charged particle beam device

Abstract

The purpose of the present disclosure is to provide a charged particle beam device that can measure an overall sample by making uniform a sample surface potential. In a charged particle beam device according to the present disclosure, a support member supporting a sample is formed using an insulating material, a surface, of a sample holder, that is in contact with the support member has a first concave portion that increases in depth from the outside of the support member toward the support member, and the support member is disposed in the first concave portion (see fig. 5A).

Description

[Technical Field]

[0001] The present disclosure relates to a charged particle beam device that irradiates a sample with a charged particle beam. [Background technology]

[0002] In recent years, the market for AR / VR technologies, such as wearable device displays, has rapidly expanded, increasing the demand for measuring patterns on wafers with insulator substrates such as quartz or sapphire (hereinafter referred to as "insulator wafers"). As a result, scanning electron microscopes (SEMs) used in the inspection and measurement of semiconductor devices are being required to stably measure insulator wafers with the same sensitivity and accuracy as conventional measurements of semiconductor wafers, such as Si.

[0003] In an SEM, electrons are generated by applying a high voltage to an electron source, which accelerates the electrons, focuses them with a focusing lens, and irradiates the object to be measured. At this time, secondary electrons generated according to the shape of the object to be measured are observed with a detector to obtain an SEM image.

[0004] Electrons emitted from an electron source have various energies, and this energy spread (ΔE) varies depending on the type of electron source. The difference in the energy of the electrons contained in the electron beam causes the electron trajectories to converge at different points, resulting in a blurred image (hereafter referred to as chromatic aberration). Generally, the smaller the diameter of the electron beam, the less the effect of chromatic aberration. When chromatic aberration is present, the minimum diameter dc of the electron beam is given by dc = CcαΔE / E. Here, α is the focusing half-angle for an electron beam at a certain accelerating voltage (E), and Cc is called the chromatic aberration coefficient of the objective lens and is the proportionality coefficient of ΔE / E. Cc is a function of the distance (working distance, WD) between the objective lens and the sample.

[0005] When the acceleration voltage of the electron beam irradiated onto the measurement target is high, the ratio of the energy width of the electron source to the acceleration voltage (ΔE / E) becomes smaller, reducing the effects of chromatic aberration and improving resolution. However, the irradiated electrons penetrate deeper and over a wider range into the sample. This causes secondary electrons to be generated even in areas far from the electron beam irradiation point, so the obtained image contains information from inside the sample, making it impossible to read the fine structure of the measurement target surface. Conversely, when the acceleration voltage of the electron beam is low, the ratio of the energy width of the electron source to the acceleration voltage (ΔE / E) becomes larger, increasing the effects of chromatic aberration and reducing resolution. However, the irradiated electrons penetrate shallower and narrower into the sample, allowing for clear observation of the sample surface.

[0006] To measure wafer patterns using an SEM, it is necessary to irradiate the wafer with an electron beam at a low acceleration voltage to obtain an image of the wafer's top surface. Therefore, we use the retarding method, which irradiates the wafer with an electron beam at a high acceleration voltage, where the ratio of the electron energy spread to the acceleration voltage is small, and decelerates the beam just before it hits the sample. A negative voltage of several kV (hereinafter referred to as the retarding voltage) is applied to the stage (hereinafter referred to as the sample holder) that holds the wafer on the backside of the wafer, creating a potential on the wafer surface (hereinafter referred to as the surface potential). By decelerating the electron beam irradiated at a high acceleration voltage using the surface potential just before it hits the wafer, it is possible to obtain an image of the wafer's surface pattern while suppressing chromatic aberration.

[0007] In the case of semiconductor wafers, the sample holder and wafer surface are at a uniform potential when a retarding voltage is applied, enabling images of consistent resolution across the entire wafer. However, when measuring insulator wafers with substrates made of insulators such as quartz or sapphire, it is not possible to apply a voltage directly from the sample holder to the wafer. The wafer surface potential is affected by charging and dielectric polarization due to electron beam irradiation. In addition, the greater the distance between the measurement target and the part of the sample holder surface where the potential is set by the application of a retarding voltage (hereinafter referred to as the retarding voltage application part), the more positive the surface potential of the measurement target becomes relative to the retarding voltage. Therefore, the acceleration voltage of the electron beam irradiated onto the sample changes depending on the measurement position. As a result, the amount of information inside the sample changes at each measurement position, resulting in differences in the measurement images. Therefore, in insulator wafer measurements, a method is needed to eliminate changes in the wafer surface potential caused by charging and changes in the distance between the sample holder and the measurement target, thereby achieving a uniform wafer surface potential.

