Dual function of thin MoO3 and WO3 films as negative and positive resists for focused ion beam lithography

Fine patterning and metallization technologies have been studied using a combination of refractory metal oxide (MoO3 and WO3) resists and Ga+ focused ion beam (FIB) lithography. In this work, it is demonstrated that depending on the preparation condition of the films, these thin oxide films act as either a negative or a positive resist with high-contrast capability. According to the results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, the negative resist mechanism is possibly due to an FIB-induced structural change from the amorphous to the ordered state, and the positive resist mechanism is due to a change from the polycrystalline to the disordered state. In both the negative and positive cases, the delineated patterns can be directly reduced to fine Mo or W wires. The potential applications of the observed dual function of oxide resists are also discussed.