JPH05211356A - Manufacture of planar type oxide superconducting thin film josephson element - Google Patents
Manufacture of planar type oxide superconducting thin film josephson elementInfo
- Publication number
- JPH05211356A JPH05211356A JP4267338A JP26733892A JPH05211356A JP H05211356 A JPH05211356 A JP H05211356A JP 4267338 A JP4267338 A JP 4267338A JP 26733892 A JP26733892 A JP 26733892A JP H05211356 A JPH05211356 A JP H05211356A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- oxide superconducting
- superconducting thin
- film
- insulator
- 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
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、平面型の酸化物超電導
薄膜ジョセフソン素子の作製方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a flat oxide superconducting thin film Josephson device.
【０００２】[0002]
【従来の技術】酸化物超電導薄膜を用いたジョセフソン
素子には積層型と平面型とがあり、平面型ジョセフソン
素子としてブリッジ型が知られている。特に、平面型ジ
ョセフソン素子において、良好な特性を持たせるために
は、ブリッジ部の対向幅をできるだけ小さく形成するこ
とが望ましく、それには１０ｎｍ程度の微細加工技術が
要求される。しかし、ブリッジ部の形成に従来より用い
られている電子線露光法，Ｘ線露光法もしくは収束イオ
ンビーム法などでは、１００ｎｍが限界とされており、
現状では良好な特性を持つ平面型ジョセフソン素子を作
製するのは困難である。2. Description of the Related Art Josephson elements using an oxide superconducting thin film are classified into a laminated type and a planar type, and a bridge type is known as a planar type Josephson element. In particular, in the planar Josephson element, in order to have good characteristics, it is desirable that the opposing width of the bridge portion is formed as small as possible, which requires a fine processing technology of about 10 nm. However, the electron beam exposure method, the X-ray exposure method, or the focused ion beam method that has been conventionally used for forming the bridge portion has a limit of 100 nm,
At present, it is difficult to fabricate a planar Josephson device having good characteristics.
【０００３】これに対して、基板上に酸化物超電導薄膜
を所定の成膜条件の下に成膜することにより、薄膜形成
温度から室温への冷却過程において、酸化物超電導薄膜
に幅が１０ｎｍ程度の亀裂を発生させる微細加工技術を
特願平３−１１４０２９号により同一出願人から出願中
である。ここには、結晶の面方向（１１０）のＳｒＴｉ
Ｏ3 基板上にマグネトロンスパッタ法により成膜したＹ
Ｂａ2 Ｃｕ3 Ｏy （ｙは超電導体に含まれる酸素量）表
面に生じた亀裂を走査型電子顕微鏡で観察した結果を開
示しており、基板と酸化物超電導薄膜との熱膨張係数の
差に起因して生ずる内部応力の亀裂発生機構への影響が
検討されている。On the other hand, by forming an oxide superconducting thin film on a substrate under predetermined film forming conditions, the width of the oxide superconducting thin film is about 10 nm in the cooling process from the thin film forming temperature to room temperature. The same applicant is applying for a microfabrication technique for generating cracks in Japanese Patent Application No. 3-114029. Here, SrTi in the crystal plane direction (110) is used.
Y formed by magnetron sputtering on O 3 substrate
It discloses the results of observing cracks formed on the surface of Ba 2 Cu 3 O y (y is the amount of oxygen contained in the superconductor) with a scanning electron microscope, and shows the difference in the thermal expansion coefficient between the substrate and the oxide superconducting thin film. The effect of internal stress caused by the crack on the crack initiation mechanism has been investigated.
【０００４】[0004]
【発明が解決しようとする課題】平面型ジョセフソン素
子は、ブリッジ部となる酸化物超電導薄膜の微細加工領
域に、障壁層が堆積された素子構造を有するため、その
作製方法としては、成膜室（チャンバー）中で基板上に
酸化物超電導薄膜を形成し、これを一旦成膜室から取り
出して微細加工を施した後に、再度成膜室に戻して障壁
層の堆積を行なっている。このため、成膜室から取り出
されている間、酸化物超電導薄膜は大気に曝されること
となり、大気中の水分や炭酸ガスにより劣化する。雰囲
気による影響は、上述した成膜後の冷却過程で酸化物超
電導薄膜に亀裂を発生させる微細加工技術を適用した平
面型ジョセフソン素子についても十分に留意する必要が
あり、素子を作製した後ある時間放置しておくと、期待
される特性が得られなくなるとか、素子の作製過程で老
化が進行し、素子作製直後でも特性が低下していること
があるということは、素子の再現性という点で問題であ
る。これらのことは、亀裂を形成した部分から酸化物超
電導薄膜の内部に向かって劣化が徐々に進むことに起因
すると考えられるので、この平面型ジョセフソン素子の
特性とその再現性を向上させるためには、亀裂部に障壁
層となる物質を挿入する過程で、大気による劣化を防止
しなければならない。Since the planar Josephson device has a device structure in which a barrier layer is deposited in the finely processed region of the oxide superconducting thin film which becomes the bridge portion, the method for producing the device is to form a film. An oxide superconducting thin film is formed on a substrate in a chamber, is taken out from the film forming chamber, is subjected to microfabrication, and is then returned to the film forming chamber to deposit a barrier layer. Therefore, the oxide superconducting thin film is exposed to the atmosphere while being taken out from the film forming chamber, and is deteriorated by moisture and carbon dioxide in the atmosphere. The influence of the atmosphere must be sufficiently taken into account for the planar Josephson device to which the microfabrication technology that causes cracks in the oxide superconducting thin film is applied during the cooling process after the film formation described above, and is after the device is manufactured. If left undisturbed for a while, the expected characteristics may not be obtained, or aging may progress during the device manufacturing process, and the properties may deteriorate immediately after device manufacturing. Is a problem. These are considered to be due to the gradual deterioration from the cracked part toward the inside of the oxide superconducting thin film, so in order to improve the characteristics of this planar Josephson element and its reproducibility. In the process of inserting a substance that will form a barrier layer into the crack, it must prevent deterioration due to the atmosphere.
