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WO1992020092A1 - Revetement de passivation pour dispositif supraconducteur a couches minces - Google Patents

Revetement de passivation pour dispositif supraconducteur a couches minces Download PDF

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Publication number
WO1992020092A1
WO1992020092A1 PCT/US1992/003832 US9203832W WO9220092A1 WO 1992020092 A1 WO1992020092 A1 WO 1992020092A1 US 9203832 W US9203832 W US 9203832W WO 9220092 A1 WO9220092 A1 WO 9220092A1
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WIPO (PCT)
Prior art keywords
superconductor
coating
polyimide
passivation
thallium
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.)
Ceased
Application number
PCT/US1992/003832
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English (en)
Inventor
William Levin Olson
Betty Florence Zuck
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Clearday Inc
Original Assignee
Superconductor Technologies Inc
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Filing date
Publication date
Application filed by Superconductor Technologies Inc filed Critical Superconductor Technologies Inc
Publication of WO1992020092A1 publication Critical patent/WO1992020092A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
    • H10N60/0661—Processes performed after copper oxide formation, e.g. patterning
    • H10N60/0716—Passivating

Definitions

  • This invention relates to the manufacture of.useful devices from high temperature superconducting thin films.
  • the invention relates to providing an effective passivation coating for thallium and YBCO thin film superconductors.
  • YBCO compounds alkaline earth metals and rare earth metals such as barium and yttrium in conjunction with copper, typically referred to as YBCO compounds. See, e.g., u, et al- Superconductivity at 93K in a New Mixed-Phase Y-Ba- Cu-0 Compound System at Ambient Pressure, Phys. Rev. Lett., Vol. 58, No. 9, pp. 908-910 (1987). After the YBCO compounds, compounds containing bismuth were discovered.
  • thallium based supercon ⁇ ductors have been prepared, generally where the composi ⁇ tions have various stoichiometries of thallium, calcium, barium, copper and oxygen.
  • the highest transition temperatures for superconductors have been observed in thallium containing compounds.
  • a number of Tl-based superconducting phases have been identified. See, e.g., G. Koren, A. Gupta and R.J. Baseman, Appl.Phys.Lett. 54, 1920 (1989).
  • transition tempera ⁇ tures range from 90K for TlCaBa-Cu_O ⁇ (the "1122 phase") to 123K for Tl 2 Ca 2 Ba 2 Cu-O ⁇ (the "2223 phase”) . Additionally, a number of different thallium based compounds have been identified, some of which include lead. All of these compounds will be collectively referred to as thallium containing superconductors.
  • High temperature superconductors have been prepared in a number of forms. The earliest forms were preparation of bulk materials, which were sufficient to determine the existence of the superconducting state and phases. More recently, thin films have been prepared, which have proved useful for making practical superconducting devices. Thin films of thallium and YBCO superconductors have been formed on various substrates. More particularly as to thallium superconductors, the applicant's assignee has successfully produced thin film thallium superconductors which are " epitaxial to the substrate. See, e.g. Preparation of Superconducting TICaBaCu Thin Films by Chemical Deposition, Olson et al. Applied Physics Letters 55, (2), 10 July 1989, pp.
  • passivation coatings are known both in the superconducting field, as well as other fields, such as semiconductor electronics. Traditionally, passivation coatings were used for scratch protection and corrosion resistance. Further, passivation coatings served to protect the device during assembly operations, which typically bring the film in contact with substances such as solders, fluxes, degreasing chemicals, encapsulation materials and the like.
  • Thin films of high temperature superconductors may have extremely rough surfaces, often with deviations of +/- 30% of the film thickness. This extreme surface roughness results in PVD coatings which are marked by pin holes or microcracks. Further, high temperature superconducting thin films sometimes lack chemical stability when subject to the high temperature and plasma environments often used to deposit PVD coatings.
  • a curable organic coating provides an effective passivation coating for superconductors.
  • a polyimide formulation has proved to be compatible with YBCO and thallium containing superconductors and to provide an effective passivation coating.
  • Probamide 412 a preimidized polyimide formulation from Ciba Geigy is used for passivation.
  • the superconducting thin film is cleaned in organic solvents and dried.
  • the Probamide 412 is spin coated on the film.
  • a coating in the range of 1- 50 microns thick at the center of the film is easily achievable.
  • the deposited coating is then preferably soft baked at 110°C for 15 minutes.
  • the coating may be lithographically patterned, the Probamide being photochemically active, being cross-linked by exposure to UV light.
  • Fig. 1 shows the unloaded Q as a function of device power for a thallium device, before and after coating with polyimide, at both- 5.6 GHz and 16.5 GHz at 77K.
  • Fig. 2 shows the unloaded Q as a function of the device power for a thallium resonator having a polyimide passivation coating processed at various temperatures for various times.
  • Fig. 3 shows the unloaded quality factor versus device power for a YBCO resonator having a polyimide passivation coating, annealed at various times and temperatures, at 2.4 GHz.
  • Fig. 4 shows the quality factor versus device power for a thallium resonator which is uncoated as compared to a thallium resonator having a polyimide passivation coating which was cycled 50 times in air from room temperature to 77K.
