Tyndall National Institute is Ireland’s largest ICT research institute (>460 researchers) with research priorities in the areas of Micro/Nanoelectronics and Photonics. Tyndall activities enable major Deep Tech innovation in Digital and Production Key Enabling Technologies (KETs).

Tyndall has extensive fabrication facilities in nanoelectronics, compound semiconductors and MEMS, which are fully supported by wide-ranging test, characterization and packaging facilities at a single site. In 2010 and 2018, the Irish Government invested in the development of the Tyndall ‘FlexiFab’ to complement the existing silicon and semiconductor fabrication facilities. FlexiFab provides a unique set of flexible fabrication facilities and is based on the principles of ‘More than Moore’ wafer processing with ‘Beyond CMOS’ concepts with an emphasis on interdisciplinarity and technological convergence.

Tyndall is a single-site research institute enabling extensive interfacing between the FlexiFab and other activities across the value chain in device theory, modelling, materials growth and systems integration. Tyndall’s key infrastructure includes:

  • Design, Modelling & Simulation
  • Semiconductor Material Growth
  • Device Fabrication (Silicon and III-V)
  • Test & Characterisation
  • Photonic & Electronic Packaging

Uniquely Tyndall has an ecosystem of expertise, capabilities and infrastructure to drive research and innovation in a range of key areas of nanoelectronics to achieve quantum advantage and functional diversity, from Nano-scale Platforms for Quantum Technologies and Disruptive Devices to their Advanced Integration with CMOS. This impact is significantly increased by the larger transnational ecosystem offered by ASCENT+. Through ASCENT+ Tyndall provides access to Key Enabling Capabilities in Nano for QuTech, Disruptive Devices and Advanced Integration, as described below.

Nano for Quantum Technologies

Tyndall has uniquely developed site-controlled III-V quantum dots for quantum light emission, e.g. single photons, and has demonstrated the only site-controlled quantum dot system capable of high fidelity entangled light emission. This is a very promising scalable platform for solid-state quantum computation and communication. Amongst the particles investigated to date for quantum information technologies, photons are the least prone to decoherence, due to weak interaction with their environment. Photons can provide close to ideal performance, with photon loss or absorption being the only relevant sources of decoherence.

The Tyndall nanostructures represent a deterministic source of on-demand non-classical light, a fundamental pre-requisite for any optical quantum information protocol. This property is not shared by conventionally exploited sources of quantum light, which rely on probabilistic down conversion events such as heralded spontaneous parametric down-conversion (HSPDC), the gold standard for non-classical radiation sources to date. Quite remarkably, sources based on QDs do not have any fundamental physical limitation in their potential to deliver quantum signals deterministically and on-demand. This technology allows for not only producing arrays of single/entangled light emitters but also the unique possibility of extracting single dot structures for successive transfer printing, e.g., on integrated structures.

Tyndall offers access to:

Processing
  • Site-controlled single/multiple quantum dots and devices
  • Re-growth GaAs processing
  • Epitaxial growth of AlGaAs- and GaAs-based structures
  • Post-growth processing for device fabrication
  • Single-dot optical emission
  • Preparation for transfer printing of structures
Modelling of quantum nanostructures
Based on group IV, group-III and group-V materials and their alloys. To assist in the evaluation/control of interactions between spins, photons and phonons. Tyndall has experience calculating the effects of intrinsic defects in group IV semiconductor nanostrucures on the band structure, oscillatorstrengths, spin and transport properties. These are currently being studied for single photon sources for quantum cryptography.
Metrology/Characterisation
  • Dry cryogenic time-resolved microPL and cryogenic workstation with optical access
  • Correlation spectroscopy and quantum tomography of polarization states
  • Optical quasi-resonant and resonant excitation of nanostructures (650-950nm)
Devices/Test Structures
Site-controlled single and entangled photon emitters in the near infrared and matched to atomic vapour quantum memories

Disruptive Devices

Processing
Tyndall’s Central Fabrication Facilities consists of three distinct cleanroom spaces, 250m2 of class 1,000 and class 10 for flexible silicon fabrication, 750m2 of class 10,000 and class 100 for MEMS and compound semiconductor fabrication, and 40 m2 of class 1000 for e-beam lithography.

