Effective removal of metal-carbide contamination from diamond circuit boards by reactive ion etching

Recently, we have demonstrated the feasibility of using laser-patterned polycrystalline diamond sheets as a substrate for implantable circuit boards. The laser grooves in the diamond can be filled with biocompatible braze alloys such as Au-ABA and polished back to create long-lasting, hermetic circuit boards suitable for implantation in the human body. However, during the process of depositing molybdenum and niobium layers to aid adhesion of the Au-ABA braze, a residual film was found to form, which was resistant to both polishing and chemical etching, resulting in electrical shorting between features on the circuit board. Here, we report an optimised reactive ion etching process to remove the residual metal contamination and electrically isolate fine features on the diamond circuit boards. Samples were evaluated through energy dispersive spectroscopy elemental analysis and electrical testing of the diamond surface, confirming the complete removal of contaminants from the diamond surface.