[0008] Patent document 1 describes a method of placing a sample on support pins arranged on a stage and applying a voltage to a plate electrode arranged between the stage and the sample, thereby making the potential uniform within a certain range (hereinafter referred to as the inspection area) on the sample surface where the electron beam is irradiated. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-085838 Summary of the Invention [Problem to be solved by the invention]

[0010] In Patent Document 1, a plate electrode is placed on the stage of an SEM, and a voltage is applied to it to equalize the potential within the inspection area. However, in this document, the range of the inspection area is limited to the range of the plate electrode, and the plate electrode is placed inside the stage that supports the sample (hereinafter referred to as the support pin), so the range in which the potential can be equalized and measured is limited relative to the size of the sample.

[0011] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a charged particle beam device that can measure the entire surface of a sample by making the surface potential of the sample uniform. [Means for solving the problem]

[0012] In the charged particle beam device according to the present disclosure, a support member for supporting a sample is formed using an insulating material, and the surface of the sample holder that contacts the support member has a first recess whose depth increases from the outside of the support member toward the support member, and the support member is disposed within the first recess. [Effects of the Invention]

[0013] According to the charged particle beam device of the present disclosure, the entire surface of the sample can be measured by making the surface potential of the sample uniform. Other configurations, advantages, and effects of the present disclosure will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a configuration diagram of a charged particle beam system 1 according to a first embodiment. [Figure 2A] As an example, a front view of the sample holder 112 is shown in which the sample 111 is supported by four support stages 201. [Figure 2B] FIG. 2B is a side view of FIG. 2A. [Figure 2C] 1 is a diagram schematically showing the potential distribution in the vicinity of the sample 111. FIG. [Figure 3A]1 is a cross-sectional view of the sample 111, the sample holder 112, and the support table 201, taken along a line passing through the support table center 200. FIG. [Figure 3B] 10 shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. [Figure 4A] A side cross-sectional view of a support base (hereinafter referred to as insulating support base 201a) in which the material of support base 201 is changed to an insulating material is shown. [Figure 4B] 10 shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. [Figure 5A] 1 shows a side cross-sectional view of an inclined recess 202 formed around an insulating support base 201a. [Figure 5B] 5B is a side cross-sectional view in which the inclined recess 202 in FIG. 5A is changed to a stepped recess 204. FIG. [Figure 5C] 10 shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. [Figure 6] The results of comparing the maximum change in the surface potential of the sample 111 for each material of the support table 201 and each tilt angle 203 are shown. [Figure 7A] This shows an example in which the inside of the insulating support base 201a is cylindrical and an inclined recess 211 is disposed inside the support base. [Figure 7B] This shows a configuration example in which a stepped recess 212 is arranged inside a cylindrical support base 205 . [Figure 8A] 4B is a side cross-sectional view showing an example of a configuration in which the charged particle beam device 1 further includes an electrode 301 for preventing charging and dielectric polarization of the sample 111 in addition to the configuration shown in FIG. 4A. [Figure 8B] The equipotential lines 124 are shown when the aperture through which the primary electron beam 121 shown in FIG. 8A passes is set to a size that does not cause a problem of misalignment of the electrode 301. [Figure 9] This is a cross-sectional view in which a slanted recess 202 with a slant angle 203 is added to the configuration of the sample 111 and sample holder 112, insulating support 201a, and electrode 301 with an enlarged hole diameter for the passage hole, which pass through the support center 200 shown in Figure 8B. [Figure 10] 10 shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. DETAILED DESCRIPTION OF THE INVENTION

[0015] <First Embodiment> 1 is a configuration diagram of a charged particle beam device 1 according to a first embodiment of the present disclosure. The charged particle beam device 1 is configured as an electron microscope. The charged particle beam device 1 includes an electron source 101, a condenser lens 102, a condenser lens 103, an aperture 104, a reflector 105, an ExB deflector 106, a detector 107, a deflector 108, a deflector 109, an objective lens 110, a sample holder 112, a stage 113, a retarding power supply 114, a display 115, and a storage device 116.

[0016] The stage 113 can move horizontally to measure the entire surface of the sample 111. A voltage is applied to the stage 113 from a retarding power supply 114. A sample holder 112 is placed on the stage 113, and the sample 111 is held by the sample holder 112. By operating the stage 113, the sample holder 112 and the sample 111 held therein can be moved horizontally. The control device is a device for controlling the operation of each part, and is, for example, a computer. A storage device 116 stores a control table 117 that defines control conditions such as voltage and current for each part. The control device can also read the control table 117 from the storage device 116 and control each part based on the control conditions defined in the control table 117.

