Objective lens and charged particle beam device including the same

Abstract

To provide an objective lens and a charged particle beam device including the objective lens.SOLUTION: An objective lens of a charged particle beam device that converges and emits a charged particle beam onto a sample, includes: a first electrode exposing and facing the sample; a second electrode converging the charged particle beam onto the sample; a third electrode having a conical tip, and a body part extending from the tip; and a fourth electrode located on the body part of the third electrode. The first electrode, the second electrode, the third electrode, and the fourth electrode each have a through hole. When the electrodes receive voltage, the charged particle beam is emitted onto the sample through the through holes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure generally relates to an objective lens and a charged particle beam device including the same. [Background technology]

[0002] Charged particle beam devices are devices that image and irradiate charged particles emitted from a charged particle source onto the surface of a sample via a charged particle optical system using a magnetic field or an electric field to grasp the characteristics of the sample. Charged particle beam devices are widely used in the fields of materials science, nanoscience, electronics, and other fields. Microscopes based on charged particle beam devices have excellent spatial resolution, so they can observe fine structures such as thin films grown on substrates, nanotubes, plasmon structures, and atomic arrangements of samples that cannot be observed with optical microscopes. Charged particle beam devices can also observe the fine structures of biological samples such as cells, and grasp the crystal structures of samples through electron beam diffraction images.

[0003] Among charged particle beam devices, a scanning electron microscope (SEM) is a device that uses an electron source as a charged particle source, which corresponds to the light source of an optical microscope, to focus and scan an electron beam on a sample, detect signal electrons, and form a microscope image. Recently, there has been a lot of interest in the research of scanning electron microscopes for observation under low-energy electron beam conditions that can improve the information that can be obtained from the surface of a sample and prevent charging and damage of the sample.

[0004] Low energy electron beams can cause problems in the resolution of charged particle beam devices due to the large chromatic aberration caused by the energy spread or the large diffraction aberration caused by the wavelength of the electron beam. To improve this, objective lenses with low aberration coefficients that can reduce the focal distance to the sample and improve the resolution, and scanning electron microscopes including the same, have been developed.

[0005] On the other hand, the sample for scanning electron microscope is generally 1×10 -3 ~10 -4 The specimen is placed in a vacuum sample chamber that is evacuated to a high vacuum of about 100 Pa. However, at this level of vacuum, the sample chamber contains hydrocarbon gases, and when the electron beam is irradiated onto the specimen, contamination occurs frequently due to the adhesion of carbides formed by the decomposition of the hydrocarbon gases. Summary of the Invention [Problem to be solved by the invention]

[0006] A scanning electron microscope objective lens has a detector located above the objective lens, which detects signals such as secondary electrons and backscattered electrons that are attracted into the objective lens to form a microscope image.

[0007] However, secondary electrons drawn into the objective lens collide with the electrodes, reproducing unwanted secondary electrons and generating noise, thereby degrading image quality and ultimately damaging and contaminating the electrodes and detectors.

[0008] One of the problems to be solved by this embodiment is to eliminate the above-mentioned drawbacks of the conventional technology, and to provide an objective lens for a charged particle beam device that can prevent secondary electrons drawn into the objective lens from colliding with an electrode and reproducing undesired secondary electrons. [Means for solving the problem]

[0009] This embodiment is an objective lens of a charged particle beam device that focuses and irradiates a charged particle beam on a sample, the objective lens including a first electrode that is exposed and faces the sample, a second electrode that focuses the charged particle beam on the sample, a third electrode having a conical tip and a main body extending from the tip, and a fourth electrode located in the main body of the third electrode, each of the first electrode, the second electrode, the third electrode, and the fourth electrode including a through hole, and a voltage is supplied so that the charged particle beam is irradiated to the sample through the through hole.

[0010] According to any aspect of this embodiment, the first electrode and the second electrode have the conical tip and a main body extending from the tip, the second electrode is positioned at a distance within the first electrode, and the third electrode is positioned at a distance within the second electrode.

[0011] According to any aspect of this embodiment, the fourth electrode is equipped with a detector that detects secondary electrons and backscattered electrons formed when the charged particle beam is irradiated onto the sample, and the fourth electrode is positioned at a position where detection efficiency is highest, regardless of the shapes and positions of the first electrode, the second electrode, and the third electrode.

[0012] According to any aspect of this embodiment, the third electrode further includes a flange extending from a main body portion of the third electrode, the first electrode further includes a first electrode insulator connected to the flange, and the second electrode further includes a second electrode insulator connected to the flange.

[0013] According to any aspect of this embodiment, a voltage corresponding to either the distance between the first electrode and the sample or the energy of the charged particle beam is supplied to the second electrode.

[0014] According to any aspect of the present embodiment, a voltage difference of 50 V or less is formed between the third electrode and the fourth electrode.

[0015] According to any aspect of the present embodiment, the voltage supplied to the second electrode is independent of the voltage supplied to the third electrode.

[0016] According to any aspect of this embodiment, the objective lens is a scanning electron microscope (SEM) objective lens.

