Charged particle beam device and electron gun

Abstract

This charged particle beam device comprises: a charged particle source 202 composed of a single crystal needle 204, a filament 205 connected to the single crystal needle, and an insulator 207 that holds the filament; a plurality of non-evaporation getter materials 201; a lead-out electrode 203; and a housing 209 disposed so as to surround the axis of an electron beam emitted by the charged particle source, the charged particle beam device being characterized in that a heater 212 for heating the plurality of non-evaporation getter materials is disposed in the lead-out electrode, the plurality of non-evaporation getter materials in the housing are disposed side by side, the housing is connected to the lead-out electrode, and elastic members 250 configured to press the non-evaporation getter materials are disposed between the non-evaporation getter materials and the housing.

Description

Charged particle beam equipment and electron guns

[0001] The present invention relates to a charged particle beam device.

[0002] A charged particle beam device generates an observation image of a sample by irradiating the sample with a charged particle beam, such as an electron beam, and detecting secondary electrons, transmitted electrons, backscattered electrons, and X-rays emitted from the sample. Obtaining an observation image with high spatial resolution requires a high-brightness electron source (charged particle source), such as a cold field emission (CFE) electron source. A CFE electron source emits an electron beam (charged particle beam) by concentrating an electric field at the tip of a sharpened single crystal (tip). If residual gas in a vacuum is adsorbed to the tip, the emitted current becomes unstable. For this reason, it is necessary to reduce the pressure around the electron source (charged particle source) (increase the degree of vacuum).

[0003] An electron source (charged particle source) is mounted in an electron gun (vacuum vessel) with the inside evacuated. One way to lower the pressure inside the vacuum vessel is to mount a non-evaporable getter (NEG) material. Unlike conventional evaporative getters, NEG material does not evaporate and maintains its original shape even when heated (activated) in a vacuum. Once activated, the NEG material begins to adsorb and occlude gases, providing a vacuum pumping effect when returned to room temperature. Patent Document 1 discloses an electron gun column equipped with a sheet coated with an NEG alloy.

[0004] Japanese Patent Application Laid-Open No. 2007-157682

[0005] However, Patent Document 1 provides insufficient consideration for the method of fixing the NEG material. NEG material is a storage-type vacuum pump, and when its surface is covered with gas, it loses pumping speed. Therefore, repeated activation is required to diffuse the adsorbed gas into the material, clean the surface, and restore pumping speed. As a result of the inventors' research, they found that the thickness of the deposited NEG material is on the order of micrometers, so the capacity for diffusing adsorbed gas into the material is small, and that after multiple activations, the material reaches the end of its life and the pumping speed cannot be restored. As a result, it was not possible to maintain a stabilized current in the charged particle beam device for a long period of time.

[0006] As a result of research by other inventors, it was found that bulk NEG materials with a thickness of more than a millimeter have a large capacity for diffusing adsorbed gases inside, and that they do not reach the end of their life even after being activated several dozen times. By using bulk NEG materials, a stable current can be maintained for a long period of time.

[0007] One issue with using bulk NEG material is that it must be fixed in direct contact with other components. Because the thermal expansion coefficients of the bulk NEG material and the other components differ, stress is applied to the NEG material due to the difference in expansion during activation. As a result, cracks form in the NEG material, causing it to break, with fragments of the material scattering into the surrounding area as foreign matter. These foreign matters cause discharge and damage the electron source.

[0008] Therefore, the present invention aims to provide a charged particle beam device that stabilizes the emission current by placing a bulk NEG material around the electron source and maintains a stable emission current for a long period of time by reducing damage to the NEG material.

[0009] A charged particle beam device comprising: a charged particle source consisting of a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament; a plurality of non-evaporable getter materials; a housing arranged to surround the axis of an electron beam emitted by the charged particle source; and an extraction electrode having the housing, wherein a heater for heating the plurality of non-evaporable getter materials is arranged on the extraction electrode; the plurality of non-evaporable getter materials are arranged side by side within the housing; and an elastic member configured to press the non-evaporable getter materials is arranged between the non-evaporable getter materials and the housing.

[0010] According to the present invention, it is possible to provide a charged particle beam device that stabilizes the emission current and maintains the stability for a long period of time.

[0011] FIG. 1 is a schematic cross-sectional view showing an example of the overall configuration of a scanning electron microscope, which is an example of a charged particle beam device. FIG. 2 is a schematic cross-sectional view showing an example of a configuration of a CFE electron source and its periphery according to Example 1. FIG. 3 is a schematic perspective view showing an example of a method for arranging and fixing NEG material according to Example 1. FIG. 4 is a schematic cross-sectional view showing an example of the function of a coil spring according to Example 1 to prevent defects during activation of NEG material. FIG. 5 is a schematic perspective view showing an example of a method for arranging and fixing NEG material according to Example 2. FIG. 6 is a schematic perspective view showing an example of a method for arranging and fixing NEG material according to Example 3. FIG. 7 is a schematic perspective view showing an example of a method for arranging and fixing NEG material according to Example 4. FIG. 8 is a schematic perspective view showing an example of a method for arranging and fixing NEG material according to Example 5.

[0012] Hereinafter, an embodiment of a charged particle beam device according to the present invention will be described with reference to the accompanying drawings. The charged particle beam device is a device that irradiates a sample with a charged particle beam such as an electron beam, detects secondary electrons, transmitted electrons, reflected electrons, X-rays, and the like emitted from the sample, and generates an observation image of the sample.

[0013] The overall configuration of a scanning electron microscope, an example of a charged particle beam device, will be described using FIG. 1 . The scanning electron microscope irradiates a sample 102 with an electron beam 101 and detects secondary electrons and backscattered electrons emitted from the sample 102 to obtain an observation image of the sample 102. It includes a microscope body 103 and a sample chamber 104, which maintain a vacuum inside. The microscope body 103 is connected to ground potential. The interior of the microscope body 103 is divided into a first vacuum chamber 105, a second vacuum chamber 106, a third vacuum chamber 107, and a fourth vacuum chamber 108, from top to bottom. A diaphragm through which the electron beam 101 passes is disposed at the center of the electrodes separating the vacuum chambers, and each vacuum chamber is differentially evacuated. The pressures in the first vacuum chamber 105, the second vacuum chamber 106, the third vacuum chamber 107, and the fourth vacuum chamber 108 are higher in the lower vacuum chambers (vacuum chambers closer to the sample chamber 104). The first vacuum chamber 105, the second vacuum chamber 106, the third vacuum chamber 107, the fourth vacuum chamber 108 and the sample chamber 104 will be described below.