[0017] Electrons emitted from the electron source 101 are focused by condenser lenses 102 and 103 and irradiated onto a sample 111 as a primary electron beam 121 (charged particle beam). Aperture 104 is a component that determines the aperture angle of the primary electron beam 121 at objective lens 110, and has an aperture through which the primary electron beam 121 passes. Deflectors 108 and 109 deflect the primary electron beam 121 to scan it over the sample 111.

[0018] The objective lens 110 is a lens that focuses the deflected primary electron beam 121, and makes the primary electron beam 121 narrower by a magnetic field that is generated when a current flows through an internal coil.

[0019] Signal particles 122 are emitted from the sample 111 irradiated with the primary electron beam 121. Generally, signal particles emitted with an energy of 50 eV or less are called secondary electrons, and signal particles emitted with an energy of more than 50 eV and close to that of the primary electron beam 121 are called backscattered electrons. The signal particles 122 collide with the reflector 105 above the sample 111. When the signal particles 122 collide with the reflector 105, tertiary electrons 123 are emitted from the reflector 105. The tertiary electrons 123 are deflected by the electric field in the ExB deflector 106 and detected by the detector 107. The electric field and magnetic field in the ExB deflector 106 also act on the primary electron beam 121, but the effects of these two forces cancel each other out with respect to the primary electron beam 121, so the primary electron beam 121 travels straight toward the sample.

[0020] The tertiary electrons 123 detected by the detector 107 are A / D converted from analog data to digital data in the order of measurement. The control device uses the digital data to create a measurement image of the sample 111. The measurement image is output on a display 115.

[0021] The accuracy of the measurement image can be adjusted by the amount of landing energy of the primary electron beam 121 incident on the sample 111. Therefore, a negative voltage of several kV (hereinafter referred to as retarding voltage) is applied to the sample 111 by a retarding power supply 114 connected to the stage 113, thereby forming an electric field between the sample 111 and the objective lens 110 that decelerates the primary electron beam 121.

[0022] The voltage application path from the stage 113 to the sample 111 will now be described. The sample holder 112 is placed on the stage 113, to which a retarding power supply 114 is connected. To prevent damage or the generation of foreign matter caused by direct contact between the sample 111 and the sample holder 112, the sample holder 112 is provided with multiple support stages 201 (support members) on which the sample 111 is placed. The support stages 201 are made of a conductive material so that a retarding voltage is applied to the sample 111. The retarding voltage that forms the surface potential is applied to the sample 111 via the stage 113, the sample holder 112, and the support stages 201. This allows the acceleration voltage of the primary electron beam 121 to be adjusted as desired. The surface potential also serves to accelerate signal particles 122 generated on the sample upward.

[0023] However, the sample 111 to be measured is not limited to conductive materials; it may also be insulating materials such as silicon, quartz, or sapphire covered with a thin insulating film. In such cases, a uniform surface potential cannot be formed on the sample 111 due to the influence of the support stage 201. This makes it impossible to control the amount of energy of the primary electron beam 121 irradiated onto the sample 111 using the retarding voltage, and an image with the desired resolution cannot be obtained. In the following description, the sample 111 is assumed to be an insulating wafer.

[0024] The relationship between the sample 111, the sample holder 112, and the support table 201 will be described with reference to FIGS. 2A, 2B, and 2C.

[0025] 2A shows a front view of the sample holder 112 in which the sample 111 is supported by four support stages 201. The holding of the sample 111 is omitted. The support stages 201 are placed on the surface of the sample holder 112 and at arbitrary positions (support points) within the surface of the sample 111, and support the sample 111 at four points.

[0026] 2B is a side view of Fig. 2A. The support stage 201 is arranged between the sample 111 and the sample holder 112 to prevent damage or the generation of foreign matter that may occur due to direct contact between the sample 111 and the sample holder 112, and is configured as a protrusion that supports the sample 111. The support stage 201 also serves as a path for conducting the retarding voltage applied to the sample holder 112 to the sample 111 and for forming an electric field in the sample to decelerate the primary electron beam 121.

[0027] Figure 2C is a schematic diagram showing the potential distribution near the sample 111. This figure shows the potential distribution relative to the center of the sample 111 when a primary electron beam 121 is irradiated from the objective lens 110 positioned above the sample 111. Equipotential lines 124 indicate the potential when the primary electron beam 121 is irradiated onto the sample 111. A retarding voltage is applied to the sample holder 112 and the support table 201. The sample 111, which is an insulating wafer placed in an electric field, is polarized with a bias toward positive and negative polarities. The front surface of the sample 111 is negatively polarized, and the back surface is positively polarized. The voltage applied to the insulating sample 111 varies depending on the distance between the retarding voltage application unit (the portion on the surface of the sample holder 112 or the surface of the support table 201 where the potential is set by the retarding voltage) and the sample 111. As a result, the surface potential of the sample 111 differs, for example, between the area above the support table 201 and other areas. This is because the top surface of the sample holder 112 and the top surface of the support table 201 are at the same potential.

