In-situ Interference lithography: a new manufacturing approach for the production of nanostructured arrays

Information processing and communications enabled by advances in semiconductor technology are at the heart of the modern interconnected and application-driven world. Modern society has an enormous appetite for new platforms and services and meeting these demands places a considerable burden on device and systems development. Over the last 50 years, semiconductor manufacturing has met these demands through a scaling of device size to ever smaller dimensions. As a result, we now approach the true nanoscale regime and seek devices of size less than 10nm. The industry is however facing enormous technological and physical challenges to work at this precise scale, equivalent to only a few atomic layers. Yet with these challenges comes also enormous potential from emerging quantum device approaches which could dramatically increase in calculation capability, dramatically improve the security of data and to do this simultaneously with lower energy costs. Our well used semiconductor device production processes, based on epitaxy, patterning and etch will struggle to turn the promise of quantum technologies into manufacturable commercial devices. In contrast, we can grow naturally 'self assembled' structures with nanometer dimensions and from such materials we have extensively demonstrated quantum interactions. However self-assembly has an Achilles heel in that we cannot control the site or the dimensions because of random nucleation. As a result we cannot predict where the nanostructure is located nor its energy state. Unsurprisingly there has been very little development in terms of manufacturable devices utilising quantum technologies. What we need is an approach which combines the best aspects of patterning and self-assembly. The approach is directed (or site-controlled) self-assembly which uses lithography to define the site and then exploits self-assembly to produce the nanostructure.

Structuring with light is the manufacturing technology of the 21st century. Many products now involve cutting, milling, surface processing, sealing etc processes using laser light. Our approach seeks to exploit the capabilities of light at much smaller dimensions, specifically its capability to create regular patterns on a very small stage through the optical interference process. We will design and build a system in which laser interference interacts with semiconductor growth to create a single step in-situ manufacturing route which is free of all major limitations of conventional high cost, low throughput nanostructuring approaches. We will build and demonstrate a custom instrument in which an interference pattern from laser interference interacts with the semiconductor growth surface to nucleate self-assembled growth on a regular grid pattern. Such an arrangement is a key requirement for developing electronic and photonic circuits based on arrays of single nanostructures. The method has the further advantage of precisely controlling assembly such that the array contains identical nanostructures in terms of size, shape and electronic properties. Using this approach we will create large area state of the art quantum dot and quantum wire arrays which are essential building blocks for the semiconductor devices of the future, enabling diverse applications including electronics, photonics, sensing and biomedicine.

The project seeks to have significant impact on the semiconductor industry, offering a new production method for highly ordered regular arrays of identical nanostructures. New manufacturing approaches such as this are vital to the development of new quantum device systems as well as providing significant opportunities for reduced production cost and yield gains in existing device processes. We strongly believe that present process approaches are fundamental flawed in their capability at the true nanoscale.

Each of our three objectives has the potential to generate significant academic and industrial interest, which will be realised through patents, research publications and conference/workshop, depending on the nature of the disclosure. Key developments in semiconductor nanostructuring and new device measurements enabled by these processes attract publication impact at the highest level, through leading journals such as Nature and Science and we will also seek to disseminate them at leading international conferences in the field.

Our novel approach has already generated significant interest from UK companies within the semiconductor device manufacturing sector (including IQE, Huawei and Oclaro) and Oclaro has kindly offered significant in-kind financial support. These companies have substantial operations in the UK and are world leading in optoelectronic materials and devices. They are high-value industries which underpin UK employment, generate substantial inward investment and gain high-value export revenue. Companies such as these would be in a strong position to take on further manufacturing development and to apply this process in future device schemes. An alternative route to commercial impact is through the UK semiconductor instrument manufacturing sector. In the preparation of this project we have worked closely with Mantis Deposition Ltd on the initial specification of the custom system. The company has indicated its strong interest in our developments and is willing to contribute specialist expertise and technical services to the project. There are opportunities for an SME such as Mantis to develop and sell a new class of vacuum instrument, generating jobs and export revenue.

As part of our developments we would expect to generate significant novel IP. Revolutionary process developments in the semiconductor field can attract extremely high value. We may seek to licence this IP or to develop this through a university-based spin out. Sheffield has experience and a growing track record of in-house exploitation of semiconductor developments though a licensing agreement with Fusion IP. Recent spin-outs include Seren Photonics, Phase Focus Ltd and Quantasol all of which offer suitable models for further development.