複合式折/繞射雙面微型光學元件
於高效能影像感測器之應用

微光學元件在近年來廣泛地被應用於各種領域，包含顯示器、光學讀取頭、光通訊、生物醫學及影像感測器等各方面，其所扮演之角色雖非主角，但皆具有提供關鍵性功能的本領。本研究乃整合微透鏡陣列和閃耀式光柵於同一層光學薄膜，為一整合型功能之混合式微光學元件，並成功開發完整類LIGA製程流程，冀望所研究之雙面折/繞射式微型光學元件以其分色效能取代彩色濾光片以濾光機制過濾出色彩之功能，於高效能影像感測有所助益。雙面折/繞射式微型光學元件乃結合二項微光學元件之性質；利用矩形微透鏡陣列之聚焦功能，行空間畫素定位、提昇整體入射光線於影像感測器之充填係數，並應用閃耀式光柵依不同波長進行色散而達分色之功效；使本研究之雙面折/繞射式微型光學元件同時具有聚光和分色之特性，不再只具單一功能，而是雙重光學特性之集合體。本文乃為複合式微光學元件之研究，經由設計模擬、灰階微影、光阻蒸鍍、模具電鑄，乃至量產複製，提出一套完整之整合性類LIGA製程技術。透過穩定之半導體製程技術，進一步發展先進灰階微影製程，並使用傾斜吸收式曝光法修正原始閃耀式光柵外型頂點偏向中心的缺點，再經由精密模具電鑄技術的整合，成功地結合高分子光學塑膠材料與成型技術的使用，促進本研究所提之創新型微光學塑膠元件的產生與技術平台的建構整合。除操作尺度於微米等級外，並具有高附加價值和低量產成本的特色。應用本研究所完成之微透鏡陣列之填充係數達100%，中心厚度值為1.8μm，形成曲率半徑約為80μm之非球面鏡，且其曲率半徑仍可由微影製作當中調整；在聚焦效率量測上，利用CCD觀察，並以軟體進行光訊號讀取，可知聚焦特性極佳，且就微透鏡陣列而言所產生之聚焦強度相當均勻。另外，在閃耀式光柵量測方面，由原子力顯微鏡及掃描式電子顯微鏡進行雙重確認後，可知閃耀式光柵之外型輪廓已接近垂直三角形之幾何形狀，其周期寬度為4μm，高度達1.01μm；而在繞射效率量測上，因新式製程改良閃耀式光柵光型，在+1階效率已可達41 %以上，且高階繞射光效率可控制在8 %以下，較之傳統彩色濾光片之極限為33%，在光利用效率上已經超越傳統彩色濾光片之極限，可有效改善影像感測器於追求高畫素、高效能上遭遇到入光量不足的窘境。

關鍵字

類LIGA製程；微光學元件；傾斜吸收式微影；分色

並列摘要

Micro-optical components have been extensively applied to many fields since 1980s, including the displays, optical pick-up heads, optical interconnection, bio-medicine and image sensors, etc. This thesis reports on a hybrid refractive/diffractive micro-optical color-separation component for the application of color separation, which was based a successful UV LIGA process to fulfill the mass-production of the component, for the purpose of replacing the action of color filter on filtering the 2/3 incident light we need. Color-separation optics is a critical component for converting the color information of surroundings into electronic data. Our hybrid refractive/diffractive micro-optical Color-separation component comprises of a microlens arrays together with a layer of diffractive blazed grating, which were made on the different side of a plastic thin film. The microlens arrays play roles of focusing and positioning the incident light onto the active region of image sensor; however, the blazed grating are three-dimensional elements consisting of period-repeating right angle structures, which retard the incident wave by a modulation of the surface profile to diffract the incident light on different angles proportional to wavelengths. Thus, the Hybrid refractive/diffractive micro-optical color-separation component has the dual functions rather than focus on unique purpose. In order to combine the advantages of refractive optics and diffractive optics, considerable work has been invested in the development of hybrid elements, including the setup of specifications, simulation of the light path, and the fabrication of the complicated three-dimensional micro-structures. Moreover, we use the inclined exposure method which comes from the idea of energy absorption in the photo-resist to improve the profile of the blazed grating. The profile of our microlens is 25μm in diameter, 1.8 μm in lag, and the radius of curvature is about 80 μm. Fill factor of our microlens can approach 100%. The +1 order diffraction efficiency of blazed grating is above 41 %, superior to the best efficiency 33% of conventional color filter; besides, the diffraction efficiency of the high order terms can reduce to below 8%. Thus, our hybrid refractive / diffractive micro-optical color-separation component can increase the efficiency of the image sensor when it goes to high quality, and small pixel size.

並列關鍵字

micro-optical component ； inclined exposure method ； color-divider ； LIGA-like process

參考文獻

[1] K. Nassau, “Color for science, art and technology,” Elsevier Science B.V., 1998.

[2] G. P. Weckler, “Operation of pn Junction Photodetectors in a Photon Flux Integrating Mode”, Journal of solid-state circuits, Vol. sc2, pp.65-73, 1967.

[11] P. B. Catrysse and B. A. Wandell, “Integrated color pixel in 0.18-μm complementary metal oxide semiconductor technology”, Journal of the Optical Society of America. A, Vol. 20, pp.2293-2306, 2003.

[14] H. Dammann, “Color separation gratings”, Applied Optics, Vol. 17, pp.2273-2279, 1978.

[18] B. Layet, L. G. Cormack, M. R. Taghizadeh, “Stripe color separation with diffractive optics”, Applied optics, Vol. 38, pp.7193-7201, 1999.

國際替代計量

複合式折/繞射雙面微型光學元件於高效能影像感測器之應用

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