JP6362941B2 - Charged particle beam equipment - Google Patents

Description

  The present invention relates to a charged particle beam apparatus, and more particularly to a charged particle beam apparatus including a pump for evacuating a beam column of the charged particle beam apparatus.

  In charged particle beam devices such as scanning electron microscopes, transmission electron microscopes, and semiconductor measurement / inspection devices, the sample is irradiated with a charged particle beam (electron beam) generated in a lens barrel in an ultra-high vacuum environment. An observation image of the sample is acquired by detecting secondary electrons, reflected electrons, or transmitted electrons emitted from the sample. When the lens barrel vibrates, the irradiation position of the electron beam fluctuates from the original position, image distortion may occur, and the observed image may become unclear.

  On the other hand, in the charged particle beam apparatus, the atmosphere near the beam source (electron source or ion source) needs to be in a high vacuum state. For this purpose, an evacuation device such as an ion pump needs to be installed in the vicinity of the column, but this ion pump may be an excitation source for vibrating the column.

  Patent Document 1 discloses a technique for suppressing vibration of a lens barrel using a dynamic vibration absorber having a natural frequency that is substantially the same as the natural frequency of a column that supports an exhaust system. Patent Document 2 discloses a technique for attenuating vibration of an ion pump in a short time by supporting the ion pump with a frame having a viscoelastic body. Patent Document 3 discloses a technique for realizing vibration reduction of a lens barrel using a vibration damping device including a laminated structure including a viscoelastic body and a metal plate.

JP 2001-76660 A JP 2011-003414 A (corresponding US Pat. No. 8,629,410) WO2011 / 043391 (corresponding US patent USP8,729,476)

  The vibration of the lens barrel or the ion pump causes the observation image to deteriorate. In order to reduce these vibrations, it is effective to attach a vibration damping device to the lens barrel and ion pump. However, if a vibration damping device is attached to the lens barrel and ion pump separately to accommodate each vibration, In addition to the complexity of the device, there is a concern about cost increase and workability deterioration.

  When the dynamic vibration absorber described in Patent Document 1 is used, there is only one natural frequency and vibration direction that can be suppressed, and in order to support a plurality of vibration modes, it is necessary to install a plurality of dynamic vibration absorbers. With increased equipment weight and complexity. Further, in the techniques disclosed in Patent Documents 1, 2, and 3, if it is attempted to reduce vibrations of the lens barrel and the ion pump at the same time, it is necessary to attach a vibration damping device to each of them, which increases costs and improves workability Decreases.

  As in Patent Document 2, a laminated structure in which a viscoelastic body is sandwiched between metal plates is attached to a frame fixed at a position opposite to one end of the ion pump and the ion pump. Can be attenuated. This is because the ion pump vibrates in the in-plane direction with respect to the viscoelastic body, thereby efficiently shearing and deforming the viscoelastic body. On the other hand, the vibration of the lens barrel has a large component that vibrates in the out-of-plane direction of the currently arranged viscoelastic body, and the effect of reducing the vibration of the lens barrel cannot be expected.

  Hereinafter, a charged particle beam apparatus that aims to reduce vibration of a charged particle beam apparatus barrel caused by the presence of an evacuation apparatus attached in the vicinity of a column with a relatively simple configuration will be described.

  As an aspect for solving the above-described object, a sample chamber in which a sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, and an interior of the lens barrel are provided. A charged particle beam apparatus comprising a pump for evacuating and a support member for supporting the pump, wherein the support member includes an inclination allowing portion for allowing an inclination of the support member. Propose a wire system.

  According to the above configuration, it is possible to reduce the vibration of the charged particle beam apparatus barrel caused by a vacuum exhaust device such as an ion pump with a relatively simple configuration.

