JPS62128426A - Secondary ion mass analyzer - Google Patents

Abstract

PURPOSE:To check a fall in the secondary ion separation capacity by providing a means of magnetic field generation generating the magnetic field almost parallel to a sample surface for preventing electrons from being incident to the ion detection part. CONSTITUTION:A large amount of secondary electrons together with secondary ions 4 is emitted from a sample 3 for analysis given an impact of a primary ion beam. Since the magnetic field 41 is parallel to the surface of the sample 3, secondary electrons are not incident to an ion resonance field 12 being given deflection in the direction deviating from an incident direction to an incident slit 5. Naturally, also secondary ions 4 are deflected by the magnetic field 41 but since their mass is extremely large as compared with electrons, a degree of deflection is minute so that an influence of the magnetic field is negligibly small. Accordingly, the secondary electrons emitted from the sample for analysis can be prevented from being incident to a mass analyzer for being able to check a fall in a separation capacity of the secondary ion mass analysis.

Description

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

<Background Art> Figure 3 shows that the present inventors have already filed a patent application (Japanese Patent Application
1195) is shown. In the figure, l is an ion source, 2 is a primary 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, 12 is an ion resonance field, 13
is the power supply, 21.22 is the secondary electron multiplier, 23, 24, 2
5, 26 are DC high voltage power supplies, 27, 28 are load resistors, 29
．． 30 is a DC high voltage blocking capacitor, 31 and 32 are amplifiers, and 33 and 34 are positively and negatively charged secondary ions, respectively. 5, 6, 7, and 12 constitute an ion analysis system of a four-electrode mass spectrometer. The figure (bl is a sectional view taken along line A-A' in figure (a)).The operation is as follows.

When 5 to 10 KeV ions (this is the -order ion beam 2) emitted from the ion source 1 bombard the analysis sample 3, positively and negatively charged secondary ions 4 are emitted from the analysis sample 3. These secondary ions enter a four-electrode mass spectrometer and are analyzed. That is, the ion resonance field 1 passing through the entrance slit 5 and surrounded by the four cylindrical electrodes 6
The secondary ions 4 that are incident on the secondary ions 2 are caused by a high-frequency electric field in which a DC electric field and an AC electric field are superimposed, which is applied by a power source 13, and only those having masses suitable for the resonance conditions determined by the electric field strength, frequency, and mass of the ions are Fly in a stable orbit,
The light will be emitted from the emission slit 7. On the other hand, secondary ions with a mass that is not suitable for the above resonance conditions are in the ion resonance field 1.
Dissipate cloud dissipation while flying 2.

Among the secondary ions that have passed through the exit slit 7, the positively charged secondary ions 33 are accelerated by the DC high voltage power supply 25.
It enters the secondary electron multiplier tube 21, becomes an electric signal, appears at the load resistor 27, and passes through the capacitor 29 to the amplifier 31.
is amplified. Among the secondary ions that have passed through the exit slit 7, negatively charged secondary ions 34 are accelerated by the DC high voltage power supply 26, enter the secondary electron multiplier 22, become an electrical signal, and appear on the load resistor 28. The signal is amplified by an amplifier 32 via a capacitor 30. Power supplies R23 and R24 are power supplies for driving the secondary electron multiplier tubes 21 and 22, respectively.

<Problems to be Solved by the Invention> In the secondary ion mass spectrometer described above, a large amount of secondary electrons are emitted from the analysis sample 3 that has been bombarded by the -order ion beam 2, in addition to the secondary ions 4. However, this mixes with the secondary ions 4 and enters the ion resonance field 12. Therefore, a problem arises in that dense empty rIRTi charges are formed in the ion resonance field 12, resulting in a decrease in the separation ability of secondary ions.

An object of the present invention is to provide a method for removing secondary electrons using a magnetic field in order to prevent deterioration of secondary ion separation ability due to contamination of secondary electrons.

