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

Technical Field

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

Background Art

[0002] A charged particle beam apparatus is an apparatus that 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, reflected electrons, X-rays and the like emitted from the sample. In order to obtain an observation image with high spatial resolution, a high-brightness electron source (charged particle source) is required, and for example, a cold field emission (CFE) electron source is used. A CFE electron source emits an electron beam (charged particle beam) by concentrating an electric field on the tip of a sharpened single crystal (tip). If residual gas in a vacuum is adsorbed on the tip of the chip, the amount of emitted current becomes unstable. For this reason, it is necessary to lower the pressure around the electron source (charged particle source) (increase the degree of vacuum).

[0003] An electron source (charged particle source) is mounted on an electron gun (vacuum container) whose interior is evacuated. As a method for reducing the pressure in a vacuum container, a Non-Evaporable Getter (NEG) material is sometimes installed. Unlike conventional evaporable getters, the NEG material maintains its original shape without evaporating even when heated (activated) in vacuum. Once the NEG material is activated and returned to room temperature, it adsorbs and occludes gas, and has a vacuum evacuation effect. Patent Document 1 discloses an electron gun column including a sheet on which an NEG alloy is formed into a film.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, Patent Document 1 does not adequately consider the method of fixing the NEG material. The NEG material is a storage-type vacuum pump, and if its surface is covered with gas, it loses its pumping speed. Therefore, it is necessary to repeatedly activate it to diffuse the adsorbed gas into the material and clean the surface, thereby restoring the pumping speed. As a result of the inventors' research, it was found that because the thickness of the deposited NEG material is on the order of micrometers, the capacity to diffuse the adsorbed gas into the interior is small, and it reaches the end of its lifespan after several activations, making it impossible to restore the pumping speed. For this reason, it was not possible to maintain the stabilized current of the charged particle beam apparatus for a long period of time.

[0006] Research by other inventors revealed that bulk NEG material with a thickness of millimeters or more has a large capacity to diffuse adsorbed gases into its interior, and does not reach the end of its lifespan even after dozens of activations. By using bulk NEG material, a stable current can be maintained for a long period of time.

[0007] One challenge when using bulk NEG material is the need to directly contact and fix other components to the bulk NEG material. Since the thermal expansion coefficients of the bulk NEG material and the other components are different, stress is applied to the NEG material due to the difference in expansion during activation. As a result, it was found that the NEG material cracks and breaks, and fragments of the NEG material scatter into the surroundings as foreign matter. This foreign matter causes discharge and damages the electron source.

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

[0009] A charged particle source comprising a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament, Multiple non-evaporating getter materials, A housing is arranged to surround the axis of the electron beam emitted by the charged particle source, A charged particle beam apparatus comprising an extraction electrode having the housing, A heater for heating the plurality of non-evaporating getter materials is arranged on the extraction electrode, The plurality of non-evaporating getter materials are arranged in a row within the housing. The present invention is characterized in that an elastic member configured to press against the non-evaporative getter material is disposed between the non-evaporative getter material and the housing. [Effects of the Invention]

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

[0011] [Figure 1] This 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 apparatus. [Figure 2] This is a schematic cross-sectional view showing an example of the configuration of the CFE electron source and its surroundings in Example 1. [Figure 3] This is a schematic perspective view showing an example of the arrangement and fixing method of the NEG material in Example 1. [Figure 4] This is a schematic cross-sectional view illustrating an example of how the coil spring of Example 1 prevents malfunctions during the activation of the NEG material. [Figure 5] This is a schematic perspective view showing an example of the arrangement and fixing method of the NEG material in Example 2. [Figure 6] This is a schematic perspective view showing an example of the arrangement and fixing method of the NEG material in Example 3. [Figure 7] This is a schematic perspective view showing an example of the arrangement and fixing method of the NEG material in Example 4. [Figure 8] This is a schematic perspective view showing an example of the arrangement and fixing method of the NEG material in Example 5. [Modes for carrying out the invention]

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

[0013] The overall configuration of a scanning electron microscope, which is an example of a charged particle beam apparatus, will be described with reference to FIG. 1. A scanning electron microscope is an apparatus that irradiates a sample 102 with an electron beam 101, detects secondary electrons and reflected electrons emitted from the sample 102, and obtains an observation image of the sample 102. The scanning electron microscope includes a column 103 that maintains the inside thereof in a vacuum and a sample chamber 104. The column 103 is connected to a ground potential. The interior of the column 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 the top. An aperture through which the electron beam 101 passes is disposed at the center of an electrode separating each vacuum chamber, and each vacuum chamber is differentially evacuated. The pressure of the first vacuum chamber 105, the second vacuum chamber 106, the third vacuum chamber 107, and the fourth vacuum chamber 108 becomes higher as the vacuum chamber is lower (a vacuum chamber closer to the sample chamber 104). Hereinafter, 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.

[0014] The first vacuum chamber 105 is a space inside an extraction electrode 203, and is evacuated by a bulk NEG material 201. The pressure of the first vacuum chamber 105 is lower than the pressures of the other second vacuum chamber 106, third vacuum chamber 107, and fourth vacuum chamber 108, and is 1×10 -9 Pa to 1×10 -10 It is evacuated to an ultra-high vacuum region on the order of Pa or lower. 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 the two pins of the CFE electron source 202 via a flashing power supply 110, and normally a negative acceleration voltage of approximately -1 kV to -100 kV with respect to the ground potential supplied from the acceleration power supply 114 is applied. 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. The extraction electrode 203 has a cup-shaped 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 up to approximately +6 kV with respect to the acceleration voltage applied to the two pins of the CFE electron source 202 is applied. By applying the extraction voltage to the extraction electrode 203, an electron beam 101 is emitted from the CFE electron source 202.

