Participation of focused ion beam implanted gallium ions in metal-assisted chemical etching of silicon

Metal-assisted chemical etching (MaCE) of silicon has proven to be a fast and effective method to fabricate 1D, 2D, and 3D micro- to nano-scale features in silicon. It has been shown that platinum catalysts deposited using focused ion beam (FIB) are a viable catalyst for MaCE; however, the feature fidelity of channels etched with FIB patterned catalysts are found to be significantly lower than catalysts formed using e-beam lithography. In this work we show that gallium (Ga⁺) ions implanted into the silicon during sample exposure result in significant etching in the irradiated regions as well as long-distance etching peripheral regions. The accelerating voltage, dose, and etching time were varied to show that the etch depth depends primarily on accelerating voltage and is largely independent of dose while the width of the peripheral region was found to scale with dose. The slope of the peripheral etching region was found to vary with both accelerating voltage and dose with three different etching times evaluated to examine how the etch profile evolves over time. These results show that Ga⁺ ions do participate in MaCE and care must be taken when a Ga⁺ ion based FIB is used.