KR101236489B1 - High vacuum apparatus for electron gun in FE-SEM - Google Patents

Abstract

 An apparatus for efficiently generating ultra-high vacuum in an electron beam acceleration device for a field emission scanning electron microscope is provided. The ultra-high vacuum generator of an electron beam accelerator for a field emission scanning electron microscope including a vacuum chamber supplies an electron gun for emitting and accelerating an electron beam included in the vacuum chamber, and a high voltage power source for emitting and accelerating the electron beam to the electron gun. A getter pump power supply for supplying driving power for heating a heater of the getter pump using the high voltage power of the beam acceleration power supply as a reference potential, and a inside of the vacuum chamber; And a getter pump that operates using a drive power source.

Description

High vacuum apparatus for electron beam accelerators for field emission scanning electron microscopes {High vacuum apparatus for electron gun in FE-SEM}

The present invention relates to an apparatus for generating ultra-high vacuum in an electron beam acceleration device for a field emission scanning electron microscope.

Field emission scanning electron microscope (Field Emission Scanning Electron Microscope) is a device for observing the shape of the sample, microstructure, distribution of members, qualitative, quantitative and the like. Samples are mainly solid, powder and thin film samples of conductors such as metals, semiconductors such as ICs and oxides, insulating materials such as polymer materials and ceramics. A field emission scanning electron microscope uses a magnetic lens to narrow the electron beam, and detects electrons generated by scanning the electron beam on a sample surface. The field emission scanning electron microscope collects electrons emitted from a specimen and converts the collected electrons into a visible light image.

In field emission scanning electron microscopy, the electron beam is emitted in a high vacuum. The reason for maintaining the vacuum is to prevent charged particles emitted from the electron gun from colliding with molecules in the air until they reach the specimen. In order to maintain high vacuum, a plurality of ion pumps are installed and used on top of the field emission scanning electron microscope. However, additional components such as a plurality of ion pumps and a support for supporting the plurality of ion pumps are added to the field emission scanning electron microscope, which tends to increase the volume of the electron microscope and increase the manufacturing cost.

On the other hand, a high voltage of up to about 30 kV is used for the electron beam acceleration of the electron microscope. In contrast, the drive voltage supplied to the ion pump (eg, 5V) is very low, so that spark discharge occurs when the distance between the ion pump and the high voltage for electron beam acceleration is close. In order to prevent spark discharge, the ion pump is installed spaced apart from the electron microscope by a certain distance, which lowers the pumping capacity of the ion pump and delays the high vacuum arrival time.

 An apparatus for efficiently generating ultra-high vacuum in an electron beam acceleration device for a field emission scanning electron microscope.

An ultra-high vacuum generator of an electron beam acceleration device for a field emission scanning electron microscope including a vacuum chamber according to one aspect includes an electron gun for emitting and accelerating an electron beam included in the vacuum chamber, and for emitting and accelerating an electron beam to the electron gun. A beam acceleration power supply for supplying a high voltage power, a getter pump power supply for supplying driving power for heating a heater of the getter pump with the high voltage power of the beam acceleration power supply as a reference potential, and is provided inside the vacuum chamber, It includes a getter pump that operates using the driving power supply of the pump power supply.

The getter pump power supply may supply the driving power set such that spark discharge does not occur between the potential of the power supplied to the getter pump and the potential of the high voltage power.

The electron gun includes an emitter that emits electrons, a suppressor electrode that focuses the emitted electrons, a primary anode to which emission high voltage power is applied so that the electrons are emitted from the emitter, and the emitted electrons are accelerated. It may include a secondary anode to which the high voltage power of the beam acceleration power supply unit is applied.

The ultra-high vacuum generator includes an emitter heating supply for supplying power for heating the emitter using the high voltage power of the beam acceleration power supply as a reference potential, and a suppressor using the high voltage power of the beam acceleration power supply as the reference potential. A suppressor power supply for supplying the operating power of the electrode, and an electron emission power supply for applying the discharge high-voltage power to the primary anode by using the high-voltage power supply of the beam acceleration power supply to the reference potential.

The getter pump may be installed to be located above the secondary anode.

According to another aspect, a field emission scanning electron microscope includes an electron gun for emitting and accelerating an electron beam, a beam acceleration power supply for supplying a high voltage power for emitting and accelerating the electron beam, and a high voltage power supply for the beam acceleration power supply. And a getter pump power supply for supplying driving power for heating the heater of the getter pump at a reference potential, and a getter pump installed in the vacuum chamber and operated using the driving power of the getter pump power supply.