[0016] When flashing the CFE electron source 202, the flashing power supply 110 applies a voltage obtained by adding approximately several volts to the negative acceleration voltage to one of the two pins, creates a potential difference of approximately several volts between the two pins, and applies a pulse current to the filament, thereby heating the filament to approximately 2000° C. (flashing). This flashing operation removes residual gas adsorbed on the CFE electron source 202 and resets the temporal change of the unstable emission current. Since the first vacuum chamber 105 and the second vacuum chamber 106 are differentially evacuated, there is a difference of several orders of magnitude in pressure between them. Details of the configuration of the CFE electron source 202 and its periphery will be described later with reference to Figure 2.

[0017] The second vacuum chamber 106 is a space surrounded by the electron gun vacuum vessel 121 and the acceleration electrode 113 outside the extraction electrode 203, and a piping 120 is connected thereto. An ion pump 111 and an auxiliary NEG pump 112 are provided at the end of the piping 120, and the second vacuum chamber 106 is evacuated. The pressure of the second vacuum chamber 106 is 1×10 -7 Pa to 1×10 -9This is an ultra-high vacuum region of approximately Pa. An accelerating electrode 113 is placed in the second vacuum chamber 106 and is isolated from the third vacuum chamber 107. The accelerating 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 accelerating voltage. An electrostatic lens is formed in the space where the extraction electrode 203 and the accelerating electrode 113 face each other. The extraction electrode 203 and the accelerating electrode 113 have a Butler lens structure to reduce electrostatic lens aberrations. The configuration above the accelerating electrode 113 is collectively called the electron gun 122. A baking heater 130 is placed outside the electron gun 122 under atmospheric pressure. The second vacuum chamber 106 is made an ultra-high vacuum by heating (baking) the entire electron gun 122 to approximately 200°C with the baking heater 130 while evacuating the electron gun 122 with an ion pump 111 and an auxiliary NEG pump 112.

[0018] The third vacuum chamber 107 is evacuated by an ion pump 115. A condenser lens 116 is placed in the third vacuum chamber 107. The condenser lens 116 focuses the electron beam 101, and the amount of current and other parameters are adjusted.

[0019] A detector 117 is placed in the fourth vacuum chamber 108. The detector 117 detects secondary electrons, backscattered electrons, etc., emitted from the sample 102. Multiple detectors 117 may be provided, and they may be placed in the sample chamber 104 or other first vacuum chambers 105, second vacuum chamber 106, and third vacuum chamber 107.

[0020] The sample chamber 104 is evacuated by a turbomolecular pump 118. The objective lens 119 and the 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 configuration of the CFE electron source 202 and its surroundings is illustrated using Figure 2. The CFE electron source 202 consists of a tip 204, a filament 205, two pins 206, an insulator 207, and a suppressor 123. The tip 204 has a sharpened tip. <310> or <111> The tip 204 is a tungsten single crystal needle with a radius of curvature of approximately 100 nm at its tip. 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 fitted to the outside of the insulator 207 and encloses the insulator 207, the pins 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. Its protruding length is approximately 0.1 mm to 3 mm.

[0022] The holder 208 is a metal cylinder that holds the entire CFE electron source 202 by fixing the suppressor 123. The holder 208 is connected to the electron gun vacuum chamber 121 via an insulator 252 and is electrically insulated from the electron gun vacuum chamber 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 during normal electron emission. A suppressor voltage is applied to the holder 208 and the suppressor 123 by the suppressor power supply 124. During flushing, the filament 205 is heated by the flushing power supply 110, which flushes the filament and removes residual gas adsorbed on the tip 204. The CFE electron source 202 does not necessarily have to be equipped with the suppressor 123, and can emit an electron beam even without it.

[0023] The extraction electrode 203 comprises a metal extraction electrode lower section 211, an extraction electrode side wall 210, a diaphragm 214, a housing 209, a coil spring 250, a load distribution plate 251, and an NEG material 201. The components other than the NEG material 201 are mainly made of materials such as stainless steel, titanium, and permalloy. The extraction electrode lower section 211 is positioned closest to the tip of the tip 204, with a height difference of approximately 0.3 mm to 10 mm between them. The housing 209 is connected to the extraction electrode lower section 211. The NEG material 201 is placed inside the housing 209. When an extraction voltage is applied to the extraction electrode 203, the components of the extraction electrode 203 also become subject to the extraction voltage and reach the same potential. The extraction electrode side wall 210 and the electron gun vacuum vessel 121 are connected via an insulator 252, electrically insulating them from each other. A differential exhaust port 213 connecting the first vacuum chamber 105 and the second vacuum chamber 106 may be provided in the side wall 210 of the extraction electrode. The conductance of the differential exhaust port 213 is made 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 positioned in the second vacuum chamber 106 and connected to the side of the extraction electrode side wall 210. By heating the heater 212 to 400°C or higher, more preferably to 500°C or higher, this heat is transferred to the housing 209 via the extraction electrode side wall 210, further heating and activating the NEG material 201 inside. By connecting the heater 212 to the extraction electrode 203, the heat conduction path from the extraction electrode 203 to the housing 209 and the NEG material 201 can be shortened, allowing the temperature of the NEG material 201 to rise efficiently and be activated. The heater 212 is a ceramic heater made of alumina, silicon nitride, boron nitride, aluminum nitride, etc. Ceramic heaters can sometimes release gas on a steady basis, worsening the pressure. Therefore, by positioning the heater 212 on the second vacuum chamber 106 side, the deterioration of the pressure in the first vacuum chamber 105 is prevented, and the pressure in the first vacuum chamber 105 is reduced.