[0014] The first vacuum chamber 105 is the space inside the extraction electrode 203, and is evacuated by the bulk NEG material 201. The pressure in the first vacuum chamber 105 is lower than the pressures in the second vacuum chamber 106, the third vacuum chamber 107, and the fourth vacuum chamber 108, and is 1×10 －９ Pa to 1 x 10 －１０The first vacuum chamber 105 is evacuated to an extremely high vacuum region of the order of Pa or less. A CFE electron source 202 is disposed in the first vacuum chamber 105, and an extraction electrode 203 is disposed so as to surround the CFE electron source 202.

[0015] An acceleration power supply 114 is connected to two pins of the CFE electron source 202 via a flashing power supply 110, and a negative acceleration voltage of approximately −1 kV to −100 kV with respect to the ground potential supplied by the acceleration power supply 114 is normally applied to the CFE electron source 202. A suppressor power supply 124 is connected to the suppressor of the CFE electron source 202, and a suppressor voltage of approximately +1 kV to −1 kV with respect to the acceleration voltage is applied to the suppressor. The extraction electrode 203 has a cup shape and separates the first vacuum chamber 105 and the second vacuum chamber 106. An extraction power supply 109 is connected to the extraction electrode 203, and a positive extraction voltage of up to approximately +6 kV with respect to the acceleration voltage applied to the two pins of the CFE electron source 202 is applied to the extraction electrode 203. When the extraction voltage is applied to the extraction electrode 203, an electron beam 101 is emitted from the CFE electron source 202.

[0016] During flashing of the CFE electron source 202, a voltage equal to the negative acceleration voltage plus several volts is applied to one of the two pins by the flashing power supply 110, creating a potential difference of several volts between the two pins, and a pulse current is applied to the filament, heating it to approximately 2000°C (flashing). This flashing operation removes residual gas adsorbed to the CFE electron source 202 and resets the unstable time variation of the emission current. The first vacuum chamber 105 and the second vacuum chamber 106 are differentially evacuated, resulting in a difference of several orders of magnitude in pressure between them. Details of the CFE electron source 202 and its peripheral configuration will be described later using FIG. 2.

[0017] The second vacuum chamber 106 is a space outside the extraction electrode 203, surrounded by the electron gun vacuum vessel 121 and the acceleration electrode 113, and is connected to a pipe 120. At the end of the pipe 120 are an ion pump 111 and an auxiliary NEG pump 112, which evacuate the second vacuum chamber 106. The pressure in the second vacuum chamber 106 is 1×10 －７ Pa to 1 x 10 －９The second vacuum chamber 106 is an ultra-high vacuum region of approximately Pa. An acceleration electrode 113 is disposed in the second vacuum chamber 106 and is isolated from the third vacuum chamber 107. The acceleration electrode 113 and the electron gun vacuum vessel 121 are connected to ground potential. The electron beam 101 is accelerated to a predetermined speed according to the acceleration voltage. An electrostatic lens is formed in the space where the extraction electrode 203 and the acceleration electrode 113 face each other. The extraction electrode 203 and the acceleration electrode 113 have a Butler lens structure that reduces aberration of the electrostatic lens. The structure above the acceleration electrode 113 is collectively referred to as the electron gun 122. A baking heater 130 is disposed in the atmosphere outside the electron gun 122. The second vacuum chamber 106 is created into an ultra-high vacuum by evacuating the electron gun 122 with the ion pump 111 and the auxiliary NEG pump 112 while heating (baking) the entire electron gun 122 to approximately 200°C with the baking heater 130.

[0018] The third vacuum chamber 107 is evacuated by an ion pump 115. A condenser lens 116 is disposed in the third vacuum chamber 107. The condenser lens 116 focuses the electron beam 101 and adjusts the amount of current and the like.

[0019] A detector 117 is disposed in the fourth vacuum chamber 108. The detector 117 detects secondary electrons, backscattered electrons, and the like emitted from the sample 102. A plurality of detectors 117 may be provided, and may be disposed in the sample chamber 104, the first vacuum chamber 105, the second vacuum chamber 106, or the third vacuum chamber 107.

[0020] The sample chamber 104 is evacuated to a vacuum by a turbo molecular pump 118. An objective lens 119 and a sample 102 are placed in the sample chamber 104. The electron beam 101 is focused by the objective lens 119 and irradiated onto the sample 102.

[0021] An example of the CFE electron source 202 and its peripheral configuration will be described using FIG. 2 . The CFE electron source 202 is composed of a tip 204, a filament 205, two pins 206, an insulator 207, and a suppressor 123. The tip 204 is a tungsten single crystal needle with a sharpened tip and a <310> or <111> orientation, and the radius of curvature of the tip is approximately 100 nm. The tip 204 is welded to the tip of the filament 205. The filament 205 is a tungsten polycrystalline wire shaped like a V-shaped hairpin. Pins 206 are welded to both ends of the filament 205. The two pins 206 are metal terminals and are electrically insulated from each other by being held by the insulator 207. The suppressor 123 is attached to the outside of the insulator 207 by fitting, and contains the insulator 207, the pin 206, the filament 205, and a portion of the tip 204. The suppressor 123 has an opening at the bottom, from which the tip of the tip 204 protrudes. The protruding length is approximately 0.1 mm to 3 mm.

[0022] The holder 208 is a metal cylinder that fixes the suppressor 123 to hold the entire CFE electron source 202. The holder 208 is connected to the electron gun vacuum vessel 121 via an insulator 252 and is electrically insulated from the electron gun vacuum vessel 121 and the pin 206. The tip 204, filament 205, and pin 206 are at the same potential, and a negative acceleration voltage supplied from the acceleration power supply 114 is applied to the holder 208 and the suppressor 123 by the suppressor power supply 124. During flashing, the filament 205 is heated by electrical current supplied by the flashing power supply 110, thereby flashing and removing residual gas adsorbed to the tip 204. The CFE electron source 202 does not necessarily have to include the suppressor 123, and can emit electron beams even without the suppressor 123.

[0023] The extraction electrode 203 includes a metallic extraction electrode lower portion 211, an extraction electrode sidewall 210, an aperture 214, a housing 209, a coil spring 250, a load distribution plate 251, and an NEG material 201. Components other than the NEG material 201 are primarily made of materials such as stainless steel, titanium, and permalloy. The extraction electrode lower portion 211 is disposed facing the front end of the tip 204 and closest to it, with the two separated by approximately 0.3 mm to 10 mm in the vertical direction. A housing 209 is connected to the extraction electrode lower portion 211. The NEG material 201 is disposed inside the housing 209. When an extraction voltage is applied to the extraction electrode 203, the components of the extraction electrode 203 also receive the extraction voltage and are at the same potential. The extraction electrode sidewall 210 and the electron gun vacuum vessel 121 are connected via an insulator 252, electrically insulating them from each other. A differential pumping port 213 that connects the first vacuum chamber 105 and the second vacuum chamber 106 may be provided on the extraction electrode side wall 210. The conductance of the differential pumping port 213 is set small to create a pressure difference of several orders of magnitude between the first vacuum chamber 105 and the second vacuum chamber 106.

