Sample inspection system

Abstract

To make a magnetic field passing through a vent hole provided in a magnetic shield for shielding an external magnetic field that may influence a sample inspection system, be smaller as much as possible.SOLUTION: Proposed is a sample inspection system comprising: a charged particle beam device for irradiating a sample with a charged particle beam to acquire an image of the sample; a total controller for controlling the charged particle beam device; a magnetic shield for configuring an internal space for housing the charged particle beam device and the total controller and shielding a magnetic field from the outside; and an air cooling device for taking air inside the magnetic shield to cool the internal space of the magnetic shield. The magnetic shield includes one or more high conductivity material layers and one or more high permeability material layers, respectively. The magnetic shield has an air vent hole for cooling at each of the high conductivity material layer and the high permeability material layer. The sample inspection system has a gap, a spatial vacancy, between the high conductivity material layer and the high permeability material layer, where the air vent hole exists.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sample inspection system. [Background technology]

[0002] In recent years, electronic devices have rapidly evolved, and semiconductor devices have become an important component of such devices. The miniaturization of semiconductor devices has significantly contributed to the development of electronic devices by achieving higher performance and functionality. As semiconductors continue to shrink, semiconductor inspection tools, such as CD-SEMs (semiconductor-device-based scanning electron microscopes), are now required to inspect circuit patterns on wafers at 5-nm resolution. This demands ever-fineered measurement resolution. In semiconductor factories where scanning electron microscopes are installed, wafer handling robots patrol nearby equipment, and nearby equipment includes semiconductor etchers equipped with high-power microwave sources and exposure machines equipped with large ultraviolet lasers. Scanning electron microscopes use electron beams to inspect fine patterns. However, in such environments, the electron beams are subject to disturbances from external magnetic fields, resulting in image degradation.

[0003] Previously, magnetic fields that degrade images were geomagnetic DC of around 30 μT, but in recent years, with the advancement of automation, they have expanded to include high-frequency magnetic fields of around 10 kHz, such as those generated by servo motors in wafer transport robots. To prevent these magnetic fields in the frequency range from DC to 10 kHz from affecting scanning electron microscopes, studies have been conducted to create a structure in which the exterior of the device is shielded with a magnetic shield.

[0004] Furthermore, in order to improve the resolution of a scanning electron microscope, problems such as shifts in the field of view due to temperature increases also become an issue. Therefore, cooling the device to reduce temperature fluctuations is important. While localized cooling is performed using water cooling, cooling to maintain a constant temperature for the entire device is performed using air cooling, which exchanges large amounts of air throughout the device. For this air cooling, vents are provided in the magnetic shield surrounding the outside of the device to allow air to pass through.

[0005] Regarding the magnetic shield surrounding the outside of the device, for example, Patent Document 1 discloses a magnetic shield with a multilayer structure made of a highly conductive material layer and a magnetic material. Also, Patent Document 2 discloses a magnetic shield that has a method of providing vents in the magnetic shield by sandwiching a honeycomb structural material between two layers of magnetic shield plates with vents to allow air to flow. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-288328 [Patent Document 2] Japanese Patent Application Publication No. 8-186392 Summary of the Invention [Problem to be solved by the invention]

[0007] It has become clear that the magnetic shield has a vent hole to allow air to flow through it, which allows external magnetic fields to penetrate into the device. Therefore, it is desirable to provide an inexpensive magnetic shield that can reduce the magnetic field that passes through the vent hole.

[0008] However, Patent Document 1 does not consider the effects of magnetic field leakage due to cooling vents in the magnetic shield. Furthermore, according to the magnetic shield disclosed in Patent Document 2, air flows between the inside and outside of the magnetic shield through the vents, but there is no description of the size of the holes, the thickness of the honeycomb structural material, the materials of the two-layer magnetic shield, or the effect of reducing the magnetic field passing through the vents, so it is unclear whether the magnetic shield is effective.

