Parylene-AF4: a polymer with exceptional dielectric and thermal properties

[2.2]Paracyclophanes are useful chemical vapor deposition (CVD) precursors of thin film polymers, known as Parylenes. Parylenes are ideally suited for use as conformal coatings in a wide variety of applications, such as in the automotive, medical, electronics, and semiconductor industries. Parylene coatings are inert and transparent and have excellent barrier properties. The bridge-fluorinated 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane (AF4) is the CVD precursor of Parylene-AF4 polymer, which combines a low dielectric constant with high thermal stability, low moisture absorption, and other advantageous properties. With such properties, and because its in vacuo deposition process ensures conformality to microcircuit features and superior submicron gap-filling capability, Parylene-AF4 has considerable promise as an interlayer dielectric for on-chip high-speed semiconductor device interconnection. This paper reviews the synthesis and properties of Parylene-AF4 and its paracyclophane precursor, including a discussion of the importance of the fluorinated bridges, the advantages of the dimeric precursor, and why Parylene-AF4 has the potential to meet the needs of the semiconductor industry with respect to the key properties of a potential interlayer dielectric.