Charged particle beam device

Abstract

This charged particle beam device is characterized by comprising: a charged particle source (202) provided with a single crystal needle (204), a filament (205) connected to the single crystal needle, and an insulator (207) for holding the filament; a non-evaporable getter material (201); an extraction electrode (203); a first vacuum chamber (105) which is inside the extraction electrode and in which the charged particle source and the non-evaporable getter material are disposed; a heater (212) for heating the non-evaporable getter material; a second vacuum chamber (106) in which the heater and the extraction electrode are disposed and which has a pressure higher than that of the first vacuum chamber; and a heat absorption plate (250) connected to the extraction electrode and disposed so as to face the heater. The charged particle beam device is also characterized in that: the heater and the non-evaporable getter material are disposed in order with respect to a direction in which a charged particle beam is emitted from the charged particle source; and the non-evaporable getter material is disposed in the first vacuum chamber and the heater is disposed in the second vacuum chamber.

Description

charged particle beam equipment

[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 adheres 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 method for lowering the pressure inside the vacuum vessel is to mount a non-evaporable getter (NEG) material. Unlike conventional evaporable 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 microscope equipped with an NEG material near the extraction electrode.

[0004] Patent No. 6777746

[0005] However, Patent Document 1 does not sufficiently consider the activation temperature of the NEG material. As a result of research by the inventors, it was found that unless the activation temperature of the NEG material is above a certain temperature, the vacuum pumping effect does not occur and the pressure cannot be reduced. In this case, a stable electron beam (charged particle beam) cannot be obtained from the electron source (charged particle source), and the reliability of the observed image is impaired.

[0006] Therefore, an object of the present invention is to provide a charged particle beam device that can improve the activation temperature by efficiently heating the NEG material and that is small in size.

[0007] A charged particle beam device according to one embodiment of the present invention comprises a vacuum vessel, a charged particle source including a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament, a non-evaporable getter material, an extraction electrode, a first vacuum chamber in which the charged particle source and the non-evaporable getter material are arranged and which is located inside the extraction electrode, a heater for heating the non-evaporable getter material, a second vacuum chamber in which the heater and the extraction electrode are arranged and which has a higher pressure than the first vacuum chamber, and a heat absorption plate connected to the extraction electrode and arranged opposite the heater, wherein the heater and the non-evaporable getter material are arranged in that order in the direction in which the charged particle beam is emitted from the charged particle source, and the non-evaporable getter material is arranged in the first vacuum chamber, and the heater is arranged in the second vacuum chamber.

[0008] According to the present invention, it is possible to provide a small charged particle beam device that stabilizes the emission current by improving the activation temperature of the NEG material and efficiently reducing the pressure around the electron source (charged particle source).

[0009] 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 the configuration of a CFE electron source and its periphery of Example 1. FIG. 3 is a schematic cross-sectional view showing an example of the effect of a heat absorbing plate of Example 1 to improve the heating efficiency of an NEG material. FIG. 4 is a schematic cross-sectional view showing an example of the effect of the emissivity of an extraction electrode of Example 1 to improve the heating efficiency of an NEG material. FIG. 5 is a diagram showing an example of the effect of a heat absorbing plate of Example 1 to improve the heating efficiency of an NEG material. FIG. 6 is a diagram showing an example of the effect of a heat absorbing plate of Example 1 to stabilize the current of an electron beam. FIG. 7 is a schematic cross-sectional view showing an example of a configuration in which a heat reflecting plate of Example 2 improves the heating efficiency of an NEG material. FIG. 8 is a perspective view showing an example of an enlarged portion of the configuration of an NEG material of Example 1.

[0010] 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.

[0011] 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, detects secondary electrons and backscattered electrons emitted from the sample 102, and generates 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. Apertures through which the electron beam 101 passes are located at the center of the electrodes separating the vacuum chambers, and differential pumping is performed. The pressure in each of the vacuum chambers 105, 106, 107, and 108 increases toward the lower vacuum chamber (the vacuum chamber closest to the sample chamber 104). Below, the vacuum chambers 105, 106, 107, and 108 and the sample chamber 104 will be described.

[0012] The first vacuum chamber 105 is the space inside the extraction electrode 203, and is evacuated by the NEG material 201. The pressure in the first vacuum chamber 105 is the lowest among the other vacuum chambers 106, 107, and 108, and is 1×10 －９ Pa to 1 x 10 －１０ The 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.

[0013] 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 is normally applied to the CFE electron source 202 relative to the ground potential supplied from the acceleration power supply 114. A suppressor power supply 124 is connected to the suppressor of the CFE electron source 202. 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 is applied to the extraction electrode 203 relative to the negative acceleration voltage applied to the two pins of the CFE electron source 202. When the extraction voltage is applied to the extraction electrode 203, an electron beam 101 is emitted from the CFE electron source 202.

[0014] 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.

[0015] 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 －９ It is an ultra-high vacuum region of about 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, which reduces aberrations of the electrostatic lens. The configuration above the acceleration electrode 113 is collectively called the electron gun 122.

[0016] 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.

[0017] A detector 117 is disposed in the fourth vacuum chamber 108. The detector 117 detects secondary electrons and backscattered electrons emitted from the sample 102. A plurality of detectors 117 may be provided, and may be disposed in the sample chamber 104 or other vacuum chambers 105, 106, and 107.

[0018] 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.

[0019] 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 1 mm.

[0020] 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 vessel 121 via an insulator 252 and is electrically insulated. 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 normally applied to them. A suppressor voltage is applied to the holder 208 and the suppressor 123 by the suppressor power supply 124. During flushing, the flushing power supply 110 applies a voltage obtained by adding several volts to the negative acceleration voltage to one of the two pins 206, creating a potential difference of several volts between the two pins 206, thereby electrically heating the filament 205 and removing (flushing) residual gas adsorbed to the tip 204. Note that the CFE electron source 202 does not necessarily have to include the suppressor 123, and can emit electron beams even without it.

