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The H-terminated surface of diamond when activated with NO2 produces a surface conduction layer that has been used to make field effect transistors (FETs). Previous reports have suggested that during NO2 exposure (NO2-activation), NO2− forms on the diamond surface and generates positive carriers (holes) in the diamond, making the diamond surface conductive. We report here on X-ray-photoelectron-spectroscopy (XPS) surface characterization of single crystal diamonds and on infrared absorption of diamond powder. After activation, XPS showed the presence of N atoms on the diamond surface, but infrared absorption found no evidence of NO2−, but instead NO3− is present on the diamond surface. Two wet chemistry techniques determined the concentration of NO3− per milligram of diamond powder. With the powder's surface area measured by the BET technique, the surface NO3− concentration was measured to be between 6.2 × 1013 and 8.2 × 1013 cm−2. This is in the same range as the carrier densities, 3 × 1013 to 9 × 1013 cm−2, determined by Hall mobility and surface conductivity measurements of single crystal diamonds. Using similar techniques, the concentration of NO2− was determined to be Both the surface conductance and the surface H atoms are stable in dry nitrogen, with or without NO2-activation, but the surface conductance, the concentrations of H atoms both with and without activation and NO3− decrease when exposed to laboratory air over a period of hours to days. Infrared absorption measurements showed the reduction of surface NO3− and H atoms during laboratory air exposure, but gave no indication of what reactions are responsible for their loss in laboratory air.

Oxide etching yield has been measured directly with inductively coupled fluorocarbon plasmas. The yields measurement technique of this work can provide useful information for feature profile evolution modeling, which is essential to understand various issues in oxide etching such as reactive ion etching (RIE) lag, inverse RIE lag, etch stop, microtrenching, bowing, etc. Etching and deposition yields per ion were measured using quartz crystal microbalance (QCM) as a function of ion bombardment energy, ion-to-neutral flux ratio, and ion-impinging angle. C2HF5, C2F6, C2H4F2, and C4F8 were used for the oxide etching. Oxide etching mechanism with those gases is complex because etching and deposition are involved at the same time. In highly selective processes fluorocarbon deposition plays important role in determining etching characteristics. Two fluorocarbon deposition mechanisms are identified in this work: neutral deposition and ion-enhanced deposition. The low-energy ions are believed to enhance the deposi...

Etching yields of silicon in F2, Cl2, Br2, and HBr high density plasmas have been measured as a function of ion bombardment energy, ion bombardment angle, and plasma composition. This information contributes to a database of experimental values needed for feature profile evolution modeling. For all plasma chemistries, the etching yield increases approximately with the square root of ion energy. Pure Cl2 and pure HBr plasmas have very similar etching yields. Silicon etching rates are lower in HBr plasmas than in Cl2 plasmas due to lower ion fluxes, not lower etching yields. The dependence of the etching yield on ion bombardment angle is significantly different for Cl2 and HBr plasmas. The etching yield in Cl2 plasmas decreases rapidly for ion angles above 60° (measured from the surface normal), which results in significant ion scattering from the sidewalls, and may cause the sidewall bowing and microtrenching seen when patterning polysilicon with Cl2 plasmas. The etching yield in HBr plasmas decreases more...

The etching chemistry of benzocyclobutene (BCB) low-k dielectric films was studied in a high density plasma etcher using F2+O2 and Cl2+O2 plasmas. The etching rate in F2+O2 plasmas exceeded 1.2 μm/min with selectivity over oxide and nitride of 16 and 32, respectively. The etching rate in Cl2+O2 plasmas exceeded 0.6 μm/min with selectivity over oxide and nitride of 40 and 80, respectively. BCB films do not etch in pure Cl2 or pure O2 plasmas without ion bombardment, but etching rates of 1000 A/min were observed using F2 plasmas without ion bombardment. The ion flux in F2+O2 plasmas is primarily O2+ and O+, whereas in Cl2+O2 the dominant ion is ClO+. BCB etching yields in F2+O2 plasmas were measured with a plasma beam/quartz crystal microbalance system. The etching yields suggest that the neutral fluxes and surface chemistry control the etching rates under these conditions, not the ion flux. Using x-ray photoelectron spectroscopy, it was determined that oxygen plasmas preferentially remove the carbon conten...

An electron beam generated plasma reactor is used to decompose low concentrations (100–3000 ppm) of 1,1-dichloroethane and 1,1-dichloroethene in atmospheric pressure air streams. The energy requirements for 90% and 99% decomposition of each compound are reported as a function of inlet concentration. Dichloroethene decomposition is enhanced by a chlorine radical propagated chain reaction. The chain length of the dichloroethene reaction is estimated to increase with dichloroethene concentration from 10 at 100 ppm initial dichloroethene concentration to 30 at 3000 ppm. Both the dichloroethane and dichloroethene reactions seem to be inhibited by electron scavenging decomposition products. A simple analytic expression is proposed for fitting decomposition data where inhibition effects are important and simple first order kinetics are not observed.

