本論文以數位光學中的微反射鏡陣列為基礎，建構一套完整的無光罩式微影系統，包括硬體架構、軟體程式、系統整合、與實驗測試。該微影系統是以動態曝光與掃描的方式，在光阻上建構二維或三維的紫外光劑量分布，經過光阻顯影製程後，產生圖案化之二維或三維的光阻微結構。為了精準定義紫外光的曝光位置與劑量，首先建立一套輔助式光學量測與檢測系統，詳細記錄紫外光光點的能量分布與光點陣列實際投影在加工平面上的座標；之後根據此一量測結果，發展出光點陣列之跳躍式斜掃描的曝光演算法，同時搭配紫外光光源的頻閃技術，完成一高精度、高解析度、大面積、與高產率的無光罩式微影設備與曝光技術；最後，通過多項實驗驗證了此一系統架構與曝光演算法的功能與可行性，並優化製程中的各項參數。
在平面與二維的無光罩式微影製程上，本論文開發的無光罩式微影系統可以在八吋(最大可達十二吋)矽晶圓的面積內製作出各種不同線寬線距的複雜光阻圖案，具體範例是應用於電子封裝的高精度印刷電路板，其微電路的最小線寬/線距可穩定達5/5微米，單一光機曝光一片完整的八吋矽晶圓需要11分鐘，本論文建立的微影系統比起世界頂尖的海德堡商用型無光罩曝光機、型號MLA150，節省約31 %的曝光時間。
在立體或三維微結構的無光罩式微影與製程上，本論文利用數值方法控制紫外光光點曝光時的密度分布，經由捲積計算與光阻曝光時的特性曲線，可以數值模擬光阻顯影後的三維深度分布，形成一個有系統與大面積的三維微結構製程技術；實際應用範例是針對平面顯示器中背光模組的導光板，可以於6分鐘內在一個八吋矽晶圓上製做出頂寬直徑約50微米、底寬直徑約6微米、深度約14.7微米、且結構分布密度逐漸變化的凹形光阻微結構，用於製作導光板製程中所需要的原始模具；同時本論文也提出能有效解決並完全消弭大面積曝光顯影後、在視覺上有帶狀拼接條紋的方法，並經實驗驗證此一方法的可行性。
本論文完成的無光罩微影系統與軟體可以應用在大面積二維或三維的光阻曝光，此系統除了具有高精度的微結構形貌控制能力外，其產率亦可以匹敵目前工業界正在使用的商用機台，同時可以自由搭配各種不同選項的子系統架構，或是調控各種製程參數，能以高度客製化的目標來優化系統的功能與表現，成為微製造領域中一項極具發展潛力的重要機台與技術。

Based on the digital micromirror device (DMD) in digital light processing (DLP) technologies, this dissertation constructs a maskless lithography system including hardware architecture, software program, system integration, and experimental testing. This lithography system is able to deliver a two-dimensional (2D) or three-dimensional (3D) distribution of ultraviolet (UV) dose on a photoresist (PR) layer by means of dynamic exposure and mechanical scanning. After PR developing processes, patterned 2D or 3D PR microstructures are obtained. To accurately define and control the position and UV dose distribution, an auxiliary optical inspection system is first established to measure the intensity profiles of UV light spots and their coordinates projected on the patterning plane. Furthermore, a UV patterning scheme based on obliquely scanning of the arrayed UV spots and strobe-lighting of the UV light source is developed. Finally, a high-precision, high-resolution, large-area, and high-throughput maskless lithography system for UV exposure of PR layers is completed. Through several experiments, the function and feasibility of this system and its UV exposure algorithm are verified. Various processing parameters in this maskless lithography system can be adjusted and optimized.