【０００５】そこで、本発明においては、以上の問題点
に鑑みて、作製過程およびその後に、大気中の水分など
により劣化することなく、良好な特性と優れた再現性を
有する平面型酸化物超電導薄膜ジョセフソン素子の作製
方法を提供することを目的としている。In view of the above-mentioned problems, therefore, in the present invention, the planar oxide superconducting material having good characteristics and excellent reproducibility without deterioration due to moisture in the atmosphere during and after the manufacturing process. It is an object to provide a method for manufacturing a thin film Josephson device.
【０００６】[0006]
【課題を解決するための手段】上記課題を解決するため
に、本発明に係る平面型酸化物超電導薄膜ジョセフソン
素子においては、基板上に形成される酸化物超電導薄膜
の成膜条件を設定することにより、その成膜後の冷却過
程で酸化物超電導薄膜に微細な亀裂を発生させることが
可能であるので、同一成膜室内で連続的に、障壁層を形
成することができる。すなわち、本発明に係る平面型酸
化物超電導薄膜ジョセフソン素子の作製方法は、酸化物
超電導薄膜をその成膜後の冷却過程で亀裂が発生する成
膜温度と膜厚とを設定して形成する成膜工程と、その後
の薄膜形成温度から室温まで酸素雰囲気中で冷却する冷
却工程と、この冷却工程の後に、成膜室を再び真空状態
にして酸化物超電導薄膜表面に障壁層となる物質を堆積
させる障壁層形成工程とを有することを特徴としてい
る。In order to solve the above problems, in the planar oxide superconducting thin film Josephson element according to the present invention, the film forming conditions of the oxide superconducting thin film formed on the substrate are set. As a result, fine cracks can be generated in the oxide superconducting thin film during the cooling process after the film formation, so that the barrier layer can be continuously formed in the same film formation chamber. That is, in the method for manufacturing the planar oxide superconducting thin film Josephson element according to the present invention, the oxide superconducting thin film is formed by setting the film forming temperature and the film thickness at which cracks occur in the cooling process after the film forming. After the film formation step and the subsequent cooling step of cooling from the thin film formation temperature to room temperature in an oxygen atmosphere, after this cooling step, the film formation chamber is evacuated again to remove a substance to be a barrier layer on the surface of the oxide superconducting thin film. And a barrier layer forming step of depositing.
【０００７】この平面型酸化物超電導薄膜ジョセフソン
素子において、障壁層となる物質に絶縁体を用いること
が好ましく、さらに、結晶質絶縁体としては、ＭｇＯ，
ＺｒＯ2 ，ＳｒＴｉＯ3 ，ＢａＦ2 ，ＣａＦ2 ，ＮｄＧ
ａＯ3 ，ＹＡｌＯ3 ，ＬａＡｌＯ3 ，ＬａＧａＯ3 およ
びＬａＳｒＧａＯ4 からなる群より選ばれた１種の絶縁
体であることが好ましい。また、非晶質絶縁体として
は、ＬｎＢａ2 Ｃｕ3 Ｏy （ＬｎはＬａ，Ｓｍ，Ｅｕ，
Ｇｄ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，ＹｂおよびＬｕからな
る群より選ばれた１種の元素、ｙは超電導体に含まれる
酸素量）、もしくは、ＭｇＯ，ＺｒＯ2 ，ＳｒＴｉ
Ｏ3 ，ＢａＦ2 ，ＣａＦ2 ，ＮｄＧａＯ3 ，ＹＡｌ
Ｏ3 ，ＬａＡｌＯ3 ，ＬａＧａＯ3 およびＬａＳｒＧａ
Ｏ4 からなる群より選ばれた１種の絶縁体であることが
好ましい。そして、障壁層となる物質に金属を用いても
よく、その金属としては、Ａｕ，ＡｇおよびＰｔからな
る群より選ばれた１種の金属であることが好ましい。In this planar oxide superconducting thin film Josephson element, it is preferable to use an insulator as the material for the barrier layer. Further, as the crystalline insulator, MgO,
ZrO 2 , SrTiO 3 , BaF 2 , CaF 2 , NdG
It is preferably one kind of insulator selected from the group consisting of aO 3 , YAlO 3 , LaAlO 3 , LaGaO 3 and LaSrGaO 4 . Further, as an amorphous insulator, LnBa 2 Cu 3 O y (Ln is La, Sm, Eu,
One element selected from the group consisting of Gd, Dy, Ho, Er, Tm, Yb and Lu, y is the amount of oxygen contained in the superconductor), or MgO, ZrO 2 , SrTi
O 3 , BaF 2 , CaF 2 , NdGaO 3 , YAl
O 3 , LaAlO 3 , LaGaO 3 and LaSrGa
It is preferably one kind of insulator selected from the group consisting of O 4 . Then, a metal may be used for the material forming the barrier layer, and the metal is preferably one kind of metal selected from the group consisting of Au, Ag and Pt.
