INVESTIGATION OF THE ADHESION MECHANISMS OF SILICON ALLOY THIN-FILMS ON POLYMER SUBSTRATES BY IR ELLIPSOMETRY

The adhesion mechanisms of plasma-deposited silicon alloys on polymer substrates (polycarbonate) were studied by a new double-modulated IR e llipsometer. This ellipsometer combines the low frequencies typical of Fourier transform spectroscopy with the high frequency (37 kHz) of th e phase modulation provided by a photoelastic device. The film adhesio n is characterized by the evolution of the vibrational properties of t he polymer surface during the early stages of the film preparation. Th e influence of preliminary plasma treatments on the polymer surface is emphasized. Successive exposure of polycarbonate to Ar and (NH3, Ar) plasmas induces a substrate activation characterized by the formation of CN bonds at the surface. Then it is shown that the SiH4, plasma tre atment leads to the formation of a very thin SiOx layer at the substra te surface. The enhancement of the film adhesion appears to be correla ted to the presence of a vibration located at 1030 cm(-1).