PLASMA POLYMERIZATION OF HEXAFLUOROPROPYLENE - FILM DEPOSITION AND STRUCTURE

Thin, pinhole-free, highly adhering films for advanced technology appl ications can be deposited through plasma polymerization, a low tempera ture, solvent-free process. This research studies the influence of pla sma environment (power, pressure, and monomer mass flow rate (F-m)) on the plasma polymerization of hexafluoropropylene (HFP) using a common industrial parallel-plate plasma reactor. The deposition and structur e of the transparent, yellow, and highly adhering plasma polymerized H FP (PPHFP) film are investigated. The rate of polymerization (R(p)) in creases with power (W) and reaches a plateau when the plasma changes f rom energy starved to monomer starved while the rate of etching (R(e)) continues to increase. The rate of deposition (R(d)), the difference between R(p) and R(e), increases with W, reaches a maximum, and then d ecreases. In a monomer starved plasma R(d) increases with F-m or press ure through a more efficient utilization of the energy supplied at a g iven W or even at a given W/F-m. The abstraction of F and the preferen tial scission of the C - CF3 bond can explain the F/C ratio of 1.5, th e significant amount of double bonds, and the relative lack of CF3 in a PPHFP that consists of CF3, CF2, and CF groups. A gas phase dominate d polymerization produces submicrometer particles some of which agglom erate into spheres. Both the particles and the spheres deposit on the surface and are incorporated into the film with further polymerization . (C) 1995 John Wiley and Sons, Inc.