JPH0735985A - Electron microscope equipment - Google Patents

Abstract

PURPOSE:To provide an electron microscopic device having high spatial resolution and capable of forming a good-quality image. CONSTITUTION:In this electron microscopic device, an observed sample 2 is irradiated with ultraviolet rays 3 through an electron lens 1 constituted of a substance transmitting the ultraviolet rays and a photoelectron generated by such irradiation is detected by a fluorescent plate 4 so as to observe the image of the surface of the sample. Thus, the sufficient signal amount of the photoelectron is obtained without impairing the performance of the electron lens 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron microscope apparatus for observing a solid surface by using photoelectrons.

[0002]

2. Description of the Related Art Photoelectron microscopy (Photo-Emis)
sion Electron Microscopy:
PEEM) is a method of observing the surface of a solid by irradiating the surface of the solid with ultraviolet light and detecting photoelectrons generated, and plays a major role in materials and biological science. Especially in recent years, elucidation of diffusion phenomena on solid surfaces,
Is making an important contribution in the field of surface science,
It is getting attention.

However, the spatial resolution of PEEM is about several tens to several hundreds of nm, which is incomparably lower than that of a transmission electron microscope or a scanning electron microscope. If the spatial resolution and image quality of PEEM are improved, it is expected that the contribution to surface science will be dramatically improved in the future.

The two main factors that determine the spatial resolution of PEEM are (1) aberration of the electron lens and (2) signal quantity of photoelectrons. In order to obtain high spatial resolution, it is necessary to reduce the aberration of the lens and increase the amount of photoelectron signals. There are two types of electron lenses, an electric field type and a magnetic field type. In either case, in order to reduce the aberration of the lens, it is necessary to make the gap from the sample surface to the lens as small as possible. However, conventionally, the ultraviolet light for generating photoelectrons is radiated through the space having the narrow gap, so that there is a drawback that the incident angle becomes relatively grazing with respect to the solid surface. As a result, the density of ultraviolet light irradiated per unit surface area becomes small, and the signal amount of photoelectrons decreases. If the irradiation angle is increased in order to increase the amount of photoelectrons generated, the gap must be widened, resulting in an increase in lens aberration. As described above, the above items (1) and (2) have a contradictory relationship, and not satisfying both of them at the same time has been a major limitation in improving the resolution.

[0005]

The present invention makes it possible to irradiate a solid surface with ultraviolet light at a sufficiently large irradiation angle without being limited by the gap between the electron lens and the sample, and to suppress the lens aberration. It is an object of the present invention to provide an electron microscope device capable of obtaining a sufficient amount of photoelectron signals and achieving high spatial resolution.

[0006]

In order to achieve the above object, the present invention uses an electron microscope apparatus for observing an image of a solid surface by detecting photoelectrons generated by irradiating the solid surface with ultraviolet light. In the above, at least a part of the material forming the electron lens or the anode for imaging the photoelectrons has a property of transmitting ultraviolet light, and at least a part of the electron lens or the anode is made of a conductive material. It is supposed to be covered with a thin film.

A drawback of the conventional method is that the electron lens made of a metal material serves as a shield so that the solid surface cannot be irradiated with ultraviolet light at a high angle. Therefore, the irradiation density of ultraviolet light on the solid surface is reduced. In addition, in the case of a sample having unevenness on the surface, formation of a shadow region of ultraviolet light is also a major drawback.

According to the present invention, it is possible to irradiate a solid surface with ultraviolet light by passing through an electron lens or an anode, at least a part of which is made of a substance having a high transmittance for ultraviolet light. As a result, even if the gap between the solid surface and the electron lens is made small, it is possible to irradiate the solid surface with ultraviolet light at a high angle, the aberration of the electron lens can be made small, and a sufficient amount of photoelectron signals can be obtained. .

[0009]

EXAMPLE FIG. 1 shows an example of the present invention. 1 is diameter 10
2 is an electron lens having a cylindrical shape with a height of 30 mm and a height of 30 mm, and FIG. 2 shows an enlarged view of its cross section. The electron lens 1 is a transparent conductor of In ₂ O ₃ (IT
O) The film 8 is coated with a thickness of about 1 μm. Reference numeral 2 denotes a sample to be observed, which is parallel to the electron lens 1 with a gap of 1 mm. Reference numeral 3 represents a ray of ultraviolet light having a halogen lamp as a light source. Reference numeral 4 is a glass coated with a phosphor for forming an image, and is located approximately 300 mm from the sample surface. Reference numeral 5 represents an ultraviolet light introduction port, and 6 represents a vacuum container for keeping the entire environment in vacuum. When the irradiation angle formed by the center of the ultraviolet light 3 and the solid surface 2 is set to 70 degrees, the ultraviolet light 3 is emitted by the electron lens 1
And is focused on the sample surface. In the above configuration, an Au film on a Si substrate is used as the sample 3, and the vacuum container 6,
When the electron lens 1 was grounded and -5 kV was applied to the sample, a magnified image about 300 times as large as that of the sample 2 was obtained on the fluorescent plate 4. This magnified image is 35 mm with ASA sensitivity 400
When the film was photographed, a good quality photograph was obtained with an exposure time of about 20 seconds.

On the other hand, as a result of performing an experiment under the condition that the irradiation angle of 3 degrees is set so that the ultraviolet light 3 does not pass through the electron lens 1 and enters the sample 2, and the other conditions are kept the same, The image was so dark that it was difficult to even see it, and the S / N ratio was poor. When a photograph was taken in the same manner as described above, a sufficient image could not be obtained even with an exposure time of 20 minutes. Furthermore, it was confirmed that when the ultraviolet light was irradiated from such a grazing angle, a shadow was formed when the sample surface had irregularities, and thus information from the entire surface could not be obtained.

In this embodiment, the single-stage lens structure is adopted, but it goes without saying that a higher magnification and resolution can be obtained if a plurality of lens structures such as two or three stages are adopted.

[0012]

According to the present invention, a photoelectron microscope (PEE) is used.
In M), a sufficient amount of photoelectron signals can be obtained without impairing the performance of the electron lens, so that high spatial resolution and high quality image formation can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an electron microscope apparatus of the present invention.

FIG. 2 is a sectional view showing an example of an electron lens according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical electron lens 2 Observation sample 3 Ray of ultraviolet light 4 Fluorescent plate 5 Ultraviolet light introduction port 6 Vacuum container 7 Quartz glass 8 ITO film

Claims (2)

[Claims] 1. In an electron microscope apparatus for observing an image of a solid surface by detecting photoelectrons generated by irradiating a solid surface with ultraviolet light, an electron lens or an anode for forming the photoelectron is constituted. An electron microscope apparatus, wherein at least a part of the material has a property of transmitting ultraviolet light. 2. The electron microscope apparatus according to claim 1, wherein at least a part of the electron lens or the anode is covered with a conductive thin film.