[0017] Another embodiment is an objective lens of a charged particle beam device that focuses and irradiates a charged particle beam onto a sample, the objective lens including: a first electrode having a conical tip and a body extending from the tip, exposed and facing the sample; a second electrode having a conical tip and a body extending from the tip, positioned within the first electrode; a third electrode having a conical tip and a body extending from the tip, positioned within the second electrode; and a fourth electrode positioned in the body of the third electrode, each of the first electrode, the second electrode, the third electrode, and the fourth electrode including a through hole, and a voltage is supplied so that the charged particle beam is irradiated onto the sample through the through hole.

[0018] According to any aspect of this embodiment, the fourth electrode is equipped with a detector that detects secondary electrons and backscattered electrons formed when the charged particle beam is irradiated onto the sample, and the fourth electrode is positioned at a position where detection efficiency is highest, regardless of the shapes and positions of the first electrode, the second electrode, and the third electrode.

[0019] According to any aspect of this embodiment, the tip of the first electrode, the tip of the second electrode, and the tip of the third electrode each include an end portion that is parallel to each other, and a thickness of the end portion of the tip of the first electrode is greater than 0 and less than or equal to 3 mm.

[0020] According to any aspect of this embodiment, the distance between the first electrode and the second electrode is greater than 0 mm and equal to or less than 4 mm.

[0021] According to any aspect of the present embodiment, the through holes formed in the first electrode, the second electrode, and the third electrode have a diameter of 3 mm or more.

[0022] According to any aspect of this embodiment, the objective lens is a scanning electron microscope (SEM) objective lens.

[0023] Another embodiment is a charged particle beam device including a charged particle source, one or more condenser lenses that focus a charged particle beam, an objective lens that irradiates a sample with the charged particle beam, and a detection unit that detects secondary electrons and backscattered electrons formed from the sample, wherein the objective lens includes: a first electrode having a conical tip portion with a through hole formed therein and a body portion extending from the tip portion, the first electrode being exposed and facing the sample; a second electrode having a conical tip portion with a through hole formed therein and a body portion extending from the tip portion, the second electrode being located within the first electrode; a third electrode having a conical tip portion with a through hole formed therein and a body portion extending from the tip portion, the second electrode being located within the second electrode; and a fourth electrode located in the body portion of the third electrode, the fourth electrode having a through hole formed therein.

[0024] According to any aspect of this embodiment, the detection unit includes a first detection unit that detects the secondary electrons and backscattered electrons, and a second detection unit that detects the secondary electrons and backscattered electrons that have passed through the first detection unit.

[0025] According to any aspect of this embodiment, the first detection unit is attached to the fourth electrode and is positioned at a position where the detection efficiency of secondary electrons and backscattered electrons is highest, regardless of the shapes and positions of the first electrode, the second electrode, and the third electrode.

[0026] According to any aspect of this embodiment, a voltage corresponding to any one of the distance between the first electrode and the sample and the energy of the charged particle beam is supplied to the second electrode.

[0027] According to any aspect of the present embodiment, the voltage supplied to the second electrode is independent of the voltage supplied to the third electrode.

[0028] According to any aspect of the present embodiment, a voltage difference of 50 V or less is formed between the third electrode and the fourth electrode.

[0029] According to any aspect of this embodiment, the distance between the first electrode and the second electrode is 4 mm or less, the thickness of the tip of the first electrode is 3 mm or less, and the diameter of the through holes formed in the first electrode, the second electrode, and the third electrode is 3 mm or more.

[0030] According to any aspect of this embodiment, the charged particle beam device is any one of an analysis device and a sample processing device including a scanning electron microscope and a spectrometer that performs energy analysis of an electron beam. Effect of the Invention

[0031] According to this embodiment, contamination caused by secondary electrons generated on the surface of the detector colliding with an electrode having a high potential is suppressed, and deterioration of the performance of the objective lens is reduced, enabling stable use for a long period of time. [Brief description of the drawings]

[0032] [Figure 1] 1 is a block diagram showing an overview of a charged particle beam device including an objective lens according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an overview of an objective lens. [Diagram 3] 2 is a diagram illustrating an example of a connection relationship with a drive power supply unit that supplies drive power required for the operation of the charged particle beam device according to the present embodiment. FIG. [Figure 4] 4 is a diagram showing an example of calculation of the trajectory and axial potential of a primary electron beam in an electrostatic objective lens portion in the charged particle beam device of the present embodiment. FIG. [Diagram 5] FIG. 2 is a schematic diagram showing a first electrode, a second electrode, and a third electrode according to the present embodiment, and parameters of the electrodes. [Figure 6] FIG. 13 is a diagram showing the spherical aberration (Cs) of the objective lens according to normalized parameter values ​​of the first electrode, the second electrode, and the third electrode. [Figure 7]FIG. 13 is a diagram showing the chromatic aberration (Cc) of the objective lens according to normalized parameter values ​​of the first electrode, the second electrode, and the third electrode. [Figure 8] FIG. 1A shows an example of the results of calculating the trajectory of secondary electrons generated on the surface of a sample in the objective lens section of a conventional charged particle beam device, and FIG. 1B shows an example of the results of calculating the trajectory of secondary electrons generated on the surface of a sample in the objective lens section of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. Fig. 1 is a block diagram showing an overview of a charged particle beam device 10 including an objective lens according to the present embodiment. Referring to Fig. 1, the charged particle beam device 10 according to the present embodiment includes a charged particle source 110, one or more condenser lenses 310, 320 for focusing a charged particle beam, an objective lens 500 for irradiating a sample with the charged particle beam, and detection units 610, 620 for detecting backscattered electrons generated from the sample. The objective lens 500 includes a first electrode 510 having a conical tip with a through hole formed therein and a body extending from the tip, the first electrode 510 being exposed and facing the sample, a second electrode 520 having a conical tip with a through hole formed therein and a body extending from the tip, the second electrode 520 being located within the first electrode, a third electrode 530 having a conical tip with a through hole formed therein and a body extending from the tip, the third electrode 530 being located within the second electrode 520, and a fourth electrode 540 being located in the body of the third electrode 530 and having a through hole formed therein.

