JPS6257115B2 - - Google Patents
Info
- Publication number
- JPS6257115B2 JPS6257115B2 JP55123985A JP12398580A JPS6257115B2 JP S6257115 B2 JPS6257115 B2 JP S6257115B2 JP 55123985 A JP55123985 A JP 55123985A JP 12398580 A JP12398580 A JP 12398580A JP S6257115 B2 JPS6257115 B2 JP S6257115B2
- Authority
- JP
- Japan
- Prior art keywords
- oxide film
- thin film
- oxygen
- gas
- frequency discharge
- 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
Links
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
- H10N60/01—Manufacture or treatment
- H10N60/0912—Manufacture or treatment of Josephson-effect devices
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Description
【発明の詳細な説明】
本発明はジヨセフソン素子の製造方法に関する
ものであり、特に超電導電極間に介挿されている
酸化膜で構成されたジヨセフソン接合素子の製造
方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a Josephson device, and particularly to a method for manufacturing a Josephson junction device composed of an oxide film interposed between superconducting electrodes.
超電導金属が薄い絶縁膜で隔てられていると
き、両者の間に電位差がなくても直流電流が流
れ、またバイアスをかけると電圧と比例した周波
数の交流が発生するというジヨセフソン効果が知
られている。このジヨセフソン効果は種々の分野
に応用され、ジヨセフソン接合素子の製造方法も
種々検討されている。 It is known that when superconducting metals are separated by a thin insulating film, a direct current flows even if there is no potential difference between them, and when a bias is applied, an alternating current with a frequency proportional to the voltage is generated.The Josephson effect is known. . This Josephson effect has been applied to various fields, and various methods of manufacturing Josephson junction devices have been studied.
従来のジヨセフソン接合素子の製造方法によれ
ば、下層電極となる超伝導薄膜が蒸着等の方法に
よつて予め形成されている基板を真空槽内の高周
波放電用電極に取付け、酸素又は酸素を含む混合
ガス雰囲気中で高周波放電を起こして上記の超伝
導薄膜表面にトンネル層となる酸化薄膜を形成
し、次にその酸化薄膜表面に、上層電極となる第
２の超伝導薄膜を形成する工程によつて上層下層
の超伝導電極とそれらの間に介挿される酸化膜で
構成されるジヨセフソン接合素子が製造される。
この製造方法では上記酸化膜を形成する前に、上
記下層電極表面の汚染物質を除去することを目的
にアルゴンガス雰囲気中で高周波放電を起こし、
プラズマエツチングによつて下層電極表面を清浄
する方法も用いられる。 According to the conventional manufacturing method of Josephson junction devices, a substrate on which a superconducting thin film serving as a lower layer electrode has been formed in advance by a method such as vapor deposition is attached to a high-frequency discharge electrode in a vacuum chamber, and a superconducting thin film containing oxygen or oxygen is attached to a high-frequency discharge electrode in a vacuum chamber. A step of generating a high-frequency discharge in a mixed gas atmosphere to form an oxide thin film that will become a tunnel layer on the surface of the superconducting thin film, and then forming a second superconducting thin film that will become an upper layer electrode on the surface of the oxide thin film. In this way, a Josephson junction element is manufactured which is comprised of upper and lower superconducting electrodes and an oxide film interposed between them.
In this manufacturing method, before forming the oxide film, high-frequency discharge is generated in an argon gas atmosphere for the purpose of removing contaminants on the surface of the lower electrode.
A method of cleaning the lower electrode surface by plasma etching is also used.
この従来の製造方法は第１図に示すように高周
波放電による酸化膜の形成が放電開始直後に急激
に進行する。従つて膜厚が均一なピンホールの少
ない緻密な酸化膜が形成されにくいという欠点が
ある。またアルゴンガス雰囲気中でのプラズマエ
ツチングによつて上記の下層電極表面を清浄にし
た後、酸素又は酸素を含む混合ガス雰囲気中での
高周波放電を開始するまでの間に清浄な上記下層
電極表面が真空槽内の残留ガスによつて汚染され
るという欠点がある。 In this conventional manufacturing method, as shown in FIG. 1, the formation of an oxide film due to high frequency discharge rapidly progresses immediately after the start of discharge. Therefore, there is a drawback that it is difficult to form a dense oxide film with a uniform thickness and few pinholes. Furthermore, after the surface of the lower electrode is cleaned by plasma etching in an argon gas atmosphere, the clean surface of the lower electrode is removed before starting high frequency discharge in an atmosphere of oxygen or a mixed gas containing oxygen. It has the disadvantage of being contaminated by residual gas in the vacuum chamber.
そこで本発明は上記欠点を解消して、超伝導薄
膜表面に膜厚が均一で且つピンホールの少ない緻
密な酸化膜を形成する方法を提供することを目的
とする。 SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for eliminating the above drawbacks and forming a dense oxide film with a uniform thickness and few pinholes on the surface of a superconducting thin film.
