JPS5947423B2 - Solid surface analysis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ion source device for generating positive ions and negative ions equipped with a quadrupole magnetic field lens group for the purpose of separating electrons, negative ions, and positive ions, and an ion source device equipped with the above-mentioned ion source. This invention relates to a solid state analyzer.

FIG. 1 shows the configuration of a conventional dual plasmatron ion source device. In the figure, electrons 2 emitted by heating the cathode 1 and positive ions 5 accelerated by the voltage applied between the cathode 1 and the intermediate electrode 3 by the power source 4 bombard the cathode 1. The secondary electrons 6 generated thereby are accelerated by the power source 4, collide with gas molecules, and are ionized. Due to this ionization, 5 more positive ions
, negative ions 7, electrons 8, etc. are generated. When the pressure of the discharge body is in the range of about 10-3 torr to 10 Torr, charged particles such as positive ions 5, negative ions T, and electrons 2, 6, and 8 generated by this ionization form plasma 9. Then, this plasma 9 is ejected from the intermediate electrode 3 in the direction of the anode 10.

Here, a magnetic field 12 excited by a magnet 11 exists between the intermediate electrode 3 and the anode 10, thereby focusing the plasma 9 and increasing its density. Conventionally, ions were extracted from the plasma 9 ejected from the anode 10 and used as an ion source. Figure 2 shows the first
1 shows a conventional example of a solid-state analyzer equipped with the dual plasmatron ion source device shown in the figure as a primary ion source.

When using positive ions from an ion source as primary ions, the anode 10 is set to a high positive voltage and the extraction electrode 13 is set to a low voltage. Only the ions 5 pass through the extraction electrode 13. However, the negative ions 7 and the electrons 2, 6, and 8 generated in the above processes are suppressed by the voltage applied between the extraction electrode 13 and the anode 10 by the power source 14, and cannot pass through the extraction electrode 13. Therefore, only positive ions 5 can be extracted purely. The voltage applied by the power source 14 acts on the positive ions 5 as a primary accelerating voltage, and the accelerated positive ions 5 are focused by the electrostatic lens 15 and then impact the sample 16.

Due to the impact of the positive ions 15, secondary ions IT are released from the sample 16. Secondary ion 17 is a power source (not shown)
The ions are accelerated by a voltage applied between the sample 16 and the secondary ion extraction electrode 18 , subjected to mass spectrometry in the magnetic field 19 , and detected by the ion collector 20 . On the other hand, when using negative ions T, a high positive voltage is applied to the extraction electrode 13 with respect to the anode 10 by the power source 14.

In this way, the positive ions 5 are suppressed by the electric field between the anode 10 and the extraction electrode 13, and the extraction electrode 13
cannot pass through, but negative ions T and each electron 2, 6, 8
is the anode 10 and the extraction electrode 1 opposite to the positive ion 5
3, and can pass through the extraction electrode 13. However, since each negative ion T contains electrons 2, 6, and 8, this becomes an obstacle when ionizing a solid purely by negative ion bombardment, and these electrons 2, 6, and 8 are mixed together.
6 and 8 impact the surface of the sample 16, causing temperature rise and contamination of the sample. Further, when using negative ions, it is necessary to provide the acceleration power source 14 with extra power due to the emission of each electron 2, 6, and 8.

For example, the power required for the acceleration power source 14 is calculated as follows. Under certain operating conditions, the ion current due to positive ions 5 is 10-5 A, and the ion current due to negative ions T is 1
0-6A, ion current 10-2 due to each electron 2, 6, 8
A is ejected from the ion source. Assuming that the primary ion acceleration voltage 14 is 104V, the power of the primary ion acceleration power supply required when using positive ions 5 is the product of 10-5A and 104V, which is 0. It is IW. However, when using negative ions T, since electrons 2, 6, and 8 are added to negative ions T, the power 14 of the primary ion accelerating power source is (10-6 +10
-2) The product of A and 104v, 100W, is required. Here, if negative ions 7 and electrons 2, 6, and 8 can be distinguished, then when only negative ions T are used, the power of the power source 14 is 10-6
It should be possible to reduce it to A×104V=0.0IW.
Conventionally, it has been impossible to extract only negative ions T using a single Duoplasmatron ion source.

However, by incorporating a magnet and an electrode into the ion source, it was revealed that negative ions and electrons could be separated using a magnetic field, and an application was filed earlier. That application utilized the fact that the amount of deflection of negative ions and electrons is significantly different for the same magnetic field strength. However, since it did not utilize the focusing properties of the magnetic field, the negative ion beam remained spread out after being deflected by the magnetic field. For this reason, when the beam is narrowed down later, the intensity does not become high, or the beam cannot be narrowed down sufficiently. Therefore, if it were possible to separate electrons and negative ions and simultaneously focus the negative ions, it would be possible to focus the beam narrowly while keeping the beam intensity high. This patent application has achieved this point. The principle and examples will be explained below. 3 and 4 are diagrams explaining the principle of the ion source section of the present invention.

