Manufacturing Quantum Nano-LEGO Blocks for Electronics, Photonics, and Phononics Integrated Systems

As the minimum feature size of the Si transistor is shrinking down, various quantum mechanical effects are observed even at room temperature operations. This includes the quantum tunnelling leakage currents and the capacitance decrease by quantum confinements. All of these effects, unfortunately, degrade the performance of transistors, and the reason is partially coming from the design principle of conventional transistors based on classical mechanics. New paradigm shift is expected to achieve the transition from classical to quantum technologies for innovations in high performance computing, secure communication, simulation, sensor, and metrology.

However, many manufacturing challenges must be overcome to integrate quantum structures for real industrial applications, since quantum states are extremely sensitive to environmental disturbances. We must minimize the line-edge-roughness, thickness-non-uniformities, random dopant fluctuations, and interfacial defects.

In this fellowship, a novel manufacturing process technology will be developed to fabricate various quantum structures, named Nano-LEGO Blocks, including quantum wells, nano-wires, quantum dots, pillars, and fins. These nano-structural building blocks will be fabricated by a combination of the state-of-the-art Si nanofabrication processes and the self-limiting wet etching. The nano-structures are defined by the crystallographic orientation with the atomically flat interface, and the quantum nature of the structures will be examined.

By properly designing the process steps and the 3D device layouts, we can economically assemble these building blocks in large quantities with wafer scale in highly reliable, low-cost, and high-yield processes. We are also planning to introduce the manipulation probes in the chamber of our He-Ion-Microscope to manipulate the building blocks to construct the 3D structures by using the electrostatic force. The concept is based on the natural extension of LEGO Blocks to the nano-meter scale, i.e., starting from the several kinds of well-defined building blocks we can construct sophisticated technological arts by the arbitrary combinations of the blocks.

As applications of this manufacturing technology, we will fabricate 3 devices:

(1) Si/Ge Based Single Photon Source,
(2) Si Single-Electron-Pump for quantum-metrology,
(3) Si on-chip heat sink for energy harvesting.

While our main purpose is to establish the comprehensive process technologies using nano-structural building blocks, we will find out real process issues and solutions in the actual device fabrications for identifying true industrial needs. The combinations of these building blocks will enable realization of new functionalities using the quantum nature of properties for various electronics, photonics, and phononics integrated system applications. The applications are not limited to quantum devices, and we will demonstrate on-chip heat sinks and low-loss Si photonic waveguide, which can immediately contribute to the energy saving in a big data centre for cloud computing.

The expected impacts of this research is summarized as follows:
1) Achieving grand challenge of systematic nano-scale designs by self-limiting process of atomically flat Si, which is fully compatible with the current Si process.
2) Novel manufacturing technologies will be established by constructing complex 3D nano-structures by the combination of top-down fabrication and bottom-up assembly.
3) Manufacturing capabilities will be significantly advanced for sever targets of quantum circuitries.
4) Various device applications opportunities will be open-up by controlling the nanostructures in the atomic level, which will be technologically important for quantum devices.
5) Applications are not limited to quantum devices. The process will also be useful for the on-chip heat sinks and low-loss Si photonic waveguide, which can immediately contribute to reduce the power consumptions in a data centre.

Business domain of quantum technologies is different from that of the conventional ICT technologies. For example, the secure quantum communication enables to protect laws of society by law of physics. The potential economic impact of the absolute safety should be comparable to the existing loss in criminals, which is worth for several times larger than the security market supported by software. This fellowship focuses on the manufacturing technologies of the hardware based on the refined process recipes. It will start as a niche market for the finance and the defence activities, where UK is strong and internationally competitive, and eventually it will grow for the consumer market.

The state-of-the-art Si technologies are located in the transition regime between classical and quantum regimes, and this fellowship project is aiming to be prepared for manufacturing capabilities of quantum devices in highly developed countries like UK. This will only be accomplished by manufacturing expensive products like quantum secure networks and quantum computers. Therefore, the manufacturing processes of quantum technologies will create jobs in UK, because of the higher values of quantum devices over the conventional consumer products.

In this way, we would like to fill in the technological gap between "Manufacturing the Future" and "Quantum Technology", which will meet with the EPSRC research portfolio.

The developed manufacturing processes will also contribute to the existing businesses like chip cooling in data centres, and other electronic and photonic integrated systems including Si photonics with a low loss waveguide, which will be immediately transferred to the industries.