【０００８】[0008]
【作用】斯かる手段を講じた本発明に係る平面型酸化物
超電導薄膜ジョセフソン素子の作製方法は、基板上に形
成される酸化物超電導薄膜が、薄膜形成温度から室温へ
の冷却過程で亀裂が発生する成膜温度と膜厚とを設定さ
れて形成されるため、成膜室から取り出すことなく、酸
化物超電導薄膜に微細加工を施すことが可能である。従
って、本発明によれば、酸化物超電導薄膜の形成後に、
障壁層物質を堆積させるためにこれを一旦成膜室から取
り出して、別の装置で微細加工を行なう必要がなくな
り、同一成膜室内で連続的な加工が可能であるから、素
子作製過程を通して常に大気と遮断された状態を保って
おり、酸化物超電導薄膜が直接大気に接触する機会を与
えない。それ故、得られた素子は大気中の水分や炭酸ガ
スにより劣化することなく、特性の安定性が高められ
る。このような同一成膜室内での連続加工は、酸化物超
電導薄膜の物性が常電導から超電導へ変わる相転移、す
なわち、酸化物超電導薄膜の結晶構造が正方晶から斜方
晶へ変化することに起因しており、相転移時における内
部応力が亀裂を発生可能な成膜条件に設定して酸化物超
電導薄膜を形成することにより始めて成し得るものであ
る。According to the method for producing the planar oxide superconducting thin film Josephson element according to the present invention, which takes such means, the oxide superconducting thin film formed on the substrate is cracked during the cooling process from the thin film forming temperature to room temperature. Since the film is formed by setting the film formation temperature and the film thickness at which the film is generated, it is possible to perform fine processing on the oxide superconducting thin film without taking it out from the film forming chamber. Therefore, according to the present invention, after forming the oxide superconducting thin film,
Since it is not necessary to take out the barrier layer material from the film forming chamber once for depositing the barrier layer substance and perform fine processing in another apparatus, continuous processing can be performed in the same film forming chamber. It maintains a state of being shielded from the atmosphere and does not give the oxide superconducting thin film an opportunity to come into direct contact with the atmosphere. Therefore, the obtained device is improved in stability of characteristics without being deteriorated by moisture or carbon dioxide in the atmosphere. Such continuous processing in the same deposition chamber causes a phase transition in which the physical properties of the oxide superconducting thin film change from normal conducting to superconducting, that is, the crystal structure of the oxide superconducting thin film changes from tetragonal to orthorhombic. This is caused by forming the oxide superconducting thin film under the film forming conditions in which the internal stress at the phase transition can generate cracks.
【０００９】[0009]
【実施例】以下に、本発明の実施例について添付図面を
参照して説明する。Embodiments of the present invention will be described below with reference to the accompanying drawings.
【００１０】本発明は平面型酸化物超電導薄膜ジョセフ
ソン素子を次のようにして作製するものである。まず、
結晶の面方向（１１０）の ＳｒＴｉＯ3 〔以下ＳＴＯ
（１１０）と略称する〕基板上にＲＦマグネトロンスパ
ッタ法を用いて、ＹＢａ2 Ｃｕ3 Ｏy （ｙは超電導体に
含まれる酸素量）〔以下ＹＢＣＯと略称する〕の薄膜を
６５０℃で堆積させて成膜する（成膜工程）。つぎに、
成膜室にＯ2 を導入し、酸素雰囲気中で薄膜形成温度か
ら室温まで冷却する（冷却工程）。この成膜後の冷却過
程において、ＹＢＣＯ膜の表面には、ＹＢＣＯ膜自身の
相転移、すなわち、結晶構造の正方晶から斜方晶への変
化に従ってＹＢＣＯ膜の組織がＣ軸方向へ収縮する応力
に起因して微細な亀裂が形成される。そして、亀裂が形
成されたＹＢＣＯ膜の表面に障壁層を形成するために、
成膜室内を真空に引き、室温でのスパッタ法により非晶
質のＹＢＣＯ膜を３００ｎｍ堆積させる（障壁層形成工
程）。このように、本発明の平面型ジョセフソン素子の
作製方法においては、従来のＸ線や電子線による微細加
工法がＹＢＣＯ膜の堆積後、これを一旦成膜室から取り
出して行なわねばならなかったのに対して、ＹＢＣＯ膜
自身の相転移時における応力により亀裂を形成すること
ができるので、成膜室を開封することなく、引き続き同
一成膜室内における連続的なスパッタ成膜を可能とした
ことを特徴としている。The present invention is to manufacture a planar oxide superconducting thin film Josephson device as follows. First,
SrTiO 3 in the crystal plane direction (110) [hereinafter referred to as STO
Abbreviated as (110)] A thin film of YBa 2 Cu 3 O y (y is the amount of oxygen contained in a superconductor) [hereinafter abbreviated as YBCO] is deposited on a substrate at 650 ° C. by using an RF magnetron sputtering method. To form a film (film forming step). Next,
O 2 is introduced into the film forming chamber and cooled from the thin film forming temperature to room temperature in an oxygen atmosphere (cooling step). In the cooling process after the film formation, a stress that causes the YBCO film structure to shrink in the C-axis direction on the surface of the YBCO film, that is, the phase transition of the YBCO film itself, that is, the structure of the YBCO film changes from tetragonal to orthorhombic. Due to the, fine cracks are formed. Then, in order to form a barrier layer on the surface of the YBCO film in which cracks are formed,
The film forming chamber is evacuated, and an amorphous YBCO film is deposited to a thickness of 300 nm by a sputtering method at room temperature (barrier layer forming step). As described above, in the method of manufacturing the planar Josephson device of the present invention, the conventional microfabrication method using X-rays or electron beams had to be performed after the YBCO film was deposited and then taken out from the film forming chamber. On the other hand, since cracks can be formed by the stress at the phase transition of the YBCO film itself, continuous sputter film formation in the same film formation chamber is possible without opening the film formation chamber. Is characterized by.
