JP2001052640A - Electron microscope and sample heating method - Google Patents

Abstract

(57) [Summary] [Objective] To enable a sample to be heated to a higher temperature than before in an electron microscope. [Constitution] In an electron microscope capable of heating a sample 2 to be observed without changing lens conditions at the time of observation, a heating electron beam 5 having an acceleration voltage lower than that of the observation electron beam 6
Is irradiated toward the objective lens 3 which is an electron lens including the sample 2 on the optical path of the observation electron beam 6, and the heating electron beam source 1 which heats the sample 2 via the lens working portion of the electron lens 3 is used. The sample 2 is heated by utilizing the operating magnetic field of the objective lens 3 for the observation electron beam 6 for focusing the heating electron beam 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron microscope and a method for heating a sample. More specifically, the present invention relates to an apparatus and a method for heating a sample during observation of the sample in an electron microscope.

[0002]

2. Description of the Related Art Hitherto, research has been conducted to trace the behavior of a microstructure of a sample when a physical change is caused by heating or pulling, and obtain multidimensional information to elucidate physical properties.

In such research, when observing a sample with an electron microscope, for example, as shown in FIG. 3, the sample is heated by a heating device installed around a sample holder (not shown) in the electron microscope. The behavior of 101 is microscopically grasped. The heating device is an electric resistance heating system in which the entire sample 101 is heated from the surroundings using a ring-shaped heating element (resistance wire) 105 as a heat source.
In such a sample heating apparatus, in order to protect the internal structure such as the objective lens 104 installed around the heat source from heat, the heating element 105 is housed in a furnace and the surrounding area is further covered with a heat shield 106. ing. In addition, the code | symbol 1 in a figure
02 is an electron gun and 103 is an electron beam.

[0004]

However, in the case of such a heating method using the electric resistance heating method, conduction or radiant heat from a furnace having a large volume is high due to, for example, a problem in the material of a heating element or a furnace. Since the influence on the internal structure of the electron microscope with high precision, particularly on the objective lens 104, becomes large, there is a problem that the heating temperature is naturally limited. Specifically, general sample size (1-3 mm diameter)
In order to maintain the required temperature and maintain the required high temperature, the furnace body containing the sample must have a diameter of 3 mm or more, and this high temperature and total generated It is difficult to install a furnace with a large amount of heat. Even if the heating element 105 is covered with the heat shielding material 106, the heat shielding material 106 and the furnace have a limited heat shielding ability depending on the material, and the installation space is limited according to the internal configuration of the electron microscope. Therefore, when the sample 101 is heated to a predetermined temperature or higher, a heat insulating structure for sufficiently preventing heat from being transmitted to the surroundings cannot be provided. For this reason, in the conventional electron microscope, the sample 101 can be heated only when the maximum temperature thereof reaches about 1000 ° C.

On the other hand, there is a demand for an electron microscope and a sample heating method capable of heating a sample to a higher temperature, in some cases, about 2000 ° C. For example, the behavior of a sample such as ceramics may not be traced unless the temperature is high. However, since the conventional heating method cannot locally heat, it cannot be heated to a high temperature.

Accordingly, an object of the present invention is to provide an electron microscope and a method for heating a sample, which can heat the sample to a higher temperature than in the past when observing the sample.

[0007]

In order to achieve the above object, the present invention is directed to an electron microscope in which a sample to be observed can be heated without changing lens conditions at the time of observation. A heating electron beam that irradiates a heating electron beam with an acceleration voltage lower than that of the beam toward an electron lens that includes the sample on the optical path of the observation electron beam, and heats the sample via the lens working portion of the electron lens. Source. Thus, as in the method for heating a sample according to claim 8, the heating electron beam irradiated at an acceleration voltage lower than the observation electron beam is applied to the electron lens including the sample on the optical path of the observation electron beam. Irradiation can be used to heat the sample using the electron lens to focus the electron beam for heating.

Therefore, the heating electron beam emitted at an acceleration voltage lower than that of the observation electron beam uses an electron lens on the optical path of the observation electron beam for focusing so as to have an extremely small and high electron density. It is focused and heats a localized area of the sample. That is, an electron lens designed to focus observation electrons transmitted through a sample has a very short focus lens for a heating electron beam emitted at an acceleration voltage much lower than the observation electron beam. It works so as to exist in multiple ways and repeats refraction and focusing action many times. As a result, the electron beam for heating has a very small beam diameter and an extremely high electron density. That is, a minute local portion of the sample is heated by the high-density electron beam. Therefore, the total amount of heat generated in the heated area is small and the influence of heat on the surroundings is small. Thermal effects on the structure can be reduced.

