JPS5931174B2 - Transmission scanning electron microscope - Google Patents

Description

[Detailed description of the invention] The present invention relates to a transmission scanning electron microscope.

In particular, it relates to means for detecting transmitted electrons.

FIG. 1 shows the schematic structure of a conventional transmission scanning electron microscope.

Generally, a field emission type electron gun is used for the purpose of narrowing the electron beam.

An extraction voltage 2 (
~3KV) is applied, electrons are emitted from the field emission cathode 1.

These electrons are accelerated to an arbitrary voltage (50 to 100 KV) by an acceleration voltage 4 applied between the second anodes.

These electrons are further focused onto the sample by a focusing lens (j).
A focused electron beam is scanned over the sample by a deflection coil.

Since a thin sample (100 OA) is generally used, most of the electrons pass through the sample.

The electron beam passing through the sample is affected by the local condition, thickness,
The intensity and scattering angle differ depending on the type of atom.

Therefore, in a transmission scanning electron microscope, a bright field detector 23 detects electrons 28 that have passed through without being scattered by the sample.
A dark field detector 22 is used to detect the scattered electrons 29.

One of the signals obtained by these detectors is selected by a switch 16, amplified by an amplifier 17, and used for brightness modulation of a cathode ray tube 19 that operates a scanning coil 18 using the same power source 12 as that for the deflection coil 7. form an image of the sample.

By using two cathode ray tubes 19, it is also possible to simultaneously form bright field and dark field images.

The dark-field detector 22 has a circular hole 21 approximately in the center of the fluorescent surface 10, which allows electrons that have passed through without being scattered by the sample to pass downward, and scatters the scattered electrons to the fluorescent surface 10. The light is converted into light and guided to the photoelectron amplifier tube 11 by the light guide J.

FIG. 2 shows the tip of the dark field detector 22 viewed from above.

In order to align the center of the circular hole 21 and the electron beam, the dark field detector 22 can be moved horizontally.

The electrons that have passed through the dark field detector 22 impact the fluorescent surface 13, are converted into light, and are guided to the photomultiplier tube 11 by the light guide 14.

In addition, as shown in FIG. 1, this detector 23 is equipped with an aperture 9 having a small circular hole 30 that further restricts the electrons passing through the circular hole 21 in order to improve the contrast of the image.
31 are provided.

This diaphragm can be moved in the XY-axis directions, and the size of the circular hole can also be changed.

Although such a detector configuration has sufficient performance, it has a complicated configuration, such as the presence of moving parts in a vacuum.

The present invention maintains the above performance and provides a simple configuration.

FIG. 3 shows an embodiment of the present invention.

The electrons transmitted through the sample 8 and scattered impact the fluorescent surface 27 to emit light.

The image formed on the fluorescent tube 27 is focused on the input end face of a detection means 26 such as a photomultiplier tube via a photoconductor 35 such as a glass plate and an optical lens 36.

On the input end face of the detection means 260, the distribution of electrons is shown as the distribution of light.

This image is converted into an electric signal by a photomultiplier tube 26, etc., and by inserting the bright field light shielding plate 25 shown in FIG. 4A in between, a bright field image is obtained, and the dark field light shielding plate shown in FIG. 4B 25'
A dark-field image can be obtained by inserting the image, and since it is outside a vacuum, horizontal movement can be easily performed.

The disk 37' is for blocking the bright field image.

By changing the diameter of the circular hole 37 in the bright-field light-shielding plate 25, the function of the diaphragm 31 shown in FIG. 1 can also be provided.

Further, if two polarizing plates are used as the light shielding plate 25, switching between bright field and dark field can be performed by simply rotating one polarizing plate.

FIG. 5 shows one embodiment of the present invention, in which reference numeral 34 at A is a fixed polarizing plate, and a circular plate 32 whose polarization direction is rotated by 90 degrees is inserted in the center of the fixed polarizing plate.

33 in B is a polarizing plate that has the same polarization direction as the disc 32. If they are stacked in this state, only the disc 32 will pass light and a bright field image will be obtained. If the polarizing plate 33 is rotated 90 degrees, all other than the disc 32 will be visible. It becomes a dark-field image that passes through.

Further, as a simple light-shielding plate, a photographic film or the like may be blackened at a desired position, or black paper or a metal mask may be pasted on a transparent film.

As stated above (according to the present invention, the performance of the detector is
A detector with a simple structure can be obtained without causing any deterioration, and its industrial value is greatly increased.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of a conventional transmission scanning electron microscope.
FIG. 3, FIG. 4, and FIG. 5 are diagrams showing one embodiment of the present invention. In the figure, 8... Sample, 25... Bright field light shielding plate, 25'... Dark field light shielding plate, 26...
...Detection means, 27... Fluorescent surface, 35...
...Light transmitter, 36...Optical lens.

Claims (1)

[Claims] 1. In a transmission scanning electron microscope, a light emitting body disposed inside the mirror body and excited in response to an image of a sample transmitted by an electron beam, a light transmitting body guiding the output of the light emitter outside the mirror body, and a light transmitting body arranged outside the mirror body. an optical means for forming an image of the light from the light transmitting body on an input end face of the detection means; and an optical means located outside the mirror body and configured to selectively transmit the output of the light emitter at the input end face of the detection means. A transmission scanning electron microscope characterized by having a shield.