The effect of a carbon-carbon double bond on the energy required for decomposition in an electron beam-generated plasma reactor is studied by comparing the decomposition of trichloroethylene and 1,1,1-trichloroethane. A reaction mechanism for TCE decomposition based on a chlorine radical chain reaction is presented which accounts for the formation of all of the experimentally observed reaction products. TCE decomposition is autocatalyzed by reaction products, whereas TCA decomposition is inhibited. The rate expression for the decomposition of TCE in the reactor is determined to be r=−[T](15.07[T0]−0.40+0.006{[T0]−[T]}), where [T] and [T0] are both in ppm, and r is in ppm Mrad−1. The energy expense ɛ for TCE decomposition is determined as a function of inlet concentration. For 99% decomposition of 100 ppm TCE in air, ɛ=28 eV/molecule, and ɛ=2.5 eV/molecule at 3000 ppm. This is only 2.5–5% of the amount of energy required to decompose a similar amount of TCA as reported by the authors in a previous study. By comparing the energy requirements for TCE decomposition to those for TCA decomposition, the TCE reaction chain length is determined to increase from approximately 20 at 100 ppm initial TCE concentration, to 40 at 3000 ppm.

Fully depleted silicon-on-insulator transistors were fabricated using two different metal gate deposition mechanisms to compare plasma damage effects on gate oxide quality. Devices fabricated with both plasma-enhanced atomic-layer-deposited (PE-ALD) TiN gates and magnetron plasma sputtered TiN gates showed very good electrostatics and short-channel characteristics. However, the gate oxide quality was markedly better for PE-ALD TiN. A significant reduction in interface state density was inferred from capacitance-voltage measurements as well as a 1200× reduction in gate leakage current. A high-power magnetron plasma source produces a much higher energetic ion and vacuum ultra-violet (VUV) photon flux to the wafer compared to a low-power inductively coupled PE-ALD source. The ion and VUV photons produce defect states in the bulk of the gate oxide as well as at the oxide-silicon interface, causing higher leakage and potential reliability degradation.

An electron beam generated plasma reactor was used for the decomposition of carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, 1,1-dichloroethane, toluene, and Freon 113. 99% decomposition of most compounds is achieved in the reactor. The energy requirements for decomposition of these compounds are given, and these results are discussed in terms of the electron capture rate coefficients and the plasma chemistry of the molecules.

Atomic layer deposition (ALD) of high-quality gadolinium oxide thin films is achieved using Gd(iPrCp)3 and O2 plasma. Gd2O3 growth is observed from 150 to 350 °C, though the optical properties of the film improve at higher temperature. True layer-by-layer ALD growth of Gd2O3 occurred in a relatively narrow window of temperature and precursor dose. A saturated growth rate of 1.4 A/cycle was observed at 250 °C. As the temperature increases, high-quality films are deposited, but the growth mechanism appears to become CVD-like, indicating the onset of precursor decomposition. At 250 °C, the refractive index of the film is stable at ∼1.80 regardless of other deposition conditions, and the measured dispersion characteristics are comparable to those of bulk Gd2O3. XPS data show that the O/Gd ratio is oxygen deficient at 1.3, and that it is also very hygroscopic. The plasma etching rate of the ALD Gd2O3 film in a high-density helicon reactor is very low. Little difference is observed in etching rate between Cl2 a...

The etching of polysilicon by low energy Cl2+HBr plasma beam was studied, and the etching yield as a function of composition, ion impingement energy and ion incident angle was measured. The etching yield by HBr plasma beam is slightly lower than Cl2 plasma beam. The angular dependence of etching yield by both Cl2 and HBr beam strongly suggests the mechanism of ion induced chemical etching, with highest etching yield at normal incident angle. For Cl2 beam, the etching yield almost keeps constant until the off-normal incident angle of ions increased to 45°, while for HBr beam, the etching yield starts dropping even with small off-normal angle. The angular dependence of etching yield by Cl2+HBr plasma at different composition exhibits similar trend as pure HBr. Using x-ray photoelectron spectroscopy, the coverage of Cl and Br on polysilicon surfaces after etching in Cl2+HBr plasmas was measured. The Cl coverage after etching with pure Cl2 plasma beam is about 1.4 times higher than the Br coverage after etchi...

Experimental results in a low temperature, low power density rf plasma reactor show that C2F6 can be decomposed by plasma reaction with oxygen, but CF4, an undesirable byproduct, is produced. Previously, it had been shown in a high temperature, high power density microwave reactor that C2F6 can be decomposed without CF4 formation. Calculations show that low temperature neutral species kinetics favor the formation of CF4 over COF2, while the opposite is true at high temperature. Further, a high degree of feedstock dissociation such as that observed in high density plasma reactors is predicted to lead to very little CF4 formation. Calculations show that adding hydrogen, water, or hydrocarbons to the C2F6+O2 mixture should reduce the power necessary for abatement, and will reduce CF4 formation. Hydrogen is predicted to getter atomic fluorine to form thermodynamically stable HF, and thus prevent perfluorocompound reformation.