JPS5864743A - Electron-ray device - Google Patents

Abstract

PURPOSE:To realize a clear reflected-electron image with a high resolution as well as a clear image of the internal part of a sample by placing a diaphragm plate in front of the sample, installing a reflected-electron detector above said diaphragm plate, and providing a means of moving said detector and said diaphragm plate along the optical axis. CONSTITUTION:A diaphragm plate 4 and a reflected-electron detector 5 are supported at the lower end of a holder 7. The holder 7 is attached to an L- shaped driving lever 8, and moved up and down integrally with the lever 8. The lever 8 is supported by a supporter 9, and has a rack 10 in its upper part. The rack 10 comes into engagement with a pinion 11, and the plate 4 and the detector 5 can be moved in the direction of the optical axis by rotating the pinion 11 from outside a mirror body. Owing to the above constitution, a reflected- electron image with a high resolution can be realized by detecting electrons with small energy loss. Consequently, a clear reflected-electron image with information of the internal part of a sample can be obtained.

Description

Detailed Description of the Invention The present invention relates to an electron beam device capable of obtaining high-resolution backscattered electron images and images of the interior of a sample in a high-acceleration voltage scanning electron microscope. When this happens, some of the electrons penetrate deep into the sample and are disturbed by the sample molecules many times, before some of them fly out from the sample surface. These electrons are generally called backscattered electrons, but the electron beam inside the sample is spreads, and the spread increases as the accelerating voltage increases, so when an electron beam is scanned with the sample to obtain a backscattered electron image, the blur of the image increases as the accelerating voltage increases〇Therefore, Conventionally, backscattered electron images have not been observed at high accelerating voltages. However, backscattered electrons contain a lot of information from the sample, and especially when an electron beam with a high acceleration voltage is used, it brings information about the inside of the sample that cannot be obtained from a secondary electron image. It is strong (sacrificed) to use it to obtain a clear sense of self.

The present invention provides an apparatus that can meet these demands, and in which a sample is placed in or immediately behind a lens magnetic field, and the reflected electron beam from the sample is imaged by the lens magnetic field, thereby separating energy. As described above, a diaphragm plate is placed in front of the sample described in #l, a backscattered electron detector is installed above the diaphragm plate, and means is provided for moving the backscattered electron detector and the diaphragm plate along the optical axis. O, which is characterized by the following characteristics, will be explained based on the following aspects. 11 is a diagram explaining the present invention in detail, and 1 and 2 indicate the upper and lower magnetic poles of the objective lens, respectively. Although not shown, the objective lens has a yoke and an excitation coil connected to the magnetic f&, and a strong lens magnetic field is formed between the upper magnetic pole 1 and the lower magnetic pole 2 by passing a current through the excitation coil. B8 shows the axial magnetic field distribution of the lens magnetic field. Although not shown above the objective lens, a focusing lens, an electron gun, and a scanning deflection coil are usually installed, and the electron beam emitted from the electron gun is focused and
While scanning, irradiate the sample 6 placed within the objective lens magnetic field.
When the electron beam of V) is irradiated, this electron beam is scattered inside the sample, undergoes energy loss, and part of it jumps out from the sample surface as reflected electrons. These reflected electrons have various energies lower than the energy of the incident electrons. , and images are formed for each energy by the magnetic field of the objective lens.

In the figure, heat is the 20KeV electron focus point, or 4
0KeV #C is a focus point of electrons of 60KeV, d is 80KeV, and e is 100KeV (zero energy loss), and they are separated in the optical axis direction. And as shown in the figure (if it is divided into intervals of 20 KeV, each interval is 5
Electrons (100 KeV) which have a diameter of 0 mm or more and which have not suffered any energy loss are focused in accordance with the position of the crossover image of the focusing lens in the previous stage. It is not possible to place a detector at each focus point (a, b, c...) of these undesirably separated electrons, and even if a detector were placed, there would be electrons with all energy keys at one point on the axis. , it is not possible to detect a single child with a single energy.The present invention provides a novel detection means that can efficiently detect only electrons with a specific energy, which is the cutoff of separated electrons, as shown in the JIEI diagram. As shown in Fig. 2, a semicircular diaphragm plate 4 as shown in Fig. 3 is placed on one side of the optical axis, and a detection device 5 is placed above it. A notch or hole 6 is provided near the optical axis so as not to obstruct the passage of the irradiated electron beam.
Further, the shape of this diaphragm plate is not limited to a semicircular shape, but may be a similar shape 2, for example, a fan shape, or a complete circle.

On the other hand, as the detector 5, for example, a PN junction type semiconductor detector is used, and in order to improve the detection efficiency, it is preferable to tilt it as shown in the figure. Also, the length of the detector in the optical axis direction If the width of electron incidence in the optical axis direction is narrowed by shortening , or by providing another diaphragm plate, it is possible to detect only electrons with a very narrow energy width. The energy of the detected electrons is determined by the position of the diaphragm plate 40 in the optical axis direction.
KeV electrons have been detected. By moving the diaphragm plate 4 and the detector 5 in the direction of the optical axis as shown by the arrow, it is possible to detect reflected electrons having an energy of 1.

FIG. 4 shows an example of movement II#I of the aperture plate and the detector, in which the aperture plate 4 and the detector 5 are held at the lower end of the holder 7. This holder is attached to a 5-shaped drive rod 8 and can be moved downward in one motion. This drive rod is supported by a holder 9 and has a rack 10 on the upper part. The rack is engaged with a pinion 11, and if this pinion is rotated by an operation from outside the mirror body, the aperture plate 4 and the detection! S5 can be moved in the optical axis direction. In this embodiment, since the aperture plate and the detector are inserted inside the upper pole of the objective lens, the aperture diameter of the upper pole allows it! Processed into large m-change (diameter 20mm or more),
The lens is therefore asymmetrical.

With the above configuration, it is possible to detect only the backscattered electrons with a narrow range of energy as new values, so it is possible to obtain a high-resolution backscattered electron image by detecting electrons with little energy loss. A clear backscattered electron image containing information about the inside (deep part) of the sample can be obtained using the detection IC.

In the above example, the sample was placed in the magnetic field of the objective lens, but if it is not possible to place the sample in the magnetic field due to the structure of the lens or the nature of the sample, it may be placed directly behind the magnetic field d of the scissors.

Claims (1)

[Claims] L When a sample soil is irradiated with a focused electron beam, one or two-dimensional L
ζ scan and detect the reflected electron beam from the electron beam irradiation point ′・
In the apparatus shown in the image, the sample is placed in a lens magnetic field.
Or, place it directly behind the sample, and image the reflected electron beam from the sample using this lens magnetic field to perform energy separation. Place an aperture plate in front of the sample, and
The electron beam device L@ is characterized by having a backscattered electron detector installed on one side, and a means for moving the backscattered electron detector and a diaphragm plate along the optical axis. or an electron beam device according to claim 1, which has a similar shape.