Optical Emission Imaging and Modeling Investigations of Microwave-Activated SiH₄/H₂ and SiH₄/CH₄/H₂ Plasmas

Abstract

Silicon is a known trace contaminant in diamond grown by chemical vapor deposition (CVD) methods.Deliberately Si-doped diamond is currently attracting great interest because of the attractive optical properties of the negatively charged silicon-vacancy (SiV − ) defect. This work reports in-depth studies of microwave activated H2 plasmas containing trace (10-100 ppm) amounts of SiH4, with and without a few % of CH4, operating at pressures and powers relevant for contemporary diamond CVD, using a combination of experiment (spatially resolved optical emission (OE) imaging) and two-dimensional

Self-consistent modeling of microwave activated N2/CH4/H2 (and N2/H2) plasmas relevant to diamond chemical vapor deposition

“…At yet higher CH4 additions (X0(CH4) >2%), ion production by EII of neutral CxHy species (mainly C2H2) is predicted to start exceeding the sum of that from EII of H and H2, resulting in a slow and progressive decline in Te. Such trends upon CH4 addition were also noted and discussed in [41].…”

Imaging and Modeling C2 Radical Emissions from Microwave Plasma-Activated Methane/Hydrogen Gas Mixtures: Contributions from Chemiluminescent Reactions and Investigations of Higher-Pressure Effects and Plasma Constriction

“…The H-atom number density in the plasma core is predicted to barely change. Such minor variations in these key parameters can be understood by recognizing the X 0 (CH 4 )-dependent balances between the ionization (i.e., associative ionization (AI) reactions between H­( n ≥ 2) atoms and H 2 and electron impact ionization (EII) of C 2 H 2 , H 2 , and H) and electron–ion recombination processes (whereby H 3 + ions interchange with C x H y + ions), as recently discussed in detail for the more complex case of dilute MW activated Si/C/H plasmas . The predicted insensitivity of these key plasma parameters to changes in X 0 (CH 4 ) is reflected in the near constancy of the (predicted) {C 2 (C)}/{C 2 (d)} and (observed) R (C/d) versus z plots shown in Figure (b).…”

“…Such minor variations in these key parameters can be understood by recognizing the X 0 (CH 4 )- + ions), as recently discussed in detail for the more complex case of dilute MW activated Si/C/H plasmas. 21 The predicted insensitivity of these key plasma parameters to changes in X 0 (CH 4 ) is reflected in the near constancy of the (predicted) {C 3.4. Higher Pressure Effects and Plasma Shrinkage.…”

“…The MW activated plasma is luminous, and spectroscopic analysis reveals emissions from electronically excited H atoms, H 2 molecules, , CH, C 2 and C 3 radicals, and even C 2 – anions . These emissions will often be supplemented by CN radical emission if nitrogen has been added to the input gas mixture (or if the plasma contains any significant air contamination) and will be enriched further by emissions from B atoms/BH radicals, OH radicals, Si atoms/SiH radicals, or PH radicals upon addition of, respectively, a B-, O-, Si-, or P-containing source gas. The relative intensities of these various emissions depend on processing parameters such as the C/H input mixing ratio (and any air impurities), the pressure and applied MW power, and the spatial location within the reactor and, even without any detailed spectroscopic analysis, allow opportunities for checking the process reproducibility and control.…”

Growth Conditions and Substrate Misorientation Angle Dependences of Silicon Incorporation in Chemical Vapor Deposition Diamond

“…After the cleaning process, the residual level of silicon in the reactor was estimated from the ratio of the emission intensities of the silicon line at a wavelength of 288.16 nm to the dissociative continuum for a discharge in pure hydrogen. It is known that the addition of methane to a hydrogen plasma with a low content of silane leads to a significant decrease of the emission intensity of silicon lines in the plasma; [ 8,24 ] therefore, the residual level was estimated in pure hydrogen. To calibrate the residual level, a small flow of silane was added to the hydrogen plasma.…”