[0009] In view of such circumstances, the present disclosure proposes a technique for minimizing the magnetic field passing through a vent provided in a magnetic shield that blocks external magnetic fields that affect a sample inspection system. [Means for solving the problem]

[0010] In order to solve the above problems, the present disclosure provides a charged particle beam device that irradiates a sample with a charged particle beam to acquire an image of the sample, an overall control device that controls the charged particle beam device, a magnetic shield that defines an internal space for accommodating the charged particle beam device and the overall control device and that shields from external magnetic fields, and an air cooling device that takes air into the magnetic shield to cool the internal space of the magnetic shield, the magnetic shield includes one or more layers of a highly conductive material and one or more layers of a highly magnetically permeable material; We propose a sample inspection system in which the magnetic shield has air vents for cooling in each of the highly conductive material layer and the highly permeable material layer, and has a spatial gap between the highly conductive material layer and the highly permeable material layer in the area where the vents are located.

[0011] Further features related to the present disclosure will become apparent from the description and accompanying drawings of this specification, and aspects of the present disclosure may be realized and realized by the elements and combinations of various elements and aspects set forth in the following detailed description and the appended claims. The descriptions herein are exemplary and illustrative only and are not intended to limit the scope or application of the present disclosure in any way. [Effects of the Invention]

[0012] According to the technology of the present disclosure, the penetration of magnetic fields into the magnetic shield is reduced, making it possible to obtain clear images with little influence of external magnetic fields on the charged particle beam. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing an example of a cross-sectional configuration of a wafer inspection device using a scanning electron microscope (charged particle beam device) according to a first embodiment of the present disclosure. [Figure 2] 3 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 near a vent hole 305 according to the present embodiment. FIG. [Figure 3] 3 is a diagram showing an example of a cross-sectional configuration of a magnetic shield in an experiment, simulating the example configuration of FIG. 2. FIG. [Figure 4] FIG. 1 is a diagram showing an example of a top view configuration of a magnetic field calculation system (configuration). [Figure 5] 10 is a graph showing the results of calculating a magnetic field generated at a magnetic field calculation point by changing only the frequency while keeping the amplitude of the current flowing through the magnetic field generating coil constant. [Figure 6] 10 is a graph showing how the hole diameter of the vent and the size of the gap affect the magnetic field that passes through. [Figure 7] FIG. 10 is a diagram showing an example of a cross-sectional configuration of a magnetic shield (comparative example) 300′ made by a known technique. [Figure 8] FIG. 10 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a second embodiment of the present disclosure. [Figure 9] FIG. 10 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a third embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a fourth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present disclosure relates to a magnetic shield that houses a charged particle beam device (scanning electron microscope) and a computer that controls the device, which constitute a sample inspection system (semiconductor inspection system) that inspects samples (wafers) used in electronic devices. More specifically, this embodiment relates to a magnetic shield that includes a first magnetic shield section having multiple vents and a second magnetic shield section that does not have vents, and has a gap between a highly conductive material layer and a highly permeable material layer that constitute the first magnetic shield section.

[0015] Hereinafter, embodiments and examples of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show specific embodiments and implementation examples in accordance with the principles of the present disclosure, but these are intended to aid in understanding the present disclosure and are by no means to be used to interpret the present disclosure in a limiting manner.

[0016] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0017] Example 1 (i) Example of wafer inspection device configuration 1 is a diagram showing an example of a cross-sectional configuration of a wafer inspection device using a scanning electron microscope (charged particle beam device) according to Example 1 of the present disclosure. Note that although a scanning electron microscope is described in this example, the same effect can be obtained with other inspection devices such as a length measurement scanning electron microscope, a scanning electron microscope with a defect review function, and other inspection devices that are affected by magnetic fields.

[0018] In FIG. 1, a primary electron beam (charged particle beam) 100 generated by an electron gun 1 is formed into a thin beam by a condenser lens 3 and an aperture 2. The formed beam is deflected by a scanning deflector 4, and further focused by an objective lens 5, and then irradiated onto the surface of a wafer 6, which is the object of observation. At the wafer surface, a holder voltage (negative voltage) 57 is applied to a holder 7 (to facilitate the emission of secondary electrons), causing secondary electrons 101 to be emitted. The secondary electrons are deflected by a secondary electron extraction deflector 11 and input to a detector 12. The detector 12 converts the secondary electrons into an electrical signal, which is supplied as detector data 59 to an image acquisition device 25, where an image is generated.