【００１１】このようにしてＳＴＯ（１１０）基板上に
ＹＢＣＯを成膜した後、障壁層として非晶質ＹＢＣＯ膜
を堆積して得られた素子構造のものについて、これをパ
ターニングした後、電極を設け電圧計および電流計を接
続した測定試料の模式図を図１（ａ），（ｂ）に示し
た。図１（ａ）は平面図、図１（ｂ）は断面図であり、
両図を併用参照して述べると、この測定試料は、基板１
上に堆積されたＹＢＣＯ膜２と障壁層を形成する非晶質
ＹＢＣＯ膜３からなる２層積層膜４を細長くして、亀裂
５を基板１のほぼ中央に位置させ、電流方向と亀裂５の
方向が直交するように、２層積層膜４の両端部に２つの
Ａｕ電極６を被着してあり、これらを測定用電流源７に
接続し、同様にして２層積層膜４のほぼ中央部で、亀裂
５を挟んで対向する２つのＡｕ電極８を被着し、これら
を測定用電圧計９に接続したものであることを示してい
る。The YBCO film was formed on the STO (110) substrate in this way, and the element structure obtained by depositing the amorphous YBCO film as the barrier layer was patterned. Schematic diagrams of measurement samples to which a voltmeter and an ammeter are provided are shown in FIGS. 1 (a) and 1 (b). 1A is a plan view and FIG. 1B is a sectional view.
Describing with reference to both figures together, this measurement sample is the substrate 1
The two-layer laminated film 4 composed of the YBCO film 2 deposited above and the amorphous YBCO film 3 forming the barrier layer is elongated, and the crack 5 is positioned substantially in the center of the substrate 1 so that the cracks 5 are formed in the current direction and the crack 5. Two Au electrodes 6 are attached to both ends of the two-layer laminated film 4 so that the directions thereof are orthogonal to each other, and these are connected to a measurement current source 7, and in the same manner, substantially the center of the two-layer laminated film 4 is attached. 2 shows that two Au electrodes 8 facing each other with the crack 5 sandwiched between them are connected to a measuring voltmeter 9.
【００１２】図１（ａ），（ｂ）に示す測定試料を用い
て、液体窒素温度（７７Ｋ）における電流−電圧特性を
調査し、その結果を図２に示す。図２において、線
（イ）は本発明の作製方法によって得られた素子の特性
線であり、線（ロ）は比較のために併記した従来の微細
加工法を用いて得られた素子の特性線である。但し、本
発明との相違を分かり易くするため、特性線（ロ）のみ
電流値を１００倍として表してある。この測定試料で
は、電流経路に対して垂直に亀裂５が入っているため、
流れている電流は亀裂５の部分に存在している非晶質Ｙ
ＢＣＯ膜３中をトンネルする準粒子トンネリングの直列
接続によるものであり、障壁層が非常に薄い場合、準粒
子トンネリング効果と同時にクーパー電子対のトンネル
も起こす。障壁層が非常に薄い場合の電流−電圧特性線
を図２に倣って図３に示す。一方、従来法により作製し
た素子、すなわち、薄膜形成後、一旦大気中に取り出し
て非晶質体を堆積させた素子の電流−電圧特性は非直線
性を示さずに、高抵抗体になるものがみられた。これは
微細加工部分の周囲が大気中に含まれる水分や炭酸ガス
により劣化され、非晶質体と超電導体との間に金属層が
生成されることに起因する。これに対して、本発明の方
法により作製した素子では、大気の影響を受けていない
から、そのような現象を起こすことなく、作製後１０日
間大気中に放置しても、特性の変化は観測されなかっ
た。以上のことから、特願平３−１１４０２９号により
出願中の平面型ジョセフソン素子の最高の特性が、本発
明の方法により効率よく容易に得ることができる。Using the measurement samples shown in FIGS. 1 (a) and 1 (b), the current-voltage characteristics at the liquid nitrogen temperature (77K) were investigated, and the results are shown in FIG. In FIG. 2, a line (a) is a characteristic line of the device obtained by the manufacturing method of the present invention, and a line (b) is a characteristic line of the device obtained by using the conventional microfabrication method described together for comparison. It is a line. However, in order to make it easy to understand the difference from the present invention, only the characteristic line (b) is shown with the current value being 100 times. In this measurement sample, the crack 5 is perpendicular to the current path,
The flowing current is the amorphous Y existing in the crack 5.
