靜電輔助噴塗用於光阻塗佈之探討與應用

Abstract

本研究開發靜電輔助噴塗裝置，將溼式光阻有效地噴塗於表面具微結構之平面與非平面圓柱基材上。本研究首先開發靜電輔助噴塗機台，接著探討將溼式光阻用靜電輔助噴塗技術應用於平面晶圓、平面具微結構之基材、金屬滾輪與微結構滾輪上，探討其厚度差異與均勻度，並與其他方式作比較。本研究利用此靜電輔助噴塗技術，結合步進式光微影技術及無電鍍鎳技術製作出剛性微結構滾輪，裝於UV固化壓印機台上，最後實際滾壓複製微結構於PET薄膜上。 塗佈實驗結果顯示，利用本研究所開發之靜電輔助噴塗機台機台能均勻的將濕式正型光阻（EPG-510）塗佈於四吋晶圓上，其均勻度 降低至5％以下，光阻厚度差異 方面（取樣長度為5 mm），可降低至121 nm上下。此外，靜電輔助噴塗可提昇塗佈之效率，在相同噴塗秒數下，使用靜電輔助噴塗之光阻厚度約為一般噴塗之兩倍。塗佈在金屬圓柱滾輪，在相同噴塗秒數3秒時，使用靜電輔助噴塗可將均勻度 由一般噴塗之19.5%降低至7.7%，厚度差異 也降低至400 nm。利用靜電輔助噴塗，證實可將光阻均勻的塗佈於有微結構之平面基材（深25 μm，寬50 μm）、有方形微結構圓柱滾輪（高度2 μm，週期143 μm）與有波浪型微結構（高度24 μm，寬度245 μm）圓柱滾輪上，其噴塗厚度差異遠比一般噴塗小，與浸潤式塗佈相當，但不會有其垂流缺陷。 本研究實際利用步進式曲面曝光機台，在圓柱型基材上定義線寬20 μm週期143 μm之連續式光阻結構，微結構平行於滾輪的軸線方向，顯影後光組線寬為19 μm，並接著使用無電鍍鎳技術，直接在滾輪上製作連續式剛性微結構（高度約為10 μm）。最後使用UV固化壓印技術，將微結構進行實際UV固化滾壓，複製於UV固化樹脂的PET膜上，轉印之深度為9.7 μm週期為143 μm，證實能利用本研究開發的靜電塗佈光阻進行步進式曝光、顯影與電鍍來直接製作微結構於剛性滾輪上，並進行UV固化滾壓複製微結構於基材上。

This study is to develop an effective mechanism for spaying photoresist on planar and non-planar substrates with high topography surface. An electrostatic-assisted spray coating apparatus for spraying photoresist on substrate has been designed and tested. First, this apparatus is used to spay photoresist on 4 type of substrates: the wafer, the planar substrate with high topography surfaces, the non-planar substrates with and without non-planar high topography surfaces. The thickness difference and uniformity of the photoresist on the substrates are measured and evaluated. The other aspect of this study is integrating electrostatic-assisted spray coating, stepped lithographic process, and electroless nickel plating process to fabricate the continuous microstructures onto the metal rollers. The rollers are then used in the UV curing roller imprinting to fabricate microstructures on PET films. The Electrostatic-assisted spray coating apparatus can successfully spay photoresist (EPG-510) on substrates. Using the electrostatic-assisted spray coating, the uniformity of photoresist is below 5% on the wafer and the thickness difference is about 121 nm. Using the electrostatic-assisted spray coating on the roller with same spray time, the uniformity of photoresist can decrease from 9.5% of traditional spray to 7.7% and the thickness difference is about 400 nm. Furthermore, using the electrostatic-assisted spray coating can effectively spray photoresist 3 kind of substrates with high topography surface: nickel plate with V groove microstructure (width 50 μm and depth 25 μm), roller with wave shape microstructure (width 245 μm and depth 24 μm), roller with rectangle microstructure (height 2 μm and period 122 μm). Compared with traditional spray coating, electrostatic-assisted spray coating yields significantly better performance in increasing uniformity and decreasing thickness difference. Electrostatic-assisted coating also avoided the defects due to the gravity-induced flow experienced in dip coating. Finally, using the stepped rotating lithography technique, the photoresist patterns with 20 μm wide line have been successfully fabricated onto the nickel-plated roller coated with electrostatic-assisted spray. Subsequently, the roller is treated with electroless nickel plating process, and the residual photoresist is removed by acetone. After that, a roller with continuous rigid nickel microstructures, with 20 μm width, 10 μm height and 143 μm period, has been fabricated. The roller is used for practical UV curing imprinting to replicate the microstructures onto PET film. Microstructures with the same period but 9.7 μm depth, have been successfully replicated on the substrates.