[0019] An overall control device 20 that controls the entire apparatus supplies an optical system command 51, which is the setting conditions of the optical system, to an optical system control device 21. Based on the command value of the optical system command 51, the optical system control device 21 inputs an electron gun command 53 to the electron gun 1, a condenser lens command 54 to the condenser lens 3, a scanning deflector command 55 to the scanning deflector 4, an objective lens command 56 to the objective lens 5, and a holder voltage 57 to the holder 7. A table 9 is installed on the top of the stages (X stage 30 and Y stage 31). The holder 7, on which the wafer 6 is placed, is installed on the table 9 with an electrical insulator 8 sandwiched therebetween, and a negative voltage is applied to it.

[0020] The stage for moving the position of the wafer 6 is placed inside a vacuum chamber 200 located below the optical system of the apparatus. The stage is equipped with a multi-axis stage that can move in translational directions along at least two or more axes. In this embodiment, it has two horizontal axes: stage 30 (X-axis direction) and stage 31 (Y-axis direction). In addition to the X-stage 30 and Y-stage 31, it may also have a Z-stage that moves the wafer 6 in the Z direction (the up and down direction in FIG. 1).

[0021] The overall control device 20 supplies a stage position command 50, such as target position information for each stage, to the stage control device 22. Based on the command value of the stage position command 50, the stage control device 22 supplies a stage drive current 61 for driving each stage to the two-axis stage to control the position of the table.

[0022] In scanning electron microscopes, the trajectory of electron beams, in particular, is bent when an external magnetic field is applied, degrading images. Furthermore, other control systems also suffer from electromagnetic noise due to the effects of magnetic and electric fields generated by AC magnetic fields, degrading images. To prevent this, in this embodiment, a magnetic shield 300 is installed around the periphery of the device to shield against magnetism. The magnetic shield 300 is composed of two or more layers: an outer highly conductive material layer 301 made of aluminum or copper alloy, etc., and an inner highly permeable material layer 302 made of permalloy or pure iron, etc. In this embodiment, a two-layer structure is shown, with one highly conductive material layer 301 and one highly permeable material layer 302. However, more layers may be used to further reduce magnetic field penetration. However, it is important that the outermost layer be the highly conductive material layer 301 in order to reduce high-frequency magnetic fields. This is because, when an AC magnetic field penetrates from outside the device, if the outermost layer is made of a highly conductive material, eddy currents will flow, which will have the effect of reflecting the AC magnetic field, while if the outermost layer is made of a highly permeable material, it will have the effect of absorbing the magnetic field, resulting in a larger magnetic field passing through the magnetic shield.In the case of a DC magnetic field, highly conductive materials do not have a magnetic field shielding effect, so there is no difference in effectiveness regardless of the outermost layer.

[0023] Numerous vents 305 for air flow are provided at the top and bottom of the magnetic shield 300. The vents 305 are configured so that vents 305a in the highly conductive material layer 301 and vents 305b in the highly magnetically permeable material layer 302 face each other. Air 309 flows between vents 305a and 305b in the direction indicated by the arrows. A ventilation unit 310 is installed above the vents 305 at the top of the device to force a large flow of air. The highly conductive material layer 301 and the highly magnetically permeable material layer 302 are fixed with bolts to a rigid frame 320 made of stainless steel or the like (the frame is composed of multiple sub-frames extending vertically and horizontally relative to the plane of FIG. 1 ).

[0024] In this embodiment, the air 309 forms a downflow from top to bottom, but if the airflow direction of the ventilation unit 310 is reversed, it is also possible to blow air from bottom to top, and by locating the air vents 305 on the left and right sides of the device instead of the top and bottom, it is also possible to blow air horizontally with the same configuration.

[0025] In addition to the vent 305, the magnetic shield 300 also has holes for transporting wafers for inspection, but the vent 305 accounts for the largest proportion of the total area, and the challenge is to prevent the magnetic field from passing through this hole and entering the magnetic shield 300. Below, a method for suppressing the magnetic field from passing through the vent 305 and entering the magnetic shield 300 in this embodiment will be described.

