Alvin H. Romang1, Sivakumar Nagarajan2, Joan K. Bosworth3, Christopher K. Ober3, Thomas P. Russell4, and James J. Watkins5. (1) Department of Chemical Engineering, University of Massachusetts-Amherst, 159 Goessman lab, 686 N. Pleasant st, Amherst, MA 01003, (2) University of Massachusetts Amherst, Conte Building, Amherst, MA 01002, (3) Materials Science and Engineering, Cornell University, 214 Bard Hall, Ithaca, NY 14853, (4) University of Massachusetts, Room A516, Conte Research Center, Amherst, MA 01002, (5) Department of Polymer Science and Engineering, University of Massachusetts, 120 Governors Dr., Amherst, MA 01003
Mesoporous metal-oxide films with well defined pore structures, 2-50 nm in size, have been gaining much interest from both the industrial and academic communities for potential applications in microelectronics, sensors, microfluidics and catalysis. For many of these applications, especially in microelectronics, processes that yield control over the local pore architecture, long-range lateral ordering and device level patterning are required for practical implementation.
By combining supercritical CO2 processing and photolithography, we demonstrate an integration of a “bottom-up” approach, the self-assembly of block copolymers with phase selective chemistry, with a classic “top down” approach, photolithographic patterning, for the fabrication of directly patterned mesoporous silica films for use as ultra low k dielectric films for interconnect structures. The mesoporous silica films are synthesized by selectively depositing silica precursors into the hydrophilic domain of sacrificial block copolymer templates, such as poly(tertiary-butoxy carbonyloxy styrene-b-styrene). We extend this technique by incorporating photo-acid generator into the polymer layer and subsequent photolithography to enable silica deposition selectively in the exposed region of the templates and to obtain device-level structures directly without subsequent etching.