Fluorene arylene copolymers are a class of aromatic macromolecules that have an alternating backbone structure consisting of a 9,9-dialkylfluorene together with one (or more) additional aromatic group(s). Fluorene when combined with chromophoric and/or charge transporting aromatic monomers to form polyfluorenes have received a great deal of attention over the last several years as the emissive layer in polymeric light emitting diodes. The emission of green, red, or blue light can be controlled by the choice of the aryl backbone segments and alkyl side groups in the polymer. More recently, polyfluorenes have been designed and evaluated As the organic semiconducting layer in polymeric field effect transistors (pFETs). This work has led to a class of polymeric semiconductors with an excellent combination of charge mobility, environmental stability, and processability. These polymers have also been shown to have optoelectronic properties. The high optical density, high charge carrier mobility, and the potential to tune the absorption spectra makes this class of materials an ideal candidate for further study in the area of organic photovoltaics. This paper reviews the synthesis and characterization of polyfluorenes, focusing on the optimization of electronic properties for the conversion of light into electric current.

The authors demonstrate the feasibility of rapid thermal curing (RTC) of benzocyclobutene (BCB) thin films using an infrared belt furnace. The effects on film properties resulting from a dramatic reduction in cure time (5 h to 5 min) are summarized. The extent of cure was determined by FTIR (Fourier-transform infrared spectroscopy) and was subsequently modeled as a function of reaction kinetics using the measured temperature profiles. FTIR spectra from the RTC films were identical to those obtained using a conventional inert gas oven and a convectively heated belt furnace, indicating that: (1) the polymerization mechanisms and the resulting polymer network structure are identical, and (2) no chemical enhancement of the curing occurs due to the absorption of infrared radiation. There are no statistically significant differences in the resulting stress and adhesion properties for samples cured by the RTC process vs. the conventional process for film thicknesses ranging from 1 to 24 mu m. Planarization measurements, made on isolated features up to 100 mu m in width, also indicate no differences in the cured films.< >

The stress at room temperature in many typical polymer coatings used for microelectronic dielectrics is near 40 MPa. Polymer coatings derived from divinylsiloxane bisbenzocyclobutene (BCB), (CAS 117732-87-3), have a stress level of ca. 38 MPa after a conventional thermal oven cure. In this work, a novel approach based on curing the BCB polymeric network in the vitrified state has been used to achieve far field stresses of 24 MPa in the final coatings. This represents a 36% reduction in the far field stress of BCB coatings cured at 250 °C. The cure methodology and compatibility with device process design are discussed.

This paper discusses the nonhermetic performance of polymer thin film coatings derived from 1,3-bis(2-bicyclo[4.2.0]octa-1,3,5-trien-3-ylethenyl)-1,1,3,3-tetramethyl disiloxane (mixed isomers, CAS 117732-87-3), known also as divinyl siloxane bis-benzocyclobutene or DVS bis-BCB. The stability of the dielectric constant and the mechanical properties have been examined before and during high temperature exposures of the polymer films to air for extended periods of time at high and low humidity. Infrared absorbance spectra and dielectric constant measurements have been correlated. Formulations of the DVS bis-BCB prepolymer with a polymeric oxidation inhibitor are predicted to yield polymer films which display less than a 10% change in the dielectric constant after 40 years in air at 85°C. These films have excellent potential for use as the dielectric coating layer in nonhermetic packaging applications for Multi Chip Module (MCM) circuits.

An interaction between heat transfer, shrinkage, and stress relaxation during postforming cooling of thermoplastic materials was studied. In order to arrive at a treatable mathematical formulation, while retaining the basic physical effects, the one‐dimensional case was analyzed with the relaxation spectrum approximated by a single relaxation time depending on temperature. An effective relaxation parameter β controlling the postforming behavior was identified. Its dependence upon the relaxation time, rate of heat transfer, and a temperature interval was established. An analytical approximation for a maximal tensile stress was developed. This result enables an understanding of the interaction between cooling conditions and material behavior.