US4412902A
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Method of fabrication of Josephson tunnel junction
Assignee: NTT Inc
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Filing: 1982-06-18
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Granted: 1983-11-01
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Expires: 2002-06-18
Abstract
Abstract There is disclosed a method of fabrication of a Josephson tunnel junction device. A surface of a base electrode of Nb or Nb compound is subjected to sputter cleaning and then to plasma oxidation in an atmosphere of a diluent gas and oxygen to form thereon an oxide layer serving as a tunnel barrier. A counter electrode is then formed on the oxide layer to provide the Josephson tunnel junction.
Inventors
- 👤 Osamu Michikami
- 👤 Yujiro Katoh
- 👤 Keiichi Tanabe
- 👤 Hisataka Takenaka
- 👤 Shizuka Yoshii
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 05:01
CPC Classifications
H; H10; H10N; H10N60/00; H10N60/01; H10N60/0912; Y; Y10; Y10S; Y10S505/00; Y10S505/80; Y10S505/815; Y10S505/816; Y10S505/817
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
139 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film to sputter cleaning in the presence of a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoroethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ) and pentafluoroethane (C 2 HF 5 ); (c) oxidizing the cleaned surface of the base electrode in the presence of a gas mixture of oxygen and inert gas to form an oxide layer on the base electrode; and (d) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 2
Independent Claim
139 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film to sputter cleaning in the presence of a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoroethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ) and pentafluoroethane (C 2 HF 5 ); (c) oxidizing the cleaned surface of the base electrode in the presence of a gas mixture of oxygen and inert gas to form an oxide layer on the base electrode; and (d) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 3
Dependent Claim
26 words
A method according to claim 1, in which the substrate is made of silicon which has an oxidized surface on which the base electrode is formed.
Claim 4
Dependent Claim
14 words
A method according to claim 1, in which the substrate is made of sapphire.
Claim 5
Dependent Claim
33 words
A method according to claim 1, in which the first superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, and Pb--In.
Claim 6
Dependent Claim
34 words
A method according to claim 1, in which the second superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, Pb, and Pb--In.
Claim 7
Dependent Claim
53 words
A method according to claim 1, in which the halogenated hydrocarbon is selected from the group consisting of tetrafluoromethane (CF 4 )--50 volume % trichlorofluoromethane (CCl 3 F), hexafluoroethane (C 2 F 6 )--20 volume % tetrafluoromethane (CF 4 ), and octafluoropropane (C 3 F 8 )--80 volume % trifluorobromomethane (CBrF 3 ).
Claim 8
Dependent Claim
33 words
A method according to claim 1, in which the inert gas used for the gas mixture in the oxidation step is selected from the group consisting of helium, argon, neon, xenon and krypton.
Claim 9
Dependent Claim
25 words
A method according to claim 1, in which the halogenated hydrocarbon in the sputter cleaning step is at a pressure of 0.5 to 0.005 Torr.
Claim 10
Dependent Claim
24 words
A method according to claim 1, in which the sputter cleaning step is carried out at a cathode voltage of 50 to 300 V.
Claim 11
Dependent Claim
26 words
A method according to claim 1, in which the oxidation of the cleaned surface of the base electrode is carried out by a plasma oxidation method.
Claim 12
Dependent Claim
29 words
A method according to claim 1, in which the oxidation of the cleaned surface of the base electrode is carried out by a natural oxidation method at room temperature.
Claim 13
Dependent Claim
29 words
A method according to claim 1, in which the pressure of the gas mixture of oxygen and inert gas in the oxidation step is between 0.005 to 0.08 Torr.
Claim 14
Dependent Claim
22 words
A method according to claim 1, in which the gas mixture in the oxidation step contains 4 to 20 volume % oxygen.
Claim 15
Independent Claim
143 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film to sputter cleaning in the presence of a diluent gas and a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoromethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ), and pentafluoroethane (C 2 HF 5 ); (c) oxidizing the cleaned surface of the base electrode in the presence of a gas mixture of oxygen and inert gas to form an oxide layer on the base electrode; and (d) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 16
Independent Claim
143 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film to sputter cleaning in the presence of a diluent gas and a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoromethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ), and pentafluoroethane (C 2 HF 5 ); (c) oxidizing the cleaned surface of the base electrode in the presence of a gas mixture of oxygen and inert gas to form an oxide layer on the base electrode; and (d) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 17
Dependent Claim
26 words
A method according to claim 14, in which the substrate is made of silicon which has an oxidized surface on which the base electrode is formed.
