JP2961795B2 - Charged particle energy analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an analyzer using energy analysis of charged particles, and simultaneously measures the distribution of the emission angles of charged particles radially emitted from one point. The present invention relates to an analytical instrument for the purpose.

(Prior art and its problems) Spectroscopy for energy analysis of charged particles, particularly electrons and ions, is used by many people in engineering and science related to solid surfaces, interfaces, thin films, catalysts, and the like. Among them, regarding the spectroscopy of electrons, XPS (X-ray Photoelectron Spe
ctroscopy), UPS (Ultraviolet Photoelectron Spectr)
oscopy) and other analytical instruments are widely used by researchers and engineers in the field. For ion spectroscopy, ISS (Ion Scattering Spectroscopy), RBS (Rathe
rford Back Scattering).

As technologies related to electron spectroscopy and ion spectroscopy add precision, it has become necessary to determine not only the energy but also the direction of travel (angle). Angle-resolved electron spectroscopy and angle-resolved ion spectroscopy The law was born. In ordinary angle-resolved spectroscopy, an excitation source (light, electron, ion, or the like) is applied to a small region of a sample, and energy analysis is performed on charged particles emitted or scattered in a specific direction. In this case, the detection angle is changed by rotating the sample and the energy analyzer around the sample. Therefore, a large amount of time is usually required for the measurement for determining the angle dependence in the energy analysis of charged particles.

In order to overcome such difficulties of angle-resolved spectroscopy of charged particles, several angle simultaneous measurement type electron energy analyzers that simultaneously analyze angle and energy with a specific angle width have been devised. If these are classified according to the setting method of the specific angle width in the simultaneous angle measurement, they are classified into three types as shown in FIG.

Type 1 simultaneously analyzes the energy of charged particles emitted in the range of the solid angle width of Ω. Type 2 performs energy analysis of charged particles emitted in a range of a polar angle width of Θ at a specific azimuth angle φ. Type 3 performs energy analysis of charged particles emitted in a range of an azimuthal width of Φ at a specific polar angle θ. The difference between Type 2 and Type 3 is that Type 2 has an angular width on one plane, while Type 3 has an angular width on a conical surface. These three types of simultaneous angle measurement type energy analyzers have been devised and partially used,
These existing simultaneous angle measurement type energy analyzers have the following problems.

That is, type 1 is the most efficient energy analyzer and is a desirable type, but currently realized energy analyzers are very complicated and expensive, and the measurement control system is complicated and expensive. is there. At present, several types of energy analyzers of type 2 have been realized, but those which have been realized can basically measure only the angular distribution in the same plane. The type 3 energy analyzer is a CMA type energy analyzer (Cylindrical Mirror Analyzer), but the polar angle θ in FIG. 2 is fixed to θ = 42 ゜ 18.5 ′. Although an energy analyzer capable of changing θ has been realized, it is actually used little because the variable range of θ is narrow.

(Means for Solving the Problems) The present inventor has conducted intensive studies in order to solve the above problems, and as a result, in an energy analyzer of an electrostatic concentric spherical type or a coaxial cylindrical mirror type, the center of the spherical surface or the cylindrical shape is considered. The sample and the exit aperture are arranged on the central axis of symmetry passing therethrough, and the entrance and exit are arc-shaped slits centered on the central axis of symmetry, and the entrance slit deflects and shifts charged particles. The present inventors have found that the conventional problems can be solved by mounting the above-mentioned electrode and providing a position-sensitive detector as an electron detector after the exit aperture.

That is, the present invention irradiates the sample with X-rays or particles,
In an energy analyzer of an electrostatic concentric spherical type or a coaxial cylindrical mirror type for analyzing the kinetic energy of charged particles emitted or scattered from the sample, a symmetrical central axis passing through the center of the electrostatic concentric spherical or coaxial cylindrical mirror cylinder is used. The arranged sample and exit aperture, arc-shaped slits for the entrance and exit centered on the symmetry central axis, electrodes for deflecting and shifting charged particles attached to the slit of the entrance, and the exit A charged particle energy analyzer comprising a position-sensitive detector provided as a detector for charged particles at a stage subsequent to the aperture, for causing the charged energy analyzer to translate the entire energy analyzer along the central axis of symmetry. Particle energy analyzer with a moving mechanism of the charged particle energy analyzer, and an exit aperture and position-sensitive detector Charged particle energy analyzer electrodes for performing deflection and acceleration of charged particles having an arcuate slit having a center of symmetry center axis provided in the previous year charged particle energy analyzer between, there is provided a.

