JPH08222161A - Microminiature scanning electron microscope - Google Patents

Abstract

PURPOSE: To provide a microminiature scanning electron microscope capable of incorporating a surface analyzer or the like. CONSTITUTION: An electron gun unit 10 is provided with a hole through which the outside atmospheric air is communicated with an electron gun room, and the electron gun room can be exhausted by an exhausting means such as a surface analyzer. All electrodes of a low-acceleration field emission electron gun unit are assembled on an insulator, deflectors 70, 71 are made the electrostatic type, a covered wire of alumina is used for the coils of magnetic field type lenses 40, 90, and a microminiature scanning electron microscope coping with ultra-high vacuum is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscopic scanning electron microscope which can be incorporated into a surface observation or surface analysis device (hereinafter referred to as a surface analysis device).

[0002]

2. Description of the Related Art A scanning electron microscope (SEM) is used for surface observation and analysis, but a high accelerating voltage is required because of high spatial resolution, and an auxiliary device for improving operability. Therefore, the size of the entire device tends to increase. SE with such high spatial resolution
A field emission electron gun (FEG) is used as the M electron gun because of its high brightness. Figure 4 shows such FE
It is a figure explaining a G unit. The gun chamber 11 and the lens barrel 20 are structured so that they can be separated from each other at the point A for the exchange of the filament. Inside the gun chamber 11,
In order to facilitate discharge countermeasures, a filament 13 to which a high voltage (negative potential) is applied on the insulator 12, the suppressor electrode 1
4. The extraction electrode 15 is assembled together. On the other hand, the anode 16 (ground potential) for accelerating the emitted electrons is incorporated in the lens barrel 20. In this way, FEG
The unit 10 is composed of a combination of two units as a whole, and thus becomes large. Further, in the high resolution SEM, as shown in FIG.
The sample 22 is irradiated with the electron beam emitted from 0 through the liner tube 21 made of metal. Since the electron beam passes through the metal cylinder, the magnetic field type lens 24 is used, and the coil and the coil 23 forming the deflection system are arranged on the atmosphere side. It is not necessary to consider measures for the coil vacuum by disposing it on the atmosphere side. Also, the exhaust will be performed only in the liner tube.

[0003]

In fields such as ESCA (chemical analysis using electron spectroscopy) used for surface observation and surface analysis, STM (scanning tunneling microscope), LEED (low energy electron diffraction device), etc. There is a request to install the SEM in. However, in these fields, since the device is designed around each analysis technique, even if the SEM is incorporated, it cannot be incorporated due to the large size of the SEM, or if the SEM is incorporated, the operation is not performed. Inevitably, the distance must be increased, and the performance is worse than that of a dedicated SEM. Also, SE
When M is installed in the analysis chamber, it is necessary to maintain an ultrahigh vacuum in the analysis chamber, but because the gas emitted from the coils that make up the deflector and lens of the SEM is large, it is possible to exhaust to an ultrahigh vacuum. Moreover, since the liner tube is a thin pipe, if the pipe length becomes long, the pumping capacity of the pump may deteriorate, and the inside of the pipe may not be evacuated to an ultrahigh vacuum. Therefore, it is difficult to incorporate a device of the same system as a conventional SEM into a surface analysis device or the like. The present invention is intended to solve the above problems, and an object of the present invention is to provide an ultra-compact scanning electron microscope which can be incorporated in a surface analysis device or the like and has a structure compatible with ultra-high vacuum.

[0004]

SUMMARY OF THE INVENTION The present invention is a micro-scanning electron microscope mounted on a flange and incorporated in a surface analysis / observation apparatus under vacuum, wherein the electron gun unit is provided with an external atmosphere in the electron gun chamber. A hole for communication is provided so that the electron gun chamber can be exhausted by the exhaust means of the surface analysis / observation apparatus. Further, according to the present invention, all the electrodes of the low-acceleration field emission electron gun unit are assembled on the insulator, the scanning deflector is electrostatic type, and the coil of the magnetic field type lens is formed of a coated wire material such as alumina or silica. Is characterized by.