[0024] The heater 212 is disposed in the second vacuum chamber 106 and connected to the side of the extraction electrode sidewall 210. By heating the heater 212 to 400°C or higher, more preferably 500°C or higher, the heat is transferred to the housing 209 via the extraction electrode sidewall 210, further heating and activating the NEG material 201 inside. Connecting the heater 212 to the extraction electrode 203 shortens the thermal conduction path from the housing 209 of the extraction electrode 203 to the NEG material 201, thereby efficiently raising the temperature of the NEG material 201 and activating it. The heater 212 is a ceramic heater made of alumina, silicon nitride, boron nitride, aluminum nitride, or the like. Ceramic heaters may constantly release gas, worsening the pressure. Therefore, by disposing the heater 212 on the second vacuum chamber 106 side, the pressure in the first vacuum chamber 105 is prevented from deteriorating and the pressure in the first vacuum chamber 105 is reduced.

[0025] The housing 209 is composed of a lid 253 and a container 254, and the lid 253 and the container 254 are fixed together with bolts or screws (not shown). The housing 209 is arranged to surround the tip 204 or the axis of the electron beam 101 emitted from the tip 204. NEG material 201 is stored inside the housing 209. The number of NEG materials 201 arranged is increased as much as possible within the limited volume of the housing 209. The NEG materials 201 are arranged in a circumferential manner with high density so as to surround the axis of the electron beam 101. The NEG materials 201 may be arranged in two or more rows in the height direction. Arranging the NEG materials 201 in two or more rows in the height direction can further improve the exhaust speed. Furthermore, the NEG materials 201 may be arranged in multiple rows in the radial direction. The housing 209 not only functions as a storage container for the NEG material 201 but also as a heat conduction path, and when the heater 212 is heated, heat is uniformly transferred to the NEG materials 201 to activate them. The housing 209 has an opening 216 only on the first vacuum chamber 105 side, and the first vacuum chamber 105 is evacuated to an extremely high vacuum by the NEG material 201. The housing 209 also functions as a partition wall separating the first vacuum chamber 105 from the second vacuum chamber 106. The first vacuum chamber 105 is evacuated by the NEG material 201, and the second vacuum chamber 106 is evacuated by the ion pump 111 and the auxiliary NEG pump 112, thereby forming a differential pumping structure between the first vacuum chamber 105 and the second vacuum chamber 106. The pressure in the first vacuum chamber 105 is lower than the pressure in the second vacuum chamber 106, and even if the pressure in the second vacuum chamber 106 increases due to discharge or electron impact desorption, the pressure in the first vacuum chamber 105 is kept low due to the effect of differential pumping. As a result, the amount of gas adsorbed to the tip 204 is reduced, reducing current attenuation and noise in the electron beam 101 and maintaining a stable electron beam.

[0026] The NEG material 201 is an alloy of zirconium, vanadium, and iron. The NEG material 201 is an individually formed bulk material having a thickness of 1 mm or more. Having a thickness of 1 mm or more increases the capacity for diffusing adsorbed gases inside, thereby extending the life of the NEG material 201. The NEG material 201 may be, for example, cylindrical, with a thickness, diameter, and height of approximately 1 mm to 100 mm. Using a bulk material having a thickness on the order of millimeters for the NEG material 201 increases the capacity for diffusing adsorbed gases inside, allowing for activation several tens of times or more, thereby extending the life of the charged particle beam device. The more NEG materials 201 are placed in the housing 209, the faster the pumping speed and the lower the pressure in the first vacuum chamber 105. Because the NEG material adsorbs gases onto its surface to evacuate, increasing the area of ​​the NEG material 201 exposed to the first vacuum chamber 105 improves the pumping speed. If a porous body made by sintering zirconium-vanadium-iron alloy powder is used as the NEG material 201, the surface will have micrometer-order irregularities, increasing the effective surface area and further improving the pumping speed. The shape of the NEG material 201 is not limited to a cylinder, and it may be a block or ring. Other materials may be used for the NEG material 201, and the temperature required for activation may be reduced to approximately 100°C depending on the type of material. If the activation temperature is low, the NEG material 201 can be activated by thirdly heating the entire electron gun 122 using the baking heater 130 located outside the electron gun 122. As a result, the heater 212 located in the second vacuum chamber 106 may be omitted.

[0027] A sheet of NEG material can also be used as the NEG material 201. However, because the thickness of the NEG material is on the order of micrometers, its capacity for diffusing adsorbed gases into the interior is small, and its lifespan expires after a few activations. Furthermore, when using a sheet as the NEG material 201, the sheet must be folded to increase the surface area of ​​the sheet mounted within the housing in order to achieve sufficient pumping speed. However, the NEG material film peels off at the folded portion, creating a large amount of foreign matter. This foreign matter causes discharge due to the voltage difference between the suppressor and the extraction electrode, damaging the chip 204. Furthermore, the composition distribution of NEG filmed on a sheet varies depending on the film formation conditions, resulting in variations in pumping speed for each sheet. This results in differences in the pressure in the first vacuum chamber 105 for each device, leading to differences in current stability between devices. On the other hand, bulk NEG material exhibits small individual variations, allowing the pumping speed to be controlled by the number of pieces placed. This makes it less likely that differences in the pressure in the first vacuum chamber 105 will occur between devices. From the above, by using individually formed bulk material as the NEG material 201, a sufficient lifespan and reduction in the difference between foreign matter and the aircraft body can be achieved.

[0028] Next, the procedure for emitting the electron beam 101 will be described. When an extraction voltage is applied to the extraction electrode 203, a strong electric field is applied to the tip of the tip 204, and the electron beam 101 is emitted by field emission. Changing the suppressor voltage changes the electric field at the tip of the tip 204, thereby adjusting the amount of emission current. An aperture 214 is located at the center of the lower extraction electrode 211. The aperture 214 has a hole diameter of typically 1 mm or less, more preferably 0.5 mm or less. The electron beam 101 passes through the hole in the aperture 214 and travels to the second vacuum chamber 106, where it expands conically before reaching the acceleration electrode 113. An aperture 215 is located at the center of the acceleration electrode 113. The outer periphery of the electron beam 101 is blocked by the aperture 215 and the acceleration electrode 113, while the central portion travels to the third vacuum chamber 107. This electron beam continues downward and is ultimately irradiated onto the sample 102.