(Operation) Hereinafter, the present invention will be described in detail.

According to the charged particle energy analyzer according to the present invention, the function of type 3 in FIG. 2 can be realized, but by providing a mechanism that can change the positional relationship between the energy analyzer and the sample along the central axis of symmetry. , The polar angle θ of type 3 can be selected, and the function of type 2 can be provided.

Fig. 1 shows the principle of operation. That is, of the charged particles emitted or scattered from the minute area of the sample, all the charged particles within the range of the azimuthal angle of Φ at the specific polar angle θ are taken into the entrance slit. The captured charged particles are subjected to energy analysis, and only charged particles having a specific energy exit from the exit slit and are detected by the position-sensitive detector. Here, the energy analyzer is a rotationally symmetric body or a part thereof about the center axis of symmetry, and the sample is set so that the center axis of symmetry coincides with the perpendicular of the sample as shown in FIG. Therefore, the charged particles in the range of Φ are all subjected to the same energy analysis, and the traveling direction of the charged particles coming out of the exit slit is determined by the azimuth when emitted or scattered from the sample. Therefore, the azimuth of charged particles having the same energy is determined corresponding to each position of the position sensitive detector.

The polar angle θ is set by translating the energy analyzer or the sample along the central axis of symmetry and applying an appropriate electrostatic voltage to the deflection electrode attached to the entrance slit. At the same time, the deflection electrode can be supplied with an acceleration or deceleration voltage for adjusting the energy of charged particles entering the entrance slit. Further, as shown in FIG. 4, by attaching an electrode having an arc-shaped slit centered on the symmetric center axis on the trajectory of the charged particle between the exit aperture and the position-sensitive detector, It is possible to prevent a decrease in the detection efficiency of the sensitive detector or to prevent mixing of secondary electrons.

When the type 2 measurement in FIG. 2 is performed in the energy analyzer of the present invention, the sample is made parallel to the central axis of symmetry as shown in FIG. The positional relationship along the central axis of symmetry and the static voltage applied to the deflection electrode attached to the entrance slit may be determined appropriately.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 5 is a schematic diagram of one embodiment of the present invention. In the figure, reference numeral 1 denotes a 120 ° electrostatic concentric spherical energy analyzer having inner and outer spherical surfaces having radii of 45 mm and 55 mm, and 2 denotes a symmetric central axis passing through the center 3 of the spherical surface. Reference numeral 4 in the drawing denotes a sample to be measured, which is set such that the central axis of symmetry 2 coincides with a perpendicular line of the sample. Reference numerals 5, 5 ', 6, and 6' in the figure denote electrodes attached to an arc-shaped entrance slit having a center on the center axis 2 of symmetry. The shape is almost as shown in the figure, and the bold line in the figure is the electrode surface. At this time, the electrodes 5, 5 'have the same voltage as that of the sample 4, and the electrode 6 has about 4 of the difference between the outer spherical voltage of the energy analyzer 1 and the potential on the center orbit of the charged particle orbit 8.
Apply up to a certain voltage. A voltage up to about 40% of the difference between the inner spherical voltage of the energy analyzer 1 and the potential on the central orbit of the charged particle orbit 8 is applied to the electrode 6 '. Orbit 7 from sample 4
The charged particles emitted along are bent by the electrodes 5, 5 ', 6, 6' in a plane including the trajectory 7 and the central axis of symmetry 2 and enter the trajectory 8. That is, the polar angle θ of the measurement is determined depending on where the sample 4 is on the center axis 2 of symmetry, and the charged particles emitted at a certain polar angle θ exit perpendicularly from the exit surface of the entrance slit and enter the trajectory 8. The DC voltage applied to the electrodes 5, 5 ', 6, 6' may be determined. At this time, the range of the azimuth width Φ that can be measured and the polar angle θ that can be set depend on the shape of the electrodes 5, 5 ′, 6, 6 ′. In this embodiment, the azimuth width Φ is 75 ° The angle θ was designed to be in the range of 40 to 90 °.

