JPH0558212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron microscope equipped with an energy filter, and more specifically, the present invention relates to an electron microscope equipped with an energy filter. It is equipped with a plurality of return spectrometers, and can be observed by switching between an energy filter image formed by the electron beam that has passed through the plurality of spectrometers and an unfiltered image formed by the electron beam that has not passed through the plurality of spectrometers. Regarding electron microscopes.

(Prior art) When an electron beam is irradiated onto a sample, the electron beam loses some of its energy due to interaction with the sample, but when the energy of the electron beam that has passed through the sample is analyzed, it can be determined that A unique spectrum can be obtained depending on the element. An electron microscope equipped with an energy filter is a device that performs elemental analysis by observing this energy loss spectrum. FIG. 2 is a schematic diagram of an electron microscope equipped with a conventional energy filter. In FIG. 2, 1 is an electron gun, 2 is an electron beam emitted from the electron gun, the electron beam 2 is focused by a focusing lens 3 and irradiated onto a sample 4, and an objective lens 5 shows a transmission electron image 6 of the sample. After forming an incident point 8 and an incident image 9 with an incident lens 7, the incident light can enter spectrometers 10a, 10b, and 10c forming an energy filter. In an electron microscope using an energy filter, spectrometers 10a, 10c and spectrometer 10b are excited to generate uniform magnetic fields in opposite directions, thereby deflecting the electron beam 2 and dispersing the energy. After that, the spectrometer is returned to the original optical axis 11 (in conventional general energy analyzers, the spectrometer is
(The electron beam is emitted perpendicular to the optical axis of the electron microscope and entered into a detector.) As in the apparatus shown in FIG. 2, three spectrometers 10a, 10
b, 10c allows spectrum analysis to be performed by aligning the electron beam 2 with the optical axis of the electron microscope.

These spectrometers 10a, 10b, 10c
In , the electron beam 2 is dispersed according to its energy value, and if it is replaced with visible light, it is dispersed due to the difference in wavelength, that is, the difference in color.
In some parts of the spectrometer, the light is focused to produce a colorless state. The image 12 formed in the spectrometer 10c is an image formed by converging dispersed electron beams of various energy values, and is in a colorless state and is called achromatic image. An energy loss spectrum 13 is also formed below the spectrometer 10c, and this is an image of chromatic dispersion. ) and select intermediate lens 15.
The color image 12 is focused on, and the energy filter image 18 is enlarged and projected onto the screen 17 by the projection lens 16.

FIG. 3 is a diagram for explaining an electron microscope image (unfiltered image) when no energy filter is used. When the energy filter is not used, the spectrometers 10a and 1 in FIG.
The excitation of 0b and 10c is turned off, and the transmitted electron image 6 is transformed into a color-disappeared image 12 in FIG. 2 by the entrance lens 7.
An enlarged image 19 is formed at the position. Here, the distance from the incident lens 7 to the enlarged image 19 is long, and therefore the magnification of the enlarged image 19 is much larger than that of the achromatic image 12 in FIG. 2, and when obtaining an energy filter image, There was a large difference in magnification between the case of obtaining an unfiltered image and the case of obtaining an unfiltered image.

(Problems to be Solved by the Invention) As mentioned above, in the conventional electron microscope equipped with an energy filter, there are two cases in which an energy filter image is observed through the energy filter;
When observing an unfiltered image, which is a normal electron microscope image, the magnification of the image is significantly different.
Since it is difficult to observe at the same magnification, it is necessary to change the magnification when switching images, which is very inconvenient.

The present invention has been made in view of the above points, and its purpose is to eliminate the difference in magnification when switching between an energy filter image and an unfiltered image for observation, thereby eliminating the inconvenience of adjusting the magnification. .

