Articles you may be interested inOptimization of closed ion source for a high-sensitivity residual gas analyzer J. Vac. Sci. Technol. A 32, 021603 (2014); 10.1116/1.4835635Size-selected cluster beam source based on radio frequency magnetron plasma sputtering and gas condensation Rev. Sci. Instrum. 76, 045103 (2005); 10.1063/1.1869332Investigation and reduction of spurious peaks caused by electron-stimulated desorption and outgassing by means of a grid heating method in a hot-cathode quadrupole residual gas analyzer Monitoring of gas composition for processes in the mTorr range is not possible with a conventional residual gas analyzer ͑RGA͒ unless a pressure reduction pumping system is used. A miniature sensor, having dimensions compatible with the mean-free path of gas molecules can operate directly at mTorr pressures while being less expensive and more compact than a conventional apparatus. This article describes a quadrupole RGA which is scaled down by a factor of 7 to operate at pressures up to 10 mTorr. This sensor requires different construction methods and drive electronics than a traditional RGA. A unique ion source with high output has been developed. The small sensor has resolution characteristics very similar to standard size models but sensitivity is reduced in proportion to the ratio of cross-sectional area for each quadrupole r 0 . Response is linear to the mTorr range and a correction method for gas scattering, based on pressure measured by a total pressure gauge included in the ion source design, extends the linear response to 10 mTorr.

Positive ions and radicals in C2F6 and CHF3 high density discharges were measured using a direct-line-of-sight mass spectrometer. The ion energy distributions of the dominant ions were measured as a function of process conditions. Appearance potential mass spectrometry was performed to measure trends of the radical densities. For C2F6 plasmas CF3 and CF3+are the most abundant neutral and ionic species, respectively. CF3 is the most abundant neutral species for a CHF3 plasma, whereas CHF2+ and CF+ are the most abundant ionic species at 600–1000 and 1400 W, respectively. Erosion of the quartz coupling window is an important contaminant source for our inductively coupled plasma system. For comparison, downstream mass spectrometry was also applied using a closed ion source system since this approach is of interest for real-time monitoring and control. Endpoint detection for Si and SiO2 film etching in a CHF3 plasma was investigated using the downstream mass spectrometer system and compared with data obtained simultaneously using the direct-line-of-sight mass spectrometer and optical emission spectroscopy. It was found that the downstream mass spectrometer system can be used for endpoint detection during SiO2 over Si selective etching. The signal changes of different species measured by these techniques for different SiO2 and Si etching processes as a function of time are reported and compared.

This Recommended Practice addresses issues involved in the use of partial pressure analyzers (PPAs) for quantitative analysis and describes recommended apparatus and procedures for determining resolution and sensitivity of a PPA so that the instrument can be used quantitatively for partial pressure, partial flow and gas composition analysis. This updates previous material in the AVS Standard 2.3-1972 (tentative) by including reference to current pressure transfer standards and computer controlled PPAs. This document presents an introduction to PPAs and how they work, definitions pertinent to the use of PPAs, equipment needed for calibration, instrument setup prior to calibration and the measurement of sensitivity and linearity by various methods. Four methods of calibration of a PPA are described as follows: (1) the direct comparison of the PPA output with a transfer standard pressure gauge, (2) the indirect comparison of PPA readings with readings of a transfer standard pressure gauge separated by a flow restriction (pressure divider method), (3) comparison of the PPA output response to known gas flow rates. The first three methods may be carried out on a test stand of suitable design or in situ. The fourth method requires that the pumping speed during calibration be the same as the pumping speed during use, and normally implies that the PPA is calibrated in situ. Discussion on gas interactions, sources of nonlinearity, stability of sensitivity and quality assurance methods is given.

Quantitative analysis of gas mixtures from sources external to a mass spectrometer (MS) requires vacuum hardware that systematically introduces the gas to the ionization region of the MS and calibration procedures that reflect the MS response to time dependent partial pressures in the gas source. Formalism for describing the gas flow, fractionation processes, and the ionization process is presented. Long-term sensitivity data for D2 is presented for three types of mass spectrometers: a quadrupole, a cycloid, and a magnetic sector mass spectrometer. The use of appropriate standard gas mixtures to monitor the accuracy of the MS calibration by control chart is advocated. Bias data from control charts can be used as the basis for minor calibration adjustments rather than total recalibration.

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