[0005]

According to the present invention, the electron gun unit is provided with a hole for communicating with the external atmosphere so that the exhaust of the electron gun chamber can be exhausted by an exhaust device such as a surface analysis device incorporated therein.
The exhaust pump for exhausting the electron gun can be omitted. In addition, by assembling all the electrodes of the FEG unit on the insulator, the assembly accuracy is improved and the size is reduced, and the gas emitted from the coil is formed by using a wire rod coated with alumina or silica for the coil that constitutes the magnetic field lens. By reducing the number, it is possible to support ultra-high vacuum, and by using an electrostatic deflector as the deflector, it is possible to install the coil in an analysis chamber such as a surface analysis device without using a coil.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of a microminiature low acceleration scanning electron microscope of the present invention. In the present embodiment, the support 1 (diameter 2) is attached to the mounting flange 2 (70φ, international standard).
6φ) is attached, and the scanning electron microscope main body designed to have a total length of 142 mm is held on this. A power supply connection flange 3 is connected to the mounting flange 2 so that power is supplied to the scanning electron microscope main body. An analysis room (not shown) such as a surface analysis device having such a micro structure
Built in. In addition, since the operating distance varies depending on the device to be incorporated, in that case, the length of the support is appropriately changed and attached.

In the FEG unit 10, as shown in FIG. 2, the filament 13, the suppressor electrode 14, the extraction electrode 15, and the anode 16 are all assembled on the insulator 12, and a hole H penetrating each of these electrodes is provided to form an electron gun unit. The electron gun chamber is configured to communicate with the external atmosphere. In a surface analyzer or the like, observation at 5 KV or less is more advantageous than observation at a high acceleration voltage in order to obtain more surface information. However, in low-acceleration FEG, a magnetic shield is required to eliminate the influence of the magnetic field, but in surface analyzers and the like, the magnetic shield is applied inside or outside the analysis chamber,
No magnetic shield dedicated to FEG is required. Further, since the accelerating voltage is low, the FEG electrode structure can be easily insulated,
Even if four electrodes are assembled on the insulator to form a unit, no problem such as discharge occurs.

Further, in order to operate the FEG, an ultrahigh vacuum (10 ^-10 Torr) is required, and in the conventional FEG, a SIP (sputter ion pump) with a high pumping speed is used to obtain the ultrahigh vacuum. Was needed. Conventional F
Although the EG unit is large and the SIP can be connected to the FEG unit, the SIP cannot be connected to the FEG unit having a length of about 20 mm shown in FIG. Therefore, in the present invention, as shown in FIG. 2, a hole H penetrating the electron gun chamber is provided in the electron gun unit, and the hole H is passed through the hole H by an exhaust pump that exhausts the analysis chamber to an ultrahigh vacuum (10 ⁻¹⁰ Torr). Evacuate the electron gun chamber. Therefore, the FEG unit of the ultra-small FEG scanning electron microscope having a short total length can be evacuated to an ultrahigh vacuum, and a scanning electron microscope image with high resolution can be obtained. Note that the thermionic emission type electron gun does not require an ultra-high vacuum unlike FEG, but does require a high vacuum. Therefore, in a microminiature thermionic emission scanning electron microscope equipped with a thermionic emission type electron gun,
When a hole penetrating the electron gun chamber is provided in the electron gun unit, the electron gun chamber can be evacuated to a high vacuum through the hole by an exhaust pump that evacuates the analysis chamber, and a high resolution scanning electron microscope image can be obtained. . Since the accelerating voltage is low in this way, four electrodes can be assembled on the insulator into a unit, a dedicated magnetic shield is not required, an exhaust pump is not required, and the FEG unit can be miniaturized. Since the assembly accuracy can be checked with the four electrodes incorporated, the optical axis during operation can be accurately obtained.

An electron gun alignment (for optical axis adjustment) 30, a condenser lens 40, a condenser lens alignment (for optical axis adjustment) 50, an aperture (aperture) 60, and a deflector are provided in a lens barrel 20 having a diameter of 26φ and a total length of 142 mm. 7
0, 71, astigmatism correctors 80, 81, and an objective lens 90 are incorporated. As described above, the low accelerating voltage allows the coil and the like to operate even if the coil is small, so that the magnetic field lens can be downsized. However, since the analysis chamber is in an ultrahigh vacuum, the gas emitted from the coil material of the magnetic field lens poses a problem. The conventional polyimide coated wire emits a large amount of gas,
Cannot exhaust to ultra-high vacuum. Therefore, in the present invention, a wire rod (copper wire) coated with alumina (Al ₂ O ₃ ) or silica is used as the coil of the magnetic field type lens of the condenser lens 40 and the objective lens 90, and as shown in FIG. It is placed on the (UHV) side. By using such a covered wire rod, the released gas can be reduced and exhausted to an ultrahigh vacuum.

