Real-Time FT-IR Studies Of The Reaction Kinetics For The Polymerization Of Divinyl Siloxane Bis-Benzocyclobutene Monomers

Abstract

The thermal polymerization reaction of divinyl siloxane bis-benzocyclobutene (DVS bis-BCB) was monitored in-situ with FT-IR spectroscopy in order to follow specific chemical changes and determine the reaction order and rate constants at temperatures from 150° to 210°C. FT-IR spectra were obtained at regular intervals throughout the reaction with a Nicolet 170SX spectrophotometer.Monomeric DVS bis-BCB contains mixed stereo and positional isomers of 1,3- bis(2-bicyclo[4.2.0]octa-1, 3, 5-trien-3-ylethenyl)-1, 1, 3, 3-tetramethyl disiloxane (CAS 117732-87-3). It polymerizes via Diels-Alder cycloaddition reactions between vinyl groups and an intermediate o-quinodimethane formed by first-order, thermally initiated ring openings of the benzocyclobutene rings. Gaseous byproducts are not produced; therefore, the cure is easier to manage than are cures for polyimides which evolve water in polycondensation reactions. The DVS bis-BCB has four reactive elements per monomer unit and, thus, polymerizes into a very highly cross linked and solvent resistant network.With the FT-IR methodology, the reaction was easily monitored through the points of gel formation and vitrification. With the exception of DSC (i.e., calorimetry) which does not sense specific chemistry, other methods were not successful in following the reaction after a gel was formed. We have found that the polymerization was first-order until vitrification occurs; the gelation alone had no apparent effect on the reaction rate.DVS bis-BCB is under development at Dow as high performance dielectric material for multilayer interconnect coating applications for the microelectronics industry. Methodology reported here is employed in developing effective cure management strategies.

Characterization of low‐k benzocyclobutene dielectric thin film

“…The activation energy (E a ) can be calculated from the expression (Ozawa, 1970): where f is the heating rate (8C/min), T is the absolute temperature, R is the gas constant and E a is the activation energy. The activation energy obtained in this study is quite close to the reported value of 36:0^0:9 kcal=mol or 150.7 kJ/mol from real-time FTIR reaction kinetics study (Stokich et al, 1991). Hence, degree of cure predicted by both FTIR and DSC methods should give close correlation.…”

“…By quantifying the growth or depletion of these peaks, the extent of cure can be determined. A strong absorption at 1,254 cm 2 1 associated with the rocking mode of the methyl groups attached to the silicon atoms can be used for normalization since these bonds are nearly unaffected by the polymerization (Dow, 1995;Stokich et al, 1991). It has been reported that all FTIR transmission measurements for BCB should be done at Brewster's angle to eliminate interference fringes.…”

Adhesion of benzocyclobutene-passivated silicon in epoxy layered structures

“…The effects of cure temperature and time have been extensively characterized for BCB resins. 26 The polymerization of BCB proceeds through a two-step thermally activated process with an o-quinodimethane intermediate. 27 The polymerization follows first-order reaction kinetics with an activation energy of 150 kJ/mol.…”

Polymerization of Thin Film Polymers

“…The discrete IR wavelength gets into resonance with the rotation or vibration of some molecule groups. The rate of reactants and products of the polymerization could be estimated by the peak height [15]. The samples were measured before and after the curing by the "FT-IR 2000 System" from Perkin-Elmer.…”