Remediation of Line Edge Roughness in Chemical Nanopatterns by the Directed Assembly of Overlying Block Copolymer Films

Abstract

Block copolymer structures have been directed to assemble on chemically patterned surfaces with the domain interfaces oriented perpendicular to the substrate. Such methods have been pursued for lithographic applications to achieve long-range order in the assembled structures and, potentially more important, provide nanometer-level control over the interfaces between structures. The chemically striped surfaces used for the directed assembly of lamellae are patterned by top-down lithographic techniques and thus often have rough edges between the regions of different chemistry. Here we quantitatively characterize, using experiments and molecular-level simulations, the propagation of line edge roughness from the chemically patterned surfaces into the interfaces between domains of block copolymer lamellae as a function of the wavelength, amplitude, and geometry of the roughness. Two geometries of surface pattern roughness are considered with oscillatory neighboring interfaces that are either in-phase or out-of-phase. Block copolymer lamellae of poly(styrene-block-methyl methacrylate) effectively self-corrected surface patterns with small wavelength in-phase and out-of-phase roughness such that little or no memory of the substrate pattern roughness could be observed at the top surface of a 40 nm thin film. Larger wavelength in-phase roughness, and to a lesser extent larger wavelength out-of-phase roughness, propagated farther from the surface pattern such that the domain interfaces between block copolymer lamellae maintained the roughness throughout the film. These self-healing capabilities of block copolymers will be essential for lithographic applications with tight tolerances on line edge roughness and line width control, e.g., in patterning transistor gates.

Kinetics of directed self-assembly of block copolymers on chemically patterned substrates

“…If the lines and spaces of the L/S guiding pattern coincide with the period L 0 of the lamellar structure of the block copolymers in the bulk and if both blocks have similar affinity to the free surface of the film, the copolymer will replicate the L/S guiding pattern and form standing lamellae orientated perpendicular to the film surfaces [8,9,10]. The stripe structure of the block copolymer mitigates the line-edge roughness [11,12] or small imperfections of the guiding pattern. Alternatively the periodicity of the L/S guiding pattern can be a small multiple of the bulk lamellar structure of the copolymer ("density multiplication" [13,14,15]).…”

Integration of block-copolymer with nano-imprint lithography : pushing the boundaries of emerging nano-patterning technology.

“…Chemically-directed BCP lithography can guide polymer self-assembly into large area, nearly defect-free patterns with 5-50nm dimensions, and can multiply the feature density while improving the pattern quality by reducing the CD variability and LER. [4][5][6] Currently, slow and expensive e-beam or extreme ultraviolet (EUV) lithography is used to form sub-100nm chemical pre-patterns for directing BCP assembly. We use relatively inexpensive immersion 193nm optical interference lithography (IL) to pre-pattern substrates for directed BCP assembly over large areas where aggressive periodic nanoscale features are required.…”

Modeling Chemoepitaxy of Block Copolymer Thin Films using Self-Consistent Field Theory

“…In the past decade, there have been a large number of papers and reviews discussing the advantages and shortcomings of chemoepitaxy. As discussed by multiple authors, [12,[17][18][19][20][21][22] the ability of the chemical pattern to form a defect-free array of vertical lamellae depends crucially on the width of the guiding stripe, w, the chemistry of the brush, film thickness, and the line multiplication factor. Because of the complexity of the system, it is very difficult to map out a universal "phase diagram".…”