Energetic Neutral Atom Beam Lithography/Epitaxy for Nanoscale Device Fabrication
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J21.3.1
Energetic Neutral Atom Beam Lithography/Epitaxy for Nanoscale Device Fabrication
Elshan A. Akhadov, Alexander H. Mueller, and Mark A. Hoffbauer Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A. ABSTRACT Energetic neutral atom beam lithography/epitaxy (ENABLE) is a versatile technique recently developed for patterning nanoscale features into polymer substrates. ENABLE achieves the direct activation of surface chemical reactions by exposing substrates to a beam of energetic neutral atoms. Polymers that form volatile oxidation products may be anisotropically etched using a neutral beam of oxygen atoms at rates exceeding 100 nm/min, avoiding problems associated with charged species inherent to other etching techniques. We report on a top-down approach for producing high-aspect-ratio nanoscale structures in polymeric materials using ENABLE. Masking techniques suitable for ENABLE etching are discussed along with applications involving the rapid production of nanoscale features over large areas. INTRODUCTION Dry etching of polymer materials by traditional approaches presents many significant challenges [1-7]. Plasma etching techniques usually involve charged species that deposit considerable charge into substrates leading to degradation of etched features [1-4]. Energetic plasma species can damage delicate polymeric materials by sputtering and related processes [5]. In addition, complex etch chemistries may result in changes in the chemical composition of polymer surfaces. New technologies that alleviate the aforementioned issues are becoming increasingly important. The use of neutral atomic species with energies on the order of chemical bond strengths (a few eVs) offers many advantages over conventional approaches due to their charge neutrality and chemical specificity. The advantages in using energetic neutral atoms for materials processing apply to both polymer etching and thin film growth. However, achieving high etch/growth rates over large areas requires a high flux of atomic species. Recently, we have developed a technique for attaining these goals called energetic neutral atom beam lithography/epitaxy (ENABLE), as schematically illustrated in Collimated Neutral O-Atom Beam Figure 1. This technique utilizes an atomic beam source that produces a flux of ~1017 atoms/cm2 sec (equivalent to 100 monolayers/sec) of collimated neutral atomic species with energies between 0.5 and 5 eV over an ~20 cm2 area [8]. Etching occurs when energetic oxygen atoms impinge upon polymer surfaces to form volatile reaction products (CO, CO2, Mask H2O, etc.) that are effectively pumped away. The inherent Polymer properties of the O-atom beam (charge neutrality and ~98% Substrate atomic content) and the very direct chemistry involving the interaction of energetic oxygen atoms with polymer surfaces, Figure 1. Schematic of ENABLE allow reproduction of mask features into polymeric films with a used for anisotropic etching.
J21.3.2
high degree of anisotropy. The etched features are very well defined an
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