Further, at the position of θ = 90 °, the surface of the sample is set at the symmetric center axis 2
(4 ′ sample position), the type 2 measurement in FIG. 2 becomes possible. Polar angle at this time Θ
Has a measuring range of 75 °.

In FIG. 5, reference numeral 9 denotes an arc-shaped exit slit having a center on the center axis 2 of symmetry, and reference numeral 10 denotes an exit aperture provided on the center axis 2 of symmetry. The potential of the exit slit 9 and the exit aperture 10 is the same as the potential on the central orbit of 8. Of the charged particles dispersed by the electrostatic concentric spherical energy analyzer 1, only those having a specific energy pass through the exit slit 9 and the exit aperture 10 and are converted into single energy. Numeral 11 in the figure denotes a deflection electrode, which has an arc-shaped slit centered on the center axis 2 of symmetry. Reference numeral 12 denotes a position-sensitive detector, which uses two microchannel plates (MCP) having an effective diameter of about 25 mm. The deflection electrode 11 maintains the same potential as the exit aperture 10, but can apply an acceleration or deceleration voltage to the position-sensitive detector 12. When the accelerating voltage is applied, the direction of incidence on the position sensitive detector 12 is made closer to a right angle, and the detection efficiency of the position sensitive detector 12 can be increased. On the other hand, when a deceleration voltage is applied, it is possible to prevent scattered secondary electrons from the exit aperture 10 and the like from being mixed into the position-sensitive detector 12.

The charged particles are converted into electrons by the position-sensitive detector,
It is amplified _{10-7 to 8} times and excites 13 multi-anodes. The multi-anode is composed of 30 radial electrodes, one of which corresponds to an azimuth of 2.5 °. A preamplifier and a pulse height discriminator are connected to each of the 30 electrodes, and the intensity of charged particles every 2.5 mm is measured simultaneously.

Next, in order to confirm the function of the above-described angle simultaneous measurement type charged particle energy analyzer of the present invention, the following experiment was performed. In FIG. 5, Si was used as sample 4
A (111) wafer was used. All parts in FIG. 5 were set in an ultrahigh vacuum tank, and the inside of the tank was evacuated to 3 × 10 ⁻¹⁰ Torr. The vacuum chamber is connected to a mirror of a scanning electron microscope that can irradiate the sample surface (right side in the figure) with an electron beam having a beam diameter of about 100 ° at 6 KV-1 nA from a direction substantially perpendicular to the plane of FIG. I have. After heating and cleaning the Si sample, the surface is 7 × 7
It was confirmed by reflection high-speed electron diffraction using the above-mentioned electron beam that it had a surface superlattice structure.

Auger electrons are emitted from the sample surface by the electron beam.
Inelastic secondary electrons are emitted. Among them, Si KLL Auger electrons (kinetic energy 1613 eV) were analyzed by the charged particle energy analyzer.

FIG. 6 shows the result. The channel numbers of the 30 multi-anodes are shown on the horizontal axis, and the KLL Auger electron intensity in each channel is plotted on the vertical axis. The rotation angle of the sample in each graph is an angle obtained by rotating the sample at the position shown in FIG. In this case, no potential difference is given between the deflection electrodes 6, 6 '. The structure in each graph reflects the anisotropy of KLL Auger electrons emitted from the Si (111) 7 × 7 surface. In fact, it can be seen that the structure of the graph shifts right and left as the sample rotates. The arrow in the graph is the direction of the axis of symmetry in the Si (111) plane, and the transition shows that the angle per channel of the multi-anode is 2.5 °.

