JPS6340019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission electron microscope equipped with an omega-type electron beam energy analyzer.

Recently, an omega-type electron beam energy analyzer, in which the energy dispersion path of the electron beam has an Ω (omega) shape, has been attached to a transmission electron microscope and used to obtain an image based on an energy-filtered transmitted electron beam. ing. This omega-type electron beam analyzer has the advantage of high dispersion power, but since the analyzer's electron beam incident direction and exit direction are located in a straight line, conventional omega-type electron beam analyzers In a transmission electron microscope, in order to switch the image to be obtained between a transmission image based on an energy-filtered electron beam by an analyzer and a normal transmission image based on an electron beam that does not pass through an analyzer,
The analyzer was mechanically moved or rotated to be placed on the optical axis or removed from the optical axis. Such mechanical movement or rotation is performed by mechanical operation from the atmospheric side, which tends to cause trouble on the vacuum seal, and also causes poor reproducibility in positioning the analyzer on the optical axis. Because of the insufficient amount of light, a good quality transmission image may not be obtained in some cases, and furthermore, the above switching cannot be performed quickly.

The present invention solves the drawbacks of such conventional devices,
A transmission system that eliminates vacuum troubles, always provides high-quality images, and allows quick switching between normal transmission images and transmission images based on energy-filtered electron beams. The purpose is to provide a type electron microscope.

Therefore, in the present invention, the electron beam transmitted through the sample 4 and the objective lens 5 is guided to an omega-type electron beam analyzer, and only the electron beam having a specific energy is extracted through a slit 40 that can be inserted and removed on the optical axis. In a transmission electron microscope having a mechanism for projecting an extracted electron beam onto a screen 42 via an intermediate lens 8 and a projection lens 41, the electron beam entrance end and exit end thereof are fixed so as to be located on the optical axis 10. Omega-type electron beam analyzer 7
, an excitation power source 31 for the analyzer, a changeover switch 36 for turning on and off the excitation power source, an auxiliary lens 6 provided between the objective lens and the analyzer, and an excitation power source 31 for the analyzer when the analyzer power source is on. an auxiliary lens power source capable of supplying two types of excitation currents preset to focus the electron beam passing through the lens on the incident end and guide the electron beam to the intermediate lens at a certain aperture angle when the analyzer power source is off; 26, first deflectors 22 and 23 provided on the incident side of the analyzer, and presetting necessary for aligning the axis of the electron beam incident on the analyzer when the analyzer power source is on and off. a first deflection power source 27, 28 that supplies the two types of deflection signals to the first deflector; and a second deflector 2 provided on the emission side of the analyzer.
4 and 25, and two preset deflection signals necessary for aligning the axis of the electron beam emitted from the analyzer when the analyzer power source is on and off can be supplied to the second deflector. The outputs of the second deflection power supplies 29 and 30, the auxiliary lens power supply, and the first and second deflection power supplies are switched to the changeover switch 3.
means 9 for switching in conjunction with the switching of 6;
32, 33, 34, and 35.

