Millimeter-scale surface nano-structuring using focused ion beam milling
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0901-Ra05-16-Rb05-16.1
Millimeter-scale surface nano-structuring using focused ion beam milling
Katharine Dovidenko, Radislav A. Potyrailo, Laurie Le Tarte Materials Analysis and Chemical Sciences General Electric Company Global Research Center, Niskayuna, NY, 12309 ABSTRACT New patterning schemes for a variety of applications including sensors and photonics are explored. We present here a comprehensive study of using focused ion beam (FIB) milling to modify surfaces over millimeter-scale areas with nano-patterns of dimensions down to 30 nm. A typical example of a pattern is 40 nm diameter x 40 nm depth wells with a 200 nm pitch. Typical sample materials are metals, but polymer patterning is possible. We have also evaluated the surface of the patterned materials to ensure there are no negative effects of these patterning schemes on the future device performance. INTRODUCTION The ability to controllably modify/pattern the surface on the nano-scale has long been under study for a variety of applications including sensors, photonic bandgap crystals, information storage devices and many others [1, 2]. Our approach to surface modification is Focused Ion Beam (FIB) nano-patterning. FIB microscope uses focused beam of Ga+ ions accelerated to 30kV, which is being rastered over the surface to produce a variety of effects ranging from nanoscale surface alterations to tens of microns of removed material. Significant progress in creating sub-micron features has been demonstrated recently [3-5]. In previous years, success of FIBinduced small-scale surface modification has been severely limited by surface damage associated with rastering of a focused Ga+ beam over the sample [e.g. 6] thus making the sample unacceptable for any surface-sensitive applications. The damage that FIB is producing is related to the phenomena of physical bombardment of material by charged ions: implantation, radiation damage, amorphization, materials removal. In recent years, development of dual-beam instruments that combine FIB with scanning electron microscope (SEM) gives the advantage of using electron beam for all the pre-patterning steps. In this study, we use FEI Nova 200 NanoLab, which has high-resolution field-emission SEM column in addition to the ion column. This allows us to use exclusively the electron beam for all the pre-patterning steps thus avoiding the surface damage and contamination. Precise instrument alignment is crucial for accurate controllable patterning at nano-level. We are also evaluating the surface of the patterned materials to ensure there are no negative effects of these patterning schemes on the future device performance. FIB milling is known to produce substantial, and not always desired, alterations on the surface. Utilizing the dual-beam FIB-SEM system, we are able to exclude sample surface exposure to the ion beam when setting up the patterns. Hence, no structural damage is typically observed through SEM imaging of the surface of patterned materials. However, there are secondary ion scattering effects taking place du
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