Design Consideration for Immersion 193: Embedded Barrier Layer and Pattern Collapse Margin

Orientation Control in Thin Films of a High-χ Block Copolymer with a Surface Active Embedded Neutral Layer

“…Our approach to stabilize perpendicular orientations in high-χ BCPs uses a minor formulation additive that is both neutral to the high-χ BCP and able to segregate to and remain anchored at the top of the film during thermal annealing. , This formulation strategy enables perpendicular orientation of high-χ lamellar block copolymers without application of an external top coat and using conventional high temperature thermal annealing, thus simplifying the process and providing potential for high throughput track compatible manufacturing. The approach was inspired by Dow’s “embedded barrier layer” technology, − which utilizes a surface active additive to segregate to the top of a photoresist film providing a barrier against leaching of resist components into the immersion fluid during exposure and to modulate surface energy for the immersion process. The embedded barrier materials are minor additives in resist formulations that migrate to the top of the film during spin coating and act as a small molecule diffusion barrier layer on top of the resist.…”

“…We initially removed the ENL with RIE before staining, but we later found the Pt-stain could effectively penetrate the ENL layer to decorate the P2VP domains and impart etch resistance . The observation that the stain can penetrate through the ENL in this system is particularly noteworthy; in photoresists for 193 nm immersion lithography, one of the main functions of the embedded barrier layer is to create a protective barrier that prevents leaching of resist components into the immersion fluid (water). − Without the ENL, an island/hole morphology was observed, suggesting alignment parallel to the substrate (Figure a). However, when the ENL was present in the formulation, the desired perpendicular orientation was achieved.…”

Tailoring the Attraction of Polymers toward Surfaces

“…This effect is controlled by a combination of enthalpic and entropic driving forces, and it can be leveraged to engineer desired properties or functions at a surface. For example, surface-active polymer additives are used to control interactions with a surrounding medium, − thereby decoupling attributes such as adhesive strength and wettability from the bulk polymer properties. Furthermore, a balance of enthalpic interactions and entropic effects will control the orientation of block copolymer domains near surfaces, − and this knowledge can be used to design new materials for nanoscale patterning and thin film electronics.…”

“…As an example, “low-energy” chain segments based on fluorinated chemistries are strongly attracted to an air surface (Table ). These moieties can enable the design of surface-active polymer additives that resist fouling in marine environments, , provide “neutral” interactions for block copolymer lithography, − and produce barrier layers for immersion lithography . Precisely positioned fluoroalkyl moieties can also induce an end-on chain orientation in polymer semiconductors and bottlebrush polymers, as illustrated in Figure , and drag “high-energy” chain segments toward surfaces. , However, in blends of polymers with similar surface energies and/or complex architectures, the segregation of polymers toward surfaces is strongly influenced by entropic effects.…”

Advances in Patterning Materials for 193 nm Immersion Lithography

“…Low surface energy materials such as organosilicon and fluorine-containing polymers have long been known to segregate to the surface of polymer blends during film formation . To take advantage of this phenomenon, small loadings (∼1−5 wt %) of tailored surface-active materials have been used to convert conventional 193 nm dry photoresists into immersion-compatible versions. ,− During spin-casting of the photoresist, these additives segregate to the resist surface to form a thin enrichment layer of the additive, which serves as an in situ topcoat barrier to reduce PAG leaching and control the water contact angles of the resist. These additives are sometimes also referred to as embedded barrier layers (EBLs) or water shedding agents (WSAs) .…”