JPS5941272B2 - Blocking potential type single-stage cylindrical mirror analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylindrical mirror analyzer suitable for use in an Auger analyzer for analyzing the surface structure of a sample, and particularly to a single-stage cylindrical mirror analyzer.

As a conventional one-stage cylindrical mirror analyzer, there is one as shown in Fig. 1. This analyzer 1 is equipped with an inner cylinder 2, an outer cylinder 3, etc., and further includes a sample S and an electron multiplier tube EM. It is interposed between.

Note that a slit A is provided at the end of the inner cylinder 2 on the electron multiplier tube side. By the way, in the conventional single-stage cylindrical mirror analyzer shown in Fig. 1, point P in Fig. 1 is the designed measurement point, but as shown by the broken line in the same figure, there is a measurement point from point P' other than point P. The signal also passes through this analyzer 1 to an electron multiplier (
detector) enters EM.

In such a case, not only is the resolution lowered and the intensity reduced, but the balance of peak intensities is also affected. This change in intensity ratio is particularly noticeable in vectors with far apart energy values.

For example, in pure silicon (Si)r, the LMM Auger electron peak exists at -92eV and -1662eV! I
C. When comparing the intensity with the existing KLL Augier electron peak, as can be seen from Table 1, this ratio changes by about 20% due to a movement of only 0.1 Tm in the measurement position. Table 1 shows the change in intensity ratio when the Si sample and the cylindrical mirror analyzer 1 are fixed and the electron beam is moved, where X is the moving distance and γ is (1622e
V peak intensity)/(92e peak intensity), σ is the standard deviation obtained using 20 or more values of γ.

Also, the acceleration of the electron is 5k, the modulation is 2V, -, (3.2e
).

To avoid this, it may be possible to make the primary electrons sufficiently thick, but this poses the problem of making it difficult to analyze minute points. Furthermore, energy resolution will also be sacrificed.

This is thought to be because, although the intensity has decreased, a signal from a point other than the ideal point on the sample S, such as point P', is added. Furthermore, in the conventional single-stage cylindrical mirror analyzer, measurements are performed with the inner tube 2 grounded.

Therefore, if the energy of the electron is E and the energy window width of the analyzer that measures it is 2△E, then the resolution ∆E/E
is a constant value (in the case of commercially available analyzers, 2/1000 to 6
/1000), so that for the Augier electron peak near 1000e, △? Many analyzers have a value of 2 to 3 eV in good conditions, usually around 5 eV. By the way, around this area there is about 700 eV of iron (Fe).
There are important transition metal elements such as IICI: 15 mar, cobalt (CO) 775 eV, nickel (NI) 848 eV, copper (Cu) 920 eV.

However, in a conventional single-stage cylindrical mirror analyzer, for example, the chemical shift of copper in the case of CU (5 CU20) is approximately 2 eV.
It is extremely difficult to measure In addition to the single-stage cylindrical mirror analyzer, a two-stage cylindrical mirror analyzer as shown in Fig. 2 has also been proposed.The advantage of this type of analyzer 1'' is that it Even when the measurement point is large, the analyzer 1'
For the second-stage analysis section AN2, the point corresponding to the point PVC in the case of the single-stage cylindrical mirror analyzer described above can be determined mechanically.

This is because only the signal from the very vicinity of point P on the sample S can pass through the analyzer and enter the electron multiplier tube EM, and the other signals are dropped by slits A1 and A3, so the measured signal This means that the image is not attached to the image.

However, this means that when attempting to perform minute point analysis, it is extremely difficult to detect a signal if the probe beam hits a region other than the vicinity of the analysis point P. This means that it is difficult to discover experimentally. In order to avoid this, it may be possible to increase the diameter of the slit A1, but this would sacrifice resolution. In addition, with this two-stage cylindrical mirror analyzer, it is possible to measure electrons with energy E by applying a blocking potential Er, but in this case, the energy of the electrons (pass The value of energy (1) Epass (=E-Er) can be set to about 100e, and therefore ΔE can be easily set to a value of about 0.5e. However, regarding the first-stage analysis part AN1 of the analyzer, it is structurally necessary to use a circular slit as the slit A1, so the resolution and efficiency are not very good.

Furthermore, in this two-stage cylindrical mirror analyzer, the inner tube 2' and outer tube 3' are longer than those in the one-stage type, so it is difficult to maintain high machining accuracy throughout. Another problem is that it increases costs.

