AVS 57th International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF-MoA

Paper TF-MoA2
Molecular Layer Deposition of Hybrid Siloxane/Alumina Polymer Films

Monday, October 18, 2010, 2:20 pm, Room Pecos

Session: Organic ALD
Presenter: A.I. Abdulagatov, University of Colorado at Boulder
Authors: A.I. Abdulagatov, University of Colorado at Boulder
B. Yoon, University of Colorado at Boulder
V.R. Anderson, University of Colorado at Boulder
Z.M. Gibbs, University of Colorado at Boulder
A.S. Cavanagh, University of Colorado at Boulder
S.M. George, University of Colorado at Boulder
Correspondent: Click to Email
Polydimethylsiloxane (PDMS) is an important polymer with excellent flexibility and low elastic modulus. The properties of PDMS are also tunable based on varying the cross-linking between the polymer chains. PDMS MLD was initially attempted using the sequential dosing of bis(dimethylamino)dimethylsilane or dimethylmethoxychlorosilane (DMMCS) and water at different temperatures. Unfortunately, the surface reactions appeared to terminate and no mass gain was measured after about 20 MLD cycles. After precursor dosing was stopped, the deposited film was observed to decrease in mass. This loss of mass is believed to be related to desorption of cyclic siloxanes from the PDMS MLD film. Cyclic siloxane desorption is entropically favored at longer PDMS chain lengths and higher temperatures and is facilitated by the high flexibility of the PDMS chains. To prevent desorption of the cyclic siloxanes, hybrid siloxane/alumina films were grown by mixing aluminum into the siloxane film using trimethylaluminum (TMA). The new hybrid MLD films contain [-Si(CH3)2-O-] units that are separated by [-Al-O-] linkages. The hybrid siloxane/alumina polymer films were grown using the precursor sequence: DMMCS; H2O, TMA; and H2O. Quartz crystal microbalance studies revealed linear growth with growth rates of ~22 ng/cm2 at 200°C. FTIR vibrational studies revealed -Si(CH3)2OCH3, -Si(CH3)2OH, - AlCH3, and –AlOH surface species after the DMMCS; H2O, TMA; and H2O exposures, respectively. FTIR studies also observed self-limiting adsorption during the individual precursor exposures. X-ray reflectivity (XRR) measurements revealed a hybrid siloxane/alumina growth rate of ~1.0 Å/cycle at 200°C and a film density of ~2.3 g/cm3. Elemental analysis of films using X-ray photoelectron spectroscopy (XPS) indicated that the films were chlorine-free. Hybrid siloxane/alumina polymer films could be grown at temperatures as low as 120°C, and these films showed some chlorine impurities.