It is a figure which shows an example of the charged particle beam apparatus provided with the inclination permission member which accept | permits the inclination of the support member which supports an ion pump. It is a figure which shows the natural vibration mode of an ion pump and a lens-barrel. It is a figure which shows an example of the charged particle beam apparatus provided with the supporting member of the ion pump which does not have an inclination permission member. It is a figure which shows a deformation | transformation when the lens-barrel of the charged particle beam apparatus provided with the supporting member of the ion pump which does not have an inclination permission member vibrates in ay direction. It is a figure which shows a deformation | transformation when the lens-barrel of the charged particle beam apparatus provided with the supporting member of the ion pump which does not have an inclination permission member vibrates to ax direction. It is a figure which shows an example of a rotation support member. It is a figure which shows an example of a rotation support member. It is a figure which shows an example of a deformation | transformation support member. It is an example of the FEM analysis result which shows the usefulness of an inclination tolerance member. It is a figure which shows an example of the charged particle beam apparatus provided with the inclination permission member. It is a figure which shows an example of the charged particle beam apparatus provided with the inclination permission member. It is a figure which shows an example of the charged particle beam apparatus provided with the inclination permission member. It is a figure which shows an example of the charged particle beam apparatus provided with the inclination permission member.

  Hereinafter, a charged particle beam apparatus that enhances the vibration reduction effect of the lens barrel and enables high-resolution and high-throughput measurement and inspection using a vibration damping device attached to the ion pump will be described.

  In the following embodiments, a sample chamber in which a sample is arranged, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, and the inside of the lens tube are evacuated. A charged particle beam device comprising an ion pump (evacuation device) and a support member that supports the ion pump via a viscoelastic body, wherein the support member is configured to move the mirror when the lens barrel is inclined. A charged particle beam apparatus including a bent portion (tilt allowing member) that can be tilted in the same direction as the lens barrel while maintaining parallel to the tube will be described.

  According to the above configuration, the vibration of the ion pump and the lens barrel can be attenuated in a short time by using the vibration damping device of the ion pump without attaching an expensive vibration damping device to the lens barrel. A resolution observation image can be acquired at high speed.

  In semiconductor measurement / inspection equipment, the demand for higher resolution is increasing due to the miniaturization of semiconductor devices, while the diameter of specimens and high throughput are increasing. It is predicted that the stage reaction force will increase with increasing throughput. All of these are factors that cause deterioration in the image quality of the observation image obtained by the charged particle beam apparatus.

  As an apparatus that keeps the inside of a lens barrel of a charged particle beam apparatus in an ultra-high vacuum (hereinafter referred to as an exhaust system), there is no moving part and no driving force such as a motor is required. Representative. In order to keep the periphery of the chip emitting the electron beam in an ultrahigh vacuum, it is necessary to install an ion pump in the electron gun at the top of the lens barrel. Therefore, the ion pump increases the position of the center of gravity of the lens barrel and works in the direction of decreasing the natural frequency of the lens barrel. The ion pump is not equipped with a vibration source such as a motor. However, when a disturbance such as floor vibration, environmental noise, or stage reaction force is applied, the ion pump itself vibrates and vibrates the lens barrel. Can be a source. Therefore, vibration reduction of the ion pump is indispensable for increasing resolution and throughput.

  Hereinafter, a charged particle beam apparatus capable of suppressing the influence of vibration caused by the presence of an ion pump will be described with reference to the drawings.

  FIG. 1 is a diagram showing an outline of a charged particle beam apparatus. Here, a length measurement SEM (Critical Dimension Scanning Electron Microscope) will be described as an example of the charged particle beam apparatus. The length measuring SEM includes a barrel 2 having a charged particle source 1 therein, an ion pump 8A for evacuating the barrel 2 to a high vacuum, and a stage 5 on which a sample 4 to be observed is placed. It consists of chamber 3. The ion pump 8 </ b> A includes a rectangular parallelepiped main body portion and a cylindrical pipe, and one end of the cylindrical pipe is coupled to the lens barrel 2. The lens barrel 2 is attached to the upper part of the sample chamber 3, and the sample chamber 3 is fixed to the gantry 7 by a vibration isolation mount 6.

