SiO2 film deposition on the inner wall of a narrow polymer tube by a capacitively coupled μplasma

SiO2 thin films were deposited on the inner wall of a narrow commercial poly(propylene) tube with inner/outer diameters of 1.0 mm/3.0 mm by plasma-enhanced chemical vapor deposition using He or Ar carrier gases and tetraethoxysilane (TEOS)/O2 feedstock gases at high pressures from 30 kPa to atmospheric pressure and at room temperature. A glow μplasma was generated inside the tube by a radio frequency (RF 13.56 MHz) capacitively coupled discharge. X-ray photoelectron spectra and infrared spectra revealed that the inner surface of the plasma-treated tube was covered by a SiO2 film. Scanning electron microscopy images indicated that the film produced by He/TEOS/O2 μplasma had a smooth surface whereas the surface of the film produced by Ar/TEOS/O2 μplasma appeared granulated. Typical deposition rates of approximately 300 nm/min were obtained by He/TEOS/O2 μplasma at atmospheric pressure and a RF power of 11 W.