JPS62226551A - Mass spectrograph - Google Patents

Abstract

PURPOSE:To make highly accurate mass spectrometry attainable, by interposing a set of quartered electrodes between a focusing lens and a beam limiting aperture, and regulating an ion beam optical system on the basis of an ion beam quantity to be irradiated to these quartered electrodes and another ion beam quantity to be reached to a smaple. CONSTITUTION:A beam monitor electrode 40 consists of a set of quartered electrodes 41-44, and an opening 45, where an ion beam is enough to pass through, is formed in the center. When the ion beam is irradiated to these equally divided electrodes 41-44, an electric current flows into each of these electrodes 41-44 in proportion to this irradiated quantity, and the current value at this time is detected by ammerters 71-74 for each electrode. With this constitution, ion beam quantities to be irradiated to each of these eqally divided electrodes are requlated so as to be equalized whereby optical axis alignment is carried out, and under this state, furthermore another ion beam quantity to be reached to a sample is regulated so as to become the maximum, thereby having a focal point of a focusing lens situated on an optical axis.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a mass spectrometer used in the analysis of solid samples, and particularly relates to a mass spectrometer that is used for irradiating the sample with a primary ion beam. This invention relates to improvements in primary ion beam optical systems.

(Prior art) This type of conventional mass spectrometry analyzer uses an ion gun to emit a primary ion beam such as Ar ions, and to convert the primary ion beam into an ion beam optical system consisting of a focusing lens, a beam limiting aperture, etc. Secondary ion mass spectrometers are common, which irradiate a sample through a system, detect secondary ions generated from the sample, and conduct mass analysis. In this device, it is necessary to efficiently irradiate the sample with the primary ion beam, and for this purpose, the optical axis of the focusing lens and the optical axis of the beam limiting aperture must match, and the focal point of the focusing lens must be aligned with the optical axis of the beam limiting aperture. It is desirable to be located on the axis. However, due to dimensional tolerances in structural design, assembly tolerances, etc., the above-mentioned deviation of the optical axis was unavoidable.

Therefore, in the past, the optical axes were aligned based on the ion beam 1 reaching the sample, but when the ion beam optical system includes an electrode that deflects the beam, alignment adjustment requires extremely skill and is very difficult. It took a lot of effort and time.

In addition, once the optical axis has shifted, it is difficult to readjust it.
There was a risk that the unstable situation would continue for a long time. Taking these points into consideration, a method has been proposed to improve efficiency by adjusting the current flowing into a shield plate that shields the electric field of the beam deflection electrode, but even in this case, optical axis alignment adjustment is not necessary. This was very difficult, and it was not possible to sufficiently improve efficiency.

(Problems to be Solved by the Invention) The present invention has been made based on the above-mentioned circumstances, and it is possible to efficiently irradiate a sample with a primary ion beam by simple and short-time adjustment. The purpose of the present invention is to provide a mass spectrometer capable of highly accurate mass spectrometry.

[Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems and achieve the purpose, the present invention has the following features:
An equally divided electrode is interposed between the focusing lens and the beam limiting aperture, and the focusing lens The ion beam optical system is adjusted so that the optical axis of the ion beam and the optical axis of the beam limiting aperture coincide with each other, and the focal point of the focusing lens is located on the coincident optical axis.

(Function) By taking such measures, optical axis alignment is performed by adjusting the amount of ion beam irradiated to each equally divided electrode to be equal, and in this state, the ion beam can further reach the sample. The focal point of the focusing lens is positioned on the optical axis by adjusting the amount of ion beam to be maximum.

(Example) FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

In the figure, 101.1 is an ion gun that emits a primary ion beam such as Ar ions, and has a filament (cathode) 11. It is composed of an intermediate electrode 12, an anode 13, and an extraction electrode 14 that determines the direction of extraction of the ion beam. Reference numeral 20 denotes a focusing lens that focuses the ion beam emitted from the ion @ 10, and the ion beam focused by the focusing lens 20 is transmitted through a pair of X-direction deflection types ti31a and 31b and a pair of Y-direction deflection tubes. 1i32
It is deflected by a deflection mechanism 30 consisting of a and 32b. 40 is a beam monitor electrode,
It consists of electrodes 41 to 44 divided into four equal parts, and an opening 45 sufficient for the passage of the ion beam is formed in the center.

The arrangement of the equally divided electrodes 41 to 44 corresponds to the adjustment direction of the axis alignment direction adjusting screws (not shown) provided on the seven nodes 13 and the extraction electrode 14 in the ion gun 10. 50 is a beam limiting aperture;
An opening 51 is formed in the sample 60 to guide the ion beam. A pair of beam deflectors are provided near the aperture 51 to deflect the ion beam so that the optical axis of the ion beam passing through the aperture 45 of the beam monitor electrode 40 passes on the central axis of the aperture 51. Electrodes 52a, 52b
and these beam deflection electrodes 52a.

A shield plate 53 is provided to shield the electric field 52b.

On the other hand, each of the equally divided electrodes 41 to 41 of the beam monitor electrode 40
44, ammeters 71 to 74 are respectively connected as shown in FIG. It is intended to be detected. Also, Figure 2 (
As shown in b), the sample 60 is also equipped with an ammeter 75 for detecting the current layer generated by ion beam irradiation.
is provided.

In this embodiment configured in this way, the ion gun 1
When a primary ion beam is emitted from zero, the primary ion beam is focused by a focusing lens 20, and then deflected by a deflection mechanism 30.
the respective apertures 45, 51 of the beam monitoring electrode 40 and the beam limiting aperture 50.
and reaches the sample 60. Then, sample 60
Since secondary ions are generated, mass spectrometry of the secondary ions is performed by a pawnshop analysis means (not shown).

