JPH0233845A - Scanning type electronic microscope - Google Patents

Abstract

PURPOSE:To detect only the secondary electrons effectively by making finely stopped electron beams scan the surface of a sample, and arranging the detector of an electronic microscope which detects secondary electrons emitted from the sample at a position that the angle formed by the axis looking down the sample surface and the sample surface becomes 5 deg. or less. CONSTITUTION:By irradiating sample surface with the electron beams 1 of a scanning type electron microscope, the secondary electrons that arose at the surface to the specified depth are made to arise isotropically in all directions. A detector 1 detects the secondary electrons advancing in the A0D direction almost parallel with the surface of these generated secondary electrons. And the electron beams 3 applied to the position A0 on the sample penetrate to the depth Zm, and the angle to take out the secondary electrons generated in the region shown by a dotted line is confined to within 5 deg.. The detector 1 detects the secondary electrons that the taking-out angle is confined to 5 deg., and only the secondary electrons that arose at the very surface of the sample are taken out effectively, and only the information that reflected the surface fine structure more certainly is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning electron microscope, and more particularly to a scanning electron microscope for observing surface microstructures.

[Prior art] When it is desired to observe the surface microstructure with particular emphasis using a conventional scanning electron microscope (hereinafter abbreviated as SFM), the acceleration voltage of the electron beam is lowered to increase the penetration depth of the electrons into the sample. The electrons emitted under conditions where the depth was shallow were detected. In this case, the angle (
There was no particular restriction on the take-out angle (hereinafter abbreviated as the take-out angle).

[Problems to be Solved by the Invention] No matter how narrow the electron probe is, it is thought that the resolution is limited to 2 to 3 nm from the interaction between the electron beam and the sample. One of the reasons for this is that the secondary electron source generated from the sample surface has a finite size. An incident electron enters a solid and is scattered and redirected until it completely loses its energy. Secondary electrons are generated even in deep regions by these solid-state scattered electrons, but because their energy is small, only those generated at the very surface (~10 nm) of the sample jump out into the vacuum.

Therefore, it can be said that SEM obtains information about a depth of about 10 nm from the surface. However, changing the accelerating voltage of the electron beam changes the penetration depth of the electron beam, and when the accelerating voltage is relatively high, there is a lot of secondary electron information from deep parts, whereas when the accelerating voltage is low, there is a lot of surface information. Therefore, images sensitive to surface microstructures can be obtained.

However, when it is desired to observe the fine structure of the surface with particular emphasis, even if the accelerating voltage is lowered as described above, the information detection of the surface structure cannot be said to be sufficiently emphasized.

The present invention has been made in order to solve the conventional problems as described above, and it is an object of the present invention to provide a scanning electron microscope that can effectively detect only secondary electrons generated on the very surface of a sample. With the goal.

[Means for Solving the Problems] The present invention provides means for scanning and covering the surface of a sample with a narrowly focused electron beam, and means for detecting secondary electrons emitted from the sample, modulating their brightness, and displaying them on a CRT. A scanning electron microscope, characterized in that the detector is disposed at a position where the angle between the axis of the detector looking into the sample surface and the surface of the sample is 5° or less. Under an electron microscope.

[Function 1] The gist of the present invention is to detect only the electrons generated on the very surface of the sample by reducing the extraction angle, and to obtain an SEM in which information on the fine structure of the surface is more emphasized. .

With reference to FIG. 1, a qualitative explanation will be given regarding the effect of increasing the detection sensitivity of the surface.

In FIG. 1, by irradiating the sample surface with the electron beam 3, secondary electrons generated on the surface up to a depth of approximately 10 nm are thought to be generated equidirectionally in all directions.

Among these, AoD occurs on the very surface and is almost parallel to the surface.
The secondary electrons traveling in the direction are detected by the detector 1.

However, the secondary electrons generated at A1 and proceeding in the A1D direction have a long distance to reach the sample surface, lose energy due to overmixing, and have a high probability of being absorbed by the sample. Therefore, by lowering the extraction angle 2, only the secondary electrons generated on the very surface can be effectively detected by the detector. In the figure, 7 m is the electron beam penetration depth, and 7 is the depth of the secondary electron generation region.

Assuming that the extraction angle 2 is θ, at a distance sufficient for the secondary electrons generated at depth A to reach the surface, ! −8 becomes Sinθ. here! If ≧10 m and A≦1 nm, θ≦5.7°.

If the distance from the secondary electron generation position to the sample surface is 10 nm or more, the secondary electrons lose energy and are absorbed by the sample, and if the distance is less than Inm, it is said to be surface information. Therefore, when the extraction angle is 5° or less,
It can be seen that information is obtained that emphasizes the secondary electrons at the very surface.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram schematically showing the scanning electron microscope of the present invention, which also serves as an explanation of the operation. A finely focused electron beam 3 generated from an electron beam source is △ on the sample. is irradiated. The incident electron beam 3 penetrates to a depth indicated by Zm in the figure, and the area becomes as indicated by the dotted line. Secondary electrons are generated up to the depth indicated by 7 in the figure. The secondary electrons generated in this region are detected by detector 1, which is set within 5° of the extraction angle, or, for the reasons mentioned above, the secondary electrons detected by detector 1 are Limited to those originating from the surface. Next, this electron beam 3 is moved to detect secondary electrons from another part.

By continuously performing this operation on the entire analysis area of the sample surface, it is possible to observe the fine structure of the very surface of the sample.

[Effects of the Invention] As explained above, the present invention has a mechanism for effectively detecting only the secondary electrons generated on the very surface of the sample, so the surface microstructure can be reflected more reliably. You can get information.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining one embodiment of the present invention. 1... Detector 2... Extraction angle 3... Electron beam 7-m... Electron beam penetration depth 7... Depth agent of secondary electron generation area

Claims (1)

[Claims] (1) In a scanning electron microscope equipped with means for scanning a sample surface with a narrowly focused electron beam, and means for detecting secondary electrons emitted from the sample, modulating the brightness, and displaying it on a CRT. A scanning electron microscope, characterized in that the detector is disposed at a position where the angle between the axis of the detector and the sample surface is 5° or less.