%0 Journal Article
%A Zhang, Jieqian
%A Clark, Michael B.
%A Wu, Chunyi
%A Li, Mingqi
%A Trefonas, Peter
%A Hustad, Phillip D.
%D 2016
%T Orientation Control in Thin Films of a High‑χ
Block Copolymer with a Surface Active Embedded Neutral Layer
%U https://acs.figshare.com/articles/journal_contribution/Orientation_Control_in_Thin_Films_of_a_High_Block_Copolymer_with_a_Surface_Active_Embedded_Neutral_Layer/2089657
%R 10.1021/acs.nanolett.5b04602.s001
%2 https://acs.figshare.com/ndownloader/files/3722872
%K surface tensions
%K Flory interaction parameter
%K ENL
%K DSA
%K BCP
%K glass transition temperature
%K film
%K surface energy
%K annealing
%X Directed self-assembly (DSA) of block
copolymers (BCPs) is an attractive advanced patterning technology
being considered for future integrated circuit manufacturing. By controlling
interfacial interactions, self-assembled microdomains in thin films
of polystyrene-block-poly(methyl methacrylate), PS-b-PMMA, can be oriented perpendicular to surfaces to form
line/space or hole patterns. However, its relatively weak Flory interaction
parameter, χ, limits its capability to pattern sub-10 nm features.
Many BCPs with higher interaction parameters are capable of forming
smaller features, but these “high-χ” BCPs typically
have an imbalance in surface energy between the respective blocks
that make it difficult to achieve the required perpendicular orientation.
To address this challenge, we devised a polymeric surface active additive
mixed into the BCP solution, referred to as an embedded neutral layer
(ENL), which segregates to the top of the BCP film during casting
and annealing and balances the surface tensions at the top of the
thin film. The additive comprises a second BCP with a “neutral
block” designed to provide matched surface tensions with the
respective polymers of the main BCP and a “surface anchoring
block” with very low surface energy that drives the material
to the air interface during spin-casting and annealing. The surface
anchoring block allows the film to be annealed above the glass transition
temperature of the two materials without intermixing of the two components.
DSA was also demonstrated with this embedded neutral top layer formulation
on a chemical patterned template using a single step coat and simple
thermal annealing. This ENL technology holds promise to enable the
use of high-χ BCPs in advanced patterning applications.
%I ACS Publications