Micromachining of Hafnium Carbide

During this project, the microfabrication of Hafnium Carbide (HfC) was investigated. Multiple tools were considered and tested for their compatibility and effectiveness when working with HfC. The main method of choice for the machining of HfC thin films was Ion Beam Etching (IBE). In the first step, the etch rate and selectivity were determined using three different methods. Then IBE was used successfully together with a standard photolithography process to create a pattern etched through the HfC film. The dependence of the etch recipe on the etch rate and sidewall verticality was then explored. Additionally, a second process using a Silicon Oxide (SiO) hard mask was tested to improve the results with regard to sidewall verticality and fencing. It was found to lead to a slight improvement. Two methods of releasing Micro-Electro-Mechanical-Systems (MEMS) devices were also investigated. For the release from a Si substrate Xenon difluoride (XeF2) was tested and judged a suitable means. For the release of devices from a SiO release layer vapour HF was tested but found not to be compatible with HfC and leading to undesirable reactions on the surface. Ellipsometry was checked as a method of determining the thickness of the HfC film but was found to be unsuitable due to material being too absorptive.