  • the passivation coating process consists of the steps of (1) preparation of the superconductor wafer (2) deposition of the passivation coating on the wafer, (3) optionally patterning the passivation coating, such as by lithography and (4) optionally post-baking the coating.
  • the passivation coating and process described herein is useful for presently known high temperature superconductors, and is described with specific reference to thallium superconductors and YBCO superconductors.
  • the film is first cleaned.
  • the film is washed for 10 seconds each in VLSI grade toluene, acetone, methanol, and isopropanol.
  • the film is dried at a sufficient temperature and time, such as 140 ⁇ C for 30 minutes, avoiding extremes of temperature which might cause film damage.
  • the film may be dried with nitrogen.
  • the film is then coated with a polyimide, in the preferred embodiment Probamide 412 from Ciba Geigy. Any conventional coating technique may be used. In the preferred embodiment, spin coating is used. A Headway Photoresist Spinner has been successfully employed. Using conventional techniques, the wafer is placed on the photoresist spinner chuck and centered. Then, approximately 60% of the wafer surface is coated with polyimide. The spinner is run at 500 rpm for 5 seconds, followed by a ramp up to 3500 rpm for 40 seconds.
  • a polyimide in the preferred embodiment Probamide 412 from Ciba Geigy. Any conventional coating technique may be used. In the preferred embodiment, spin coating is used. A Headway Photoresist Spinner has been successfully employed. Using conventional techniques, the wafer is placed on the photoresist spinner chuck and centered. Then, approximately 60% of the wafer surface is coated with polyimide. The spinner is run at 500 rpm for 5 seconds, followed by a ramp up to 3500
  • Probamide 412 has been formed at the center of the film.
  • the film plus coating is preferably soft baked at 110°C for 15 minutes on a temperature regulated hot plate. This soft bajke eliminates the solvents from the film, and prepares the structure for lithography.
  • any known lithographic technique consistent with these materials may be employed.
  • contact mask aligners may be employed to pattern the coating.
  • Aligner having a Hg lamp with a fluence of 2.1 mW/cm 2 at
  • the film is then placed in 50 mL of QZ3301 developer solution (gamma butyral lactone base solvent) for 1.5 minutes with constant agitation to remove the unexposed areas of polyimide. After removal from the developer, the film is dipped for 40 seconds in 50 mL of fresh developer, followed by emersion for 10 seconds in 50 mL of rinse solution, QZ3312. Immediately following • removal of the wafer from the rinse solution, the wafer is dried in ultrafiltered dry nitrogen. The wafer is then baked again for 1.5 hours at 140 ⁇ C to remove any remaining developer or rinse solvents. Optionally, heating may be done under vacuum to aid drying. At this point, the patterned polyimide layer is now ready for further processing, such as addition of metallization.
  • QZ3301 developer solution gamma butyral lactone base solvent
  • the film may be further heat treated to cross link the polyimide coating for stability at higher process temperatures. Generally, it has been found that temperatures less than 250 ⁇ C should be used to avoid damage to the film.
  • the disclosed passivation process and coating materials have proved to be particularly useful for microwave devices. Significantly, the passivation process and materials do not significantly degrade the performance of microwave devices formed from the superconducting films. Data obtained from devices manufactured according to the procedure of this invention are provided below.
  • Fig. 1 shows the unloaded quality factor (Q) of a thallium resonator device, both before and after coating with polyimide.
  • Fig. 2 shows the unloaded Q as a function of device power for a thallium resonator having a polyimide passivation coating which was processed at various times and temperatures. The measurements were made at 5.6 GHz at 77K. Device performance was not significantly impacted until processing at a temperature of 250 ⁇ C for 1 hour.
  • Fig. 3 shows the unloaded quality factor as a function of device power for a YBCO resonator having a polyimide passivation coating, subject to annealing at various times and temperatures.
  • the YBCO films obtained for the polyimide passivation were grown by in situ laser ablation techniques on lanthanum aluminate substrates. The films were patterned using wet chemical etch techniques to form 5.6 GHz resonators. As in the case for the thallium film results of Fig. 2, there is no significant degradation of properties until processing at 250°C.
  • Fig. 4 shows the quality factor as a function of device power for thallium resonators.
  • the square box with a dot shows the results for a thallium resonator without a passivation coating.
  • the black diamond shows the results for a thallium resonator coated by the process and polyimide coating of this invention, after thermally cycling the device 50 times in air from room temperature to 77K. The sample was cooled by placing it in liquid nitrogen. The sample was then removed and left in air. Significant condensation of water was present on the sample. Nevertheless, after cycling 50 times, the resonator performance was not degraded as shown by the results graphed in Fig. 4. In marked contrast, an unpassivated film subject to such extensive temperature cycling would have severely degraded.
  • a film coated in accordance with this invention was subject to hydrochloric acid (HC1) . Significantly, no pinholes, cracks or delaminations occurred during temperature cycling. The film remained intact through repeated acid treatments.
  • HC1 hydrochloric acid

