Epitaxy, characterisation and microfabrication of tailor–made 3C–SiC/Si heterostructures for advanced technological semiconductors

Since the pioneering work of Nishino et al. (Journal of Electrochemical Society, 1980), which introduced multi-step growth for heteroepitaxial cubic silicon carbide (3C–SiC) on silicon (Si) via chemical vapor deposition (CVD), progress in achieving high-quality, relaxed 3C–SiC films has been limited. 3C–SiC and 3C–SiC/Si heterostructures have enormous potential in advanced sensors for harsh environments as well as compact, high frequency and high power electronics. Persistent material challenges, including defects and wafer bowing, have hindered the large-scale production and commercialisation of 3C–SiC/Si-based microdevices, with no commercially available devices to date. This thesis builds upon the recent breakthrough, a few years back but only recently published, by Myronov et al. (Materials Today Communications, 2024), demonstrating single–step silicon carbide heteroepitaxy on silicon at reduced temperatures. It presents a comprehensive investigation into the growth, characterisation, and device fabrication of 3C–SiC/Si, addressing fundamental deposition parameters and their impact on material properties. Key focus areas include the growth precursor ratio and temperature dependencies, which challenge conventional assumptions regarding the optimal Si-to-C atomic ratio for stoichiometric growth. The first part of the thesis explored the deposition kinetics of 3C–SiC, whereby ultra-thin epilayers down to a few nanometres are successfully produced with improved crystallinity by careful control over growth rate. Then, a systematic study on Si and C atomic ratios by changing their precursors’ flow rates, with and without intentional doping, revealed an optimal stoichiometric balance with high reproducibility. Of particular importance here were the discussions about managing and minimizing the wafer bow with no negative impact on crystalline quality and its implications with respect to reshaping the understanding of 3C–SiC growth mechanisms. The second part focuses on the microfabrication of suspended microstructures from 3C–SiC epilayers, a process complicated by thickness variations and strain states. Suspension helps harvest true electrical, mechanical and optical properties by isolating epilayers from the substrate and providing movable parts in and out of substrate plane. Using an all-dry fabrication process, thin films were successfully suspended with and without metallization. However, metallization challenges—including equipment downtime and processing limitations—necessitated wet chemical etching, significantly reducing fabrication yield, particularly during wire bonding. These fabrication bottlenecks, along with potential solutions, are critically examined to guide future improvements. Beyond its immediate implications for commercial viability, this work showcases 3C–SiC as an state of art material for advanced semiconductor technology with tuneable properties, and demonstrates material potential in applications as microstructures and microsensors through which fundamental material properties such as elastic modulus and thermal conductivity may be extracted. The insights gained from this work open new possibilities for integrating 3C–SiC/Si into next-generation semiconductor applications, particularly in areas where traditional materials face fundamental limitations. It may also become an authoritative reference and a roadmap of critical research about compound semiconductors for the wider scientific community.