[0028] 3A and 3B, the details of the support table 201 and the change in the sample surface potential at each position will be described.

[0029] Figure 3A is a cross-sectional view of the sample 111, sample holder 112, and support table 201, passing through the support table center 200. It is assumed that the support table 201 in Figure 3A is made of a conductive material. An objective lens 110 is installed above the sample 111, and a primary electron beam 121 is irradiated onto an irradiation point 125 on the sample 111. The equipotential lines 124 generated by the voltage applied to the sample 111 and support table 201 at this time are shown. The irradiation position R0 of the primary electron beam 121 when irradiated onto the support table center 200 is set as the origin, and the irradiation positions when the sample holder 112 is moved horizontally at regular intervals are defined as R1, R2, and R3, respectively. R1 to R3 in Figure 3A each indicate the positional relationship of the primary electron beam irradiation point 125. R1 is the position on the support table 201. R2 is the edge position of the support table 201. R3 is a position away from the support table 201, and there is no support table 201 directly below the sample 111; only the sample holder 112 is present.

[0030] When the support base 201 is conductive, the retarding voltage is applied up to the top surface of the support base 201, and therefore, compared to the position R3 (flat portion), the surface potential of the sample 111 at the point in contact with the support base 201 (for example, position R0 in Figure 3A) is more strongly affected by the retarding voltage and changes in the negative direction.

[0031] Figure 3B shows the difference in surface potential of the sample 111 for each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. The vertical axis shows the surface potential difference when the surface potential of the sample 111 on the flat portion (position R3) of the sample holder 112 is set to 0 V, and the horizontal axis shows the electron beam irradiation position R when the sample holder 112 is moved horizontally with the support stage center 200 as the base point. This figure shows the sample surface potential difference with the flat portion as the reference when the sample holder 112 is moved horizontally at regular intervals, such as from R0 to R3 shown in Figure 3A. At positions R0 to R2, where the distance between the surface of the sample 111 and the retarding voltage application unit is small, the value of the surface potential of the sample 111 approaches the value of the retarding voltage, and therefore changes in the negative direction. Conversely, at position R3, the distance between the sample 111 and the retarding voltage application unit is large, and therefore the value of the surface potential of the sample 111 changes in the positive direction.

[0032] An example of the shape of the support table 201 and the surface potential of the sample in the first embodiment will be described with reference to FIGS. 4A and 4B.

[0033] FIG. 4A shows a cross-sectional side view of a support stage (hereinafter, insulating support stage 201a) in which the material of the support stage 201 has been changed to an insulating material. As in FIG. 3A, a primary electron beam 121 is irradiated onto an irradiation point 125 on the sample 111. The equipotential lines 124 formed by the voltages applied to the sample 111 and the insulating support stage 201a are shown. R0 to R3 are the same as in FIG. 3A. Since a retarding voltage cannot be applied directly to the insulating support stage 201a and the retarding voltage is no longer conducted to the top of the support stage, the equipotential lines 124 shift toward the sample holder 112 compared to FIG. 3A. Accordingly, the surface potential of the sample 111 in contact with the insulating support stage 201a shifts in a positive direction compared to FIG. 3A. However, due to the dielectric polarization of the insulating support stage 201a, the equipotential lines are distorted near the insulating support stage 201a.

[0034] Figure 4B shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. The vertical axis shows the surface potential difference when the surface potential of the sample 111 on the flat portion of the sample holder 112 is set to 0 V, and the horizontal axis shows the electron beam irradiation position R when the sample holder 112 is moved horizontally with the support stage center 200 as the base point. This figure shows the sample surface potential with the flat portion as the reference when the sample holder 112 is moved horizontally at regular intervals, such as from R0 to R3 shown in Figure 4A. The solid line shows the surface potential when the conductive support stage 201 shown in Figure 3B is used, and the dashed-dotted line shows the surface potential when the insulating support stage 201a is used.

[0035] By changing the material of the support base to an insulating material, it is possible to prevent the retarding voltage from being applied to the top surface of the support base. Furthermore, the distance between the surface to which the potential is set by applying the retarding voltage and the surface of the sample 111 is the same between the location where the insulating support base 201a is located and other locations. This is because the potential of the insulating support base 201a is not affected by the retarding voltage. As a result, the equipotential lines 124 on the insulating support base 201a move closer to the sample holder 112 compared to Figure 3A. However, due to the dielectric polarization of the insulating support base 201a as well as the sample 111, the sample surface potential changes in the negative direction at R0 to R2. As a result, the change in the surface potential of the sample 111 cannot be reduced to a negligible value.