[0034] The charged particle beam device 10 illustrated in Fig. 1 is a scanning electron microscope (SEM) and may further include a spectrometer 910 and a lower detector 920. Secondary electrons and backscattered electrons generated from a sample are incident on the spectrometer 910 and their energies are analyzed to detect elements, chemical bond states, interband transitions, phonons, or molecular vibration states on the sample surface. Some of the secondary electrons and backscattered electrons generated from the sample are detected by the lower detector 920.

[0035] Other embodiments of the charged particle beam device not shown may include focused ion beam optics (FIB optics) and a lower detector. The focused ion beam optics can be switched between an inclined state with respect to a stage on which a sample is placed and a vertical state with respect to the stage. The focused ion beam can etch a sample or deposit a film on the sample, and can process the sample in a micrometer-scale region of interest (RoI). When processing a sample with a focused ion beam, the surface of the sample can be arranged so that the focused ion beam optics is vertical to the sample. According to such an embodiment, the charged particle beam device can function as a sample processing device, and a scanning electron microscope having an electrostatic objective lens can observe a region to be processed with an ion beam at a high magnification without moving the sample. The charged particle beam device illustrated in FIG. 1 may be any one of an analysis device including a scanning electron microscope and a spectrometer that performs energy analysis of an electron beam, and a sample processing device including a focused ion beam optics.

[0036] 1, an electron source 110 includes a filament 111, a suppressor electrode 113, an extractor electrode 115, and an electron source vacuum pump 119. The electron source vacuum pump 119 forms the inside of the electron source 110 at a desired vacuum level.

[0037] The filament 111 generates charged particles. In one embodiment, the filament 111 may be a thermionic element that is heated to emit electrons. When a current is applied to the filament 111, the filament 111 is heated to emit electrons. As one example, the filament may be made of any one of lanthanum hexaboride (LaB6) single crystal, cerium hexaboride (CeB) single crystal, zirconia-coated tungsten (ZrO-W), and tungsten.

[0038] A suppressor electrode 113 prevents the generated charged particles from being emitted in any direction, and an extractor electrode 115 extracts the charged particles in a desired direction.

[0039] As an embodiment, the charged particle beam device 10 may further include a beam electrode 210 that determines the energy of the charged particle beam B emitted from the electron source 110. The beam electrode 210 may be connected to a beam tube 200 that forms a path along which the charged particle beam B travels. As an embodiment, the inside of the beam tube 200 may be formed to a desired degree of vacuum by the third region pump 142 and the second region pump 144.

[0040] In the illustrated embodiment, the charged particle beam device 10 includes a first condenser lens 310 and a second condenser lens 320. The first condenser lens 310 is formed by winding a coil 314 in a yoke 312 having a gap. The magnetic flux formed by the coil 314 flows out through the gap formed in the yoke 312, and thus acts as a lens for focusing the charged particle beam B. The beam diameter of the charged particle beam B is limited by the first condenser lens 310 and the aperture 330, and the current of the charged particle beam is determined. As an embodiment, the first condenser lens 310 may further include an optical axis aligner 316 that controls the charged particle beam so as to coincide with the optical axis of the first condenser lens 310.

[0041] The second condenser lens 320 is formed by winding a coil 324 inside a yoke 322 having a gap. A magnetic flux formed by the coil 324 flows out through a gap formed in the yoke 322, and thus acts as a lens that converges the charged particle beam B. The second condenser lens 320 controls a convergent angle at which the charged particle beam B is converged on the sample. In one embodiment, the second condenser lens 320 may further include an optical axis aligner 326 that adjusts the charged particle beam so as to coincide with the optical axis of the second condenser lens 320.

[0042] The charged particle beam B that passes through the openings formed in the detector cover 410 and the second upper detector 620 is corrected for astigmatism by a stigmator 710, and is scanned at a low magnification by a subscan 810. As described later, the charged particle beam B is scanned at a high magnification by a main scan 820 and irradiated onto a sample.