[0025] The housing 209 consists of a lid 253 and a container 254, and the lid 253 and container 254 are fixed together with bolts or screws (not shown). The housing 209 is positioned to surround the chip 204, or the axis of the electron beam 101 emitted from the chip 204. The NEG material 201 is housed inside the housing 209. The number of NEG materials 201 arranged within the limited volume of the housing 209 is increased as much as possible. The NEG materials 201 are densely arranged in a circular pattern surrounding the axis of the electron beam 101. The NEG materials 201 may be arranged in two or more layers in the height direction. Arranging the NEG materials 201 in two or more layers 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 functions not only as a container for the NEG materials 201 but also as a heat conduction path, uniformly transferring heat to the NEG materials 201 and activating them when the heater 212 is heated. The housing 209 has an opening 216 only on the side of the first vacuum chamber 105, and the first vacuum chamber 105 is made into an extremely high vacuum by vacuum evacuation with the NEG material 201. The housing 209 also functions as a partition wall separating the first vacuum chamber 105 and the second vacuum chamber 106. By evacuating the first vacuum chamber 105 with the NEG material 201 and the second vacuum chamber 106 with the ion pump 111 or auxiliary NEG pump 112, the first vacuum chamber 105 and the second vacuum chamber 106 have a differential pumping structure. 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 rises due to discharge or electron shock 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 on the tip 204 is reduced, the attenuation of the electron beam 101 current and noise are reduced, and a stable electron beam is maintained.

[0026] The material of NEG material 201 is an alloy of zirconium, vanadium, and iron. NEG material 201 uses individually formed bulk material with a thickness of 1 mm or more. Having a thickness of 1 mm or more increases the capacity for diffusing adsorbed gases into the interior, thus extending the lifespan of NEG material 201. The shape of NEG material 201 is, for example, cylindrical, with a thickness, diameter, and height ranging from approximately 1 mm to 100 mm. Using bulk material with millimeter-order thickness for NEG material 201 increases the capacity for diffusing adsorbed gases into the interior, allowing for activation multiple times (tens of times or more), resulting in a practically sufficient lifespan for a charged particle beam apparatus. Increasing the number of NEG material 201 units placed within the housing 209 improves the exhaust speed and reduces the pressure in the first vacuum chamber 105. Since NEG material adsorbs gases onto its surface and is then evacuated, increasing the surface area of ​​NEG material 201 exposed to the first vacuum chamber 105 improves the exhaust speed. If a porous material made by sintering zirconium-vanadium-iron alloy powder is used for the NEG material 201, the effective surface area increases due to the micrometer-order irregularities on the surface, further improving the exhaust speed. The shape of the NEG material 201 is not limited to a cylinder; it can also be a block or a ring. Other materials may be used for the NEG material 201, and depending on the type of material, the temperature required for activation can be reduced to about 100°C. When the activation temperature is low, the NEG material 201 can be activated by heating the entire electron gun 122 with a baking heater 130 placed outside the electron gun 122. As a result, the heater 212 placed in the second vacuum chamber 106 can be omitted.

[0027] A sheet of NEG material can also be used as the NEG material 201. However, because the thickness of the deposited NEG material is on the order of micrometers, the capacity to diffuse adsorbed gases into the interior is small, and its lifespan is limited to a few activations. Furthermore, when a sheet is used as the NEG material 201, it is necessary to bend the sheet to increase the surface area of ​​the sheet mounted inside the housing in order to obtain a sufficient pumping speed. However, the deposited NEG material peels off at the bent area, generating a large amount of foreign matter. This foreign matter causes a discharge due to the voltage difference between the suppressor and the extraction electrode, damaging the chip 204. In addition, the composition distribution of NEG deposited on a sheet changes depending on the deposition conditions, resulting in variations in pumping speed from sheet to sheet. Therefore, there is a problem of differences in the pressure in the first vacuum chamber 105 from one device to another, resulting in differences in current stability between devices. On the other hand, bulk NEG material has small individual variations, and the pumping speed can be controlled by the number of pieces placed. Therefore, differences in the pressure in the first vacuum chamber 105 are less likely to occur between devices. Based on the above, using individually formed bulk material as NEG material 201 ensures sufficient lifespan and reduces the difference between foreign matter and the aircraft.

[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. By changing the suppressor voltage, the electric field at the tip of the tip 204 changes, and the amount of emission current can be adjusted. An aperture 214 is placed in the center of the lower part 211 of the extraction electrode. The hole diameter of the aperture 214 is typically 1 mm or less, more preferably 0.5 mm or less. The electron beam 101 passes through the hole of the aperture 214 and proceeds to the second vacuum chamber 106, spreading out in a cone shape to reach the accelerating electrode 113. An aperture 215 is placed in the center of the accelerating electrode 113. The outer periphery of the electron beam 101 is blocked by the aperture 215 and the accelerating electrode 113, and the central part proceeds to the third vacuum chamber 107. This electron beam proceeds further downward and is finally irradiated onto the sample 102.

[0029] Next, we will explain how the first vacuum chamber 105 is efficiently evacuated to an extremely high vacuum. The ion pump 111 and the auxiliary NEG pump 112 have their effective pumping speed limited by the conductance of the exhaust path in the piping 120, resulting in low efficiency in evacuating around the electron source (charged particle source). On the other hand, the NEG material 201 is positioned very close to the electron source (charged particle source) inside the extraction electrode 203, resulting in high conductance and a high effective pumping speed. Therefore, it efficiently evacuates around the electron source (charged particle source).