[0036] 5A, 5B, 5C, and 6, the details of the sample holder 112 having a recessed periphery and the sample surface potential will be described.

[0037] FIG. 5A shows a cross-sectional side view of a slanted recess 202 formed around an insulating support base 201a. A slanted recess 202 (first recess) is arranged around the insulating support base 201a, deepening toward the support base center 200 at a certain inclination angle 203. As in FIG. 4A, a primary electron beam 121 is irradiated onto an irradiation point 125 on the sample 111. The diagram shows equipotential lines 124 formed by the voltages applied to the sample 111 and the insulating support base 201a. The surface potential of the sample 111 is influenced by the dielectrically polarized insulating support base 201a, and changes in the negative direction as it approaches the support base center 200. Therefore, a recess that deepens toward the support base center 200 is formed near the insulating support base 201a. The insulating support base 201a is placed within this recess. By placing the insulating support base 201a in the recess, the distance between the sample 111 and the retarding voltage application unit in the vicinity of the insulating support base 201a increases. This shifts the surface potential of the sample 111 in the positive direction, thereby canceling out the negative potential change caused by the dielectric polarization of the insulating support base 201a. This further reduces the amount of change in the surface potential of the sample 111 at each position.

[0038] 5B shows a side cross-sectional view in which the inclined groove 202 in FIG. 5A has been changed to a stepped groove 204. Changing the shape of the groove to a stepped shape still achieves the same effect of reducing the amount of change in the surface potential of the sample 111 as with the inclined groove. As mentioned above, the surface potential of the sample 111 changes depending on the distance between the sample 111 and the retarding voltage application section, so it is possible to adjust the surface potential of the sample 111 by changing the depth of the step and the width to the next step.

[0039] Figure 5C shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. The vertical axis represents the surface potential difference when the surface potential of the sample 111 on the flat portion of the sample holder 112 is set to 0 V, and the horizontal axis represents the electron beam irradiation position R when the sample holder 112 is moved horizontally with the support stage center 200 as the base point. Here, the sample surface potential relative to the flat portion is plotted when the sample holder 112 is moved horizontally at regular intervals, from R0 to R3 as shown in Figure 4A. The dashed-dotted line represents the surface potential of the sample 111 when the insulating support stage 201a shown in Figure 4B is used. The dashed-two-dot line represents the surface potential of the sample 111 when the recess is arranged as shown in Figure 5A. The effect of reducing the amount of change in surface potential due to the stepped recess 204 is equivalent to that of the inclined recess 202 having an inclination angle formed by the angle A and angle B of the stepped recess 204 shown in Figure 5B, the hypotenuse connecting the lower end of the insulating support base 201a, and the surface of the sample holder 112.

[0040] Figure 6 shows the results of comparing the maximum change in the surface potential of the sample 111 for various materials and tilt angles 203 of the support stage 201. The vertical axis shows the maximum change in the surface potential of the sample 111 relative to the flat surface, and the horizontal axis shows the material and tilt angle 203 of the support stage being compared. Without a recess, the maximum change in the surface potential of the sample 111 is reduced to less than one-third of that of a conductive support stage by using an insulating support stage material. When the tilt angle 203 of the recess on the periphery of the insulating support stage 201a is set to 45° or less, the positive change in the surface potential due to the recess is greater than the negative change in the surface potential due to the dielectric polarization of the sample 111 and the insulating support stage 201a. When the tilt angle 203 of the recess on the periphery of the insulating support stage 201a is set to 60°±15°, the change in the surface potential of the sample is smaller than when only the insulating support stage 201a is used. 6, it can be seen that by using an insulating support base, the amount of change in surface potential can be reduced to a fraction of that of a conductive support base. Furthermore, by forming a recess in the sample holder 112, it can be seen that the amount of change in surface potential can be further reduced to a fraction of that of a conductive support base.

[0041] Since the amount of change in the surface potential of the sample 111 changes between positive and negative across zero, it is possible to make the amount of change in the surface potential zero and make the surface potential of the sample 111 a uniform value by changing the inclination angle 203 of the inclined recess 202. As a result, the potential change occurring on the surface of the sample 111 is reduced to a negligible level, making it possible to obtain an image with the desired resolution.

[0042] 5A to 6, an example has been described in which the potential difference between the surface potential of the portion of sample 111 supported by insulating support base 201a (e.g., R0) and the surface potential of the portion not supported (e.g., R3) is nearly zero. This potential difference is preferably zero. However, it should be noted that the effect of this embodiment can be achieved to the extent that this potential difference can be reduced in the presence of an indentation compared to the absence of an indentation.