For planar or 2D maskless UV exposure, the maskless lithography system is applied for obtaining complex 2D PR patterns of various line/spacing within an 8-inch (up to 12-inch) silicon wafer. Typical examples are high-precision and advanced printed circuit boards (PCB) used in microelectronic circuits and packaging. The minimum line/spacing is around 5 μm/5 μm, and the total exposure time of a single optical engine for an 8-inch silicon wafer is about 11 minutes. That is to say, the lithography system established in this dissertation saves about 31% of the exposure time compared with the world's top commercial maskless lithography system (MLA150) of Heidelberg Instruments.
For maskless UV exposure and manufacturing of 3D microstructures, this dissertation uses numerical methods to control the density distribution of UV light spots. Based on UV intensity convolution and the characteristic curve of the PR layer, 3D depth profiles of the PR layer after developing can be simulated numerically. It forms a systematic method for large-area fabrication of 3D microstructures. A practical example is for light guiding plates of backlight modules in flat-panel displays. Concave PR microstructures with a top diameter of 50 μm, a bottom diameter of 6 μm, and a depth of about 14.7 μm with a specific varying density distribution can be fabricated on an 8-inch silicon wafer in 6 minutes. This 3D patterned PR layer can be used as the original mother mold in the manufacturing process of light guiding plates. Methods are also developed to effectively eliminate the band-like stitching gaps after large-area UV exposure and PR development.
The maskless lithography system developed in this dissertation can be applied to 2D or 3D UV exposure of PR layers over a large patterning area. This system not only can achieve accurate 2D lithography patterns and precise 3D profiles, but also high throughput and productivity compatible with commercialized systems used in industry. The system is very flexible in terms of a wide range of combinations of various sub-systems, as well as in adjusting the processing parameters to optimize its functions and performance. This maskless lithography system has great potential for further developments and applications in the field of micro-manufacturing.

[1] “Planography.” Encyclopaedia Britannica. https://www.britannica.com/technology/planography (accessed Jan. 9, 2023).
[2] E. Enriquez, D. Shreiber, E. Ngo, M. Ivill, S. Hirsch, C. Hubbard, and M. Cole. “Photolithography.” Optimization of Thick Negative Photoresist for Fabrication of Interdigitated Capacitor Structures. https://apps.dtic.mil/sti/pdfs/ADA615865.pdf (accessed Jan 9, 2023).
[3] T. Epicier, “3D nanoimaging of semiconductor devices and materials by electron tomography,” Ph.D. dissertation, (2013).
[4] K. Keskinbora, C. Grévent, M. Bechtel, M. Weigand, E. Goering, A. Nadzeyka, L. Peto, S. Rehbein, G. Schneider, R. Follath, J. V.-Comamala, H. Yan, and G. Schütz, “Ion beam lithography for fresnel zone plates in x-ray microscopy,” Opt. Express 21, 11747–11756 (2013).
[5] J. Niu, M. Zhang, Y. Li, S. Long, H. Lv, Q. Liu, and M. Liu, “Highly scalable resistive switching memory in metal nanowire crossbar arrays fabricated by electron beam lithography,” J. Vac. Sci. & Technol. B 34, 02G105 (2016).
[6] R. Barbucha, M. Kocik, J. Mizeraczyk, G. Kozioł, and J. Borecki, “Laser direct imaging of tracks on PCB covered with laser photoresist,” Bull. Pol. Acad. Sci. Tech. Sci. 56 (2008).
[7] B. Du, H. Zhang, J. Xia, J. Wu, H. Ding, and G. Tong, “Super-resolution imaging with direct laser writing-printed microstructures,” J. Phys. Chem. A 124, 7211–7216 (2020).
[8] K. Takahashi and J. Setoyama, “A UV-exposure system using DMD,” Electron. Commun. Jpn. Part II: Electron. 83, 56–58 (2000).
[9] A. Bertsch, H. Lorenz, and P. Renaud, “3D microfabrication by combining microstereolithography and thick resist UV lithography,” Sens. Actuator A: Phys. 73, 14–23 (1999).
[10] C. Sun, N. Fang, D. Wu, and X. Zhang, “Projection micro-stereolithography using digital micro-mirror dynamic mask,” Sens. Actuator A: Phys. 121, 113–120 (2005).
