非平面奈米壓印微影製程開發及其光學元件製作研究

Development of Non-planar Nanoimprint Lithography Processes and its Optical Applications

李煜斌(Yuet-Ping Lee)

指導教授 ： 王倫

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01153

摘要

非平面基材之次微米結構元件製作，最近頗受各界的矚目。曲面有很多傳統平面結構達不到的特殊效果，例如：碟式太陽能聚光器、複眼影像感測器、航太工程飛行元件、光學透鏡裝置、天文光學元件等，產業上應用發展潛力極大。

當前可進行曲面奈米壓印微影的方法不多，機器設備昂貴且製程條件受限，壓印面積也受侷限。本文提出了一種非平面奈米壓印微影方法，係結合了塑膠熱壓成型術(Thermoforming)及傳統奈米壓印微影術(Nanoimprint Lithography)，可在曲面上達到大面積均勻施壓及不壓破脆性基材之目的，此法也可擴充至曲面雙邊微結構壓印應用。

本研究第一部分先改良傳統旋轉塗佈機之挾持機構，成功在 2吋碟型曲面基材上塗佈出阻劑，並以非接觸式光學薄膜量測儀檢測塗佈厚度。量測結果發現阻劑塗佈均勻，惟在曲面邊緣處受離心力影響較厚。在壓印製程方面，吾人首先利用熱壓成型法預製出特定形狀的密封薄膜，再搭配PDMS軟性模具及氣體施壓機構，軟模可與曲面基材表面完整接觸，因此有效壓印面積大幅提昇，且達到均勻的壓印效果。

本研究進一步探討各種曲面光學元件應用，先以干涉微影術製做次微米繞射光柵，將其翻製成PDMS軟模具後，以此曲面奈米壓印製程來製作各種光學元件。已成功製得2吋羅蘭圓(Rowland Circle)式凹面型光柵，其光柵週期為1.2 μm，實際測試可見光的分光效率約為20 %。此外，亦製出雙表面堆疊光柵元件，初步已可分出9道光束，未來可應用於光學微影術、光通訊和極化分光器上。由此看來，曲面微奈米結構元件之發展應用空間極大。

關鍵字

非平面 ； 奈米壓印微影 ； 干涉微影 ； 熱壓成型 ； 羅蘭圓 ； 堆疊

並列摘要

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.

並列關鍵字

non-planar ； nanoimprint lithography ； interference lithography ； thermoforming ； Rowland circle ； stacked

參考文獻

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