近年來，利用可降解的嵌段共聚物(block copolymer)經由自組裝(self-assembly)製備奈米結構薄膜(nanostructured thin film)已成為趨勢，也因其於不同研究領域之應用而被廣泛研究。而為了製備符合實際應用的嵌段共聚物薄膜，如何達到自組裝奈米微結構的有序性與定向性控制為應用開發的關鍵。取向自組裝(Directed Self-Assembly)，由於結合了由大而小(top-down)和由小而大(bottom-up)的方式，可成功改善有序性並控制奈米微結構薄膜的定向性，被廣泛用於奈微機電系統之應用研發。
由於星狀(star-block)嵌段共聚物之亂度效應(entropic effect)可形成垂直定向之嵌段共聚物薄膜，故本研究針對一特殊之嵌段共聚物系統─星狀聚苯乙烯-聚二甲基矽烷(polystyrene-b-poly dimethylsiloxane, PS-PDMS)嵌段共聚物，利用特殊蝕刻方法製備之高低差奈米圖案化基材(topographic nanopatterned substrate)，進行取向自組裝，目標為製備柱狀及層板狀之奈米微結構薄膜，使其呈現垂直定向並達到大規模有序之排列。本研究將運用熱退火處理方式，經成核成長機制達到取向自組裝，並著重於利用異相二次成核(heterogeneous secondary nucleation)機理，進行微相分離(microphase separation)之有序化排列。
本研究將探討不同大小及形狀之高低差奈米圖案化基材，對於星狀共聚物之取向自組裝的影響程度與機理，並系統性地研究星狀嵌段共聚物自組裝行為，了解嵌段共聚物經異相成核成長進行取向自組裝之機制，以改善奈米微結構薄膜之有序性及達到定向性控制之理論基礎。由於含矽嵌段聚苯乙烯-聚二甲基矽烷共聚物之聚二甲基矽烷鏈段與聚苯乙烯鏈段，於氧電漿環境下之高蝕刻對比，聚二甲基矽烷鏈段經由氧電漿的反應性離子蝕刻（reactive ion etch），可直接轉換成多氧化矽（SiOx），成為一抗氧電漿的材料，且同時可將單純碳氫高分子聚苯乙烯鏈段降解，作一蝕刻用遮罩。故本研究利用將利用星狀嵌段共聚物經成核成長進行取向自組裝，透過氧電漿的反應性離子蝕刻，製備出大規模有序排列之垂直定向之柱狀或層板狀之多氧化矽奈米微結構薄膜。

The fabrication of nanostructured thin films from the self-assembly of degradable block copolymers (BCPs) has attracted extensive attention in the past decades, and a variety of appealing applications in different research areas have been suggested by using the nanostructured thin films. To create useful BCP thin films for practical uses, controlled ordering of self-assembled nanostructures is essential. Directed self-assembly (DSA), which combines the top-down with bottom-up methods, is of great interest in micro electro mechanical systems (MEMS) due to the ability to control orientation and improve the lateral ordering of the nanostructured BCP thin films.
In this study, we aim to examine a specific block copolymer system, star-block polystyrene-block-polydimethylsiloxane (PS-PDMS) copolymers with cylinder- and lamellae-forming phases as nanostructured thin films with perpendicular orientation and controlled lateral ordering by DSA using topographically nanopatterned substrates fabricating from a specific lithographic approach. Our previous studies found that entropic effect can be used to control the orientation of BCP thin films. Specifically, the architecture of star-block copolymers can be used to regulate the entropic contribution to the self-assembled nanostructures. As demonstrated, for star-block copolymers with the same volume fractions of PS and PDMS, perpendicularly oriented BCP nanostructures could be induced via an entropic effect regulated by the number of arms.
Here, we aim to investigate the nucleation and growth mechanisms of the self-assembled star-block PS-PDMS directed by the fabricated nanopatterns through thermal annealing. In particular, we are interested in the ordering process of the star-block copolymers through the type of secondary (i.e., heterogeneous) nucleation for microphase separation. Accordingly, the nucleation mechanism for the microphase-separated star-block PS-PDMS will be systematically studies by using topographic nanopatterns with different trench dimensions and different geometric textures. As a result, the controlled orientation and also the lateral ordering of self-assembled block copolymers through the nucleation and growth can be examined to provide the fundamental understanding of the DSA approach. By taking advantage of the high etching contrast of silicon-containing PDMS as compared to PS, the PDMS block will be oxidized into SiOx through the treatment of reactive ion etching (RIE) while the PS block can be simultaneously degenerated. As a result, the well-ordered perpendicular SiOx cylinders or lamellae can be obtained through such a graphoepitaxy approach followed by dry etching (RIE) process.

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