Manufacturing of nano-engineered III-N semiconductors: Equipment Business Case

Tools for defining nanoscale device geometry are widely used in CMOS manufacturing but the economies of scale of Si VLSI do not apply to most other semiconductor industries. Conventional photolithographic techniques are limited by the size of the smallest features that they can pattern so that achieving even smaller features typically requires using the expensive and slow technique of Electron Beam Lithography. As a result only very small regions can be patterned at the highest resolution.

Cost-effective wafer-scale solutions for nanoscale devices do exist but are less widely available. They include Nanoimprint Lithography (NIL), Self-Assembly Lithography (SAL), or more recently Displacement Talbot Lithography (DTL). NIL can achieve sub-10nm features but is very sensitive to particle defects, SAL is cheap but is restricted to limited patterns and domain sizes, and DTL is a new and potentially disruptive technology for applications in the 150-1000 nm range (No DTL systems exist in the UK). The aim of this grant is to bring the two techniques of NIL and DTL more into the mainstream by demonstrating their capability for up-scaling from small area nanopatterned materials or devices into full wafers. The NIL and DTL equipment will allow us to determine the most suitable technique (since either one will not satisfy the requirements for all applications) and related nanofabrication processes creating nano-scale patterns (10-1000 nm) in a range of materials for a variety of applications.

The ability to nanopattern at the wafer scale is essential for commercial production of emerging device types and for research applications where large-area uniformity is necessary for subsequent processing steps. An example of the latter is crystal growth on nanopatterned substrates since large area patterns are essential to achieve good uniformity of growth in the growth reactor.

The ultimate goal behind establishing these nanolithography techniques is to develop advanced fabrication processes for the UK's 21st Century manufacturing industries, and in particular the manufacturing of III-Nitride semiconductor materials. The III-Nitrides are functional materials that underpin the emerging global solid state lighting and power electronics industries. But their properties enable far wider applications: solar energy conversion by photovoltaic effect and water splitting, water purification, sensing by photonic and piezoelectric effects and in non-linear optics. Many applications of these functions of the III-Nitrides are enhanced, even enabled by creating three dimensional (3D) nanostructures. However the exploitation of these properties can only be achieved if there are production-worthy processes available. Hence the purpose of this proposal.

This proposal is about providing access to wafer-scale nanolithography equipment to a collaboration of internationally leading researchers in the field of III-Nitride semiconductor materials. The III-Nitrides are materials that underpin the emerging global solid state lighting and power electronics industries. Nanostructuring these materials have the potential to enhance their properties and this will be the driving force behind developing the nanolithography capability. These researchers will then make the techniques available to other materials systems and applications as described in the linked research proposal.

Knowledge will be advanced through exploring the capability of DTL for sub-micron patterning and establishing the limits to the technique and how it compares to NIL. The linked research project will involve optical modelling of the DTL process to understand the variety of patterns that can be created.

The capability of large volume manufacturing of nanostructures will accelerate the scientific understanding of the role that they can play in increasing the quality of semiconductor crystals by reducing their defect density and in enabling future device architectures. The importance of this area of research is exemplified by the US administration's recent announcement of $200 million for the foundation of an 'Integrated Photonics Manufacturing Institute'.

The equipment will allow existing proof-of-principle devices that are created by EBL to be up-scaled to pilot production either within the university or commercial sectors. With successful IP protection this could lead to further research contracts in the short term (2-5 years from project start), the creation of a new spin-out company or a new product line within an existing business in the medium term. The wafer-scale processes that will be developed will have economic impact in reducing the costs involved in manufacturing processes.

In particular the programme of research will have direct impact on the industrial partners connected with the proposal. A number of the Research Projects identified in the linked research proposal that will be used to inform and validate the generic manufacturing processes have been inspired through these industrial connections. The work will also impact a wider range of semiconductor companies, including support industries such as the manufacturers of process equipment.

The UK-based expertise and capability will allow new ideas to be brought to market more quickly and cost-savings to be made in the manufacturing process leading to increased competitiveness of the UK semiconductor industry.

Highly-skilled personnel will be trained for future industrial roles on the advanced nanolithography equipment. For University of Bath researchers the training will be delivered via its availability in the cleanroom and external users via the Nanolithography Access scheme. New PhD students in the Condensed Matter CDT will be trained via a 4 day intensive training course covering all the equipment based in the David Bullet Nanofabrication Cleanroom.

Secondary training will be delivered to further researchers through inter- and intra-university seminars enabled by the networks to which the PIs and CIs belong. For example, the UK Nitrides Consortium, the management committee of which the PI serves, exists to allow for formal and informal interactions and the exchange of personnel. In addition, the Open Workshop will educate attendees on the capability of the systems purchased.

There will be long term impact on society through 1) enabling new types of integrated, multifunctional sensors for lab-on-a-chip medical diagnostics and gas sensing, 2) improving the energy efficiency of light emitters to accelerate the shift towards solid state lighting, and 3) developing a UK based semiconductor manufacturing industry that is world leading.