[0043] Fig. 2 is a diagram showing an overview of the objective lens 500. Referring to Fig. 1 and Fig. 2, the objective lens 500 includes a first electrode 510, a second electrode 520, a third electrode 530, and a fourth electrode 540, and a charged particle beam B incident on the objective lens 500 is focused and irradiated on a sample by an electric field formed by voltages applied to the first electrode 510, the second electrode 520, the third electrode 530, and the fourth electrode 540.

[0044] The first electrode 510, the second electrode 520, the third electrode 530, and the fourth electrode 540 are arranged to overlap with a gap therebetween, and are electrically insulated from each other by their respective insulators. The first electrode 510, the second electrode 520, the third electrode 530, and the fourth electrode 540 may be formed of a conductive material. In one embodiment, the first electrode 510, the second electrode 520, and the third electrode 530 include a cylindrical body and a cone-shaped tip connected to the body. Each of the tips has a terminal portion formed parallel to each other with a thickness, and the tip has a through hole H formed therein to be able to irradiate a charged particle beam B toward a sample.

[0045] In an embodiment not shown, the first electrode, the second electrode, and the third electrode include a body having a polygonal cross-section and a polygonal pyramid end connected to the body, with a through hole formed in the end through which a charged particle beam can be irradiated toward the sample.

[0046] The third electrode 530 is connected to the beam tube 200. In addition, the third electrode 530 can be electrically connected to the beam electrode 210 via the beam tube 200.

[0047] The third electrode 530 may further include a flange F extending from the body of the third electrode. The body of the first electrode 510 may be connected to the flange F via a first electrode insulator 512, and electrical insulation between them is maintained. The body of the second electrode 520 may be connected to the flange F via a second electrode insulator 522, and electrical insulation between them is maintained. In addition, the flange F may be fixed to a partition wall of the charged particle beam device 10 by a third electrode insulator 532.

[0048] The fourth electrode 540 may be disposed within the body of the third electrode 530. The fourth electrode 540 may be disposed within the body of the third electrode 530 while being insulated by a fourth electrode insulator 542. As in the illustrated embodiment, the top shape of the fourth electrode 540 connected to the fourth electrode insulator 542 may correspond to the cross-sectional shape of the beam tube 200 and / or the cross-sectional shape of the third electrode 530. The fourth electrode 540 may further include an opening and a protruding structure in which the opening extends along the beam path of the charged particle beam B, and the first upper detector 610 may be located around the protruding structure. In one embodiment, the fourth electrode 540 and the first upper detector 610 may be coupled to each other. In one embodiment, the diameter of the opening may be 2 mm or less.

[0049] According to the conventional technology, the detector is disposed on the innermost electrode, and there is a correlation between the shape of the electrode and the position of the first upper detector. That is, since the scanning electron microscope has a high spatial resolution, there is a correlation between the shape of the electrode that minimizes the beam diameter of the primary electron beam irradiated on the sample and the mounting position of the detector that provides high detection performance. This means that there is a trade-off between the spatial resolution and the high detection performance of the first upper detector, making it difficult to achieve both performances.

[0050] However, according to the present embodiment, the fourth electrode 540 is provided, and the position of the first upper detector 610 and / or the fourth electrode 540 can be arranged independently of the shapes and positions of the first electrode 510, the second electrode 520, and the third electrode 530. Therefore, the position where the fourth electrode 540 and / or the first upper detector 610 is arranged may be the position having the highest detection efficiency, regardless of the shapes of the first electrode 510, the second electrode 520, and the third electrode 530.

[0051] The first upper detector 610 can detect secondary electrons and backscattered electrons having a widened trajectory caused by irradiation of the sample with the charged particle beam B, and can be arranged at a position where the detection efficiency is optimal, regardless of the shape and arrangement of the other electrodes. The second upper detector 620 detects secondary electrons and backscattered electrons that have passed through the opening of the fourth electrode.

[0052] A main scanner 820 may be disposed on the outer peripheral surface of the first electrode 510. As described above, the main scanner 820 performs high-magnification beam scanning on the charged particle beam B focused via the objective lens 500. Therefore, high-precision scanning of the charged particle beam B can be performed by the sub-scanner 810 disposed along the path of the charged particle beam B in the beam tube 200 and the main scanner 820 performing high-magnification beam scanning.

[0053] The sample may be placed in a first region V1 where a first vacuum level is maintained together with the objective lens 500, and may be placed on a stage. In one embodiment, the stage may be a five-axis stage capable of controlling the XYZ position, rotation, and tilt of the sample, and the sample placement portion of the stage may be formed of an insulator to cut off electrical connection with the sample.

[0054] In one embodiment, the charged particle beam device 10 is divided into a first region V1 maintained at a first vacuum degree, a second region V2 maintained at a second vacuum degree, a third region V3 maintained at a third vacuum degree, and a fourth region V4 maintained at a fourth vacuum degree, and are evacuated to different vacuum degrees.

[0055] In the illustrated embodiment, the fourth region V4 may be an internal region of the electron source 110 and can be distinguished from the third region by an orifice O having an opening. The fourth region V4 is vacuum pumped to a volume of 1×10 by an electron source vacuum pump 119 included in the electron source 110. -8 A vacuum level of the order of Pa can be maintained.