Furthermore, when a spatial BVC electron gun is installed and used to perform Auger electron spectroscopy, it is difficult to apply a blocking potential to the inner cylinder 2', so the operation is normally performed with the inner cylinder 2' at ground potential. things will be done.

In FIG. 2, reference numeral A2 indicates a slit, G1 indicates a grounding grid, and G2 indicates a blocking potential grid.

However, each of these analyzers individually has various problems as mentioned above, and a common problem with both is that they are greatly affected by fluctuations in the measurement position with respect to the geometric center point P of the analyzer. That's true.

Although the stability of this measurement position is extremely closely related to quantitative accuracy, the optimum measurement point P' varies depending on the equipment conditions (mainly the magnetic field around the sample and analyzer) and depends on the energy of the electrons. (see Figure 3). In other words, even though the geometric center is point P, the trajectory is bent by the surrounding magnetic field, so the effective point is point P'
could be better. It is known that such a point differs depending on the energy, and the higher the energy, the closer the point PIIC becomes. For example, the rotation radius of low-energy electrons due to earth's magnetism is about 1 m for about 100 eV electrons. In this case, the distance is 20T1r! 0.1 while moving n? This difference is not negligible considering the operating conditions of the analyzer when performing minute point analysis (Table 1 and 4th and 5th
(See Figures A and b). Note that FIGS. 4a and 5a are graphs showing changes in the intensity of Si and Ni when the sample and electron beam are fixed and the position of the analyzer is moved, and FIGS. Similarly, FIG. 5b is a graph showing the change in intensity ratio of Si and Ni.

Furthermore, ion pumps are often used in current ultra-high vacuum equipment, and magnetic leakage from these magnets, however small, cannot be ignored as a problem. In other words, at this level of minute point analysis, it is necessary to carefully examine the measurement points, and the effective center of this measurement must be determined based on the electron energy, the geometrical arrangement of the entire device, etc.

This invention aims to solve these problems.
By making the blocking potential method applicable to single-stage models,
The window width of the measurement energy can be maintained at a very small constant value, and the optimum position/sample measurement position set in advance for each energy can be moved, thereby reducing the speed caused by fluctuations in the measurement point. The purpose of this invention is to provide a blocking potential type single-stage cylindrical mirror analyzer that can minimize changes in vector profile. For this reason, the present invention provides a sample moving mechanism capable of mounting and moving a sample, and a detector that detects secondary charged particles having sample-specific information obtained from the sample irradiated with a primary charged particle beam. In the one-stage cylindrical mirror analyzer interposed between the inner cylinder and the inner cylinder, the first and second slits are formed in the wall surface of the analyzer body. an outer cylinder that fits into the inner cylinder at a predetermined interval, and a slit member provided at the detector side end of the inner cylinder, and a grounding grid is provided on the analyzer body. , a blocking potential grid is provided in the inner cylinder, a power source capable of applying a blocking potential is connected to the inner cylinder, and the measurement position of the sample is moved to an optimal position set in advance for each energy. The present invention is characterized in that a control means is provided for outputting a control signal to the sample moving mechanism.

Hereinafter, a blocking potential type one-stage cylindrical mirror analyzer as an embodiment of the present invention will be explained with reference to the drawings. Fig. 6 is a schematic configuration diagram thereof, in which a sample S is mounted and moved in the X-Y direction. A sample position automatic movement mechanism D that can be moved is provided. Furthermore, an electron multiplier tube EM is provided, and this electron multiplier tube EM is used to detect a sample ejected from the surface of the sample S that has been irradiated with an electron beam (primary charged particle beam) from an electron gun Ge;Ge'. This is a detector for detecting Auger electrons (secondary charged particles) that have unique information.

A single-stage cylindrical mirror analyzer 1 is interposed between a sample S with a moving mechanism D and an electron multiplier EM.

The analyzer 1 also includes an inner cylinder (inner cylinder) 2 and an outer cylinder (outer cylinder) 3 within the analyzer main body 1a.
First and second slits A' and A5 are formed in the wall surface of the slit.

Furthermore, the outer cylinder 3 is fitted from the outside of the inner cylinder 2 with a predetermined gap between the inner cylinder 2 and the outer cylinder 3.
The space between is formed as an electron passage path for electrons from the sample S that have passed through the first slit A/ to exit from the second slit Al.

Note that the electron gun has an inner cylinder 2ifC, as indicated by the symbol Ge.
It may be built-in, or it may be disposed outside the analyzer 1, as indicated by the symbol Ge'.

When the electron gun is housed in the inner tube 2, it is necessary to double shield it as shown in FIG.

