(131c) Coarse-Grained Molecular Dynamic Simulation of PS-PMMA Block Copolymer Directed Self-Assembly on a Flexible Brush Substrate

Directed self-assembly (DSA) of block copolymer (BCP) is a promising and economic replacement for expensive EUV lithography in manufacturing periodic lamellar patterns that is widely appeared in semi-conductor and electronic fields. People have done many researches on the defect which is one of the main issues that hinders the wide application of BCP DSA on both simulation and experiment sides. Meanwhile, an evenly distributed line space pattern, in other word, low critical dimension (CD) variation, is also critical for the quality of formed pattern but in relatively lack of studying.

A coarse-grained molecular dynamic (CGMD) model has been applied on the studying of polystyrene-b-poly (methyl methacrylate) (PS-b-PMMA) block copolymer DSA process. Chemoepitaxy method has been simulated. During AIChE 2020, we reported a model with the neutral area (hydroxyl terminated PS-PMMA brush) as well as pinned area (cross linked PS) was simplified as steady beads called “steady bead substrate” in the figure. This model provides a decent amount of understanding towards the BCP DSA process in LiNe flow and the influence of topographic structures. To acquire more accuracy and gain the ability to investigate more properties like brush surface condition, recently a new model was carried out, in which the neutral area steady beads were replaced with realistic flexible short chain brushes composed by PS and PMMA randomly called “flexible brush substrate” as in the figure.

Many parameters that are difficult to precisely control can be modified and studied using this simulation model. Before the introduction of those real short chain brushes, three substrate topographic parameters’ influence on the formed structure were studied using “steady bead substrate” model, they are the gap between pinned area and neutral substrate (A in the bottom left graph), pinned area width (B in the bottom left graph) and distance between side walls (C in the bottom left graph). Now with the more realistic flexible brush model, we focus more on other parameters including 1) brush surface defect, 2) brush chain length, 3) brush surface roughness and 4) the substrate topography as a whole (the gap between raised pinned area and brush top surface). The influence of those parameters on the CD variation and roughness of the formed lamellar structure are investigated.

The same topographic influence was found in flexible brush substrate as that in previous steady bead substrate system, which also verifies our model. It is also shown that neutral brush surface roughness has a significant effect on formed lamellar quality, but it is not obvious influential to the defect level of formed structure. Those results can be used as a guidance for high quality lamellae manufacture. This flexible brush model can also provide us a deeper and thorough understanding of the BCP DSA process and can be extended to the study of many other BCP DSA flow system like contact-hole flow and as so on.