Understanding and Control of Lateral Contraction in Stamping Lithography
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0921-T02-07
Understanding and Control of Lateral Contraction in Stamping Lithography Zheng Li1, Li Tan2, and Gang-yu Liu3 1 Department of Mechanics and Engineering Science, Peking University, Beijing, China, People's Republic of 2 Department of Engineering Mechanics and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68516 3 Department of Chemistry, University of California, Davis, CA, 95616
ABSTRACT Thin film contraction under external mechanical stress can be used to miniaturize size and increase density of patterned features on top. Nonlinear Finite Element Analysis is used to provide guidance on this contraction process. It was found that the substrate contraction causes stress accumulation along interfaces between protruded features and substrate. These stress accumulation complexes the control of profile changes on patterned features and suggest a design of patterned features arranged beyond a critical distance to avoid cross-interference.
INTRODUCTION Stamping lithography, including soft lithography [1] and imprint lithography [2], has made deep impacts on nanomanufacturing due to its nanometer scale resolution, easiness in operation and compatibility to a variety of materials. In this process, a master stamp is used to transfer topographic features into thin films, such that, either negative or positive replicas are obtained. Many efforts have been invested to afford manufacture flexibility to stamped features, in which small scale structures with size or shape different from those on the master stamp were demonstrated [3,4]. Pathways contributing to such flexibility mainly include a fine tuning of master stamp deformation in vertical direction, such as a multi-layered master stamp design [5] or a careful control on pressuring the soft stamp [6,7]. Feature size miniaturization, on the other hand, was performed through a designated dewetting or diffusion process on the stamped material [8,9]. Further attenuation of the replica structures, however, presents great challenges, such as complication in tuning feature density, lack of means for reducing line edge roughness, as well as a much concerned resolution in competing with beam or scanning probe lithography. Recently (2006) G. Y. Liu and others presented the concept of feature miniaturization through lateral contraction of the substrate [10], which shed light on addressing part of above challenges. Lateral contraction process, such as uni- or bi-axial contraction, was used to aggressively reduce feature size and increase feature density at the same time. For instance, sub-40 nm protein gratings are revealed after contracting original sub-micrometer features, and correspondingly pattern density has been increased 10 fold. This added process in stamping suggests great flexibility in tuning both feature size and density, thus, suggesting less demand on precision manufacturing of the master stamp from other high-end lithography platforms. Since this lateral process involves a nonlinear and large-scale
deformation in elast
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