Chemically Enhanced Focused Ion Beam Selective Patterning of Titanium, Titanium Oxide and Nitride Thin Films
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0983-LL02-05
Chemically Enhanced Focused Ion Beam Selective Patterning of Titanium, Titanium Oxide and Nitride Thin Films Andrei Stanishevsky1 and John Melngailis2 1 University of Alabama at Birmingham, Birmingham, AL, 35294 2 University of Maryland College Park, College Park, MD, 20742 ABSTRACT Focused ion beams (FIBs) provide maskless prototyping of 2-D and 3-D micro- and nanostructures for many applications in optics, electronics, and medicine. In many situations, the chemical enhancement of the FIB sputtering process is used to increase the selectivity and removal rate of different materials. In this study, Ti, TiO2, and TiN thin films of different origin were patterned using Ga+ FIB without or with chemical enhancement (or gas assisted etching, GAE). The effects of ion beam parameters and gas ambient on the sputtering yields, etching selectivity, roughening at the film/substrate interface, sub-micron and nano-scale patterning of these materials were investigated. Several gases, including XeF2, CO2, chlorine, bromine, and oxygen, were employed. The largest increase of the sputtering yield was achieved with XeF2 gas, whereas CO2 and oxygen depleted the sputtering rate. Among all gases tested, the Br2 FIB GAE produced the best uniformity of the material removal. It was found that the use of bromine gas provides the best selectivity between the titanium oxide and pure titanium or its nitride.
INTRODUCTION Over the last two decades, focused ion beams (FIB) have become a popular tool for surface modification of materials and functional structures prototyping at micro- and nano-scale. Principles of focused ion beam equipment design, generation of ion beams, and the applications of the technique have been thoroughly discussed in numerous reviews, for example [1-5]. The main applications of FIB processes today are mostly concerned with local ion sputtering or modification of the material. This technique is used for defect repair of optical and X-ray masks, electronic, optical, and MEMS device prototyping and modification, failure analysis of circuits and devices, sample preparation for transmission electron microscopy (TEM), ion microscopy and secondary ion mass spectroscopy (SIMS), and experiments on direct maskless fabrication of a variety of micro- and nanostructures. A number of factors determine the FIB micro- and nano-machining results, including ionbeam diameter, current and ion mass, angular effects caused by edges or depth variations across the pattern, and the redeposition of sputtered material. The sputtering yield of various materials in the typical range of ion energies used in FIB is usually 1-3 atom/ion. To enhance the sputter yield by a factor between 2 and 30 and to suppress the redeposition of sputtered material, FIB gas assisted etching (GAE) is often used. The principle of ion beam gas assisted etching (GAE) is to adsorb suitable precursor gas molecules on a substrate and expose them to an ion beam. The ion beam causes a reaction between the adsorbed gas molecules and the substrate atoms, forming v
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