High-Resolution Direct-Write Multiphoton Photolithography in Electronic Polymers
Reference Number: 07-21
Inventor: Daniel Higgins and Takashi Ito
Background:
Due to the limitations of commonly used photo-resist-based lithographic methods, researchers have long sought alternative procedures that can produce high resolution patterns without the use of photomasks and chemical developers. An important additional challenge has been in the creation of grayscale (three-dimensional) surface relief structures.
The present invention pertains to a new laser-based ablative method for fabricating high-resolution binary and grayscale structures in common commercial insulating and electrically-conducting polymers. Ablative lithography has been demonstrated previously in many of these materials. These studies frequently employed nanosecond pulsed UV-to-IR light to drive removal of the polymer film. None demonstrated high-resolution lithography, instead depicting structures tens of micrometers across, with depth resolution on the order of the wavelength of light employed.
High-resolution multiphoton-based photolithography using common photoresist technologies has been demonstrated using different polymers in other reports. These studies also demonstrated that three-dimensional structures could be fabricated. Unfortunately, common positive-tone resists are gradually “exposed” if used in the presence of light and may delaminate from the substrate surface when immersed under liquids (i.e. water).
Advantages:
Advantages of this IP over previous methods:
- Grayscale patterning with 1-2 nm depth resolution has been achieved
- High-Resolution binary patterns have been prepared
- Etching technique can be applied to commonly-used commercial polymers
- Etching process does not require use of photomasks or chemical developers
- Etching is driven by irradiation with femtosecond pulses at near-infrared wavelengths
Applications
This innovative technology can be used to:
- Fabricate arrays of microelectrodes and microelectronic circuits for use in chemical sensors, biosensors and biochips
- Fabricate molds having submicron-scale features
- Construct Micro/nanofluidic devices
- Pattern organic electronic circuit components
- Prepare arbitrary grayscale (three-dimensional) computer-generated surface-relief patterns, without any additional development steps and without use of a photomask
Patent Status
- Provisional patent application filed in July 2007.
Above are demonstrating high-resolution direct-write lithography in a poly(methylmethacrylate) thin film. Edge sharpnesses on the order of 120 nm are obtained, demonstrating unprecidented resolution for applications employing near-infrared light.
Above are images demonstrating controlled grayscale patterning of a conducting polymer thin film. A) depicts a grayscale template (pyramid) used to generate the patterns, while B)-D) depict the patterns produced in the film. Line profiles across these patterns are shown in the lower left plots, demonstrating 1 nm depth resolution at low powers. A different grayscale pattern is depicted in the lower right image, exhibiting 2 nm depth resolution.
Above are data from a polymer/liquid-crystal diffraction grating prepared using the aforementioned multiphoton lithographic method. Polymeric channels having a 2 µm pitch and 250 nm depths are shown. When filled with a nematic liquid crystal, and sandwiched between optically transparent electrodes, electrically switchable diffraction gratings are obtained.
Microelectrodes consisting of a transparent indium tin oxide electrode coated with a transparent polymer thin film (upper) and molds for PMMA soft lithography (below) can be fabricated using this technology. This technology can be used to fabricate arrays of microelectrodes having arbitrary structures. In addition, patterns having 50 nm depths can be easily transferred from the mold to a PDMS monolith.
Kansas State University Research Foundation seeks to have discussions with companies that are interested in licensing and/or research collaborations.
Interested parties should contact:
National Institute for Strategic Technology Acquisition and
Commercialization (NISTAC)
2005 Research Park Circle Manhattan, KS 66502
Tel: 785-532-3900 Fax: 785-532-3909
E-Mail: nistac@ksu.edu