Optimization of block copolymer self-assembly through graphoepitaxy: A defectivity study

Abstract

International audienceIn this paper we report a synoptic methodology to evaluate and optimize the long-range order induced by graphoepitaxy of block copolymer (BCP) self-assembly. The authors focus the study on a BCP that produces hexagonally packed arrays of cylinders oriented perpendicular to the substrate with the copolymer film thickness greater than the trench depth. Prepatterned structures used in the graphoepitaxy approach have been generated by e-beam lithography on a commercial hydrogen silesquioxane resist. A suitable surface modification was accomplished by grafting a random polystyrene-r-poly(methyl methacrylate) copolymer on the prepatterned surfaces. The polystyrene-b-poly(methyl methacrylate) was spin-coated and annealed in order to generate the desired self-assembly. Since the self-assembly process is based on a thermodynamic mechanism, the induced defectivity needs to be reassessed with respect to the standard lithographic process. Using the cylinder center coordinates, a Delaunay triangulation is performed to find the nearest neighbors. This triangulation enables us to easily locate the disclinations which are characterized by having a number of nearest neighbors different from six. Thus, the number of defects can be quantified precisely. Additionally, this methodology affords an accurate evaluation of both the optimum mesa and trench critical dimensions yielding defect-free surfaces and may be extended to monitor the robustness of the BCP directed self-assembly process. Such diagnostics are critical in the implementation of large scale industrial processes

The Hole Shrink Problem: Directed Self-Assembly Using Self-Consistent Field Theory

“…A promising avenue to complement and enhance current state-of-the-art optical lithography-based technologies uses the spontaneous self-assembly of soft materials as a high-resolution patterning technique. The directed self-assembly (DSA) of block copolymers in particular has been shown in numerous experimental and numerical studies to dramatically improve the fidelity of self-assembly and reduce defectivity [1][2][3][4][5][6][7]. In the present study, we focus on a recent application of DSA in lithography, namely, Vertical Interconnect Access (VIA) lithography.…”

Field-Theoretic Simulations of Multi-Cylinder Configurations in VIA Lithography

“…The directed self-assembly (DSA) of block copolymers in particular has been shown in numerous experimental and numerical studies to provide a robust strategy for creating a variety of useful line and space patterns with low defectivity [1][2][3][4][5][6][7] . In the context of VIA lithography, DSA of PS-PMMA in cylindrical confinement has been successfully implemented to produce PMMA VIA cylinders with a reduced critical dimension (CD) relative to a guiding prepattern [8][9][10][11] .…”

Advanced Formulation for DSA Resists

“…[4] The analysis is typically performed on a set of 20 SEM pictures per system, thus around 15000 cylinders. The software performs a Delaunay triangulation and a Voronoï construction to detect coordinance-based defects (i.e.…”