本発明の目的は下層及び上層の超伝導薄膜とそ
れらにはさまれた前記下層薄膜表面上の酸化膜と
から構成され、且つ前記酸化膜が酸素を含む雰囲
気中での高周波放電によつて前記下層薄膜表面上
に形成されるジヨセフソン接合素子の製造方法に
おいて、酸素を含まない雰囲気中での高周波放電
に前記下層薄膜をさらした後前記高周波放電を停
止することなく、前記雰囲気の一部又は全部を徐
徐に酸素ガスに置換し酸化膜を形成することを特
徴とするジヨセフソン素子の製造方法によつて達
成される。 An object of the present invention is to provide a superconducting thin film comprising a lower layer and an upper layer superconducting thin film and an oxide film on the surface of the lower layer thin film sandwiched therebetween, and in which the oxide film is formed by high frequency discharge in an oxygen-containing atmosphere. In a method for manufacturing a Josephson junction device formed on a surface of a lower layer thin film, after exposing the lower layer thin film to a high frequency discharge in an oxygen-free atmosphere, without stopping the high frequency discharge, part or all of the atmosphere is exposed. This is achieved by a method for manufacturing a Josephson device, which is characterized by gradually replacing oxygen gas with oxygen gas to form an oxide film.
以下本発明を詳細に説明する。 The present invention will be explained in detail below.
基板上に下層電極となる超電導薄膜を蒸着、ス
パツタ等の方法で付着させ、リフトオフ、等の方
法で下層電極としてのパターンを形成する。この
工程では超電導薄膜表面上に膜厚10Åの酸化膜が
形成され、その酸化膜表面は、ウエツトな工程の
際に汚染される。次に前記基板を真空槽（ベルジ
ヤー）内に設けられた高周波放電用電極に取りつ
け、10-6Torr以下の高真空に真空槽内を排気す
る。次に希ガス、窒素ガス、好ましくはアルゴン
ガスをガス圧１×10-3〜１×10-1Torrで真空槽内
に導入し高周波放電を発生させる。その際の放電
電力0.05〜5W／cm2、放電時間１〜10分で超電導
薄膜上に形成されていた酸化膜は真空槽内に導入
された希ガス等のイオンのエツチング効果によつ
て除去せしめられ超伝導薄膜の清浄な面を露出す
る。 A superconducting thin film that will become a lower layer electrode is deposited on the substrate by a method such as vapor deposition or sputtering, and a pattern as a lower layer electrode is formed by a method such as lift-off. In this process, an oxide film with a thickness of 10 Å is formed on the surface of the superconducting thin film, and the oxide film surface is contaminated during the wet process. Next, the substrate is attached to a high-frequency discharge electrode provided in a vacuum chamber (belgear), and the inside of the vacuum chamber is evacuated to a high vacuum of 10 -6 Torr or less. Next, a rare gas, nitrogen gas, preferably argon gas, is introduced into the vacuum chamber at a gas pressure of 1×10 -3 to 1×10 -1 Torr to generate a high frequency discharge. At a discharge power of 0.05 to 5 W/cm 2 and a discharge time of 1 to 10 minutes, the oxide film formed on the superconducting thin film is removed by the etching effect of ions such as rare gases introduced into the vacuum chamber. to expose the clean surface of the superconducting thin film.
次に放電電力を初めてそれの1/5〜1/100に低下
させた後徐々に希ガスの一部又は全部を酸素ガス
に置換してゆき超伝導薄膜表面上を酸化する。酸
素ガスを徐々に置換して該薄膜を酸化することに
より従来のような急激な酸化膜形成は行なわれず
安定した品質の酸化膜が形成される。しかしなが
ら酸素ガス導入当初は微量の酸素ガスでも酸化が
進行するので酸素ガス分圧を時間と共に指数関数
的に増加させる等の方法により酸素ガス分圧を
徐々に増加させるように注意をする必要がある。
酸素分圧が目的の分圧比になつた時点で分圧比を
固定する。所望の酸化膜の膜厚が形成された後、
真空槽内を10-6Torr以下の高真空に排気して上
記の酸化膜上に上層の電極となる超伝導薄膜を蒸
着、スパツタ等によつて形成する。この一連の方
法によつて清浄な緻密な酸化膜をトンネル層とし
て有するジヨセフソン接合素子が製造出来る。 Next, the discharge power is first lowered to 1/5 to 1/100 of that, and then part or all of the rare gas is gradually replaced with oxygen gas to oxidize the surface of the superconducting thin film. By gradually replacing oxygen gas to oxidize the thin film, an oxide film of stable quality is formed without forming an oxide film as rapidly as in the conventional method. However, when oxygen gas is initially introduced, oxidation progresses even with a small amount of oxygen gas, so care must be taken to gradually increase the oxygen gas partial pressure by increasing the oxygen gas partial pressure exponentially over time. .
