Diagnostics in helicon plasmas for deposition

Abstract

O 2 and O 2 /TEOS helicon plasmas used for plasma enhanced chemical vapour deposition of SiO x films are investigated in the 1-10 mTorr pressure and 0-800 W rf power ranges. The positive oxygen ions are analysed by energy selective mass spectrometry and Langmuir probes. The oxygen atom concentration is monitored by actinometry and ionization threshold mass spectrometry. In oxygen plasmas it is shown that O + 2 is the major positive ion, and that the oxygen molecules are far from being completely dissociated, due to a very high oxygen atom recombination frequency on the reactor walls. The dissociation degree increases with the rf power reaching 10% at 500 W. In O 2 /TEOS plasmas, the plasma density and electron temperature decrease as the TEOS fraction increases. In contrast, the degree of oxygen dissociation increases sharply with the addition of a few per cent TEOS, is maximum for about 5% TEOS and decreases as TEOS fraction is further increased. In a 95:5 O 2 /TEOS plasma (5 mTorr, 300 W) the fluxes of oxygen positive ions and atoms impinging onto a floating substrate are estimated to be 4 × 10 15 cm −2 and 10 18 cm −2 s −1 respectively. Under these plasma conditions, near-stoichiometric SiO 2 films, with low OH content, are deposited at ambient temperature. The corresponding atom to ion flux ratio is about 250, which suggests the dominant role of oxygen atoms in the deposition kinetics. The comparison of the compositions of layers grown in a 5 mTorr 95:5 O 2 /TEOS plasma at two rf powers confirms the major role of oxygen atoms.

Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

“…Atomic oxygen is in general understood to be more energetic than nitrogen. Values on the order of a significant fraction of 1.0 are sometimes quoted [40][41] , but this result seems to be very ideal for this surface. Since a significantly augmented level of surface reactivity is observed compared to the pure nitrogen cases, it may be a piece of evidence that suggests that energetic species resulting from the high temperature reservoir into the freestream may be a cause of the observed heating.…”

Study of magnetic field influence on charged species in a low pressure helicon reactor

“…The studied helicon reactor consisted of the helicon source made of a 30 cm long glass tube, 15 cm in diameter, and the stainless steel diffusion chamber with the length and diameter, both of 30 cm [5,6]. The source tube was surrounded by two Helmholtz coils supplied by a dc current of 0 ÷ 2 A.…”

“…The magnetic field lines were parallel to the reactor axis in the source and diverged in the diffusion chamber [5]. Compared to the one-coil source [5,6] the amplitude of the axial magnetic field created by the two Helmholtz coils was more uniform.…”

“…Compared to the one-coil source [5,6] the amplitude of the axial magnetic field created by the two Helmholtz coils was more uniform. Calculations of this amplitude (B) showed that varying the current (I B ) in the coils from 0 to 2 A corresponded to B = 0 ÷ 10 mT (0 ÷ 100 Gauss) in the source tube and 0 ÷ 1.4 mT (0 ÷ 14 Gauss) in the diffusion chamber (Fig.…”

“…The present paper is focused on an investigation of the rf helicon reactor used for material processing, namely on an influence of dc magnetic field and rf power on the discharge parameters in the diffusion chamber. The reactor was previously used for the deposition of silicon oxides and organosilicon polymer films as well as plasma diagnostics [5]. It was, however, equipped with one magnetic coil around the source tube whereas here, two coaxial coils producing more homogeneous axial magnetic field were used.…”