[0026] (ii) Configuration example of magnetic shield 300 FIG. 2 is a diagram showing an example of a cross-sectional configuration of magnetic shield 300 near ventilation hole 305 according to this embodiment. The outer side of magnetic shield 300 is made of high-conductivity material layer 301 and has ventilation hole 305a. The inner side of magnetic shield 300 is made of high-permeability material layer 302 and has ventilation hole 305b. A characteristic feature of this embodiment is that only the portion of high-conductivity material layer 301 having ventilation hole 305a is made of a separate plate (separate member), and only this portion is separated from high-permeability material layer 302 by gap 304, with each layer being fixed to frame 320 with bolts 330. Alternatively, only the portion of high-permeability material layer 302 having ventilation hole 305b may be made of a separate plate (separate member), and the separate plate (separate member) may be placed below high-permeability material layer 302 without ventilation hole 305b, and fixed to frame 320 with bolts 330 to form a gap. Furthermore, the thickness of the highly conductive material layer 301 and the thickness of the highly magnetically permeable material layer 302 may be the same or different. For example, the highly conductive material layer 301 may be configured to be thicker than the highly magnetically permeable material layer 302, and the highly magnetically permeable material layer 302 may be configured to be thicker than the highly conductive material layer 301.

[0027] (iii) Consideration of the optimal size of the gap 304 To optimize the size of the gap 304, the following magnetic field calculations (experiments) were performed. The system used for the magnetic field calculations (experimental configuration) is explained in Figures 3 and 4. Figure 3 shows an example of a cross-sectional configuration of a magnetic shield from an experiment, simulating the configuration example shown in Figure 2. In Figure 3, the upper layer is a highly conductive material layer 301, which is made of aluminum alloy A5052 in the calculations (experiments). The lower layer is a highly permeable material layer 302, made of permalloy PC. The highly conductive material layer 301 has a vent 305a. The highly permeable material layer 302 has a vent 305b. Both vents 305a and 305b have the same diameter. A gap 304 is located between the highly conductive material layer 301 and the highly permeable material layer 302. A magnetic field generating coil 400 with a diameter of 40 mm is placed 10 mm above the highly conductive material layer 301. Furthermore, a variable frequency AC power supply 401 is connected to the magnetic field generating coil 400 to pass a current through the coil 400. A position on the central axis of the magnetic field generating coil 400, 20 mm below the high permeability material layer 302, was set as the magnetic field calculation point 402, and the magnetic field at that position was calculated to estimate the magnitude of the magnetic field passing through the vent hole.

[0028] Figure 4 shows an example of a top-view configuration of the magnetic field calculation system (configuration). The vent holes 305a in the highly conductive material layer 301 and the vent holes 305b in the highly magnetically permeable material layer 302 have the same diameter and are arranged in the same position (their centers are aligned) when viewed from above. The pitch between the holes (the distance between the centers of the vent holes) is twice the diameter of the vent holes. Furthermore, the vent holes are arranged to fill an area of ​​100 mm x 100 mm.

[0029] Hereinafter, with reference to FIGS. 5 and 6, the results of evaluating the magnetic field passing through the vent hole in the system described with reference to FIGS. 3 and 4 will be described.

[0030] FIG. 5 is a graph showing the results of calculating the magnetic field generated at the magnetic field calculation point by changing only the frequency while keeping the amplitude of the current flowing through the magnetic field generating coil constant. In the graph of FIG. 5, the horizontal axis represents the logarithm of the frequency (log 10The vertical axis represents the amplitude of the calculated magnetic flux density (frequency). Here, the system (configuration) of magnetic shield 300 used for magnetic field calculations was a configuration in which the thickness of the permalloy PC in high permeability material layer 302 was 0.8 mm, the thickness of the A5052 in high conductivity material layer 301 was 0.8 mm and 2 mm, and the gap was 0 mm and 2 mm.

[0031] As a result, it was found that the magnetic field passing through A5052 with a thickness of 2 mm is smaller than that of A5052 with a thickness of 0.8 mm at all frequencies. This phenomenon is known to be caused by the fact that the thicker the A5052, the more the passing magnetic field attenuates. It was also found that the passing magnetic field becomes smaller with a gap of 2 mm compared to a gap of 0 mm when the frequency (logarithmic display) exceeds around 5 kHz. The skin depth of A5052 has a resistivity of 4.9 x 10 -8 In Ωm, the resistance is approximately 1.1 mm at 10 kHz. Figure 5 shows the results when the A5052 thickness is 0.8 mm and 2 mm. These results suggest that at 10 kHz, the magnetic field is barely able to pass through the A5052, and the magnetic field passing through the vent hole (10 mm diameter) becomes dominant. In other words, as the frequency increases, the magnetic field passes only through the vent hole, while at lower frequencies, the magnetic field passes through other parts besides the vent hole. Therefore, at frequencies above 5 kHz, when the gap becomes large, the magnetic field that passes only through the vent hole 305a in the high-conductivity material layer 301 spreads and attenuates before reaching the vent hole 305b in the high-permeability material layer 302.

[0032] Figure 6 is a graph showing how the diameter of the vent hole and the size of the gap affect the passing magnetic field. In the graph in Figure 6, the horizontal axis represents the diameter of the vent hole, and the vertical axis represents the strength of the passing magnetic field. In the figure, the strength of the passing magnetic field is normalized to values ​​for a vent hole diameter of 10 mm and a gap size of 0 mm. Figure 6 shows that the passing magnetic field attenuates as the gap size increases from 0 mm to 1 mm, 2 mm, 3 mm, and 4 mm. However, looking at the results for 2 mm to 4 mm, there is no significant change in the effect even if the gap is larger than 1 / 3 of the vent hole diameter (the magnetic field attenuation increases to a certain extent). However, if the device configuration requires a larger gap, it is effective to increase the gap size to 1 / 3 or more of the vent hole diameter. As described above, based on the graph in Figure 6, it can be seen that the gap size needs to be at least 1 / 10 of the vent hole diameter.

[0033] Based on the findings described above, in this embodiment, the size of gap 304 in FIG. 2 is set to 1 / 10 or more of the diameter of the hole of ventilation hole 305, thereby making it possible to reduce the magnitude of the magnetic field passing through ventilation hole 305.

[0034] (iv) Comparison of this Example and Comparative Example Finally, a comparison will be made between this embodiment and a magnetic shield made by a known technique (comparative example).

[0035] 7 is a diagram showing an example of the cross-sectional configuration of magnetic shield 300′ (comparative example) made by a known technique. The difference between the example of the cross-sectional configuration of magnetic shield 300′ of the comparative example and the example of the cross-sectional configuration of magnetic shield 300 of this embodiment is that in the comparative example, highly conductive material layer 301 and highly magnetically permeable material layer 302 are made from a single plate, in which vent holes 305a and 305b are placed, and there is no gap between highly conductive material layer 301 and highly magnetically permeable material layer 302.

[0036] If there is no gap in the magnetic shield 300', if the positions of the vents 305a and 305b are significantly misaligned, the cross-sectional area through which the air flows will decrease, making it difficult for the air to flow. To prevent this, it is necessary to increase the diameter of one of the vents so that the cross-section of the entire vent does not become smaller even if the positions of the vents 305a and 305b are misaligned. In the comparative example of Figure 7, the diameter of the vent 305b in the high-permeability material layer 302 is larger than the diameter of the vent 305a. Increasing the diameter of the vent in this way increases the magnetic field that passes through.

[0037] Furthermore, using aluminum for the highly conductive material layer 301 is cost-effective. However, because aluminum is a soft material, punching is typically used to create multiple holes, such as vents. However, punching can cause the plate to warp, and post-punching processes, such as rolling, are required to correct the warp, resulting in poor hole position accuracy. Therefore, it is difficult to align the positions of the vents 305a and 305b. In this embodiment, however, a gap 304 is provided between the vents 305a and 305b as shown in FIG. 2. This prevents the cross-sectional area through which air flows from being reduced even if the positions of the vents 305a and 305b are misaligned, allowing the vents 305a and 305b to have the same diameter.

[0038] Furthermore, in this embodiment, as shown in FIG. 2, the portion of the highly conductive material layer 301 having the ventilation hole 305a is stacked on the highly conductive material layer 301 and secured to the frame 320 with bolts, thereby increasing the rigidity of the weaker ventilation hole portion. In contrast, the magnetic shield 300' of the known technology (comparison example) shown in FIG. 7 has a structure in which the rigidity near the ventilation hole 305 is weak. While increasing the rigidity can be achieved by increasing the thickness of the highly conductive material layer 301 or the high magnetic permeability material layer 302, there are limitations to the thickness when punching holes. For example, aluminum can only be punched to a thickness of approximately 3 mm or less, and harder materials such as permalloy and stainless steel can only be punched to an even thinner thickness. Furthermore, increasing the overall thickness of the plate is disadvantageous in terms of weight and cost, and the present embodiment is therefore superior in terms of weight, cost, and rigidity.

[0039] <Example 2> 8 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a second embodiment of the present disclosure. In FIG. 8, components denoted by reference numerals 1 to 330 are the same as those in FIG.

