WO2007129376A1

WO2007129376A1 - Electronic lens

Info

Publication number: WO2007129376A1
Application number: PCT/JP2006/308728
Authority: WO
Inventors: Keizo Yamada; Minoru Matsuzawa
Original assignee: Topcon Corporation
Priority date: 2006-04-26
Filing date: 2006-04-26
Publication date: 2007-11-15

Abstract

Provided is a small-size electronic lens having a small aberration for use in a microscope and an evaluation device using an electronic beam. The electronic lens is characterized in that its characteristic can be modified in a short time without using a complicated correction device. In the electronic lens, a correction electrode (11) is arranged in the vicinity of objective lenses (12, 13) as electrostatic lenses for correcting the aberration. Alternatively, a correction mechanism formed by a magnet is arranged in the vicinity of the objective lenses as magnetic lenses for correcting the aberration.

Description

Specification

Electronic lens

Technical field

[0001] The present invention relates to an electron lens used in a microscope or an evaluation apparatus using an electron beam.

Background art

[0002] Since an electron beam has a wavelength shorter than that of visible light, an electron microscope using an electron beam can observe and measure a finer object than when an optical microscope is used. However, the resolution of an actual electron microscope can only reach a very rough resolution compared to the wavelength of the electron beam used. For example, even if an electron beam with a wavelength of 0.1 A or less is used, a resolution of about 20 A can be obtained.

The reason is that the electron lens for controlling the electron beam to converge to a desired spot diameter has various large aberrations. For this reason, even if the electron beam is converged, it has a wide force ^ corresponding to the magnitude of the aberration, and the resolution becomes rougher than the value that the diffraction limit force is calculated.

By the way, there are two types of typical electronic lenses, electrostatic lenses and electromagnetic lenses (or magnetic lenses), both of which have the above-mentioned aberrations. However, since an electrostatic lens cannot converge an electron beam having a very large spherical aberration compared to an electromagnetic lens to a diameter of several nanometers, an electromagnetic lens is generally used as an objective lens of an electron microscope. Have been used. Here, the operation of the conventional electrostatic lens will be described with reference to the sectional view of the conventional electrostatic lens shown in FIG. 19A and the plan view shown in FIG. 19B. First, the electron beam EB19 is incident on the objective lens 190 with a large diameter. The electron beam EB19 incident on the objective lens 190 is subjected to a force by an electric field formed by the electrode 192 applied with the voltage 195a and the electrode 193 applied with the voltage 195b, and is perpendicular to the equipotential surface 196. It passes through the electrostatic lens while changing the traveling direction, converges to the electron beam diameter 199, and reaches the sample surface (not shown). However, since the equipotential surface 196 has a spherical shape, it acts as a spherical electron lens. As a result, the spherical aberration of the electron lens increases, and the converged electron beam diameter 199 is large. Diameter.

On the other hand, with respect to electromagnetic lenses, in recent years, methods for improving aberrations have begun to be introduced. One of the methods is a method using a multipole, which is a technique for correcting aberrations of an electron lens using a correction device having 12 poles (see, for example, Patent Document 1). Another method is a technique for reducing chromatic aberration, and a method using a spectroscope is known. This is a method of reducing the energy dispersion of the electron beam and eliminating the chromatic aberration by separating the electron beam separately from each other.

[0005] In addition, as a technique for improving the electron microscope, in recent years, the substrate current generated when an electron beam is irradiated onto a sample (semiconductor substrate) is measured, the fine structure of the sample is evaluated, and the semiconductor device manufacturing process is performed. A semiconductor device measuring apparatus (EBSCOPE) to be managed is used (for example, see Patent Document 2). In this apparatus, unlike a conventional electron microscope, it is necessary to irradiate a sample with an electron beam having various beam shapes in which the electron beam is converged to the extreme or is forced. In addition, it is necessary to measure the acceleration voltage of the electron beam in various ways. In this apparatus, an electromagnetic lens is used as the objective lens.

