Etching of CoFeB nanometer thin films using inductively coupled plasma reactive ion etching

CoFeB is a critical ferromagnetic material in magnetic tunnel junctions (MTJs), the fundamental components of magnetic random access memory (MRAM) devices. The precise control of CoFeB’s etching behavior is essential for optimizing MTJ performance. In this study, the etching characteristics of CoFeB magnetic nanofilms were examined using an inductively coupled plasma reactive ion etching (ICP-RIE) system with Ar, CO/Ar, and SF6/Ar plasmas. AR-N photoresist was employed as the etching mask to investigate the effects of ICP power, radio frequency (RF) bias power, and chamber pressure on both the etching rate and the resulting morphology. Our findings demonstrate that effective etching of CoFeB can be achieved using pure Ar plasma. Additionally, optimizing power and pressure parameters improves the etching selectivity between the CoFeB nanofilm and the photoresist. However, after physical etching with pure Ar, significant redeposition was observed, leading to an increase in the nanopillar diameter. The introduction of CO or SF6 into the Ar plasma resulted in a marked reduction in the etching rate of CoFeB. Additionally, etching experiments conducted on different overlayer-substrate thin film combinations revealed notable differences in both etching rates and morphology.