JPS6153825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for analyzing a sample by exciting a sample with a charged particle beam and analyzing a secondary particle beam emitted from the sample. Concerning improvements to the part that performs energy analysis of particle beams.

When a sample is bombarded with an electron beam or an ion beam, a variety of information about the sample can be obtained by performing energy analysis, mass spectrometry, etc. on particle beams such as electrons and ions emitted from the sample. For example, when a sample is bombarded with an electron beam, atoms on the sample surface are excited and so-called Auger electrons are emitted. Measuring the energy of this Augier electron reveals the type of atom that emitted the Augier electron, and quantitatively detecting the Auger electron with a specific energy determines the density of the atom that emitted the Augier electron, that is, the content of a specific element on the sample surface. I understand.

FIG. 1 shows an example of a currently proposed comprehensive analytical device for performing the above-mentioned type of analysis. O is a source of electrons and ions, and either particle is emitted by switching. A is an accelerating electrode, L is an electron lens that focuses these charged particle beams onto the sample surface, D is a deflection electrode that scans the sample surface with the particle beam, and S
is the sample. The sample S is set at an angle so that the generated particle beam can easily enter the subsequent analysis section. 1 is the particle beam irradiation point on the sample S, 2 is the entrance slit of the energy analyzer 3, and l is an electron lens for focusing the image of the point 1 on the sample onto the slit 2. The energy analyzer 3 is a double hemispherical shell,
A voltage is applied between each hemisphere, and an electric field is formed between the hemispheres in the radial direction. Among the charged particles that entered this double spherical shell through slit 2, particles with a specific energy corresponding to the strength of the electric field travel in a group of trajectories whose center orbit is an arc passing through the middle of the double spherical shell. Particles that move along the spherical shell and have other energies that are concentrated on the exit slit 4 hit the spherical shell or collide at a point outside the exit slit 4. In this way, the energy analyzer 3 separates and extracts particles with a specific energy. The particle beam passing through the energy analyzer 3 and exiting from the exit slit 4 is focused again onto the entrance slit 11 of the mass spectrometer 5 by the lens ^l1 . The mass spectrometer 5 is a quadrapol type,
Only particles with a specific mass number go straight through the exit slit 6.
The particle beam can pass through the particle beam detector 7 and be detected. Reference numeral 14 denotes a particle beam detector placed laterally between the energy analyzer 3 and the mass spectrometer 5. When only energy analysis is performed, the particle beam exiting the energy analyzer is detected laterally by the repulsion electrode 12. It is then detected by the detector 14.

The present invention is to improve the energy analyzer part of the apparatus shown in FIG. The direction of the energy analyzer and the direction of the particle beam exiting the energy analyzer are made parallel (orthogonal in the conventional example shown in Figure 1), thereby simplifying the work and assembly of the entire device and improving the accuracy of the device. It is in.

The conventional energy analyzer shown in Figure 1 uses a double hemispherical shell, but let us consider the case where an appropriate voltage is applied between the double spherical shells, which are cut into a smaller area than the hemisphere, as shown in Figure 2. . In this case, let P and Q be the intersection of the straight line P for charged particles
The voltage applied to the double spherical shell can be selected so that the point is the source of the charged particle beam and the point Q becomes its image. The present invention takes advantage of this relationship. The present invention will be explained below with reference to Examples.