Tyndall offers processing access to:

  • Tunnelling devices, sensors & NEMS.
  • Tyndall has the processing protocols and flexibility to take advanced materials from users and integrate them into working electronic devices. For example functional materials are often grown by Molecular Beam Epitaxy (MBE) or Atomic Layer Deposition (ALD), but in order to demonstrate functionality at the device level, say for memory, sensing, or steep-slope switch applications, further processing can be provided such as photolithography, etch, doping, and contacting.
  • Advanced Patterning: E-beam lithography is available for top-down nanowire patterning on Si or non-Si substrates. Nanowire test structures can be patterned according to user-defined designs, but typically are fabricated with a range of widths for proper electrical and process characterisation. Process development and characterisation for nanowire-FETs, FinFETs, and MuGFETS (multi-gate FETs) must be carried out on structures appropriate for the technology. Sub-10 nm wide wires can be fabricated to provide test structures for nanowire process development analysis, as well as for electrical characterisation of structures with fine features.
  • Metal customisation: Metal contact tracks enabled using the electron beam or FIB (Focused ion beam) milling – allows customization of nanowire structures at dimensions of 10nm and lower (potentially 2.5nm)
  • 2D contacting: Technologies for 2D contacting to nanoscale structures and e-beam contacting on flakes. Specifically to address the vast choice of 2D materials it is critical to electrically evaluate selected material options. E-beam contacting can be performed on material flakes at Tyndall (graphene, transition metal dichalcogenides etc.). Electrical characterization can be undertaken for resistance measurements, or if required demonstrator FET devices can be fabricated by this method of e-beam lithography and contacting.
Modelling
Tyndall has extensive and unique experience in the atomistic calculation of the physical parameters that determine optical, electronic transport and thermoelectric properties of materials for novel devices. Modelling/Data Sets include the electronic and vibrational states, band offsets, electron-phonon coupling, deformation potentials, alloy and impurity scattering, optical matrix elements and oscillator strengths. The expertise at Tyndall ranges from the determination of these properties in bulk materials to assessing how they change due to alloying, nanostructuring and when in contact with novel materials as used in disruptive devives. Examples include the electronic thermoelectric properties of group IV alloys and nanostructures, such as SiGe and Si nanowires; optical and transport properties and band offsets in group IV – III-V heterostructures, such as Ge/InGaAs and related alloys, and electronic and vibrational dynamics in semiconductors, metals and semimetals. Our atomistic approach has the added advantage of allowing access to both quantum and classical properties, and have led to improved materials for nanoelectronic, ultrascaled, quantum and optical devices.

Tyndall provides modelling access to the determination from first-principles of:

  • Effects of strain, doping and alloying on the electronic and thermoelectric of group IV materials, including electronphonon, impurity and alloy scattering.
  • Band offsets between group IV, group-III and group-V materials, and their dependence on strain and anion/cation interface termination.
  • Deformation potentials as a function of strain and alloy composition for group-IV compounds and Si nanowires.
  • Optical matrix elements between electronic bands in group-IV and group III-V alloys, and superlattices. This includes optical coupling between indirect bands via electron-phonon, impurity and alloy scattering
  • Electron and phonon non-equilibrium dynamics, for instance after photoexcitation, in Ge and Bi
  • Effects of alloying and strain on phonon band structures.
Metrology/Characterisation
Tyndall has extensive expertise in Metrology/Characterisation for the development of Disruptive Devices, in particular in defects metrology at the dielectric/semiconductor interface of various materials systems; including Si, Ge, III-V, Transition Metal Dichalcogenides (TMDs) and SiC for different applications.

Tyndall offers electrical and physical characterisation access

  • Multi-frequency impedance measurements taken at a range of temperatures (77K-450K)
  • Physical characterisation using a variety of techniques
    • Nanovisualisation with AFM, DBFIB
    • High Resolution TEM, SEM and FIB, EDAX capability
    • Raman & Optical Spectroscopy
    • Fluorescence microscopy
    • Scanning Acoustic microscope)

This enables the fabrication of fully-functional metal/high-k/III-V gate stack technologies for MOSFET applications in nano-electronics. With the utilisation of additional expertise in the MOVPE of III-V materials, surface passivation of interface defects at high-k/III-V interfaces can be applied to achieve very significant reductions in the interface defect densities so that inversion behaviour can be observed in the high-k/III-V region for both n-MOS and p-MOS high-k devices. To discriminate between interface states and border traps located in the dielectric, a novel methodology combining experimental capacitance and conductance voltage measurements with physics based TCAD simulations is applied. These protocols have been successfully transferred to and demonstrated in the fabrication of full III-V, TMD and SiC MOSFETs. Further work is currently under way to extend this knowledge to the formation and characterisation of semiconductor materials and device architectures at low temperatures (<500°C) which would allow incorporating memory and logic functions into the traditionally passive back end of line of silicon integrated circuits.