[0056] The third region V3 can be differentiated from the second region V2 by the detector cover 410 and differentially pumped. The third region V3 is pumped by the third region pump 142 to a volume of 1×10 -7 A vacuum level of the order of Pa can be maintained.

[0057] The second region V2 can be separated from the first region V1 by the opening of the fourth electrode 540 and can be differentially pumped. The second region V2 is pumped by the second region pump 144 to a volume of 1×10 -6 The first region V1 in which the sample is placed can be evacuated by the first pump 146 to a vacuum level of 1×10 -3 ~1×10 -4 The vacuum level Pa can be maintained at a desired vacuum level in each region. As described above, each region can be differentially evacuated by a pump located in each region to maintain the desired vacuum level.

[0058] 3 is a diagram illustrating a connection relationship with a driving power supply unit 1000 that supplies driving power required for the operation of the charged particle beam device 10 according to the present embodiment. Referring to FIG. 1 and FIG. 3, the driving power supply unit 1000 may include an electron source driving power supply unit 1010 that supplies driving power to the electron source 110, and an objective lens driving power supply unit 1020 that supplies voltage to an electrode included in the objective lens and a sample. A user can control the driving power supply unit 1000 through a user terminal 1030 to control the charged particle beam device 10. Data related to secondary electrons and backscattered electrons detected by the charged particle beam device 10 can be supplied to a calculation device for calculation and processing, and can be imaged and displayed to a user through the user terminal 1030.

[0059] In one embodiment, the electron source driving power supply unit 1010 includes a filament current supply unit I fil , suppression voltage V sup The suppression voltage supply V sup , and the extraction voltage V for extracting charged particles to the extractor electrode 115 ext The extraction voltage supply V ext The filament current I fil , suppression voltage V sup and the extraction voltage V ext is the acceleration voltage V that determines the initial energy of the charged particle beam B. ACC The signal is supplied superimposed on the

[0060] As one embodiment, the objective lens driving power supply unit 1020 may include a first electrode driving power supply unit V1, a second electrode driving power supply unit V2, a third electrode driving power supply unit V3, and a fourth electrode driving power supply unit V4 that are connected to the first electrode 510, the second electrode 520, the third electrode 530, and the fourth electrode 540, respectively, and supply voltages, and a sample driving power supply unit V0 that supplies voltage to the sample.

[0061] The charged particle beam B is focused and supplied to the sample by an electric field formed by voltages applied to the first electrode 510, the second electrode 520, the third electrode 530, and the fourth electrode 540 by the first electrode driving power supply unit V1, the second electrode driving power supply unit V2, the third electrode driving power supply unit V3, and the fourth electrode driving power supply unit V4, respectively.

[0062] A user can control the energy of the charged particle beam irradiated to the sample via the user terminal 1030. As an embodiment, the energy of the charged particle beam irradiated to the sample can be controlled. As an example, the user controls the third electrode drive power supply unit V3 via the user terminal 1030 to supply a third electrode drive voltage V3 to the third electrode 530, and controls the first electrode drive voltage V1 supplied to the first electrode 510 to be supplied at a voltage lower than the third electrode drive voltage V3.

[0063] In this way, by controlling the magnitude relationship between the first electrode driving voltage V1 supplied to the first electrode 510 and the third electrode driving voltage V3 supplied to the third electrode 530, the energy with which the charged particle beam is irradiated onto the sample can be controlled.

[0064] In one embodiment, the first electrode voltage V1 supplied to the first electrode 510 may be the same as the sample voltage V0 supplied to the sample. In another embodiment, the first electrode voltage V1 may be set to a potential between the sample voltage (V0) -50V and the sample voltage (V0) +50V.

[0065] The second electrode focuses the charged particle beam B on the sample. In one embodiment, a user can control the second electrode drive power supply unit V2 with the user terminal 1030 to adjust the voltage V2 applied to the second electrode 520, thereby focusing the charged particle beam B on the sample in accordance with the working distance WD between the objective lens 500 and the sample or the energy of the electron beam.

[0066] Most of the secondary electrons and backscattered electrons formed when the charged particle beam B is irradiated onto the sample are drawn into the objective lens 500 and detected by the first upper detector 610. The fourth electrode 540 has a cylindrical portion on which the first upper detector 610 is attached, protruding toward the sample, and an opening is provided at the center. This cylindrical portion reduces the solid angle of the primary electron beam with respect to the detector, and reduces abnormal trajectory deflection of the primary electron beam caused by charging of the insulating detector surface. The secondary electrons and backscattered electrons that pass through the opening of the fourth electrode 540 proceed and diverge upward of the beam tube, and are detected by the second upper detector.

[0067] FIG. 4 shows an example of calculation of the trajectory and axial potential of the primary electron beam in the electrostatic objective lens portion in the charged particle beam device of this embodiment.

[0068] The potentials V1 to V4 applied to the first to fourth electrodes of the objective lens are 1000V, 8155V, 4000V, and 4000V, respectively, and the sample potential V0 is 1000V, which are relative values ​​with the electron source 110 as the 0V reference. As illustrated, the same potential is applied to the third and fourth electrodes. This provides the advantage that contamination and damage to the electrodes and detector can be prevented and detection performance can be improved, as described below.