Embodiments of the present invention will be described in detail below based on the drawings. In FIG. 1 showing an embodiment of the present invention, 1
is an electron gun, 2 and 3 are first-stage and second-stage converging lenses, 4 is a sample to which the electron beam focused by these converging lenses 2 and 3 is irradiated, 5 is an objective lens, and 6 is an omega lens. When the omega-type electron beam analyzer 7 is not operating, the electron beam focused by the objective lens 5 is converged and guided to the intermediate lens 8, and when the omega-type electron beam analyzer 7 is operating, the electron beam that has passed through the objective lens 5 is converged and guided to the intermediate lens 8. Omega type electron beam analyzer 7
This lens has the role of converging the incident light to the incident end of the lens, and therefore, by switching the changeover switch 9, the lens 6 is supplied with a preset current corresponding to the above two lens states from the power supply 26. be done. The omega type electron beam analyzer 7 is fixedly mounted so that its electron beam entrance end and electron beam exit end are located on the optical axis 10. FIG. 2 is an enlarged view of the omega type electron beam analyzer 7, which has elements 11a, 11b, and 11c made of a nonmagnetic material such as copper. The tube 11a is a tube that serves as an electron beam passage when obtaining a normal electron beam transmission image, and the tube 11b is a tube that serves as an electron beam passage when dispersing the energy of the electron beam, and these two tubes are communicated with each other. Reference numeral 11c is a tube for connecting both of these tubes to a vacuum pump. The upper end of the tube 11a is vacuum-sealed with an O-ring 12 and connected to a liner tube (not shown) on the objective lens side, and the lower end of the tube 11a is vacuum-sealed with an O-ring 13 and connected to a liner tube (not shown) on the objective lens side. liner tube (not shown). A pair of substantially sector-shaped magnetic poles 14 are attached parallel to the plane of the paper so as to sandwich the tube 11b. The magnetic poles 15 are a pair of magnetic poles similar to the magnetic poles 14. A pair of magnetic poles 16 forming part of a donut shape
The tube 11b is also attached with the tube 11b sandwiched therebetween. (However, only one of the pair is shown in the drawing.) Magnetic pole 1
4 and 15 are magnetized by supplying an excitation current to their excitation coils, a magnetic field perpendicular to the page from the back side to the front side of the page is created in the gap between these two magnetic poles.
Ha is generated, and the pair of magnetic poles 16 generates a magnetic field Hb directed from the front side to the back side of the page. Therefore, when an excitation current is supplied to the analyzer 7, the electron beam that has flown along the optical axis 10 has its trajectory bent and flies along the tube 11b, during which time the electron beam is dispersed according to its energy. be done. Magnetic pole 1 mentioned above
4 and 16, and 15 and 16 are integrally connected via spacers 17 and 18 made of non-magnetic material, so that even the slightest displacement of the magnetic poles will not occur. Note that 19, 20, and 21 represent the yokes of the magnetic poles 14, 15, and 16, respectively. 1st
As shown in the figure, two-stage deflection coils 22 and 23 for alignment are arranged on the electron beam incident side of the analyzer 7, and two-stage deflection coils 24 and 25 for alignment are also arranged on the output side of the analyzer 7. It is being These coils 22 and 23 are connected to switching switches 32 and 33 by power supplies 27 and 28, respectively.
An excitation current is supplied via. Similarly, coil 2
4 is supplied with an excitation current from a power source 29 via a changeover switch 34. The coil 25 is also supplied with an excitation current from an adder circuit 38. The adding circuit 38 adds the sawtooth scanning signal supplied from the scanning signal generating circuit 39 and the excitation current for alignment from the excitation power supply 30 when the switch 37 is on, and adds the excitation current for alignment from the excitation power supply 30 when the switch 37 is off.
5 is supplied with only an excitation current for alignment. 31 is a power source for the analyzer, and the excitation current from the power source 31 is supplied to the analyzer 7 only when the switch 36 is in the connected state as shown by the solid line. Each of the power supplies 27, 28, 29, and 30 supplies two types of excitation currents similarly to the power supply 26. 1st
The seed excitation current is applied to the coils 22 and 22, respectively, so as to align the electron beam when the analyzer 7 is not excited.
The second type of excitation current is a current supplied to these coils so as to align the electron beam when the analyzer 7 is excited. These specific current values are set in advance by adjustment in the above two cases. The changeover switches 32, 33, 34, and 35 are for selecting these two types of excitation current.
These switches, like the switch 9, are designed to operate in conjunction with the switch 36 of the analyzer power supply 31. 40 is a slit for selectively passing only the electron beam having a specific energy among the electron beams whose energy has been dispersed by the analyzer 7, 41 is a projection lens, and 42 is a fluorescent plate. 4
3 is an electron beam detector, 44 is an amplifier, and 45 is a cathode ray tube to which a scanning signal from a scanning signal generator 39 is supplied.

