部を規定する。次に、第２図ｆに示すように
エツチングマスク２８を残したまま一酸化珪素
（SiO）などでなる絶縁体層２９を蒸着する。エ
ツチングマスク２８をリフトオフして第２図ｇに
示すような構造を得た後、第２の超伝導体層２７
表面をスパツタクリーニングし、第２図ｈに示す
ように第２の超伝導体層２７と同様な方法で第３
の超伝導体層３０を被着、パターニングし上部配
線を形成する。 Next, as shown in FIG. 2c, the surface of the Al layer 25 is thermally oxidized in a pure oxygen atmosphere to form a tunnel barrier layer 26. As shown in FIG. 2d, a film thickness of 200 Å was obtained using the same method as in the case of the first superconductor layer 22.
A second superconductor layer 27 of NbN is deposited to complete the formation of the bonding layers. The feature of the method for manufacturing the Josephson junction element is the method of forming the junction constituent layers described above, but in order to realize an actual element, it is necessary to add the following process as an example. First, the bonding constituent layer is patterned as shown in Figure 2d using a reactive sputter etching method using fluorocarbon 12 (CCl 2 F 2 ) or fluorocarbon 13 (CF 4 ) as an etching gas to form the lower wiring. , the second superconductor layer 27 as shown in FIG.
An etching mask 28 is formed at the location where the upper junction will be formed, and the second superconductor layer 27 is patterned by reactive etching using CCl 2 F 2 or CF 4 to define the junction. Next, as shown in FIG. 2f, an insulating layer 29 made of silicon monoxide (SiO) or the like is deposited with the etching mask 28 left in place. After lifting off the etching mask 28 to obtain the structure shown in FIG.
The surface is spatter cleaned, and a third superconductor layer 27 is formed in the same manner as the second superconductor layer 27, as shown in FIG. 2h.
A superconductor layer 30 is deposited and patterned to form upper wiring.
本実施例では第２図ａの工程で生じた第１の超
伝導体層２２表面の窒素過剰な層２３を除去した
後、補助層２４を被着する。そのため、第１の超
伝導体層２２と補助層２４との間に存在する低
Tcまたはノーマルな性質を示す遷移領域を薄く
することができる。また、第２図ｂに示すよう
に、Alでなる金属層２５は第１の超伝導体層２
２上にNbでなる補助層２４を介して形成される。
そのため、第１の超伝導体層２２と金属または半
導体層２５との反応は補助層２４によつて防止さ
れる。トンネル障壁層２６を形成するAl酸化物
は前述したようにNb酸化物より安定であるため、
補助層２４とトンネル障壁層２６との化学反応は
生じない。さらに、AlはNb膜へのぬれ性が良好
で、熱酸化によつて均質な酸化膜が制御性良く形
成される。以上のことから、NbN本来のギヤツ
プ電圧をもちサブギヤツプリーク電流の小さいジ
ヨセフソン接合素子が得られる。本実施例では、
トンネル障壁層１４にAlの被着後、酸化して形
成したAl酸化膜を用いたが、他の金属や半導体
を酸化、窒化またはフツ化の各反応により形成し
た絶縁膜でも、上記金属や半導体の各反応に対す
る生成エネルギーの絶対値がNbの同様な反応に
対する値よりも大きい場合には本実施例と同様な
結果が得られる。 In this embodiment, the auxiliary layer 24 is deposited after removing the nitrogen-rich layer 23 on the surface of the first superconductor layer 22 produced in the step shown in FIG. 2a. Therefore, the low temperature existing between the first superconductor layer 22 and the auxiliary layer 24
The transition region exhibiting Tc or normal properties can be made thinner. Further, as shown in FIG. 2b, the metal layer 25 made of Al is the first superconductor layer 2.
2 with an auxiliary layer 24 made of Nb interposed therebetween.
Therefore, reaction between the first superconductor layer 22 and the metal or semiconductor layer 25 is prevented by the auxiliary layer 24. As mentioned above, the Al oxide forming the tunnel barrier layer 26 is more stable than the Nb oxide.