[0069] 4, in the range of -150 to -50 mm on the z axis corresponding to the internal region of the objective lens 500, the axial potential is determined by the potentials of the third and fourth electrodes and is 4000 V. A voltage of 8155 V is applied to the second electrode 520, and is adjusted so that the charged particle beam B is focused on the sample. The voltage V1 of the first electrode 510 is set to 1000 V, which is the same potential as the sample voltage V0.

[0070] The trajectory of the primary electron beam must be converged onto the optical axis at a position of -150 mm by the condenser lenses 310 and 320, and then enter the objective lens 500 and be focused on the surface of the sample at the position of Z=0 mm.

[0071] In the objective lens 500, the electron beam diverges due to the acceleration effect between the third electrode 530 and the second electrode 520, and converges due to the deceleration effect near the boundary between the second electrode 520 and the first electrode 510, and is focused on the sample.

[0072] In the electrostatic objective lens 500 of this embodiment, the second electrode voltage V2 applied to the second electrode 520 can be adjusted to focus the electron beam on the sample, and the working distance WD between the objective lens 500 and the sample and the focusing conditions when the energy of the electron beam are changed can be controlled. In addition, the second electrode voltage V2 supplied to the second electrode 520 can be set independently of the third electrode voltage V3 supplied to the third electrode 530 and the potential of the beam tube 200. Even when the second electrode voltage V2 is changed to adjust the focusing, the third electrode voltage V3 and the fourth electrode voltage V4 that affect the detection efficiency can be kept constant, so that the signal detection efficiency of the electron beam can be kept constant.

[0073] There are two possible methods for applying voltages to realize the axial potential shown in the example. In the first method, when the sample is grounded (0 V) and the beam tube 200 inside the column is set to a positive potential, the following voltages are applied: V0=0 V, V1=0 V, V2=+7155 V, V3=+3000 V, and V4=+3000 V. The accelerating voltage V applied to the electron source 110 is ACC =-1000V.

[0074] In the second method, when the sample is set to a negative potential and the beam tube 200 inside the column is grounded (0 V), the following voltages are applied: V0 = -3000 V, V1 = -3000 V, V2 = +4155 V, V3 = 0 V, and V4 = 0 V. The accelerating voltage V applied to the electron source ACC =-4000 V. When using a scanning electron microscope alone, both voltage application methods are possible.

[0075] Since the sample side of the spectrometer that performs the above-mentioned energy analysis of the electron beam is often grounded, the first method is preferable for simultaneously operating the scanning electron microscope and the spectrometer.

[0076] Fig. 5 is a schematic diagram showing the first, second and third electrodes according to the present embodiment, and the parameters (dimensional variables) of the electrodes. Fig. 6 is a diagram showing the spherical aberration (Cs, spherical aberration) of the objective lens 500 according to the normalized parameter values ​​of the first, second and third electrodes, and Fig. 7 is a diagram showing the chromatic aberration (Cc, chromatic aberration) of the objective lens 500 according to the normalized parameter values ​​of the first, second and third electrodes.

[0077] 5 to 7, the ends of the first electrode 510, the second electrode 520, and the third electrode 530 may have a cone shape. The angle of the cone is θ OL The ends of the cone formed by the first electrode 510, the second electrode 520, and the third electrode 530 can be cut parallel to each other to form an opening with a diameter D.

[0078] The thickness of the end portion of the first electrode 510 is t1, the thickness of the end portion of the second electrode 520 is t2, and the thickness of the end portion of the third electrode 530 is t3. In the illustrated embodiment, the thickness of the end portion and the thickness of the remaining portion of the electrode are shown to be different from each other, but this is an exemplary embodiment, and the thickness of the end portion and the thickness of the remaining portion of the electrode may be equal to each other. In addition, the distance between the first electrode 510 and the second electrode 520 is g1, and the distance between the second electrode 520 and the third electrode 530 is g2.

[0079] The horizontal axis in Figures 6 and 7 is the normalized parameter value (dimension value), and the vertical axis is the calculated aberration value. For normalization, the formula (relevant value - minimum value) / (maximum value - minimum value) was used. The smaller the aberration value on the vertical axis, the better the performance of the objective lens. For each geometric dimension value, the greater the slope of the graph, the more important the target geometric dimension is.

[0080] For the spherical aberration Cs illustrated in FIG. 6, it can be seen that the thickness t1 of the tip of the first electrode 510 and the diameter D of the electrode opening have a greater influence on the result value than the other parameters, and for the chromatic aberration Cc illustrated in FIG. 7, it can be seen that in addition to these, the spacing g1 between the first and second electrodes is also a parameter that has a greater influence on the result value than the values ​​of the other parameters.