[11] C. Yuan, K. Kowsari, S. Panjwani, Z. Chen, D. Wang, B. Zhang, C. J.-X. Ng, P. V. Y. Alvarado, and Q. Ge, “Ultrafast three-dimensional printing of optically smooth microlens arrays by oscillation-assisted digital light processing,” ACS Appl. Mater. & Interfaces 11, 40662–40668 (2019).
[12] H. Zhang, T. Qi, X. Zhu, L. Zhou, Z. Li, Y.-F. Zhang, W. Yang, J. Yang, Z. Peng, G. Zhang, F. Wang, P. Guo, and H. Lan, “3D printing of a PDMS cylindrical microlens array with 100% fill-factor,” ACS Appl. Mater. & Interfaces 13, 36295–36306 (2021).
[13] M. M. Emami, M. Jamshidian, and D. Rosen, “Multiphysics modeling and experiments of grayscale photopolymerization with application to microlens fabrication,” J. Manuf. Sci. Eng. 143 (2021).
[14] Texas Instruments, “DLP7000 DLP® 0.7 XGA 2x LVDS Type A DMD,” DLPS026F datasheet, Aug. 2012 [Revised Jun. 2019].
[15] Texas Instruments, “DLP6500 0.65 1080p MVSP Type A DMD,” DLPS040A datasheet, Oct. 2014 [Revised Oct. 2016].
[16] 簡弘量（2020）。〈光點陣列斜掃描無光罩式微影系統開發〉（博士論文，國立成功大學機械工程學系，臺南，臺灣）。
[17] L. Huang, C. Liu, H. Zhang, S. Zhao, M. Tan, M. Liu, Z. Jia, R. Zhai, and H. Liu, “Technology of static oblique lithography used to improve the fidelity of lithography pattern based on DMD projection lithography,” Opt. & Laser Technol. 157, 108666 (2023).
[18] K. F. Chan, Z. Feng, R. Yang, A. Ishikawa, and W. Mei, “High-resolution maskless lithography,” J. Microlith. Microfab. Microsyst. 2, 331–339 (2003).
[19] C. Peng, Z. Zhang, J. Zou, and W. Chi, “A high-speed exposure method for digital micromirror device based scanning maskless lithography system,” Optik 185, 1036–1044 (2019).
[20] W. Allen and R. Ulichney, “Wobulation: Doubling the addressed resolution of projection displays,” in SID Symposium Digest of Technical Papers, 2005, pp. 1514–1517.
[21] K. Kim, S. Han, J. Yoon, S. Kwon, H.-K. Park, and W. Park, “Lithographic resolution enhancement of a maskless lithography system based on a wobulation technique for flow lithography,” Appl. Phys. Lett. 109, 234101 (2016).
[22] R. Chen, H. Liu, H. Zhang, W. Zhang, J. Xu, W. Xu, and J. Li, “Edge smoothness enhancement in DMD scanning lithography system based on a wobulation technique,” Opt. Express 25, 21958–21968 (2017).
[23] W. J. Smith, Modern Optical Engineering: The Design of Optical Systems, 4th ed. New York: McGraw-Hill Education, 2008.
[24] J. Park, S.-C. Byun, and B.-U. Lee, “Lens distortion correction using ideal image coordinates,” IEEE Trans. on Consumer Electron. 55, 987–991 (2009).
[25] F. Zhou, Y. Cui, L. Liu, and H. Gao, “Distortion correction using a single image based on projective invariability and separate model,” Optik 124, 3125–3130 (2013).
[26] K. Huang, S. Ziauddin, M. Zand, and M. Greenspan, “One shot radial distortion correction by direct linear transformation,” in IEEE International Conference on Image Processing, 2020, pp. 473–477.
[27] H.-L. Chien, Y.-H. Chiu, and Y.-C. Lee, “Maskless lithography based on oblique scanning of point array with digital distortion correction,” Opt. Lasers Eng. 136, 106313 (2021).