According to the present invention, when a getter pump is installed inside a vacuum chamber of an electron microscope and a drive voltage of the getter pump is generated using a high voltage for accelerating electron beams as a reference potential, a conventional use of an ion pump that is spaced apart from a vacuum chamber is used. In comparison, it is possible to reach the high vacuum state required by the electron microscope quickly. In addition, the getter pump can be safely operated while the electron microscope of the electron microscope is being driven to maintain a high vacuum state.

1 is a diagram illustrating an example of an electron microscope structure.
FIG. 2 is a diagram illustrating a detailed structure of an upper structure and a power supply of the electron microscope included in FIG. 1 according to an exemplary embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the terms described below are defined in consideration of the functions of the present invention, and this may vary depending on the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

1 is a diagram illustrating an example of an electron microscope structure.

The electron microscope 100 includes a field emission tip 112, an anode 114, a focusing lens 116, 118, an aperture 120, a scanning coil 122, an objective focusing electrode 124. The detector 140 may include a photomultiplier 150, a getter pump 160, and a power supply 200.

The electron microscope 100 irradiates an electron beam to the specimen 130 to provide information about the specimen 130. Components 112, 114, 116, 118, 120, 122, 124, 140 included in the electron microscope are included in the vacuum chamber 110.

The electron beam 10 emerging from the field emission tip 112 is accelerated at the anode 114 to form a mono-chromatic electron beam that is focused by the focusing lenses 116, 118, which are electromagnetic lenses. The field emission tip 112 may be composed of a tungsten tip with a sharp tip. The configuration including the field emission tip 112 and the anode 114 corresponds to an electron gun and may further include other components to emit and accelerate the electron beam. Details of the configuration of the electron gun will be described later with reference to FIG. 2.

The focusing lenses 116 and 118 are formed of cylindrical electromagnets in which coils are wound, and serve to collect electrons into one place by using the property of the electrons being bent by a magnetic field. This electron beam forms a focal point on the specimen 130 through the objective lens 124. The electron beam 10 is scanned left and right and up and down using the scanning coil 122.

When the charged particles forming the electron beam 10 impinge on the surface of the specimen 130, secondary electrons are generated from the surface of the specimen 130. Since secondary electrons are emitted from the surface portion of the specimen 130, the secondary electrons provide information about the shape of the surface. Some of the electrons collided with the specimen 130 at high speed may be reflected or bounced off the surface. Back-scattered electrons are used for component analysis of the sample.

Detector 140 may include a scintillator (not shown) and a light guide (not shown). A scintillator refers to a device (or substance) that emits light when it is bombarded by electrons. When secondary electrons strike a fluorescently coated scintillator, the secondary electrons excite the fluorescent material and emit light, which travels along a light guide, which may be composed of lucite or quartz. do.

The photomultiplier 150 (hereinafter referred to as PMT) converts the light reached along the light guide into electrical pulses. Although not shown, the output voltage of the PMT 150 may be amplified and converted into a digital signal, and image processing may be performed to provide an image of the scan area of the specimen 130. Since the secondary electrons eventually pass through a medium called an optoelectronic device, the secondary electrons appear brighter when the emission amount is large and darker when the secondary electrons are large, and thus an image of the contrast of the specimen 130 may be obtained.

The getter pump 160 utilizes the chemisorption properties of reactive gas guns, such as oxygen, hydrogen, water and carbon oxides, to devices fabricated by non-evaporable getter materials, thereby evacuating the vacuum chamber 110. It can be configured to make a high vacuum state, for example about 10 ^-10 torr. Non-evaporable getter materials may include titanium or zirconium-based alloys. The getter pump 160 is sintered in the form of a porous powder, and generally a heating material such as molybdenum (Mo) or tungsten (W) is wound therein.

The getter pump 160 includes a heater (not shown) for activating the non-evaporable getter material and for heating the getter material to an effective temperature for controlling the adsorptive properties of the getter material. The heater may be made of, for example, a material such as molybdenum (Mo) or tungsten (W) wound therein. A driving voltage is applied to heat the heater included in the getter pump 160. The getter pump 160 shown in FIG. 1 represents a cross section of a discotic getter pump with a central axis parallel to the path of the electron beam 10 and with an empty center.

The ion pump 170 may be installed on the upper portion of the vacuum chamber 110 to maintain high vacuum. Although one ion pump 170 is shown in FIG. 1 for simplicity of the drawing, a plurality of ion pumps are typically used, and ancillary for the ion pump 170 such as a support for supporting the plurality of ion pumps is shown. Components are additionally installed in the field emission scanning electron microscope. The getter pump 160 may be used to reduce the number of ion pumps 170 used or to replace the ion pumps 170.

