Research

The following are some brief overviews of current research project topics in the Henderson Research Group.  If you clink on the hyperlink title of one of the research areas, it will take you to a page with additional information on the topic.
1. Design, Synthesis, and Characterization of Block Copolymers for Directed Self Assembly (DSA) - As
    feature sizes have continued to shrink in integrated circuit manufacturing, current 193 nm optical lithography
    methods have reached the limits of their capabilities in terms of single layer resist patterning at a pattern pitch
    of ~80nm. To achieve smaller pitches, various multiple patterning schemes are being employed.  To progress
    below 40 nm pitch features, alternative methods are needed.  Directed self assembly (DSA) of block
    copolymers is one promising alternative for patterning pitches smaller than 40 nm.  In such DSA techniques,
    one takes advantage of the general fact that most polymers are phase immiscible with one another, and thus
    block copolymers have a natural tendency to microphase separate on a length scale that is commensurate with
    the polymer block dimensions.  Thus, pattern pitch in features made by DSA can be controlled by controlling
    the size of the block copolymers (i.e. by controlling the polymers degree of polymerization).  Our work in this
    area is directed at developing high chi block copolymers that can achieve very small pattern pitches and
    developing the materials and processes needed to achieve directed assembly of such block copolymers into
    useful nanostructures.         
 
2. Modeling and Simulation of Block Copolymer Phase Separation and Directed Self Assembly - In support
    of our DSA work mentioned above, we are also developing techniques and models to simulate the phase
    separation process in block copolymer systems, with a particular emphasis on studying the directed assembly
    process in thin block copolymer films.  Our group, in collaboration with Professor Pete Ludovice (GT ChBE), are
    developing new techniques for performing fast annealing of copolymers in molecular dynamics simulations in
    order to access the large time and length scales needed in the simulations to probe questions of interest in
    DSA.  For example, for a given block copolymer system, what is the expected defect level in such a process?
    What is the ideal guiding layer material for a given block copolymer? What is the scaling of phase separated
    pattern pitch with block copolymer characteristics (e.g. degree of polymerization and chi)?  We are utilizing
    our custom GPU computing cluster to perform simulations with effectively millions to tens of millions of atoms
    on fast time scales (e.g. 7 million effective atom block copolymer phase separation simulation completed in <12
    hours).
 
3. Pattern Collapse in Polymeric and Photoresist Nanostructures - The semiconductor industry has continued
    its drive for smaller feature sizes, as typically described by Moore's Law, in integrated circuits devices now for
    roughly 50 years using essentially the same type of lithographic process which involves ultraviolet exposure of
    a polymeric resist followed by a wet "development" of the resist image in either an organic solvent or aqueous
    alkaline solution. same types of basic photoresist technology.  As feature sizes have now reached below the 50
    nm size scale, the collapse of those resist features as a result of the capillary forces experience by the features
    during drying following wet development has become a major problem and possible limiter for future reductions
    in feature size.  Our work in this area has focused on three main issues: (1) characterizing and understanding   
    the mechanical behavior of polymeric nanostructures such as those formed during high resolution lithography,
    (2) developing methods and models to perform such physical property measurements on nanoscale structures,
    and (3) developing materials and methods to help prevent such pattern collapse via methods that are
    compatible with standard integrated circuit manufacturing processes.

4. Synthesis and Characterization of Graphene and Graphene-based Electronic Devices - Graphene is an
    exciting material which is nominally a single sheet of carbon atoms arranged into an sp2 hybridized graphite
    lattice.  Graphene has a variety of unique properties including extremely large very high carrier mobility (i.e. up
    to possibly 200,000 cm2/Vs) and large mechanical strength.  Graphene is of particular interest as a possible
    replacement for current transparent conductors such as ITO (indium tin oxide) and as a replacement
    semiconductor for silicon in high speed electronic circuits.  Our work in this area is focused on several issues
    including: (1) developing low temperature routes to the synthesis of graphene films and nanostructures based
    on directed synthesis techniques, (2) developing methods for opening a bandgap in graphene and controllably
    doping the material, and (3) developing silicon compatible processing schemes whereby graphene devices can
    be integrated with current CMOS technology.  

5. Fundamental Studies of the Physicochemical Behavior of Polymer Ultra-thin Films - The observed
    physical properties of polymers changes dramatically when they are confined into ultra-thin film form.  For
    example, a decrease in the diffusion coefficient of molecules within the polymer film of several orders of
    magnitude as compared to bulk properties can be observed in sub-100 nm thick films.  Our work in this area is
    focused on characterizing the physical properties of such ultra-thin polymer films, developing an understanding
    of the origins of such proprty changes, and exploiting these properties in a variety of applications ranging from
    semiconductor manufacturing to fuel cells.

 
6. Development of Methods and Materials for 3-D Stereolithography - Stereolithography refers to processes
    in which 3-D objects are made directly from electronic CAD design data.  One common method for achieving
    this is through the build-up of such objects via the layer-by-layer photopolymerization of reactive monomers to
    form solid cross-linked polymer objects.  Our work in this area focuses on both developing new
    stereolithographic methods and tools based on projection imaging systems and the development of new
    materials for use in stereolithography to build functional objects for applications such as tissue engineering. 
 

7. Modeling of Polymerization and Photopolymerization Kinetics - In order to control such processes and
    design improved materials and methods, a better understanding of and modeling capability for the
    photopolymerization processes involved is needed. Our work in this area focuses on characterizing the kinetics
    and behavior of such photopolymerization processes and developing predictive models of such processes
    based on this characterization data. We utilize a combination of experimental measurements (e.g. real-time
    FTIR kinetics measurements, photo-DSC, etc.) and molecular and monte carlo modeling techniques to
    accomplish these goals.