Stability of lithographically patterned transition metal layers controls spatial selectivity during etching of diamond

Abstract

Transition metals (TM) that are lithographically patterned on surfaces of polycrystalline diamond offer a vehicle for site selective removal of carbon. Here, we present a characterization of the trade-offs between spatial selectivity, isotropy of material removal and etching rate as a function of the TM composition and heat treatment. Fe, Co, Ni and FeCoB were studied for their ability to convert and transport C from diamond under heat treatment. Following solvothermal removal of the reaction products, the surface topographies inherited by diamond were characterized using atomic force microscopy. The structure of interaction zones between diamond and TM were studied using electron microscopy and Raman spectroscopy. Ni layers remain stable during the heat treatment to enable highly selective material removal. However, Fe, Co and FeCoB layers were fragmented and transported by the reaction products, which led to loss of selectivity in material removal. The etching rate of FeCoB shows a weaker dependency with diamond surface grain orientation. Combinatorial process designs involving bilayers of Ni and FeCoB enable trade-offs in the etching rate and isotropy, including the ability to control the side profiles of the etched features on diamond. • Polycrystalline diamond was patterned using different solid-state etchants. • The mechanism of etching behavior difference of different etchants was illustrated. • FeCoB/Ni hierarchical etchant was designed to improve etching performance and achieve inclined etching.