Batch-fabricated MEMS retarding potential analyzer for high-accuracy ion energy measurements

We report the design, fabrication, and experimental characterization of a novel fully microfabricated retarding potential analyzer (RPA) with performance better than the state-of-the-art. Our device comprises a set of bulk-micromachined electrode grids with apertures and inter-electrode spacing compatible with high-density plasma measurements; the thick electrodes also make our ion energy sensor more resistant to ablation in harsh environments than previously reported miniaturized RPAs. Our RPA includes a set of microfabricated deflection springs for robust and compliant alignment of the grid apertures across the grid stack, which greatly increases the signal strength and minimizes the ion interception, resulting in a tenfold improvement in peak signal amplitude compared to an RPA with unaligned grids and similar inter-electrode spacing.