Oxygen-free polymers: new materials with low dielectric constant and ultra-low dielectric loss at high frequency

Abstract

Two new oxygen-free polymers (p-4F-BVS and p-6F-BVS) have been prepared through a thermal crosslinking reaction based on benzocyclobutene-containing monomers that contain only carbon, hydrogen, fluorine, and silicon atoms without oxygen atoms. These polymers display excellent dielectric performance at a high frequency of 10 GHz with dielectric constants (D_k) of 2.42 and 2.58 and dielectric losses (D_f) of 6.4 × 10⁻⁴ and 1.1 × 10⁻³ for p-6F-BVS and p-4F-BVS. For comparison, a polymer (p-6F-BCB) containing oxygen atoms has been synthesized, which exhibits a D_k of 2.48 and a D_f of 2.33 × 10⁻³. These results indicate that oxygen atoms have a negative effect on the dielectric loss of the organic materials, while the introduction of the bulky –CF₃ groups is positive for decreasing the dielectric constants of the polymers. Such results are significant for the design of low dielectric loss materials. The two polymers also exhibit a low thermal expansion coefficient (CTE) of about 55 ppm °C⁻¹ in the range of temperatures from 30 to 300 °C. These data indicate that the two polymers are highly desirable for application as advanced packaging materials in the microelectronics industry.