[0030] By pre-arranging multiple NEG material 201 inside the housing 209 and then mounting it in the electron gun, the assembly time can be reduced compared to mounting the NEG material 201 individually in the electron gun. In addition, the risk of foreign matter being generated by the NEG material 201 bumping against electron gun components during assembly is reduced. Furthermore, if the NEG material 201 reaches the end of its lifespan after many years of use, all of the NEG material 201 can be easily replaced with new ones simply by replacing the housing during maintenance of the charged particle beam device, thereby restoring the exhaust velocity.

[0031] The housing 209 is positioned to surround the chip 204 or the axis in the direction of propagation of the electron beam 101. In this configuration, the distance of the exhaust path between the NEG material 201 and the chip 204 is reduced, increasing the conductance and improving the effective exhaust speed. By positioning the housing 209 at the same height as the chip 204, the distance can be minimized and the conductance can be maximized. On the other hand, the housing 209 may be positioned at a different height from the chip 204. For example, if the housing 209 is made taller to accommodate a large amount of NEG material 201, space constraints may require the housing 209 to be positioned higher than the chip 204. Even in this case, positioning the housing 209 to surround the axis of the electron beam 101 minimizes the distance of the exhaust path from the chip 204 to any of the NEG material 201, thereby improving the conductance.

[0032] The first vacuum chamber 105 is a limited, narrow space confined to the inside of the extraction electrode 203, and because it contains a small number of components, the total amount of degassing is small. Furthermore, since the entire extraction electrode 203 is heated to a high temperature by the heater 212, molten hydrogen inside the components is removed, further reducing the amount of degassing per component. The combined effect of the improved effective pumping speed and reduced degassing amount achieved by placing the NEG material 201 inside the extraction electrode 203 allows the pressure in the first vacuum chamber 105 to be efficiently reduced to an extremely high vacuum, providing a stable discharge current from the CFE electron source 202.

[0033] The arrangement and fixing method of the NEG material 201 will be explained using Figure 3. Figure 3 is a perspective view of a part of the housing 209. In Figure 3, a cylindrical coordinate system is used, with the height direction represented as Z, the circumferential direction as θ, and the radial direction as R. The NEG material 201 is placed inside the housing container 254, and the housing lid 253 is placed over it from above. The NEG material 201 is arranged regularly in the circumferential direction (θ direction), and the NEG material 201 may be placed in contact with each other. In this way, a large number of NEG material 201 can be placed within the limited volume of the housing 209, and the pressure in the first vacuum chamber 105 is reduced by improving the exhaust speed. The NEG material 201 is arranged in two stages in the height direction (Z direction) to increase the number of pieces that can be placed inside the housing 209. The number of stages may be more than two. A load distribution plate 251-A may be placed between the lower NEG material 201-A and the upper NEG material 201-B. A load distribution plate 251-B and a coil spring 250-A are placed between the upper NEG material 201-B and the lid 253. The coil spring 250-A is placed between the load distribution plate 251-B and the lid 253, and it is preferable that there are multiple coil springs 250-A. The container 254 is equipped with a partition wall 303, and the container 254 and the partition wall 303 are formed as a single unit. A load distribution plate 251-C is placed between the end NEG materials 201-C and NEG materials 201-D and the partition wall 303. A coil spring 250-B may be placed between the partition wall 303 and the load distribution plate 251-C.

[0034] It is preferable that the load distribution plate 251-A is in contact with multiple NEG materials 201. The number of NEG materials in contact is such that at least two NEG materials are located at different positions in the circumferential direction and two NEG materials are located at different positions in the height direction, so that it is in contact with at least three different NEG materials. The load distribution plate 251-B is also in contact with multiple NEG materials, and at least two NEG materials are located at different positions in the circumferential direction. The load distribution plate 251-C is also in contact with multiple NEG materials, and at least two NEG materials are located at different positions in the height direction.

[0035] The coil spring 250 is a spring made by winding metal wire, and its elasticity is maintained even when heated during activation. The length of the coil spring 250 expands and contracts from its natural length, pressing against the parts it contacts in the direction of expansion and contraction, and maintaining the applied force.

[0036] When the lid 253 is placed over the container 254, the coil spring 250-A is compressed by the lid 253, applying a vertical force 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 multiple NEG material 201-B that it contacts below. The NEG material 201-B is fixed in place by being pressed. The multiple NEG material 201-B transmit the compressed force further to the load distribution plate 251-A below. The load distribution plate 251-A distributes the applied force and transmits it to the multiple NEG material 201-A that it contacts below, pressing and fixing them in place. In this way, the entire NEG material 201 is fixed by the coil spring 250-A, and the positional change of the NEG material 201, especially the positional change in the vertical direction, is reduced. By reducing the positional change, damage to the NEG material 201 can be suppressed. The coil spring 250 is elastic and returns to its original length when the cover 253 is removed. Therefore, it can be reused as long as its elasticity is maintained.

[0037] The coil spring 250-B is positioned 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, which it is in contact with, pressing and fixing them in place. NEG material 201-C and NEG material 201-D further transmit this force to other NEG material that are in circumferential contact, 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, and changes in the position of the NEG material 201, especially changes in its circumferential position, are reduced. By arranging the coil spring as described above, the NEG material 201 is pressed and fixed in terms of height and circumferential direction, preventing sliding, which is the collision or rubbing of the NEG material 201 with other parts due to movement from its predetermined position. Note that an additional coil spring 250 may be added to apply force in the radial direction. Even in this case, the entire NEG material 201 is fixed, and in particular, radial positional changes are reduced. By arranging multiple coil springs 250 and increasing the direction of pressure (height, circumference, and radius), the NEG material 201 is fixed more firmly. The dimensions of the NEG material 201, such as height and diameter, may not be constant, and a gap may form between the lid 253 of the housing 209 and the NEG material 201-B, causing the NEG material 201 to move. Therefore, by arranging a coil spring 250 that presses in the height direction, collisions and sliding due to the movement of the NEG material 201 are prevented. If the direction in which the lid 253 of the housing 209 is placed is circumferential, gaps are more likely to form in the circumferential direction, so it is more preferable to arrange a coil spring 250 that presses in the circumferential direction. If the direction in which the lid 253 is placed is radial, gaps are more likely to form in the radial direction, so it is more preferable to arrange a coil spring 250 that presses in the radial direction.

