Kgy Karine Letourneur

DETECTION OF CH IN AN EXPANDING ARGON/ACETYLENE PLASMA USING CAVITY RING DOWN ABSORPTION SPECTROSCOPY

Abstract Cavity ring down (CRD) absorption spectroscopy is used to measure the methylidyne (CH) radical in an Ar/C 2 H 2 plasma. The rotational spectrum of the A 2 Δ (v′=0) ← X 2 Π (v′′=0) transition around 430 nm is recorded to determine the total CH ground state density, both as a function of the current through the arc producing the low-pressure Ar plasma and as a function of the injected acetylene flow. Total ground state densities between 5×10 15 and 8×10 16 m −3 are detected. The trends show that the methylidyne radical plays a minor role in the growing mechanism of hydrogenated amorphous carbon films and is predominantly formed in the charge exchange/dissociative recombination channel starting from the C 2 H radical.

Surface loss probabilities of the dominant neutral precursors for film growth in methane and acetylene discharges

The surface loss probabilities of the dominant neutral growth species emanating from methane and acetylene discharges are investigated by depositing thin films inside a cavity. The walls of this cavity are made from silicon substrates. Particles from the plasma can enter the cavity through a slit. The surface loss probability is determined by analysis of the deposition profile inside the cavity. This surface loss probability corresponds to the sum of the probability for effective sticking on the surface and the probability for the formation of a nonreactive volatile product via surface reactions. In a methane discharge the surface loss probability is ∼0.65±0.15 and in an acetylene discharge ∼0.92±0.05, respectively. The dominant contribution in the neutral radical flux emanating from a methane discharge towards the surface consists of CH3 radicals, as known from experiments using mass spectrometry. Furthermore, it is known from literature that the upper limit for the reaction probability for CH3 is in the...

Plasma chemistry during deposition of a-C:H

Abstract The different dissociation products (C, C2, CH and C2H) from C2H2 dissociation in a remote Ar/C2H2 plasma were measured using Cavity Ring Down Spectroscopy (CRDS). Whereas the radicals C, C2 and CH were spectrally identified, in the region where C2H absorption is usually assigned (260–290 nm) only broadband absorption was observed. Suggestions are given on how to explain the broadband absorption, but as yet no clear identification has been made and no species assigned to it.

Argon ion-induced dissociation of acetylene in an expanding Ar/C2H2 plasma

Mass spectrometric and Langmuir probe measurements reveal that the plasma chemistry of an expanding Ar/C2H2 plasma which is used for deposition of hydrogenated amorphous carbon is dominated by argon ion-induced dissociation of the precursor gas. The ion-induced dissociation is very efficient leading to complete depletion under certain conditions. The ion fluence as determined from modeling the mass spectrometry results is in good agreement with Langmuir probe measurements suggesting a one-to-one relation between the argon ion and acetylene consumption. The good correlation found between the growth rate and the acetylene consumption rate expresses the efficient use of the dissociation products.

Plasma chemistry of an expanding Ar/C2H2 plasma used for fast deposition of a-C:H

Mass spectrometric measurements in combination with Langmuir probe measurements reveal that the plasma chemistry of an expanding Ar/C2H2 is dominated by argon-ion-induced dissociation of the precursor gas. Under high arc current conditions complete depletion of acetylene is observed, indicating an efficient consumption of the injected acetylene. A clear correlation between the ion fluence emanating from the arc determined from modeling the mass spectrometry results and Langmuir probe measurements is observed. First measurements by means of cavity ring down and optical emission spectroscopy of the products of the dissociation of acetylene indicate that the dominant dissociation channel is C2H and H.

Stripping of photoresist using a remote thermal Ar/O2 and Ar/N2/O2 plasma

Photoresist is etched using a remote thermal (cascaded arc) plasma in Ar/O2 and Ar/O2N2 mixtures. Very high etch rates, up to 200 nm/s, are achieved at low substrate temperatures (350 K) and low electron and ion temperatures (<0.5 eV). The addition of small amounts of nitrogen (3%) leads to an increase in etch rate. The etch rate in Ar/O2/N2 also increases with time during the etching process. The details of the plasma and surface chemistries are not yet well understood.

Supersonically expanding cascaded arc plasma properties: comparison of Ne, Ar and Xe

Mathematical modelling was applied to study the dynamical and physical properties of the supersonically expanding rare gas plasma formed by a cascaded arc. Keeping constant the volume flow rate and the power input into the plasma, the Ne, Ar and Xe flows are compared. We demonstrate that the difference in mass flow rate affects the dynamic properties of plasma expansion. Modelling and experimental results show that the recombination heating of electrons is more significant in a gas that has a lower ionization potential.