Effects of Stress and Morphology on the Resistivity and Critical Temperature of Room-Temperature-Sputtered Mo Thin Films

Fàbrega, L.; Fernández-Martínez, Iván; Parra-Borderías, María; Gil, O.; Camón, A.; González-Arrabal, R.; Sesé, J.; Santiso, J.; Costa-Kramer, J.L.; Briones, F.

doi:10.1109/tasc.2009.2027609

Cited by 27 publications

(24 citation statements)

References 34 publications

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“…Over a wide range of deposition conditions, T c appears to be closely correlated with resistivity, which in turn is believed to be dominated by grain-boundary scattering. The observed correlation agrees with that typically observed for sputtered films 4,9 and can be understood by considering that disorder in the film smears the the electronic density of states, thus, for Mo leading to an enhancement of the density of states at the Fermi level 10,11 . Additionally, disorder could soften the phonon spectrum 12 .…”

Section: Ion-beam Assisted Deposition Of Mo Filmssupporting

confidence: 87%

“…Two techniques are in common use for the deposition of high quality bilayers: a) e-beam evaporation onto heated substrates for Mo/Au 1 , and b) sputter deposition at room temperature for Mo/Cu 2,3,4,5 . While in principle the bilayer fabrication should be straightforward, in practice reproducibility remains a significant challenge, partly because the interactions of various process and materials parameters are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

et al. 2016

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Superconducting/normal metal bilayers with tunable transition temperature are a critical ingredient to the fabrication of high performance transition edge-sensors (TES). Popular material choices include Mo/Au and Mo/Cu, which exhibit good environmental stability and provide low resistivity films to achieve adequate thermal conductivity. The deposition of high quality Mo films requires sufficient adatom mobility, which can be provided by energetic ions in sputter deposition, or by heating the substrate in an e-beam evaporation process. The bilayer Tc depends sensitively on the exact deposition conditions of the Mo layer and the superconducting/normal metal interface. Because the individual contributions (strain, crystalline structure, contamination) are difficult to disentangle and control, reproducibility remains a challenge. Recently, we have demonstrated that low energy ion beam assist during e-beam evaporation offers an alternative route to reliably produce high quality Mo films without the use of substrate heating. The energy and momentum delivered by the ion beam provides an additional control knob to tune film properties such as resistivity and stress. In this report we describe modifications made to the commercial end-Hall ion-source to avoid iron contamination allowing us to produce superconducting Mo films. We show that the ion beam is effective at enhancing the bilayer interface transparency and that bilayers can be further tuned to reduced Tc and higher conductivity by vacuum annealing.

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Section: Ion-beam Assisted Deposition Of Mo Filmssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

et al. 2016

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“…We have found through careful control of film thickness uniformity and stress, that using this method we can achieve sufficiently repeatable results [5]. The effects of deposition conditions on Mo Tc have been studied in [6]. We have additionally found that the silicon surface condition can affect the Mo transition temperature by changing the as-deposited Mo film stress for identical deposition conditions.…”

Section: Fig 1 Fabrication Flowmentioning

confidence: 99%

Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

Denis¹,

Ali²,

Appel³

et al. 2015

J Low Temp Phys

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Characterization of the minute cosmic microwave background polarization signature requires multi-frequency, high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of detector modules for measurement of the CMB at 90 GHz. The 90 GHz detectors are a scaled version of the 40 GHz architecture where, due to smaller size detectors, we have implemented a modular (wafer level) rather than the chip-level architecture. The new fabrication process utilizes the same design rules with the added challenge of increased wiring density to the 74 TES's as well as a new wafer level hybridization procedure. The hexagonally shaped modules are tile-able, and as such can be used to form the large focal planes required for a space-based CMB polarimeter. The detectors described here will be deployed in two focal planes with seven modules each in the Johns Hopkins University led ground-based Cosmology Large Angular Scale Surveyor (CLASS) telescope.

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“…Si 3 N 4 is cleaned with a KOH solution prior to deposition. This cleaning procedure and base pressure are crucial for the reproducibility and high quality of Mo, while bias voltage during sputtering controls the film stress, ultimately determining its T c and residual resistance ratio 11 . After Mo deposition, the pressure is changed to 6μbar and a 15nm-thick Au film is deposited in-situ by DC magnetron sputtering; typical deposition rates are respectively 0.2nm/s and 0.5nm/s for Mo and Au.…”

Section: Tes Fabricationmentioning

confidence: 99%

“…In previous work we demonstrated our ability to fabricate high quality, reproducible Mo thin films and Mo-based TES 10,11,12,13 . Now we have devised a development plan aimed at fabricating TES meeting X-IFU requirements.…”

Section: Introductionmentioning

confidence: 99%

Towards Mo/Au based TES detectors for Athena/X-IFU

et al. 2014

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The X-ray spectroscopy telescope Athena has been designed to implement the science theme "the hot and energetic universe", selected by the European Space Agency as the second large mission of its Cosmic Vision program. X-IFU, one of the two interchangeable focal plane instruments of Athena, is a high resolution X-ray spectrometer made of a large array of Transition Edge Sensors. Two options are under consideration for the X-IFU microcalorimeters: Ti/Au bilayers or Mo/Au bilayers. Here we report on our efforts to develop Mo/Au-based TES. The TES are made of high quality superconducting Mo/Au bilayers fabricated at room temperature on low stress Si 3 N 4 membranes; Mo is deposited by RF magnetron sputtering and in-situ covered by a thin (15nm) Au layer deposited by DC sputtering; in a second step, the Au layer thickness is increased ex-situ by e-beam deposition, to obtain suitable resistance R n and operation temperature values. Very sharp transitions (~few mK transition width) are obtained, with typically R n~2 5mΩ and T c~ 100-120mK for 65/215 bilayers. First simple TES designs are being tested. Also, Bi films several μm thick, intended to constitute the X-ray absorber, are fabricated by electrochemical deposition.

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Effects of Stress and Morphology on the Resistivity and Critical Temperature of Room-Temperature-Sputtered Mo Thin Films

Cited by 27 publications

References 34 publications

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

Fabrication of Superconducting Mo/Cu Bilayers Using Ion-Beam-Assisted e-Beam Evaporation

Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

Towards Mo/Au based TES detectors for Athena/X-IFU

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