In such a configuration, when observing a normal transmission electron microscope image, the changeover switch 36 is connected to the OFF side as shown by the dotted line, and the power supply 31 is turned off.
The excitation current from the Omega-type electron beam analyzer 7
Avoid being supplied to As a result, switch 3
Switches 9, 32, 33, 34, 3 are linked to 6.
5 is also connected as shown by the dotted line in FIG. Further, the switch 37 is turned off (opened) and the slit 40 is removed. As a result, electron gun 1
After the twisted electron beam passes through the sample 4, it is imaged by the objective lens 5, and then refocused by the lens 6 so that it enters the intermediate lens 8 at an appropriate aperture angle. The electron beam passing through the intermediate lens 8 is finally imaged onto a fluorescent plate 42 by a projection lens 41. At this time, as shown in FIG.
The electron beam that has deviated from the center is deflected so that its axis C intersects with the optical axis 10 at the position of the deflection coil 23, and the deflection coil 23 deflects the electron beam back so that the axis C of the electron beam is along the optical axis. Do such a deflection. Since the deflection coils 24 and 25 have the same function, the electron beam is not deviated off-axis by the residual magnetic field of the analyzer, and a transmitted image of the sample is formed on the fluorescent plate 42.

Next, when attempting to obtain a transmitted image of the sample based on a transmitted electron beam having a specific energy selected by the omega type electron beam analyzer 7, the changeover switch 36 is set to the connected state as shown by the solid line. Switch so that In conjunction with this switching, the switches 9, 32, 33, 34, and 35 are switched to the connected state shown by solid lines. Furthermore, the slit 40 is placed at the position shown in FIG. Also, at this time, the switch 37 is left off.

As a result, the electron beam from the electron gun 1 passes through the sample 4, is focused by the objective lens 5, and is further focused by the lens 6 onto the incident end of the analyzer 7. At this time, the deflection coils 22 and 23 deflect the electron beam so that when the analyzer 7 is excited, the electron beam is incident on the center of the input end of the analyzer 7 along the optical axis. On the other hand, power supply 3 is connected to analyzer 7.
Since the excitation current from 1 is supplied, the area between the pair of magnetic poles 14 and the area between the pair of magnetic poles 15 of the analyzer 7 has the second
In the figure, a magnetic field is generated from the back side of the paper surface to the front side, indicated by Ha, and a magnetic field directed from the front side of the paper surface to the back side, indicated by Hb, is generated in the area sandwiched between the pair of magnetic poles 16. Therefore, the Lorentz force based on the magnetic field Ha acts on the electron beam from the electron gun 1, causing the electron beam to move clockwise, and then to move counterclockwise due to the Lorentz force caused by the magnetic field Hb.
Finally, by performing a clockwise motion using the magnetic field Ha, the light is emitted from the output end of the analyzer 7 through the tube 11b. The electron beam whose energy has been dispersed by the analyzer 7 forms images on the dispersion surface of the analyzer 7 at different positions depending on the energy, but only the electron beam having the energy to be selectively extracted passes through the slit 40. The electron beam is deflected by coils 24 and 25 so that it passes through and is correctly guided to a subsequent lens system. slit 4
The electron beam having a specific energy that has passed through 0 passes through an intermediate lens 8 and a projection lens 41 to a fluorescent plate 4.
A sample image is formed on the fluorescent plate 42 based on the transmitted electron beam having a specific energy.

In the present invention described above, a transmission image formed by switching a switch is vacuum-sealed between a normal transmission image and an image based on an energy-selected electron beam without mechanical movement of the analyzer 7. Switching can be done quickly and without the above troubles. Furthermore, in the apparatus of the present invention, since the analyzer is fixed, no positional deviation occurs and a stable line can be obtained.

