Abstract
Generation of focused multiple ion beamlets from an intense microwave plasma source is investigated for the creation of localized subsurface modification of materials. Unlike conventional single element focused ion beam (FIB) systems, the plasma source is capable of providing ion beams of multiple elements. Two types of plasma electrodes (PE) are employed, one with a honeycomb structure with notched apertures and another with a 5×5 array of through apertures, both attached to the plasma source and are capable of generating focused ion beamlets (50 - 100 μm diameter) in a patterned manner. Measurements of ion saturation current near the PE indicate that the plasma is uniform over an area of ∼ 7 cm2, which is further confirmed by uniformity in extracted beam current through the apertures. The ion beams are applied to investigate change in electrical sheet resistance Rs of metallic thin films in a controlled manner by varying the ionic species and beam energy. Results indicate a remarkable increase in Rs with beam energy (∼ 50 % at 1 keV for Ar ions), and with ionic species (∼ 90% for Krypton ions at 0.6 keV), when 80 nm thick copper films are irradiated by ∼2 cm diameter ion beams. Ion induced surface roughness is considered as the main mechanism for this change as confirmed by atomic force microscopy (AFM) measurements. Predictions for micro-beamlet induced change in Rs are discussed. The experimental results are verified using TRIM and AXCEL-INP simulations.
Highlights
Ion beam tools are useful for basic science, technology as well as material studies
Ion saturation current were measured by using bent Langmuir probes of three different sizes and shows the uniformity of plasma over the plasma electrodes (PE)
SRIM and TRIM simulations are performed to study the ion ranges inside the sample in order to optimize the sample thickness for use in the experiments
Summary
Ion beam tools are useful for basic science, technology as well as material studies. Over the years different kinds of ion beams having energies in the range, starting from few electron volts to millions of electron volts have been used for research and applications. The penetration depth inside the material would change. This allows us to selectively modify any particular layer inside the material by selecting the beam energy. With the rapid development of nanotechnology, focused ion beam (FIB) systems are becoming increasingly important as they are widely used for micro fabrication,[1] nano-machining,[1,2] ion lithography,[3] nano-implantations etc. These are comparatively high energy beams with energies of the order of few tens of kV. In last few years low energy ion beams have attracted attention due to its interesting nature of interactions with matter where primarily the subsurface atomic layers can be tailored for a variety of applications
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