Development of silicon carbide plasma etch processes for next generation power electronics

The Research Engineer will develop new processes for plasma etching of Silicon Carbide (SiC) and develop new applications in Power Electronic based on SiC devices.

The market for SiC power devices is set to grow exponentially - driven by the electric vehicles market. The trend in terms of hybrid (HEV) / battery electric vehicle (BEV) powertrains is to push the DC voltage to beyond 600V, utilising high battery capacity systems. The purpose here is to reduce the demanding cabling requirements currently hampering electric vehicle performance. Beyond 600V, the only viable power semiconductor device option that can achieve the required efficiency levels is SiC. SiC power MOSFETs will be used within the main inverter powertrain, including a DC boost converter stage if required. Moreover, these higher voltage electric vehicle sales are set to reach 18 million by 2023. When one considers that this represents 16.2% of total global vehicle sales, the market relevance becomes obviously apparent.

The Research Engineer will develop process technology for SiC devices, plasma dicing and new mask coatings. Robust coatings are required for etch-mask materials to pattern and etch trench structures in SiC wafers. These material coatings could be polymers, dielectrics or metals. These coatings will be deposited using SPTS tools for testing. Mask coating development will include conformal dielectric (SPTS MVD system). These coatings will also be trialled for contact pad and gate structures. Further processes will be developed to fabricate metal-oxide-semiconductor field-effect transistors (MOSFETs) in SiC. Novel SiC trench MOSFET designs will be investigated. SiC trench MOSFETs are seen as the future of SiC power devices, with the reduced device pitch enabling a greater number of devices per unit area and thus, enabling lower cost. The challenge is to minimise sidewall microtrenching and striation through efficient mask coatings and process control.

These SiC Power devices will be tested for high voltage applications such as high-efficiency inverters in DC/AC converters for solar/wind power supplies and electric/hybrid vehicles power conversion.

The Research Engineer will work with the APS SPTS Technologies dielectric etch tool to develop plasma etch recipes to produce vertical side walls. Etch processes will also be investigated further to develop a deep etch process for SiC plasma dicing. Plasma dicing is a signature process for SPTS's silicon etch tools, but dicing technology has not been fully developed for SiC. The future of power electronic devices will require SiC plasma dicing processes to decrease die size and increase fabrication flexibility.

The challenges for this project will be the development of the masking material, which needs to maintain high resolution features and survive the intense plasma etch process. Additionally, developing a high power etch process that can etch through SiC at high rates (1 micrometre /minute) whilst maintaining vertical (and smooth trench walls). This will be important for both the development of power devices and the plasma dicing process.

The outcomes of the proposed research are multiple and include (i) creating new masking materials for high power vacuum etch tools, (ii) developing new plasma processes for deep SiC etching for both trench and plasma dicing application (iii) characterising new power electronic devices for high voltage applications based on SiC materials.

The CDT will produce 50 graduates with doctoral level knowledge and research skills focussed on the development and manufacture of functional industrial coatings. Key impact areas are:

Knowledge
- The development of new products and processes to address real scientific challenges existing in industry and to transfer this knowledge into partnering companies. The CDT will enable rapid knowledge transfer between academia and industry due to the co-created projects and co-supervision.
- The creation of knowledge sharing network for partner companies created by the environment of the CDT.
- On average 2-3 publications per RE. Publications in high impact factor journals. The scientific scope of the CDT comprises a mixture of interdisciplinary areas and as such a breadth of knowledge can be generated through the CDT. Examples would include Photovoltaic coatings - Journal of Materials Chemistry A (IF 8.867) and Anti-corrosion Coatings - Corrosion Science (IF 5.245), Progress in Organic Coatings (IF 2.903)
- REs will disseminate knowledge at leading conferences e.g. Materials Research Society (MRS), Meetings of the Electrochemical Society, and through trade associations and Institutes representing the coatings sector.
- A bespoke training package on the formulation, function, use, degradation and end of life that will embed the latest research and will be available to industry partners for employees to attend as CPD and for other PGRs demonstrating added value from the CDT environment.

Wealth Creation
- Value added products and processes created through the CDT will generate benefits for Industrial partners and supply chains helping to build a productive nation.
- Employment of graduates into industry will transfer their knowledge and skills into businesses enabling innovation within these companies.
- Swansea University will support potential spin out companies where appropriate through its dedicated EU funded commercialisation project, Agor IP.

Environment and society
- Functionalised surfaces can potentially improve human health through anti-microbial surfaces for health care infrastructure and treatment of water using photocatalytic coatings.
- Functionalised energy generation coatings will contribute towards national strategies regarding clean and secure energy.
- Responsible research and innovation is an overarching theme of the CDT with materials sustainability, ethics, energy and end of life considered throughout the development of new coatings and processes. Thus, REs will be trained to approach all future problems with this mind set.
- Outreach is a critical element of the training programme (for example, a module delivered by the Ri on public engagement) and our REs will have skills that enable the dissemination of their knowledge to wide audiences thus generating interest in science and engineering and the benefits that investments can bring.

People
- Highly employable doctoral gradates with a holistic knowledge of functional coatings manufacture who can make an immediate impact in industry or academia.
- The REs will have transferable skills that are pertinent across multiple sectors.
- The CDT will develop ethically aware engineers with sustainability embed throughout their training
- The promotion of equality, diversity and inclusivity within our cohorts through CDT and University wide initiatives.
- The development of alumni networks to grow new opportunities for our CDT and provide REs with mentors.