This is due to the series connection of quasi-particle tunneling tunneling through the BCO film 3, and when the barrier layer is very thin, a tunnel of Cooper electron pairs occurs simultaneously with the quasi-particle tunneling effect. A current-voltage characteristic line when the barrier layer is very thin is shown in FIG. 3 following FIG. On the other hand, an element manufactured by a conventional method, that is, an element in which a thin film is formed and then taken out into the air and an amorphous material is deposited thereon does not show non-linearity in current-voltage characteristics, but becomes a high resistance element. Was seen. This is because the periphery of the microfabricated portion is deteriorated by moisture and carbon dioxide contained in the atmosphere, and a metal layer is formed between the amorphous body and the superconductor. On the other hand, since the element manufactured by the method of the present invention is not affected by the atmosphere, a change in characteristics is observed even if the element is left in the atmosphere for 10 days after manufacturing without causing such a phenomenon. Was not done. From the above, the best characteristics of the planar Josephson device applied for a patent application No. 3-114029 can be efficiently and easily obtained by the method of the present invention.
【００１３】つぎに、超電導体としてＹＢＣＯ，絶縁体
としてＬａＳｒＧａ4 （以下ＬＳＧＯと略称する）を用
い、前述と同様にＲＦマグネトロンスパッタ法により、
亀裂を入れたＹＢＣＯ薄膜を形成後、成膜室を開封せず
に基板ホルダーをＬＳＧＯターゲット上に移動させて再
びスパッタを行ない、ＹＢＣＯ薄膜上にＬＳＧＯ薄膜を
３００ｎｍ堆積させ、図１（ａ），（ｂ）に示したもの
と同様の測定試料を作製して、液体窒素温度における電
流−電圧特性を測定した結果、図２とほぼ同様の線図が
得られた。Next, using YBCO as the superconductor and LaSrGa 4 (hereinafter abbreviated as LSGO) as the insulator, the RF magnetron sputtering method was used as described above.
After forming the cracked YBCO thin film, the substrate holder is moved to the LSGO target without opening the film formation chamber and sputtering is performed again to deposit the LSGO thin film to a thickness of 300 nm on the YBCO thin film, as shown in FIG. A measurement sample similar to that shown in (b) was prepared and the current-voltage characteristics at the liquid nitrogen temperature were measured. As a result, a diagram similar to that in FIG. 2 was obtained.
【００１４】図４（ａ），（ｂ）は図１（ａ），（ｂ）
に示した測定試料と基本的に同じ形状を持つ測定試料の
模式図であり、共通部分を同一符号で表してあるが、異
なる点は、図４に示す測定試料は、障壁層としてＡｕ１
０を用いたことである。この測定試料は次のようにして
作製したものである。ＳＴＯ（１１０）基板１上に、電
子ビーム反応性蒸着法によりＹＢＣＯ膜２を７００℃で
蒸着し成膜した後、Ｏ2 を導入して酸素雰囲気中で室温
まで冷却し、ＹＢＣＯ膜２の表面に亀裂を発生させる。
その後成膜室を開封せずに、再び成膜室内を真空に引
き、Ａｕ１０を室温で蒸着することにより、ＹＢＣＯ膜
２とＡｕ１０との２層膜を得、この２層膜をパターニン
グしＡｕ電極６，８を被着し、測定用電流源７と測定用
電圧計９に接続する。FIGS. 4 (a) and 4 (b) are shown in FIGS. 1 (a) and 1 (b).
4 is a schematic diagram of a measurement sample having basically the same shape as the measurement sample shown in FIG. 4, and common portions are represented by the same reference numerals, except that the measurement sample shown in FIG.
0 was used. This measurement sample is manufactured as follows. After the YBCO film 2 was deposited on the STO (110) substrate 1 by the electron beam reactive evaporation method at 700 ° C. to form a film, O 2 was introduced and the film was cooled to room temperature in an oxygen atmosphere to obtain the surface of the YBCO film 2. To crack.
Thereafter, without opening the film forming chamber, the film forming chamber is evacuated again and Au10 is vapor-deposited at room temperature to obtain a two-layer film of YBCO film 2 and Au10. The two-layer film is patterned to form an Au electrode. 6 and 8 are attached and connected to the measuring current source 7 and the measuring voltmeter 9.
【００１５】この測定試料を用いて液体窒素温度（７７
Ｋ）における電流−電圧特性を調査した結果を図５に示
す。図５において、線（イ）は本発明の作製方法によっ
て得られた素子の特性線であり、線（ロ）は比較のため
に併記した従来法を適用して得られた素子の特性線であ
る。この測定試料は図１のときと同様に、電流経路に対
して垂直に亀裂５が入っているため、流れている電流
は、亀裂５の部分に存在しているＡｕ１０中をクーパー
電子対がトンネルする近接効果によるものである。従来
法、すなわち、薄膜形成後、一度大気中に取り出して、
Ａｕを蒸着した素子は、超電導電流のばらつきが大きい
上に、臨界電流値は本発明の方法を用いたものより全て
小さい値を示した。これも前述と同様に、微細加工部分
の周囲が大気中に含まれる水分や炭酸ガスにより劣化さ
れるために、Ａｕと超電導体との間に生成される金属層
の厚さが増したことが原因である。本発明の方法を用い
た場合、素子作製後１０日間大気中に放置しても特性の
変化は観測されない。Using this measurement sample, the liquid nitrogen temperature (77
The result of having investigated the current-voltage characteristic in K) is shown in FIG. In FIG. 5, line (a) is the characteristic line of the element obtained by the manufacturing method of the present invention, and line (b) is the characteristic line of the element obtained by applying the conventional method described for comparison. is there. As in the case of FIG. 1, this measurement sample has a crack 5 perpendicular to the current path. Therefore, the flowing current causes the Cooper electron pair to tunnel through Au 10 existing in the crack 5 portion. This is due to the proximity effect. Conventional method, that is, after forming a thin film, once taken out into the atmosphere,
The elements vapor-deposited with Au had large variations in the superconducting current, and the critical current values were all smaller than those using the method of the present invention. Similarly to the above, since the periphery of the microfabricated portion is deteriorated by moisture and carbon dioxide contained in the atmosphere, the thickness of the metal layer generated between Au and the superconductor is increased. Responsible. When the method of the present invention is used, no change in characteristics is observed even if the device is left in the atmosphere for 10 days.