Furthermore, in the device described above, the switches 9, 3
2, 33, 34, 35, and 36 are connected as shown by the solid line, if the slit 40 is removed and the magnification of the intermediate lens 8 and the projection lens 41 is set to a smaller value than when obtaining a sample image, it is possible to obtain a fluorescent light. An enlarged spectral image of the dispersion plane of the analyzer 7 is projected on the light plate 42. Therefore, the fluorescent plate 42 was removed,
When the switch 37 is closed, a sawtooth scanning signal is supplied to the coil 29 via the adding circuit 38, and the spectral image oscillates at the position of the fluorescent plate 42 in accordance with the scanning signal. Therefore, a detection signal obtained by converting the spectrum into an electric signal is generated in the detector 43, but this signal is supplied to the cathode ray tube 45 to which the scanning signal from the scanning signal generation circuit 39 is supplied. A signal representing the spectral intensity of the transmitted electron beam as shown in FIG. 4 is displayed.

Therefore, in the device according to the invention, the deflection coil for alignment can be used as a scanning coil for displaying electron beam spectral signals on a cathode ray tube or the like.

The embodiment described above is only one embodiment of the present invention,
Other embodiments may also be employed.

For example, in the embodiment described above, two stages of deflection coils for alignment are provided on each of the incident end side and the output end side of the omega type electron beam analyzer, but if the deviation of the electron beam is small, one stage Each deflection coil may be used, and an electrostatic deflection plate may be used instead of such a deflection coil.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram explaining an omega type electron beam analyzer, and FIG. 3 is a diagram showing an alignment coil 22,
23, and FIG. 4 is a diagram showing an energy spectrum image of an electron beam displayed on a cathode ray tube. 1: Electron gun, 2, 3: Converging lens, 4: Sample,
5: Objective lens, 6: Lens, 7: Omega type electron beam analyzer, 8: Intermediate lens, 9, 32, 3
3, 34, 35, 36, 37: changeover switch, 10: optical axis, 22, 23, 24, 25: deflection coil, 26 to 31: power supply, 38: addition circuit, 3
9: Scanning signal generation circuit, 40: Slit, 41:
Projection lens, 42: Fluorescent plate, 43: Electron beam detector, 45: Cathode ray tube.

Claims (1)

[Claims] 1. The electron beam transmitted through the sample 4 and the objective lens 5 is guided to an omega-type electron beam analyzer, and only the electron beam having a specific energy is extracted through a removable slit 40 on the optical axis. In a transmission electron microscope having a mechanism for projecting a beam onto a screen 42 via an intermediate lens 8 and a projection lens 41, an omega-type transmission electron microscope is used, in which the electron beam entrance end and exit end are fixed so as to be located on the optical axis 10. An electron beam analyzer 7, an excitation power source 31 for the analyzer, a changeover switch 36 for turning on and off the excitation power source, an auxiliary lens 6 provided between the objective lens and the analyzer, and an excitation power source 31 for the analyzer when the analyzer power source is turned on. In this case, two preset excitation currents can be supplied to focus the electron beam that has passed through the objective lens on the incident end and guide the electron beam to the intermediate lens at a certain aperture angle when the analyzer power is off. an auxiliary lens power source 26 and a first deflector 2 provided on the incident side of the analyzer
2 and 23, and a first deflector that supplies two preset deflection signals necessary for aligning the axis of the electron beam incident on the analyzer when the analyzer power source is on and off. The axis of the electron beam emitted from the analyzer is aligned between the first deflection power source 27, 28 and the second deflector 24, 25 provided on the output side of the analyzer, when the analyzer power source is on and when the analyzer power source is off. a second deflection power source 29, 30 capable of supplying two preset deflection signals necessary for the second deflector to the second deflector; Means 9, 32, 33, 34, 35 for switching in conjunction with switching of the switch 36
A transmission electron microscope characterized by comprising: