JP2000208089A - Electron microscope device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform both observation by a scanning electron microscope and observation by a photo-electron microscope by using a single device without moving a sample. SOLUTION: When this device is used as a scanning electron microscope, a lens barrel 2 is kept at the same potential as that of a sample 4, and a negative potential is applied to an electron gun 1. The electrons emitted from the electron gun 1 are converged by electron lenses 13, 14 of the lens barrel 2 and scanned on the sample 4 by deflection coils 15, 16. The secondary electrons from the sample 4 are detected and converted into an electric signal by a secondary electron detector 5, and displayed on a secondary electron image display means 8. When the device is used as a photo-electron microscope, a positive acceleration voltage is applied to the lens barrel 2. An ultraviolet-ray is applied on the sample 4 from a mercury lamp 6, and the image of the photo-electrons from the surface of the sample 4 is focused on a photo-electron detector 17 by the electron lenses 13, 14. The focused image of the photo-electrons is converted into an electric signal and displayed on a photo-electron image display means 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electron microscope apparatus.

[0002]

2. Description of the Related Art Conventionally, a scanning electron microscope or an emission microscope has been known as an electron microscope apparatus for observing an image of a sample surface by detecting electrons emitted from the sample surface. A scanning electron microscope scans a sample surface with a finely narrowed primary electron beam, detects secondary electrons and reflected electrons generated from an electron beam irradiation area, and determines the signal intensity by scanning the primary electron beam. It is displayed on the screen in synchronization.
On the other hand, an emission microscope is a method in which photoelectrons and thermal electrons emitted from a sample surface are imaged by an electron lens to form an enlarged image of the sample surface. In particular, when the emitted electrons are photoelectrons, it is called a photoelectron microscope.

[0003] The spatial resolution of a scanning electron microscope is determined by the spot size of a primary electron beam on the sample surface.
For example, in the latest scanning electron microscope equipped with a field emission electron gun, a high spatial resolution of 1 nm or less has been achieved. However, in order to obtain such a high spatial resolution, it is necessary to narrow down the electron beam and detect a sufficient amount of secondary electron signals. Therefore, an observation region is scanned to form one image. It takes several minutes to complete. In contrast, a photoelectron microscope collects image signals formed on the image plane and collects a single photoelectron image. Is possible. However, the spatial resolution of photoelectron microscopes is orders of magnitude worse than scanning electron microscopes,
At present, it is about 100 nm (Ultramicroscopy 36
(1991) 148-153 (Authors: W. Engel, MEKordesh, HHRo
termond, S.kubala, Oertzen).

When the time required to acquire one image of the sample surface is defined as time resolution, the scanning electron microscope has a high spatial resolution and a low time resolution as described above, whereas the photoelectron microscope has a spatial resolution. Have low but high temporal resolution and are complementary to each other. In addition, while a scanning electron microscope mainly detects secondary electrons, a photoelectron microscope detects photoelectrons, and the information obtained from both microscope devices is fundamentally different due to the different generation mechanism. Is different. Therefore, depending on the purpose, it is often the case that information on both the scanning electron microscope and the photoelectron microscope is desired for the same sample. But,
Conventionally, since these two electron microscopes are independent and separate devices, it has not been possible to observe both a scanning electron microscope image and a photoelectron microscope image using the same device.

[0005]

In order to evaluate a phenomenon that changes on a solid surface, for example, a chemical reaction of a catalyst or the like, a surface diffusion of a substance, or an electron emission phenomenon from an electron-emitting device, a photoelectron that can be observed in real time is used. A microscope is suitable.
When observing the dynamic phenomena of the surface, heating of the sample, introduction of gas, or application of voltage to the sample may be performed to cause a change. It is necessary to observe the surface in detail with an electron microscope.

However, as described above, in the conventional apparatus configuration, the scanning electron microscope and the photoelectron microscope are independent and completely separate apparatuses. Therefore, both the scanning electron microscope image and the photoelectron microscope image are obtained using the same apparatus. It cannot be observed. In order to observe with both microscope devices, it was necessary to perform observation with one microscope device, and then take the sample out into the atmosphere and reset it to the other microscope device. Such an operation is not only time-consuming but also undesirable because the surface state of the sample may change due to exposure to the atmosphere.

Accordingly, an object of the present invention is to provide a scanning electron microscope having both the functions of a scanning electron microscope and a photoelectron microscope in a single apparatus without removing or resetting the sample from the apparatus. It is an object of the present invention to provide an electron microscope device capable of performing observation by a TEM and observation by a photoelectron microscope.

[0008]

The electron microscope apparatus of the present invention is characterized by an electron beam generating means, a scanning means for scanning an electron beam emitted from the electron beam generating means on a sample surface, and an electron beam. A secondary electron detector for detecting secondary electrons emitted from the sample when the sample is irradiated, and synchronizing the signal intensity of the secondary electrons detected by the secondary electron detector with the scanning of the electron beam. Secondary electron image display means for displaying, light irradiating means for irradiating the sample with light, photoelectron detector for detecting photoelectrons emitted from the sample when irradiated with the light, and detection by the photoelectron detector A photoelectron image display means for displaying an intensity signal of the photoelectrons, and when the electron beam is irradiated from the electron beam generation means, the electron beam is focused on the sample surface, and the light is irradiated from the light irradiation means. When There photoelectrons emitted from the sample where having optical means for focusing the photoelectron detector.

According to such a configuration, it is possible to observe a sample as a scanning microscope and also to observe a sample as a photoelectron microscope. In addition, since the common optical means is used, images of both the photoelectron microscope and the scanning electron microscope can be observed only by changing the electrical settings of the apparatus without moving the sample.

An electron lens for converging the electron beam on the surface of the sample when the optical means scans the electron beam, and an electron for imaging the photoelectron when the photoelectron is emitted from the sample. And a configuration in which the optical axes of both electron lenses substantially coincide with each other. Alternatively, the electron lens of the optical means focuses the electron beam on the sample surface when scanning the electron beam, and when the photoelectrons are emitted from the sample, the photoelectrons are sent to the photoelectron detector. An image may be formed.

[0011] The light irradiation means may be a mercury lamp for irradiating ultraviolet rays.

[0012] The scanning means may be a deflection coil.

Further, it is preferable that an electrode for applying a voltage to the sample and a heater for heating the sample are provided on a sample stage on which the sample is placed. In this case, observation of the sample under various conditions can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An electron microscope apparatus according to a first embodiment of the present invention shown in FIG. 1 is disposed above a lens barrel 2 and an optical axis of the lens barrel 2. Electron beam generating means. The electron beam generating means is an electron gun that emits thermoelectrons, field emission electrons, or the like. In the present embodiment, the electron beam generating means is a thermionic electron gun 1 that emits electrons by heating the filament 10 by heating. The thermoelectron emission type electron gun 1 has a Wehnelt electrode 11 for forming a crossover point of emitted electrons and an extraction electrode 12.

The lens barrel 2 includes an optical unit including a plurality of electron lenses, a scanning unit that scans a primary electron beam emitted from the electron gun 1, a photoelectron detector 17 for detecting a photoelectron image, and Is provided.

The optical means of the present embodiment comprises an objective lens 13 and a projection lens 14 which are three-pole type electrostatic lenses, and functions as a means for focusing a primary electron beam during observation with a scanning electron microscope. Sometimes it acts as a means of imaging photoelectrons. That is, the projection lens 14 functions as a projection lens during observation with a photoelectron microscope, and functions as a focusing lens during observation with a scanning electron microscope.

The scanning means of this embodiment comprises a deflection coil 15 in the X and Y directions, and a deflection coil 16 connected in the opposite direction to the deflection coil 15, and these two upper and lower deflection coils 15, 16 are provided. The primary electron beam emitted from the electron gun 1 is scanned.

Further, the photoelectron detector 17 of the present embodiment
Is a plate-type two-dimensional detector in which a multi-channel plate, a phosphor and a CCD are integrated, and has a diameter of 5
A slit having an effective area of 0 mm and a diameter of 0.5 mm is formed at the center thereof, through which an electron beam can pass.

A sample stage 3 equipped with a moving mechanism capable of finely moving three-dimensionally and a rotating mechanism having the optical axis of the lens barrel 2 as a rotation axis is provided so as to face the lens barrel 2. In the vicinity of the sample stage 3, a secondary electron detector 5 for detecting secondary electrons, a mercury lamp (light irradiation means) 6 for irradiating ultraviolet light, and a mercury lamp 6 and a sample stage 3 A quartz port 7 located between them is provided.

In this embodiment, the secondary electron image display means 8 connected to the secondary electron detector 5 and the photoelectron detector 17
And an opto-electronic image display means 9 connected to the camera.

The vacuum vessel 18 including the lens barrel 2 and the electron gun 1 are held in a vacuum atmosphere by a differential pumping system.

When the electron microscope apparatus of this embodiment having such a configuration is used as a scanning electron microscope, the lens barrel 2 is held at the same potential as the sample 4 set on the sample stage 3, and the electron gun 1 Has a negative potential-
Va is applied. Electrons emitted from the electron gun 1 are accelerated by the acceleration voltage Va and enter the lens barrel 2. Subsequently, the electron beam is focused on the surface of the sample 4 by optical means (electron lenses 13 and 14) arranged in the lens barrel 2, and
The observation area of the sample 4 is scanned by the scanning means (deflection coils 15 and 16). Secondary electrons generated from the sample 4 irradiated with the electron beam are detected by the secondary electron detector 5 and converted into electric signals, and displayed on the secondary electron image display means 8 as a scanning electron microscope image.

On the other hand, when the electron microscope apparatus of the present embodiment is used as a photoelectron microscope, a positive acceleration voltage Va is applied to the lens barrel 2 with respect to the sample 4. When ultraviolet rays are irradiated from the mercury lamp (light irradiation means) 6 toward the sample 4, photoelectrons emitted from the surface of the sample 4 in response to the ultraviolet rays are accelerated by the acceleration voltage Va and placed in the lens barrel 2. The formed electron lenses 13 and 14 form an image on a photoelectron detector 17 which is a plate-type detector. The formed photoelectrons are converted into electric signals by the photoelectron detector 17 and displayed on the photoelectron image display means 9 as a photoelectron microscope image. When the observation is performed as a photoelectron microscope in this manner, the operating conditions of the electron gun 1 are not particularly limited.
Is not operated, or the primary electron beam is
The acceleration voltage and the like of the electron gun 1 are set so as not to enter.

The entire electron microscope apparatus is held in a vacuum by a suitable exhaust system, but a mercury lamp (light irradiation means) 6 for generating photoelectrons is usually placed outside a vacuum vessel 18 to emit light. Sample 4 through quartz port 7
Irradiation on the surface.

The electron gun 1 and the lens barrel 2 of this embodiment can set an acceleration voltage independently with respect to the sample stage 3, and can be used when the apparatus is used as a scanning electron microscope.
Secondary electrons are accelerated by the electron gun 1, and photoelectrons when used as a photoelectron microscope are accelerated in a space from the surface of the sample 4 to the lens barrel 2.

The applicant has specifically measured the spatial resolution of the electron microscope apparatus of the present embodiment as a photoelectron microscope. A sample obtained by depositing a stripe-shaped gold pattern on a silicon wafer was set as an observation sample 4 on a sample stage 3. Then, first, the sample stage 3
The potential of the lens barrel 2 with respect to
The voltage was set to kV, and the surface of the sample 4 was irradiated with ultraviolet rays through a quartz port 7 from a mercury lamp 6 as light irradiation means. Photoelectrons generated from the sample 4 are detected by the photoelectron detector 17 in a state where the lens conditions of the electronic lenses 13 and 14 are appropriately set. The photoelectron image was displayed on the photoelectron image display means 9, and while observing the photoelectron image, the voltages of the objective lens 13 and the projection lens 14 were adjusted to set the focus and magnification of the photoelectron image. At this time, the objective lens 13 functions mainly for focus adjustment, and the projection lens 14 functions mainly for magnification setting. As a result of defining the interval until the contrast difference of the edge profile of the gold pattern changes from 10% to 90% as the spatial resolution, the resolution as a photoelectron microscope was about 200 nm. Also,
Video recording of a photoelectron microscope image while moving the sample, and playback with frame-by-frame playback proved to have a time resolution at least higher than the TV rate (60 fields / second).

Next, the spatial resolution of the electron microscope apparatus of this embodiment as a scanning electron microscope was measured. The lens barrel 2 is set to the same potential as the sample 4 and the electron gun 1
The acceleration voltage of the primary electrons generated from is set to 25 kV,
The filament 11 is energized and heated to emit primary electrons,
With the lens conditions of the electron lenses 13 and 14 appropriately set, electron beams were scanned in a rectangular region on the surface of the sample 4 using the deflection coils 15 and 16. Sample 4 by electron beam irradiation
Is detected by the secondary electron detector 5,
The image is displayed on the secondary electron image display means 8 as a secondary electron image.
When the objective lens 13 was adjusted and focused while observing the secondary electron image, it was confirmed that the same field of view as that of the above-described photoelectron image observation could be observed without moving the sample 4. When the distance between the observed gold pattern islands was measured, the resolution as a scanning electron microscope was 30%.
nm.

Since the conditions of the electron lenses 13 and 14 are electrically controlled by an external control device (not shown), switching between observation with a photoelectron microscope and observation with a scanning electron microscope is performed as follows.
This is executed by changing the setting of the control device. As described above, according to the present invention, it is possible to observe images of both the photoelectron microscope and the scanning electron microscope without changing the sample 4 and only by changing the electrical settings of the apparatus. The time required to switch between scanning electron microscope observation and photoelectron microscope observation depends on the accelerating voltage and the electron lenses 13 and 1.
It was determined by the time for setting each lens condition of No. 4 and was about 5 minutes as an actually measured value. This time can be further reduced by automatically setting the observation conditions.

[Second Embodiment] FIG. 2 shows a second embodiment of the present invention. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The electron gun 19 of this embodiment is a field emission type electron gun having a filament 28 and two upper and lower extraction electrodes 29.

The lens barrel 20 is provided with an objective lens 30, an intermediate lens 31, and a projection lens 32 as magnetic field type electron lenses. The intermediate lens 31 and the projection lens 32 function as a focusing lens during observation with a scanning electron microscope. In addition to the upper and lower two-stage deflection coils 15 and 16 for electron beam scanning, a beam tilt deflection coil 33 for adjusting the tilt of the electron beam is provided. Above the objective lens 30, a stigmator for astigmatism correction for correcting astigmatism and an objective aperture 37 for narrowing the electron beam are provided.

The sample stage 21 has a three-axis moving mechanism and a rotating mechanism in the same manner as the sample stage 3 of the first embodiment. An electrode (not shown) and a resistance heating type heater (not shown) for heating the sample 4 are provided.

Although not explicitly shown in FIG. 2, the lens barrel 2
The inside of the vacuum chamber 39, the vacuum vessel 39, and the electron gun 19 are independently maintained in vacuum by three differential exhaust systems. However, the vacuum vessel 39 of the present embodiment is provided with an inlet 40 for introducing various gases.

In this embodiment, as a result of examining the resolution by the same method as in the first embodiment, the spatial resolution as a photoelectron microscope was 70 nm, and the spatial resolution as a scanning electron microscope was 5 nm.

Next, a Spindt-type electron-emitting device was observed using the electron microscope apparatus of the present embodiment. The Spindt-type electron-emitting device is a device that emits electrons from a minute structure in a field, and is attracting attention and studied as a material for realizing a flat display. This Spindt-type electron-emitting device was set as a sample 4 on a sample stage 21 and observed.