Further, unlike the conventional case, since a liner tube is not used, electrostatic deflectors can be used as the deflectors 70 and 71. By using an electrostatic deflector, no coil is required, and there is no problem even under ultra-high vacuum,
Also, the number of lead wires required for the deflector of the magnetic field type can be reduced to almost half, and the deflector can be miniaturized.
It is possible to use a coated wire rod such as alumina to form a magnetic field type deflector, but the coil of the deflector is small (10
mm φ), so if you wind a coated wire such as alumina,
The coil radius is 5 mm, and the coating is torn to cause poor insulation, which is not preferable as a small coil for a deflector or the like.

Since the entire apparatus is miniaturized in this way,
Although the current density of the coil for operating the magnetic field lens is limited, when the overall outer diameter is φ26, the voltage of the electron gun can be operated up to 5 KV, and even if the maximum of 5 KV is limited, the electron gun can be operated. By using FEG as the source of, the function as SEM can be sufficiently maintained even at a low acceleration voltage. The FEG of this size has an acceleration voltage of 130 eV and a luminance of 10 ⁷ A / cm ² · str.

In the above embodiment, the FEG unit was incorporated into the international standard of 70 mmφ, but the mounting flange may be changed according to the intended device.
Further, as the lens configuration, a condenser lens is incorporated, but this has a mode in which the current density is variable, and is also applicable to analysis such as AES (Auger electron spectrometer) that requires a large current density. This is because, if it is used only in the SEM mode, the condenser lens can be omitted and only the objective lens can function, and further miniaturization can be achieved.

[0013]

As described above, according to the present invention, the electron gun unit is provided with a hole for communicating with the external atmosphere so that the exhaust of the electron gun chamber can be exhausted by an exhaust device such as a built-in surface analyzer. Therefore, the electron gun chamber can be evacuated without connecting an exhaust device to the microminiature electron gun unit, and a high-resolution scanning electron microscope image can be obtained.
In addition, all four electrodes of the FEG unit are assembled on the insulator to form a unit, and the dedicated magnetic shield and exhaust pump are not required, so that the FEG unit can be downsized, and the coil that constitutes the magnetic field lens is coated with alumina. It is possible to cope with ultra-high vacuum by reducing the gas released from the coil by using the wire rod, and by using the electrostatic deflector as the deflector, the coil is not required and the entire device is miniaturized and the surface analysis device, etc. Can be incorporated into.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a microminiature low-acceleration scanning electron microscope of the present invention.

FIG. 2 is a diagram illustrating an electron gun unit of the present invention.

FIG. 3 is a diagram illustrating a magnetic field type lens of the present invention.

FIG. 4 is a diagram showing a conventional electron gun unit.

FIG. 5 is a diagram illustrating a magnetic field type lens of a conventional SEM.

[Explanation of symbols]

1 ... Support, 2 ... Mounting flange, 3 ... Power connection flange, 10 ... Electron gun unit, 12 ... Insulator, 13 ... Filament, 14 ... Suppressor electrode, 15 ... Extraction electrode, 16 ... Anode, 20 ... Lens barrel, 30 ... Electron gun alignment, 40 ... Focusing lens, 50 ... Focusing lens alignment, 60 aperture, 70, 71 ... Deflector, 80, 81
... astigmatism corrector, 90 ... objective lens.

Claims (2)

[Claims] 1. A microscanning electron microscope mounted on a flange and incorporated in a surface analysis / observation apparatus under vacuum, wherein an electron gun unit is provided with a hole for communicating the outside atmosphere with the electron gun chamber. Surface analysis of chamber exhaust /
An ultra-compact scanning electron microscope characterized in that it can be performed by an exhaust means of an observation device. 2. A microscopic scanning electron microscope mounted on a flange and incorporated in a surface analysis / observation apparatus under vacuum, wherein all electrodes of a low acceleration field emission electron gun unit are assembled on an insulator and scanning is performed. A microminiature scanning electron microscope characterized in that the deflector for use is an electrostatic type, and the coil of the magnetic field type lens is formed of a coated wire material such as alumina or silica.