[0021] The extraction electrode 203 is composed of a metallic extraction electrode lower part 211, extraction electrode side wall 210, aperture 214, NEG unit 209, heat absorption plate 250, heat conduction plate 251, and NEG material 201. Stainless steel, titanium, permalloy, etc. are used as the main materials for the parts other than the NEG material 201. The extraction electrode lower part 211 is disposed in a position facing the tip of the chip 204 and closest to it, and the two are separated by approximately 0.3 mm to 10 mm in the height direction. The NEG unit 209 is connected to the extraction electrode lower part 211. The NEG material 201 is disposed inside the NEG unit 209.

[0022] The NEG unit 209 is a thermally conductive container made of metal, which transfers heat evenly throughout when heated to maintain a constant temperature. The NEG unit 209 may be made of a material with high thermal conductivity, such as stainless steel, titanium, permalloy, copper, silver, gold, or aluminum. Alternatively, these may be deposited on the surface. The NEG unit 209 has an opening 216 only on the first vacuum chamber 105 side, and the first vacuum chamber 105 is evacuated using the NEG material 201. A thermally conductive plate 251 may be provided inside the NEG unit 209. The material of the thermally conductive plate 251 is the same as that of the NEG unit 209, and more preferably, a material with high thermal conductivity is used, or a film of such a material may be deposited.

[0023] The NEG material 201 is a porous cylindrical pill made of a sintered alloy of zirconium, vanadium, and iron, and multiple pieces are arranged inside the NEG unit 209. The NEG material 201 may be other NEG materials and may have a shape other than a pill, such as a block, sheet, ring, thin film, or a combination of these. Also, only one piece may be arranged. The temperature at which the NEG material 201 is activated is approximately 500°C, and varies depending on the material. The closer the heating temperature of the NEG material 201 is to this activation temperature, the faster the exhaust speed will be.

[0024] An extraction voltage is applied to the extraction electrode 203, and its components are at the same potential. The extraction electrode sidewall 210 is connected to the electron gun vacuum vessel 121 via an insulator 252 and is electrically insulated. The electric field at the tip of the tip 204 is determined by the potential formed by the extraction electrode 203, and the electron beam 101 is emitted from the tip 204 by field emission. A positive or negative suppressor voltage with respect to the tip 204 is applied to the suppressor 123, and the electric field at the tip of the tip 204 is adjusted. An aperture 214 is disposed in the center of the extraction electrode lower portion 211. The hole diameter of the aperture 214 is typically 1 mm or less, more preferably 0.5 mm or less.

[0025] The electron beam 101 passes through a hole in the aperture 214 and proceeds to the second vacuum chamber 106, and then expands in a cone shape before reaching the acceleration electrode 113. An aperture 215 is disposed in 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, and the central portion proceeds to the third vacuum chamber 107.

[0026] The pressure in the vacuum chamber decreases as the effective pumping speed of the vacuum pump increases and the amount of outgassing from components in the vacuum chamber decreases. The effective pumping speed increases as the pumping speed of the vacuum pump itself increases and the conductance of the pumping path increases. The effective pumping speed of the ion pump 111 and the auxiliary NEG pump 112 is limited by the conductance of the piping 120, resulting in a low effective pumping speed around the electron source (charged particle source). On the other hand, the NEG material 201 is located very close to the electron source (charged particle source) inside the extraction electrode 203, resulting in a high conductance and a high effective pumping speed. This allows for efficient vacuum pumping around the electron source (charged particle source). Meanwhile, the first vacuum chamber 105 is a limited, narrow space confined only to the extraction electrode 203, and contains a small number of components, resulting in a small total amount of outgassing. Furthermore, the heater 212 heats the entire extraction electrode 203 to a high temperature once, thereby removing molten hydrogen from the components and reducing outgassing. As a result, the pressure in the first vacuum chamber 105 is efficiently reduced, and a stable emission current can be obtained from the CFE electron source 202 .

[0027] A differential pumping port 213 connecting 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 reduced to create a pressure difference of several orders of magnitude between the first vacuum chamber 105 and the second vacuum chamber 106. On the other hand, when the NEG material 201 is activated, the pressure in the first vacuum chamber 105 temporarily exceeds the pressure in the second vacuum chamber 106 due to the release of hydrogen gas and the like from the NEG material 201. Gases such as hydrogen released from the NEG material 201 are released into the second vacuum chamber 106 through this differential pumping port 213 and are pumped out by the ion pump 111 and the auxiliary NEG pump 112. By sufficiently removing the hydrogen gas released by the NEG material 201, the pumping speed of the NEG material 201 after activation is increased. In addition, rare gases that cannot be pumped by the NEG material 201 are pumped out by the ion pump 111. The differential pumping port 213 may have a circular or elongated shape. It is also effective to make the opening area of ​​the differential pumping port 213 larger than the opening area of ​​the aperture 214. The aperture 214 also functions as a differential pumping hole, but since its hole diameter is small, its conductance is small and its effect is limited.

[0028] Because the first vacuum chamber 105 and the second vacuum chamber 106 are isolated and differentially pumped, the pressure in the first vacuum chamber 105 is less likely to increase even if the pressure in the second vacuum chamber 106 increases. The pressure in the second vacuum chamber 106 may increase due to gas flowing in from the sample chamber 104, electron stimulated desorption gas emitted from the aperture 215 and acceleration electrode 113 irradiated with the electron beam 101, sudden discharge, etc. However, due to the effect of differential pumping, the pressure increase in the first vacuum chamber 105 is several orders of magnitude smaller than the pressure increase in the second vacuum chamber 106. Therefore, even if the pressure in the second vacuum chamber 106 deteriorates, the pressure in the first vacuum chamber 105 remains low, and a stable emission current is maintained.

