Density and production of NH and NH2 in an Ar–NH3 expanding plasma jet

Abstract

The densities of NH and NH 2 radicals in an Ar-NH 3 plasma jet created by the expanding thermal plasma source were investigated for various source-operating conditions such as plasma current and NH 3 flow. The radicals were measured by cavity ringdown absorption spectroscopy using the ͑0,0͒ band of the A 3 ⌸ ← X 3 ⌺ − transition for NH and the ͑0,9,0͒-͑0,0,0͒ band of the à 2 A 1 ← X 2 B 1 transition for NH 2 . For NH, a kinetic gas temperature and rotational temperature of 1750± 100 and 1920± 100 K were found, respectively. The measurements revealed typical densities of 2.5 ϫ 10 12 cm −3 for the NH radical and 3.5ϫ 10 12 cm −3 for the NH 2 radical. From the combination of the data with ion density and NH 3 consumption measurements in the plasma as well as from a simple one-dimensional plug down model, the key production reactions for NH and NH 2 are discussed.

A capacitive probe with shaped probe bias for ion flux measurements in depositing plasmas

“…These processes, namely, charge transfer reaction between the argon ions emanating from the plasma source and NH 3 and/or SiH 4 molecules, followed by dissociative recombination with low energy electrons, have been reported in detail elsewhere. 13,16,17 The ion flux is gradually decreasing from fore, above a NH 3 flow rate of 16 sccs, no further enhancement of the dissociation of SiH 4 molecules is achievable and the ion flux remains constant ͑cf. Fig.…”

“…16,17 The ion current obtained from the I-V measurements corresponding to V bias = −10, I i,LP , was plotted as a function of the ion current I i,IP , which resulted from the ion probe measurements. In the case of the ion probe measurements in a high density Ar plasma, the collecting area needed to be made smaller to perform accurate ion probe measurements.…”

N, NH, and NH2 radical densities in a remote Ar–NH3–SiH4 plasma and their role in silicon nitride deposition

“…These molecular ions recombine dissociatively with electrons into mainly N and NH radicals. 33 The charge transfer reaction as well as the dissociative recombination reaction are very fast and the N and NH densities both saturate at a level of 3 ϫ 10 12 cm −3 for NH 3 flows above 3 SCCS ͑standard cubic centimeter per second͒ due to the limited amount of Ar + ions available. Langmuir probe measurements carried out at 36 cm from the plasma source revealed an exponential decrease of the ion density by three orders of magnitude until 3 SCCS NH 3 was injected in the plasma, 28 which is in line with the constant N and NH densities above 3 SCCS NH 3 .…”

H2generation in Ar/NH3microdischarges

“…In this paper, we discuss results from computational investigations of the use of Ar/NH 3 mixtures for production of H 2 in microdischarge devices. Although NH 3 is commercially produced by reactions 4 Author to whom any correspondence should be addressed. 5 Present address: Novellus Systems, Inc., 3011 N. 1st St, San Jose, CA 95134 USA.…”

“…Van den Oever et al [4,5] investigated the production of NH and NH 2 in expanding Ar/NH 3 plasmas for possible use in ultrahigh-rate deposition of Si 3 N 4 films. Recent interest in NH 3 plasmas includes high pressure (0.1-1 atm) dielectric barrier discharges (DBDs) and micro-hollow cathode discharges for conversion of NH 3 to H 2 .…”