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)

Abstract

Un revêtement pour dispositifs supraconducteurs à haute température se compose de polyimide. Dans le mode de réalisation préférée, on utilise le polyimide Probamide 412 afin de produire un revêtement de passivation pour des supraconducteurs au thallium ou YBCO (baryum et yttrium associés à du cuivre). On forme une structure locale plane que l'on peut utiliser comme base pour d'autres structures, telles que des métallisations. Un procédé de production d'un revêtement de passivation en polyimide sur des supraconducteurs comprend généralement les étapes consistant à recouvrir le supraconducteur de polyimide, facultativement à conférer un motif au polyimide selon des techniques photolithographiques, puis à durcir le polyimide en une étape de cuisson.
PCT/US1992/003832 1991-05-08 1992-05-08 Revetement de passivation pour dispositif supraconducteur a couches minces Ceased WO1992020092A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US69766091A 1991-05-08 1991-05-08
US697,660 1991-05-08

Publications (1)

Publication Number Publication Date
WO1992020092A1 true WO1992020092A1 (fr) 1992-11-12

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5635730A (en) * 1995-03-22 1997-06-03 Advanced Mobile Telecommunication Technology Inc. Superconducting oxide thin film device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6410677A (en) * 1987-07-03 1989-01-13 Hitachi Ltd Oxide superconducting integrated circuit
EP0301962A2 (fr) * 1987-07-27 1989-02-01 Sumitomo Electric Industries Limited Film mince supraconducteur of méthode pour fabriquer celui-ci
US4960751A (en) * 1987-04-01 1990-10-02 Semiconductor Energy Laboratory Co., Ltd. Electric circuit having superconducting multilayered structure and manufacturing method for same
US4997719A (en) * 1988-10-25 1991-03-05 Ube Industries, Ltd. Niobium-containing superconductor-laminated aromatic polyimide material
US5041880A (en) * 1988-06-16 1991-08-20 Sharp Kabushiki Kaisha Logic device and memory device using ceramic superconducting element

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4960751A (en) * 1987-04-01 1990-10-02 Semiconductor Energy Laboratory Co., Ltd. Electric circuit having superconducting multilayered structure and manufacturing method for same
JPS6410677A (en) * 1987-07-03 1989-01-13 Hitachi Ltd Oxide superconducting integrated circuit
EP0301962A2 (fr) * 1987-07-27 1989-02-01 Sumitomo Electric Industries Limited Film mince supraconducteur of méthode pour fabriquer celui-ci
US4942142A (en) * 1987-07-27 1990-07-17 Sumitomo Electric Industries Ltd. Superconducting thin film and a method for preparing the same
US5041880A (en) * 1988-06-16 1991-08-20 Sharp Kabushiki Kaisha Logic device and memory device using ceramic superconducting element
US4997719A (en) * 1988-10-25 1991-03-05 Ube Industries, Ltd. Niobium-containing superconductor-laminated aromatic polyimide material

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
APPLIED PHYSICS LETTER, Vol. 52, No. 4, 25 January 1988, BANSAL et al., "Chemical Durability of High-Temperature Superconductor Y-BA-CU-O in Aqueous Environments", pages 323-325. *
PATENT ABSTRACTS OF JAPAN; & JP,A,1 010 677, 13 January 1989. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5635730A (en) * 1995-03-22 1997-06-03 Advanced Mobile Telecommunication Technology Inc. Superconducting oxide thin film device

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