No chemical reaction occurs between the auxiliary layer 24 and the tunnel barrier layer 26. Furthermore, Al has good wettability to the Nb film, and a homogeneous oxide film can be formed with good controllability through thermal oxidation. From the above, a Josephson junction element with a gap voltage inherent to NbN and a small sub-gear leakage current can be obtained. In this example,
Although an Al oxide film formed by depositing Al and oxidizing it was used for the tunnel barrier layer 14, an insulating film formed by oxidizing, nitriding, or fluoriding other metals or semiconductors may also be used. If the absolute value of the energy of formation for each reaction is larger than the value for a similar reaction of Nb, results similar to those of this example can be obtained.
（発明の効果）
以上説明したように本発明によれば、NbNで
なる超伝導体層とトンネル障壁層との間にクーパ
ー対の侵入深さ以下の膜厚を有するNbでなる補
助層が設けられているため、超伝導体層とトンネ
ル障壁層との反応で生じる低Tc層やノーマル層
を介在することなく、NbN本来のギヤツプ電圧
をもち、サブギヤツプリーク電流の小さいジヨセ
フソン接合素子が得られる。また、Nbと比較し
て、反応の生成エネルギーが小さな金属または半
導体を酸化、窒化またはフツ化して形成した化合
物をトンネル障壁層に用いることにより、その化
学的な安定性、膜厚の均一性及び制御性がさらに
改善されたジヨセフソン接合素子が得られる。(Effects of the Invention) As explained above, according to the present invention, an auxiliary layer made of Nb having a film thickness equal to or less than the penetration depth of Cooper pairs is provided between the superconductor layer made of NbN and the tunnel barrier layer. As a result, Josephson junction elements with the inherent gap voltage of NbN and small sub-gap leakage current can be created without the intervening low Tc layer or normal layer generated by the reaction between the superconductor layer and the tunnel barrier layer. can get. In addition, by using a compound formed by oxidizing, nitriding, or fluoridating a metal or semiconductor whose reaction energy is lower than that of Nb for the tunnel barrier layer, we can improve its chemical stability, uniformity of film thickness, and A Josephson junction element with further improved controllability is obtained.
さらに、本発明によれば、第１の超伝導体層表
面の窒素過剰な低Tc層を除去した後、補助層が
形成されるため、第１の超伝導体層と補助層との
間の超伝導特性の悪い遷移領域のない特性の優れ
たジヨセフソン接合素子が製造できる。 Furthermore, according to the present invention, since the auxiliary layer is formed after removing the nitrogen-excess low Tc layer on the surface of the first superconductor layer, the auxiliary layer is formed between the first superconductor layer and the auxiliary layer. A Josephson junction device with excellent characteristics without a transition region with poor superconducting characteristics can be manufactured.
第１図は本発明のジヨセフソン接合素子を示す
断面図、第２図ａ〜ｈは本発明のジヨセフソン接
合素子の製造方法を工程順に示す断面図、第３図
は従来のジヨセフソン接合素子を示す断面図であ
る。
図において、１１，２１，３１は基板、１２，
２２，３２はNbNでなる第１の超伝導体層、１
３，２４はNbでなる第１の補助層またはNbでな
る補助層、１４，２６，３３はトンネル障壁層、
１５はNbでなる第２の補助層、１６，２７，３
４はNbNでなる第２の超伝導体層、２３は窒素
過剰な低Tc層、２５は金属層、２８はエツチン
グマスク、２９は絶縁体層、３０は第３の超伝導
体層である。
FIG. 1 is a cross-sectional view showing a di-Josefson junction device of the present invention, FIGS. 2 a to h are cross-sectional views showing the manufacturing method of the di-Josefson junction device of the present invention in the order of steps, and FIG. 3 is a cross-sectional view showing a conventional di-Josefson junction device. It is a diagram. In the figure, 11, 21, 31 are substrates, 12,
22, 32 are the first superconductor layers made of NbN, 1
3 and 24 are first auxiliary layers made of Nb or auxiliary layers made of Nb; 14, 26, and 33 are tunnel barrier layers;
15 is the second auxiliary layer made of Nb, 16, 27, 3
4 is a second superconductor layer made of NbN, 23 is a nitrogen-excess low Tc layer, 25 is a metal layer, 28 is an etching mask, 29 is an insulator layer, and 30 is a third superconductor layer.