[0029] Next, the operation of efficiently evacuating the first vacuum chamber 105 to an extremely high vacuum will be described. The effective pumping speed of the ion pump 111 and the auxiliary NEG pump 112 is determined by the conductance of the pumping path of the piping 120, and the efficiency of evacuating the area around the electron source (charged particle source) is low. On the other hand, the NEG material 201 is disposed inside the extraction electrode 203 and in close proximity to the electron source (charged particle source), and therefore has a large conductance and a high effective pumping speed. As a result, the area around the electron source (charged particle source) is efficiently evacuated.

[0030] By placing multiple NEG materials 201 inside the housing 209 in advance and mounting this on the electron gun, the time required for assembly can be reduced compared to mounting the NEG materials 201 individually on the electron gun. Also, there is less chance of the NEG materials 201 colliding with electron gun components during assembly, resulting in the generation of foreign matter. Furthermore, when the NEG materials 201 reach the end of their life after many years of use, all of the NEG materials 201 can be easily replaced with new ones simply by replacing the housing during maintenance of the charged particle beam device, and the exhaust speed can be restored.

[0031] The housing 209 is arranged to surround the tip 204 or the axis of the traveling direction of the electron beam 101. In this configuration, the distance of the exhaust path between the NEG material 201 and the tip 204 is shortened, which increases conductance and improves the effective exhaust speed. By arranging the housing 209 at the same height as the tip 204, the distance can be minimized and conductance can be maximized. On the other hand, the housing 209 may be arranged at a different height from the tip 204. For example, when the housing 209 is made large in the height direction and a large amount of NEG material 201 is mounted inside, the housing 209 may be arranged at a higher position than the tip 204 due to space constraints. Even in this case, by arranging the housing 209 to surround the axis of the electron beam 101, the distance of the exhaust path from the tip 204 to any of the NEG materials 201 can be minimized and conductance can be improved.

[0032] The first vacuum chamber 105 is a limited, narrow space that exists only inside the extraction electrode 203, and contains a small number of components, resulting in a small total amount of outgassing. Furthermore, the entire extraction electrode 203 is heated to a high temperature once by the heater 212, which removes molten hydrogen from inside the components and reduces the amount of outgassing per component. The combined effects of improving the effective pumping speed and reducing the amount of outgassing achieved by placing the NEG material 201 inside the extraction electrode 203 described above allow the pressure in the first vacuum chamber 105 to be efficiently reduced to an extremely high vacuum, and a stable emission current is provided from the CFE electron source 202.

[0033] The arrangement and fixing method of the NEG material 201 will be described using FIG. 3 . FIG. 3 is a perspective view of a portion of the housing 209. Note that FIG. 3 uses a cylindrical coordinate system, with the height direction represented as Z, the circumferential direction represented as θ, and the radial direction represented as R. The NEG material 201 is arranged inside the housing container 254, and a housing lid 253 is placed on top. The NEG material 201 may be arranged regularly in the circumferential direction (θ direction), and the NEG materials 201 may be arranged in contact with each other. This allows a large number of NEG materials 201 to be arranged within the limited volume of the housing 209, improving the exhaust speed and reducing the pressure in the first vacuum chamber 105. The NEG material 201 is arranged in two tiers in the height direction (Z direction), increasing the number of materials arranged within the housing 209. Note that the number of tiers may be more than two. A load distribution plate 251-A may be arranged between the lower tier NEG material 201-A and the upper tier NEG material 201-B. A load distribution plate 251-B and a coil spring 250-A are arranged between the upper NEG material 201-B and the lid 253. The coil springs 250-A are arranged between the load distribution plate 251-B and the lid 253, and it is preferable that there are a plurality of coil springs 250-A. The container 254 is provided with a partition wall 303, and the container 254 and the partition wall 303 are formed integrally. A load distribution plate 251-C is arranged between the end NEG material 201-C and NEG material 201-D and the partition wall 303. A coil spring 250-B may be arranged between the partition wall 303 and the load distribution plate 251-C.

[0034] The load distribution plate 251-A preferably comes into contact with a plurality of NEG materials 201. The number of contacts is at least two NEG materials at different circumferential positions and two NEG materials at different height positions, for a total of at least three different NEG materials. The load distribution plate 251-B also comes into contact with a plurality of NEG materials, and at least two NEG materials at different circumferential positions. The load distribution plate 251-C also comes into contact with a plurality of NEG materials, and at least two NEG materials at different height positions.

[0035] The coil spring 250 is a spring made of wound metal wire and is made of a material that maintains its elasticity even when heated during activation. The length of the coil spring 250 expands and contracts from its natural length, pressing against the component that it comes into contact with in the direction of expansion and contraction, and maintaining the applied force.

[0036] When the lid 253 is placed on the container 254, the coil spring 250-A is pressed by the lid 253 and contracts, applying a force in the height direction to the load distribution plate 251-B. The load distribution plate 251-B distributes and transmits the force of the coil spring 250-A to the multiple NEG materials 201-B that are in contact below. The NEG materials 201-B are fixed in position by being pressed. The multiple NEG materials 201-B transmit the pressed force further downward to the load distribution plate 251-A. The load distribution plate 251-A distributes the applied force and transmits it to the multiple NEG materials 201-A that are in contact below, pressing them to fix them. In this way, the entire NEG material 201 is fixed by the coil spring 250-A, reducing positional changes of the NEG material 201, particularly changes in position in the height direction. By reducing positional changes, damage to the NEG material 201 can be suppressed. The coil spring 250 has elasticity and returns to its original length when the lid 253 is removed, so it can be reused as long as it maintains its elasticity.