[0043] It is desirable that the surface of the sample holder 112 that comes into contact with the support table 201 is larger than the planar size of the sample 111. This makes it possible to provide a uniform surface potential over the entire surface of the sample 111. The same applies to the following embodiments.

[0044] <Embodiment 2> An example of the configuration of a charged particle beam system 1 according to a second embodiment of the present disclosure will be described with reference to Figures 7A and 7B. Matters described in the first embodiment but not described in the second embodiment can also be applied to the second embodiment unless there are special circumstances.

[0045] 7A shows an example in which the inside of insulating support stage 201a is cylindrical (hereinafter referred to as cylindrical support stage 205), and inclined recess 211 is arranged inside the support stage. FIG. 7A is a cross-sectional view of sample 111, sample holder 112, and cylindrical support stage 205, passing through support stage center 200. Objective lens 110 is installed directly above sample 111. Assume that primary electron beam 121 is irradiated onto sample 111. The bottom surface of cylindrical support stage 205 has a hole for inserting conductive fixing screw 207, and a conductive fixing part (hereinafter referred to as inclined fixing part 206) with an inclination angle 203 at the end of the upper surface is fixed by screw 207 inserted from the bottom of sample holder 112.

[0046] The retarding voltage applied to the sample holder 112 is applied to the inclined fixing portion 206 via the conductive fixing screw 207. The inclined portion of the inclined fixing portion 206 forms an inclined recess 211 inside the inner wall of the cylindrical support base 205, thereby lowering the surface of the sample holder 112. As will be described later, the inclined recess 211 can cancel at least a part of the change in the surface potential of the sample 111.

[0047] 7B shows a configuration example in which a stepped recess 212 is arranged inside a cylindrical support base 205. As in FIG. 7A, the bottom surface of the cylindrical support base 205 has a hole for passing a conductive fixing screw 207, and a conductive fixing portion (hereinafter referred to as a stepped fixing portion 208) with a stepped cutting on the edge of the top surface is fixed by the conductive fixing screw 207 inserted from the bottom of the sample holder 112. The retarding voltage applied to the sample holder 112 is applied to the stepped fixing portion 208 via the conductive fixing screw 207. The stepped portion of the stepped fixing portion 208 forms a stepped recess 212 on the inside of the cylindrical support base 205, thereby lowering the surface position of the sample holder 112.

[0048] As shown in Figures 4A and 4B, at the contact area between the sample 111 and the insulating support 201a, both the sample 111 and the insulating support 201a are dielectrically polarized, resulting in a negative change in the sample surface potential compared to other areas. Therefore, by making the support cylindrical, the contact area between the sample 111 and the insulating support 201a is reduced, thereby reducing the potential change caused by dielectric polarization. Furthermore, to address the negative surface potential change occurring at the contact area between the sample 111 and the cylindrical support 205, a sloped groove 211 or a stepped groove 212 is formed inside the cylindrical support 205, increasing the distance between the retarding voltage application unit and the sample 111, thereby changing the surface potential of the sample 111 in the positive direction. The change in the sample surface potential occurring at the contact area between the cylindrical support 205 and the sample 111 is counteracted by the grooves arranged inside the cylindrical support 205, thereby reducing the change in the surface potential of the sample 111 occurring near the support 205.

[0049] The effect of the recess on the inside of the cylindrical support base 205 can be exhibited to the extent that it is formed to the extent that it can cancel at least a part of the change in the sample surface potential that occurs at the contact area between the cylindrical support base 205 and the sample 111. In addition, by combining this with the recess on the outer periphery of the support base described in the first embodiment, the change in the surface potential can be further suppressed.

[0050] <Third Embodiment> In the configuration shown in FIG. 5A in which an inclined recess 202 having an inclination angle 203 is disposed near an insulating support table 201a, the surface potential of the sample 111 is uniformly shifted in the positive direction compared to the retarding voltage due to the dielectric polarization of the sample 111 and the insulating support table 201a, charging due to irradiation with the primary electron beam 121, and changes in the distance from the retarding voltage application unit. Therefore, in the third embodiment of the present disclosure, a configuration for suppressing the uniform shift in the surface potential of the sample 111 will be described with reference to FIGS. 8A, 8B, 9, and 10. The matters described in the first and second embodiments but not described in the third embodiment can also be applied to the third embodiment unless there are special circumstances.