According to the present embodiment, the electrodes and the heater are provided on the sample stage 21. By energizing the electrodes to drive the electron-emitting devices, the electron-emitting device can be used in addition to observing a photoelectron image as a photoelectron microscope. By observing an electron emission image due to the field emission from the device, it is possible to evaluate the time change of the brightness and the shape. Further, before and after this driving, a secondary electron image is obtained by a scanning electron microscope, and by comparing the two, it is also possible to analyze the mechanism of deterioration of the element due to electron emission. Sample stage 2
It is also possible to examine in detail the effects of heating the sample 4 by the heater 1 and the introduction of various gases from the inlet 40 on the element.

As described above, according to the present invention, by realizing the functions of the photoelectron microscope and the scanning electron microscope with the same device, the characteristic evaluation and the structure evaluation of the electron-emitting device can be performed in detail and simply.

[0038]

According to the present invention, observation of a photoelectron image and observation of a secondary electron image of the same sample can be performed by simple switching with a single electron microscope apparatus. Since it is not necessary to reset the sample, the observation of the photoelectron image and the observation of the secondary electron image can be performed under exactly the same conditions.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electron microscope device according to a first embodiment of the present invention.

FIG. 2 is a schematic view of an electron microscope device according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 electron gun (electron beam generating means) 2 lens barrel 3 sample stage 4 sample 5 secondary electron detector 6 light irradiation means (mercury lamp) 7 quartz port 8 secondary electron image display means 9 photoelectron image display means 10 filament 11 Wehnelt electrode 12 Leader electrode 13 Objective lens (optical means) 14 Projection lens (optical means) 15, 16 Deflection coil (scanning means) 17 Photoelectron detector 18 Vacuum container 19 Electron gun (electron beam generating means) 20 Lens barrel 21 Sample Stage 28 Filament 29 Extraction electrode 30 Objective lens (optical means) 31 Intermediate lens (optical means) 32 Projection lens (optical means) 33 Beam tilt deflection coil 36 Stigmatol for astigmatism correction 37 Objective aperture 38 Photoelectron detector 39 Vacuum container 40 Inlet

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G001 AA03 AA07 BA07 BA08 CA03 FA16 GA01 GA06 GA09 HA13 JA03 JA04 JA13 JA14 JA20 KA01 PA07 RA03 SA02 SA04 5C033 NN01 NN10 NP05 NP06 UU03 UU04 UU10

Claims (6)

[Claims] 1. An electron beam generating means, a scanning means for scanning an electron beam irradiated from the electron beam generating means on a surface of a sample, and an electron beam emitted from the sample when irradiated with the electron beam.
A secondary electron detector for detecting a secondary electron; secondary electron image display means for displaying a signal intensity of the secondary electron detected by the secondary electron detector in synchronization with scanning of the electron beam; Light irradiating means for irradiating light on the sample, a photoelectron detector for detecting photoelectrons emitted from the sample when irradiated with the light, and a photoelectron image display for displaying an intensity signal of the photoelectrons detected by the photoelectron detector Means for converging the electron beam on the surface of the sample when the electron beam is irradiated from the electron beam generating means, and generating photoelectrons emitted from the sample when the light is irradiated from the light irradiation means. An optical means for forming an image on a photoelectron detector. 2. An electron lens for focusing the electron beam on a surface of the sample when scanning the electron beam, and forming an image of the photoelectron when the photoelectron is emitted from the sample. The electron microscope apparatus according to claim 1, further comprising an electron lens that causes the optical axes of the two electron lenses to substantially coincide with each other. 3. The electron lens of the optical means focuses the electron beam on the surface of the sample when scanning the electron beam, and converts the photoelectron into the photoelectron when the photoelectron is emitted from the sample. The electron microscope apparatus according to claim 1, wherein an image is formed on a detector. 4. The electron microscope apparatus according to claim 1, wherein said light irradiation means is a mercury lamp that irradiates ultraviolet rays. 5. An electron microscope apparatus according to claim 1, wherein said scanning means is a deflection coil. 6. The sample stage on which the sample is placed is provided with an electrode for applying a voltage to the sample and a heater for heating the sample. 3. The electron microscope device according to claim 1.