[0029] Another advantage of differentially pumping the first vacuum chamber 105 and the second vacuum chamber 106 is that the electron gun 122 can be made smaller. By efficiently evacuating the area around the electron source (charged particle source) using the NEG material 201, the pressure in the first vacuum chamber 105 remains low even if the capacity of the ion pump 111 and the auxiliary NEG pump 112 is reduced to increase the pressure in the second vacuum chamber 106. By miniaturizing or omitting the ion pump 111 and the auxiliary NEG pump 112, the electron gun 122 can be made smaller, reducing costs and reducing the floor space or height of the charged particle beam device. Furthermore, the weight of the electron gun 122 is reduced, improving the resistance to mechanical vibrations of the charged particle beam device and improving resolution.

[0030] The heater 212 is disposed in the second vacuum chamber 106 so as to contact the side surface of the extraction electrode sidewall 210. By heating the heater 212 to 500°C or higher, the heat is transferred to the NEG unit 209 via the extraction electrode sidewall 210, further heating and activating the NEG material 201 inside. The heater 212 is a ceramic heater made of alumina, silicon nitride, boron nitride, or the like. Ceramic heaters are less susceptible to brittle fracture and wire breakage than metal heaters and are therefore suitable for high-temperature heating. The heater 212 has a cylindrical structure, which provides a wide contact area with the extraction electrode sidewall 210, reducing thermal resistance and efficiently transferring heat from the heater 212 to the extraction electrode sidewall 210. Ceramic heaters may constantly emit 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 minimized.

[0031] The NEG unit 209 and the NEG material 201 therein are disposed at different heights relative to the heater 212, with the heater 212 disposed above and the NEG unit 209 and the NEG material 201 disposed below. In other words, if the axial direction in which the electron beam 101 travels is defined as the forward direction and the opposite direction as the rearward direction, the NEG unit 209 and the NEG material 201 are disposed at positions spaced apart in the axial direction relative to the heater 212, with the NEG unit 209 and the NEG material 201 disposed in front and the heater 212 disposed in the rearward direction.

[0032] In this case, by arranging the heater 212, the NEG unit 209, and the NEG material 201 at different heights and overlapping their horizontal positions, the extraction electrode 203 is prevented from becoming larger in the horizontal direction. As a result, the extraction electrode 203 can be made smaller even when the NEG unit 209 is provided. By miniaturizing the extraction electrode 203, the electron gun vacuum vessel 121 and the electron gun 122 are made smaller, improving the resistance of the electron gun 122 to mechanical vibrations and improving the resolution of the charged particle beam device. In addition, the floor area required for installing the charged particle beam device is reduced, resulting in reduced costs. In addition, by arranging the NEG unit 209 and the NEG material 201 at different heights relative to the heater 212, the heater 212 can be made longer in the vertical direction, and the increased contact area of ​​the heater 212 improves the efficiency of heat transfer.

[0033] The heat absorbing plate 250 is disposed opposite the heater 212 and in a position directly facing the heater 212. The heat absorbing plate 250 and the heater 212 are not in contact with each other. The heat absorbing plate 250 is connected to the NEG unit 209. The heat absorbing plate 250 absorbs radiant heat emitted from the heater 212, becomes hot, and transfers this heat to the NEG unit 209, thereby improving the heating efficiency of the NEG material 201. This action is explained using FIG. 3.

[0034] An example of the effect of the heat absorption plate 250 on improving the heating efficiency of the NEG material 201 will be described using FIG. 3 . As shown by the heat conduction path 301, heat generated by the heater 212 is conducted to the NEG unit 209 via the extraction electrode side wall 210. Here, radiant heat 302 is emitted from the heater 212 heated to 500°C or higher. By arranging the heat absorption plate 250 in a position facing the heater 212 so as to directly view the heater 212, the radiant heat 302 is absorbed by the heat absorption plate 250, and the heat absorption plate 250 is heated to a high temperature. According to the Stefan-Boltzmann equation, the amount of radiant heat 302 is proportional to the difference between the fourth power of the temperature of the heater 212 and the fourth power of the temperature of the heat absorption plate 250. As the temperature of the heat absorption plate 250 increases, the radiant heat 302 decreases, and the heater 212 increases in temperature with less power. Since the heat absorption plate 250 is connected to the NEG unit 209 , heat is transferred from the heat absorption plate 250 to the NEG unit 209 as shown by the heat conduction path 303 .

[0035] As a result, heat from the heater 212 is transferred to the NEG unit 209 through two paths, heat conduction path 301 and heat conduction path 303, and the NEG unit 209 is heated efficiently. In other words, the thermal resistance of the heat conduction from the heater 212 to the NEG unit 209 is reduced, and the temperature difference between the heater 212 and the NEG unit 209 is reduced. Alternatively, the reduced thermal resistance allows the heater 212 and the NEG unit 209 to be heated to a high temperature with less power. The heat absorption plate 250 may be assembled and connected to the NEG unit 209 as a separate part, or may be manufactured integrally from the same material.

