AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA1
In-Situ Monitoring of Unstable Neutral Molecules using Ion Attachment Mass Spectrometer

Thursday, November 6, 2003, 2:00 pm, Room 315

Session: Plasma Diagnostics: Mechanisms
Presenter: Y. Shiokawa, Anelva Corporation, Japan
Authors: Y. Shiokawa, Anelva Corporation, Japan
M. Nakamura, Anelva Corporation, Japan
Y. Hirano, Anelva Corporation, Japan
Y. Taneda, Anelva Corporation, Japan
T. Fujii, Anelva Corporation, Japan
Correspondent: Click to Email
Ion Attachment Mass Spectrometer (IAMS)@footnote 1@ has a unique advantage of fragment-free; mass analysis of true original molecule without dissociation, which is impossible by common methods such as electron impact. Therefore, IAMS has been expected to measure unstable neutral molecules in gas processes, and was already applied to analysis of thermal reaction by metallic-organic material for Cu-CVD and of exhaust gas from dry etching system.@footnote 2@ Although conventional IAMS used in these experiments is large and needed higher pressure than 100Pa for sampling, newly developed IAMS@footnote 3@ is compact and needs only 1Pa, so that IAMS in-situ monitor seems to be realized. Therefore we are investigating capabilities of new IAMS for in-situ monitoring of unstable neutral molecules in many processes, including tool for plasma diagnostics. In this experiment, plasma was produced by small inductively coupled source with 2Pa of c-C@sub 4@F@sub 8@ (100%), and new IAMS was put on it at a distance of 10cm apart. Neutral molecules of CF@sub 2@, C@sub 2@F@sub 4@, COF@sub 2@ by IAMS and ions of CF@sub 2@@super +@, C@sub 2@F@sub 4@@super +@, COF@sub 2@@super +@, ionized in plasma, were measured simultaneously. First, when plasma power increased from 25W to 200W, CF@sub 2@@super +@, C@sub 2@F@sub 4@@super +@ did not change largely, but CF@sub 2@ reduced to one-tenth and C@sub 2@F@sub 4@ one-hundredth at only 50W. On the other hand, both COF@sub 2@@super +@ and COF@sub 2@ did not change largely. Next, when pressure decreased from 2Pa to 0 .5Pa, CF@sub 2@@super +@ kept constant but CF@sub 2@ reduced to one-tenth. These results show that behavior of true original molecules is completely different from that of ions ionized in plasma. It is well known too that neutrals such as CF@sub 2@, C@sub 2@F@sub 4@ cannot be detected correctly by electron impact. Therefore it was confirmed that new IAMS is very useful as in-situ monitor in plasma. We would like to present some examples of c-C@sub 4@F@sub 8@ plasma in manufacturing conditions and of SiH@sub 4@ plasma throughout our talk. Precious discussions with Prof. Nakata and Prof. Takayanagi of Tokyo University of Agriculture and Technology are gratefully acknowledged. @FootnoteText@ @footnote 1@ T.Fujii, Mass Spectrometry Review 19(2000) 111, @footnote 2@ M.Nakamura et al, JVST-A 19(2001) 1105,@footnote 3@ Y.Hirano et al, AVS Int.Sympo. PS-TuP3 (2002)