[0038] An exhaust path 306 is formed in the adjacent spaces around the coil spring 250 in the circumferential direction. The exhaust path 306 functions as a vacuum exhaust path with high conductance, contributing to the vacuum exhaust of the radially outer (larger radius) surface of the NEG material 201, thereby improving the effective exhaust speed.

[0039] The load distribution plate 251 is a metal plate with a fixed width and length, and distributes stress by making surface contact with the NEG material 201. The load distribution plate 251 equalizes the force of the coil spring 250, and further equalizes the force by contacting multiple NEG materials 201, preventing stress concentration and cracking of the NEG material 201. The more NEG materials 201 that the load distribution plate 251 contacts, the more uniform the stress becomes, suppressing cracking of the NEG material 201 due to stress concentration. In addition, by using the load distribution plate 251, force can be applied to and fixed to the entire NEG material 201 even if the number of coil springs 250 installed is reduced. Furthermore, by performing spherical or chamfering on the end faces of the load distribution plate 251, cracking of the NEG material 201 caused by sharp end faces contacting the NEG material 201 can be suppressed. The load distribution plate 251 is provided with a convex-shaped positioning part 301, and the coil spring 250 is placed over it. By positioning the coil spring 250 in a predetermined positioning section 301, the stress applied to the NEG material 201 is prevented from being unevenly distributed. The positioning section 301 may have a concave shape, and other components may be combined with it.

[0040] Another effect of the load distribution plate 251 is that, compared to the case where multiple NEG materials 201 are stacked in contact, the surface area exposed to the first vacuum chamber 105 increases. By making the width of load distribution plate 251-A narrower than the width of the NEG material 201 it contacts, the upper surface 304 of NEG material 201-A is exposed to the vacuum. As a result, the upper surface 304 contributes to vacuum evacuation. Similarly, by making the width of load distribution plate 251-B narrower than the width of the NEG material 201 it contacts, the upper surface 305 of NEG material 201-B is exposed, contributing to vacuum evacuation. In addition, a surface exposed to the vacuum is created on the lower side of NEG material 201-B. By placing the load distribution plates between the NEG materials 201 in this way and exposing part of the upper or lower surface of the NEG material 201 to the vacuum, the evacuation speed of the NEG material 201 can be improved. Furthermore, the load distribution plate 251 may also be provided with an opening 302. By providing the opening 302, the surface of the NEG material 201 facing the opening 302 is exposed to the vacuum, contributing to vacuum evacuation. As a result, the evacuation speed can be improved.

[0041] When the NEG material 201 moves from its predetermined position, the exposed area in the vacuum changes, which can reduce the exhaust speed. Furthermore, if the moved NEG material 201 collides with or slides against other parts or other NEG material 201, it may break and generate foreign matter. In particular, when a sintered body is used for the NEG material 201, its surface has micrometer-order irregularities, which can easily crack and become foreign matter. Therefore, it is necessary to hold the NEG material 201 in contact with other parts to prevent movement and sliding. As in this embodiment, using the coil spring 250 fixes the NEG material 201, reducing collisions and sliding due to movement. Bulk NEG material 201 can crack and break if stress concentrates on certain parts, such as corners, generating a large amount of foreign matter. However, using the load distribution plate 251 prevents stress concentration. Causes of movement of the NEG material 201 include vibrations during equipment assembly and transportation, and earthquakes. On the other hand, even when the NEG material 201 is fixed, activation can cause problems such as cracking of the NEG material 201 and the formation of gaps in the housing 209. The effect of using the coil spring 250 to prevent these activation problems will be explained next.

[0042] Using Figure 4, the function of this configuration in preventing malfunctions during the activation of the NEG material 201 is explained. In order to give the NEG material 201 exhaust capacity, it is necessary to activate it by heating it to 400°C or higher. Here, since the thermal expansion coefficients of the NEG material 201, the load distribution plate 251, the container 254, and the lid 253 are different, malfunctions occur when they expand during heating and their lengths change. The coil spring 250 reduces these malfunctions during activation.

[0043] Figure 4(A) is a cross-sectional view of a portion of the housing 209 when the coil spring 250 is not used. In this configuration, as an example, three layers of NEG material 201 are arranged in the height direction, and the lid 253 is in contact with the uppermost layer of NEG material 201 to fix the entire NEG material 201. When activation is performed in this configuration, the sum of the lengths L1 of the NEG material 201 and the load distribution plate 251 may become longer than the inner height L2 of the container 254 due to thermal expansion. At this time, the lid 253 applies a downward force to the NEG material 201. If this force concentrates on the corners of the NEG material 201, cracks 401 occur, and a portion of the NEG material 201 breaks and falls off. In addition, a large amount of granular foreign matter is generated from the cracks 401, which damages the tip 204 through 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 a gap 402 occurs, the housing 209 ceases to function as a partition, and the first vacuum chamber 105 and the second vacuum chamber 106 become connected through the gap 402. As a result, the pressure in the first vacuum chamber increases (deteriorates). Also, because the differential pumping effect of the first vacuum chamber 105 is lost, if the pressure in the second vacuum chamber 106 increases due to discharge or electron shock desorption, the pressure in the first vacuum chamber 105 will also increase, making it impossible to stabilize the current. In addition, if the height L2 of the container becomes longer than L1 due to thermal expansion, the NEG material 201 will no longer be fixed by the lid 253, and the movement of the NEG material 201 will cause collisions and sliding with other parts.

