Studies of the mechanism of boron nitride thin-film formation by means of nitrogen-argon gas mixture plasma jet

Abstract

The mechanism of boron nitride thin-film formation using the nitrogen-argon gas mixture plasma jet, which is a new method reported in our previous paper, has been studied. The electron temperature, electron density, and magnitudes of various ion and radical species in the plasma jet have been measured by an electrostatic probe and by optical spectroscopic methods. The amount of recombination of free nitrogen atoms by three-body conversion was estimated using the emission intensity of the first positive band system from nitrogen B state vibrational level v = 11. The emission intensity from vibrational level v = 11 in the vicinity of the boron target shows a more than one order of magnitude increase than when the boron target is absent, and the peak value occurs at a gas pressure of approximately 5 Torr to 10 Torr. Experimental data are discussed in connection with the optimum discharge condition of BN synthesis in the plasma. It is concluded that enhanced recombination on the boron target and substrate surface supplies large amounts of molecular nitrogen ions and vibrationally excited nitrogen molecules in the vicinity of the substrate, and thus that the high-energy ion-rich condition makes it possible to form a cubic BN film on the substrate surface placed in the plasma jet. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 1–6, 1997