Planarization with Cyclotene™ 3022 (BCB) Polymer Coatings

This work examines the planarization of polymer thin film coatings derived from Cyclotene™ 3022 prepolymer resins. Cyclotene™ 3022 is a divinyl siloxane bis-benzocyclobutene prepolymer (DVS-BCB, CAS 117732-87-3). It is used primarily as a dielectric in microelectronics applications. Using profilometry, planarization measurements have been made on thin films spun over features consisting of lines and trenches. Feature widths have been varied from 2 to 1000 μm and the feature depths and film thickness have been varied from 1 to 16 μm. Effects of the processing procedure, resin concentration and resin additives have been explored. Local (versus global) planarization will be discussed. Planarization has been found to depend on all feature dimensions and the polymer film thickness. Lines or other structures having a width of 100 μm or less can be planarized to 90% or better with standard commercial formulations of Cyclotene™ 3022, provided that the mean film thickness is twice the line-height or feature-depth. Metals such as Al, Cu, Cr and Ti can all be planarized to this degree; however, surface preparations may influence the result.