James Watt Nanofabrication Centre

Dr Stephen Thoms has been an integral part of Glasgow University since 1984, having joined directly from Oxford University where he earned a DPhil in Engineering entitled 'Studies in mixed species charged particle beam dynamics'.

He began his tenure as one of the early postdoctoral researchers in the Ultra Small Structures Laboratory a mere eight years after the invention of electron beam nanolithography and 6 years since the invention of e-beam liftoff in PMMA at Glasgow. The early work of which Stephen was a part laid the foundations for the future excellence of Glasgow as a world-leading centre of Nanotechnology with a focus on useful devices and open-handed collaboration: His first two papers at Glasgow demonstrated quantum confinement effects in 50nm GaAs wires at low temperature and 170nm wires defined by e-beam and transferred into indium phosphide by silicon tetrachloride etching. As the lithographic heart of an integrated team further advances of lasting value included the use of Methane Hydrogen for GaAs etching (30nm wires), the earliest GaAs/AlGaAs quantum wires confined by etching and a wide variety of early devices for electronic and optical quantum studies.  

As the leader of the high-resolution lithography effort Stephen constructed a lithography system based on a heavily modified TEM to achieve the highest resolution lithography possible. Characteristically the system supported 3” wafers and obtained the world record for a short period grating by pattern transfer into a challenging and useful material.  

In 1989, Dr Thoms was appointed as a Research Technologist, with a particular focus on electron beam lithography. During his long tenure at Glasgow, Dr Thoms has served as the lead research scientist for lithography, playing a pivotal role in its development and success.  

As the size of the effort expanded the pressure on the technology base continued to build. The volume of work and the need for accurate registration in multilevel mixed lithography led in 1990 to the purchase and commissioning of the first wide area e-beam tool in a UK university, a Leica EBPG5, a process led by Stephen. The change to the new machine from homemade tools based on homemade software was profoundly and beneficially disruptive. E-beam lithography was now a hands-off process in which outrageously skilled technical staff performed the challenging task of loading and setting up a spectacularly heterogeneous mix of samples. This was the start of the mixed research lab / facility model in use to this day. The integration of commercial software for design, exposure and modelling required the development, from scratch, of a vast array of software and procedures, training and validation systems, all done by Stephen. This was so effective that the EBPG had the largest throughput of any system in the world, despite the fact that no two samples were the same. Since the costs of the tool are fixed this emphasis on throughput and managed operation made the cost of a job very low, whilst ensuring extreme reproducibility. This underpinned the increasing interaction with commercial users, initially led by Stephen and Douglas Macintyre which led in 1997 to the incorporation of Kelvin Nanotechnologies (KNT). The availability of reliable, large area, reproducible exposure was also pivotal in the establishment of Glasgow’s leading efforts in ultra-high speed MMIC fabrication, photonic integration and nanostructures. He has continued his research into the technique, with notable contributions in the areas of mechanical pattern transfer, resists, metrology and lithographic alignment. 

Starting in 1997, an effort was made to transition all fabrication work to a single laboratory, the James Watt Nanofabrication Centre, which opened in 2005. Stephen led the lithography effort of this process, which was accompanied by the acquisition of a new field emission exposure tool, a Vistec VB6 UHR EWF housed in a custom- designed class 10 column room. The challenges and triumphs of the migration to the EBPG were replicated, now compounded by the need for continuous operation of two very different machines on two sites: Activity on the new tool only exceeded that on the EBPG in 2008.  

Only eight months later, planning commenced on the replacement for the VB6. In 2016 funding was obtained for a new tool in a top-rated proposal to EPSRC. The spending was complete in 2018 and the VB6 was turned off in 2021. 

Dr Thoms is a global expert on electron beam lithography, and his expertise has been sought after by many other academic fabrication labs and companies. Stephen is an excellent teacher, and highly prolific in training people who are now in leading positions all over the world. This reputation further solidified the JWNC's status as a leading and collaborative facility.   

Today, the JWNC conducts over 100 electron beam jobs weekly, encompassing a wide range of activities from blue-sky research and R&D to commercial ventures, including commercial access through KNT. Currently, the JWNC boasts a staff size of around 30, supporting a University research portfolio that exceeds £10 million per year. The JWNC is a key part of the Scottish super cluster of critical technologies, spanning research, design, development, and manufacturing. It stands as one of the UK’s leading facilities for converting fundamental science into components for cutting-edge devices and technologies used by some of the world’s leading tech companies.  

Dr Thoms’ retirement is well-deserved after decades of dedicated service and leadership. His presence will be greatly missed by colleagues and students alike. As Dr Thoms sorted through his belongings, he found an old publication - Miniaturisation at Glasgow [PDF] - that serves as a nostalgic throwback to the earlier days of nanoscale and semiconductor research at Glasgow. 

We wish Dr Thoms all the best in his well-earned retirement!

September 2024 

Jonathan Weaver 

Martin Weides 

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First published: 20 September 2024