【００１６】さらに本発明の方法を用いる際、これまで
述べた超電導ＹＢＣＯとＹＢＣＯ非晶質体との組み合わ
せ、超電導ＹＢＣＯとＬＳＧＯ絶縁体との組み合わせ、
超電導ＹＢＣＯとＡｕとの組み合わせに関して、次のよ
うにしても同様の効果を得ることができる。Further, when using the method of the present invention, a combination of the superconducting YBCO and the YBCO amorphous body described above, a combination of the superconducting YBCO and the LSGO insulator,
With respect to the combination of superconducting YBCO and Au, the same effect can be obtained by the following.
【００１７】 全ての組み合わせについて、超電導Ｙ
ＢＣＯのＹを、Ｌａ，Ｓｍ，Ｅｕ，Ｇｄ，Ｄｙ，Ｈｏ，
Ｅｒ，Ｔｍ，ＹｂおよびＬｕのいずれかで置き換える。Superconducting Y for all combinations
Y of BCO is La, Sm, Eu, Gd, Dy, Ho,
Replace with any of Er, Tm, Yb and Lu.
【００１８】 ＹＢＣＯ非晶質体のＹを、Ｌａ，Ｓ
ｍ，Ｅｕ，Ｇｄ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，Ｙｂおよび
Ｌｕのいずれかで置き換える。Y of the YBCO amorphous body is represented by La, S
Replace with any of m, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu.
【００１９】 ＹＢＣＯ非晶質体の代わりに、Ｍｇ
Ｏ，ＺｒＯ2 ，ＳｒＴｉＯ3 ，ＢａＦ2 ，ＮｄＧａ
Ｏ3 ，ＹＡｌＯ3 ，ＬａＡｌＯ3 ，ＬａＧａＯ3 および
ＬａＳｒＧａＯ4 の非晶質体のいずれかを用いる。Instead of the YBCO amorphous body, Mg
O, ZrO 2 , SrTiO 3 , BaF 2 , NdGa
Any of O 3 , YAlO 3 , LaAlO 3 , LaGaO 3 and LaSrGaO 4 is used.
【００２０】 ＬＳＧＯ絶縁体の代わりに、ＭｇＯ，
ＺｒＯ2 ，ＳｒＴｉＯ3 ，ＢａＦ2，ＣａＦ2 ，ＮｄＧ
ａＯ3 ，ＹＡｌＯ3 ，ＬａＡｌＯ3 およびＬａＧａＯ3
の非晶質体のいずれかを用いる。Instead of the LSGO insulator, MgO,
ZrO 2 , SrTiO 3 , BaF 2 , CaF 2 , NdG
aO 3 , YAlO 3 , LaAlO 3 and LaGaO 3
One of the amorphous bodies is used.
【００２１】 Ａｕの代わりに、ＡｇおよびＰｔのい
ずれかを用いる。Instead of Au, either Ag or Pt is used.
【００２２】これらのうち、，についての結果を表
１，表２に示す。Of these, the results for and are shown in Tables 1 and 2.
【００２３】[0023]
【表１】 [Table 1]
【００２４】[0024]
【表２】 [Table 2]
【００２５】[0025]
【発明の効果】以上に説明したとおり、本発明に係る平
面型酸化物超電導薄膜ジョセフソン素子の作製方法は、
酸化物超電導薄膜の表面の微細加工を一旦成膜室から取
り出して、別の装置で行なうのではなく、酸化物超電導
薄膜の物性が常電導から超電導へ変わる相転移時におけ
る内部応力を利用して、成膜過程の冷却時に生ずる亀裂
として形成しているために、成膜室から取り出す必要が
なく、酸化物超電導薄膜が水分や炭酸ガスを含む大気に
直接曝されることがないので、素子の劣化を生じない。
従って、得られる平面型ジョセフソン素子の特性が向上
しその再現性も安定する。積層型ジョセフソン素子では
薄膜形成後、同一成膜室内で障壁層物質を堆積させるこ
とも行なわれているが、平面型のジョセフソン素子では
従来これを行なうのは容易ではなく、仮に可能であると
しても莫大な費用が想定される。本発明の方法は、酸化
物超電導薄膜自身の相転移時における内部応力が亀裂を
発生させる成膜条件に設定して酸化物超電導薄膜を形成
する素子作製過程において始めて成し得るものである。As described above, the method for manufacturing the planar oxide superconducting thin film Josephson element according to the present invention is
Rather than taking out the microfabrication of the surface of the oxide superconducting thin film once from the film forming chamber and performing it with another device, the internal stress at the phase transition when the physical properties of the oxide superconducting thin film change from normal conduction to superconductivity is used. Since the oxide superconducting thin film does not need to be taken out from the film forming chamber because it is formed as a crack generated during cooling during the film forming process, and the oxide superconducting thin film is not directly exposed to the atmosphere containing water and carbon dioxide gas, No deterioration occurs.
