JPS6237860A - Secondary ion mass spectrometer - Google Patents

Abstract

PURPOSE:To simultaneously measure positive and negative secondary ions, by providing two neutralizing electrodes in the face of each other between the emission slit and secondary electron multiplier of a four-electrode mass spectrometer, and applying a secondary electron removing magnetic field be tween the electrodes. CONSTITUTION:Neutralizing electrons 23, 24 are disposed parallel in the face of each other between an emission slit and a secondary electron multiplier 8. When secondary ions 25, 26 collide against the neutralizing electrodes 23, 24, secondary electrons are emitted therefrom. A magnetic field 29 is applied to prevent the secondary electrons from entering into the secondary electron multiplier 8 to make a noise. The secondary electrons are curved into a flying orbit by the magnetic field 29 so that the secondary electrons are removed. The intensity of the magnetic field 29, which would affect the flying orbits of the secondary ions 25, 26 immediately after their passage through the emis sion slit 7, is kept at an appropriate level so that the magnetic field does not affect the flying orbits of the secondary ions. As a result, the positive and negative secondary ions can be simultaneously detected without receiving the noise due to the secondary electrons.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to a secondary ion mass spectrometer that simultaneously detects positively charged secondary ions and negatively charged secondary ions.

<Prior art> Figure 2 shows a conventional secondary ion mass spectrometer. The secondary ion mass spectrometer shown in the figure consists of an ion source 1, an analysis sample 3, an entrance slit of 5°, a cylindrical electrode 6. Pickpocket pickpocket 91-7
．． Secondary electron multiplier8. DC high voltage power supply9. Load resistance 10.
Amplifier 11. It is composed of a quadrupole mass spectrometer which is composed of an ion resonance field 12 and a power supply 13 in which a DC voltage and a high frequency voltage are superimposed.

Therefore, when ions of 5 to 10 keV (these ions are called secondary ion beam 2) emitted from the ion source 1 bombard the analysis sample 3, positively charged and negatively charged secondary ions 4 are emitted from the analysis sample 3. do. This secondary ion 4 will be incident on a quadrupole mass spectrometer and will be analyzed.

That is, the secondary ions 4 that have passed through the entrance slit 5 and entered the ion resonance field 12 surrounded by the four cylindrical electrodes 6 are as follows.
It receives a high frequency electric field which is a superimposition of a DC electric field and an AC electric field applied by the electric rR13. For this reason, the ion resonance field 1
Of the secondary ions 4 incident on 2, only those having masses suitable for the resonance conditions determined by the strength of the high-frequency electric field, frequency, and mass of the ions fly in a stable trajectory and exit from the exit sulin l-
It will be emitted from 7. On the other hand, secondary ions having a mass that is not suitable for the above-mentioned resonance conditions scatter and disappear while flying in the ion resonance field 12.

Of the secondary ions exiting 17 from the exit slit 7, only positively charged ions enter the secondary electron multiplier 8, become an electrical signal, appear on the load resistor, and are amplified by the multiplier 11.

In this case, the DC high-voltage power supply 9 serves as a driving power supply for the secondary multiplier tube 8, and at the same time, the secondary ions 4 that have reached the exit slit 7
This is because, while it has the role of accelerating positively charged ions among the secondary ions 4 and guiding them to the secondary electron multiplier 8, it has the effect of blocking negatively charged ions among the secondary ions 4. Therefore, such a secondary ion mass spectrometer cannot detect negatively charged secondary ions.

Therefore, in order to detect negatively charged ions among the secondary ions 4, it is necessary to change the wiring in the vicinity of the secondary electron multiplier tube 8 of the mass spectrometer as shown in FIG. In this way, the negatively charged ions among the secondary ions that have reached the exit slit 7 are accelerated by the DC power supply 14, enter the secondary electron multiplier 8, become an electrical signal, and appear on the load resistor 10. It is amplified by the amplifier 11 by the diameter of the capacitor 13. The DC power supply 9 is a power supply for driving the secondary electron multiplier tube 8, and the capacitor 15 is connected to a high voltage l! This is a high withstand voltage capacitor for I stop, and the other features are the same as those shown in FIG.

<Problems to be Solved by the Invention> As mentioned above, in conventional secondary ion mass spectrometers, the measurement systems for positively charged secondary ions and negatively charged secondary ions are completely different. It was not possible to simultaneously measure negatively charged ions.

An object of the present invention is to provide a secondary ion mass spectrometer that can simultaneously measure positively charged secondary ions and negatively charged secondary ions.

<Means for Solving the Problems> The configuration of the present invention to achieve the above object is a secondary ion mass consisting of an ion source for emitting primary ions, an analysis sample, and a quadrupole mass spectrometer. In the analyzer, between the quadrupole mass spectrometer exit slit and the secondary electron multiplier,
A neutralizing electrode connected to an accelerating power source for positively charged secondary ions and a neutralizing electrode connected to an accelerating power source for negatively charged secondary ions are arranged facing each other, and a secondary electron removing electrode is disposed between these electrodes. A special magnetic field is applied.