[0051] 8A is a side cross-sectional view showing an example of a configuration in which the charged particle beam device 1 further includes an electrode 301 for preventing charging and dielectric polarization of the sample 111 in addition to the configuration shown in FIG. 4A. The electrode 301 is placed above the sample 111, and a negative voltage of the same polarity and value as the sample holder 112 is applied to the electrode 301. The objective lens 110 is installed above the electrode 301, and the primary electron beam 121 is irradiated onto an irradiation point 125 on the sample 111. The diagram shows equipotential lines 124 formed by the voltages applied to the sample 111 and the insulating support base 201a. R0 to R3 are the same as those in FIG. 4A.

[0052] A hole for the primary electron beam 121 is disposed at the center of the electrode 301, and a negative voltage equal to the retarding voltage is applied to the electrode 301. Therefore, no electric field is generated between the sample holder 112 and the electrode 301, preventing dielectric polarization of the sample 111. Furthermore, by decelerating the primary electron beam 121 with the voltage (retarding voltage) applied to the electrode 301, it becomes possible to control the acceleration voltage of the primary electron beam 121 using the retarding voltage, and to obtain an image with the desired resolution.

[0053] However, this method has the problem that the primary electron beam 121 is decelerated on the surface of the electrode 301, not on the surface of the sample 111, and therefore the distance the decelerated electrons travel before irradiating the sample 111 becomes long. As mentioned above, when the acceleration voltage of the electron beam is low, the ratio (ΔE / E) of the energy width of the electron source to the acceleration voltage increases, and the effect of chromatic aberration also increases. The increase in chromatic aberration during the time it takes for the low-acceleration-voltage electron beam decelerated by the electrode 301 to be irradiated onto the sample 111 reduces the resolution.

[0054] Furthermore, in order to make the surface potential of the sample 111 the same as the retarding voltage, it is necessary to make the diameter of the central hole of the electrode 301 very small. However, there is also the problem that, when the amount of positional deviation of the electrode 301 is the same, the smaller the central hole diameter, the greater the degradation in resolution.

[0055] FIG. 8B shows equipotential lines 124 when the passage hole of the primary electron beam 121 shown in FIG. 8A is sized so that misalignment of the electrode 301 does not cause a problem. The other configurations are the same as those in FIG. 8A. If the diameter of the passage hole arranged in the electrode 301 is increased (for example, the hole diameter is made larger than the surface size of the insulating support base 201a), the influence of misalignment of the electrode 301 is reduced. Meanwhile, near the passage hole, potential changes occur in the surface potential of the sample 111 due to charging, dielectric polarization, and the distance between the retarding voltage application unit and the sample 111. This causes the surface potential of the sample 111 to become nonuniform, making it impossible to control the acceleration voltage of the primary electron beam 121 using the retarding voltage. Therefore, we consider using the configuration of embodiment 1 in addition to the configuration of FIG. 8B.

[0056] Figure 9 is a cross-sectional view of the sample 111, sample holder 112, insulating support 201a, and electrode 301 with an enlarged hole diameter passing through the support base center 200 shown in Figure 8B, with an inclined recess 202 with an inclination angle 203 added. The equipotential lines 124 formed by the voltage applied to the sample 111 and insulating support 201a are also shown. Furthermore, the irradiation position R0 of the primary electron beam 121 when irradiating the center of the support base is set as the origin, and the positions R1, R2, and R3 are respectively shown as the sample holder 112 moved horizontally at regular intervals. R1 to R3 in Figure 9 show the relative positions of the primary electron beam irradiation point 125. Here, R1 is a position on the insulating support 201a, R2 is the edge position of the insulating support 201a, and R3 is a position distant from the insulating support 201a. There is no insulating support 201a directly below the sample 111; only the sample holder 112 is located.

[0057] Figure 10 shows the difference in surface potential of the sample 111 at each primary electron beam irradiation point 125, with the surface potential at position R3 as the reference. The vertical axis represents the surface potential of the sample 111, and the horizontal axis represents the electron beam irradiation position R when the sample holder 112 is moved horizontally with the support stage center 200 as the base point. Here, the retarding voltage applied to the sample 111 is Vr when the sample holder 112 is moved horizontally at a constant interval, such as from R0 to R3 shown in Figures 8A, 8B, and 9. The surface potentials in Figures 8A, 8B, and 9 are plotted. The solid line represents the surface potential of the sample 111 in Figure 8A, the dashed line represents the surface potential of the sample 111 in Figure 8B, and the dashed line represents the surface potential of the sample 111 generated in Figure 9.

[0058] As described with reference to FIG. 8A, by placing the electrode 301 to which the retarding voltage is applied above the sample 111, no electric field is generated between the sample holder 112 and the electrode 301, thereby preventing dielectric polarization of the sample 111. Near the primary electron beam 121 passage hole arranged in the electrode 301, potential changes are canceled out by the insulating support 201a shown in FIG. 5A of the first embodiment and the inclined recess 202 arranged around it, making it possible to reduce the amount of change in the surface potential of the sample 111 for each irradiation position, as shown in FIG. 5C. In addition, since the retarding voltage is applied to the electrode 301, the retarding voltage application portion approaches the surface of the sample 111. As a result, the surface potential of the sample 111 changes in the negative direction, thereby suppressing the deviation between the surface potential of the sample 111 and the retarding voltage.