FIG. 3 is an explanatory diagram of the operation of the positive ion source, and FIG. 4 is an explanatory diagram of the operation of the negative ion source, which separates negative ions and electrons and focuses the negative ions. In both figures, magnetic poles 21, 22, 23 constitute a quadrupole lens group.

A cross-sectional view of the magnetic poles 21 and 23 is shown in FIG. 5, and a cross-sectional view of the magnetic pole 22 is shown in FIG. Reference numeral 29 denotes a voltage generating power source for extracting positive ions or negative ions and electrons from the plasma generating means.

When positive ions are required, a high voltage is applied to the anode 10 relative to the electrode 20. Conversely, when negative ions are required, the anode 10 is set to a low potential. In FIGS. 3 and 4, a magnetic field exists in the space of the opposing electrodes 21, 22, and 23 in a direction approximately perpendicular to the plane of the paper. In Figures 3 and 4, negative ion T, positive ion 5 and electrons 2, 6, 8
The orbit of is shown enlarged more than usual. That is,
The aperture angle of these beams is set to be 5 to 10 times larger than the actual one. The operation will be explained below with reference to both figures.
In FIG. 3, a negative potential is applied by a power source 29 to an extraction electrode 28 with respect to an anode 10 of a plasma generation source.

At this time, only the positive ions 5 can pass through the electrode 28. Even if the negative ions and electrons are ejected from the anode 10, they are returned to the anode 10 due to the above-mentioned negative potential.
The positive ions 5 are focused in the horizontal and vertical directions by a magnetic quadrupole lens group and imaged onto the electrode 24 . The ion beam 5 that has passed through V) 28 can be focused into a point at the position 24 by the three sets of lenses shown in FIG. The one shown in FIG. 4 is used as a negative ion source.

The difference from FIG. 3 is that the potential 29 of the power source applied to the electrode 28 is reversely positive with respect to the anode 10 of the plasma generation source. The positive ions ejected from the anode 10 are immediately returned by this potential and reach the anode 10. On the other hand, negative ions 7 and electrons 2 ejected from the anode 10
, 6 and 8, the negative ions are focused vertically and horizontally by a group of quadrupole lenses and pass through the electrode 24. on the other hand,
The mass of an electron is less than 1/2000 that of a negative ion.
Therefore, when the magnetic field is strong enough to focus negative ions, the electrons move around the magnetic field with a small orbital radius and are trapped by the magnetic pole 21. Therefore, only negative ions can pass through the electrode 24. As explained above using FIG. 3 and FIG. 4, only the sign of the power supply voltage 29 is different in positive and negative, but because of almost the same structure, V, as a positive ion source or a negative ion source, does not contain electrons. Moreover, these ion beams can be used in a narrowly focused state. FIG. 7 shows another negative ion source configuration of the present invention in which the shape of the electrode 24 is changed. The operation is similar to that described in FIGS. 3-4. However, the electrons 2, 6, and 8 collide with the cylindrical inner walls of the electrodes 24 and 28 and disappear. Generally, the role of the electrode 24 is considered to be to apply the following ion accelerating electric field and for the differential exhaust hole.

FIG. 8 is an explanatory diagram of a solid-state analyzer using the ion source according to the present invention shown in FIGS. 4 and 3.

In FIG. 7, when using positive ions 5 from an ion source, a power source 29 is used to connect an electrode 28 to a dianode 10.
A negative potential is applied to the electrode 24, and a negative ion accelerating voltage is applied to the extraction electrode 13 and the electrode 24 by the power source 14.
Only the positive ions that have passed through the electrode 24 are accelerated by the accelerating electric field, and then focused by the electrostatic lens 15 on the sample 1.
Shock 6. At this time, the secondary ions 17 emitted from the sample 16 are accelerated and then mass separated by the fan-shaped magnetic field 18.
Detected by the ion collector 19. Further, when using the negative ions 7, a potential having the sign of the negative ion source is applied to the voltage 29. Further, an ion accelerating voltage that is more positive than the electrode 24 may be applied to the extraction electrode 13 by the power source 14. The negative ions 7 are accelerated by this accelerating electric field, and the Seiden lens 15
After being focused at , it collides with the sample 16. Due to this impact, secondary ions 17 are emitted from the sample 16 in the same way as when the positive ions 5 collide with the sample 16. This secondary ion 7
are mass-separated by the fan-shaped magnetic field 18 and then detected by the ion collector 19. When using the negative ions 7 in this way, the electrons 2, 6, and 8 generated in various processes are affected by the action of the magnetic quadrupole lens group as shown in Figure 4.
It cannot pass through the electrode 24. Therefore, only negative ions 7 containing no electrons can be taken out from the electrode 24. Therefore, it is possible to ionize a solid only by negative ion bombardment. The effects of extracting negative ions from plasma using a quadrupole lens group are: (1) only negative ions can be separated without electrons, and (2) the negative ion beam can be separated both horizontally and vertically. It can be focused to a point.

