Atom Fabrication Laboratories
The Atom Fabrication Laboratories provide a globally unique set of facilities for the development of atomically precise devices in silicon. Ten state-of-the-art scanning tunneling microscopes (STM), including three low temperature scanning tunneling microscope (LT-STM) and several variable temperature scanning tunneling microscopes (VT-STM) from ScientaOmicron Nanotechnology GmbH and Unisoku Ltd are hosted at UNSW. Each of these systems offers the combination of high-quality silicon growth and high resolution STM imaging and lithography capabilities.
Work on understanding surface atom exchange chemistry is performed on the VT-STMs, which consist of a custom-configured, triple-chamber UHV STM/MBE systems. These STMs can be operated at temperatures ranging from 8K to 1100K and are used to perform atom-scale lithography. A second UHV chamber houses silicon sources for the MBE growth of epitaxial silicon with thicknesses up to hundreds of nanometers.
The multi-chamber STM-SEM/MBE system was our first system to undertake qubit fabrication development and provides the necessary registration and high-purity silicon growth capabilities required for multi-qubit fabrication. Specifically, the MBE system is capable of device quality Si and SiGe growth of wafers up to 4” diameter, with low background doping levels.
A low temperature oxide chamber is available for the development of high-quality silicon dioxide barrier layers, using a resistive silicon sublimation (SUSI) and an RF plasma neutral atomic oxygen source. Operating under UHV conditions, the STM-SEM and MBE chambers are physically connected even though they are housed in different, acoustically shielded laboratories within the Atom Fabrication Laboratories.
Also housed in the Atom Fabrication laboratories is an Omicron Nanoprobe four probe STM system that is configured for in-situ electrical characterisation of nano- and atomic-scale devices, and a combined VT/LT-STM system that allows low temperature imaging of donor wavefunctions. All STM systems are equipped with a Nanonis STM-controller from SPECS Zurich that allows for surface imaging, atomic precise hydrogen lithography and low temperature state-of-the-art spectroscopy allowing the determination of the level spectrum of a sub-surface dopant or multi-dopant arrangement.
A three-floor atom-scale manufacturing foundry exists adjacent to the Centre laboratories for Silicon Quantum Computing (SQC). This facility hosts dedicated STMs, fridges, and a customised fast processing facility dedicated to quantum processor prototype development. This includes a next-generation VT/LT-STM system and a Unisoku Ltd LT STM, which allows STM imaging and spin selectiviev electron spectroscopy at temperatures down to 300mK and in magnetic fields up to 9T. More recently, a number of STMs have been retro-fitted with isotopically pure 28Si sources to produce qubit desires that benefit from the long coherence times found in this material. Accurate growth temperature and surface quality can be monitored in-situ with a laser absorption/reflection-based BandiT temperature measure system.
Cryogenic Measurement Laboratories
The Centre hosts a series of Cryogenic Measurement Laboratories, across both the Newton and Old Main Buildings with Centre researchers having access to multiple dilution fridges. These laboratories form an impressive set of experimental facilities for characterisation and measurements of quantum processors for the silicon projects at UNSW.
The laboratories house a collection of dry and wet dilution refrigerators from various vendors (Oxford Instruments, Leiden Cryogenics and BlueFors) allowing quantum electronic measurements at temperatures down to 7mK and in magnetic fields up to 7 T. Typical qubit experiments require measuring voltage signals in the pV range, from DC to 50GHz microwave frequencies, using fast pulsing, arbitrary waveforms, and laser light sources, and all of which are installed and readily available.
Real-time data acquisition and fast feedback techniques are available, and pulsed local electron spin resonance experiments are routinely conducted. All set-ups have ultra-low noise and high bandwidth current amplifiers, allowing detection of currents in the pA range with < 10 microseconds time resolution, or fA at low frequency. Optical access is available for some dilution fridges, and this led to the first observation of resonant photo-ionisation of a dopant atom by single shot charge sensing with 50 neV resolution.