Therefore, the characteristics of the obtained flat type Josephson element are improved and the reproducibility thereof is stable. In the stacked Josephson device, it is also possible to deposit the barrier layer material in the same film forming chamber after forming the thin film, but in the case of the planar Josephson device, it is not easy to do so, and it is possible. However, enormous costs are expected. The method of the present invention can be performed for the first time in a device manufacturing process for forming an oxide superconducting thin film by setting film forming conditions in which internal stress at the phase transition of the oxide superconducting thin film itself causes cracking.
【図１】（ａ）は本発明の方法を適用し障壁層をＹＢＣ
Ｏとした測定試料を模式的に示す平面図、（ｂ）はその
断面図である。FIG. 1 (a) is a view of applying a method of the present invention to a YBC barrier layer.
The top view which shows typically the measurement sample set to O, (b) is the sectional view.
【図２】図１に示す測定試料の電流−電圧特性を従来法
を適用した試料との比較で示すグラフ図である。2 is a graph showing current-voltage characteristics of the measurement sample shown in FIG. 1 in comparison with a sample to which a conventional method is applied.
【図３】図１に示す測定試料において、障壁層の膜厚を
薄く作製した場合の電流−電圧特性を従来法を適用した
試料との比較で示すグラフ図である。3 is a graph showing the current-voltage characteristics of the measurement sample shown in FIG. 1 when the barrier layer was made thin, in comparison with the sample to which the conventional method was applied.
【図４】（ａ）は本発明の方法を適用し障壁層をＡｕと
した測定試料を模式的に示す平面図、（ｂ）はその断面
図である。4A is a plan view schematically showing a measurement sample to which the method of the present invention is applied and the barrier layer is Au, and FIG. 4B is a sectional view thereof.
【図５】図４に示す測定試料の電流−電圧特性を従来法
を適用した試料との比較で示すグラフ図である。5 is a graph showing current-voltage characteristics of the measurement sample shown in FIG. 4 in comparison with a sample to which a conventional method is applied.
１・・・基板 ２・・・ＹＢＣＯ膜 ３・・・非晶質ＹＢＣＯ膜 ４・・・２層積層膜 ５・・・亀裂 ６・・・Ａｕ電極 ７・・・測定用電流源 ８・・・Ａｕ電極 ９・・・測定用電圧計 １０・・・Ａｕ DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... YBCO film 3 ... Amorphous YBCO film 4 ... Two-layer laminated film 5 ... Crack 6 ... Au electrode 7 ... Measurement current source 8 ...・ Au electrode 9 ・ ・ ・ Voltmeter for measurement 10 ・ ・ ・ Au
───────────────────────────────────────────────────── フロントページの続き (72)発明者 津田 孝一 神奈川県川崎市川崎区田辺新田１番１号 富士電機株式会社内 (72)発明者 向江 和郎 神奈川県川崎市川崎区田辺新田１番１号 富士電機株式会社内 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koichi Tsuda 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Fuji Electric Co., Ltd. No. 1 inside Fuji Electric Co., Ltd.
Claims (9)
ｕ3 Ｏy （ＬｎはＬａ，Ｓｍ，Ｅｕ，Ｇｄ，Ｄｙ，Ｈ
ｏ，Ｅｒ，Ｔｍ，ＹｂおよびＬｕからなる群より選ばれ
た１種の元素、ｙは超電導体に含まれる酸素量）酸化物
超電導薄膜に、その成膜後の冷却過程で発生した亀裂を
有してなる平面型酸化物超電導薄膜ジョセフソン素子の
作製方法であって、 前記酸化物超電導薄膜をその成膜後の冷却過程で前記亀
裂が発生する成膜温度と膜厚とを設定して形成する成膜
工程と、その後の薄膜形成温度から室温まで酸素雰囲気
中で冷却する冷却工程と、この冷却工程の後に、成膜室
を再び真空状態にして前記薄膜表面に障壁層となる物質
を堆積させる障壁層形成工程と、を有することを特徴と
する平面型酸化物超電導薄膜ジョセフソン素子の作製方
法。1. LnBa 2 C formed on the front surface side of a substrate
u 3 O y (Ln is La, Sm, Eu, Gd, Dy, H
One element selected from the group consisting of o, Er, Tm, Yb and Lu, and y is the amount of oxygen contained in the superconductor.) The oxide superconducting thin film has cracks generated during the cooling process after the film formation. A method of manufacturing a planar oxide superconducting thin film Josephson element comprising: forming the oxide superconducting thin film by setting a film forming temperature and a film thickness at which the cracks are generated in a cooling process after the film formation. Film forming step, followed by a cooling step of cooling from the thin film forming temperature to room temperature in an oxygen atmosphere, and after this cooling step, the film forming chamber is evacuated again to deposit a substance to be a barrier layer on the thin film surface. And a step of forming a barrier layer, the method for producing a planar oxide superconducting thin film Josephson device.
質として絶縁体を用いることを特徴とする平面型酸化物
超電導薄膜ジョセフソン素子の作製方法。2. The method for manufacturing a planar oxide superconducting thin film Josephson element according to claim 1, wherein an insulator is used as the material to be the barrier layer.