Among the secondary ions that reach the exit slit, positively charged secondary ions accelerate and collide with the negatively charged neutralizing electrode, and are neutralized by obtaining electromagnetism, while negatively charged secondary ions are neutralized. It accelerates and collides with the charged neutralizing electrode, loses its charge and becomes neutralized.

In this way, the positive and negative secondary ions are neutralized and become high-speed 4-atomic atoms, which then enter the secondary electron multiplier tube, become an electrical signal, appear on the load resistor, and are multiplied by the multiplier. still,
The flight trajectory of the secondary electrons emitted from the neutralizing electrode due to the collision ζ of the secondary ions is bent by the secondary electron removal magnetic field, and the secondary electrons □ do not enter the multiplier tube.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Incidentally, the same parts as those in the prior art described above are given the same numbers and the description thereof will be omitted.

An embodiment of the present invention will be explained in FIG. As shown in FIG. 1, neutralizing electrodes 23 and 24 are arranged parallel to each other and facing each other between the output sulin)-7 and the secondary electron multiplier tube 8, and these neutralizing electrodes 23 and 24 are located in the opposite direction, respectively. It is connected to accelerating power sources 21 and 22 for charged secondary ions and negatively charged secondary ions, and has a negative potential or a positive potential. Therefore, positively charged secondary ions 25 that have passed through the exit slit 7 are accelerated by the power source 21, obliquely enter the neutralizing electrode 23, acquire electric charge from the neutralizing electrode 23, are neutralized, and become fast atoms 27. Become. On the other hand, the negatively charged secondary ions 26 are accelerated by the power source 22, obliquely enter the neutralizing electrode 24, give electrons to the neutralizing electrode 24, are neutralized, and become high-speed atoms 28.

When the secondary ions 25 and 26 obliquely enter the neutralization electrode 23, 24, they undergo scattering close to elastic scattering, so the high-speed atoms 27
The kinetic energy of ,28 is that the secondary ions are the power source21.22
It has a large value close to the kinetic energy obtained by accelerating it. Thereafter, the high-speed atoms 27 and 28 enter the secondary electron multiplier tube 8, appear as an electric signal at the load resistor 10, and are multiplied by the amplifier 11.

In addition, the secondary ions 25 and 26 are connected to the neutralization electrodes 23 and 2, respectively.
4, secondary electrons are emitted from the neutralizing electrode. In order to prevent these from entering the secondary electron multiplier 8 and causing noise, a magnetic field 29 is applied perpendicular to the plane of the paper, and the flight trajectory of the secondary electrons is bent by the magnetic field 29, and the secondary electrons are removed. There is. The magnetic field 29 affects the trajectory of the secondary ions 25 and 26 immediately after passing through the exit slit 7, but the ion 2
Since the mass of 5,26 is about 2000 times or more than the mass of an electron, by keeping the strength of the magnetic field 29 at an appropriate value, it is possible to avoid affecting the flight trajectory of the secondary ions 25,26. It can be done.

Therefore, positive and negative charged secondary ions are detected simultaneously without being affected by secondary electron noise.

<Effects of the Invention> As specifically explained above based on the examples, the secondary ion mass spectrometer of the present invention has the advantage of being able to simultaneously analyze secondary ions with positive and negative charges without changing the power supply connection. has.

[Brief explanation of drawings]

Figure 1 (al is a schematic configuration diagram of a secondary ion mass spectrometer according to an embodiment of the present invention, Figure 1 (bl is the same figure (A in al)
- A' line sectional view, Figure 2 (al is a schematic diagram of a conventional secondary ion mass spectrometer that detects positively charged secondary ions, Figure 2 (b) is B - in Figure 2 (a)) B' line sectional view, 3rd
Figure (al) is a schematic configuration diagram of a conventional secondary particle mass spectrometer that detects negatively charged secondary ions, and Figure 3 (b) is the same figure (al
It is a sectional view taken along the line c-c' inside. In the drawings, 1 is an ion source, 2 is a secondary ion beam, 3 is an analysis sample, 4 is a secondary ion, 5 is an entrance slit, 6 is a cylindrical electrode, 7 is an exit slit, 8 is a secondary electron multiplier, 9 is a DC high-voltage power supply, 10 is a load resistor, 11 is an amplifier, 12 is an ion resonance field, 13 is a power supply in which DC and high frequency are superimposed, 14 is a power supply for ion acceleration, 15 is a capacitor, 21 is a positive charge secondary 22 is the accelerating voltage of negatively charged secondary ions, 23.24 is the neutralizing electrode, 25 is the positively charged secondary ions, 26 is the negatively charged secondary ions, and 27.28 is the fast atom.

Claims (1)

[Claims] In a secondary ion mass spectrometer consisting of an ion source for emitting primary ions, an analysis sample, and a quadrupole mass spectrometer,
Between the exit slit of the quadrupole mass spectrometer and the secondary electron multiplier tube, there is a neutralization electrode connected to an accelerating power source for positively charged secondary ions, and a neutralizing electrode connected to an accelerating power source for negatively charged secondary ions. A secondary ion mass spectrometer characterized in that a neutralizing electrode is disposed facing each other and a magnetic field for removing secondary electrons is applied between these electrodes.