[0040] The difference between Example 2 and Example 1 (FIG. 2) is that the portion of high-permeability material layer 302 having vent hole 305b is a separate component from the other portions. Because the process of drilling many holes in a large plate is difficult and costly, it is better to create the portion where many holes, such as the vent holes, are to be drilled separately. Furthermore, in this structure, gap 304 is the sum of the thicknesses of high-conductivity material layer 301 and high-permeability material layer 302, which is effective when a large gap is desired.

[0041] Example 3 9 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a third embodiment of the present disclosure. In FIG. 9, the components denoted by reference numerals 1 to 330 are the same as those in FIG.

[0042] The difference between Example 3 and Example 1 (FIG. 2) is that the material and thickness of the highly conductive material layer 301 are different between the highly conductive material layer 301 in the portion without the ventilation hole 305a and the highly conductive material layer 301a in the portion with the ventilation hole 305a.

[0043] In the third embodiment, the highly conductive material layer 301 is made of a duralumin-based material such as A5052, which is an aluminum alloy, or copper or a copper alloy, as these materials are inexpensive, have excellent rigidity, and have excellent conductivity.

[0044] On the other hand, since the highly conductive material layer 301a is directly connected to the frame 320 with bolts 330, rigidity is not very important. For this reason, a material with excellent conductivity but a poor Young's modulus, such as pure aluminum or copper, can be selected as the material. Furthermore, since a material with high conductivity can be used for the highly conductive material layer 301a, its thickness can be made thin as needed. Note that when copper is used for the highly conductive material layer 301a, copper has more than twice the rigidity of aluminum, so the thickness of the highly conductive material layer 301a can be made half or less compared to when aluminum is used.

[0045] 9, the thickness of the highly conductive material layer 301a in the portion having the ventilation hole 305a is configured to be thinner than the thickness of the highly conductive material layer 301 in the portion not having the ventilation hole 305a, but the third embodiment is not limited to this. For example, the thickness of the highly permeable material layer 301a in the portion having the ventilation hole 305a may be configured to be thicker than the thickness of the highly permeable material layer 301 in the portion not having the ventilation hole 305a. Furthermore, the thickness of both the highly conductive material layer 301a in the portion having the ventilation hole 305a and the high permeable material layer 302 in the portion having the ventilation hole 305b may be configured to be thinner than the thickness of both the highly conductive material layer 301 in the portion not having the ventilation hole 305a and the high permeable material layer 302 in the portion not having the ventilation hole 305b.

[0046] Example 4 10 is a diagram showing an example of a cross-sectional configuration of a magnetic shield 300 for a scanning electron microscope according to a fourth embodiment of the present disclosure. In FIG. 10, the components denoted by reference numerals 1 to 330 are the same as those in FIG.

[0047] The difference between Example 4 and Example 3 (FIG. 9) is that in Example 4, frame 320 is not located near ventilation hole 305, but is located at a position slightly away from ventilation hole 305, and highly conductive material layer 301b having ventilation hole 305a is disposed widely so as to reach frame 320, thereby being directly connected to frame 320. More specifically, highly conductive material layer 301b having ventilation hole 305a and highly permeable material layer 302 having ventilation hole 305b are directly connected to frame 320 by being disposed widely so as to reach frame 320. E and vent 305b E from the highly conductive material layer end 301b E and the high magnetic permeability material layer end 302 E The distance to the frame 320 (the width of the peripheral area for fixing the highly conductive material layer 301b and the highly magnetically permeable material layer 302 to the frame 320 with bolts) can be at least twice the distance in the short direction of the subframe that makes up the frame 320.

[0048] In the fourth embodiment, since rigidity is important for the highly conductive material layer 301b, the layer is made of a material that can ensure rigidity, such as copper, copper alloy, or duralumin, which has high conductivity and rigidity.