Patent Document 1: Japanese Patent Laid-Open No. 2005-302359

Patent Document 2: JP 2006-19761

Disclosure of the invention

Problems to be solved by the invention

[0006] As described above, attempts have been made to reduce aberration by adding a correction device to an electromagnetic lens. In this case, however, the electron microscope has a complicated structure and in order to completely correct the aberration. There is a problem that a skillful operation technique of the correction device is required. In addition, there is a problem that the cost of the electron microscope increases and convenience decreases.

In addition, by adding a correction device to the electromagnetic lens, the electron beam column becomes very large. As a result, there is a problem in that secondary performance deterioration is likely to occur, which is likely to cause electromagnetic interference that is susceptible to vibration and noise.

[0007] The semiconductor device measuring apparatus (EBSCOPE) as described above has recently been used in the mass production process in a semiconductor device manufacturing factory, and is used for fine structure inspection of semiconductor devices. It is increasingly used to determine process conditions. When considering such an application, the problem that the operation of the correction device is complicated and expensive is a very large practical obstacle.

Also, with conventional electromagnetic lenses, it has been difficult to obtain a wide variety of electron beams required for semiconductor device measurement equipment (EBSCOPE) in a short time. The reason is that a large amount of heat is generated due to the large current required for the operation of the electromagnetic lens, and the amount of current that flows changes due to changes in the characteristics of the electromagnetic lens. This is because the characteristics are bad, and it takes about one hour to stabilize the amount of heat and make the characteristics of the electromagnetic lens steady.

[0008] In order to avoid this problem, a force using a method using an electrostatic lens as the objective lens is considered. As described above, there is a problem that the electrostatic lens has a very large spherical aberration.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small electron lens having a small aberration and capable of changing characteristics without using a complicated correction device in a short time.

Means for solving the problem

[0009] In order to solve the above-described problems, an electron lens according to the present invention includes a correction mechanism that corrects the aberration of an electrostatic lens.

The electron lens according to the present invention is characterized in that the correction mechanism is a correction electrode disposed in the vicinity of the objective lens.

The electron lens according to the present invention is characterized in that the correction electrode has a circular hole.

[0010] Further, the electron lens according to the present invention is characterized in that the correction electrode has a hole having a shape other than a circle.

The electron lens according to the present invention is characterized in that the shape of the hole of the correction electrode is different from the shape of the objective lens.

The electron lens according to the present invention is characterized in that the correction mechanism is an electrode through which an electron formed of a conductive material can pass.

[0011] In the electron lens according to the present invention, the electrode deforms the shape of the conductive material. It is characterized by being formed.

Moreover, the electron lens according to the present invention is characterized in that the electrode has a Fresnel lens shape.

The electron lens according to the present invention is characterized in that a plurality of the electrodes in the shape of a Fresnel lens are arranged in the incident direction of the electron beam.

The electron beam scanning apparatus according to the present invention is characterized in that the electron beam scanning range is expanded using an electron lens.

[0012] In the electron lens according to the present invention, the correction mechanism includes a correction electrode having a set of electrode forces facing a direction substantially perpendicular to the incident direction of the electron beam in the incident direction of the electron beam. It is a multistage lens arranged in a plurality of sets, and is characterized by comprising voltage application means for applying independent voltages to the correction electrodes.

In addition, the electron lens according to the present invention is characterized in that the arrangement angles of the correction electrodes of each set constituting the multistage lens are different.

[0013] In the electron lens according to the present invention, the correction mechanism includes a plurality of correction electrodes having a circular hole and having a concave portion or a convex portion on the circumference of the hole in the incident direction of the electron beam. This is a multi-stage lens superposed on each other, characterized in that it comprises voltage application means for applying independent voltages to the correction electrodes, and the correction electrodes are rotatable.

[0014] Further, the electron lens according to the present invention has a plurality of focal points.

The electron lens according to the present invention is characterized in that the plurality of focal points exist at different positions.

The electron lens according to the present invention is characterized in that the plurality of focal points have a long focal length and a short focal length, respectively.

In addition, the electronic lens according to the present invention includes a correction mechanism that corrects the aberration of the magnetic lens. The electronic lens according to the present invention includes a plurality of ring-shaped fixed magnets having different sizes. It is characterized by being arranged concentrically.