(3) It is possible to perform sufficient differential pumping, and (4)
) The ion source can be made smaller. Here (1
)} and (2) have already been explained. (
In item 3), the pressure of the cathode 1, intermediate electrode 3, and anode 10 in FIG. 1 is 10-1T0rr when in use. Conventionally, differential pumping was performed at the anode 10,
After that, I kept it at 10-7 TOrr. However, as in the present invention, differential pumping can be performed not only at the anode 10 but also at the electrode 24. Therefore, the exhaust system after the electrode 24 can be downsized. Regarding (4), simply adding a small quadrupole lens group to the conventional dual plasmatron ion source works as a positive and negative ion source, so the overall size can be reduced. In the present invention, effects (1) to (4) can be simultaneously satisfied in the form of a product. Also(
Regarding 2), a numerical comparison can be made as follows. Consider the case of the configuration shown in FIG. 2 as a conventional numerical value. Conventionally, at the position of the electrode 24, when the diameter was 0.4 mm, the negative ions were 2.times.10@-5 A1 and the positive ions were 4.times.10@-5 A.
In the present invention, negative ions are 2.5 x 10-4 A with a diameter of 0.4 mm.
In both cases, the ion current could be increased approximately 12 times to 5×10 −4 A per positive ion. In the conventional method, when the diameter was 0.1 mm, the amount of negative ions was 2×10 −6 A and the amount of positive ions was 4×10 −6 A. On the other hand, in the present invention, when the diameter was 0.1 mm, the negative ions were 2×10 −4 A and the positive ions were 4×10 −4 A. That is, in the present invention, since negative ions and positive ions can be focused by operating the quadrupole lens group, a beam of any desired size can be obtained without sacrificing the ion current. In this regard, in the conventional method, when the beam diameter is reduced simply by mass separation of electrons and ions by a magnetic field, the ion current also decreases rapidly in proportion to the area of the beam. The reality is that we want to extract a large amount of ion beam from the ion source. Since the negative ion current of the present invention can be made about 12 times larger when the beam diameter is 0.4 TnWLφ and about 100 times larger when the beam diameter is 0.1 mmφ than that in the conventional method, it is thought that the field of application thereof will be significantly expanded. Next, the effect of extracting negative ions in the solid-state analyzer equipped with the above-mentioned positive and negative ion source of the present invention will be explained.

The effects of the present invention are as follows: (1) elucidation of the ionization phenomenon caused only by negative ions, and (2) elucidation of the ionization phenomenon caused by electron irradiation (local heating of the sample, adhesion of contaminants to the sample surface, solidification of contaminants, etc.). (3) The ion accelerating power source and capacity can be made smaller (approximately 1/100 of the conventional one); (4) The negative ion current for the same beam diameter is approximately 10 to 100 times smaller than the conventional one. (5) The beam focusability of negative and positive ions is improved (approximately 10
~50 times: positive ions and negative ions are focused into a point at the position of the electrode 24).

Owing to the effects of the present invention described above, solid surface analysis can now be easily performed in the true sense.

In the present invention, a case has been described in which there are three sets of quadrupole lens groups, but two or four sets may be used depending on the required beam conditions. Further, the magnetic poles forming the grooves in the lens group may be a permanent magnet or an electromagnet whose strength can be varied. In the present invention, an example in which the electrode 24 has a hole has been described, but the electrode 24 is formed into a mesh; however, the electrode 24 may have a plurality of holes.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an outline of the configuration of a conventional dual plasmatron ion source, Fig. 2 is an explanatory diagram of a conventional solid-state analyzer equipped with the ion source shown in Fig. 1, and Fig. 3 is an explanatory diagram of the present invention. FIG. 4 is an explanatory diagram of the negative ion operation of the ion source device of the present invention, and FIGS. 5 and 6 are the quadrupole lenses of FIGS. 3 and 4. FIG. 8 is a cross-sectional view of the magnetic poles of the group, and FIG. 8 is a cross-sectional view showing an example of the ion source of the present invention. FIG.

Claims (1)

[Claims] 1 Plasma generation means, means for extracting positive ions or negative ions and electrons from the plasma generation means, and the extracted positive ions or negative ions and electrons are converted into only positive ions or negative ions by a magnetic field type quadruple magnetic lens group. A solid surface analysis device characterized by having a positive and negative ion source with a configuration that separates and focuses ions.