Here, it is preferable that the electron lens to which the heating electron beam is incident be an objective lens, and the sample be placed between the electrodes or in the vicinity thereof. in this case,
Since the electron lens containing the sample has a strong lens magnetic field to form a high-acceleration electron beam, it has a strong focusing effect on the heating electron beam. And the influence of heat on the surroundings is reduced. Further, the heating electron beam source may be disposed at a position that can be irradiated simultaneously with the observation electron beam, for example, at a position that can be irradiated toward the electron lens from an angle coaxial with or close to the optical axis of the observation electron beam. preferable.

According to a fifth aspect of the present invention, in the electron microscope according to any one of the first to fourth aspects, the acceleration voltage of the heating electron beam source is made variable. In this case, since the emission angle and spread are changed by changing the acceleration voltage, the focus of the heating electron beam shifts in the irradiation axis direction, and the heating range can be changed by widening or narrowing the heating range.

According to a sixth aspect of the present invention, in the electron microscope according to the first to third or fifth aspects, the heating electron beam source changes an incident angle or an incident position of the electron beam to the electron lens. I have to. in this case,
For example, the focusing position of the electron beam can be shifted on the sample surface.

Further, according to a seventh aspect of the present invention, in the electron microscope according to any one of the first to sixth aspects, the heating electron source can be intermittently irradiated. in this case,
The temperature can be adjusted appropriately by intermittently heating the sample.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an example of an embodiment shown in the drawings.

FIG. 1 and FIG. 2 show an embodiment of an electron microscope according to the present invention. The electron microscope includes an electron lens (in the present embodiment, an “object” shown in the figure below) that includes a heating electron beam 5 having an acceleration voltage lower than that of the observation electron beam 6 and the sample 2 on the optical path of the observation electron beam 6. A heating electron beam source, for example, an electron gun 1 for irradiating the sample 2 through the lens working portion of the electron lens 3 and irradiating it toward the lens 3). FIG. 2 schematically shows the sample 2, the objective lens 3, the condenser lens 4, etc. with the heating electron gun 1 at the center, but does not show other components of the electron microscope.

The heating electron gun 1 emits electrons at an acceleration voltage lower than that of the observation electron beam, for example, several kV, in order to obtain electrons suitable for heating. In the present embodiment, the heating electron gun 1 is provided outside the objective lens 3 and at the optical axis of the electron microscope, that is, the optical axis 9 of the observation electron beam 6.
It is installed so as to be retracted from the observation electron beam 6 at a position close to, and can be irradiated with the heating electron beam 5 toward the center of the objective lens 3.

The heating electron gun 1 is moved in parallel with the optical axis 9 to change the height or change the inclination to change the angle of incidence on the electron lens 3 by an adjustment mechanism (not shown). Thus, it is preferable that the position for focusing on the sample 2 is adjusted so as to be adjusted. in this case,
It is also possible to observe various behaviors by changing the heating position and mode without moving the sample 2.

The heating electron gun 1 is provided so as not to block the observation electron beam 6 applied to the sample 2. For example, in the present embodiment, as shown in FIG. 2, it is set at a position retracted from the path of the observation electron beam 6.
In this case, the heating electron gun 1 is installed at the optical axis 9 of the electron microscope, that is, for observation so that the objective electron beam 3 can be irradiated with the heating electron beam 5 as close as possible to the optical axis 9 of the objective lens 3. Preferably, it is close to the path of the electron beam 6.

The heating electron gun 1 used here is an electron generally used in an electron microscope or the like, except that the acceleration voltage uses a voltage sufficiently lower than that of the observation electron gun 8. No special structure is required for the gun, and a general known electron gun can be used. As the accelerating voltage, a voltage sufficiently lower than the electron beam 6 for observation, for example, several kv of about 1/100 of the electron beam for observation is used.

The heating electron gun 1 is capable of adjusting the accelerating voltage. For example, the heating electron gun 1 is provided so that the material and the shape of the sample 2 can be heated by changing the energy of the heating electron beam 5. ing. Further, the heating electron beam 5 may be irradiated continuously or intermittently. In this case, the temperature of the sample 2 can be appropriately adjusted. In the present embodiment, the heating electron gun 1 capable of performing such intermittent irradiation is used.

On the other hand, a high accelerating voltage is generally used as the observation electron beam 6 to affect the resolution. For example, in the present embodiment, an electron beam suitable as the observation electron beam 6 is obtained from the observation electron gun 8 by applying an acceleration voltage of about 100 kV to 300 kV. Note that the observation electron gun 8 used here may be a known electron gun similarly to the heating electron gun 1.

