In situ analysis of perfluoro compounds in semiconductor process exhaust: Use of Li+ ion-attachment mass spectrometry

Abstract

Ion-attachment mass spectrometry is capable of accurate and in situ analysis of multicomponent gases that may even include unknown components. We developed a compact apparatus that uses this method and examined its performance for perfluoro compounds, a class of greenhouse gases, using typical standard gases, and subsequently applied the method to the in situ analysis of exhaust gases from a dry-etching machine, where c-C4F8/O2/Ar plasma is generated. Perfluoro compounds of low concentration can be detected as quasimolecules without any fragmentation. In the exhaust gases, many components that are not considered in the current measurement protocol [J. Meyers, D. Green, P. Maroulis, and W. Reagen, Equipment Environmental Characterization Guidelines, Rev. 3.0 (INTEL, 1999)] are measured, as well as components already reported.

Hydrophobic treatment of organics against glass employing nonequilibrium atmospheric pressure pulsed plasmas with a mixture of CF4 and N2 gases

“…13 Generally, nonequilibrium atmospheric-pressure plasmas such as dielectric barrier discharge ͑DBD͒ employing He or Ar gas are produced by applying rf power to dielectriccovered parallel plate electrodes. The gas phase was analyzed by ion attachment mass spectroscopy ͑IAMS͒, [19][20][21][22][23] and optical emission spectroscopy ͑OES͒. In order to reduce the gas cost of the DBD process, we have developed a nonequilibrium atmospheric-pressure pulsed plasma source employing an N 2 based gas instead of rare gases.…”

Direct Mass Spectrometric Study of the Ionic Species Content of a C2HCl3/He/O2 Microwave Discharge Plasma

“…Although a detailed description of the Li + -IAMS experimental setup has been given elsewhere [19], here we briefly review the main points as well as the modifications made for the present study. All experiments were performed using an apparatus produced by the ANELVA Corp. (Fuchu, Japan) with a quadrupole mass spectrometer (QMS) and a lithium ion emitter.…”

Determination of Acetone in Human Breath by Lithium Ion Attachment Mass Spectrometry

“…By contrast, IAMS produces no fragmentation, because neutral target molecules (M) are attached to Li ions with a low translational energy of less than 2 eV induced by the Coulombic force. 15) Thus, the analyte target molecules e#ectively become [M῍Li] ῍ that are stabilized by third-body gases, such as in matrices like N 2 and H 2 O, which remove any excess energy of the adduction. 16) Li ion a$nity also a#ects the relative sensitivity of the analysis, depending on the polarity and structure of compounds.…”

“…16) Li ion a$nity also a#ects the relative sensitivity of the analysis, depending on the polarity and structure of compounds. 15), 17) The relative sensitivity for acetone is higher by 10 5 times than that of N 2 at 100 Pa. 17) Therefore, the sensitivity of the IAMS system is high enough to analyze acetone at ppbv levels or lower in exhaled breath without any preconcentration.…”