[0037] The coil spring 250-B is arranged in a contracted state and applies a circumferential force to the load distribution plate 251-C. The load distribution plate 251-C distributes and transmits the force of the coil spring 250-B to the NEG material 201-C and NEG material 201-D that it contacts, pressing and fixing them. The NEG material 201-C and NEG material 201-D further transmit this force to the other NEG material that it contacts in the circumferential direction, pressing the entire NEG 201 in the circumferential direction. As a result, the entire NEG material 201 is fixed by the coil spring 250-B, reducing positional changes of the NEG material 201, particularly in the circumferential direction. By arranging the coil spring as described above, the NEG material 201 is pressed and fixed in the height and circumferential directions, preventing sliding, which is collision or rubbing against other parts, caused by the NEG material 201 moving from its predetermined position. Note that the coil spring 250 may be added in a direction that applies force in the radial direction. Even in this case, the entire NEG material 201 is fixed, and positional change in the radial direction is particularly reduced. By arranging multiple coil springs 250 and increasing the height, circumference, radius, and pressing direction, the NEG material 201 is more firmly fixed. The dimensions of the NEG material 201, such as the height and diameter, may not be constant, which may create a gap between the lid 253 of the housing 209 and the NEG material 201-B, causing the NEG material 201 to move. Therefore, by arranging the coil spring 250 that presses in the height direction, collisions and sliding due to movement of the NEG material 201 are prevented. Note that if the direction in which the lid 253 of the housing 209 is placed is the circumferential direction, gaps are also likely to form in the circumferential direction, so it is more preferable to arrange the coil spring 250 that presses in the circumferential direction. If the cover 253 is placed in the radial direction, gaps are likely to form in the radial direction, so it is more preferable to arrange the coil spring 250 that applies pressure in the radial direction.

[0038] An exhaust path 306 is formed in the space adjacent to the coil spring 250 in the circumferential direction. The exhaust path 306 functions as a vacuum exhaust path with large conductance, and allows the surface of the NEG material 201 arranged on the radially outer side (the side with larger R) to contribute to vacuum exhaust, thereby improving the effective exhaust speed.

[0039] The load distribution plate 251 is a metal plate with a certain width and length, and distributes stress by making surface contact with the NEG material 201. The load distribution plate 251 is used to equalize the force of the coil spring 250, and by making contact with multiple NEG materials 201, the force is equalized, preventing stress concentration and cracking of the NEG material 201. The more NEG materials 201 that the load distribution plate 251 comes into contact with, the more uniform the stress becomes, and cracking of the NEG material 201 due to stress concentration can be suppressed. Furthermore, by using the load distribution plate 251, it is possible to apply force to the entire NEG material 201 and fix it, even if the number of coil springs 250 to be mounted is reduced. In addition, by performing spherical machining or chamfering on the end surfaces of the load distribution plate 251, cracking of the NEG material 201 due to contact with the NEG material 201 can be suppressed. The load distribution plate 251 is provided with a convex positioning portion 301, which is covered with a coil spring 250. By placing the coil spring 250 in a predetermined positioning portion 301, the stress applied to the NEG material 201 is prevented from being unevenly distributed. The positioning portion 301 may be concave, or may be combined with other components.

[0040] Another effect of the load distribution plate 251 is that the surface area exposed to the first vacuum chamber 105 is increased compared to when multiple NEG materials 201 are stacked in contact with each other. The load distribution plate 251-A exposes the upper surface 304 of the NEG material 201-A to the vacuum by making its width narrower than that of the NEG material 201 it contacts. As a result, the upper surface 304 contributes to evacuation. Similarly, the load distribution plate 251-B exposes the upper surface 305 of the NEG material 201-B by making its width narrower than that of the NEG material 201 it contacts, thereby contributing to evacuation. Note that a surface exposed to the vacuum is also created on the underside of the NEG material 201-B. By placing the load distribution plate between the NEG materials 201 in this way and exposing part of the upper and lower surfaces of the NEG materials 201 to the vacuum, the evacuation speed of the NEG material 201 can be improved. Additionally, an opening 302 may be provided in the load distribution plate 251. By providing the opening 302, the surface of the NEG material 201 facing the opening 302 is exposed to the vacuum, contributing to the vacuum evacuation. As a result, the evacuation speed can be improved.

[0041] If the NEG material 201 moves from its designated location, its exposed area in the vacuum changes, potentially reducing the pumping speed. Furthermore, if the moved NEG material 201 collides with or slides against other components or other NEG materials 201, some of the material may break, generating foreign matter. In particular, if a sintered NEG material 201 is used, its surface has micrometer-order irregularities, which can easily crack and generate foreign matter. Therefore, it is necessary to hold the NEG material 201 in contact with other components and secure it to prevent movement or sliding. Using the coil spring 250, as in this embodiment, fixes the NEG material 201, reducing collisions and sliding due to movement. If stress concentrates on a corner or other part of the bulk NEG material 201, cracks may occur, resulting in breakage and the generation of large amounts of foreign matter. However, using the load distribution plate 251 prevents stress concentration. Causes of movement of the NEG material 201 include vibrations during device assembly and transportation, and earthquakes. On the other hand, even if the NEG material 201 is fixed, activation can cause problems such as cracks in the NEG material 201 and gaps in the housing 209. The effect of using the coil spring 250 to prevent these problems during activation will be described below.

[0042] Using Figure 4, we will explain how this configuration prevents problems during activation of the NEG material 201. In order to give the NEG material 201 exhaust capacity, it is necessary to activate it by heating it at 400°C or higher. Here, the NEG material 201, the load distribution plate 251, the container 254, and the lid 253 all have different thermal expansion coefficients, so problems occur when they expand during heating and their lengths change. The coil spring 250 reduces these problems during activation.

[0043] FIG. 4A is a cross-sectional view of a portion of the housing 209 without the coil spring 250. In this configuration, as an example, the NEG material 201 is arranged in three vertical tiers, and the lid 253 is placed in contact with the top-tier NEG material 201 to secure the entire NEG material 201 in place. When activation is performed with this configuration, thermal expansion can cause the total length L1 of the NEG material 201 and the load distribution plate 251 to become longer than the inner height L2 of the container 254. At this time, the lid 253 applies a downward force to the NEG material 201. If this force concentrates at a corner of the NEG material 201, a crack 401 occurs, causing part of the NEG material 201 to break and fall off. Furthermore, a large amount of granular foreign matter is generated from the crack 401, damaging the tip 204 through electrical discharge. Furthermore, if L1 becomes longer than L2, the lid 253 may be pushed up, creating a small gap 402 in the housing 209. When gap 402 is created, housing 209 no longer functions as a partition, and first vacuum chamber 105 and second vacuum chamber 106 are connected via gap 402. As a result, the pressure in the first vacuum chamber increases (deteriorates). Furthermore, since the differential pumping effect of first vacuum chamber 105 is lost, if the pressure in second vacuum chamber 106 increases due to discharge or electron shock desorption, the pressure in first vacuum chamber 105 also increases, making it impossible to stabilize the current. In addition, if the height L2 of the container becomes longer than L1 due to thermal expansion, NEG material 201 will no longer be fixed by lid 253, and movement of NEG material 201 will cause collision or sliding with other components.