[28] S. Huang, M. Li, L. Wang, Y. Su, and F. Wang, “Research on maskless lithography system based on digital oblique scanning strategy,” J. Laser Micro Nanoeng. 15, 45–48 (2020).
[29] J. Choi, G. Kim, W.-S. Lee, W. S. Chang, and H. Yoo, “Method for improving the speed and pattern quality of a DMD maskless lithography system using a pulse exposure method,” Opt. Express 30, 22487–22500 (2022).
[30] J. Liu, J. Liu, Q. Deng, J. Feng, S. Zhou, and S. Hu, “Intensity modulation based optical proximity optimization for the maskless lithography,” Opt. Express 28, 548–557 (2020).
[31] K. Zhong, Y. Gao, F. Li, N. Luo, and W. Zhang, “Fabrication of continuous relief micro-optic elements using real-time maskless lithography technique based on DMD,” Opt. & Laser Technol. 56, 367–371 (2014).
[32] A. Kaltashov, P. K. Parameshwar, N. Lin, and C. Moraes, “Accessible, large-area, uniform dose photolithography using a moving light source,” J. Micromech. Microeng. 32, 027001 (2021).
[33] M. A. Smith, S. Berry, L. Parameswaran, C. Holtsberg, N. Siegel, R. Lockwood, M. P. Chrisp, D. Freeman, and M. Rothschild, “Design, simulation, and fabrication of three-dimensional microsystem components using grayscale photolithography,” J. Micro/Nanolithogr., MEMS, MOEMS 18, 043507 (2019).
[34] L. Mosher, C. M. Waits, B. Morgan, and R. Ghodssi, “Double-exposure grayscale photolithography,” J. Microelectromech. Syst. 18, 308–315 (2009).
[35] B. Badawi, O. Sayadi, I. Eisele, and C. Kutter, “Three-state lithography model: an enhanced mathematical approach to predict resist characteristics in grayscale lithography processes,” J. Micro/Nanopatterning, Mater. Metrol. 20, 014601 (2021).
[36] Y. Hirai, K. Sugano, T. Tsuchiya, and O. Tabata, “A three-dimensional microstructuring technique exploiting the positive photoresist property,” J. Micromech. Microeng. 20, 065005 (2010).
[37] X. Ma, Y. Kato, F. Kempen, Y. Hirai, T. Tsuchiya, F. Keulen, and O. Tabata, “Multiple patterning with process optimization method for maskless DMD-based grayscale lithography,” Procedia Eng. 120, 1091–1094 (2015).
[38] H. Chien and Y. Lee, “Three dimensional maskless ultraviolet exposure system based on digital light processing,” Int. J. Precis. Eng. Manuf. 21, 937–945 (2020).
[39] M. N. Hasan, D.-H. Dinh, H.-L. Chien, and Y.-C. Lee, “Maskless beam pen lithography based on integrated microlens array and spatial-filter array,” Opt. Eng. 56, 115104 (2017).
[40] D.-H. Dinh, H.-L. Chien, and Y.-C. Lee, “Maskless lithography based on digital micromirror device (DMD) and double sided microlens and spatial filter array,” Opt. & Laser Technol. 113, 407–415 (2019).
[41] S. Zhou, Z. Lu, Q. Yuan, G. Wu, C. Liu, and H. Liu, “Measurement and compensation of a stitching error in a DMD-based step-stitching photolithography system,” Appl. Opt. 60, 9074–9081 (2021).
[42] J. Wang, Y. Hayasaki, F. Zhang, X. Wang, and S. Sun, “Variable scattering dots: Laser processing light guide plate microstructures with arbitrary features and arrangements,” Opt. & Laser Technol. 136, 106732 (2021).
[43] J. Wang and J. Dong, “Design of flexible optical waveguide with high uniformity and efficiency for light therapies,” Opt. Lasers Eng. 151 (2022).
