Microscopic evidence of carbide formation at the interface of tungsten-based ohmic contacts on diamond

Abstract

The fabrication of ohmic contacts is a fundamental technological step toward the development and manufacture of reliable electronic devices. However, in the case of diamond-based devices, there is a lack of knowledge related to the formation of these types of contacts. While the role of interface carbide formation on refractory–metal/diamond contacts has been reported as a key mechanism for the thermal stabilization and optimization of ohmic behaviour; there is still a lack of knowledge, at the diamond/tungsten (W) interface, related to the structural and chemical characteristics versus electrical performance. To fulfil this lack, W onto boron-doped diamond contacts were fabricated on a p+diamond layer by Electron-Beam Induced Deposition and followed by an annealing process. Then, W-diamond contacts were chemically, electrically, and structurally characterized at room temperature before and after thermal treatment. Once annealed, the Transfer Length Method (TLM) analysis revealed ohmic behaviour with specific contact resistance of 2.74 ×10 4 Ω⋅cm2. Electron Energy Loss Spectroscopy in Scanning Transmission Electron Microscopy (STEM-EELS) revealed tungsten carbide (WC) formation at the interface after annealing. So, a relation between WC formation and ohmic contact characteristics is demonstrated.