  A vibration damping device for suppressing vibration of the ion pump 8A (hereinafter referred to as an ion pump vibration damping device) includes a laminated structure in which a viscoelastic body 11A is fixed between a support plate 10A and a support plate 12A, and a sample chamber 3. The support plate 10A is fixed to the ion pump 8A, and the support plate 12A is fixed to the frame 13, respectively. The frame 13 is interposed between the sample chamber 3 and the ion pump 8A, and functions as a support member that supports the ion pump 8A at a predetermined height. In addition, the hinge 16A functions to allow the frame 13 to move in the movable direction of the hinge and limit the movement in other directions.

  The viscoelastic body 11A can obtain a higher damping capacity in shear deformation than in tensile and compression deformation. Since the ion pump damping device has the hinge 16A at the lower end of the frame 13, rotational deformation in the xz plane is facilitated. Therefore, even when the lens barrel 2 is inclined, relative displacement can be generated in the in-plane direction of the support plate while maintaining the support plate 10A and the support plate 12A in parallel, and the viscoelastic body 11A is shear-deformed. High damping ability can be obtained.

  In general, the charged particle beam apparatus obtains an observation image from secondary electron intensity obtained by irradiating an observation object with a charged particle beam 9 generated from the charged particle source 1. The charged particle beam 9 is irradiated from the charged particle source 1 on the upper part of the lens barrel 2 to the sample 4 fixed to the stage 5 in the sample chamber 3 that passes through the inside of the lens barrel 2 and is kept in a vacuum. The intensity of the secondary electrons detected from the sample 4 is imaged and displayed as the coordinates of the irradiation position and the shade corresponding to the secondary electron intensity at the coordinates. Therefore, when some vibration is applied to the charged particle beam apparatus and the lens barrel 2 and the stage 5 are vibrated, the charged particle beam 9 is not irradiated at the position where the original irradiation should be performed, and the observation image appears to be shaken (hereinafter, image shake). This causes a decrease in image quality and measurement accuracy.

  The excitation force acting on the lens barrel 2 and the stage 5 includes an input by the floor vibration 14 and the environmental sound 15 and an input when the stage 5 moves and stops. When the vibration of the ion pump 8A is excited by these inputs, it becomes a vibration source for vibrating the lens barrel 2 and the stage 5. The attenuation of the ion pump 8A itself is small, and a long time is required until the residual vibration after the stage 5 moves and stops is attenuated.

  FIG. 2 is a diagram showing natural vibration modes of the ion pump 8A and the lens barrel 2. As shown in FIG. In the orthogonal coordinate system of FIG. 2, the direction parallel to the barrel 2 is the z direction, the direction perpendicular to the barrel 2 and parallel to the cylindrical pipe of the ion pump 8A is the x direction, and the direction perpendicular to the xz plane is the y direction. (Ideal optical axis (beam trajectory when the beam is not deflected)). Further, rotations about the x, y, and z axes are defined as θx, θy, and θz. The main natural vibration mode of the ion pump 8 </ b> A is a mode that rotates around each axis about a joint portion between the cylindrical pipe and the main body as a fulcrum. These natural vibration modes vibrate in the yz plane if the rotational displacement is very small. On the other hand, the main natural vibration mode of the lens barrel 2 is a mode in which the lens barrel 2 is tilted in the x and y directions with the joint portion of the lens barrel 2 and the sample chamber 3 as a fulcrum. In order to control the ion pump 8A, it is necessary to arrange the viscoelastic body 11A in the yz plane, and if there is no hinge 16A, a damping effect is expected against the tilting of the lens barrel 2 in the x direction. Can not.

  FIG. 3 is a view showing an ion pump vibration control device without the hinge 16A. The ion pump vibration control device illustrated in FIG. 3 has a configuration in which a frame 17 fixed to the support plate 12A is firmly fixed on the sample chamber 3 with a bolt or the like. FIG. 4 is a diagram showing a deformation when the lens barrel 2 of the charged particle beam apparatus provided with the ion pump damping device without the hinge 16A falls in the y direction. When the lens barrel 2 falls in the y direction, the ion pump 8A and the ion pump vibration control device face the direction of the lens barrel 2 following the deformation of the lens barrel 2, so it is difficult to shear the viscoelastic body 11A. is there.