[44] M. Jakubowsky, J. Werder, C. Rytka, P. M. Kristiansen, and A. Neyer, “Design, manufacturing and experimental validation of a bonded dual-component microstructured system for vertical light emission,” Microsyst. Technol. 26, 2087–2093 (2020).
[45] Y.-B. Lee, G.-W. Yoon, and J.-B. Yoon, “Mass-producible structural design and fabrication method for a slim light-guide plate having inverse-trapezoidal light out-couplers,” J. Micromech. Microeng. 29, 035001 (2019).
[46] H.-X. Yin, C.-R. Zhu, Y. Shen, H.-F. Yang, Z. Liu, C.-Z. Gu, B.-L. Liu, and X.-G. Xu, “Enhanced light extraction in N-GAN-based light-emitting diodes with three-dimensional semi-spherical structure,” Appl. Phys. Lett. 104, 061113 (2014).
[47] C. M. Waits, A. Modafe, and R. Ghodssi, “Investigation of gray-scale technology for large area 3D silicon MEMS structures,” J. Micromech. Microeng. 13, 170 (2002).
[48] K. Totsu, K. Fujishiro, S. Tanaka, and M. Esashi, “Fabrication of three-dimensional microstructure using maskless gray-scale lithography,” Sens. Actuator A: Phys. 130, 387–392 (2006).
[49] N. Y. J. Tan, X. Zhang, D. W. K. Neo, R. Huang, K. Liu, and A. S. Kumar, “A review of recent advances in fabrication of optical Fresnel lenses,” J. Manuf. Process. 71, 113–133 (2021).
[50] Y. Liang, T. Zhu, M. Xi, H. N. Abbasi, J. Fu, R. Su, Z. Song, H. Wang, and K. Wang, “Fabrication of a diamond concave microlens array for laser beam homogenization,” Opt. & Laser Technol. 136, 106738 (2021).
[51] L. Wang, N. Luo, Z. Zhang, H. Xiao, L. Ma, Q. Meng, and J. Shi, “Rapid fabrication of sub-micron scale functional optical microstructures on the optical fiber end faces by DMD-based lithography,” Opt. Express 30, 676–688 (2022).
[52] 施翰昆（2022）。〈無光罩曝光機之紫外光光源開發與成像鏡頭檢測〉（碩士論文，國立成功大學機械工程學系，臺南，臺灣）。
[53] J. A. Nelder and R. Mead, “A simplex method for function minimization,” J. Comput. 7, 308–313 (1965).
[54] H. Yuen, J. Princen, J. Illingworth, and J. Kittler, “Comparative study of Hough transform methods for circle finding,” Image Vis. Comput. 8, 71–77 (1990).
[55] H.-F. Kuo and W.-C. Wu, “Forming freeform source shapes by utilizing particle swarm optimization to enhance resolution in extreme UV nanolithography,” IEEE Trans. on Nanotechnol. 14, 322–329 (2015).
[56] S. Oh, D. Han, H. B. Shim, and J. W. Hahn, “Optical proximity correction (OPC) in near-field lithography with pixel-based field sectioning time modulation,” Nanotechnology 29, 045301 (2017).
[57] B.-Y. Yu, Y. Zhong, S.-Y. Fang, and H.-F. Kuo, “Deep learning-based framework for comprehensive mask optimization,” in Proceedings of the 24th Asia and South Pacific Design Automation Conference, 2019, pp. 311–316.
[58] P. Isola, J.-Y. Zhu, T. Zhou, and A. A. Efros, “Image-to-image translation with conditional adversarial networks,” in Proceedings of the IEEE conference on computer vision and pattern recognition, 2017, pp. 1125–1134.
[59] T. Karras, S. Laine, and T. Aila, “A style-based generator architecture for generative adversarial networks,” in Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, 2019, pp. 4401–4410.
[60] T. Karras, M. Aittala, S. Laine, E. Härkönen, J. Hellsten, J. Lehtinen, and T. Aila, “Alias-free generative adversarial networks,” Adv. Neural Inf. Process. Syst. 34, 852–863 (2021).