[0044] 4B is a cross-sectional view of a portion of the housing 209 when using a coil spring 250. In this configuration, the NEG material 201 is arranged in two stages in the height direction, and the coil spring 250 and the load distribution plate 251 are arranged between the lid 253 and the NEG material 201. When activation is performed in this configuration, the coil spring 250 expands and contracts to change the height L3, thereby preventing malfunctions caused by thermal expansion of each component.

[0045] When L1 increases due to thermal expansion, the coil spring 250 contracts and maintains the pressure on the NEG material 201. At this time, because the coil spring 250 is an elastic body, the pressure is sufficiently smaller than the force of the lid 253, which is a rigid body shown in FIG. 4A . Furthermore, the force of the coil spring 250 is distributed throughout the NEG material 201 by the load distribution plate 251. As a result, cracks 401 are prevented from occurring in the NEG material 201. Furthermore, the contraction of the coil spring 250 prevents the position of the lid 253 from changing, and no gap 402 is generated in the housing 209. As a result, differential evacuation between the first vacuum chamber 105 and the second vacuum chamber 106 is maintained. Furthermore, even if the height L2 of the container increases due to thermal expansion, the coil spring 250 expands, so that the NEG material 201 remains fixed and pressed. As a result, collisions and sliding caused by movement of the NEG material 201 are prevented even during heating. Furthermore, even after activation is completed and the temperature returns to room temperature, the coil spring 250 returns to its original length, causing each component to return to its original position and shape, and the NEG material 201 also remains pressed and fixed. As described above, by arranging the coil spring 250 and allowing its length to expand and contract, positional changes due to thermal expansion of other components are absorbed even during heating, preventing malfunctions.

[0046] 4 has been described with respect to the effect of the coil spring 250 arranged in the height direction, but a coil spring arranged in the circumferential direction also prevents the occurrence of cracks 401 and gaps 402 in the NEG material 201 due to thermal expansion in the circumferential direction, or collisions and sliding due to movement of the NEG material 201. Alternatively, the coil spring 250 may be arranged in the radial direction (direction R), and in this case, defects due to thermal expansion in the radial direction are similarly prevented.

[0047] As described above, by fixing the NEG material 201 using the coil spring 250 in this embodiment, it is possible to reduce the decrease in pumping speed due to movement of the NEG material 201, and the generation of foreign matter due to collision or sliding with other components or other NEG materials. Furthermore, by using the coil spring 250, cracks and foreign matter generation in the NEG material 201 that occur when activating the NEG material 201, as well as the generation of gaps 402 in the housing 209, are prevented. Furthermore, by efficiently evacuating the first vacuum chamber 105 using the NEG material 201, an extremely high vacuum is achieved. Furthermore, by differentially evacuating the first vacuum chamber 105, the extremely high vacuum state of the first vacuum chamber 105 is maintained without being affected by the pressure of the second vacuum chamber 106. Furthermore, by using bulk NEG material individually formed in the NEG material 201 and having a thickness on the order of millimeters, it is possible to extend the lifespan, reduce foreign matter, and reduce differences in pumping speed between devices. As a result, a charged particle beam device with stable current over a long period of time is provided.

[0048] In the first embodiment, a configuration has been described in which the NEG material 201 is fixed using the coil spring 250. In the second embodiment, a configuration has been described in which the NEG material 201 is fixed using the coil spring 250 when the container does not have a partition wall 303. Note that some of the configurations and functions described in the first embodiment can be applied to the second embodiment, and therefore, the same reference numerals are used for similar configurations and functions, and the description thereof will be omitted.

[0049] A method for fixing the NEG material 201 in this embodiment will be described using FIG. 5. In this configuration, the container 254 does not have a partition wall 303, and the NEG material 201 is arranged continuously in the circumferential direction. In order to fix the NEG material 201 in the circumferential direction, a load distribution plate 251-C and a load distribution plate 251-D are arranged between the NEG material 201-C at one end and the opposing NEG material 201-E at the other end. A coil spring 250-B is arranged between the load distribution plate 251-C and the load distribution plate 251-D. The coil spring 250-B is arranged in a contracted state from its natural length and applies a force in the circumferential direction. This force is transmitted to the load distribution plate 251-C, and then distributed and transmitted to the NEG material 201-C and NEG material 201-D. Furthermore, this force is transmitted in sequence to the other NEG materials 201 adjacent in the circumferential direction. As a result, the entire NEG material 201 is pressed and fixed. The load distribution plate 251-C distributes and transmits the stress, preventing cracks in the NEG material 201 and the generation of foreign matter. The coil spring 250-B also applies force to the load distribution plate 251-D in the opposite circumferential direction. This force is distributed and transmitted to the NEG material 201-E and the NEG material 201-F, and then transmitted in sequence to other NEG materials 201 not shown. As a result, the entire NEG material 201 is pressed and fixed. Even in the case where there is no partition wall 303 in the circumferential direction of the container as in this embodiment, the NEG material 201 is fixed by arranging the coil spring 250 and the load distribution plate 251 between adjacent NEG materials 201, and positional changes of the NEG material 201, particularly in the circumferential direction, are reduced. As a result, movement, collision, and sliding of the NEG material 201 are prevented. Furthermore, when the NEG material 201 is activated, the coil spring 250 absorbs displacement in response to thermal expansion, thereby preventing the occurrence of cracks 401 and foreign matter, and the occurrence of gaps 402 in the housing 209. Note that, although the coil spring 250 is disposed between the NEG materials 201 adjacent in the circumferential direction in this embodiment, the same effect can be obtained by disposing the coil spring 250 and the load distribution plate 251 between the NEG materials 201 adjacent in the height direction or radial direction.

[0050] In the second embodiment, a configuration in which the coil spring 250 is used for fixing when the container does not have a partition wall 303 is described. In the third embodiment, a configuration in which the leaf spring 601 is used for fixing instead of the coil spring 250 is described. Note that some of the configurations and functions described in the first and second embodiments can be applied to the third embodiment, and therefore, the same configurations and functions are designated by the same reference numerals and will not be described again.

[0051] The method for fixing the NEG material 201 in this embodiment will be described using Figure 6. The leaf spring 601 has a structure in which a metal plate is folded. The accordion-shaped metal plate has elasticity that allows it to expand and contract when folded, and it presses against the parts it comes into contact with, maintaining the applied force. By using a metal material for the leaf spring 601, its elasticity is maintained even when it is heated during activation.