According to the electron microscope configured as described above, it is possible to trace the behavior of the sample 2 at a high temperature while heating a limited portion of the sample 2 under observation as follows.

That is, when it is necessary to heat the sample 2 to be observed, an acceleration voltage of about several kv is applied to the heating electron gun 1 so that the low-speed heating electron beam 5 is irradiated with the light of the observation electron beam 6. Irradiation is performed toward an objective lens 3 which is an electron lens including a sample 2 on a road.

At this time, the objective lens 3 acts as a strong lens for the heating electron beam 5, and it is as if FIG.
Since a very short focus lens as shown in (1) acts as a virtual lens 7 that exists in multiples, the heating electron beam 5 passing through the lens magnetic field is repeatedly refracted and focused many times to make the beam diameter extremely large. Small and high electron density. Further, since the heating electron beam 5 having an acceleration voltage sufficiently lower than that of the observation electron beam 6 does not easily pass through the sample 2, the energy absorption efficiency in the sample 2 is increased and the temperature is easily raised. Furthermore, since the region that is heated to a high temperature has a small volume locally, the total amount of generated heat is extremely small as compared with the conventional electric resistance heating system. Even if the sample 2 dissipates the temperature due to heat conduction, it can maintain a local high temperature without a large amount of dissipated heat if it is a thin film that can transmit the observation electron beam. Thus, sample 2 may have a limited, very localized high temperature, for example, 2000 ° C. or more if necessary.

Further, in this case, since the reached temperature depends on the density and the amount of the heating electron beam 5, even if the sample 2 is heated, only a minute local portion is heated to a high temperature, so that the generated total heat amount is small and the ambient temperature is reduced. Can be kept low. Therefore, if light shielding is considered around the objective lens 3, the heat insulation structure and material can be simplified.

On the other hand, when the heating area is too small, the irradiation range is widened by shifting the beam focus in the axial direction by changing the acceleration voltage or moving the heating electron gun 1 or the heating position is changed to the sample 2. When it is shifted upward, it is easy to change the heating mode, for example, by changing the incident angle or the incident position of the heating electron beam 5 on the objective lens 3. Also in this case, as shown in FIG.
Although the light is obliquely incident on the center position of the virtual lens 7, the trajectory is corrected while the light is repeatedly focused and refracted, and finally the sample 2 is irradiated in a state substantially coincident with the beam path of the observation electron beam 6. Will be done. Further, the mode of heating is not limited to the method of always continuously irradiating the beam, and the temperature may be adjusted by, for example, intermittent irradiation.

The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the heating electron beam gun 1 is disposed at a position slightly retracted from the optical path of the observation electron beam 6, and the heating electron beam 5 is angled with respect to the optical axis 9 of the observation electron beam 6. However, the present invention is not particularly limited to this, and a ring-shaped heating electron beam source (not shown) is provided around the optical axis 9 of the observation electron beam, and the optical axes of the heating electron beam are mutually aligned. Irradiation may be performed so as to be almost the same. In any case, the heating electron beam 5 and the observation electron beam 6 are irradiated simultaneously or as required, if necessary, so that the heated sample can be observed. In addition, when heating and observing the sample, if it is acceptable to observe the sample while heating or to observe after heating, it is also possible to heat a part that is not the observed part and to observe the condition. Is not bound at all.

Further, in the present embodiment, the sample 2 is disposed between the lens pole pieces of the objective lens 3 (between the poles), and the heating electron beam 5 is directed upward of the objective lens 3 of the sample 2 (in FIG. 1). Although the light is made incident, the present invention is not particularly limited to this, and the sample may be arranged near the pole piece of the objective lens.

Although the electron microscope of the present embodiment has been described as being provided with the heating electron gun 1 from the beginning, it is also possible to additionally install the heating electron gun 1 on an existing electron microscope. The heating method of the present invention can be realized, and the sample 2 can be heated at a high temperature with a relatively simple configuration. Furthermore, in the present embodiment, an example in which the present invention is applied to a transmission electron microscope is mainly described, but the present invention is not particularly limited to this, and the present invention is applied to a scanning electron microscope (SEM) or a scanning electron microscope (STEM). Is also possible. In any case, it suffices that the heating electron beam 5 is focused on the sample 2 via at least the lens action portion (lens magnetic field) of the electron lens including the sample 2 on the optical path of the observation electron beam 6. . In this embodiment, the sample 2 is irradiated with the observation electron beam 6 and the heating electron beam 5 from the same surface side. However, in some cases, the observation electron beam 6 and the heating electron beam 5 are irradiated. 5 may be directed toward the objective lens 3 from opposite directions.

