High-specification nanofabrication equipment: enabling increased capability and capacity for electronics, spintronics, photonics, and bioelectronics.

In March 2021, the University of Leeds took ownership of its £96M Sir William Henry Bragg Building, which will bring the Schools of Physics & Astronomy, and Computing, into the North East quarter of the University, next to the Schools of Chemistry, Electronic & Electrical Engineering, Mechanical Engineering, Civil Engineering, and Chemical & Process Engineering. In parallel, the University has established the Bragg Centre for Materials Research, which brings together more than 200 materials researchers from across campus to foster a vibrant and creative community of scientists and engineers to inspire and facilitate ground-breaking and interdisciplinary research to meet global challenges.

At the heart of the Bragg community is the Leeds Nanotechnology Cleanroom, which was established in 2002, and over the last twenty years has significantly expanded its activities to support a breadth of research across the University, including spintronic, opto-electronic and bioelectronic materials and devices. It is now also used extensively by external industry and academia, and has led to the training of over 200 researchers over the last decade.

The Cleanroom is currently moving into new, larger, and significantly enhanced accommodation in the Sir William Henry Bragg Building. This will triple the maximum number of daily Cleanroom users, and provide a significant enhancement in the environment and capabilities for device processing (e.g. enabling gas chemistries hitherto not possible). The 730 m2 new facility is future-proofed (with a further 99 m2 fallow space for expansion) and constructed to the highest levels of specification, including bays at ISO 4 (class 10) specification and temperature stability of 0.1 degC/hr. There are also eight class 10 lamina wet benches, and 31 quiet islands for vibration-sensitive equipment. This is accompanied by 20 specialist gas cabinets for flammable, corrosive and inert gases with associated gas pipes and valve manifold boxes, as well as point of use, vent and catastrophic abatement systems, accompanied by a gas detector network for specialist gases and O2 depletion.

Current equipment includes: direct-write and mask-based photolithography; electron-beam lithography; thermal and electron-beam evaporation, sputtering and atomic layer deposition; ion beam etching; wafer and die bonding, lapping and dicing; rapid thermal annealing; electron and atomic force microscopy, and ellipsometry; and, test and packaging. All can be used for piece parts (e.g. 6 mm x 6 mm dies), with most being scalable to 4" wafers. The equipment is available to all users, and enables them to develop bespoke processes.

However, there is currently a lack of reactive-gas etching and deposition systems. This programme will address this through the provision of:

1) A silicon deep reactive ion etcher, providing high aspect ratio and through-wafer etching of silicon.

2) An open-load, parallel-plate reactive ion etcher (RIE), which will be used to realise 'teflon-like' coatings to aid demoulding during microfluidics fabrication, and for shallow dielectric etching.

3) An inductively-coupled-plasma RIE for dry-etching a wide range of materials including oxides, nitrides, polymers and refractory metals.

4) High-density, plasma-enhanced chemical vapour deposition to enable coating with dielectric cladding layers, e.g. for photonic waveguides.

These instruments will lead to the fabrication of electronic, optoelectronic and spintronics devices with significantly higher yields, and greatly improved device/materials properties. The substantial reductions in process development time will offer immediate benefit. They will also enable the patterning of materials, and realisation of device structures at Leeds that simply could not be contemplated previously, underpinning future research for the next decade and beyond across the engineering, physical, biological and medical sciences, and its translation to industry.