A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and 275 • C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of 51 l min −1 , a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: 8.0 µm min −1 for Kapton (O 2 and He only), 1.5 µm min −1 for silicon dioxide, 2.0 µm min −1 for tantalum and 1.0 µm min −1 for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.
The reaction chemistry in the afterglow of a non-equilibrium, capacitive discharge, operated at 600 Torr total pressure with (0.5 to 5.0) × 10 17 cm -3 of oxygen in helium, has been examined by ultraviolet absorption spectroscopy, optical emission spectroscopy, and numerical modeling. The densities of the active species,and O 3 , have been determined as a function of the operating conditions. At RF power densities between 6.1 and 30.5 W/cm 3 and a neutral temperature of 100 ( 40°C, the plasma generated (0.2 to 1.0) × 10 16 cm -3 of O( 3 P) and O 2 ( 1 ∆ g ), (0.2 to 2.0) × 10 15 cm -3 of O 2 ( 1 Σ g + ), and (0.1 to 4.0) × 10 15 cm -3 of O 3 . After the power was turned off, the singlet-sigma and singlet-delta states decayed within 0.1 and 30.0 ms, respectively. The concentration of oxygen atoms remained constant for about 0.5 ms, then fell rapidly due to recombination with O 2 to form O 3 . It was found that the etching rate of polyimide correlated with the concentration of oxygen atoms in the afterglow, indicating that the O atoms were the active species involved in this process.
A plasma jet has been developed which deposits silica films at up to 3000Å min −1 at 760 Torr and 115 to 350 • C. The jet operates by feeding oxygen and helium gas between two coaxial electrodes that are driven by a 13.56 MHz radio frequency source at 40 to 500 W. Tetraethoxysilane is mixed with the effluent of the plasma jet and directed onto a substrate located 1.7 cm downstream. The properties of the silica films, as determined by infrared spectroscopy and capacitance measurements, are comparable to those of thermally grown silicon dioxide films at 900 • C.
Silicon dioxide films were grown using an atmospheric-pressure plasma jet that was produced by flowing oxygen and helium between two coaxial metal electrodes that were driven by 13.56 MHz radio frequency power. The plasma exiting from between the electrodes was mixed with tetraethoxysilane (TEOS), and directed onto a silicon substrate held at 115-350 • C. Silicon dioxide films were deposited at rates ranging from 20 ± 2 to 300 ± 25 nm min −1. The deposition rate increased with decreasing temperature and increasing TEOS pressure, oxygen pressure and RF power. For the latter two variables, the rate increased as follows: Rd ∝ P 0.3 O 2 (RF) 1.4. Films grown at 115 • C were porous and contained adsorbed hydroxyl groups, whereas films grown at 350 • C were smooth, dense and free of impurities. These results suggest that the mechanism in the atmospheric pressure plasma is the same as that in low-pressure plasmas.
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