であることを特徴とする平面型酸化物超電導薄膜ジョセ
フソン素子の作製方法。3. The method for manufacturing a planar oxide superconducting thin film Josephson element according to claim 2, wherein the insulator is crystalline.
ＭｇＯ，ＺｒＯ2 ，ＳｒＴｉＯ3 ，ＢａＦ2 ，Ｃａ
Ｆ2 ，ＮｄＧａＯ3 ，ＹＡｌＯ3 ，ＬａＡｌＯ3，Ｌａ
ＧａＯ3 およびＬａＳｒＧａＯ4 からなる群より選ばれ
た１種の絶縁体であることを特徴とする平面型酸化物超
電導薄膜ジョセフソン素子の作製方法。4. The crystalline insulator according to claim 3, wherein the crystalline insulator is MgO, ZrO 2 , SrTiO 3 , BaF 2 , Ca.
F 2 , NdGaO 3 , YAlO 3 , LaAlO 3 , La
A method for producing a planar oxide superconducting thin film Josephson element, which is one kind of insulator selected from the group consisting of GaO 3 and LaSrGaO 4 .
であることを特徴とする平面型酸化物超電導薄膜ジョセ
フソン素子の作製方法。5. The method for manufacturing a planar oxide superconducting thin film Josephson element according to claim 2, wherein the insulator is amorphous.
ＬｎＢａ2 Ｃｕ3 Ｏy （ＬｎはＬａ，Ｓｍ，Ｅｕ，Ｇ
ｄ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，ＹｂおよびＬｕからなる
群より選ばれた１種の元素、ｙは超電導体に含まれる酸
素量）であることを特徴とする平面型酸化物超電導薄膜
ジョセフソン素子の作製方法。6. The amorphous insulator according to claim 5, wherein the amorphous insulator is LnBa 2 Cu 3 O y (Ln is La, Sm, Eu, G
a planar oxide superconducting thin film Josephson characterized in that one element selected from the group consisting of d, Dy, Ho, Er, Tm, Yb and Lu, and y is the amount of oxygen contained in the superconductor) Manufacturing method of device.
ＭｇＯ，ＺｒＯ2 ，ＳｒＴｉＯ3 ，ＢａＦ2 ，Ｃａ
Ｆ2 ，ＮｄＧａＯ3 ，ＹＡｌＯ3 ，ＬａＡｌＯ3,LaGaO
3 およびＬａＳｒＧａＯ4 からなる群より選ばれた１種
の絶縁体であることを特徴とする平面型酸化物超電導薄
膜ジョセフソン素子の作製方法。7. The amorphous insulator according to claim 5, wherein the amorphous insulator is MgO, ZrO 2 , SrTiO 3 , BaF 2 , Ca.
F 2, NdGaO 3, YAlO 3 , LaAlO 3, LaGaO
3. A method for producing a planar oxide superconducting thin film Josephson element, which is one kind of insulator selected from the group consisting of 3 and LaSrGaO 4 .
質として金属を用いることを特徴とする平面型酸化物超
電導薄膜ジョセフソン素子の作製方法。8. The method for manufacturing a planar oxide superconducting thin film Josephson element according to claim 1, wherein a metal is used as the material for the barrier layer.
ｇおよびＰｔからなる群より選ばれた１種の金属である
ことを特徴とする平面型酸化物超電導薄膜ジョセフソン
素子の作製方法。9. The metal according to claim 8, wherein the metal is Au, A
1. A method for producing a planar oxide superconducting thin film Josephson element, which is one kind of metal selected from the group consisting of g and Pt.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4267338A JPH05211356A (en) | 1991-10-08 | 1992-10-06 | Manufacture of planar type oxide superconducting thin film josephson element |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3-259497 | 1991-10-08 | ||
| JP25949791 | 1991-10-08 | ||
| JP4267338A JPH05211356A (en) | 1991-10-08 | 1992-10-06 | Manufacture of planar type oxide superconducting thin film josephson element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05211356A true JPH05211356A (en) | 1993-08-20 |
Family
ID=26544156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4267338A Pending JPH05211356A (en) | 1991-10-08 | 1992-10-06 | Manufacture of planar type oxide superconducting thin film josephson element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05211356A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016146495A (en) * | 2010-03-18 | 2016-08-12 | 株式会社リコー | Coating liquid for forming insulator film, insulator film, manufacturing method for insulator film, and manufacturing method for semiconductor device |
| US10020374B2 (en) | 2009-12-25 | 2018-07-10 | Ricoh Company, Ltd. | Field-effect transistor, semiconductor memory display element, image display device, and system |
-
1992
- 1992-10-06 JP JP4267338A patent/JPH05211356A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10020374B2 (en) | 2009-12-25 | 2018-07-10 | Ricoh Company, Ltd. | Field-effect transistor, semiconductor memory display element, image display device, and system |
| US11271085B2 (en) | 2009-12-25 | 2022-03-08 | Ricoh Company, Ltd. | Field-effect transistor having amorphous composite metal oxide insulation film, semiconductor memory, display element, image display device, and system |
| JP2016146495A (en) * | 2010-03-18 | 2016-08-12 | 株式会社リコー | Coating liquid for forming insulator film, insulator film, manufacturing method for insulator film, and manufacturing method for semiconductor device |
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