Development of Non-planar Nanoimprint Lithography Processes and its Optical Applications
Date Issued
2007
Date
2007
Author(s)
Lee, Yuet-Ping
DOI
en-US
Abstract
Patterning sub-micron structures onto non-planar substrates recently has drawn much interest, especially for the fabrication of dish solar concentrator, optical, astronomical and bio-sensing components. However, the curved surfaces are difficult to pattern down to the sub-micron regime using conventional electron-, ion-, photo-beam lithographies and diamond turning. There are only a few methods to achieve the curved patterning by nanoimprint lithography (NIL). They need complex equipments and extreme limitations in processing condition and imprinted area.
In this thesis, we proposed an effective method for fabricating sub-micron structures onto a non-planar substrate by combining thermoforming and nanoimprint technologies, called curved surface nanoimprint (CSN). CSN scheme can prevent the curved surface from crumbling that may results from high gas pressuring and could obtain uniform imprinting pressure distribution throughout the whole curved substrate. Moreover, replicating sub-micron structures onto two-sided curved, both convex and concave, surfaces is also achieved.
Firstly, we modified the mechanism of spin-coater to be suitable for coating curved substrates. The resin thickness on the 2-inch dish is measured by an optical thin-film measurement instrument. The curve fitting of the results show that the thickness is uniformly distributed except only at the radial position far from the center area and discovered thicker due to larger centrifugal force.
Secondly, we apply both soft mold and gas-assisted pressuring scheme, pre-shaping of seal film and soft holder arrangements are proposed and implemented for imprinting sub-micron structures on the soft mold onto curved surfaces. Conformal contact and uniform imprinting pressure throughout the whole area can be achieved between the PDMS mold and the curved substrate.
Finally, we explore some optical applications on curved surface nanoimprint. The grating was obtained by interference lithography and then replicated to a PDMS soft mold for fabricating the diffractive optical elements. We successfully fabricate a 2-inch Rowland circle type concave grating with period of 1.2 μm, the first order reflectance at different wavelengths was about 20%. Furthermore, a stacked multilayer grating (SMG) is fabricated by double-sided imprint. This element can diffract totally 9 beams, by which we can make use of it to design for various applications such as on photolithography, optical communication networks and beam splitter and polarization purification and so on in the future potentially.
Subjects
非平面
奈
米壓印微影
干涉微影
熱壓成型
羅
蘭
圓
堆疊
non-planar
nanoimprint lithography
interference lithography
thermoforming
Rowland circle
stacked
Type
thesis
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