Dependence of the dielectric constant on the fluorine content and porosity of polyimides

The trend toward miniaturization in inte- grated circuit fabrication demands good interlayer dielec- tric materials. This need can be met by polyimide (PI), which has extreme thermal and chemical stability and, most importantly, a low dielectric constant. Four porous PIs with symmetrically substituted fluorine contents were synthesized. Different porosity levels were achieved with a sol-gel technique through the incorporation of 10 or 20% tetraethyl orthosilicate into the polymer matrix and then acid etching. Their dielectric constants were correlated with the fluorine contents and porosity levels. High poros- ity levels and higher fluorine contents induced substantial decreases in the PI dielectric constants (2.4-2.7). The re- sultant values were within the applicable range for dielec- tric materials in integrated circuits. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3192-3200, 2011