[0044] Figure 4(B) is a cross-sectional view of a portion of the housing 209 when a coil spring 250 is used. In this configuration, NEG material 201 is arranged in two stages in the height direction, and the coil spring 250 and load distribution plate 251 are placed between the lid 253 and the NEG material 201. When activation is performed with this configuration, the coil spring 250 expands and contracts, changing 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 compresses while maintaining pressure on the NEG material 201. At this time, since the coil spring 250 is an elastic body, the pressing force is sufficiently smaller than the force of the rigid lid 253 shown in Figure 4(A). In addition, the force of the coil spring 250 is distributed across the entire NEG material 201 by the load distribution plate 251. As a result, cracks 401 in the NEG material 201 are prevented. Furthermore, the compression of the coil spring 250 prevents the lid 253 from changing position, and no gaps 402 occur in the housing 209. As a result, differential exhaust between the first vacuum chamber 105 and the second vacuum chamber 106 is maintained. Moreover, even if the height L2 of the container increases due to thermal expansion, the coil spring 250 extends, maintaining the pressure on the NEG material 201 and keeping it fixed. As a result, collisions and sliding due to movement of the NEG material 201 are prevented even when heated. Furthermore, even after activation is complete and the system 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 remains compressed and fixed. As described above, by positioning the coil spring 250 and allowing it to expand and contract, positional changes due to thermal expansion of other components are absorbed even during heating, preventing malfunctions.

[0046] While Figure 4 illustrates the effect of coil springs 250 arranged in the height direction, coil springs arranged in the circumferential direction also prevent cracks 401 and gaps 402 in the NEG material 201 caused by circumferential thermal expansion, as well as collisions and sliding due to movement of the NEG material 201. In addition, coil springs 250 may also be arranged in the radial direction (R direction), and in this case as well, problems caused by radial thermal expansion will be similarly prevented.

[0047] As described above in this embodiment, by fixing the NEG material 201 using the coil spring 250, it is possible to reduce the decrease in exhaust speed due to the movement of the NEG material 201 and the generation of foreign matter caused by collisions and sliding with other parts and other NEG materials. Furthermore, by using the coil spring 250, cracking of the NEG material 201 and generation of foreign matter that occur when the NEG material 201 is activated, and the generation of gaps 402 in the housing 209 are prevented. In addition, extremely high vacuum is achieved by efficiently evacuating the first vacuum chamber 105 using the NEG material 201. 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 with a thickness on the order of millimeters that is individually formed on the NEG material 201, the lifespan is extended, foreign matter is reduced, and differences in exhaust speed between machines are reduced. As a result, a charged particle beam apparatus with stable current over a long period of time is provided. [Examples]

[0048] Example 1 describes a configuration in which the NEG material 201 is fixed using a coil spring 250. Example 2 describes a configuration in which the coil spring 250 is used to fix the material when there is no partition wall 303 in the container. Note that some of the configurations and functions described in Example 1 can be applied to Example 2, so the same reference numerals are used for similar configurations and functions and their descriptions are omitted.

[0049] Using Figure 5, the method for fixing the NEG material 201 in this embodiment will be explained. 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. To fix the NEG material 201 in the circumferential direction, load distribution plates 251-C and 251-D are placed between the NEG material 201-C at one end and the NEG material 201-E at the other opposing end. A coil spring 250-B is placed between the load distribution plates 251-C and 251-D. The coil spring 250-B is placed in a contracted state from its natural length and applies 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 sequentially transmitted to other NEG material 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 stress, preventing cracking and the generation of foreign matter in the NEG material 201. The coil spring 250-B also applies force to the load distribution plate 251-D, which is facing in the opposite direction in the circumferential direction. This force is distributed and transmitted to the NEG material 201-E and NEG material 201-F, and then sequentially to other NEG material 201 that are not shown. As a result, the entire NEG material 201 is pressed and fixed. Even when 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 load distribution plate 251 between adjacent NEG material 201, and the positional change of the NEG material 201, especially the positional change in the circumferential direction, is 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 the displacement in response to thermal expansion, preventing the formation of cracks 401, foreign matter, and gaps 402 in the housing 209. In this embodiment, the coil spring 250 is placed between adjacent NEG material 201 in the circumferential direction, but similar effects can be obtained by placing the coil spring 250 and load distribution plate 251 between adjacent NEG material 201 in the height direction or radial direction. [Examples]

[0050] Example 2 describes a configuration in which a coil spring 250 is used for fixing when there is no partition wall 303 in the container. Example 3 describes a configuration in which a leaf spring 601 is used for fixing instead of the coil spring 250. Note that some of the configurations and functions described in Examples 1 and 2 can be applied to Example 3, so the same reference numerals are used for similar configurations and functions and their descriptions are omitted.

[0051] Using Figure 6, the method for fixing the NEG material 201 in this embodiment will be explained. The leaf spring 601 has a structure in which a metal plate is folded. The bellows-shaped metal plate has elasticity that allows it to expand and contract as it folds, and maintains the state in which force is applied by pressing on the contacted part. By making the leaf spring 601 out of metal, its elasticity is maintained even when heated during activation.

[0052] A leaf spring 601-A is positioned between the NEG material 201 and the lid 253. When the lid 253 is placed over the container 254, the leaf spring 601-A is compressed by the lid 253, applying a force in the height direction. This force is distributed and transmitted to the multiple NEG materials 201 that are in contact below, and 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 compressed, fixing its position, and in particular, positional changes in the height direction are reduced. The leaf spring 601 is elastic and returns to its original length when the lid 253 is removed. Therefore, it can be reused.

