用于<=11nm超细微结构制备的聚苯乙烯-聚(alpha-羟基羧酸)嵌段共聚物的引导组装

Directed assembly of block copolymers on chemical patterns holds promise to overcome the physical limitation of photolithography and is one of the most ideal alternative technologies for the fabrication of next generation integrated circuits and other devices. Currently,poly(styrene-b-methyl methacrylate)(PS-b-PMMA) and poly(styrene-b-dimethylsiloxane)(PS-b-PDMS) block copolymers are the most widely studied block copolymers for directed assembly, but both copolymers have limitations: the small interaction parameter (Chi) of PS-b-PMMA limits its smallest period (Lo) to be ~30 nm, while the large surface energy (Gamma) difference between PS and PDMS blocks makes it difficult to orient domains perpendicular to the substrate. Therefore, neither of them meets the technical requirement listed in the International Technology Roadmap for Semiconductors for the fabrication of sub-11 nm half-pitch node. In this proposal, we will design and synthesize poly(styrene-b-alpha-hydroxycarboxylic acid) with large Chi value and nearly equal Gamma value, and direct the assembly of the copolymer on chemical patterns to fabricate nanostructures with a half-pitch of sub-11 nm and desired pattern geometries for the fabrication of integrated circuits and other electronic devices. Poly(styrene-b-alpha-hydroxycarboxylic acid) combines the advantages of PS-b-PMMA and PS-b-PDMS and has large Chi and nearly equal Gamma value.More importantly, the Gamma value of the poly(alpha-hydroxycarboxylic acid) block can be finely tuned by adjusting the number of methyl groups, and the change of the number of methyl groups has little effect on the Chi value of the copolymer. Directed assembly of these blok copolymers on chemical patterns will allow to assemble perpendicularly oriented domains with a half-pitch of sub-11 nm into the derised pattern geometries for the design of integrated ciruits, which will further promote the industrilization process of the directed assembly technology.

嵌段共聚物引导组装有望突破光刻法的物理极限这一瓶颈，是制造下一代芯片的理想候选技术之一。目前，PS-PMMA和PS-PDMS等被广泛用于引导组装研究，但均有一定的局限性：PS-PMMA的相互作用参数(Chi)较小，而PS和PDMS的表面自由能(Gamma)相差较大。因此，它们均不满足半导体行业制备<=11nm半节距节点的技术要求。本项目将设计和合成具有大Chi和相近Gamma的聚苯乙烯-聚(alpha-羟基羧酸)嵌段共聚物，实现其在化学图案上的引导组装制备芯片设计所需的图案。聚苯乙烯-聚(alpha-羟基羧酸)结合了PS-PDMS和PS-PMMA的优点，有较大的Chi值和相近的Gamma值；尤为重要的是可通过改变聚酯嵌段的甲基数来调节它的Gamma值，而对共聚物的Chi值影响较小。引导组装该嵌段共聚物将可获得半节距<=11nm、垂直于基材的用于芯片设计的图案，从而推动引导组装的产业化进程。

通过电子束刻蚀、极远紫外光刻蚀或193 nm液浸曝光制备特征尺寸小于10 nm的结构存在产率低、成本高、工艺复杂的缺点。嵌段共聚物的引导自组装是制备小于10 nm结构的热点技术之一。这项技术的应用要求嵌段共聚物的两个嵌段的表面自由能（Gamma）相近，这样嵌段共聚物薄膜才能形成垂直贯穿的相畴。而且，嵌段共聚物需要具有较高的相互作用参数（Chi），才能够相分离形成周期≤20 nm的结构。.本项目选取与PS具有相近值的聚（alpha-羟基羧酸）系列聚合物进行嵌段共聚物的引导组装研究，从分子设计角度出发，通过选取不同结构或构型的单体，合成了聚苯乙烯-聚丙交酯（PS-b-PLA）、聚苯乙烯-聚乙丙交酯（PS-b-PLGA）及聚苯乙烯-聚丙交/乙丙交共聚酯[PS-b-P(LA-co-LGA)]等嵌段共聚物，并对他们的引导组装行为进行了研究。结果表明，PLA的Gamma值与立体构型或手性存在一定关系，而且对温度较为敏感，不同的PLA嵌段结构需要采用不同的退火温度。相对于PS-b-PMMA，PS-b-PLA具有更大的Chi值，可以实现更小的相分离尺寸。在此基础上，我们首次合成了PS-b-PLGA，解决了PLGA嵌段难以可控聚合以及分子量受限的难题，并测试了PS-b-PLGA的Chi值，证明了PS-b-PLGA的Chi值大约是PS-b-PLA的2倍，可以得到小于10 nm的相分离结构。另外，我们还选取乙丙交酯与丙交酯进行共聚，开环聚合合成PS-b-P(LA-co-LGA)，通过调节LGA与LA在聚酯链段中的比例，可以有效地调节其Gamma值，使其与PS更相近，而不显著改变其Chi值，并在加热退火条件下获得了垂直于基材的相分离结构。