[0036] Heat is transferred from the NEG unit 209 to the internal NEG material 201 via the paths indicated by the heat radiation path 304 and the heat conduction path 305. As a result, the NEG material 201 is heated to a high temperature and activated, thereby realizing pumping capacity. The NEG material 201 is entirely enclosed and contained within the NEG unit 209, and is not positioned protruding outside the NEG unit 209. Therefore, the entire NEG material 201 is heated uniformly, and no areas are generated that are insufficiently activated due to temperature imbalance. As a result, the pumping speed is maximized. More preferably, all of the NEG material 201 is in thermal contact with the NEG unit 209, minimizing the temperature difference between the NEG material 201 and the NEG unit 209.

[0037] A heat conduction plate 251 may be placed inside the NEG unit 209. Use of the heat conduction plate 251 improves the heating efficiency of the NEG materials 201, and the temperature of the multiple NEG materials 201 becomes uniform. The heat conduction plate 251 is placed in contact with the multiple NEG materials 201. Therefore, heat is transferred between the NEG materials 201, eliminating temperature imbalances, eliminating areas that are underactivated, and maximizing the exhaust speed. The heat conduction plate 251 may be placed in contact with the NEG unit 209. In this case, as shown by heat conduction paths 306 and 307, heat is efficiently transferred from the NEG unit 209 to the NEG materials 201, further reducing the temperature difference between the two.

[0038] In this configuration, the components with the highest temperature during heating are the heater 212, the heat absorption plate 250, the NEG unit 209, and the NEG material 201. Heat during heating is transferred from the component with the highest temperature to the component with the lowest temperature by thermal conduction or thermal radiation.

[0039] The temperature of the NEG material 201 increases when it is placed below the heater 212. As shown by the heat conduction path 308 and the heat radiation paths 309, 310, and 311, heat escapes from the extraction electrode 203 to the outside during heating. The extraction electrode side wall 210 is connected to the electron gun vacuum vessel 121 via the insulator 252. Here, the electron gun vacuum vessel 121 is exposed to the outside air at room temperature, so its temperature is low. Therefore, a large temperature difference occurs between the electron gun vacuum vessel 121 and the heater 212, and the amount of heat of the heat conduction path 308 is greater than that of the heat radiation paths 309, 310, and 311.

[0040] If the NEG material 201 is placed above the heater 212, that is, between the heater 212 and the electron gun vacuum vessel 121, a large amount of heat is absorbed by the electron gun vacuum vessel 121, so the temperature of the NEG material 201 drops rapidly compared to the heater 212, and activation may not be possible. On the other hand, if the NEG material 201 is placed below the heater 212, the only heat absorbed from this position is radiant heat indicated by the heat radiation paths 309 and 311, and the amount of heat is less than that of the heat conduction path 308. As a result, the NEG material 201 is maintained at a high temperature similar to that of the heater 212.

[0041] In addition, by arranging the NEG material 201 below the heater 212, the pressure around the tip 204 can be further reduced. The pressure around the tip 204 is reduced as the exhaust path between the tip 204 and the NEG material 201 is shortened to increase the conductance and the effective pumping speed. The tip 204 is arranged in a position facing the extraction electrode lower part 211, and is arranged below the extraction electrode 203 as a whole. Therefore, by arranging the NEG material 201 below the extraction electrode 203, the distance of the exhaust path to the tip 204 is shortened. Therefore, the NEG unit 209 is connected to the extraction electrode lower part 211, and the heater 212 is arranged above the NEG unit 209, and the effective pumping speed can be improved.

[0042] Furthermore, if the heater 212 is placed below the NEG material 201 while leaving the position of the NEG material 201 unchanged, the distance between the chip 204 and the lower side of the extraction electrode lower part 211 will increase. In this case, the distance between the chip 204 and the electrostatic lens formed in the space where the extraction electrode lower part 211 and the acceleration electrode 113 face each other will increase, increasing aberration and degrading resolution. For this reason, by placing the heater 212 above the NEG material 201 and shortening the distance between the chip 204 and the lower side of the extraction electrode lower part 211, it is possible to minimize the aberration of the electrostatic lens.

[0043] Furthermore, by arranging the NEG material 201 below the heater 212, it becomes easier to mount the wiring 312 for the heater 212. The heater 212 has wiring 312 for electrical heating. The wiring 312 is connected to a feedthrough (not shown) provided on the top surface of the electron gun vacuum vessel 121, and power is supplied from an external power source. This wiring 312 must not come into contact with other electrodes and cause a short circuit. Furthermore, in order to simplify the configuration and miniaturize the electron gun, the length of the wiring 312 must be short. By arranging the NEG material 201 below the heater 212, the distance to the feedthrough is shortened, and the length of the wiring 312 can be shortened. Furthermore, since there is free space above the heater 212 for placing the wiring 312, the configuration of the wiring 312 can be simplified, making it easier to prevent short circuits.

[0044] To summarize the above arrangement of the heater 212 and the NEG material 201, by arranging the heater 212 above and the NEG material 201 below, it is possible to achieve effects such as an increase in the heating temperature of the NEG material 201 and an increase in the effective pumping speed, a reduction in the aberration of the electrostatic lens, and simplification of the wiring 312 of the heater 212, in addition to miniaturization of the electron gun 122. In other words, the above effects are achieved by arranging the heater 212 first and then the NEG material 201 in this order with respect to the traveling direction in which the electron beam 101 is emitted.

[0045] By keeping the heat absorption plate 250 and the heater 212 out of contact, it is possible to heat the heater 212 and the NEG material 201 to a high temperature with little power. As shown by the heat radiation path 310, radiant heat escapes to the outside from the heat absorption plate 250. If the heat absorption plate 250 is in contact with the heater 212 and heated to the same high temperature, the radiant heat from the heat radiation path 310 increases, and the power required for heating increases.

[0046] However, by making the heat absorption plate 250 and heater 212 non-contact, the temperature of the heat absorption plate 250 becomes slightly lower than that of the heater 212, and the radiant heat of the heat radiation path 310 decreases in proportion to the fourth power of that. As a result, the amount of heat escaping to the outside decreases, and heating to a high temperature is possible with less power. In addition, the heater 212 is a ceramic heater, and its dimensional precision is not good. For this reason, it is difficult to assemble the heater 212 so that both the inner and outer surfaces are in contact with other electrodes. Making the heat absorption plate 250 and heater 212 non-contact facilitates assembly.

[0047] Another function of the heat absorption plate 250 is to prevent the heater 212 from becoming charged. As shown in FIG. 2 , when the electron beam 101 collides with the aperture 215 or the acceleration electrode 113, reflected electrons are emitted from these and scattered inside the second vacuum chamber 106. The heater 212 is made of ceramic and becomes charged when the reflected electrons collide with it. The charged heater 212 forms an unintended potential distribution and bends the trajectory of the electron beam 101. This can result in reduced resolution due to off-axis aberrations or in the electron beam 101 not reaching the sample 102 due to trajectory deviation. In addition, as the heater 212 becomes increasingly charged, discharge occurs between the heater 212 and the surrounding electrodes. This results in voltage fluctuations, which can cause problems such as melting of the tip 204 or destruction of the electrodes.

[0048] However, by arranging a metal heat absorbing plate 250 opposite the heater 212 as in the present invention, collision of reflected electrons with the heater 212 is prevented, and charging is prevented. Because the heat absorbing plate 250 is made of metal, it does not itself become charged. In addition, by further reflecting reflected electrons from its surface, the reflected electrons are kept away from the heater 212, thereby reducing the chance of collision. The upper end of the heat absorbing plate 250 is higher than the upper end of the heater 212, preventing reflected electrons from reaching the heater 212. As a result, charging of the heater 212 is prevented, and deviation of the electron beam trajectory and discharge are prevented.

[0049] An example of the configuration of the NEG material 201 inside the NEG unit 209 will be described using FIG. 8. FIG. 8 is an enlarged perspective view of a portion of the NEG material 201. The NEG material 201 is preferably made of sintered porous bulk material, and multiple pieces are arranged inside the NEG unit 209. By using multiple NEG materials 201, the surface area of ​​the NEG material facing the vacuum increases compared to when a single NEG material with the same total volume is arranged. This increases the surface area that adsorbs gas, improving the pumping speed. In addition, sintered NEG material has a large effective surface area because its surface has micrometer-order irregularities. Therefore, it has a higher pumping speed and can reduce pressure more than NEG material with a smooth surface.

[0050] The NEG materials 201 have a cylindrical structure and are closely arranged with their sides in contact with each other, thereby increasing the number of NEG materials mounted within the NEG unit 209. The areas where the NEG materials 201 contact each other are not exposed to the vacuum and do not contribute to vacuum evacuation. However, by giving the NEG materials 201 a cylindrical structure and having the circles contact each other, the contact area is minimized. As a result, the total area of ​​the NEG materials 201 exposed to the vacuum increases, maximizing the evacuation speed. The more NEG materials 201 are used, the higher the total evacuation speed. The NEG materials 201 may be stacked in two or more rows in the height direction, or arranged in two or more rows in the radial direction. Note that the radial direction described in FIG. 8 corresponds to the horizontal direction in FIG. 2. The NEG materials 201 may have a spherical structure or a three-dimensional structure with curved sides. In this case, the area where the NEG materials 201 contact each other is minimized.

[0051] When a porous sintered body is used for the NEG material 201, its poor thermal conductivity can cause temperature differences between multiple NEG materials 201 or within a single NEG material 201, resulting in some parts that cannot be activated. However, using a thermally conductive plate 251 equalizes the temperature difference, making it easier to activate the entire material. When using a thermally conductive plate 251, NEG materials 201 may be placed above and below the thermally conductive plate 251, as shown by the upper NEG material 802 and the lower NEG material 803. The width of the thermally conductive plate 251 is narrower than the diameter of the NEG material 201, exposing part of the lower surface of the upper NEG material 802 and the upper surface of the lower NEG material 803 to the vacuum. As a result, the surface area contributing to exhaust increases, improving the exhaust speed.

[0052] By having the upper-level NEG material 802 and the lower-level NEG material 803 in contact with the same heat conduction plate 251, even when the NEG material 201 is arranged in multiple levels in the height direction, differences in temperature between the levels are prevented. As a result, the entire NEG material 201 is heated and activated uniformly. In addition to the upper-level NEG material 802 and the lower-level NEG material 803, the NEG material 804 or NEG material 805 in the circumferential direction is also brought into contact with the heat conduction plate 251, so that at least three or more pieces are in contact. As a result, the temperature is uniform in both the height direction and the circumferential direction.

[0053] A plurality of heat conduction plates 251 are arranged periodically in the circumferential direction, and more preferably, all of the NEG materials 201 are brought into contact with one of the heat conduction plates 251. As a result, the temperature of all of the NEG materials 201 in the NEG unit 209 is made uniform. Even when the NEG materials 201 are arranged in multiple rows in the radial direction, a heat conduction plate 251 is provided between the rows, and the NEG materials 201 in different rows are brought into contact with the same heat conduction plate 251, thereby preventing temperature deviation due to the rows.

[0054] The thermal conduction plate 251 may have an opening 801. By providing the opening 801, the surface of the NEG material 201 that is exposed to the vacuum without contacting the thermal conduction plate 251 increases. As a result, the exhaust speed improves. By using the thermal conduction plate 251, it is possible to achieve both a uniform heating temperature of the NEG material 201 and an improved exhaust speed due to the increased exposed area.