Claim 18
Dependent Claim
14 words
A method according to claim 14, in which the substrate is made of sapphire.
Claim 19
Dependent Claim
33 words
A method according to claim 14, in which the first superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, and Pb--In.
Claim 20
Dependent Claim
34 words
A method according to claim 14, in which the second superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, Pb, and Pb--In.
Claim 21
Dependent Claim
53 words
A method according to claim 14, in which the halogenated hydrocarbon is selected from the group consisting of tetrafluoromethane (CF 4 )--50 volume % trichlorofluoromethane (CCl 3 F), hexafluoroethane (C 2 F 6 )--20 volume % tetrafluoromethane (CF 4 ), and octafluoropropane (C 3 F 8 )--80 volume % trifluorobromomethane (CBrF 3 ).
Claim 22
Dependent Claim
33 words
A method according to claim 14, in which the inert gas used for the gas mixture in the oxidation step is selected from the group consisting of helium, argon, neon, xenon and krypton.
Claim 23
Dependent Claim
40 words
A method according to claim 14, in which the halogenated hydrocarbon in the sputter cleaning step is at a pressure of 0.5 to 0.005 Torr, the sputter cleaning being carried out at a cathode voltage of 50 to 300 V.
Claim 24
Dependent Claim
26 words
A method according to claim 14, in which the oxidation of the cleaned surface of the base electrode is carried out by a plasma oxidation method.
Claim 25
Dependent Claim
29 words
A method according to claim 14, in which the oxidation of the cleaned surface of the base electrode is carried out by a natural oxidation method at room temperature.
Claim 26
Dependent Claim
22 words
A method according to claim 14, in which the gas mixture in the oxidation step contains 4 to 20 volume % oxygen.
Claim 27
Dependent Claim
30 words
A method according to claim 14, in which the diluent gas is selected from the group consisting of helium, neon, argon, krypton, xenon, carbon monoxide, carbon dioxide, methane, and nitrogen.
Claim 28
Independent Claim
132 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film simultaneously to sputter cleaning and oxidation in the presence of a gas mixture of a diluent gas, oxygen, and a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoromethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ) and pentafluoroethane (C 2 HF 5 ), so that an oxide layer is formed on the base electrode; and (c) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 29
Independent Claim
132 words
A method for the fabrication of a Josephson tunnel junction device which comprises the steps of: (a) forming a base electrode film of a first superconductor metal on a substrate; (b) subjecting a surface of the base electrode film simultaneously to sputter cleaning and oxidation in the presence of a gas mixture of a diluent gas, oxygen, and a halogenated hydrocarbon selected from the group consisting of fluorinated hydrocarbons (CnF 2n+2 :n=1˜4), trifluoromethane (CHF 3 ), trichlorofluoromethane (CCl 3 F), trifluorobromomethane (CBrF 3 ), dichlorodifluoromethane (CCl 2 F 2 ), trifluoroethane (C 2 H 3 F 3 ) and pentafluoroethane (C 2 HF 5 ), so that an oxide layer is formed on the base electrode; and (c) forming a counter electrode film of a second superconductor metal on the oxide layer.
Claim 30
Dependent Claim
34 words
A method according to claim 26, in which the first superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, Pb, and Pb--In.
Claim 31
Dependent Claim
34 words
A method according to claim 26, in which the second superconductor metal is at least one metal selected from the group consisting of Nb, Nb--Al, Nb--Ge, Nb--Sn, Nb--Ga, V--Si, Nb--C--N, Nb--N, Pb, and Pb--In.
Claim 32
Dependent Claim
30 words
A method according to claim 26, in which the diluent gas is selected from the group consisting of helium, neon, argon, krypton, xenon, carbon monoxide, carbon dioxide, methane, and nitrogen.
Claim 33
Dependent Claim
58 words
A method according to claim 26, in which the gas mixture in the oxidation step contains 4 to 20 volume % oxygen, the total pressure of the gas mixture is 0.005 to 0.06 Torr, and the sputter cleaning and the oxidation is carried out at a cathode voltage of 40 to 150 V for 1 to 20 minutes.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-10-31 | 1987-05-02 | 1987-11-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-10-31 | 1991-05-02 | 1991-11-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-10-31 | 1995-05-02 | 1995-11-01 | $7700.00 | Window Closed / Lapsed |