  FIG. 5 is a view showing a deformation when the lens barrel 2 of the charged particle beam apparatus having the ion pump vibration control apparatus without the hinge 16A falls in the x direction. When the lens barrel 2 falls in the x direction, the viscoelastic body 11A is increased in tensile and compressive deformation in the thickness direction and deformation of the frame 17 and cannot be effectively attenuated. If the frame 17 can be supported by a support member that can be rotated or bent along with the inclination of the lens barrel 2, the tensile and compressive deformation in the plate thickness direction of the viscoelastic body 11 </ b> A is suppressed, and the frame 17 is efficiently deformed in the shear direction. It becomes possible.

  FIG. 6 shows a configuration in which the frame 13 is supported by hinges 16A and 16B that can rotate about the y-axis. Although the width and number of hinges are not limited, it is desirable to support the frame 13 with a certain width in the y direction in order to avoid a decrease in rotational rigidity around the x axis. The support member having rotation or bending deformation may have the configuration shown in FIGS.

  FIG. 7 shows a configuration in which the frame 13 is supported by a bearing and a shaft that can rotate about the y-axis. By making the shafts 19A and 19B pass through the bearings 18A and 18B fixed to the sample chamber 3 and the bearing holes 20A and 20B provided in the frame, the frame 13 can be inclined around the y-axis. Become. Further, considering that the frame 13 may be tilted following the tilt of the lens barrel 2, the form of deformation may be not only rotational deformation but also bending deformation. As shown in FIG. 8, by attaching support members 21A and 21B having a smaller thickness and lower rigidity than the frame 13, the support members 21A and 21B are bent and deformed in the x direction, and the frame 13 is inclined in the x direction. It becomes possible.

  FIG. 9 is an example of an FEM analysis result showing the usefulness of the tilt allowing member such as a hinge or a rotation mechanism. The mode damping ratio in the natural vibration mode of the ion pump and the lens barrel is plotted on the basis of the mode damping ratio when the ion pump damping device without the tilt allowing member is used. By making the frame of the ion pump damping device highly rigid, the mode damping ratio in the natural vibration mode of the ion pump has increased significantly, but in the natural vibration mode of the lens barrel, the mode damping ratio has decreased. . On the other hand, in the proposed structure that supports the rotation of the frame, the mode damping ratio in the natural vibration mode of the lens barrel has increased to nearly double while maintaining the mode damping ratio in the natural vibration mode of the ion pump, and the tilt is allowed. The usefulness of the member can be confirmed.

  FIG. 10 is a diagram illustrating another example of the charged particle beam apparatus including the tilt allowing mechanism. One end of the frame 22 is coupled to the support plate 12 </ b> A, and the other end is fixed to the sample chamber 3. The frame 22 has a slit shape with a small plate thickness in a part in the z direction, and the bending deformation increases at the slit position where the bending rigidity decreases. When the lens barrel 2 is tilted in the x direction, the amount of deformation of the viscoelastic body 11A, the amount of deformation in the compression direction, and the amount of deformation in the shear direction vary depending on the slit position. The slit position is preferably arranged so that the shear deformation of the viscoelastic body 11A is maximized. FIG. 11 can be considered as a configuration example that facilitates the inclination of the frame by locally reducing the rigidity of the frame itself as described above. One end of the frame 23 is coupled to the support plate 12 </ b> A, and the other end is fixed to the sample chamber 3. The frame 23 has a shape in which a part of the frame having a uniform thickness is locally bent. The amount of deflection of the frame 22 increases from the bent portion, and the followability to the inclination of the lens barrel 2 in the x direction is increased as compared with the case where there is no bent portion.

