Vapor deposition of stable copolymer thin films in a batch iCVD reactor

Abstract

This study demonstrates the deposition of poly(ethylhexyl acrylate-co-ethylene glycol dimethacrylate) (P(EHA-co-EGDMA)) copolymer thin films in a batch type initiated chemical vapor deposition (iCVD) reactor. Crosslinked copolymers are desired for many applications because of their high stable properties. iCVD polymers derived by monomers bearing only one vinyl bond are usually linearly structured polymers and hence they are not durable, which is unfavorable for many real-world applications. Robust crosslinked iCVD films can be produced with the help of crosslinkers. In a typical iCVD process, copolymer thin film is produced by constantly feeding monomer vapor and crosslinker into the reactor. The monomer/crosslinker ratio should be precisely controlled for fabrication of reproducible thin films. In order to eliminate problems caused by adjusting the flowrates of precursors, a closed-batch type iCVD reactor was used for the first time in this study to produce copolymer thin films. The variation of precursors' partial pressures allowed control over the copolymer thin film structures. As compared with homopolymer, copolymers showed the better chemical and thermal stable properties. Almost 40% of the copolymer thin film remained on the substrate surface at an annealing temperature of 300 degrees C, whereas the homopolymer film was completely removed at an annealing temperature of 280 degrees C.