[0081] By setting the desired aberration coefficients and referring to the graphs in Figures 6 and 7, it is possible to determine the geometric dimensions for realizing a high-performance electrostatic lens that is equal to or less than the reference value. Specifically, in order to make the spherical aberration Cs equal to or less than 40 mm and the chromatic aberration Cc equal to or less than 6 mm, it is necessary to make the diameter D of the opening of each electrode equal to or more than 3 mm, the thickness t1 of the tip of the first electrode equal to or less than 3 mm, and the distance g1 between the first electrode and the second electrode equal to or less than 4 mm. Similar calculations can be performed under different beam energy and working distance (WD) conditions to realize a high-performance objective lens with reduced aberrations.

[0082] 6 and 7 show the cone angle θ of the electrostatic objective lens, which is an important design condition. OL We also performed calculations for . Although the dependence is small, it can be seen that the larger the cone angle, the smaller the aberration coefficient and the better the performance of the lens. Using Figures 6 and 7, we can determine the cone angle that meets the specifications for both the electrostatic objective lens of a scanning electron microscope and the objective lens of a spectrometer.

[0083] FIG. 8(a) shows an example of the calculation result of the trajectory of secondary electrons generated on the surface of a sample in the objective lens section of a conventional charged particle beam device. The equipotential surface of the electrostatic lens is shown by a red line, and the trajectory of the secondary electrons is shown by a blue line. As shown in the figure, an equipotential surface is formed between the detector and the electrode, which indicates that a potential difference is formed. Therefore, secondary electrons generated from the sample are accelerated by the potential difference between the electrode and the detector, collide with the electrode, and generate undesired secondary electrons, which are detected by the detector and act as undesired noise. In addition, secondary electrons generated on the surface of the detector collide with the electrode with a high potential, which contaminates the inner wall of the electrode, causing an imbalance in the electric field, which ultimately reduces the performance of the objective lens.

[0084] In the conventional detector, after a certain period of use, the detector and electrodes must be removed and the objective lens must be disassembled for periodic replacement, which is inconvenient and inefficient because the detector and electrodes must be reassembled with precise alignment of their centers with other electrodes.

[0085] Fig. 8(b) shows an example of the result of calculating the trajectory of secondary electrons generated on the surface of the sample in the objective lens unit of this embodiment. Referring to Fig. 8(b), it can be seen that the secondary electrons generated from the sample are drawn into the inside without colliding with the edge, and the detector is positioned higher than in the conventional technology, so that the amount of secondary electrons passing through the aperture is increased, and the detection efficiency is improved.

[0086] In addition, in the conventional technology, a potential difference is formed between the detector and the electrode, and many equipotential lines can be confirmed, but in this embodiment, there is no potential difference or a potential difference of less than 50V is formed between the third electrode and the fourth electrode. That is, as a result, secondary electrons generated from the sample do not collide with the electrodes, so that contamination of the electrodes can be prevented, performance deterioration of the electrostatic lens can be prevented, and long-term stable operation can be achieved. Furthermore, if the potential difference between the fourth electrode and the third electrode is set to +50V or less, secondary electrons generated in the detector completely return toward the upper detector, so that contamination of the electrodes can be more effectively prevented. In one embodiment, the potential difference between the second electrode and the third electrode is 4000V or more, so that if the potential difference between the fourth electrode and the third electrode is about 50V, the potential difference can be ignored.

[0087] In addition, in this embodiment, when replacing the first upper detector 610, even if the fourth electrode 540 is removed, the first upper detector 610 can be easily replaced without the need to remove the second and third electrodes which generate the main lens action, and therefore the maintenance thereof is easy. In order to facilitate understanding of the present invention, the present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary embodiments for implementation, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical scope of the present invention should be determined by the appended claims. [Explanation of symbols]

[0088] 10. Charged particle beam equipment 110 Electron source 111 Filament 113 Suppressor Electrode 115 Extractor Electrode 119 Vacuum pump for electron source 142 Third-range pump 144 4th Zone Pump 146 First Zone Pump 200 Beam Tube 210 Beam Electrode 310 First Condenser Lens 312 York 314 Coil 316 Optical axis aligner 320 Second Condenser Lens 322 York 324 Coil 326 Optical axis aligner 330 Aperture 410 Detector cover 500 Objective Lens 510 1st electrode 512 First electrode insulator 520 2nd electrode 522 Second electrode insulator 530 3rd electrode 532 Third electrode insulator 540 4th electrode 542 4th electrode insulator 610 First Upper Detector 620 Second Upper Detector 710 Stigmator 810 Subscan 820 Main Scan 910 Spectrometer 920 Lower Detector 1000 Drive power supply unit 1010 Electron source drive power supply 1020 Objective lens drive power supply unit 1030 User terminal

Claims

1. An objective lens of a charged particle beam device that focuses and irradiates a charged particle beam on a sample, comprising: The objective lens is a first electrode that is exposed and faces the sample; a second electrode for focusing the charged particle beam onto the sample; a third electrode having a conical tip and a body extending from the tip; a fourth electrode located on a body portion of the third electrode; An objective lens, wherein each of the first electrode, the second electrode, the third electrode, and the fourth electrode includes a through hole, and when a voltage is supplied, the charged particle beam is irradiated onto the sample through the through hole.

