厚膜光阻 (Thick-film photoresist)可用於製作高深寬比的結構，普遍廣泛應用於LIGA微機械加工技術，製作MEMS微電機系統元件或微結構等。負型厚膜光阻可應用於積體電路後段IC封裝，利用厚膜光阻形成高深寬比的結構圖案，產生大尺寸金屬凸塊作為中心封裝，使局部設備冷卻以提高封裝的穩定性。
本研究分成兩個部份，第一部份先以苯乙烯 (Styrene)、異戊二烯 (Isoprene)、甲基丙烯酸 (Methacrylic acid)等單體，依不同比例利用自由基聚合法 (Free radical polymerization)合成，共聚合成出不同高分子樹脂後，探討其物理特性，如分子量、玻璃轉化溫度、熱分解溫度、黏度、酸價等，並分析其官能基與化學結構等；第二部份將合成樹脂添加光起始劑 (Photoinitiator)以及其他添加劑等製備成負型光阻，進行黃光微影製程，以旋轉塗佈光阻於晶圓表面，單次塗佈達膜厚30微米，去除大部分溶劑後，以波長315~400 nm (Broad band)進行UV固化程序，最後以鹼性顯影液沖洗，使用光學顯微鏡與電子顯微鏡觀察光阻顯影效果與光阻形態。
經由微影程序，發現合成高分子平均分子量愈低，並添加增塑型樹脂時，有助於顯影的速度。在最適化條件下，可得膜厚30微米的負型光阻，圖形線寬最小達50微米。

關鍵字: 厚膜負型光阻、高深寬比、黃光微影製程、IC封裝

Thick-film photoresist is used to create the high-aspect-ratio (HAR) structure and it can be widely and commonly used in LIGA (Lithographie, Galvanoformung, Abformung) technology to fabricate HAR microstructures for MEMS (microelectromechanical systems). This photoresist can be applied in integrated circuit packaging process. A large size metal bumps, prepared with using thick-film photoresist, is often employed at center of package in order to cool the local structures. It is found to enhance the productivity of packaging process.
There are two parts in this study. In the first part, the polymer, used as binder for photoresist, were synthesized via free-radical polymerization with using styrene, isoprene, methacrylic acid and other monomers. The effects of preparation parameters on molecular weight (MW), glass transition temperature (Tg), thermal decomposition temperature (Td), viscosity and the acid value of the prepared binders were be investigated in detail. The functional groups and chemical structures were also analyzed systematically. The photoinitiator and other additives were added into the prepared polymer to synthesize the negative-type photoresist in the second-part work. The negative-type photoresist was coated on the wafer by spin coating process, where the film thickness was adjusted by spin speed to match the specification (30 μm) for photo-lithography process. Most of solvent was removed from the photoresist after soft-baking. The dried film, then, was UV-cured under radiation at wavelength from 315 to 400 nm (broad band), with different exposure. The pattern was obtained with using alkaline developers. Finally, the integrity of pattern and photoresist morphology were further observed by the microscope and the SEM.

In the photo-lithography process, the results indicated that the synthetic binder with lower average molecular weight and adding the toughener resin exhibit the more rapid development rate. The resolution of the prepared negative-type photoresist with film thickness of 30 μm could reach line width dimension of 50 μm.

Key words: Thick-film photoresist, high aspect ratio, photo-lithography, IC packaging

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