[0053] A leaf spring 601-B is positioned between the container partition wall 303 and the NEG material 201. The leaf spring 601-B is positioned in a contracted state and applies force in the circumferential direction. This force is distributed and transmitted to multiple contacting NEG materials 201, and further 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, especially positional changes in the circumferential direction, are reduced.

[0054] Because the leaf spring 601 has a surface structure, it can apply uniform stress through surface contact. As a result, stress concentration on a part of the NEG material 201, preventing cracking or the generation of foreign matter, is prevented. Furthermore, since the leaf spring 601 can contact multiple NEG materials 201, it itself has the effect of distributing force similar to that of a load distribution plate. For this reason, the load distribution plate 251-B adjacent to the coil spring 250 described in Example 1 can be omitted, reducing the number of parts.

[0055] As in this embodiment, the NEG material 201 can be fixed using the leaf spring 601, preventing collisions and sliding caused by the movement of the NEG material 201. Furthermore, when the NEG material 201 is activated, the leaf spring 601 absorbs the displacement in response to thermal expansion, preventing the formation of cracks 401, foreign matter, and gaps 402 in the housing 209. [Examples]

[0056] Example 3 describes a configuration in which a leaf spring 601 is used for fixing. Example 4 describes a configuration in which a leaf spring 701 is arranged radially for fixing. Note that some of the configurations and functions described in Examples 1 to 3 can be applied to Example 4, so the same reference numerals are used for similar configurations and functions and their descriptions are omitted.

[0057] Figure 7 illustrates the method for fixing the NEG material 201 in this embodiment. In this configuration, the NEG material 201 is arranged in two radial rows, increasing the number of NEG material 201 mounted inside the housing 209 and improving the exhaust speed. The NEG material 201-G of the first radial row and the NEG material 201-H of the second radial row are in contact with each other, and furthermore, NEG material 201 in the same row are in contact with each other in the circumferential direction. As a result, a large number of NEG material 201 are mounted inside the housing 209, increasing the exhaust speed. The load distribution plate 251 is also widened in the radial direction, and is in contact with both the first and second radial rows of NEG material 201 to distribute and transmit the force of the coil spring 250 to both rows. The opening 302 provided in the load distribution plate 251 is widened so as to span both 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 the same as that of the leaf spring 601 described in Example 3, and is a structure in which a metal plate is folded, applying force by pressing on the contacted parts. Its elasticity is maintained even when heated during activation.

[0059] The leaf spring 701 is positioned in a compressed state and applies a force in the radial direction. This force is distributed and transmitted to the second radial row of NEG material 201-H that it contacts. Furthermore, this force is transmitted to the inner first radial row of NEG material 201-G. As a result, the entire NEG material 201 is pressed and fixed, and radial positional changes are reduced in particular. Alternatively, a load distribution plate may be added between the first radial row of NEG material 201-G and the second radial row of NEG material 201-H. In this case, the force pressing on the second radial row of NEG material 201-H is further distributed and averaged by the added load distribution plate and transmitted to the first radial row of NEG material 201-G.

[0060] Similar to Example 3, the leaf spring 701 has a surface structure, so stress is made uniform through surface contact. As a result, stress concentration in a part of the NEG material 201 prevents cracking and the generation of foreign matter.

[0061] As in this embodiment, the NEG material 201 can be fixed even when using the leaf spring 701, preventing collisions and sliding caused by the movement of the NEG material 201. Furthermore, when the NEG material 201 is activated, the leaf spring 701 absorbs the displacement in response to thermal expansion, preventing the formation of cracks 401, foreign matter, and gaps 402 in the housing. [Examples]

[0062] Example 4 describes a configuration in which leaf springs 701 are arranged and fixed radially. Example 5 describes a configuration in which shim spacers 801 are arranged and fixed. Note that some of the configurations and functions described in Examples 1 to 4 can be applied to Example 5, so the same reference numerals are used for similar configurations and functions and their descriptions are omitted.

[0063] Figure 8 illustrates the method for fixing the NEG material 201 in this embodiment. In this configuration, the NEG material 201 is fixed with a metal, elastic shim spacer 801. The shim spacer is preferably annealed to soften it and give it elasticity. Stainless steel, permalloy, titanium, titanium alloy, aluminum alloy, or copper alloy can be used for the shim spacer 801.

[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 thickness. When the lid 253 is placed over the container 254, the shim spacer 801-A is pressed by the lid 253 and compresses slightly, applying a force in the height direction. This force is distributed and transmitted to the multiple NEG material 201 that are in contact below, and further transmitted to the multiple NEG material 201 in the lower row via the load distribution plate 251. As a result, the entire NEG material 201 is pressed down, fixing its position, and in particular, positional changes in the height direction are reduced. The shim spacer 801 is elastic and returns to its original length when the lid 253 is removed. Therefore, it can be reused.

[0065] A shim spacer 801-B is placed between the container partition wall 303 and the NEG material 201. The shim spacer 801-B has a block-like structure. The shim spacer 801-B is pressed into the container 254 and applies a force in the circumferential direction. This force is distributed and transmitted to multiple contacting NEG material 201s, and further transmitted to adjacent NEG material 201s in the circumferential direction. As a result, the entire NEG material 201 is pressed and fixed, and the positional change of the NEG material 201, especially the positional change in the circumferential direction, is reduced.

[0066] The shim spacer 801 has a surface structure and can compress the NEG material 201 by making surface contact with it, thereby uniformly distributing stress. As a result, stress concentration on a part of the NEG material 201, which can cause cracking or foreign matter to form, is prevented. Furthermore, since the shim spacer 801 can contact multiple NEG material 201s, it itself has the same effect as a load distribution plate. For this reason, the coil spring 250 described in Example 1 and the adjacent load distribution plates 251-B and 251-C can be omitted, reducing the number of parts.

