US4414738A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical lithographic technique for fabricating submicron-sized Josephson microbridges
Assignee: United States Department of the Navy
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Filing: 1981-02-02
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Granted: 1983-11-15
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Expires: 2001-02-02
Abstract
Abstract Planar superconducting-normal-superconducting (SNS) Josephson microbridgesnd superconducting quantum interference devices (SQUIDs) with bridge widths of about 0.2 microns and lengths of about 0.1 micron or less are fabricated with the aid of a technique referred to as "shadow evaporation". The procedure permits the submicron dimensions to be set by edge film thickness and slant evaporation angle, both of which can be accurately measured. Microbridges have been constructed with vanadium banks or electrodes and gold-titanium bridges, although other materials can be used including superconducting metals for the bridge. It is expected that a refined version of this technique would be suitable for repeated batch fabrication of single and multiple Josephson microbridges.
Inventors
- 👤 Edward C. Jelks
- 👤 George L. Kerber
- 👤 Howard A. Wilcox
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 14:12
CPC Classifications
H; H10; H10P; H10P76/00; H10P76/20; H10P76/202; H10N; H10N60/00; H10N60/01; H10N60/0912; Y; Y10; Y10S; Y10S438/00; Y10S438/942; Y10S438/944; Y10S505/00; Y10S505/825; Y10S505/917; Y10S505/922
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
268 words
A method of fabricating planar, Josephson microbridge devices and arrays of microbridge devices each microbridge device having a bridge dimensioned with a length and width each less than 0.3 micrometer and which extends between a first superconducting electrode and a second superconducting electrode all of which are disposed on a planar substrate, comprising: depositing a first layer of a metal on the substrate; disposing a first photoresist layer on top of at least a portion of the deposited first metal layer; etching the first deposited metal layer to undercut the photoresist layer; depositing a second metal layer on the substrate to define a submicron wide exposed substrate strip next to and beneath the photoresist layer, the depositing of the second metal layer is at a first acute angle to the normal of the substrate over the upper edge of the photoresist layer to define the dimensions of the exposed substrate strip; depositing the microbridge material on the exposed substrate strip to produce the submicron-sized microbridge, the depositing of the microbridge material is at a second acute angle to the normal of the substrate over the upper edge of the second deposited metal layer and under a lower exposed edge of the photoresist layer to define the lateral dimensions of the submicron-sized microbridge; dissolving the photoresist layer; and stripping away the first and second metal layers of the substrate to leave the submicron-sized bridge on the substrate, the submicron-sized bridge is included in a microbridge device by depositing the first and second superconducting electrodes along the submicron-sized microbridge to assure the creation of a submicron gap between the electrodes.
Claim 2
Independent Claim
268 words
A method of fabricating planar, Josephson microbridge devices and arrays of microbridge devices each microbridge device having a bridge dimensioned with a length and width each less than 0.3 micrometer and which extends between a first superconducting electrode and a second superconducting electrode all of which are disposed on a planar substrate, comprising: depositing a first layer of a metal on the substrate; disposing a first photoresist layer on top of at least a portion of the deposited first metal layer; etching the first deposited metal layer to undercut the photoresist layer; depositing a second metal layer on the substrate to define a submicron wide exposed substrate strip next to and beneath the photoresist layer, the depositing of the second metal layer is at a first acute angle to the normal of the substrate over the upper edge of the photoresist layer to define the dimensions of the exposed substrate strip; depositing the microbridge material on the exposed substrate strip to produce the submicron-sized microbridge, the depositing of the microbridge material is at a second acute angle to the normal of the substrate over the upper edge of the second deposited metal layer and under a lower exposed edge of the photoresist layer to define the lateral dimensions of the submicron-sized microbridge; dissolving the photoresist layer; and stripping away the first and second metal layers of the substrate to leave the submicron-sized bridge on the substrate, the submicron-sized bridge is included in a microbridge device by depositing the first and second superconducting electrodes along the submicron-sized microbridge to assure the creation of a submicron gap between the electrodes.
Claim 3
Dependent Claim
124 words
A method according to claim 1 in which the depositing of the first and second superconducting electrodes includes: applying a second photoresist layer over at least a portion of the submicron-sized microbridge and the substrate, treating second photoresist layer to create an undercut profile, depositing a superconducting metal layer over the second photoresist layer and onto an exposed portion of the submicron-sized microbridge and the substrate, removing the second photoresist layer and the part of the superconductor electrode metal layer covering it; depositing still more of the superconductor electrode metal layer at a third acute angle to the normal of the upper edge first deposited superconductor electrode metal layer to define a submicron gap between the superconductor electrode linked by the submicron wide bridge.
Claim 4
Dependent Claim
40 words
A method according to claim 2 in which the problems associated with photoresist distortion by heating are reduced by mounting the substrate on a copper plate and using thermally-conducting grease between the substrate and copper plate to promote heat flow.
Claim 5
Dependent Claim
32 words
A method according to claim 3 in which the superconducting metal is refractory and tensile therein is reduced by sandwiching a lead film between successive layers of the deposited superconducting electrode metal.
Claim 6
Dependent Claim
21 words
A method according to claim 4 in which the superconducting electrode is made of more than one layer of deposited vanadium.
Claim 7
Dependent Claim
15 words
A method according to claim 5 in which the vanadium layers sandwich a lead layer.
Claim 8
Dependent Claim
66 words
A method according to claim 6 in which the planar substrate is a silicon/silicon oxide substrate, the submicron-sized microbridge is a gold bridge deposited on the substrate, and a first and second vanadium electrodes are deposited on the substrate and portions of the gold bridge to expose a submicron-length of the gold bridge that extends across a submicron gap between the first and second vanadium electrodes.
Claim 9
Dependent Claim
30 words
A method according to claim 7 in which a titanium layer is interposed between the substrate and the gold microbridge to aid in adhesion of the gold to the substrate.
Claim 10
Dependent Claim
25 words
A method according to claim 8 in which the width of the gold microbridge is about 0.2 micrometers and the gap is about 0.1 micrometer.
Claim 11
Dependent Claim
31 words
A method according to claim 9 further including a compressive metal layer of lead deposited on at least one exposed surface of a vanadium layer to reduce a tensile stress buildup.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-14 | 1987-05-16 | 1987-11-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-14 | 1991-05-16 | 1991-11-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-14 | 1995-05-16 | 1995-11-15 | $7700.00 | Window Closed / Lapsed |