Integrating atomic layer deposition and ultra-high vacuum physical vapor deposition for in situ fabrication of tunnel junctions

Journal Article · Tue Jul 15 00:00:00 EDT 2014 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4890286· OSTI ID:22308683

Malek, Gary A.; Lu, Rongtao; Han, Siyuan; Yu, Haifeng; Zhao, Shiping ^[1]

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1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

Atomic Layer Deposition (ALD) is a promising technique for growing ultrathin, pristine dielectrics on metal substrates, which is essential to many electronic devices. Tunnel junctions are an excellent example which require a leak-free, ultrathin dielectric tunnel barrier of typical thickness around 1 nm between two metal electrodes. A challenge in the development of ultrathin dielectric tunnel barriers using ALD is controlling the nucleation of dielectrics on metals with minimal formation of native oxides at the metal surface for high-quality interfaces between the tunnel barrier and metal electrodes. This poses a critical need for integrating ALD with ultra-high vacuum (UHV) physical vapor deposition. In order to address these challenges, a viscous-flow ALD chamber was designed and interfaced to an UHV magnetron sputtering chamber via a load lock. A sample transportation system was implemented for in situ sample transfer between the ALD, load lock, and sputtering chambers. Using this integrated ALD-UHV sputtering system, superconductor-insulator-superconductor (SIS) Nb-Al/Al{sub 2}O{sub 2}/Nb Josephson tunnel junctions were fabricated with tunnel barriers of thickness varied from sub-nm to ∼1 nm. The suitability of using an Al wetting layer for initiation of the ALD Al{sub 2}O{sub 3} tunnel barrier was investigated with ellipsometry, atomic force microscopy, and electrical transport measurements. With optimized processing conditions, leak-free SIS tunnel junctions were obtained, demonstrating the viability of this integrated ALD-UHV sputtering system for the fabrication of tunnel junctions and devices comprised of metal-dielectric-metal multilayers.

• OSTI ID: 22308683
• Journal Information: Review of Scientific Instruments, Vol. 85, Issue 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM OXIDES
ATOMIC FORCE MICROSCOPY
DIELECTRIC MATERIALS
ELECTRODES
ELLIPSOMETRY
JOSEPHSON JUNCTIONS
MAGNETRONS
METALS
NUCLEATION
PHYSICAL VAPOR DEPOSITION
PRESSURE RANGE MICRO PA
SPUTTERING
SUPERCONDUCTORS
TUNNEL EFFECT
VISCOUS FLOW