Tyndall offers nanoferroics characterisation access to its expertise and equipment for the characterisation of magnetoelectric multiferroic materials. In these materials the ferroelectric and ferromagnetic polarisations are coupled such that switching one switches the other, making them most promising architectures for memory scaling beyond current technologies. The unique advantage of these advanced materials is that not only could they find application in high storage density, low-power memory devices that can be electrically written and magnetically read, but also by constructing devices that exploit the presence of both ferroelectric and ferromagnetic states, memory technologies with 4-state logic could be achieved. Characterisation is performed with state-of-the-art Asylum Research MFP-3D Atomic Force Microscope with high voltage piezoresponse force microscopy (PFM), variable magnetic field (VFM) and high voltage PFM imaging under variable magnetic fields (VFM2-HV) capabilities. The MFP-3D Asylum Research AFM is equipped with a high voltage amplifier (up to ±220V) and a DART (Dual AC Resonance Tracking) PFM mode designed to boost the piezo signal and minimise topographical ‘cross-talk’, enabling measurements of even the weakest piezoelectric materials. The ability of the PFM lithography mode to ‘write’ and pattern ferroelectric domain structures allows demonstration that polarisation information can be stored in films and recovered for potential memory/data storage applications.

The VFM2-HV Variable Field Module works in conjunction with the MFP-3D Asylum Research AFM addressing technical needs of

  1. Magnetic force microscopy (MFM) imaging under a high, variable magnetic field
  2. Simultaneous MFM and PFM under high tip-sample voltage bias and high, variable magnetic field.

During MFM imaging, long-range, out-of-plane magnetic forces between ferromagnetic samples and an AFM coated with a ferromagnetic material are detected. The VFM2-HV can apply static magnetic fields up to ±2000 Oe, parallel to the sample plane, therefore is an ideal option for researchers who want to investigate nano-scale magnetic effects on application of high magnetic fields while performing spatially resolved atomic force microscopy experiments.

Advanced Integration

Processing
The Tyndall Flexifab allows the integration of new materials, device and subsystem concepts, from the nano- to the meso-scale, thereby, enabling research across nanoelectronics, nanophotonics and nanobiotechnology. In particular, integrating photonics with nanoelectronics can achieve the functionality of heterogeneous multi-chip integrations solutions but with the performance, complexity and scalability of ‘systems on a chip’. There are a number of developed processes that are proven to produce state-of-the-art results to be used in the monolithic integration of nanophotonics and optical sensors with advanced CMOS.

Tyndall offers processing access to range of etching systems for nanostructuring of silicon, silicon nitride, gallium arsenide and others. For the CMOS-compatible materials, there is the option to combine them with the processes of 100mm CMOS line, to realise, for example, photonic nanodevices with electro-optic tuning or current injection. As the 100mm wafer scale makes such processing relatively easy to access and cost effective to use, in comparison to 200mm and 300mm facilities, this makes the Tyndall nanostructuring capability quite attractive.

Tyndall offers access to chemical functionalisation processes and expertise to enable the integration of novel materials into devices. As devices are progressively getting smaller, the materials comprising these devices are approaching a point where the surface atoms start to dominate behaviour. In order to reduce variability in material performance it is imperative to introduce a surface passivation layer. Tyndall can provide considerable expertise in carrying out chemical functionalisation of bulk and nanostructured materials for the formation of self-assembled monolayers at the air:surface interface. The chemical modification can be used not only to passivate the surface but also to change wetting properties or to introduce new functionality. This expertise covers a very broad range of materials from semiconductors (e.g. silicon and germanium) to 2D materials (e.g. graphene and TMDs) and metals (e.g. gold and silver) or oxides (e.g. titanium and silicon dioxide). 2D materials are or particular importance as they are almost entirely comprised of surface atoms. If the surface remains untreated, oxidation and adsorption of adventitious material will have a detrimental impact on their electrical properties. In order to reduce performance variability it is necessary to
passivate their basal planes. Methods such as spin coating resists and polymers have been used however Tyndall offers a method which is more easily controlled and less likely to cause damage to the underlying material. Self-assembled monolayers of hetero-atom alkanes (e.g. thiols or amines) can be used to form non-covalently stabilising layers.

Modelling
As heating effects have become increasingly important for highly-packed devices, Tyndall has developed a unique suite of computational tools to accurately describe electronic and thermal transport properties of bulk semiconducting materials, with a particular emphasis on topological V2-VI3 and IV-VI materials. These simulation tools require as an input only the material’s chemical composition and can be used to predict electronic and thermal conductivity of novel bulk materials with no empirical parameters. This accelerates the discovery of materials with tailored electro-thermal properties for heat dissipation. Further work is currently under way to extend these codes to enable predictions of electro-thermal properties of complex nanostructured materials and alloys, which will include the contribution of topological states in the case of V2-VI3 and IV-VI materials.

Tyndall offers modelling access to these simulation tools for the ASCENT+ users. Tyndall has also access to numerical modelling software for advancing the integration of photonic technologies, namely the LUMERICAL suite and Photodesign FIMMWAVE/FIMMPROP, along with a large number of well-trained staff who can support ASCENT+ users.

Tyndall’s FlexiFab