FIG. 3 shows an embodiment of the present invention. The optical system of the charged particle beam that excites the sample is shown in a simplified manner. Also, parts corresponding to the configuration in FIG. 1 are given the same reference numerals. B is an excitation charged particle beam that irradiates the sample S, and 1 is the irradiation point. The energy splitting device 3 is a double spherical shell that is cut into the hemisphere by θ (20° to 40°) at the center angle, and the tangent at the left end of the double spherical shell to the great circle that passes through the middle of this double spherical shell. is sample S
Passing through point 1 above, the right end surface of the double spherical shell is beam B
It is fixed so that the direction perpendicular to the double spherical shell, that is, the tangent at the right end of the spherical shell of the great circle passing through the middle of the double spherical shell, is parallel to the beam B. As is clear from the figure, if the great circle passing through the middle of the double spherical shell is extended as an arc on the left side, it will contact beam B, and the point of contact M will be located on the extension of the horizontal plane of the right end surface of the double spherical shell. It is a relationship. Since point 1 on the sample S is a point source of the secondary particle beam, this point corresponds to the position of the entrance slit of the energy analyzer 3 without using a separate slit, and as shown in Fig. 2. This corresponds to point P, and among the charged particles emitted from point 1 on the sample, those with a specific energy are the extension of the straight line connecting point 1 and the spherical center C of the double spherical shell of the energy analyzer. The energy is concentrated at the intersection point Q between and the straight line that exits the energy splitting device 3 and extends vertically downward. An exit slit 4 of the energy analyzer 3 is located at point Q. This slit 4 also serves as an entrance slit for a subsequent quadrupole mass spectrometer 5. The quadrupole mass spectrometer consists of four parallel electrodes extending in the vertical direction. Direct current voltage and high-frequency alternating voltage of opposite polarity are applied to adjacent electrodes in a superimposed manner, and the charges incident parallel to the electrodes are Among the particles, only particles with a specific mass number travel straight and particle beams with other masses are emitted. Reference numeral 6 represents an exit slit for taking out the particle beam that has come straight forward, and 7 represents a charged particle detector. If you eliminate the DC component of the voltage applied to the four electrodes in a quadrapol mass spectrometer and use only the AC component, the mass spectrometry function will be lost, but the charged particles that are incident through the slit 4 and have a tendency to diverge will not diverge and will proceed almost straight. It is possible to direct it to the exit slit 6. Therefore, when only energy analysis of charged particles is performed and mass analysis is not necessary,
It is sufficient to cut off the DC component of the voltage applied to each electrode of the mass spectrometer 5, and the detector 7 can be used as is.

Comparing the device of the present invention with the conventionally proposed device shown in FIG. is no longer necessary, and the lens l is also no longer necessary, simplifying the device configuration. In addition, since the direction of beam B of the sample excitation line and the beam after the exit of the energy spectrometer are parallel, the entire device can be fabricated and assembled using one reference plane and the direction perpendicular to it as the processing direction, making the work easy and simple. High accuracy can be obtained, and the resulting device can easily maintain its accuracy against gravity (with the configuration shown in Figure 1, it is necessary to provide sufficient rigidity against deflection due to the device's own weight).
becomes. By arranging an energy analyzer and a Quadrapole mass spectrometer in series, the DC component of the voltage applied to each electrode of the Quadrapole mass spectrometer can be added or subtracted separately from the AC component. is used only to make the incident beam go straight without causing it to diverge, omitting the lens and repulsion electrode between the energy analyzer and the mass spectrometer, and allowing the energy analyzer and the mass spectrometer to share a single particle detector. This makes it possible to further simplify the configuration of the entire device.

[Brief explanation of the drawing]

Fig. 1 is a vertical side view of an analyzer that has already been proposed, Fig. 2 is a longitudinal side view of a double spherical shell energy analyzer for explaining the principle of the present invention, and Fig. 3 is an apparatus according to an embodiment of the present invention. vertical side view. B...excitation ray beam, S...sample, 3...energy analyzer, 5...quadrapol mass spectrometer, 6...exit slit, 7...charged particle detector.

Claims (1)

[Scope of Claims] 1. An energy analyzer consisting of double spherical shells that form an electric field between them in an analyzer of the type that irradiates a sample with excitation rays and analyzes secondary particle beams emitted from the sample. It is cut slightly from the hemispherical shape so that the longitudinal section is fan-shaped, and the exit side end face of the energy analyzer is perpendicular to the direction of the excitation line beam, and the great circle passing through the middle of the double spherical shell at the entrance side end face is made. A sample analysis device using a charged particle beam, in which the sample is located at the intersection of a tangent and the excitation beam. 2. A quadrupole mass spectrometer is placed on the exit side of the energy analyzer consisting of a double spherical shell, using the exit slit of the analyzer as the inlet slit,
2. A sample analysis device using a charged particle beam according to claim 1, wherein a DC voltage can be applied and subtracted separately from an alternating voltage to each electrode of the mass spectrometer.