Versatile pattern generation of periodic, high aspect ratio Si nanostructure arrays with sub-50-nm resolution on a wafer
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NANO EXPRESS
Open Access
Versatile pattern generation of periodic, high aspect ratio Si nanostructure arrays with sub-50-nm resolution on a wafer scale Jian-Wei Ho1,2,3*, Qixun Wee4,2,3, Jarrett Dumond3, Andrew Tay5 and Soo-Jin Chua2,3,4,6*
Abstract We report on a method of fabricating variable patterns of periodic, high aspect ratio silicon nanostructures with sub-50-nm resolution on a wafer scale. The approach marries step-and-repeat nanoimprint lithography (NIL) and metal-catalyzed electroless etching (MCEE), enabling near perfectly ordered Si nanostructure arrays of user-defined patterns to be controllably and rapidly generated on a wafer scale. Periodic features possessing circular, hexagonal, and rectangular cross-sections with lateral dimensions down to sub-50 nm, in hexagonal or square array configurations and high array packing densities up to 5.13 × 107 structures/mm2 not achievable by conventional UV photolithography are fabricated using this top-down approach. By suitably tuning the duration of catalytic etching, variable aspect ratio Si nanostructures can be formed. As the etched Si pattern depends largely on the NIL mould which is patterned by electron beam lithography (EBL), the technique can be used to form patterns not possible with self-assembly methods, nanosphere, and interference lithography for replication on a wafer scale. Good chemical resistance of the nanoimprinted mask and adhesion to the Si substrate facilitate good pattern transfer and preserve the smooth top surface morphology of the Si nanostructures as shown in TEM. This approach is suitable for generating Si nanostructures of controlled dimensions and patterns, with high aspect ratio on a wafer level suitable for semiconductor device production. Keywords: Sub-50-nm resolution; User-defined patterns; Wafer scale; Non-porous; Si nanostructures; Step-and-repeat nanoimprint lithography; Metal-catalyzed electroless etching PACS: 81.16.Hc; 81.16.Nd; 81.05.Cy
Background Silicon nanostructures have unique optical, electrical, and thermoelectric properties not observed in its bulk embodiment. The advantages conferred by these traits have seen Si nanostructures being applied in nanoelectronics for transistor miniaturization [1-3], photovoltaics for exceptional light trapping [4-6], and photodetection for ultrahigh photoresponsivity [7]. Si nanostructures such as Si nanowires (SiNWs) have also enabled ultra-sensitivity to be realized in chemical and biological sensing [8], efficient * Correspondence: [email protected]; [email protected] 1 NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Centre for Life Sciences, #05-01, 28 Medical Drive, Singapore 117456, Singapore 2 Centre for Optoelectronics, Department of Electrical and Computer Engineering, National University of Singapore, Block E3 02-07, Engineering Drive 3, Singapore 119260, Singapore Full list of author information is available at the end of the article
thermoelectric performance [9], enhanced performance in Li-ion batteries [10], and n
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