FIG. 7 is a graph showing the effect of the deflection electrode at the sample position at a rotation angle φ = 0 ° in FIG. The deflection electrode voltage intensity is represented by what percentage of the voltage between the spherical electrodes 1 and 6 is applied to the potential of the deflection electrodes 6 and 6 '. A positive sign indicates a forward direction between the electrodes 6 and 6' and the spherical electrode, and a negative sign indicates Indicates that a reverse voltage was applied. It can be seen from the figure that the anisotropic pattern of the KLL Auger electron intensity changes with the change in the deflection electrode voltage, which is shown in FIG. 5 with the change in the Auger electron detection polar angle from the sample surface. Changes. Accurate determination of the detected polar angle is not performed in this embodiment.

In the above description, the case of the electrostatic concentric spherical energy analyzer has been described. However, the same angle simultaneous measurement function can be provided to the coaxial cylindrical mirror energy analyzer. In this case, the only difference is the shape and voltage distribution of the electrodes attached to the entrance slit, and the other parts are basically unchanged.

(Effects of the Invention) As described in detail above, the use of the simultaneous angle measurement type charged particle energy analyzer of the present invention has the following advantages.

The efficiency of the angle-dependent measurement is improved by several tens to one hundred times, and the measurement time is shortened accordingly. As a result, it is possible to perform measurement with less influence of temporal fluctuation of the system such as surface contamination.

Since the angle-dependent measurement does not involve mechanical movement of the device, vibrations can be eliminated and the micro area (several hundreds to several thousand square meters)
Can be adapted to the measurement of

The energy analyzer and moving mechanism can be installed on a vacuum flange such as a φ203mm conflat flange, and a large-scale rotating mechanism is not required. Therefore, the device can be downsized, and versatility and operability are increased.

As a measurement circuit system, a one-dimensional position-sensitive detection circuit system is sufficient, and it is relatively inexpensive and data processing is simple.

[Brief description of the drawings]

Fig. 1 is a conceptual diagram for explaining the principle of the present invention, Fig. 2 is a diagram for explaining three basic types of angle simultaneous measurement type charged particle energy analysis, and Fig. 3 is a sample and a book. FIG. 4 is a schematic diagram showing the positional relationship of the angle simultaneous measurement type charged particle energy analyzer of the present invention, FIG. 4 is a schematic diagram showing the positional relationship of the exit aperture, the deflecting electrode and the position sensitive detector, and FIG. FIG. 6 and FIG. 7 are schematic views of the embodiment.
This is a measurement example when the angle simultaneous measurement type charged particle energy analyzer of the present invention is applied to a (111) 7 × 7 surface. 1; electrostatic concentric spherical energy analyzer, 2; central axis of symmetry, 3;
Center of electrostatic concentric spherical energy analyzer, 4, 4 '; measurement sample, 5, 5', 6, 6 '; electrode on entrance slit, 7, 8; orbit of charged particle, 9; exit slit, 10 ; Exit aperture, 1
1; accelerating or decelerating electrode, 12; position sensitive detector, 13; multi-anode

Claims (3)

(57) [Claims] An electrostatic concentric spherical or coaxial cylindrical mirror type energy analyzer for irradiating a sample with X-rays or particles and analyzing the kinetic energy of charged particles emitted or scattered from the sample. A sample and an exit aperture arranged on a center axis of symmetry passing through the center of a spherical or coaxial cylindrical mirror cylinder, arc-shaped slits for an entrance and an exit centered on the center axis of symmetry, attached to the slit of the entrance. A charged particle energy analyzer, comprising: an electrode for deflecting and shifting the charged particles; and a position-sensitive detector provided as a charged particle detector after the exit aperture. 2. A charged particle energy analyzer according to claim 1, further comprising a moving mechanism for translating the entire energy analyzer in parallel along said central axis of symmetry. 3. An electrode for deflecting and accelerating and decelerating charged particles having an arc-shaped slit centered on a central axis of symmetry is provided between an exit aperture and a position-sensitive detector. The charged particle energy analyzer according to claim 1 or 2, wherein: