於平面基板與滾筒表面以步進對準式干涉微影技術接合次微米週期性圖案

Stitching Submicron Periodic Patterns over a Planar Substrate and a Roller by Utilizing Step-and-Align Interference Lithography

陳永彬(Yung-Pin Chen)

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/博士(2011年)

https://doi.org/10.6342/NTU.2011.01439

摘要

本論文研發一套步進對位式干涉微影系統，可於四吋矽晶圓與直徑五公分的金屬滾筒上製作大面積次微米週期性圖案，藉由雙光束干涉微影於基板上曝光出小區域方形面積的干涉條紋圖形，再透過高精準度的控制系統定位平台步進移動或轉動基板，將小面積的次微米週期性圖案接合成大面積。
步進對位式干涉微影系統可分為兩種模式：平面與滾筒模式，即可分別在平面基板或滾筒表面接合製作大面積次微米週期性圖案，利用一可翻轉之反射鏡控制雷射光束的傳播方向，可簡易地切換干涉曝光操作在平面或曲面模式。每個模式之光學系統均包含三組光學機構，分別為光束穩定機構，其將來自於另一張桌面上的氬離子雷射光束做持續性追蹤穩定光束的飄移；光擴束機構，將小直徑之雷射光束擴大為大面積平面高斯光束；雙光束干涉機構，由分光鏡將擴束光強度均勻等分為兩道，再重合於塗佈有光阻之基板上，以產生干涉圖形。
針對步進對準接合的需求設計一適當光束以產生小面積曝光區域，其曝光劑量在這小區域中的分佈可於大面積完全接合後達到均勻劑量分佈的效果，然而目前尚無技術可將雷射的高斯光束轉換為此設計之光束，因此利用一金屬片遮罩於其中央開一方型孔洞，將擴束後之高斯光束入射於基板前，截取出中心能量強度較為均勻的區域做為單位曝光面積。擴束後之高斯光強度分佈於小面積內較為平緩，因此對於光束重合於基板上時有較大的錯位誤差容忍度，即使有約2毫米的疊合錯位，兩道入射光束重合的強度分佈依然可達到干涉對比度高於0.99的效果。
於晶圓與滾筒上利用步進對準式干涉微影成功將週期約700奈米與800奈米的干涉圖案接合，晶圓接合約90塊單位曝光面積耗時約半小時，而滾筒接合約120塊單位曝光面積耗時約一小時，相對於其他次微米週期性結構製造技術，例如電子束微影，所耗費的時間大幅縮減，雖然有些許干擾因素造成干涉條紋在一次曝光區與接合區的光學反射頻譜不同，利用光學顯微鏡與電子顯微鏡的高放大倍率觀察下，次微米週期性條紋的連接與長距離的連續性沿伸均獲得證實。在不接合圖案的條件下，僅利用光學干涉微影模組，可製作週期小於300奈米之一維與二維週期性結構。

關鍵字

步進對準式干涉微影術 ； 次微米週期性圖案 ； 大面積 ； 滾筒

並列摘要

A Step-and-Align Interference Lithography (SAIL) system is developed for fabricating continuous submicron periodic patterns over a silicon wafer with diameter of 100 mm and a metal roller with radius of curvature 25 mm. By utilizing two-beam interference lithography to expose submicron periodic patterns in a small square area and the position stages with high precision control system to stepwise move or rotate the substrate, the small exposure regions are stitched to be large-area submicron periodic patterns.
The SAIL system is composed of two fabrication modes; plane mode and roller mode, which can be used to fabricate and stitch the interference patterns on a planar sub-strate and a roller, respectively. A flip bending mirror is used to control the propagation direction of laser beam, and then the interference patterns exposed in the plane or roller mode can be switched conveniently. The optical module in each mode has three functions; beam stabilization function to trace and stabilize the laser beam’s drifting from the argon ion laser placed on a separate table, beam expansion function to expand a small laser beam to a large-area collimated Gaussian beam, and two-beam interference function to have two beams interfered with equal intensity by splitting the expanded beam via a beamsplitter on the substrate coated with photoresist.
To obtain uniform exposure dose distribution over the whole large area after step-wise stitching the small exposure regions, a beam profile is designed to have the unit ex-posure area with designed dose distribution. However, there is no beam shaper to trans-form the laser beam into the designed beam. A metal mask with a square open window set up before the substrate is used to truncate the central region of the expanded Gaussian beam whose intensity distribution is more uniform to be the unit exposure area. The Gaussian intensity distribution is smoother in the small region of the expanded beam, which has large tolerance for the overlapping misalignment of two incident beams. Even though the overlapping misalignment is about 2 mm, the interference contrast in the overlapping area could still be higher than 0.99.
The interference patterns with period about 700 nm and 800 nm are stitched suc-cessfully over the wafer and the roller. There are about 90 unit exposure areas stitched over the wafer and 120 unit exposure areas stitched over the roller, which take half an hour and an hour, respectively. The process times are much shorter than those of other fabrication methods for making submicron periodic patterns such as e-beam lithography. Although the reflectance spectra of the fringes in the single interference regions and the overlapping regions vary owing to some disturbances, the connection of the submicron periodic fringes and the continuity of fringes for a long distance are verified by utilizing the OM and the SEM. The one- and two-dimensional patterns with the period smaller than 300 nm can be fabricated in the single interference regions without stitching by uti-lizing the optical interference lithography module.

並列關鍵字

Step-and-align interference lithography(SAIL) ； submicron periodic structures ； large area ； roller

參考文獻

[61] Jer-Haur Chang, Yung-Pin Chen, Shieh-June Chiu, Lon A. Wang, Cheng-Hung Chen, Lien-Sheng Chen, and Jia-Yush Yen, "A method of measuring grating period obtained by step-and-align interference lithography," presented at the 34th International Conference on Micro- and Nano-Engineering, Athens, Greece, 2008.

[1] Yung-Pin Chen, Cheng-Hung Chen, Jer-Haur Chang, Hsin-Chieh Chiu, Guan-Yu Chen, Chieh-Hsiu Chiang, Lien-Sheng Chen, Ching-Tung Tseng, Chih-Hsien Lee, Jia-Yush Yen, and Lon A. Wang, "Stitching periodic submicron fringes by utilizing step-and-align interference lithography," Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, vol. 27, pp. 2951-2957, 2009.

[2] Lon A. Wang, Yung-Pin Chen, Chih-Sheng Jao, Shuo-Hung Chang, and Jer-Haur Chang, "Method and Apparatus for Generating Periodic Patterns by Step-and-align Interference Lithography," in Republic of China, People's Republic of China, USA, and Germany, Unpublished patent.

[3] Jia-Yush Yen, Shu-Hung Chang, Cheng-Hung Chen, and Lien-Shen Chen, "Positioning method and apparatus and system of interference lithography," in Republic of China, Unpublished patent.

[4] Ralf K. Heilmann, Carl G. Chen, Paul T. Konkola, and Mark L. Schattenburg, "Dimensional metrology for nanometre-scale science and engineering: towards sub-nanometre accurate encoders," Nanotechnology, vol. 15, p. S504, 2004.