  FIG. 12 is a diagram showing still another example of the charged particle beam apparatus including the tilt allowing mechanism. In the present embodiment, an example will be described in which a plurality of support members (a plurality of frames) and a plurality of tilt allowing portions (hinges arranged at different positions in the height direction of the lens barrel) are provided. The lower frame 25 is rotatably supported by the sample chamber 3 via hinges 16A and 16B, the upper end of the lower frame 25 and the lower end of the upper frame 24 are rotatably supported by hinges 26A and 26B, and the upper end of the upper frame 24 is supported by the support plate 12A. It becomes a combined configuration. Since there are two rotation support positions in the z direction, the degree of freedom of deformation of the upper frame 24 is increased. Accordingly, it is possible to deform the viscoelastic body 11A in the shear direction while suppressing the deformation amount in the thickness direction of the viscoelastic body 11A as compared with the case where there is one rotation and bending support member in the z direction. Although the support member shown in FIG. 12 has a hinge structure, the above-described rotation support member, bending support member, and locally different frame members may be freely combined. Further, the hinges 26A and 26B may be directly attached to the support plate 12A without using the upper frame 24. There are no restrictions on the number of frames and support members, and a plurality of frames and support members may be installed in the z direction.

  FIG. 13 is a diagram illustrating still another example of the charged particle beam apparatus including the tilt allowing mechanism. The ion pumps 8 </ b> A and 8 </ b> B are attached in the x direction of the lens barrel 2 at different distances from the sample chamber 3 in the z direction. The lower frame 28 is rotatably supported by the sample chamber 3 via hinges 16A and 16B, the lower end of the upper frame 27 is supported by bending support members 29B and 29C on the + x side of the upper surface of the lower frame 28, and the upper end of the upper frame 27 is It is coupled to the support plate 12A. The support plate 12B is coupled to the −x side of the upper surface of the lower frame 28 via a bending support member 29A. By using a common frame corresponding to each of the ion pumps 8A and 8B as in the lower frame 28, the number of parts can be reduced. You may attach the flame | frame corresponding to each ion pump, without making a flame | frame common.

1 charged particle source 2 lens barrel 3 sample chamber 4 sample 5 stage 6 vibration isolation mount 7 mount 8A, 8B ion pump 9 charged particle beam 10A, 10B support plate 11A, 11B viscoelastic body 12A, 12B support plate 13 frame 14 floor vibration 15 Ambient sound 16A, 16B Hinge 17 Frame 18A, 18B Bearing 19A, 19B Shaft 20A, 20B Bearing hole 21A, 21B Bending support member 22 Frame with slit 23 Bending frame 24 Upper frame 25 Lower frame 26A, 26B Hinge 27 Upper frame 28 Lower Frame 29A, 29B, 29C Bending support member

Claims (9)

A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
Before an inclined allowance portion for permitting the inclination of Ki支 support member, the support member is a charged particle beam apparatus characterized that you support the pump above said inclined allowable unit. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
Wherein the support member, the same direction as the inclination direction of the lens barrel, a charged particle beam apparatus characterized in that it comprises a member for selectively tilting the support member. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
The charged particle beam device according to claim 1, wherein the support member has a bent portion that can be tilted in the same direction as the lens barrel when the lens barrel is tilted. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
The charged particle beam device according to claim 1, wherein the support member has a lower rigidity than other portions of the support member, and has a deforming portion that bends the support member as the lens barrel is inclined. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
The charged particle beam device according to claim 1, wherein the support member is rotatable and includes a rotating portion that bends the support member as the lens barrel is inclined. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
The support member includes a first inclined tolerance portion that allows at least a first divided support member and is configured by the second split support member Rutotomoni, inclined relative to the sample chamber of the first support member, said first 2. A charged particle beam apparatus comprising: a second support member and a second tilt allowing portion that allows tilt with respect to the first support member. In claim 6,
The charged particle beam apparatus, wherein the first divided support member and the second divided support member are arranged at different height positions of the lens barrel. A sample chamber in which the sample is placed, a stage on which the sample is mounted, a lens barrel for irradiating the sample with a charged particle beam, a pump for evacuating the interior of the lens barrel, and the pump A charged particle beam apparatus including a support member,
A charged particle beam apparatus comprising a plurality of the pumps and provided with an inclination allowing portion for allowing the support member to be inclined for each of the pumps. In claim 8,
A charged particle beam apparatus comprising: a lower support member that supports an inclination permission portion provided for each of the pumps; and a lower support member inclination permission portion that supports the lower support member so as to be tiltable.