Means for Solving the Problems〉 The configuration of the present invention to achieve the above object includes an ion source for emitting a secondary ion beam, an analysis sample, and a mass spectrometer, and also has a configuration that can be used as an ion detection section of the mass spectrometer. Equipped with a power source for accelerating charged secondary ions and a secondary electron multiplier for detecting the same, and a power source for accelerating negatively charged secondary ions and a secondary electron multiplier for detecting the same, the secondary electron multiplier for positive and negative charges is provided. A secondary ion mass spectrometer that simultaneously measures ions is characterized in that a magnetic field generating means for generating a magnetic field substantially parallel to the surface of the sample is provided to prevent electrons from entering the ion detection section.

The main purpose of the present invention is to apply a magnetic field parallel to the surface of the analysis sample to bend the flight trajectory of secondary electrons emitted from the analysis sample and prevent them from entering the four-electrode mass spectrometer. The present invention is different from the conventional technology in that it includes a magnetic field generating means.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to FIG.

As shown in FIG. 1, a magnetic field 41 parallel to the surface of the analysis sample 3 is generated by a magnetic field generating means 1 (not shown), and the rest is performed using the secondary ion material analyzer shown in FIG. It has a similar configuration. The operation is as follows.

From the analysis sample 3 that has been bombarded by the secondary ion beam 2,
A large amount of secondary electrons are emitted simultaneously with the secondary ions 4. Since the magnetic field 41 is parallel to the surface of the sample 3, the secondary electrons are deflected away from the direction of incidence into the entrance slit 5 and do not enter the ion resonance field 12. Naturally, the secondary ions 4 are also deflected by the magnetic field 41, but since their mass is extremely large compared to electrons (the degree of deflection is minute and the magnetic field 41
1's shadow VJl is so small that it can be ignored. When considered quantitatively, the results are as follows.

FIG. 2 shows the circular orbit radius (Lamar radius) of charged particles in a magnetic field.

The secondary ions and secondary electrons emitted from the analysis sample 3 in FIG. 1 both have a kinetic energy U of about 50 eV.

According to Figure 2, for example, in the case of a hydrogen ion with a mass number of 1, the orbital radius r, -=100 cm in a 100er magnetic field, while the electron quality l is about 172 cm for the hydrogen ion.
000, so the orbital radius is 1 of the hydrogen ion orbital radius.
74 ((r, = 2.5 am). Therefore, 10
While the 0er magnetic field can prevent secondary electrons from entering the mass spectrometer, there is no problem because the orbital radius of other ions C, which have a larger mass than the hydrogen ions, is even larger than that of the hydrogen ions.

In the above embodiment, the magnetic field 41 was parallel to the surface of the analysis sample 3, but it does not necessarily have to be completely parallel (
, as long as they are approximately parallel. In other words, any magnetic field that has a component parallel to the surface of the analysis sample 3 is sufficient.

<Effects of the Invention> As specifically explained based on the embodiments above, by applying a magnetic field, it is possible to prevent secondary electrons emitted from an analysis sample from entering the mass spectrometer, so secondary ion mass spectrometry is possible. This has the advantage of preventing a decrease in resolution.

[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)
B-B'14. % cross-sectional view, Figure 2 is a graph showing the relationship between the orbital radius of a charged particle moving in a magnetic field and the kinetic energy of the particle, Figure 3 (al is a schematic diagram of the top secondary ion mass spectrometer, Figure fb) is the same figure (A-A in the text
'It is a line cross-sectional view. In the drawing, 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, 12 is an ion resonance field, 15 is a power source, 2
1.22 is a secondary electron multiplier, 23, 24, 25, 26 is a DC high voltage power supply, 27, 28 is a load resistor, 29.30 is a DC high voltage blocking capacitor, 31.32 is an amplifier, 3
3 is a positively charged secondary ion, 34 is a negatively charged secondary ion, 41
is the magnetic field.

Claims (1)

[Claims] Equipped with an ion source for emitting a primary ion beam, an analysis sample, and a mass spectrometer, a power source for accelerating positively charged secondary ions as an ion detection part of the mass spectrometer, a secondary electron multiplier for detecting the same, and a negative charge In a secondary ion mass spectrometer that is equipped with a power source that accelerates secondary ions and a secondary electron multiplier that detects them, and that measures positively and negatively charged secondary ions at the same time, it is approximately parallel to the surface of the sample. 1. A secondary ion mass spectrometer, comprising a magnetic field generating means for generating a magnetic field to prevent electrons from entering the ion detection section.