!!Large-area submicron replica molding of porous low-k dielectric films and application to photonic.pdf

/locate/mee Microelectronic Engineering 84 (2007) 603–608Large-area submicron replica molding of porous low-k dielectric films and application to photonic crystal biosensor fabrication Ian D. Block, Leo L. Chan, Brian T. Cunningham * Nano Sensors Group, University of Illinois at Urbana-Champaign, 208 N. Wright St, Urbana, IL 61801, USA Received 13 February 2006; received in revised form 14 December 2006; accepted 14 December 2006 Available online 16 January 2007Abstract We demonstrate a replica-molding method for submicron patterning of a low-index sol–gel nanoporous glass for the purpose of fab- ricating large-area (80 cm2) label-free photonic crystal optical biosensors. Scanning electron micrographs show the sol–gel exhibited minimal shrinkage and good substrate adhesion and depict precise and uniform pattern transfer over the fabricated area within the limits of measurement resolution. A unique characterization approach is described in which the photonic crystal optical resonance is used to accurately and quickly characterize the geometrical and material property uniformity over a large area. Uniformity within 1% was mea- sured over an 80 cm2 area. We suggest that this robust method is an excellent approach for photonic crystal sensor fabrication, and may also find applications in integrated optics and electronics.  2006 Elsevier B.V. All rights reserved. Keywords: Low-k; Replica molding; Optical biosensor; Sol–gel glass1. Introduction Imprint lithography and nanoreplication methods are emerging as important techniques for imparting submicron features to a wide array of devices. In comparison to pho- tolithography, and to a greater extent e-beam lithography, these methods provide higher throughput, lower cost, decreased processing complexity and equipment require- ments, and the ability to directly pattern a large variety of materials [1]. This approach has previously been used to successfully mold sol–gel glass precursors into diffractive optical elements, len