Here, in order to efficiently irradiate the sample 60 with the primary ion beam, the ion beam system is adjusted, that is, the optical axis of the focusing lens is aligned with the optical axis of the beam limiting aperture, and the focal position of the focusing lens is adjusted. is required. These adjustments are made as follows. When each of the equally divided electrodes 41 to 44 of the beam monitor electrode 40 is irradiated with an ion beam, each of the electrodes 41 to 44 is irradiated with the ion beam in proportion to this irradiation m.
44, and the current value at this time is detected by each ammeter 71-74. Now, the indicated value of the ammeter 71 is the maximum, and the following indicated values are 74>72
>73, it can be seen that the optical axis of the ion beam that has passed through the focusing lens 20 is shifted toward the electrode 41 side. Therefore, by shifting the optical axis toward the electrode 43 using the adjustment screws provided on the anode 13 and the extraction electrode 14 while monitoring the indicated values of each of the ammeters 71 to 74, the indicated values of each of the ammeters 71 to 74 can be adjusted. When they become equal, the optical axis of the ion beam focused by the focusing lens 20 coincides with the optical axis of the beam monitor electrode 40 and, by extension, with the optical axis of the beam limiting aperture 50.

On the other hand, when the optical axes are aligned and the focal point of the focusing lens 20 is located on the aligned optical axes, the ion beam irradiation tJJm on the sample 60 increases. Therefore, the indicated value of the ammeter 75 provided on the sample 60 is monitored, and the focusing lens 20 and the deflection mechanism 30 are adjusted so that this indicated value becomes maximum.

Thus, according to this embodiment, the adjustment of the optical axis of the focusing lens 2° and the optical axis of the beam limiting aperture and the focal position adjustment of the focusing lens are performed by the current flowing into each of the equally divided electrodes 41 to 44 of the beam monitor electrode 40. This can be done while monitoring the amount of current that changes in proportion to l and the ion beam j reaching the sample 60. Therefore, it can be carried out reliably and in a short time. In addition, the beam monitor electrode 4
Since the arrangement of each of the light splitting electrodes 41 to 44 of 0 coincides with the optical axis adjustment direction, anyone can easily adjust the arrangement. Therefore, it becomes possible to stably maintain an optimal beam irradiation state over a long period of time.

Note that the present invention is not limited to the above embodiments.

For example, in the embodiment described above, ammeters 71 to 75 were provided to each of the equally divided electrodes 41 to 44 of the beam monitor electrode 40 and to the sample 60, but as shown in FIG. and a current detector 81 on the sample 60, respectively.
- 85 are provided, and the detection outputs of these current detectors 81 - 85 are introduced into a monitor control section 86 .
Accordingly, each of the detection outputs may be displayed on the monitor device 87 in an analog or digital manner. Furthermore, in the above embodiment, the arrangement of the equally divided electrodes 41 to 44 of the beam monitor electrode 40 is made to match the direction adjustment screw for axial alignment between the anode 13 and the extraction electrode 14, thereby simplifying the adjustment. As shown, the equally divided electrodes 41 to 44 are connected to each pair of electrodes 31a and 31b of the deflection mechanism
Beam adjustment can also be made relatively easily by matching the directions of 32a and 32b or by shifting them by 45 degrees. Further, in this case, each pair of electrodes 31a and 31b of the deflection mechanism 30
The potentials applied to the electrodes 32a and 32b can be easily set by monitoring the ammeters 71-74 connected to the equally divided electrodes 41-44. Further, in the above embodiment, the case where the beam monitor electrode 40 is divided into four parts is shown, but the same effect can be obtained by dividing the beam monitor electrode 40 into three equal parts, five equal parts or more.

Of course, many other modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, equally divided electrodes are interposed between the focusing lens and the beam limiting aperture, and the ion beam is irradiated to each of these equally divided electrodes. and the amount of ion beam reaching the sample such that the optical axis of the focusing lens and the optical axis at the beam limiting aperture coincide, and the focal point of the focusing lens is located on the coincident optical axis. By adjusting the ion beam optical system, the sample can be efficiently irradiated with the primary ion beam by simply adjusting the flight time, providing an 'Rffi analyzer that can perform highly accurate mass spectrometry. can.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) and 2(b) are diagrams for explaining the adjusting means in the same embodiment, and FIG. 3 is a diagram showing the adjusting means in the present invention. It is a system diagram showing a modification. 10... Ion gun, 11... Filament, 12.
... Intermediate electrode, 13... Anode, 14... Extraction electrode, 20... Focusing lens, 30... Deflection mechanism, 4
0... Beam monitor electric bridge, 41-44... Equally divided electrode, 50... Beam limiting aperture, 52... Beam deflection electrode, 53... Shield plate, 60... Sample,
71-75...Ammeter, 81-85...Current detector, 86...Monitor system 01]\i placement, 87...Monitor device. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] In a mass spectrometer that performs mass analysis of a sample by irradiating the sample with a primary ion beam emitted from an ion gun through an ion beam optical system consisting of a focusing lens, a beam limiting aperture, etc., the focusing lens and the beam limiting aperture are provided. Interpose equally divided electrodes between the
Based on the amount of ion beam irradiated to each of these equally divided electrodes and the amount of ion beam reaching the sample, the optical axis of the focusing lens is aligned with the optical axis of the beam limiting aperture, and the focusing lens is A mass spectrometer characterized in that the ion beam optical system is adjusted so that focal points of lenses are located on the coincident optical axes.