A study on the etching characteristics of magnetic tunneling junction materials using DC pulse-biased inductively coupled plasmas

Yang, Kyung Chae; Jeon, Min Hwan; Yeom, Geun Young

doi:10.7567/jjap.54.01ae01

Cited by 12 publications

(7 citation statements)

References 30 publications

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“…For example, a subtractive process will yield similar structures given that the top and bottom electrodes are grown, defined, and patterned using sputter deposition, optical lithography, and etching, respectively. Smaller dimensions can also be achieved via etching, while some extra attention will be required to avoid redepostion on the edges of the junction, a standard technique in magnetic tunnel junction fabrication [15].…”

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confidence: 99%

Overlap junctions for high coherence superconducting qubits

Long

et al. 2017

Applied Physics Letters

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Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ with Ar milling before the junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed. Superconducting devices implemented as quantum bits (qubits) are among the leading candidates for building quantum computers. Key elements in all types of superconducting qubits are Josephson junctions, which are the non-linear elements in the superconducting circuitry. This non-linearity separates the two lowest energy levels from higher excitations, forming a two-level system as the physical qubit. Coherence times of superconducting qubits have been increased significantly in both 2D and 3D geometries (∼10-100µs) [1][2][3][4][5]. These relatively long coherence times, combined with fast, high-fidelity gate schemes, have enabled the demonstration of quantum error detection with superconducting devices [6][7][8].While the design and fabrication for various other elements that form quantum circuits, i.e., resonators, shunt capacitors, and inductors, have been well studied and brought into line with standard cleanroom techniques, the preparation of the non-linear Josephson junction is still typically conducted separately on a device-by-device basis. In general, low participation ratios from both the Josephson junction and it's immediate surroundings are essential to the success of present-day superconducting qubits [4,9]. This goal is typically achieved by shrinking the junction size. These low-loss junctions have predominantly been fabricated using a multi-angle shadowevaporation (SE) technique, because it naturally yields small structures in a single step process and works well enough for demonstrations of small-scale circuits [10,11]. SE is also convenient in that the oxidation of the base electrode is conducted in-situ on the as-deposited film and, then immediately covered by the top electrode.To satisfy the requirement of scalability of quantum circuits, it is becoming critical to bring the junction fabrication step in line with standard fabrication techniques. This is difficult with the angle-dependence of the SE technique because it limits the wafer size for preparing junctions with tight margins. One possible avenue is to use overlap junctions, as shown in Ref. [12], where the two electrodes of Josephson junctions are prepared in separate steps. The coherence time...

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confidence: 99%

Overlap junctions for high coherence superconducting qubits

Long

et al. 2017

Applied Physics Letters

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“…In order to enhance the volatility of the byproducts, processing temperature over 350 °C is implemented [ 57 , 58 ], which is hazardous for high-performance MTJs. DC pulse-biased ICP etching conducted by Yang et al [ 59 ] proved to be efficient to reduce the redeposition. By introducing a 60% duty ratio of the DC pulse, decreased residue layer thickness was observed in CoPt/MgO/CoFeB structures compared to that etched with radio frequency continuous wave (RF CW) biasing.…”

Section: Failure Issues Due To Nanofabrication Of Magnetic Tunnel mentioning

confidence: 99%

Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy

et al. 2016

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Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ) becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM) for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high scalability, and easy integration into conventional complementary metal oxide semiconductor (CMOS) circuits. However, this device suffers from a number of failure issues, such as large process variation and tunneling barrier breakdown. The large process variation is an intrinsic issue for PMA-MTJ as it is based on the interfacial effects between ultra-thin films with few layers of atoms; the tunneling barrier breakdown is due to the requirement of an ultra-thin tunneling barrier (e.g., <1 nm) to reduce the resistance area for the spin transfer torque switching in the nanopillar. These failure issues limit the research and development of STT-MRAM to widely achieve commercial products. In this paper, we give a full analysis of failure mechanisms for PMA-MTJ and present some eventual solutions from device fabrication to system level integration to optimize the failure issues.

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“…In other cases, because of the spatial-dependent reactivity, for a cubic crystal of Prussian Blue analogues, the surfaces tend to be dissolved in the acidic/basic solution quicker than the corners and edges [22,74]. Although in situ etching methods have been extensively utilized [75][76][77][78][79], they are not suitable for investigating the differences between solid cubes and mesoframes because of the difficulties in controlling the size/shape and composition. Alternatively, post-etching provides opportunities for comparison of the solid cubes and mesoframes with similar size/shape and composition.…”

Section: Introductionmentioning

confidence: 99%

Structural Design and Properties of Coordination Polymers

Kostakis¹

2018

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Coordination polymers (CPs) or metalorganic frameworks (MOFs), have become one of the most prominent branches of inorganic and materials chemistry due to the extensive variety of their applications. This book covers a range of recent developments in coordination polymer chemistry. Wang and Chuang et al. report a reversible Single-Crystal-to-Single-Crystal structural transformation and sorption studies (Crystals 2017, 7(12), 364;

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A study on the etching characteristics of magnetic tunneling junction materials using DC pulse-biased inductively coupled plasmas

Cited by 12 publications

References 30 publications

Overlap junctions for high coherence superconducting qubits

Overlap junctions for high coherence superconducting qubits

Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy

Structural Design and Properties of Coordination Polymers

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