[0067] As in this embodiment, the NEG material 201 can be fixed even when using the shim spacer 801, preventing collisions and sliding caused by the movement of the NEG material 201.

[0068] Multiple 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 and implemented without departing from the spirit of the invention. For example, the coil spring 250-A and load distribution plate 251-B of Example 1 may be combined with the leaf spring 601-B of Example 3. Also, instead of the coil spring 250 and the leaf spring 601, spiral springs, bamboo springs, disc springs, decorative springs, ring springs, etc. may be used. Furthermore, instead of tungsten single crystal, low work function materials such as CeB6 and LaB6, or materials with an inert surface such as carbon-coated materials may be used as the tip 204. Furthermore, nanowire electron sources or single-atom electron sources with a tip radius of curvature sharpened from tens of nanometers or a few atoms to about one atom may be used. In addition, the charged particle source to which the present invention can be applied is not limited to CFE electron sources, but can also be Schottky electron sources and ion sources. An example of an ion source is a gas field ionization ion source, and the tip 204 is <111> By using a tungsten single crystal with a specific crystal orientation and applying a positive voltage to the tip 204 relative to the extraction electrode 203, an ion beam can be emitted from the tip 204 as a charged particle beam, even with the same overall apparatus configuration. Furthermore, to obtain a stable emission current from a Schottky electron source, 1 × 10⁻¹⁰ -7 An ultra-high vacuum of less than Pa is required. By applying this invention, efficient vacuum evacuation around the electron source (charged particle source) can be achieved, enabling both efficient vacuum evacuation and miniaturization of the charged particle beam apparatus. Furthermore, the effect of pressure rise in the second vacuum chamber is reduced, making it easier to maintain a stable emission current. [Explanation of symbols]

[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...Drawer power supply, 110...Flushing power supply, 111...Ion pump, 112...Auxiliary NEG pump, 113...Accelerating electrode, 114...Accelerating 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…drawout electrode, 204…tip, 205…filament, 206…pin, 207…insulator, 208…holding part, 209…housing, 210…drawout electrode side wall, 211…lower part of drawout electrode, 212…heater, 213…differential exhaust port, 214…restrictor, 215…restrictor, 216…opening, 250…coil spring, 251…load distribution plate, 252…insulator, 253…lid, 254…container, 301…positioning part, 302…opening, 303…partition, 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 source comprising a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament, Multiple non-evaporating getter materials, A housing is arranged to surround the axis of the electron beam emitted by the charged particle source, A charged particle beam apparatus comprising an extraction electrode having the housing, A heater for heating the plurality of non-evaporating getter materials is arranged on the extraction electrode, The plurality of non-evaporating getter materials are arranged in a row within the housing. A charged particle beam apparatus characterized in that an elastic member configured to press the non-evaporating getter material is disposed between the non-evaporating getter material and the housing.

2. The charged particle beam apparatus according to claim 1, characterized in that the elastic member is a coil spring or a leaf spring.

3. The charged particle beam apparatus according to claim 2, characterized in that the plurality of non-evaporating getter materials are individually formed bulk materials having a thickness of 1 mm or more.

4. The charged particle beam apparatus according to claim 3, further comprising load distribution plates in contact with the plurality of non-evaporating getter materials.

5. The charged particle beam apparatus according to claim 4, characterized in that the load distribution plate has an opening.

6. The charged particle beam apparatus according to claim 3, characterized in that the elastic member is arranged such that the non-evaporating getter material is pressed in the height direction.

7. The charged particle beam apparatus according to claim 3, characterized in that the non-evaporating getter material is arranged in two or more stages in the height direction.

8. The charged particle beam apparatus according to claim 3, characterized in that a plurality of the elastic members are arranged such that the non-evaporating getter material is pressed from two or more different directions.

9. The non-evaporating getter material is arranged, and a first vacuum chamber is located inside the extraction electrode, The heater and the extraction electrode are arranged in a second vacuum chamber, the second vacuum chamber having a higher pressure than the first vacuum chamber. The charged particle beam apparatus according to claim 3, characterized in that the housing has an opening only on the side of the first vacuum chamber.

10. A charged particle source comprising a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament, Multiple non-evaporating getter materials, A housing is arranged to surround the axis of the electron beam emitted by the charged particle source, A charged particle beam apparatus comprising an extraction electrode having the housing, A heater for heating the plurality of non-evaporating getter materials is arranged on the extraction electrode, The plurality of non-evaporating getter materials are arranged in a row within the housing. A charged particle beam apparatus characterized in that an elastic member configured to press against the non-evaporating getter material is disposed between the non-evaporating getter materials.

11. The charged particle beam apparatus according to claim 10, characterized in that the elastic member is a coil spring or a leaf spring.

12. The charged particle beam apparatus according to claim 11, characterized in that the plurality of non-evaporating getter materials are individually formed bulk materials having a thickness of 1 mm or more.

13. A charged particle source comprising a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament, Multiple non-evaporating getter materials, A housing is arranged to surround the axis of the electron beam emitted by the charged particle source, A charged particle beam apparatus comprising an extraction electrode having the housing, A heater for heating the plurality of non-evaporating getter materials is arranged on the extraction electrode, The plurality of non-evaporating getter materials are arranged in a row within the housing. An electron gun characterized in that an elastic member configured to press against the non-evaporating getter material is disposed between the non-evaporating getter material and the housing.

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

15. The electron gun according to claim 14, characterized in that the plurality of non-evaporating getter materials are individually formed bulk materials having a thickness of 1 mm or more.

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