[0055] Generally, when NEG material is repeatedly exposed to the atmosphere and activated, adsorbed substances diffuse and accumulate inside, reducing the pumping speed and shortening its lifespan. However, bulk NEG material with a three-dimensional structure has sufficient volume, so there is a large capacity for adsorbed substances to diffuse inside. This results in a long lifespan despite repeated activation. Using sintered bulk material for the NEG material 201 not only improves the pumping speed but also extends the lifespan.

[0056] FIG. 4 illustrates an example of how the emissivity of the outer surface 401 of the extraction electrode 203 improves the heating efficiency of the NEG material 201. As shown by the heat radiation paths 309, 310, and 311, heat escapes from the extraction electrode 203 to the outside. By lowering the emissivity of the outer surface of the extraction electrode 203, the radiant heat is reduced, allowing the heater 212 and the NEG material 201 to be heated to a high temperature with lower power. Therefore, the outer surfaces 401 of the heat absorption plate 250, the NEG unit 209, and the extraction electrode lower portion 211 are polished to a surface roughness Ra of 1 μm or less using electrolytic composite polishing or the like, and the emissivity is set to 0.3 or less, more preferably 0.1 or less. Alternatively, a metal with a low emissivity different from the base material of the electrode, such as gold, silver, copper, aluminum, or titanium nitride, may be deposited on the outer surface 401.

[0057] Additionally, the higher the emissivity of the inner surface 402 of the heat absorption plate 250, the more it absorbs the radiant heat 302 emitted from the heater 212. As a result, the temperature of the heat absorption plate 250 increases, and the temperature of the NEG material 201 also increases. Therefore, the surface roughness of the inner surface 402 is set to be greater than Ra = 1 μm, and the emissivity is set to be 0.3 or greater. Furthermore, a film of a material with a high emissivity different from the base material of the electrode, such as carbon, its compounds, or metal oxides, may be formed on the inner surface 402.

[0058] 4 can be summarized in another way as follows: by making the emissivity of the outer surface of the heat absorption plate 250 lower than that of the inner surface, the heating efficiency of the NEG material 201 is improved. In other words, by making the emissivity of the inner side of the heat absorption plate 250 facing the heater 212 higher than that of the opposite outer side, the NEG material 201 can be heated to a high temperature with less power. In other words, by making the surface roughness of the inner side of the heat absorption plate 250 greater than that of the opposite outer side, the NEG material 201 can be heated to a high temperature with less power. In other words, by exposing different materials to the inner and outer surfaces of the heat absorption plate 250 and making the emissivity of the inner side higher than that of the outer side, the NEG material 201 can be heated to a high temperature with less power.

[0059] In a configuration in which the pressure around the first vacuum chamber 105 and the electron source (charged particle source) is efficiently reduced by disposing the NEG material 201 inside the extraction electrode 203 as in the present invention, it is necessary to provide a space around the NEG material 201 to improve conductance and increase the effective pumping speed. On the other hand, providing a space around the NEG material 201 narrows the path of heat conduction to the NEG material 201, making it difficult for heat to be transferred, lowering the heating temperature of the NEG material 201, and there is a possibility that the NEG material 201 will not be activated and the pumping speed will decrease. In other words, in a configuration in which the NEG material 201 is disposed inside the extraction electrode 203, there is a trade-off between improving the effective pumping speed of the NEG and improving its activation temperature. In particular, when the NEG material 201 is a bulk material with a three-dimensional structure, a temperature distribution occurs within the three-dimensional structure of the NEG material 201, and some parts may not be activated due to a lack of temperature rise, resulting in a decrease in pumping capacity.

[0060] However, by utilizing radiant heat using the heat absorption plate 250 as in the present invention, the heating efficiency of the NEG material 201 is improved, and the heating temperature of the NEG material 201 becomes sufficiently high to activate it. In other words, the thermal resistance between the heater 212 and the NEG material 201 is reduced, reducing the temperature difference between them and improving the heating efficiency. In other words, the NEG material 201 can be heated to a high temperature even with less power supplied to the heater 212. In addition, by surrounding the NEG material 201 using the NEG unit 209 and the heat conduction plate 251 and transferring heat uniformly, there is no temperature bias inside the NEG material 201, and the entire material is activated uniformly, maximizing the exhaust speed.

[0061] Furthermore, by arranging the heater 212 and the NEG material 201 at different heights, with the heater 212 at the top and the NEG material 201 at the bottom, the electron gun 122 can be made smaller and the heating temperature and effective pumping speed of the NEG material 201 can be improved. In other words, by arranging the heater 212 first and then the NEG material 201 in this order with respect to the traveling direction of the emitted electron beam 101, the electron gun 122 can be made smaller and the heating temperature and effective pumping speed of the NEG material 201 can be improved. As a result of the above configuration, the NEG material 201 is activated at a sufficiently high temperature, thereby efficiently reducing the pressure around the electron source (charged particle source), providing a stable electron beam and providing a compact electron gun and charged particle beam device.

[0062] An example of the effect of the heat absorption plate 250 in improving the heating efficiency of the NEG material 201 will be described using FIG. 5 . FIG. 5 shows the temperature of the NEG material 201 versus the input power of the heater 212. Note that the power is normalized to 1, which is the power at which the NEG material 201 reaches 500°C when the heat absorption plate 250 is present. By providing the heat absorption plate 250, heat is more easily transferred from the heater 212 to the NEG material 201, and the amount of heat escaping from the extraction electrode 203 to the outside is reduced. As a result, the temperature of the NEG material 201 is higher even with the same power compared to when the heat absorption plate 250 is not present. Therefore, the NEG material 201 is sufficiently activated, the exhaust speed is improved, and the pressure in the first vacuum chamber 105 is reduced.

