Chemistry Reference
In-Depth Information
Si
6
H
+
Si
7
H
+
Si
4
H
+
10
4
Si
8
H
+
Si
9
H
+
Si
10
H
+
SiH
3
+
Si
2
H
5
+
Si
5
H
+
Si
3
H
5
+
10
3
10
2
10
1
0
50
100
150
Mass (amu)
200
250
300
FIGURE 6.27
Mass spectra of positive ions of an expanding cascade arc plasma. (From
Kessels, W.M.M. et al.,
Appl. Phys. Lett.
, 72, 2397, 1998.)
10
6
Si
10
H
m
-
Si
20
H
m
-
10
5
Si
30
H
m
-
10
4
Si
40
H
m
-
10
3
10
2
0
200
400
600 800
Mass (amu)
1000
1200
FIGURE 6.28
Negative ions in an RF discharge in SiH
4
. (From Hollenstein, C. et al.,
J. Vac.
Sci. Technol.
A, 14, 535, 1996.)
etching, and thin film deposition. Mass spectrometry is an effective tool for process
control in industrial plasma chemical applications.
6.5.3 N
EUTRAL
P
LASMA
C
OMPONENTS
The mass spectrometric analysis of neutral components in plasmas is applied to stable
atoms and molecules but also to free radicals. The investigation of stable neutral
nonreactive components is extensively discussed in textbooks of mass spectrometry,
[279,323].
The mass spectrometric analysis of neutral particles requires their ionization in
an ion source. Each compound is characterized by its molecular ion with the mass
number
m
z
(not visible for all compounds) and the fragment ions with different
mass numbers and intensities. These mass spectra are compiled for many substances,
see [324]. The definite identification of the neutral component may be supported
by consideration of the mass spectrum determined by the isotopic components with
their various abundances. The quantitative analysis of more complicated mixtures
with the interference of the various cracking pattern demands the decomposition of
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