[0052] A leaf spring 601-A is placed between the NEG material 201 and the lid 253. When the lid 253 is placed on the container 254, the leaf spring 601-A is pressed by the lid 253 and contracts, applying a force in the height direction. This force is distributed and transmitted to the multiple NEG materials 201 that it comes into contact with below, and is then transmitted to the multiple NEG materials 201 in the lower row via the load distribution plate 251. As a result, the entire NEG material 201 is pressed, fixing its position and reducing positional changes, particularly in the height direction. The leaf spring 601 is elastic and returns to its original length when the lid 253 is removed. This allows it to be reused.

[0053] A leaf spring 601-B is disposed between the partition wall 303 of the container and the NEG material 201. The leaf spring 601-B is disposed in a contracted state and applies a force in the circumferential direction. This force is distributed and transmitted to the multiple NEG materials 201 that it comes into contact with, and is then transmitted to adjacent NEG materials 201 in the circumferential direction. As a result, the entire NEG material 201 is pressed and fixed, and positional changes of the NEG material 201, particularly in the circumferential direction, are reduced.

[0054] Since the leaf spring 601 has a planar structure, it can be pressed with an even stress by making surface contact. As a result, stress is prevented from concentrating on one part of the NEG material 201, causing cracks or foreign matter. Furthermore, since the leaf spring 601 can come into contact with multiple NEG materials 201, it itself has the effect of distributing force in the same way as a load distribution plate. Therefore, it is possible to omit the load distribution plate 251-B adjacent to the coil spring 250 described in the first embodiment, thereby reducing the number of parts.

[0055] Using the leaf spring 601 as in this embodiment also makes it possible to fix the NEG material 201 and prevent collisions and sliding due to movement of the NEG material 201. Furthermore, when the NEG material 201 is activated, the leaf spring 601 absorbs displacement in response to thermal expansion, thereby preventing the occurrence of cracks 401 and foreign matter, and the occurrence of gaps 402 in the housing 209.

[0056] In the third embodiment, a configuration in which the leaf spring 601 is used for fixing is described. In the fourth embodiment, a configuration in which the leaf spring 701 is disposed in the radial direction for fixing is described. Note that, since some of the configurations and functions described in the first to third embodiments can be applied to the fourth embodiment, the same reference numerals are used for the same configurations and functions, and the description thereof will be omitted.

[0057] The method of fixing the NEG material 201 in this embodiment will be described using FIG. 7 . In this configuration, the NEG material 201 is arranged in two rows in the radial direction, and the number of NEG material 201 mounted in the housing 209 is increased to improve the pumping speed. The NEG material 201-G in the first row in the radial direction and the NEG material 201-H in the second row are in contact with each other, and the NEG material 201 in the same row are also in contact with each other in the circumferential direction. As a result, a large number of NEG material 201 are mounted in the housing 209, increasing the pumping speed. The load distribution plate 251 is also widened in the radial direction, and is in contact with both the first and second rows of NEG material 201 in the radial direction, distributing and transmitting the force of the coil spring 250 to both rows. The opening 302 provided in the load distribution plate 251 is widened so that it spans the two rows of NEG material 201, increasing the surface area of ​​the NEG material 201 exposed to the first vacuum chamber 105.

[0058] A leaf spring 701 is placed between the NEG material 201 and the side wall 702 of the container. The structure of the leaf spring 701 is similar to that of the leaf spring 601 described in Example 3, and is a folded metal plate that applies force by pressing against parts it comes into contact with. Its elasticity is maintained even when heated during activation.

[0059] The leaf spring 701 is arranged in a contracted state and applies a force in the radial direction. This force is distributed and transmitted to the NEG material 201-H in the second row in the radial direction that it comes into contact with. Furthermore, this force is transmitted to the inner NEG material 201-G in the first row in the radial direction. As a result, the entire NEG material 201 is pressed and fixed, reducing positional change, particularly in the radial direction. Note that a load distribution plate may be added between the NEG material 201-G in the first row in the radial direction and the NEG material 201-H in the second row. In this case, the force pressing the NEG material 201-H in the second row is further distributed and averaged by the added load distribution plate and transmitted to the NEG material 201-G in the first row.

[0060] As in the third embodiment, the leaf spring 701 has a planar structure, and the stress is uniformed by surface contact. As a result, stress is prevented from concentrating on a part of the NEG material 201, which would otherwise cause cracks or foreign matter.

[0061] Even when the leaf spring 701 is used as in this embodiment, the NEG material 201 can be fixed, and collisions and sliding due to movement of the NEG material 201 can be prevented. Furthermore, when the NEG material 201 is activated, the leaf spring 701 absorbs displacement in response to thermal expansion, thereby preventing the occurrence of cracks 401 and foreign matter, and the occurrence of gaps 402 in the housing.

[0062] In the fourth embodiment, a configuration in which the leaf springs 701 are arranged and fixed in the radial direction is described. In the fifth embodiment, a configuration in which the shim spacers 801 are arranged and fixed is described. Note that some of the configurations and functions described in the first to fourth embodiments can be applied to the fifth embodiment, and therefore, the same configurations and functions are designated by the same reference numerals and will not be described again.

[0063] The method for fixing the NEG material 201 in this embodiment will be described with reference to Figure 8. In this configuration, the NEG material 201 is fixed using a shim spacer 801 made of metal and having elasticity. The shim spacer is preferably annealed to soften it and make it elastic. The shim spacer 801 is made of stainless steel, permalloy, titanium, titanium alloy, aluminum alloy, or copper alloy.

[0064] A shim spacer 801-A is placed between the NEG material 201 and the lid 253. The shim spacer 801-A has a plate-like structure and is thick. When the lid 253 is placed on the container 254, the shim spacer 801-A is pressed by the lid 253 and contracts slightly, applying a force in the height direction. This force is distributed and transmitted to the multiple NEG materials 201 that it comes into contact with below, and is further transmitted to the multiple NEG materials 201 in the lower row via the load distribution plate 251. As a result, the entire NEG material 201 is pressed, fixing its position and reducing positional change, particularly in the height direction. The shim spacer 801 is elastic and returns to its original length when the lid 253 is removed. This allows it to be reused.

[0065] A shim spacer 801-B is disposed between the partition wall 303 of the container and the NEG material 201. The shim spacer 801-B has a block-like structure. The shim spacer 801-B is press-fitted into the container 254 and applies a force in the circumferential direction. This force is distributed and transmitted to the multiple NEG materials 201 that it comes into contact with, and is further transmitted to the NEG materials 201 that are adjacent in the circumferential direction. As a result, the entire NEG material 201 is pressed and fixed, and positional changes of the NEG material 201, particularly in the circumferential direction, are reduced.

