Instrumental Effects on Sensitivity Factors in Secondary Neutral Mass Spectrometry Measurements

Abstract

Some instrumental effects on sensitivity factors in SNMS (secondary or sputtered neutral mass spectrometer) have been investigated with :[II-V semiconductors, viz., GaAs, GaP and InP. There is a large variation of sensitivity factors, affected by target potential, ion optics setting and multiplier voltage, which is related to the mass difference between component elements. But relatively small variation of sensitivity factors by plasma conditions was found. KeywordsSecondary neutral mass spectrometry, relative sensitivity factor SNMS (secondary, or sputtered neutral mass spectrometer) has received a lot of attention because of its advantages in quantification and depth resolution.1-11 Principle and instrumental reality of INA-3 are described elsewhere.1,3,4,1o Some instrumental effects of INA-3 (Leybold) on relative intensities, from which sensitivity factors can be calculated, have been investigated on III-V semiconductors. In order to discuss quantification of solid mass spectrometer, sputtering process and atomization, ionization process, ion transfer process, and detection process have to be examined. These processes are influenced by target potential, plasma condition, ion optics setting, and multiplier condition in the case of INA-3. The effects of ion optics of INA-3 have been investigated and are described in ref. 12. Briefly, intensity ratios change very much by ion optics setting condition, depending on mass difference between the constituents; in the case of GaAs the variation of intensity ratios was less than 20%, while for InP it was more than 200%.In this report, the effects of target potential, plasma conditions and multiplier condition on sensitivity factors will be discussed. Since sputtering process and ionization process are separated, SNMS should be free of matrix effect compared with SIMS (Secondary Ion Mass Spectrometer). Although it has been said that comparatively uniform sensitivity factors can be obtained1'4, strong variation of sensitivity factors with these instrumental parameters are found.Experimental

Quantitative analysis of films by ion microbeam methods. II: SIMS

“…It has small matrix effect (factor 3 [58]), but a relatively high LLD because of poor extraction efficiency of the sputtered neutrals.…”