2. The first electrode and the second electrode are a conical tip portion and a body portion extending from the tip portion; The second electrode is spaced apart from the first electrode, The objective lens of claim 1 , wherein the third electrode is spaced apart within the second electrode.

3. The fourth electrode is a detector is attached to detect secondary electrons and backscattered electrons formed when the sample is irradiated with the charged particle beam; The fourth electrode is The objective lens according to claim 1 , wherein the first electrode, the second electrode and the third electrode are disposed at positions where detection efficiency of secondary electrons and backscattered electrons is highest, regardless of their shapes and positions.

4. The third electrode is a flange extending from the body portion of the third electrode; the first electrode further includes a first electrode insulator connected to the flange; The objective lens of claim 1 , wherein the second electrode further comprises a second electrode insulator connected to the flange.

5. The second electrode has The objective lens according to claim 1 , wherein a voltage corresponding to either one of the distance between the first electrode and the sample and the energy of the charged particle beam is supplied.

6. The objective lens according to claim 1 , wherein a voltage difference of 50 V or less is formed between the third electrode and the fourth electrode.

7. The objective lens of claim 1 , wherein the voltage supplied to the second electrode is independent of the voltage supplied to the third electrode.

8. The objective lens of claim 1 , wherein the objective lens is a scanning electron microscope (SEM) objective lens.

9. An objective lens of a charged particle beam device that focuses and irradiates a charged particle beam on a sample, comprising: The objective lens is a first electrode having a conical tip and a body extending from the tip, the first electrode being exposed and facing the sample; a second electrode positioned within the first electrode, the second electrode having a conical tip and a body portion extending from the tip; a third electrode located within the second electrode and having a conical tip and a body extending from the tip; a fourth electrode located on a body portion of the third electrode; An objective lens, wherein each of the first electrode, the second electrode, the third electrode, and the fourth electrode includes a through hole, and when a voltage is supplied, the charged particle beam is irradiated onto the sample through the through hole.

10. The fourth electrode is a detector is attached to detect secondary electrons and backscattered electrons formed when the sample is irradiated with the charged particle beam; The fourth electrode is The objective lens according to claim 9 , wherein the first electrode, the second electrode and the third electrode are arranged at positions where detection efficiency of secondary electrons and backscattered electrons is highest, regardless of their shapes.

11. each of the first electrode tip, the second electrode tip, and the third electrode tip includes an end portion parallel to one another; The objective lens of claim 9 , wherein the thickness of the distal end of the first electrode is greater than 0 and less than or equal to 3 mm.

12. The objective lens according to claim 9 , wherein the distance between the first electrode and the second electrode is greater than 0 mm and is equal to or smaller than 4 mm.

13. The objective lens according to claim 9 , wherein the through holes formed in the first electrode, the second electrode, and the third electrode have a diameter of 3 mm or more.

14. The objective lens of claim 9 , wherein the objective lens is a scanning electron microscope (SEM) objective lens.

15. A charged particle beam device, comprising: a charged particle source; and one or more condenser lenses for focusing the charged particle beam; an objective lens that forms an image of the charged particle beam on a sample; a detection unit for detecting secondary electrons and backscattered electrons generated from the sample, The objective lens is a charged particle beam device including: a first electrode having a conical tip portion with a through hole formed therein and a main body portion extending from the tip portion, the first electrode being exposed and facing the sample; a second electrode having a conical tip portion with a through hole formed therein and a main body portion extending from the tip portion, the first electrode being positioned within the first electrode; a third electrode having a conical tip portion with a through hole formed therein and a main body portion extending from the tip portion, the second electrode being positioned within the second electrode; and a fourth electrode positioned in the main body portion of the third electrode, the fourth electrode having a through hole formed therein.

16. The detection unit is a first detector for detecting the secondary electrons and the backscattered electrons; The charged particle beam device according to claim 15 , further comprising: a second detector configured to detect the secondary electrons and backscattered electrons that have passed through the first detector.

17. The first detection unit is attached to the fourth electrode, The charged particle beam device according to claim 16 , wherein the first electrode, the second electrode, and the third electrode are arranged at positions where detection efficiency of secondary electrons and backscattered electrons is highest, regardless of their shapes.

18. The second electrode has The charged particle beam device according to claim 15 , wherein a voltage corresponding to any one of a distance between the first electrode and the sample and energy of the charged particle beam is supplied.

19. The voltage supplied to the second electrode is The charged particle beam device according to claim 18 , wherein the voltage is independent of the voltage supplied to the third electrode.

20. The charged particle beam device according to claim 15 , wherein a voltage difference of 50 V or less is formed between the third electrode and the fourth electrode.

21. The distance between the first electrode and the second electrode is 4 mm or less, The thickness of the tip of the first electrode is 3 mm or less, The charged particle beam device according to claim 15 , wherein the through holes formed in the first electrode, the second electrode, and the third electrode have a diameter of 3 mm or more.

22. 16. The charged particle beam device according to claim 15, wherein the charged particle beam device is any one of an analysis device including a scanning electron microscope and a spectrometer that performs energy analysis of an electron beam and a sample processing device.

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