AVS 51st International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA4
Electron Impact Reactions of DVS-BCB Monomer in He Plasma for Low-k Film Deposition

Tuesday, November 16, 2004, 2:20 pm, Room 213B

Session: Plasma and Polymers
Presenter: K. KINOSHITA, Mirai, Japan
Authors: K. KINOSHITA, Mirai, Japan
M. SHIMOYAMA, Mirai, Japan
A. NAKANO, Mirai, Japan
J. KAWAHARA, Mirai, Japan
N. KUNIMI, Mirai, Japan
T. KIKKAWA, Mirai, Japan
Correspondent: Click to Email
DVS-BCB (divinylsiloxane-bis-benzocyclobutene) is known as a precursor of a spin-on low-k material with the dielectric constant of 2.7@footnote 1@. Plasma polymerization process has also been developed to deposit DVS-BCB film from the monomer@footnote 2@. Higher thermal stability (400 °C) and very thin (<20 nm) conformal film formation have been achieved by this vapor phase deposition technique. However, reactions of DVS-BCB in the plasma remain unclear. Recently, in-situ quadrupole mass spectrometry (QMS) study of this plasma showed that there were two types of unique reactions which had never been observed in the thermal polymerization process@footnote 3@. These were hydrogen attachment to and methyl group desorption from the DVS-BCB, resulting in different polymer structures from those of thermally polymerized films. This paper reports molecular orbital calculations for these reactions. Total MO energy calculated by the density functional technique with the 6-31G* basis set clearly showed that both the neutral DVS-BCB and ionized DVS-BCB were stabilized by the hydrogen attachment. The attachment energies are about 2 eV and 4 eV for neutral and ionized species, respectively. The methyl group desorption was also analyzed by changing the Si-CH@sub 3@ distance. When the Si-CH@sub 3@ distance d was stretched from the stable position (d=1.88 Å), there appeared two types of saddle point structures at d=2.38 - 3.88 Å before final dissociation. The total MO energy at this final condition showed a lower value than the transition state. This means, methyl group desorption reaction needs activation to proceeds. The MO calculations well explain the QMS observations. This work was supported by NEDO. @FootnoteText@ @footnote 1@ T. M. Stokich, Jr., et al.: Mat. Res. Soc. Symp. Proc., 227, (1991) 103.@footnote 2@ J. Kawahara, et al., Technical Dig. IEDM 2003, 6-2-1, (2003) 143.@footnote 3@ K. Kinoshita, et al., Proc. Dry Process Symp. 2003, 6-6, (2003) 157.