AVS 50th International Symposium
    Processing at the Nanoscale Tuesday Sessions
       Session NS+MI-TuA

Paper NS+MI-TuA8
Polymer Patterning using a Soft Inkpad

Tuesday, November 4, 2003, 4:20 pm, Room 308

Session: Nanoscale Patterning and Lithography
Presenter: Y.P. Kong, Institute of Materials Research and Engineering, Singapore
Authors: Y.P. Kong, Institute of Materials Research and Engineering, Singapore
L. Tan, University of Michigan, Ann Arbor
L.-R. Bao, University of Michigan, Ann Arbor
X.D. Huang, Institute of Materials Research and Engineering, Singapore
S.W. Pang, University of Michigan, Ann Arbor
A.F. Yee, Institute of Materials Research and Engineering, Singapore
Correspondent: Click to Email
We present a method of producing micrometer and submicrometer patterns of polymer on substrates. A patterned hard mold is pressed onto an 'inkpad' coated by a polymer. The inkpad consists of a polydimethylsiloxane (PDMS) layer backed by a hard substrate. The function of the PDMS layer is twofold. Oxygen plasma treatment of the PDMS layer allows a polar polymer solution to be spun coated on it. The hydrophobic recovery of the PDMS layer then lowers its surface energy and this allows the transfer of the polymer to the hard mold that has a higher surface energy. Secondly, the deformation of the PDMS layer during the pressing induces a large stress field gradient at the edges of the mold protrusions. It is this stress that leads to a localized rupture of the polymer layer. The pressing is carried out at temperatures close to the glass transition temperature of the polymer and under relatively low pressures to transfer the polymer onto the protrusions of the hard mold. After the hard mold is separated from the inkpad, it is brought into contact with a substrate under a suitable temperature and pressure to produce a positive replica of the mold. At the same time, a negative image of the mold is left on the inkpad and this negative pattern can be transferred to a substrate. With a 700 nm period silicon grating mold, we are able to produce both positive and negative polymeric gratings. We also demonstrate the transfer of multiple layers of polymer onto the protrusions of the mold thereby increasing the aspect ratio of the patterns. Transferring of different polymer layers leads to the possibility of making high-resolution polymer light emitting displays and organic circuits. The advantages of our patterning method over nanoimprint lithography are: lower process temperatures and pressures, no material transport related problems, absence of a residual layer that needs removal, and the possibility to create both negative and positive replicas of the mold.