(Means for Solving the Problems) The present invention for solving the above problems includes a plurality of spectrometers that deflect an electron beam from a sample, disperse the energy, and then return it to the original optical axis. In an electron microscope that can switch and observe an energy filter image formed by an electron beam that has passed through a plurality of spectrometers and an unfiltered image formed by an electron beam that has not passed through a plurality of spectrometers, The present invention is characterized in that a transfer lens is provided on the electron line through which the electron passes only when forming an image, and an unfiltered image having the same size as the energy filter image is obtained.

(Function) In the present invention, when switching between the energy filter image and the unfiltered image, the transfer lens is excited and the energy filtered image and the unfiltered image can be observed at the same magnification.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows a spectrometer 1 in an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing a normal electron microscope operation in which the excitation of 0a, 10b, and 10c is cut off to obtain an unfiltered image. Since the same parts in the figure as in FIG. 2 are given the same reference numerals, repeated explanation will be avoided. 21 is a mechanical axis of vertical symmetry of the spectrometers 10a, 10b, 10c, and 22 is a transfer lens provided on the electron line through which the electron beam 2 passes only when forming an unfiltered image; It is installed on the vertical symmetry axis 21 of the meters 10a, 10b, 10c. transfer lens 2
2 is a lens with a magnification of 1, and is excited only when observing an unfiltered image, and converts the incident image 9 into a color-extinguished image 1 in FIG.
The transmitted electron image 23 is transferred to position 2 at the same magnification to form a transmitted electron image 23. The focal length ft of the transfer lens 21 at this time is ft=l/4...(1) (where l is the distance from the position of the incident image 9 to the position of the color erasing image 12 in FIG. 2) Focal length l/4 If you place the subject at a position twice the focal length, then from equation (1), 1/ft - 1/2ft = 1/2ft...(2) The first term on the left side, ft, is the focal length, and the second term, 2ft, is the focal length. The position of the subject from the lens, 2ft on the right side is the position of the image from the lens. From equation (2), the image is located at a position equal to the distance between the lens and the subject on the opposite side of the lens, and the magnification is 1.

From the above explanation, since the passing electron image 23 is formed in the same size as the color disappearing image 12 at the position of the color disappearing image 12 in FIG. Obtained as an image. Please note that the examples listed here are only examples.
For example, the position where the image is formed by the transfer lens 22 may be the position of the energy filter image shown in FIG. Furthermore, the incident point 8 may be transferred instead of the incident image 9.

(Effects of the Invention) As described above in detail, according to the present invention, even if an energy filter image and an unfiltered image are switched, the image can be formed without changing the magnification.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electron microscope in an unfiltered state equipped with an energy filter according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an electron microscope equipped with a conventional energy filter, and FIG. 3 is a diagram of a conventional energy filter. FIG. 1 is a schematic configuration diagram of an electron microscope equipped with a filter in an unfiltered state. DESCRIPTION OF SYMBOLS 1... Electron gun, 2... Electron beam, 3... Focusing lens, 4... Sample, 5... Objective lens, 6... Transmission electron image, 7... Incident lens, 8... Incident point, 9...
...Incidence image, 10a, 10b, 10c... Spectrometer, 11... Optical axis, 12... Color extinction, 13
... Energy loss spectrum, 14 ... Energy selection slit, 15 ... Intermediate lens, 16 ...
...Projection lens, 17...Screen, 18...Energy filter image, 19...Enlarged image, 20...
Projection image, 21... vertical symmetry axis of spectrometer, 22... transfer lens.

Claims (1)

[Claims] 1 Equipped with a plurality of spectrometers that deflect and energy disperse an electron beam from a sample and return it to the original optical axis, and an energy filter image formed by the electron beam that has passed through the plurality of spectrometers and the plurality of spectrometers. In an electron microscope capable of switching between an unfiltered image formed by an electron beam that does not pass through a meter and an unfiltered image for observation, a transfer lens is provided on an electron path through which the electron beam passes only when forming the unfiltered image; An electron microscope characterized in that an unfiltered image of the same size as an energy filtered image is obtained.