Further, a slit member having an annular slit A is provided at the end of the inner cylinder 2 on the detector side.

By the way, a first power source 4 is connected to the inner tube 2, and a second power source 5 is interposed between the inner tube 2 and the outer tube 3. The first and second power supplies 4 and 5 are respectively configured of variable DC power supplies 4a and 5a and modulated AC power supplies 4b and 5b that are connected in series.

In addition, a blocking potential grid G2 is provided at the sample side end of the inner cylinder 2.
At the same time, a grounding grid G1 is provided at the sample side end of the grounded analyzer main body 1a. Therefore, by changing the voltage Vr of the DC power source 4a, the AC power source 4
When the voltage Mr of b is modulated, this acts on the grid G2, and together with the effect of the grid G1, the pass energy Epass can be made constant, so the window width can be kept constant.

Furthermore, by changing the voltage Vp of the DC power supply 5a and applying voltage MpVC modulation of the AC power supply 5b, it is possible to change the electric field state between the inner cylinder 2 and the outer cylinder 3. The passing energy of the electrons passing through the second slit A'' can be controlled.

Note that a draw-in DC power supply 6 capable of applying a constant voltage Vi is interposed between the inner cylinder 2 and the electron multiplier EM, and thereby the electron multiplication factor of the electron multiplier EM is maintained constant. can.

By the way, a control means 7 is provided which outputs a control signal to the moving mechanism D to move the measurement position of the sample S to an optimal position set in advance for each energy.

The control means 7 includes at least a memory that stores information regarding the optimal measurement position on the sample corresponding to each energy set in advance, and controls reading of data in this memory and performs other desired signal processing. The signal Sd from the computer 7 is supplied to the automatic sample position movement mechanism D via the I/O interface 8.

In addition, this computer 7 includes each variable DC power source 4a, 5.
Voltage value of a Vr, V? It also serves as a mechanism for voltage adjustment, and signals Svr and Svp are supplied to each power source 4a and 5a via the I/0 interface 8 for voltage adjustment.

Furthermore, the computer 7 also serves as a mechanism for deflection control of the electron guns Ge; Ge', and a signal Sdc for this deflection control is sent to the electron gun G via the I/O interface 8.
e;Ge′・\supplied. With the above-described configuration, the sample S is irradiated with an electron beam from the electron gun Ge;Ge'' controlled by the computer 7.

At this time, the moving mechanism D, which is also controlled by the computer 7, is operated so that the PVC electron beam is irradiated at the optimal measurement position on the sample S, which is determined depending on the energy.

When the electron beam is irradiated in this way, Auger electrons with sample-specific information are generated from the surface of the sample S, and only those with energy above a certain size are used as grid G.
The Auger electrons enter between the inner tube 2 and the outer tube 3 from the first slit A1, where the passing energy is controlled, and the Auger electrons enter the second slit Ai' again.
From there, the electron enters the inner cylinder 2, and finally passes through the annular slit A to the electron multiplier tube EMifC. more detected.

At this time, since the electron pass energy is maintained at a constant value by the grids G1 and G2, the window width can be kept constant.

Furthermore, since it is easy to perform measurements with this window width of 1 e or less, it is also possible to measure substances with a chemical shift of about 2 eV, such as in the case of Cu and CU2O.

Note that the amount of pass energy and the amount of energy of electrons passing through the space between the inner tube 2 and the outer tube 3 are controlled by voltage values R and p using signals Svr and Svp from the computer 7.
This is done by changing the .

In addition, even if the measurement energy changes, the electron beam hits the optimal position on the sample S corresponding to this energy.
The moving mechanism D operates upon receiving a signal Sd from the computer 7.

Therefore, changes in the vector profile due to changes in measurement points can be minimized. As detailed above, the blocking potential type single-stage cylindrical mirror analyzer of the present invention provides the following effects and advantages.

(1) Measurement with extremely high stability and a window width of 1e or less is possible.

Therefore, it is most suitable for use in measurements using Auger electron spectroscopy, including state changes associated with metal oxidation. (2)
By adjusting the potential applied to the inner cylinder and bringing it to earth potential, measurements can be made under exactly the same conditions as conventional single-stage analyzers, which improves versatility. (3) Determining the optimum measurement point is easy. That is, it is possible to measure the change in intensity due to positional deviation from the optimum point, and to store the optimum point based on this change in intensity in the computer in advance.

Furthermore, unlike conventional two-stage analyzers, it does not show steep changes in intensity with respect to position, so it is easy to understand changes sequentially. (4) In measurement, constant window width (ΔE constant) type analysis becomes possible.

