Structure of Copolymer Films Created by Plasma Enhanced Chemical Vapor Deposition (PECVD)

The structures of substrate/layer and layer/air interfaces in copolymer films made using plasma enhanced chemical vapor deposition (PECVD) have been probed for the first time using x-ray reflectivity (XR). Both XR and atomic force microscopy (AFM) measurements revealed extremely smooth surfaces for copolymer films made from comonomers benzene and octafluorocylcobutane (B-OFCB) and from comonomers hexamethyldisiloxane and octafluorocylcobutane (HMDS-OFCB). The surface roughnesses range from 2.5 to 9.5 {\AA} for both B-OFCB and HMDS-OFCB films. HMDS-OFCB copolymer films and B-OFCB copolymer films deposited on Si substrates are characterized by a uniform scattering length density throughout the film thickness. The XR measurements also reveal that one can tune the refractive index by varying the monomer feed ratio in the copolymer films.