[0049] The configuration of the fourth embodiment can be utilized when the vent 305 is disposed in a location where the frame 320 cannot be installed because a fan or the like is present near the vent 305 . [Explanation of symbols]

[0050] 1. Electron gun 2 apertures 3. Condenser lens 4 Scanning deflector 5 Objective Lenses 6 wafers 7 Holder 8 Electrical insulation section 9 tables 11 Secondary electron extraction deflector 12 Detectors 20 Overall control device 21 Optical system control device 22 Stage control device 25 Image acquisition device Stages 30 and 31 50 Stage position command 51 Optical system directive 52 Image capture conditions 53 Electron Gun Command 54 Condenser Lens Instruction 55 Scanning deflector command 56 Objective Lens Instructions 57 Holder voltage 58 Secondary electron extraction deflector command 59 detector data 61 Stage drive current 100 Primary electron beam 101 Secondary electron 200 Vacuum container 300, 300' magnetic shield 301, 301a, 301b Highly conductive material layer 302 High permeability material layer 304 Gap 305, 305a, 305b Vents 310 Ventilation Unit 320 frames 330 volts 400 Magnetic field generating coil 401 AC power supply 402 Magnetic field calculation point

Claims

1. a charged particle beam device that irradiates a sample with a charged particle beam to acquire an image of the sample; an overall control device that controls the charged particle beam device; a magnetic shield that forms an internal space for accommodating the charged particle beam device and the overall control device and that shields from an external magnetic field; an air cooling device that takes air into the magnetic shield to cool the internal space of the magnetic shield, the magnetic shield includes one or more highly conductive material layers and one or more highly permeable material layers; A sample inspection system, wherein the magnetic shield has air vents for cooling in each of the highly conductive material layer and the highly permeable material layer, and has a spatial gap between the highly conductive material layer and the highly permeable material layer where the air vents are located.

2. In claim 1, A sample inspection system, wherein the gap is set to be 1 / 10 or more of the diameter of the vent hole.

3. In claim 1, the magnetic shield includes a first magnetic shield portion having the vent hole and a second magnetic shield portion not having the vent hole, the first magnetic shield portion is configured separately and independently from the second magnetic shield portion, A sample inspection system, wherein the first magnetic shield portion is attached at least one of above the highly conductive material layer constituting the second magnetic shield portion or below the highly permeable material layer constituting the second magnetic shield portion, thereby forming the gap.

4. In claim 3, A sample inspection system, wherein the highly conductive material layer is configured to be thicker than the highly permeable material layer in the first magnetic shield section and the second magnetic shield section.

5. In claim 3, A specimen inspection system, wherein a material of the first magnetic shield portion is different from a material of the second magnetic shield portion.

6. In claim 5, A sample inspection system, wherein the second magnetic shield section is made of a material having higher rigidity than the first magnetic shield section.

7. In claim 1, the magnetic shield includes a first magnetic shield portion having the vent hole and a second magnetic shield portion not having the vent hole, the first magnetic shield portion is configured separately and independently from the second magnetic shield portion, A specimen inspection system, wherein the thickness and material of the highly conductive material layer of the first magnetic shield portion are different from the thickness and material of the highly conductive material layer of the second magnetic shield portion.

8. In claim 1, the magnetic shield includes a first magnetic shield portion having the vent hole and a second magnetic shield portion not having the vent hole, the first magnetic shield portion is configured separately and independently from the second magnetic shield portion, A specimen inspection system, wherein the thickness and material of the high magnetic permeability material layer of the first magnetic shield portion are different from the thickness and material of the high magnetic permeability material layer of the second magnetic shield portion.

9. In claim 1, the magnetic shield includes a first magnetic shield portion having the vent hole and a second magnetic shield portion not having the vent hole, the highly conductive material layer and the highly magnetically permeable material layer of the magnetic shield are fixed to a frame made up of a plurality of subframes, thereby forming the internal space for accommodating the charged particle beam device and the overall control device; a distance between two adjacent sub-frames in the frame is longer than a length between the air vents closest to an end of the first magnetic shield portion; the first magnetic shield portion has a vent hole formation region in which the plurality of vent holes are formed, and a peripheral region in which the vent holes are not formed, A specimen inspection system, wherein the first magnetic shield unit is fixed to the subframe and the second magnetic shield unit in the peripheral region.

10. In claim 9, A sample inspection system, wherein the distance from the edge of the vent hole closest to the end of the first magnetic shield section to the edge of the peripheral region in the first magnetic shield section is greater than twice the short-side distance of the subframe.

11. In claim 10, the highly conductive material layer and the highly permeable material layer of the first magnetic shield portion are made of copper, a copper alloy, or duralumin; A specimen inspection system, wherein the thickness of the highly conductive material layer of the first magnetic shield portion is approximately the same as the thickness of the highly conductive material layer of the second magnetic shield portion.

Images