[0059] <Modifications of the present disclosure> The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0060] In the above embodiment, an electron microscope has been given as an example of the charged particle beam device 1, but the configuration according to the present disclosure can also be applied to other devices that irradiate charged particle beams.

[0061] In the above embodiments, examples of the sample 111 made of an insulating material include, for example, a semiconductor wafer or a photomask using an insulating material as a substrate, but the present disclosure is not limited to these, and can be applied to other insulating samples. [Explanation of symbols]

[0062] 1: charged particle beam device, 101: electron source, 102: condenser lens 1, 103: condenser lens 2, 104: aperture, 105: reflector, 106: ExB deflector, 107: detector, 108: deflector 1, 109: deflector 2, 110: objective lens, 111: sample, 111: sample holder, 113: stage, 114: retarding power supply, 115: display, 116: storage device, 121: primary electron beam beam, 122: secondary electron beam, 123: tertiary electron beam, 124: equipotential line, 125: primary electron beam irradiation point, 200: support base center, 201: support base, 201a: insulating support base, 202: inclined recess, 203: inclination angle, 204: stepped recess, 205: cylindrical support base, 206: inclined fixing portion, 207: fixing screw, 208: stepped fixing portion, 211: inclined recess, 212: stepped recess, 301: electrode

Claims

1. A charged particle beam device that irradiates a sample with a charged particle beam, a support member on which the sample is placed; a sample holder supporting the support member; Equipped with the support member is formed using an insulating material, a surface of the sample holder that comes into contact with the support member has a first recess whose depth increases from the outside of the support member toward the support member; the support member is disposed within the first recess; the first recess is configured such that a distance between the sample and the sample holder increases from an outer periphery of the first recess toward the support member; The surface of the sample holder that comes into contact with the support member has an area larger than that of the sample. A charged particle beam device characterized by:

2. The first recess is configured by a slope or a step that deepens from the outside of the support member toward the support member.

2. The charged particle beam device according to claim 1, wherein:

3. The tilt has an angle of 60°±15° with respect to the surface of the sample holder.

3. The charged particle beam device according to claim 2.

4. The support member is arranged to support the sample at a plurality of support points.

2. The charged particle beam device according to claim 1, wherein:

5. the charged particle beam device further comprises a power supply that applies a voltage to the sample holder to generate an electric field that decelerates the charged particle beam; The first recess is When the power supply applies the voltage, the potential difference between the potential of the portion of the sample that is supported by the support point and the potential of the portion that is not supported by the support point becomes smaller than when the first recess is not present. It is configured as follows:

5. The charged particle beam device according to claim 4.

6. The support member has a cylindrical shape and is configured to support the sample at the top of the cylinder.

2. The charged particle beam device according to claim 1, wherein:

7. The surface of the sample holder that comes into contact with the support member has a second recess whose depth increases from the inside of the cylindrical shape toward the inner wall of the cylindrical shape.

7. A charged particle beam device according to claim 6.

8. the charged particle beam device further comprises a power supply that applies a voltage to the sample holder to generate an electric field that decelerates the charged particle beam; The second recess is configured to increase the distance between the portion of the sample holder to which the voltage is applied and the sample, compared to other portions of the sample holder, thereby canceling at least a part of the fluctuation in the surface potential of the sample caused by the dielectric polarization of the support member at a contact portion where the support member and the sample come into contact.

8. A charged particle beam device according to claim 7.

9. the charged particle beam device further comprises an electrode disposed between a beam source that emits the charged particle beam and the sample; the charged particle beam device further comprises a power supply that applies a voltage to the sample holder to generate an electric field that decelerates the charged particle beam; The power supply applies a voltage to the electrode having the same polarity as the voltage applied to the sample holder by the power supply, thereby suppressing the dielectric polarization of the sample.

2. The charged particle beam device according to claim 1, wherein:

10. The power supply applies to the electrodes a voltage value that is the same as the voltage value applied to the sample holder.

10. The charged particle beam device according to claim 9, wherein:

11. the electrode has a hole through which the charged particle beam passes; The opening size of the hole is larger than the planar size of the support member.

10. The charged particle beam device according to claim 9, wherein:

12. The sample is a semiconductor substrate using an insulating material as a substrate.

2. The charged particle beam device according to claim 1, wherein:

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