The power supply 200 is connected to the electron guns 112 and 114 to supply the high voltage to accelerate the electron beam 10. The high voltage can be, for example, a voltage of -1 kV to -30 kV. In addition, the power supply unit 200 may be configured to supply power to the getter pump 160, in particular, the heater included in the getter pump 160.

Although not shown for clarity, the power supply unit may also be used for the focusing lenses 116 and 118, the scan coil 122, the specimen holder for moving the specimen 130, the detector 140, and the PMT 150. Power supply means such as 200 is connected. In addition, although not shown in FIG. 1, the field emission scanning electron microscope 100 may further include various electronic circuits and components such as a circuit for controlling a vacuum, a scanning circuit, and an image signal processing circuit.

Reference numeral 300 denotes the superstructure and power supply unit 300 of the electron microscope of FIG. 1, and the structure and operation of the superstructure and power supply unit 300 of the electron microscope will be described in detail.

FIG. 2 is a diagram illustrating a detailed structure of an upper structure and a power supply unit 300 of the electron microscope included in FIG. 1 according to an embodiment.

In FIG. 2, a configuration including an emitter 102, a suppressor electrode 104, a primary anode 106, and a secondary anode 114 corresponds to the electron gun.

Emitter 102 emits electrons. Emitter 102 may be comprised of tungsten filaments. When emitter 102 is heated, electrons are released out of the tungsten surface due to thermal ionization and field emission effects. The pointed portion at which electrons are emitted from emitter 102 corresponds to field emission tip 112 of FIG. 1.

The suppressor electrode 104 is used to focus and control the emitted electrons so that the beam due to the emitted electrons has a small radius. The suppressor electrode 104 is located between the emitter 102 and the primary anode 106. The suppressor electrode 104 is also referred to as a Wehnlelt cylinder or grid cap. The suppressor electrode 104 is applied with a slightly lower bias voltage, for example, about 300V, compared to the emitter 102 to concentrate the emitted electrons in a narrow range. The suppressor electrode 104 has a hole in the center of the lower portion, as shown in FIG. 2, so that the electrons emitted from the emitter 102 are accelerated toward the primary anode 106.

The primary anode 106 is energized with a high emission power source to emit electrons from the emitter. For example, the primary anode 106 may be configured such that a high voltage of 3 to 5 kV is applied as a reference potential by using the high voltage power of the beam acceleration power supply 210 to emit electrons to the field emission tip 112.

The secondary anode 114 corresponding to the anode 114 of FIG. 1 is applied with the accelerated high voltage power of the beam acceleration power supply 210 so that the emitted electrons are accelerated. The secondary anode 114 may be configured to apply a high voltage of up to 30 kV between the secondary anode and the field emission tip 112 so that the emitted electrons are accelerated.

The configuration including the emitter 102, the suppressor electrode 104, the primary anode 106 and the secondary anode 114 is for explaining an example of the electron gun, and is not limited thereto. An electron gun according to various modified configurations may be used.

The power supply unit 200 of FIG. 1 includes a beam accerlation power supply 210, an electron extraction power supply 220, a suppressor power supply 230, The emitter heating power supply 240 may include an emitter heating power supply 240 and a getter pump power supply 250.

The beam acceleration power supply 210 supplies a high voltage power to the electron guns 112 and 114 for emitting and accelerating the electron beams to the electron guns. The negative electrode of the beam acceleration power supply 210 is connected to the electron emission power supply 220, the suppressor power supply 230, the emitter heating power supply 240, and the getter pump power supply 250. The positive electrode of the beam acceleration power supply 210 is connected to a secondary anode 114 that accelerates the electron beam 10. For example, an emission voltage of 3 to 5 kV is applied between the emitter 102 and the primary electrode 106, and an acceleration voltage of -30 kV is applied between the emitter 102 and the secondary electrode 114. Can be.

The electron emission power supply unit 220 applies the emission high voltage power lower than the high voltage supplied to the secondary anode 114 to the primary anode 106 using the high voltage power of the beam acceleration power supply 210 as the reference potential.

The suppressor power supply 230 may supply an operating power of, for example, -300 V to the suppressor electrode 104 using the high voltage power of the beam acceleration power supply 210 as a reference potential.

The emitter heating power supply 240 supplies power for heating the emitter 102 using the high voltage power of the beam acceleration power supply 210 as a reference potential.

