Nanoporous Organosilicate Films Prepared in Acidic Conditions Using Tetraalkylammonium Bromide Porogens

Authors

  • Salvador Eslava,

    1. Interuniversitary MicroElectronic Center (IMEC) Kapeldreef 75, 3001 Leuven (Belgium)
    2. Centrum voor Oppervlaktechemie en Katalyse Katholieke Universiteit Leuven Kasteelpark Arenberg 23, 3001 Leuven (Belgium)
    Search for more papers by this author
  • Mikhail R. Baklanov,

    Corresponding author
    1. Interuniversitary MicroElectronic Center (IMEC) Kapeldreef 75, 3001 Leuven (Belgium)
    • Interuniversitary MicroElectronic Center (IMEC) Kapeldreef 75, 3001 Leuven (Belgium).
    Search for more papers by this author
  • Jone Urrutia,

    1. Interuniversitary MicroElectronic Center (IMEC) Kapeldreef 75, 3001 Leuven (Belgium)
    Search for more papers by this author
  • Christine E. A. Kirschhock,

    1. Centrum voor Oppervlaktechemie en Katalyse Katholieke Universiteit Leuven Kasteelpark Arenberg 23, 3001 Leuven (Belgium)
    Search for more papers by this author
  • Karen Maex,

    1. Interuniversitary MicroElectronic Center (IMEC) Kapeldreef 75, 3001 Leuven (Belgium)
    2. Department of Electrical Engineering (ESAT-INSYS) Katholieke Universiteit Leuven Kasteelpark Arenberg 10, 3001 Leuven (Belgium)
    Search for more papers by this author
  • Johan A. Martens

    Corresponding author
    1. Centrum voor Oppervlaktechemie en Katalyse Katholieke Universiteit Leuven Kasteelpark Arenberg 23, 3001 Leuven (Belgium)
    • Centrum voor Oppervlaktechemie en Katalyse Katholieke Universiteit Leuven Kasteelpark Arenberg 23, 3001 Leuven (Belgium).
    Search for more papers by this author

  • We would like to acknowledge Dr. Francesca Iacopi for scientific discussions. CEAK and JAM acknowledge the Flemish government for a concerted research action (GOA). SE acknowledges Santiago Esconjauregui. Supporting Information is available online from Wiley InterScience or from the author.

Abstract

Organosilicate films with narrow pore size distribution tunable in the range of 1–3.4 nm were prepared by spin-coating of silicon wafers with sols prepared in acidic conditions using tetraethyl orthosilicate, methyltrimethoxysilane, and tetraalkylammonium bromide (TAABr) porogen. The pore size was defined by the alkyl chain length of the quaternary ammonium molecule and the porogen concentration. The pore network in the films and the hydrophobicity of the pore surfaces were characterized using ellipsometric porosimetry with toluene and water adsorbates. In the absence of TAABr, the pore volume was 9 vol% and the pore size 1 nm. By using TAABr porogens, monomodal pore size distributions were obtained in the range of 1.2–3.5 nm. The pore volume was in the range from 18 vol% at 1.2 nm pore diameter up to 54 vol% at 3.5 nm diameter. The hydrophobicity of the pores was dependent on the pore diameter, with smaller pores being the least hydrophobic. The increase of hydrophobicity with pore size was explained by an increased distance between silanol groups on the curved pore surfaces. The mechanical properties and dielectric constant of these films were comparable to reference materials prepared using more sophisticated porogens reported in the literature.

Ancillary