This value can be arbitrarily determined by setting the pass energy Epass during the experiment. (5) Since it is possible to use an annular slit, it is advantageous in terms of resolution and brightness compared to conventional two-stage analyzers.

(6) With the stabilization of the measurement position, the instability that accompanies measurement can be guaranteed even for minute point analysis with a probe diameter of 0.1 m or less.

(7) As a result of (6), it is possible to have a standard spectrum that does not depend on the installation conditions of the measuring instrument as common data, increasing the accuracy of surface analysis and increasing the compatibility of Augier analysis data. can. In other words, it becomes possible to determine sensitivity coefficients that do not differ for each standard device. (8) Although it is desirable to operate by correcting the surrounding magnetic field, even without magnetic field correction, compared to the conventional type, the
It is expected that there will be significant improvement below e.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing a conventional single-stage cylindrical mirror analyzer, Figure 2 is a schematic diagram showing a conventional two-stage cylindrical mirror analyzer, and Figure 3 is a schematic diagram showing a conventional cylindrical mirror analyzer. FIG.
b and FIGS. 5A and 5B are graphs for explaining the operation of a conventional cylindrical mirror analyzer, and FIG. 6 shows a blocking potential type single-stage cylindrical mirror analyzer as an embodiment of the present invention. FIG. 1... Single-stage cylindrical mirror analyzer, 1a...
Analyzer main body, 2...Inner cylinder, 3...Outer cylinder, 4, 5...Power supply, 4a, 5a...Variable DC power supply, 4b, 5b... AC power supply, 6...
.....Line-in power supply, 7.....computer as control means, 8.....I/O interface, A, A', AI'......slit, D ...
...Sample position automatic movement mechanism (sample movement mechanism), S...
...Sample, G1...Grounding grid, G2.
...Blocking potential grid, Ge, Ge'...
・Electron gun, EM...Electron multiplier tube (detector).

Claims (1)

[Claims] 1. A sample moving mechanism capable of mounting and moving a sample, and a detector that detects secondary charged particles having sample-specific information obtained from the sample irradiated with a primary charged particle beam. In the one-stage cylindrical mirror analyzer interposed between an outer cylinder that fits into the inner cylinder at a predetermined interval on the outside of the analyzer, and a slit member provided at the detector side end of the inner cylinder, and a grounding grid provided on the analyzer body. At the same time, a blocking potential grid is provided on the inner cylinder, a power source capable of applying a blocking potential is connected to the inner cylinder, and the measurement position of the sample is moved to an optimal position preset for each energy. A blocking potential type single-stage cylindrical mirror analyzer, characterized in that a control means for outputting a control signal for movement to the sample moving mechanism is provided. 2. The blocking potential type single-stage cylindrical mirror analyzer according to claim 1, wherein the primary charged particle beam is an electron beam irradiated from an electron gun, and the secondary charged particles are Auger electrons. 3. A variable DC power source and an AC power source are interposed in series between the inner tube and the outer tube in order to control the passing energy of the secondary charged particles passing between the inner tube and the outer tube. A blocking potential type single-stage cylindrical mirror analyzer according to claim 1. 4. The detector is composed of an electron multiplier tube, and in order to maintain the electron multiplication factor of the detector constant, a power source capable of applying a constant voltage is interposed between the inner cylinder and the detector. A blocking potential type single-stage cylindrical mirror analyzer according to claim 1. 5. The blocking potential type one-stage cylindrical mirror analyzer according to claim 1, wherein a blocking potential grid is provided at the sample side end of the inner cylinder. 6. The blocking potential type single-stage cylindrical mirror analyzer according to claim 1, wherein a grounding grid is provided at the sample side end of the analyzer body. 7. The blocking potential type single-stage cylindrical mirror analyzer according to claim 1, wherein the slit is configured as an annular slit. 8. The blocking potential type single-stage cylindrical mirror analyzer according to claim 1, wherein the power source connected to the cylinder is comprised of a variable DC power source and an AC power source connected in series. 9. The control means includes at least a memory that stores information regarding the optimal position set in advance for each of the energies, and a central processing unit that controls reading of data in the memory and performs desired signal processing. A blocking potential type single-stage cylindrical mirror analyzer according to claim 1, which is configured as a computer. 10 Claim 9, wherein the computer also serves as a mechanism for adjusting the voltage value of the variable DC power supply.
The blocking potential type single-stage cylindrical mirror analyzer described in 2.