Multichannel detector for ion temperature determination in vacuum ultraviolet spectrum

A vacuum ultraviolet spectrometer equipped with a charge coupled device and an open multichannel plate has been used to analyze the temperature of carbon and oxygen ions in the NOVA-UNICAMP tokamak. The detection system was optimized and aligned to minimize the instrumental broadening. Also, higher order diffractions of the emissions were analyzed, resulting in lower experimental errors. The ion temperature was monitored during the tokamak discharge, presenting values between 30 and 70 eV. (c) 2007 American Institute of Physics.78

Efficacy of ECR-CVD silicon nitride passivation in InGaP/GaAs HBTs

High quality passivation silicon nitride films have been obtained requiring no surface pretreatment and being fully compatible with monolithic microwave integrated circuits. The nitride film is deposited by electron cyclotron resonance-chemical vapor deposition directly over GaAs-n substrate and over InGaP/GaAs heterojunction structures, which are used for heterojunction bipolar transistors (HBTs). Metal/ nitride/ GaAs-n capacitors were fabricated for all the samples. Effective charge densities of 3 X 10(11) cm(-2) and leakage current densities of 1 mu A/cm(2) were determined. Plasma analysis showed a reduced formation of molecules such as NH in the gas phase at low pressures, allowing the deposition of higher quality films. The process was used for InGaP/GaAs HBT fabrication with excellent results, such as higher current gain of passivated device comparing to unpassivated HBTs. (c) 2006 American Vacuum Society.2441762176

Mode transitions and hysteresis in inductively coupled plasmas

Optical emission spectroscopy as a noninvasive plasma diagnostic was employed to study mode transitions and hysteresis in an inductively coupled plasma in Ar and Ar/N-2 mixtures. Using selected Ar lines, basic plasma parameters, relevant to the analysis of the mode transitions, were evaluated. Small changes of the electron energy distribution function in the vicinity of the mode transition were detected. The role of metastable Ar atoms in mode transitions and in a hysteresis was clarified. Enhanced production of metastables in the hysteresis region as well as faster transitions in plasmas with higher influence of metastables were observed. (c) 2007 American Institute of Physics.101

Deposition of sacrificial silicon oxide layers by electron cyclotron resonance plasma

Electron cyclotron resonance plasmas with SiH4/O-2/Ar mixtures were used for deposition of thin films of silicon oxide, to be employed as sacrificial layers in microelectromechanical system (MEMS) fabrication. The grown films were characterized by Fourier transform infrared and ellipsometry. Optical emission spectroscopy and Langmuir probe were used for plasma characterization. It has been shown that OH molecules generated in the plasma play an important role in formation of films suitable as sacrificial layers for MEMS fabrication. Extremely high etch rates of grown oxide films (up to 10 mu m/min) were obtained, allowing fabrication of high quality poly-Si suspended structures. (c) 2007 American Vacuum Society.2541166117

Electron density and temperature determination using the concept of particle confinement time uniqueness

The use of atomic hydrogen line emission to determine the particle confinement time τ(p) of a tokamak plasma is a well-known diagnostic technique. Using such a method, for any one of the emission lines, be it from Lyman, Balmer, or Paschen series, the same (i.e., unique) value of τ(p) must be obtained. Furthermore, this measurement is directly related to the local values of the electron temperature and density. We have developed a method based on the H-α, H-β, and H-γ hydrogen line emissions and on the concept of τ(p) uniqueness for a tokamak plasma, to determine the local electron density and temperature. The technique has been applied to plasma discharges generated in the NOVA-UNICAMP tokamak. The results show good agreement with measurements from multichannel Thomson scattering and Langmuir probe. A procedure to simulate the H-α emissivity radial profile using the obtained results is also discussed. © 2005 American Institute of Physics.76

Silicon nitride thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition for micromechanical system applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Thin silicon nitride films have been deposited by a low temperature (20 degrees C) Electron Cyclotron Resonance (ECR) plasma directly on Si substrates. Varying the process pressure, gas composition and radio frequency bias power, films with different properties were obtained. Characterization by Fourier transform infra-red spectrometry reveals the presence of Si-N, Si-H and N-H bonds in the films. Refractive indexes in the range from 1.77 to 2.9 and deposition rates from 13 to 18 nm/min were determined by ellipsometry. Buffered hydrofluoric acid (BHF) etch rates from 0.7 to 509 nm/min, and KOH etch rates lower than I nm/min were obtained. Optical emission spectroscopy showed a strong correlation between the concentration of NH molecules produced in the plasma and porosity of the films. Finally, the films that presented high resistance to etching in KOH and BHF were used to fabricate suspended membranes on Si substrates. With these results, the ECR plasma produced SiNx films that have been used for fabrication of membranes in microelectromechanical systems. (c) 2008 Elsevier B. V. All rights reserved.5162177777782Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FINEPConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq