Combining double patterning with self-assembled block copolymer lamellae to fabricate 10.5 nm full-pitch line/space patterns

Directed self-assembly of block copolymers and self-aligned double patterning are two commonly used pitch scaling techniques to increase the density of lithographic features. In this work, both of these pitch scaling techniques were combined, enabling patterning at even higher densities. In this process, directed self-assembly of a high-χ block copolymer was used to form a line/space pattern, which served as a template for mandrels. Via these mandrels, atomic layer deposition was used to deposit a thin aluminium oxide spacer. By this method, a total pitch scaling factor of 8, equivalent to a 10.5 nm full pitch, was reached. The types of defects and the line roughness at the different steps of the process were discussed.

Path to Move Beyond the Resolution Limit with Directed Self-Assembly

Directed self-assembly (DSA) of block copolymers (BCPs) has long been viewed as a powerful alternative to extend the resolution of optical lithography. For full-area patterning applications, despite significant progress, the two most prominent DSA methods (chemoepitaxy and graphoepitaxy) are facing a scalability challenge: the critical dimension (CD) of the guiding patterns will need to be continuously scaled down to closely match the dimension of the BCP microdomain, a task that not only contravenes some of the resolution gains achieved by density multiplication but that will also become particularly difficult below 10 nm. To avoid this conundrum, we propose here a synergistic integration of graphoepitaxy and chemoepitaxy through self-registered self-assembly (SRSA) to enable the simultaneous realization of feature density multiplication and CD shrinkage resolution gains. We report nearly perfect DSA on prepatterns with high density multiplication factors and CD of several multiples of the BCP microdomain size. A prepattern consisting of alternating stripes of a relatively thicker neutral mat and a thinner neutral brush with preferential wetting sidewalls serves as a topographic pattern to guide an ultrathin BCP blend film inside the trenches. As the oriented BCP pattern assembles, the blend film deploys a layer of chemical markers on the bottom surface through SRSA generating 1:1 chemical contrast patterns inside the trenches. After thorough removal of the blend film, the newly formed self-registered chemical patterns interpolated by the remaining neutral mat strips serve as the guiding patterns for a second chemoepitaxial DSA step to achieve full-area, defect-free DSA of thick BCP films.

Self-Registered Self-Assembly of Block Copolymers

Directed self-assembly (DSA) of block copolymer (BCP) thin films, especially with density multiplication, is one of the most promising options for further improving resolution and throughput in nanolithography. However, controlling defect density has been one of the major hurdles for many DSA applications. Both thermodynamically and kinetically, defect-free patterns favor the use of low density multiplication factors and thinner films, which undermine the promise of enhanced resolution and the formation of robust masks for pattern transfer. Here, we demonstrate a self-registered self-assembly method to enable nearly perfect DSA on loosely defined chemical patterns with high density multiplication factor. Self-registered self-assembly involves two DSA steps. In the first step, an ultrathin BCP blend film is used to obtain vanishingly low defect densities. Concurrently as the film is annealed, preloaded chemical markers separate into the different polymer blocks and graft to the substrate locking in a new chemical contrast pattern with 1:1 feature registration. After thorough removal of the blend film, the remaining self-registered chemical pattern can establish defect-free DSA of thick BCP films.

A surface interaction model for self-assembly of block copolymers under soft confinement

The surface interaction between substrates and block copolymers is one of the most important factors that control the alignment of self-assembled domains under thin film confinement. Most previous studies simply modeled substrates modified by grafting polymers as a hard wall with a specified surface energy, leading to an incomplete understanding of the role of grafted polymers. In this study, we propose a general model of surface interactions where the role of grafted polymers is decomposed into two independent contributions: the surface preference and the surface softness. Based on this model, we perform a numerical analysis of the stability competition between perpendicular and parallel lamellae of symmetric diblock copolymers on substrates modified by homopolymers using self-consistent field theory. The effects of the surface preference and the surface softness on the alignment of lamellar domains are carefully examined. A phase diagram of the alignment in the plane of the surface preference parameter and the surface softness parameter is constructed, which reveals a considerable parameter window for preparing stable perpendicular lamellae even on highly preferential substrates.

Rapid ordering of block copolymer thin films

Block-copolymers self-assemble into diverse morphologies, where nanoscale order can be finely tuned via block architecture and processing conditions. However, the ultimate usage of these materials in real-world applications may be hampered by the extremely long thermal annealing times-hours or days-required to achieve good order. Here, we provide an overview of the fundamentals of block-copolymer self-assembly kinetics, and review the techniques that have been demonstrated to influence, and enhance, these ordering kinetics. We discuss the inherent tradeoffs between oven annealing, solvent annealing, microwave annealing, zone annealing, and other directed self-assembly methods; including an assessment of spatial and temporal characteristics. We also review both real-space and reciprocal-space analysis techniques for quantifying order in these systems.

Directed self assembly of block copolymers using chemical patterns with sidewall guiding lines, backfilled with random copolymer brushes

Recently, alignment of block copolymer domains has been achieved using a topographically patterned substrate with a sidewall preferential to one of the blocks. This strategy has been suggested as an option to overcome the patterning resolution challenges facing chemoepitaxy strategies, which utilize chemical stripes with a width of about half the period of block copolymer to orient the equilibrium morphologies. In this work, single chain in mean field simulation methodology was used to study the self assembly of symmetric block copolymers on topographically patterned substrates with sidewall interactions. Random copolymer brushes grafted to the background region (space between patterns) were modeled explicitly. The effects of changes in pattern width, film thicknesses and strength of sidewall interaction on the resulting morphologies were examined and the conditions which led to perpendicular morphologies required for lithographic applications were identified. A number of density multiplication schemes were studied in order to gauge the efficiency with which the sidewall pattern can guide the self assembly of block copolymers. The results indicate that such a patterning technique can potentially utilize pattern widths of the order of one-two times the period of block copolymer and still be able to guide ordering of the block copolymer domains up to 8X density multiplication.