High interaction parameter block copolymers for advanced lithography

textBlock copolymers demonstrate potential in next-generation lithography as a solution for overcoming the limitations of conventional lithographic techniques. Ideal block copolymer materials for this application can be synthesized on a commercial scale, have high [chi]-parameters promoting self-assembly into sub-20 nm pitch domains, have controllable alignment and orientation, and have high etch contrast between the domains for facilitating pattern transfer into the underlying substrate. Block copolymers that contain silicon in one domain are attractive for nanopatterning since they often fulfill at least three of these requirements. However, silicon-containing materials are notoriously difficult to orient in thin films due to the low surface energy of the silicon-containing block, which typically wets the free surface interface. In this work, the methodology behind material choice and the synthesis of new silicon-containing block copolymers by a variety of polymerization techniques will be described. Thin film self-assembly of the block copolymers with domains oriented perpendicular to the plane of the substrate is achieved using different solvent annealing and neutral surface treatments with thermal annealing conditions. Block copolymer patterns are transferred to the underlying substrate by reactive ion etching and directed self-assembly of the polymers is demonstrated using chemical contrast patterns. Interesting thermodynamics governing the self-assembly of block copolymers with solvent annealing will also be discussed. Finally, new amphiphilic block copolymers will be described that were created with lithographic applications in mind but that are most useful for biological applications in drug delivery.Chemical Engineerin

Anhydride copolymer top coats for orientation control of thin film block copolymers

The concepts described herein involve the use of random copolymer top coats that can be spin coated onto block copolymer thin films and used to control the interfacial energy of the top coat-block copolymer interface. The top coats are soluble in aqueous weak base and can change surface energy once they are deposited onto the block copolymer thin film. The use of self-assembled block copolymers to produce advanced lithographic patterns relies on their orientation control in thin films. Top coats potentially allow for the facile orientation control of block copolymers which would otherwise be quite challenging.Board of Regents, University of Texas Syste

Thin film block copolymer assembly in mixtures of highly selective solvents

Perpendicular orientation of block copolymer (BCP) domains in thin films is generally preferred over parallel orientation for lithographic applications. [1] Thermal annealing can be used to promote this orientation, but often requires a top coat since one block will typically wet the air interface. [2] Solvent annealing is an attractive alternative for achieving perpendicular orientation of the domains by neutralizing the surface energy of the air interface. Many examples of using solvent annealing in BCP thin films exist in the literature, involving domain non-selective [3] and selective [4] solvents. Silicon-containing polymers are desirable for lithographic applications because their high chi-parameters and high etch selectivity allow them to self-assemble into small domains and be transferred easily into an underlying substrate by oxygen etching. [5,6] This paper describes the process used to solvent anneal a new silicon-containing polymer, poly(trimethylsilyl styrene-b-lactide) (PTMSS-b-PLA) using cyclohexane vapor, a solvent that preferentially swells the PTMSS domain.Chemical Engineerin

Polylactide/silicon-containing block copolymers for nanolithography

A diblock copolymer system that self-assembles at very low molecular weights to form very small features is described. One polymer in the block copolymer contains silicon, and the other polymer is a polylactide. The block copolymer may be synthesized by a combination of anionic and ring opening polymerization reactions. This block copolymer may form nanoporous materials that can be used as etch masks in lithographic patterning.Board of Regents, University of Texas Syste

Polylactide/silicon-containing block copolymers for nanolithography

The present invention includes a diblock copolymer system that self-assembles at very low molecular weights to form very small features. In one embodiment, one polymer in the block copolymer contains silicon, and the other polymer is a polylactide. In one embodiment, the block copolymer is synthesized by a combination of anionic and ring opening polymerization reactions. In one embodiment, the purpose of this block copolymer is to form nanoporous materials that can be used as etch masks in lithographic patterning.Board of Regents, University of Texas Syste

Anhydride copolymer top coats for orientation control of thin film block copolymers

The use of self-assembled block copolymer structures to produce advanced lithographic patterns relies on control of the orientation of these structures in thin films. In particular, orientation of cylinders and lamellae perpendicular to the plane of the block copolymer film is required for most applications. The preferred method to achieve orientation is by heating. The present invention involves the use of polarity-switching top coats to control block copolymer thin film orientation by heating. The top coats can be spin coated onto block copolymer thin films from polar casting solvents and they change composition upon thermal annealing to become “neutral”. Top coats allow for the facile orientation control of block copolymers which would otherwise not be possible by heating alone.Board of Regents, University of Texas Syste

Block copolymer orientation control using a top-coat surface treatment

Directed self-assembly of Si containing block copolymers (BCP) is a candidate for next generation patterning technology because it enables both high resolution and high etch contrast. Achieving high resolution requires a high x parameter. However, it is often difficult to achieve perpendicular patterns by thermal annealing of BCPs with a lower surface energy block, which tends to align with the air interface. New top surface treatment materials that provide a surface energy between those of the blocks have been developed that enable perpendicular pattern alignment with block copolymers that have a low surface energy block.Chemical Engineerin

Self-Assembly and Directed Assembly of Polymer Grafted Nanocrystals via Solvent Annealing

Polymer grafted nanocrystals (PGNCs) incarnate a duality of powerful attributes: their inorganic crystal cores hold promise to design nanocrystal solids from superlattice assemblies while their polymeric ligands exhibit the soft colloidal properties of star polymers. From their star polymer analogues, PGNC derive two important, yet sometimes less-exploited attributes: (1) swollen PGNCs are mobile and can be solvent annealed toward thermodynamic equilibrium, and (2) in the semidiluted regime in good solvents, PGNCs display a richer phase diagram compared to that of hard-sphere colloids which can be accessed by controlling the solvent intake during solvent annealing. Here we study the self-assembly of ∼4 nm Fe₃O₄ nanocrystals capped with polystyrene ligands under solvent annealing. We confirm swelling behavior and even a phase transition to a hexatic phase, in agreement with models for star polymers. We exploit the polymeric properties of the PGNCs to perform directed self-assembly using thinly textured patterns to achieve long-range orientational order of the superstructure. We also demonstrate the use of the superlattice assembly as a lithographic mask for pattern transfer with a full pitch of 9.5 nm

Synthesis of Amphiphilic Naturally-Derived Oligosaccharide-<i>block</i>-Wax Oligomers and Their Self-Assembly

Self-assembly characteristics of amphiphilic macromolecules into micelles, nanoparticles and vesicles has been of fundamental interest for many applications including designed nanoscale therapeutic delivery systems and enzymatic reactors. In this work, a class of amphiphilic block oligomers was synthesized from naturally occurring oligosaccharides and aliphatic alcohol precursors, which are all currently prominent in the pharmaceutical, food, and supplement industries. These block oligomer materials were synthesized by functionalization of the precursor materials followed by subsequent coupling by azide–alkyne cycloaddition and their bulk self-assembly was investigated after solvent vapor annealing. Self-assembly of the amphiphilic materials into liposomes in aqueous solution was also investigated after preparing solutions using a nanoprecipitation method. Encapsulation of hydrophobic components was demonstrated and verified using dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy experiments