Thermal imidization of poly(amic acid) on Si(100) surface modified by plasma polymerization of glycidyl methacrylate

The plasma polymerization of glycidyl methacrylate (GMA) on pristine and Ar plasma-pretreated Si(100) surfaces was carried out. The epoxide functional groups of the plasma-polymerized GMA (pp-GMA) could be preserved, to a large extent, through the control of the glow discharge parameters, such as the radio-frequency (RF) power, carrier gas flow rate, system pressure, and monomer temperature. The pp-GMA film was used as an adhesion promotion layer for the Si substrate. The polyimide (PI)/pp-GMA-Si laminates, formed by thermal imidization of the poly(amic acid) (PAA) precursor poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA) on the pp-GMA-deposited Si surface (the pp-GMA-Si surface), exhibited a 180°-peel adhesion strength as high as 9.0 N/cm. This value was much higher than the negligible adhesion strength for the PI/Si laminates obtained from thermal imidization of the PAA precursor on both the pristine and the argon plasma-pretreated Si(100) surfaces. The high adhesion strength of the PI/pp-GMA-Si laminates was attributed to the synergistic effect of coupling the curing of epoxide functional groups in the pp-GMA layer with the imidization process of the PAA, and the fact that the plasma-deposited GMA chains were covalently tethered onto the Si(100) surface. The chemical composition and structure of the deposited films were characterized, respectively, by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, while the surface morphology of the deposited films was characterized by atomic force microscopy (AFM).