[0063] Even without the heat absorption plate 250, the NEG material 201 can be heated up to 500°C by increasing the heater power. However, in this case, the temperatures of the heater 212 and the extraction electrode 203 become excessively high, causing distortion of the electrodes and evaporation of the low-melting-point material. As a result, the electrode distortion makes it impossible to remove and reassemble the extraction electrode 203, making it impossible to replace the CFE electron source 202 or the NEG unit 209. Furthermore, the evaporation of the low-melting-point material causes the evaporated metal to be deposited on insulators, etc., causing discharge and making the electron gun 122 unusable. Therefore, these problems can be prevented by heating the NEG material 201 to a high temperature with low power without excessively heating the heater 212 and the extraction electrode 203, as in the present invention.

[0064] An example of the effect of the heat absorption plate 250 in stabilizing the electron beam current will be described with reference to Fig. 6. Fig. 6 shows the stabilization time of the electron beam versus the pressure in the second vacuum chamber 106. The stabilization time is measured when the pressure in the second vacuum chamber 106 is 1 x 10 without the heat absorption plate 250. －９ The stabilization time at 1 Pa was normalized as 1. NEG activation occurs when the adsorbed substances on the NEG surface diffuse into the interior, creating a clean surface. The diffusion rate of adsorbed substances increases exponentially with temperature, and a few percent increase in heating temperature increases the diffusion rate several times. Therefore, even a slight increase in the NEG heating temperature can significantly change the pumping speed.

[0065] In the present invention, the heat absorption plate 250 is provided to increase the heating temperature of the NEG material 201, thereby sufficiently activating it and thereby improving the pumping speed of the NEG material 201. As a result, even if the pressure in the second vacuum chamber 106 is the same, the pressure in the first vacuum chamber 105 is reduced compared to when the heat absorption plate 250 is not provided, and the stabilization time of the electron beam emitted from the CFE electron source 202 is improved. In addition, by providing the heat absorption plate 250, the pressure in the second vacuum chamber 106 required to obtain the same stabilization time can be increased. This makes it possible to reduce the size or power consumption of the auxiliary NEG pump 112 and the ion pump 111, thereby enabling the size and cost reduction of the charged particle beam device.

[0066] In the first embodiment, a configuration has been described in which the heating efficiency of the NEG material 201 is improved and activated using a heat absorption plate 250. In the second embodiment, a configuration including a heat reflection plate 701 will be described. 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 will be used for similar configurations and functions, and the description thereof will be omitted.

[0067] An example of how a heat reflector 701 improves the heating efficiency of the NEG material 201 will be described with reference to FIG. 7 . In this embodiment, the heat reflector 701 is disposed in the second vacuum chamber 106 so as to surround the extraction electrode 203. The heat reflector 701 is made of stainless steel, titanium, permalloy, or the like, and is connected to the electron gun vacuum vessel 121 via an insulator 252. The heat reflector 701 has an opening 704 at the bottom center, and the electron beam 101 emitted from the CFE electron source 202 passes through this opening 704 and proceeds to the acceleration electrode 113 and aperture 215 below. The heat reflector 701 is electrically connected to the extraction power supply 109, and an extraction voltage is applied to it. Note that the voltage applied to the heat reflector 701 may be any other voltage.

[0068] As shown by the heat radiation paths 309, 310, and 311, radiant heat escapes from the extraction electrode 203 toward the outside during heating. Without the heat reflector 701, the extraction electrode 203 faces the electron gun vacuum vessel 121, which is exposed to the ambient air at room temperature and has a low temperature. Here, since radiant heat is proportional to the difference between the fourth powers of the temperatures of the opposing objects, the radiant heat from the heat radiation paths 310 and 311 becomes relatively large, and a large amount of heat is taken away from the extraction electrode 203. On the other hand, by providing the heat reflector 701 in a position surrounding the extraction electrode 203 as in this embodiment, the extraction electrode 203 and the heat reflector 701 face each other. The temperature of the heat reflector 701 becomes intermediate between the temperatures of the extraction electrode 203 and the electron gun vacuum vessel 121, and the radiant heat shown by the heat radiation paths 310 and 311 is reduced. As a result, the amount of heat escaping from the extraction electrode 203 is reduced, and the NEG material 201 can be heated to a high temperature even if the input power of the heater 212 is reduced.

[0069] The surface of the heat reflector 701 is subjected to electrolytic composite polishing or the like to achieve a surface roughness Ra of 1 μm or less and an emissivity of 0.3 or less, preferably 0.1 or less. Alternatively, a metal with a low emissivity different from the base material of the heat reflector, such as gold, silver, copper, aluminum, or titanium nitride, may be deposited. By reducing the emissivity of the inner surface of the heat reflector 701, the radiant heat emitted from the extraction electrode 203 is less likely to be absorbed by the heat reflector 701, thereby reducing the amount of heat in the heat radiation paths 310 and 311. As a result, the NEG material 201 can be heated to a high temperature with less power. Furthermore, by reducing the emissivity of the outer surface of the heat reflector 701, the radiant heat transmitted from the heat reflector 701 to the electron gun vacuum vessel 121, as indicated by the heat radiation path 703, is reduced. As a result, the temperature of the heat reflector 701 increases, further reducing the radiant heat indicated by the heat radiation paths 310 and 311. As a result, the NEG material 201 can be heated to a high temperature even if the input power of the heater 212 is further reduced.