The solid-state qubit measurements in the Centre are fully supported by a Helium liquefier plant. This $2M investment from the UNSW Faculty of Science allows measurements to run uninterrupted, thereby reducing reliance on the commercial supply of liquid helium, which fully relies on imports.
The laboratories are supported by professional staff with extensive experience in cryogenics and RF measurement systems. This laboratory is operated with a UPS supported power supply, a helium gas recovery network, and a large cooling water capacity for its dry dilution refrigerators, and additional security and safety measures.
Fast Processing Laboratory
The Fast-Processing Lab of SQC is a dedicated clean room for silicon processing. Spanning an area of just under 200m2, it contains new, flexible, and high resolution electron beam lithography tools as well as a full-scale silicon front-end processing line to enable rapid processing and deliver a fast turn-around time for qubit fabrication.
CQC2T researchers were instrumental in establishing open access cleanroom facilities at UNSW, which have combined with the NSW Node of the Australian National Fabrication Facility (ANFF-NSW) to provide an extensive facility offering advanced nanofabrication capability across four distinct laboratory areas. ANFF-NSW infrastructure and operations are managed by the ANFF-NSW team, headed by Prof Professor François Ladouceur (ANFF-NSW Director) and Dr Matt Boreland (ANFF-NSW Facility Business Manager).
In 2019, the ANFF-NSW labs were extensively refurbished via a $4.8M UNSW funded project. The project included space restructuring to accommodate $4.5M of new process tools under the Research Infrastructure Investment Plan (RIIP) supported by co-funding from the Federal Government (NCRIS), State Government (RAAP) and UNSW. Several new tools such as oxidation furnaces, ion etching tools, and electron beam lithography tools have been delivered and installed on that investment stream.
The ANFF-NSW Lower East Advanced Lithography laboratories comprise 50m2 of ISO5 and 30m2 of ISO7 cleanroom space. The focus in this area is nano-electronic device production, with key equipment including two FEI/NPGS electron beam lithography systems (one dedicated to Centre projects) that are regularly used to produce sub-20 nanometer device features. Other tools in this area support wet chemical processing, photolithography, metal deposition, metrology, and wafer dicing.
The ANFF-NSW Upper East laboratories offer a further 50m2 of ISO5 and 90m2 of ISO7 cleanroom space. A 60m2 ISO5 cleanroom was created within the South laboratories during the 2019 lab restructuring. This area contains high-temperature furnaces to support core Si MOS processes, specifically diffusion (p-type and n-type), oxidation (both thick and extremely high-quality thin layers), and annealing. In addition, the ISO5 zone has supporting capabilities for wet chemical processing. The ISO7 zone contains a suite of chemical vapour deposition (CVD) tools including plasma-enhance PECVD and newly commissioned low-pressure LPCVD for depositing thin films of Si, SiOx, SiNx and related materials.
The ANFF-NSW West Advanced Lithography, PVD and Plasma-Etching laboratories comprise 80m2 of ISO5 and 110m2 of ISO6 cleanroom space. The ISO5 zone contains four fume cupboards for wet chemical processing as well as photolithography, a newly installed atomic layer deposition, annealing and metrology tools. A dedicated room within the ISO5 zone houses a Raith 150TWO electron beam lithography system capable of stitch-free high-resolution patterning over large device areas.
The ISO6 zone contains e-beam evaporators, a multi-target sputtering system, plasma etching tools, a deep reactive ion etching system, and a suite of in-process metrology, including a newly installed digital microscopy system.
The ANFF-NSW south laboratories, covering 160m2, were opened mid-2014 and house a Veeco molecular beam epitaxy (MBE) system for the growth of a range of III-V materials and a Pascal dual chamber laser-MBE system producing a range of complex ceramic materials. The new Metrology and Packaging laboratory houses wire-bonders, probe stations, wafer scribers, pick-and-place tools and a parylene encapsulation tool.