Graphoepitaxial assembly of cylinder forming block copolymers in cylindrical holes

Abstract

The graphoepitaxial assembly of cylinder-forming block copolymers assembled into holes is investigated through theoretically informed coarse grained Monte Carlo simulations (TICG MC). The aim is to identify conditions leading to assembly of cylinders that span the entire thickness of the holes, thereby enabling applications in lithography. Three hole geometries are considered, including cylinders, elliptical cylinders, and capsule-shaped holes. Four distinct morphologies of cylinder forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymers are observed in cylinders and elliptical holes, including cylinders, spheres, partial cylinders, and wall-bound cylinders. Additional morphologies are observed in capsuleshaped holes. PMMA cylinders that extend through the entire hole are found with PMMA-wetting surfaces; a weak wetting condition is needed on the bottom of the hole and a strong wetting condition is necessary on the sides of the hole. Simu-lated are also used to explore the morphologies that arise when holes are overfilled, or when PMMA homopolymers are added in blends with copolymers. We find that overfilling can alter considerably the morphological behavior of copolymers in cylinders and, for blends; we find that when the homopolymer concentration is >10%, the range of conditions for formation of PMMA cylinders that extend through the entire hole is increased. In general, results from simulations (TICG) are shown to be comparable to those of self-consistent (SCFT) calculations, except for conditions where fluctuations become important.identifying the conditions leading to formation of ideal cylinders that span the entire thickness of the confining hole. In this work, we use simulations to identify such conditions. Graphoepitaxy relies on topography to guide the assembly of block copolymers. Segalman et al. [8][9][10][11] used primarily poly (styrene-b-2vinyl pyridine) (PS-b-P2VP) sphere forming block copolymers. Work by Cheng et al. 20,21 considered poly(styrene-b-ferrocenylsilane) (PS-b-PFS) sphere-forming diblock copolymers. One important outcome of that work was to show that defects in the confining walls can have a pronounced influence in the resulting morphology, and give rise to defective microdomains. 22 Lamellar-forming poly(styrene-b-ethyl-alt-propylene) (PS-b-PEP) block copolymers have also been assembled in trenches under preferential wetting of the PS, 23,24 and Hammond andThis article was published online on 16 December 2014. An error was subsequently identified. This notice is included in the online and print versions to indicate that it has been corrected 31 January 2015.

Design and Analysis of Stability-Guaranteed PUFs

“…Therefore, final assembly results can be random by designing guiding templates that are large enough to cause random assembly errors even if there are no lithographic variations [32]. Figure 2 shows three simulation results of the same large guiding template with an existing DSA simulator [33], where the model of the PS-b-PMMA copolymer has been validated in [34]. The three layers inside the polygonal guiding template are the top, middle, and bottom layers of a via.…”

Boundary-directed epitaxy of block copolymers

“…While the achievements of graphoepitaxy and chemoepitaxy (as well as hybrid processes adapting aspects of both techniques 27 – 29 ) have been extensive 1 – 4 , directed assembly via these methods faces several challenges. For example, graphoepitaxy is sensitive to underfilling and overfilling of BCP in the trenches 30 , 31 , and requires fabrication of topographic structures that interfere with subsequent processing if the structures cannot be removed 32 . On the other hand, chemoepitaxy requires the formation of narrow guiding features that have widths of 0.5–1.5 times the BCP domain spacing ( L 0 ), where a width of 0.5 L 0 is ideal 21 – 23 .…”

Mechanisms of Directed Self-Assembly in Cylindrical Hole Confinements

“…The interfacial energy between each surface and each copolymer block needs to be carefully tuned, in concert with the template diameter, to induce the assembly of a desired cylinder. It has been demonstrated that cylinders can successfully form in smaller template diameters if the sidewall preference is for the majority block. , However, most theoretical work has focused on cylindrical templates where the sidewall surface is preferentially wet by the minority block of a cylinder-forming block copolymer. − Peters et al, using a theoretically informed coarse-grained model, demonstrated that increasing the affinity of the sidewall for the minority block leads to a stabilization of the desired through-film cylinder morphology over other metastable structures . Laachi et al, utilizing a field-theoretic model, have also provided insights into the morphological, kinetic, and thermodynamic differences that exist between nonpreferential sidewalls and sidewalls that are preferentially wet by the minority block .…”

“…24−27 Peters et al, using a theoretically informed coarse-grained model, demonstrated that increasing the affinity of the sidewall for the minority block leads to a stabilization of the desired through-film cylinder morphology over other metastable structures. 28 Laachi et al, utilizing a field-theoretic model, have also provided insights into the morphological, kinetic, and thermodynamic differences that exist between nonpreferential sidewalls and sidewalls that are preferentially wet by the minority block. 29 These studies collectively support the conclusion that a sidewall that is preferentially wet by the minority block provides a critical boundary condition for obtaining the desired cylindrical morphology.…”