[0070] Since the lower surface of the extraction electrode 203 faces the acceleration electrode 113, heat shown by the heat radiation path 309 escapes from the extraction electrode 203. Therefore, a second heater 702 may be provided on the acceleration electrode 113. The second heater 702 is a ceramic heater and is placed in contact with the acceleration electrode 113. The second heater 702 is also placed in the third vacuum chamber 107, so that even if steady degassing occurs, the pressure in the second vacuum chamber 106 is not deteriorated. The second heater 702 is heated at the same time as the heater 212, and the acceleration electrode 113 and the aperture 215 are heated to approximately 500°C. As a result, the temperature difference between the extraction electrode 203 and the acceleration electrode 113 is reduced, and the radiant heat along the heat radiation path 309 is reduced. Therefore, the amount of heat escaping from the extraction electrode 203 is reduced, and the NEG material 201 can be heated to a high temperature even with a further reduction in the input power of the heater 212. In addition, by heating the acceleration electrode 113 and the aperture 215, the amount of electron stimulated desorption gas emitted when the electron beam 101 collides with them is reduced, thereby preventing the pressure in the second vacuum chamber 106 from deteriorating.

[0071] The above describes several embodiments of the present invention. However, the present invention is not limited to the above embodiments, and modifications of the components may be made without departing from the spirit and scope of the invention. For example, instead of a tungsten single crystal, a low work function material such as CeB6 or LaB6, or a surface-inactive material such as a carbon-coated material, may be used for the tip 204. Furthermore, a nanowire electron source or a single-atom electron source having a sharpened tip radius of curvature of several tens of nanometers or several to one atom may also be used. Furthermore, the charged particle source to which the present invention can be applied is not limited to a CFE electron source, but can also be applied to a Schottky electron source or an ion source. In particular, a gas field ionization ion source is an example of an 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, ions can be emitted as a charged particle beam from the tip 204, even if the device configuration is otherwise approximately the same. Furthermore, in order to obtain a stable emission current from a Schottky electron source, a 1×10 －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.

[0072] 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, 1 17...detector, 118...turbomolecular pump, 119...objective lens, 120...piping, 121...electron gun vacuum vessel, 122...electron gun, 123...suppressor, 124...suppressor power supply, 201...NEG material, 202...CFE electron source, 203...extraction electrode, 204...tip, 205...filament, 206...pin, 207...insulator, 208...holding portion, 209...NEG unit 210... side wall of extraction electrode, 211... lower part of extraction electrode, 212... heater, 213... differential exhaust port, 214... aperture, 215... aperture, 216... opening, 250... heat absorption plate, 251... heat conduction plate, 252... insulator, 301... heat conduction path, 302... radiant heat, 303... heat conduction path, 304... heat radiation path, 305... heat conduction path, 306... heat conduction path, 307... heat conduction path, 30 8...heat conduction path, 309...heat radiation path, 310...heat radiation path, 311...heat radiation path, 312...wiring, 401...outer surface, 402...inner surface, 701...heat reflector, 702...second heater, 703...heat radiation path, 704...opening, 801...opening, 802...upper NEG material, 803...lower NEG material, 804...circumferential NEG material, 805...circumferential NEG material.

Claims

1. A charged particle beam device comprising: a charged particle source having a single crystal needle, a filament connected to the single crystal needle, and an insulator holding the filament; a non-evaporable getter material; an extraction electrode; a first vacuum chamber inside the extraction electrode in which the charged particle source and the non-evaporable getter material are arranged; a heater for heating the non-evaporable getter material; a second vacuum chamber in which the heater and the extraction electrode are arranged and which has a higher pressure than the first vacuum chamber; and a heat absorption plate connected to the extraction electrode and arranged opposite the heater, wherein the heater and the non-evaporable getter material are arranged in that order in the direction in which a charged particle beam is emitted from the charged particle source, and the non-evaporable getter material is arranged in the first vacuum chamber, and the heater is arranged in the second vacuum chamber.

2. The charged particle beam device according to claim 1, characterized in that the extraction electrode comprises a heat-conducting container having an opening on the side of the first vacuum chamber, and the heat-conducting container comprises a plurality of the non-evaporable getter materials therein.

3. A charged particle beam device according to claim 2, characterized in that the heat absorbing plate is connected to the heat conducting container.

4. The charged particle beam device according to claim 3, wherein the temperature of said heat absorbing plate is higher than the temperature of said non-evaporable getter material when said heater is heating.

5. The charged particle beam device according to claim 3, wherein the non-evaporable getter material is a sintered body having a three-dimensional structure.

6. The charged particle beam device according to claim 5, wherein the non-evaporable getter material has a curved side surface, and a plurality of the non-evaporable getter materials are in contact with each other at the side surface.

7. The charged particle beam device according to claim 2, characterized in that the thermally conductive container has a thermally conductive plate therein, the thermally conductive plate being in contact with at least three or more of the non-evaporable getter materials.

8. The charged particle beam device according to claim 7, wherein the thermally conductive plate is provided with an opening.

9. The charged particle beam device according to claim 1, characterized in that the heater is made of ceramic, and the heat absorbing plate is a member that prevents reflective particles generated by the charged particle beam from colliding with the heater.

10. A charged particle beam device according to claim 1, characterized in that the emissivity of the inner surface of the heat absorbing plate facing the heater is higher than the emissivity of the outer surface.

11. The charged particle beam device according to claim 10, wherein the surface roughness of the inner surface of the heat absorbing plate is greater than the surface roughness of the outer surface.

12. The charged particle beam device according to claim 11, wherein the inner and outer surfaces of the heat absorbing plate are made of different materials.

13. The charged particle beam device according to claim 1, further comprising a heat reflector disposed in the second vacuum chamber, the heat reflector being disposed so as to surround the extraction electrode.

14. The charged particle beam device according to claim 1, further comprising an acceleration electrode disposed opposite said extraction electrode, said acceleration electrode being provided with a second heater.

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