[0029]

As is apparent from the above description, according to the first and eighth aspects of the present invention, the action magnetic field of the electron lens including the sample on the optical path of the observation electron beam is focused on the heating electron beam. Because the beam diameter is extremely small and the electron density is increased to locally heat the sample, even if it is heated to an extremely high temperature, the amount of heat generated is extremely small compared to the electric resistance heating method. Dissipation of heat due to heat conduction is small, and a local high temperature can be maintained without thermally affecting the surroundings. Therefore, it is possible to observe the behavior of the sample at a high temperature which could not be observed conventionally.

Moreover, the ultimate temperature depends on the density and amount of the heating electron beam, and there is no problem with the conventional heat source such as the material of the heating element for resistance heating. Can be determined. Further, in this electron microscope, even if the sample is heated, only the minute local portion is heated to a high temperature, so that the total heat generated is small and the ambient temperature can be kept low, so that the structure around the sample can be simplified. At the same time, the sample holder does not need to be made of a material that can withstand the local maximum temperature reached by electron beam heating, and it suffices to consider thermal insulation with the sample and mild shielding of radiant heat.

According to the second aspect of the present invention, since the sample is set between the poles of the objective lens or in the vicinity thereof, the magnetic field acting on the lens including the sample is extremely strong. Has a strong focusing effect, and heats a minute local area with a high-density electron beam, thereby reducing the influence of heat on the surroundings.

According to the third and fourth aspects of the present invention, the heating electron beam is heated simultaneously or shifted from the coaxial or close angle to the optical axis of the observation electron beam as needed, or while heating an arbitrary portion. Since observation is possible after heating, there is no restriction on observation conditions.

According to the electron microscope of the fifth aspect, by adjusting the acceleration voltage, the heating mode can be changed by shifting the focus or changing the energy of the heating electron beam. Therefore, various behaviors of the sample under various heating conditions can be observed.

According to the electron microscope of the sixth aspect,
By changing the incident angle and incident position of the heating electron beam, it is possible to easily change the heating position on the sample and create various heating conditions and observation conditions.

Further, according to the electron microscope of the seventh aspect, the temperature of the sample can be appropriately adjusted by intermittent irradiation of the heating electron beam.

[Brief description of the drawings]

FIG. 1 is a view showing the principle of local heating by an electron beam according to the present invention, and shows a case where a sample is incident on a sample inside an electron microscope.
2 shows the paths of two electron beams.

FIG. 2 is a partial longitudinal sectional view of an electron microscope showing an example of a structure near an objective lens and a positional relationship of a heating electron gun.

FIG. 3 is a partial longitudinal sectional view of the inside of an electron microscope showing an example of a conventional electron microscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating electron gun 2 Sample 3 Objective lens (Electronic lens containing the sample on the optical path of the observation electron beam) 5 Heating electron beam 6 Observation electron beam 7 Virtual lens for heating electron beam 9 Observation electron beam optical axis

Continued on the front page (72) Inventor Hideo Kusanagi 2-1-1-1, Iwatokita, Komae-shi, Tokyo F-term in the Komae Research Center, Central Research Institute of Electric Power Industry 2G001 AA03 BA07 BA11 CA03 RA03 RA20 5C001 BB01 CC01 5C033 SS01 SS02 SS10

Claims (8)

[Claims] In an electron microscope capable of heating a sample to be observed without changing lens conditions during observation, a heating electron beam having an acceleration voltage lower than that of the observation electron beam is irradiated with light of the observation electron beam. An electron microscope, comprising: a heating electron beam source that irradiates an electron lens on a road including the sample and heats the sample via a lens working portion of the electron lens. 2. The electron microscope according to claim 1, wherein the electron lens is an objective lens, and the sample is placed between or near the poles. 3. The electron microscope according to claim 1, wherein the heating electron beam source is disposed at a portion that can be irradiated simultaneously with the observation electron beam. 4. The heating electron beam source according to claim 3, wherein the heating electron beam source is arranged at a position where the electron beam can be irradiated toward the electron lens from an angle coaxial with or close to the optical axis of the observation electron beam. electronic microscope. 5. The electron microscope according to claim 1, wherein the heating electron beam source has a variable acceleration voltage. 6. The electron microscope according to claim 1, wherein the heating electron beam source changes an incident angle or an incident position of the electron beam on the electron lens. 7. The electron microscope according to claim 1, wherein said heating electron beam source is capable of intermittently irradiating an electron beam. 8. A heating method for heating a sample to be observed in an electron microscope, wherein the heating electron beam irradiated at an acceleration voltage lower than the observation electron beam is provided on the optical path of the observation electron beam. Irradiating an electron lens including: and heating the sample using the electron lens for focusing of the heating electron beam.