The driving power of the getter pump 160 is extremely low compared to the high voltage power of the beam acceleration power supply 210. In addition, the getter pump 160 is installed inside the vacuum chamber 110 and is installed close to the high voltage power supplied from the beam acceleration power supply 210. Therefore, when driving power close to the ground potential is supplied to the getter pump 160 as compared with the high voltage power of the beam acceleration power supply 210 applied to the emitter 102 and the anode 114, spark discharge may occur. .

In order to prevent the occurrence of such spark discharge, the getter pump power supply unit 250 supplies driving power for heating the heater of the getter pump 160 using the high voltage power of the beam acceleration power supply unit 210 as a reference potential. For example, the getter pump power supply 250 may supply the getter pump 160 with a supply potential lowered by a potential difference for driving the getter pump 160 at a reference potential corresponding to the high voltage power.

The getter pump power supply 250 supplies a driving power set such that spark discharge does not occur between the potential of the power supplied to the getter pump 160 and the potential of the high voltage power applied to the beam acceleration power supply 210.

The getter pump 160 is installed inside the vacuum chamber 110, and is operated by heating a getter material heated using the driving power of the getter pump power supply 250. The getter pump 160 may be positioned above the secondary anode 114, particularly for ultra-high vacuum at the top of the vacuum chamber 110 of the field emission scanning electron microscope 100 that includes the electron gun.

In this way, since the getter pump 160 may be safely installed so that spark discharge does not occur in the vacuum chamber 110, the vacuum chamber 110 may quickly reach a high vacuum state. In addition, even when the field emission scanning electron microscope 100 in which the electron beam 10 is generated in the electron guns 102, 104, 106, 112, and 114 is operated, the getter pump 160 can be safely operated.

In addition, such a configuration reduces the volume of the field emission scanning electron microscope 100 by installing and using a getter pump 160 in the vacuum chamber 110 instead of a plurality of ion pumps conventionally used for high vacuum. Can be. Therefore, compared with the case of using the ion pump spaced apart in the vacuum chamber conventionally, it is possible to reach the high vacuum state required by an electron microscope quickly.

In the above description, the electron gun 100 using the electron guns 102, 104, 106, 112, 114, the getter pump 160, and the power supply unit 200 has been described, but the electron guns 102, 104, 106, 112, 114, the getter pump 160 and the power supply 200 can be modified to be used in other electron beam acceleration devices that accelerate the electron beam in a vacuum.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be construed to include various embodiments within the scope of the claims.

Claims (6)

An ultra-high vacuum generator of an electron beam acceleration device for a field emission scanning electron microscope including a vacuum chamber,
An electron gun that emits and accelerates an electron beam included in the vacuum chamber;
A beam acceleration power supply for supplying a high voltage power for emitting and accelerating the electron beam to the electron gun;
A getter pump power supply for generating and supplying a driving power dropped by a driving voltage for heating the heater of the getter pump, using the high voltage power of the beam acceleration power supply as a reference potential; And
And a getter pump installed inside the vacuum chamber and configured to heat the heater using a driving power supply of the getter pump power supply and to operate the vacuum chamber in a high vacuum state. The method of claim 1,
And the getter pump power supply is configured to supply the drive power, so that spark discharge does not occur between the potential of the drive power supplied to the getter pump and the potential of the high voltage power. The method of claim 1,
The electron gun,
Emitters that emit electrons;
A suppressor electrode for focusing the emitted electrons;
A primary anode to which emission high voltage power is applied to emit electrons from the emitter;
And a secondary anode to which a high voltage power of the beam acceleration power supply unit is applied to accelerate the emitted electrons. The method of claim 3,
An emitter heating supply unit configured to supply power for heating the emitter using the high voltage power of the beam acceleration power supply unit as a reference potential;
A suppressor power supply unit supplying operation power of the suppressor electrode using the high voltage power of the beam acceleration power supply unit as a reference potential; And
And an electron emission power supply unit configured to apply the emission high voltage power to the primary anode using the high voltage power of the beam acceleration power supply unit as a reference potential. The method of claim 3,
The getter pump, ultra-high vacuum generating device is installed to be located above the secondary anode. As a field emission scanning electron microscope,
An electron gun that emits and accelerates an electron beam;
A beam acceleration power supply for supplying a high voltage power for emitting and accelerating the electron beam to the electron gun;
A getter pump power supply for supplying driving power for heating a heater of the getter pump using the high voltage power of the beam acceleration power supply as a reference potential; And
And a getter pump installed inside the vacuum chamber, the getter pump heating the heater using a driving power supply of the getter pump power supply and operating the vacuum chamber to a high vacuum state.

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