[0066] The shim spacer 801 has a planar structure, and by being in planar contact with the NEG material 201, it can apply pressure with uniform stress. As a result, stress is prevented from concentrating on one part of the NEG material 201, causing cracks or foreign matter. In addition, because the shim spacer 801 can come into contact with multiple NEG materials 201, it itself has the same effect as a load distribution plate. Therefore, it is possible to omit the load distribution plates 251-B and 251-C adjacent to the coil spring 250 described in the first embodiment, thereby reducing the number of parts.

[0067] Even if the shim spacer 801 is used as in this embodiment, the NEG material 201 can be fixed, and collisions and sliding due to movement of the NEG material 201 can be prevented.

[0068] A number of embodiments of the present invention have been described above. The present invention is not limited to the above embodiments, and the components can be modified within the scope of the gist of the invention. For example, the coil spring 250-A and the load distribution plate 251-B of the first embodiment may be combined with the leaf spring 601-B of the third embodiment. Furthermore, instead of the coil spring 250 and the leaf spring 601, a spiral spring, a coned disc spring, a filigree spring, a ring spring, or the like may be used. Furthermore, instead of a tungsten single crystal, a CeB ６ and LaB ６ Alternatively, a low work function material such as tungsten or a material with an inactive surface such as a carbon-coated material may be used. Alternatively, a nanowire electron source or a single-atom electron source having a sharpened tip radius of curvature of several tens of nanometers or from several atoms to one atom may be used. The charged particle source to which the present invention is applicable is not limited to a CFE electron source; it can also be applied to a Schottky electron source or an ion source. An example of an ion source is a gas field ionization ion source. By using a tungsten single crystal with a <111> crystal orientation for the tip 204 and applying a positive voltage to the tip 204 relative to the extraction electrode 203, an ion beam can be emitted as a charged particle beam from the tip 204, even if the device configuration is otherwise the same. In addition, in order to obtain a stable emission current from a Schottky electron source, a tungsten single crystal with a <111> crystal orientation and a positive voltage to the tip 204 relative to the extraction electrode 203 can be used. －７ An ultra-high vacuum of 0.1 Pa or less is required. By applying the present invention, efficient evacuation of the area around the electron source (charged particle source) can be achieved, achieving both efficient evacuation and miniaturization of the charged particle beam device. In addition, the effect of pressure rise in the second vacuum chamber is reduced, making it easier to maintain a stable emission current.

[0069] 101...electron beam, 102...sample, 103...microscope body, 104...sample chamber, 105...first vacuum chamber, 106...second vacuum chamber, 107...third vacuum chamber, 108...fourth vacuum chamber, 109...extraction power supply, 110...flushing power supply, 111...ion pump, 112...auxiliary NEG pump, 113...acceleration electrode, 114...acceleration power supply, 115...ion pump, 116...condenser lens, 117...detector, 118...turbomolecular pump, 119...objective lens, 120...piping, 121...electron gun vacuum vessel, 122...electron gun, 123...suppressor, 124...suppressor power supply, 130...baking heater, 201...NEG material, 202...CF E electron source, 203...extraction electrode, 204...tip, 205...filament, 206...pin, 207...insulator, 208...holding portion, 209...housing, 210...extraction electrode side wall, 211...extraction electrode lower portion, 212...heater, 213...differential exhaust port, 214...aperture, 215...aperture, 216...opening, 250...coil spring, 251...load distribution plate, 252...insulator, 253...lid, 254...container, 301...positioning portion, 302...opening, 303...partition wall, 304...upper surface, 305...upper surface, 306...exhaust path, 401...crack, 402...gap, 601...leaf spring, 701...leaf spring, 702...side wall, 801...shim spacer.

Claims

1. A charged particle beam device comprising: a charged particle source consisting of a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament; multiple non-evaporable getter materials; a housing arranged to surround the axis of an electron beam emitted by the charged particle source; and an extraction electrode having the housing, wherein a heater for heating the multiple non-evaporable getter materials is arranged on the extraction electrode; the multiple non-evaporable getter materials are arranged in a row within the housing; and an elastic member configured to press the non-evaporable getter materials is arranged between the non-evaporable getter materials and the housing.

2. The charged particle beam device according to claim 1, wherein the elastic member is a coil spring or a leaf spring.

3. The charged particle beam device according to claim 2, wherein the plurality of non-evaporable getter materials are individually formed bulk materials having a thickness of 1 mm or more.

4. The charged particle beam device according to claim 3, further comprising a load distribution plate in contact with said plurality of non-evaporable getter materials.

5. A charged particle beam device according to claim 4, wherein said load distribution plate is provided with an opening.

6. The charged particle beam device according to claim 3, wherein the elastic member is disposed so that the non-evaporable getter material is pressed in the height direction.

7. The charged particle beam device according to claim 3, wherein the non-evaporable getter materials are arranged in two or more stages in the height direction.

8. The charged particle beam device according to claim 3, wherein a plurality of the elastic members are arranged so that the non-evaporable getter material is pressed from two or more different directions.

9. A charged particle beam device as described in claim 3, characterized in that it comprises: a first vacuum chamber inside the extraction electrode, in which the non-evaporable getter material is disposed; and a second vacuum chamber in which the heater and the extraction electrode are disposed and which has a higher pressure than the first vacuum chamber, and the housing has an opening only on the side of the first vacuum chamber.

10. A charged particle beam device comprising: a charged particle source consisting of a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament; multiple non-evaporable getter materials; a housing arranged to surround the axis of an electron beam emitted by the charged particle source; and an extraction electrode having the housing, wherein a heater for heating the multiple non-evaporable getter materials is arranged in the extraction electrode, the multiple non-evaporable getter materials are arranged in a row within the housing, and an elastic member configured to press the non-evaporable getter materials is arranged between the non-evaporable getter materials.

11. The charged particle beam device according to claim 10, wherein the elastic member is a coil spring or a leaf spring.

12. The charged particle beam device according to claim 11, wherein the plurality of non-evaporable getter materials are individually formed bulk materials having a thickness of 1 mm or more.

13. A charged particle beam device comprising: a charged particle source consisting of a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament; multiple non-evaporable getter materials; a housing arranged to surround the axis of an electron beam emitted by the charged particle source; and an extraction electrode having the housing, wherein a heater for heating the multiple non-evaporable getter materials is arranged on the extraction electrode; the multiple non-evaporable getter materials are arranged in a row within the housing; and an elastic member configured to press the non-evaporable getter materials is arranged between the non-evaporable getter materials and the housing.

14. The electron gun according to claim 13, wherein the elastic member is a coil spring or a leaf spring.

15. The electron gun according to claim 14, wherein said plurality of non-evaporable getter materials are individually formed bulk materials having a thickness of 1 mm or more.

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