ICP-Ätzanlage
Final Report Abstract
The usage of the ICP plasma etcher was directly linked to the research of the former DFG-Center for Functional Nanostructures (CFN) funded by the DFG from 2001 to 2014. The researchers at the interdisciplinary research center worked together in five research areas: Nano-Photonics (Area A), Nano-Electronics (Area B), Molecular Nanostructures (Area C), Nano-Biology (Area D) and Nano-Energy (Area E). With the end of CFN funding new research projects came into focus: the investigation of integrated nanophotonic circuits, and hybrid nanophotonic devices, and to the field of superconducting Josephson devices. In detail, the plasma etcher (ICP) was essential to perform following projects: Nanophotonic Devices. The ICP was used for dry etching of photonic components in silicon and silicon nitride. The focus was on the fabrication of low-loss photonic waveguides, grating couplers, polarization beam splitters and ring resonators. To this end, the ICP was mainly used to transfer soft polymer masks created by electron beam lithography into thermally grown SiO2, which acts as a hard mask for further dry or wet chemical etching processes. Quantum Nanophotonics. The project is concerned with realizing nanophotonic integrated circuits for applications in on-chip information processing and sensing. Waveguide base-devices are developed to exploit near-field coupling for on-chip control of the properties of propagating modes. These devices are fabricated with electron-beam lithography and reactive ion etching to realize sub-wavelength photonic components. Nanophotonic cavities and interferometers are used to enhance light-matter interactions in a chipscale framework. This allows for realizing compact systems for the integration with nanoscale devices. Interdigitized transducers to manipulate the quantum state of two-level defects by ultrasonic waves. In a series of experiments it was recently shown that two-level defects, which are abundant in Josephson junctions and presently the biggest obstacles for superconducting circuits to be employed as quantum bits, are sensitive to external strain fields. In a next step we will apply ultrasonic waves in the GHz range to manipulate the quantum state of these two-level defects in order to gain more insight into their microscopic nature. For these experiments, surface acoustic waves (SAW) will be used on the chip with the superconducting circuitry. The generation of SAW at GHz frequencies requires interdigitized transducers with finger widths in the range of μm. Reactive-ion etching was employed to etch the finger-like capacitor structures. This technology proved to be superior to the conventional lift-off technique to reliably produce structures with 1μm widths. Microwave circuits for coherent manipulation of superconducting Qubits. Superconducting Qubit circuits based on Josephson junctions are a promising candidate for a scalable quantum computer. One of the key figure of merit is the quantum coherence of the individual Qubit and therefore the high quality electromagnetic environment, especially in the microwave regime. Multi-gas and high etching rate is here a mandatory requirement for the quality of microwave circuits, since it allows for an optimal material selection and purity. Several samples have been successfully prepared and measured employing the ICP as a key fabrication tool. Development of superconducting nano-wires for quantum-phase slip dynamics. The quantum phase slip phenomena in superconducting nano-wire junctions is dual to the Cooper pair tunneling phenomena in Josephson junction. The nano-wires fabricated with the ICP Plasmalab are required to be only a few ten nanometer wide and set therefore stringent limits to the fabrication tools. Utilizing the ICP etching tool, wires have been successfully fabricated which fulfill these requirements and have been characterized at low temperatures.
Publications
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„Smooth and ultra-precise silicon nanowires fabricated by conventional optical lithography” CLEO 2011, Baltimore (Maryland), USA, Paper CThZ1, May 2011
Palmer, R.; Alloatti, L.; Korn, D.; Moosmann, M.; Huska, K.; Lemmer, U.; Gerthsen, D.; Schimmel, Th.; Freude, W.; Koos, C. and Leuthold J.
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“Strain Tuning of Individual Atomic Tunneling Systems Detected by a Superconducting Qubit” Science 338, 232 (2012)
G.J. Grabovskij, T. Peichl, J. Lisenfeld, G. Weiss, A.V. Ustinov
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“Anisotropic Rare-Earth Spin Ensemble Strongly Coupled to a Superconducting Resonator”, Phys. Rev. Lett. 110, 157001 (2013)
S. Probst, H. Rotzinger, S. Wünsch, P. Jung, M. Jerger, M. Siegel, A. V. Ustinov and P. A. Bushev
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“Diamond integrated optomechanical circuits”, Nature Communications 4, 1690 (2013)
P. Rath, S. Khasminskaya, C. Nebel, C.Wild and W.H.P. Pernice
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“On-chip photonic memory elements employing phase change materials”, Advanced Materials 26, 1372 (2014)
C. Rios, P. Hosseini, D. Wright, H. Bhaskaran, and W.H.P. Pernice
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“Waveguide integrated electroluminescent carbon nanotubes”, Advanced Materials 26, 3465 (2014)
S. Khasminskaya, F. Pyatkov, B. S. Flavel, W.H.P. Pernice and R. Krupke
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“Multiphoton dressing of an anharmonic superconducting many-level quantum circuit”, Phys. Rev. B 91, 054523 (2015)
J. Braumüller, J. Cramer, S. Schlör, H. Rotzinger, L. Radtke, A. Lukashenko, P. Yang, S. T. Skacel, S. Probst, M. Marthaler, L. Guo, A. V. Ustinov, and M. Weides
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“One-dimensional Josephson junction arrays: Lifting the Coulomb blockade by depinning”, Phys. Rev. B 92, 045435 (2015)
N. Vogt, R. Schäfer, H. Rotzinger, W. Cui, A. Fiebig, A. Shnirman, and A. V. Ustinov
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„Probing the density of states of two-level tunneling systems in silicon oxide films using superconducting lumped element resonators”, Appl. Phys. Lett. 106, 022603 (2015)
S. T. Skacel, Ch. Kaiser, S. Wuensch, H. Rotzinger, A. Lukashenko, M. Jerger, G. Weiss, M. Siegel, and A. V. Ustinov
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“Cavity-enhanced light emission from electrically driven carbon nanotubes”, Nature Photonics 10, 420 (2016)
F. Pyatkov, V. Fütterling, S. Khasminskaya, B. S. Flavel, F. Hennrich, M. M. Kappes, R. Krupke, and W.H.P. Pernice