The electron lens according to the present invention is characterized in that the correction mechanism has a plurality of small magnets arranged in a plane. [0016] The electronic lens according to the present invention further includes an electrostatic lens, and the magnetic lens and the electrostatic lens are arranged so that the incident directions of the electron beams are the same.

The electron lens according to the present invention is characterized in that the correction mechanism includes a plurality of holes formed in a support substrate and magnets in one or more of the holes.

In addition, the electron lens according to the present invention is characterized in that the correction mechanism is constituted by a magnet that can rewrite polarity, strength, or both.

[0017] Further, the electron lens according to the present invention is characterized in that the polarity and / or strength of the magnet is rewritten using a magnetic head.

The electron lens according to the present invention is characterized in that the magnetic lens is configured by discretely changing the strength of the magnet.

The electron lens according to the present invention is characterized in that the magnetic lens is configured by continuously changing the strength of the magnet.

The electron beam apparatus according to the present invention is characterized by using the electron lens.

The invention's effect

[0018] According to the present invention, it is possible to change characteristics without using a complicated correction device in a short time, and it is possible to obtain a small electron lens having a very small convergence.

Brief Description of Drawings

FIG. 1 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a first embodiment of the present invention.

FIG. 2 is a sectional view (A) and a plan view (B) of an electron lens according to a first modification of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a second modification of the first embodiment of the present invention.

FIG. 4 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a third modification of the first embodiment of the present invention.

FIG. 5 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a fourth modification of the first embodiment of the present invention.

FIG. 6 is a cross-sectional view (A) and a plan view of an electron lens according to a fifth modification of the first embodiment of the present invention. It is a surface view (B).

FIG. 7 is a sectional view (A) and a plan view (B) of an electron lens according to a sixth modification of the first embodiment of the present invention.

FIG. 8 is a plan view (A) and a plan view separately displayed for each correction electrode in order to show the arrangement angle of each correction electrode of the electron lens according to the seventh modification of the first embodiment of the present invention. (B) and sectional view (C).

FIG. 9 is a cross-sectional view (A) and a plan view (B) of an electron lens according to an eighth modification of the first embodiment of the present invention.

FIG. 10 is a cross-sectional view of an electron lens in which two electron Fresnel lenses of the present invention are stacked.

11 is a cross-sectional view of an electron beam scanning device of an electron microscope using the electron lens shown in FIG.

FIG. 12 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a second embodiment of the present invention.

FIG. 13 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a first modification of the second embodiment of the present invention.

FIG. 14 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a second modification of the second embodiment of the present invention.

FIG. 15 is a plan view of an electron lens and a writing device according to a third modification of the second embodiment of the present invention.

FIG. 16 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a third embodiment of the present invention.

FIG. 17 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a first modification of the third embodiment of the present invention.

FIG. 18 is a cross-sectional view (A) and a plan view (B) of an electron lens according to a second modification of the third embodiment of the present invention.

FIG. 19 is a cross-sectional view (A) and a plan view (B) of a conventional electrostatic lens.

Explanation of symbols

10 Objective lens (main lens) 11 Correction electrode

12 electrodes

13 electrodes

14 Insulator

15 voltage

16 equipotential surface

17 Conventional equipotential surface

18 holes

EB1 electron beam

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

FIG. 1A shows a cross-sectional view of the electron lens according to the first embodiment of the present invention, and FIG. 1B shows a plan view.

As shown in FIG. 1A, this electron lens is composed of an objective lens (main lens) 10, a correction electrode 11, an electrode 12, an electrode 13, an insulator 14, and a hole 18. Operates as an electric lens. The electrode 12 is formed with an objective lens (main lens) 10 formed of a circular cavity. A correction electrode 11 having a hole 18 made of a circular cavity smaller than the size of the objective lens (main lens) 10 is provided at the center of the electrode 13 so as to be electrically insulated from the electrode 13. The correction electrode 11 can locally apply a potential in the vicinity of the objective lens (main lens) 10.

