Effect of VHF excitation frequency on localized deposition of silicon in non-equilibrium-plasma-enhanced CVD by an under-expanded supersonic jet

High rates of localized silicon deposition on a low temperature (473 K) substrate impinged by an under-expanded supersonic jet in a conventional non-equilibrium-plasma chemical vapor deposition process at different excitation frequencies were observed. A single 0.3-mm internal diameter nozzle was used as one of the electrodes for the capacitively coupled plasma. A SiH4/H2 gas mixture at a pressure of 65 kPa was injected through the nozzle into the vacuum chamber at a pressure of 800 Pa. An under-expanded supersonic jet was generated and exhibited turbulence in the vicinity of the substrate surface. A maximum deposition rate of 4.5 μm/s was obtained 10 mm downstream from the nozzle with 0.8 W/cm2 of 100 MHz VHF power.