The partial pressure ratio is fixed when the oxygen partial pressure reaches the desired partial pressure ratio. After the desired oxide film thickness is formed,
The inside of the vacuum chamber is evacuated to a high vacuum of 10 -6 Torr or less, and a superconducting thin film that will become the upper layer electrode is formed on the oxide film by vapor deposition, sputtering, or the like. Through this series of methods, a Josephson junction device having a clean, dense oxide film as a tunnel layer can be manufactured.
本発明の方法によれば超伝導薄膜間の酸化膜は
膜厚が従来より均一なピンホールの少ない清浄な
緻密なものが形成される。 According to the method of the present invention, the oxide film between the superconducting thin films is a clean, dense film with a uniform thickness and fewer pinholes than in the past.
以下実施例を示す。 Examples are shown below.
シリコン基板上に下層電極となるPb−In−Au
合金を蒸着し、リフトオフ法によつて下層電極と
してのパターンを形成し次にシリコン基板をベル
ジヤー内の高周波放電用電極に配置して
10-6Torr以下に排気する。その後アルゴンを１
×10-2Torrのガス圧でベルジヤー内に導入し高
周波放電を起す。0.3W／cm2の放電電力で２分間
放電を行なう。この時アルゴンイオンのエツチン
グ効果により、Pb−In−Au薄膜の清浄な面が得
られる。次に放電電力を初めの1/10である
0.3W／cm2に下げ、アルゴンと酸素ガスのガス圧
の和を１×10-2Torrに保ちつつアルゴンを酸素
ガスに徐々に置換しPb−In−Au薄膜を酸化す
る。第２図に放電時間と酸化膜厚との関係を示
す。酸素を導入10分後酸化膜厚が約50Åに達す
る。この方法により膜厚が均一でピンホールもな
く緻密な酸化膜が得られる。 Pb-In-Au as the lower layer electrode on the silicon substrate
The alloy is vapor-deposited, a pattern is formed as a lower layer electrode using the lift-off method, and then the silicon substrate is placed on the high-frequency discharge electrode in the bell jar.
Exhaust to below 10 -6 Torr. Then add 1 argon
A gas pressure of ×10 -2 Torr is introduced into the bell jar to generate a high-frequency discharge. Discharge is performed for 2 minutes with a discharge power of 0.3W/cm 2 . At this time, due to the etching effect of argon ions, a clean surface of the Pb-In-Au thin film can be obtained. Next, the discharge power is 1/10 of the initial value.
The Pb-In-Au thin film is oxidized by lowering the pressure to 0.3 W/cm 2 and gradually replacing argon with oxygen gas while keeping the sum of the gas pressures of argon and oxygen gas at 1×10 −2 Torr. FIG. 2 shows the relationship between discharge time and oxide film thickness. Ten minutes after introducing oxygen, the oxide film thickness reaches approximately 50 Å. By this method, a dense oxide film with uniform thickness and no pinholes can be obtained.
第１図は従来の製法による酸化膜厚の放電時間
依存性を示すグラフであり、第２図は本発明に係
る酸化膜厚の放電時間依存性を示すグラフであ
る。
FIG. 1 is a graph showing the discharge time dependence of the oxide film thickness according to the conventional manufacturing method, and FIG. 2 is a graph showing the discharge time dependence of the oxide film thickness according to the present invention.
Claims (1)
た前記下層薄膜表面上の酸化膜とから構成され、
且つ前記酸化膜が酸素を含む雰囲気中での高周波
放電によつて前記下層薄膜表面上に形成されるジ
ヨセフソン接合素子の製造方法に於て、 酸素を含まない雰囲気中での高周波放電に前記
下層薄膜をさらした後、前記高周波放電を停止す
ることなく、前記雰囲気中に徐々に酸素を導入
し、酸化膜を形成することを特徴とするジヨセフ
ソン素子の製造方法。[Scope of Claims] 1 Consisting of a lower layer and an upper layer superconducting thin film and an oxide film on the surface of the lower layer thin film sandwiched therebetween,
In the method for manufacturing a Josephson junction element, the oxide film is formed on the surface of the lower thin film by high frequency discharge in an oxygen-containing atmosphere, 1. A method for manufacturing a Josephson device, characterized in that after exposing the atmosphere, oxygen is gradually introduced into the atmosphere without stopping the high-frequency discharge to form an oxide film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55123985A JPS5749285A (en) | 1980-09-09 | 1980-09-09 | Production of josephson junction element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55123985A JPS5749285A (en) | 1980-09-09 | 1980-09-09 | Production of josephson junction element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5749285A JPS5749285A (en) | 1982-03-23 |
| JPS6257115B2 true JPS6257115B2 (en) | 1987-11-30 |
Family
ID=14874181
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP55123985A Granted JPS5749285A (en) | 1980-09-09 | 1980-09-09 | Production of josephson junction element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5749285A (en) |
-
1980
- 1980-09-09 JP JP55123985A patent/JPS5749285A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5749285A (en) | 1982-03-23 |
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