Claims (1)
導体層と、この第１の超伝導体層上に形成された
トンネル障壁層と、このトンネル障壁層を介して
前記第１の超伝導体層と対向して形成された
NbNでなる第２の超伝導体層とを基本構成要素
とするジヨセフソン接合素子において、前記第１
の超伝導体層と前記トンネル障壁層との間または
前記トンネル障壁層と前記第２の超伝導体層との
間の少なくとも一方にクーパー対の侵入深さ以下
の膜厚のNbでなる補助層を介在させたことを特
徴とするジヨセフソン接合素子。 ２ 前記トンネル障壁層が金属または半導体の酸
化、窒化、フツ化のいずれかの化学反応により形
成された化合物で、前記化学反応における酸素、
窒素、フツ素一原子当りの生成エネルギーの値が
Nbに対する同一反応の値よりも小さいことを特
徴とする特許請求の範囲第１項記載のジヨセフソ
ン接合素子。 ３ アルゴンと窒素との混合ガス雰囲気中でNb
ターゲツトをスパツタして基板上にNbNでなる
第１の超伝導体層を被着する工程と、前記第１の
超伝導体層表面の窒素過剰な層を除去した後、ク
ーパー対の侵入深さ以下の膜厚のNbでなる補助
層と金属または半導体層を連続被着する工程と、
この金属または半導体層を酸化、窒化またはフツ
化してトンネル障壁層を形成する工程と、このト
ンネル障壁層上に前記第１の超伝導体層と同様な
方法でNbNでなる第２の超伝導体層を形成する
工程とを含むことを特徴とするジヨセフソン接合
素子の製造方法。[Claims] 1. A first superconductor layer made of NbN formed on a substrate, a tunnel barrier layer formed on this first superconductor layer, and a formed opposite to the first superconductor layer.
In the Josephson junction device having a second superconductor layer made of NbN as a basic component, the first
an auxiliary layer made of Nb with a film thickness equal to or less than the penetration depth of the Cooper pair between the superconductor layer and the tunnel barrier layer or between the tunnel barrier layer and the second superconductor layer; A Josephson junction element characterized by interposing. 2. The tunnel barrier layer is a compound formed by a chemical reaction such as oxidation, nitridation, or fluorination of a metal or semiconductor, and oxygen in the chemical reaction,
The value of formation energy per atom of nitrogen and fluorine is
The Josephson junction device according to claim 1, characterized in that the value is smaller than that of the same response to Nb. 3 Nb in a mixed gas atmosphere of argon and nitrogen
After depositing a first superconductor layer made of NbN on the substrate by sputtering a target and removing the nitrogen-rich layer on the surface of the first superconductor layer, the depth of penetration of the Cooper pair is determined. A step of continuously depositing an auxiliary layer made of Nb and a metal or semiconductor layer with a thickness of:
A step of forming a tunnel barrier layer by oxidizing, nitriding or fluoridating this metal or semiconductor layer, and forming a second superconductor made of NbN on this tunnel barrier layer in the same manner as the first superconductor layer. A method of manufacturing a Josephson junction element, comprising the step of forming a layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61229536A JPS6386486A (en) | 1986-09-30 | 1986-09-30 | Josephson junction device and manufacture thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61229536A JPS6386486A (en) | 1986-09-30 | 1986-09-30 | Josephson junction device and manufacture thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6386486A JPS6386486A (en) | 1988-04-16 |
| JPH0517714B2 true JPH0517714B2 (en) | 1993-03-09 |
Family
ID=16893707
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61229536A Granted JPS6386486A (en) | 1986-09-30 | 1986-09-30 | Josephson junction device and manufacture thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6386486A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11495724B2 (en) * | 2020-07-21 | 2022-11-08 | International Business Machines Corporation | Superconducting structure and device surface termination with alloy |
-
1986
- 1986-09-30 JP JP61229536A patent/JPS6386486A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6386486A (en) | 1988-04-16 |
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