Then, the objective lens (main lens) 10 and the correction electrode 11 are arranged in this order from the incident direction of the electron beam EB1. An insulator 14 is sandwiched between the electrode 12 and the electrode 13, and the distance between the electrode 12 and the electrode 13 can be changed by changing the thickness of the insulator 14. When this electron lens is viewed from above, as shown in FIG. 1B, a correction electrode 11 is installed at the center of the objective lens (main lens) 10 and a hole 18 is formed at the center of the correction electrode 11.

In addition, the correction electrode 11 has a voltage 15a force electrode 12 has a voltage 15b force electrode 13 has a voltage 15 c is applied to each. Each voltage may be any voltage. For example, the voltage of the correction electrode 11 (voltage 15a) and the voltage of the electrode 13 (voltage 15c) may be the same voltage as the electrode 12, the ground potential, or a floating state. .

Next, the operation of the present electron lens will be described.

In the electron lens according to the present embodiment, a correction electrode 11 having a predetermined potential is disposed in the vicinity of the objective lens (main lens) 10. Therefore, the shape of the equipotential surface 16 near the objective lens (main lens) 10 is different from the equipotential surface shape of the objective lens (main lens) 10 alone due to the influence of the potential of the correction electrode 11. It becomes. That is, the potential of the correction electrode 11 affects the conventional equipotential surface formed by the electrodes 12 and 13 to which a voltage is applied, and changes the shape of the equipotential surface.

As a result, the shape of the equipotential surface 16 can be freely changed by adjusting the size, shape, position or potential of the correction electrode 11. Compared to the conventional equipotential surface 17 in the absence of the correction electrode 11, the shape of the equipotential surface 16 in this electron lens is deformed by the presence of the correction electrode 11, and the curvature of each part becomes smaller. ing. As a result, the spherical aberration is smaller than that of the conventional electrostatic lens.

That is, with the structure shown in FIG. 1, an electron lens in which the shape of the electron lens (that is, the equipotential surface shape) is changed to an aspheric shape other than the spherical shape can be realized. For example, if the distance between the objective lens (main lens) 10 and the correction electrode 11 is changed, the degree of the aspherical surface of the electron lens shape (equipotential surface shape) can be changed. In other words, when the distance between them is infinity, the shape of the electron lens (equipotential surface shape) is the spherical shape that the objective lens (main lens) 10 has alone, but the electrode distance is reduced from there. Then, an electron lens is obtained in which the potential of the correction electrode 11 is changed from an equipotential surface shape near the objective lens (main lens) 10 to an aspherical shape.

[0026] The electron beam EB1 incident on the electron lens is affected by the electric field generated by the correction electrode 11, the electrode 12, and the electrode 13, and changes the traveling direction perpendicular to the equipotential surface 16. While converging the beam diameter, the beam heads toward the hole 18 provided in the correction electrode 11. Only the electron beam EB1 passing through the hole 18 passes through the electron lens and reaches the surface of the sample (not shown). The electron beam EB1 has smaller spherical aberration than the conventional equipotential surface 17. Since it converges under the influence of the aspheric equipotential surface 16, it converges to a smaller spot diameter than before.

In addition, since this electron lens does not require a large current to flow unlike conventional electromagnetic lenses, it does not generate heat, and the electron lens characteristics can be changed instantaneously simply by changing the voltage applied to each electrode.

[0027] In the above-described example, the force using the correction electrode 11 having the hole 18 at the center part. The shape of the equipotential surface in the vicinity of the objective lens (main lens) 10 is not necessarily required to have a hole. What is necessary is just to be able to arrange the electrode which can do things.

Further, the position where the correction electrode 11 is provided may be on the objective lens (main lens) 10 or on both the bottom and top and bottom as described in the present embodiment. When the correction electrode 11 is provided on the objective lens (main lens) 10 or both above and below, the electron beam EB1 first passes through the hole 18 provided at the center of the correction electrode 11, so that The beam diameter is equal to or smaller than the diameter of the hole 18 and enters the objective lens (main lens) 10. Therefore, the electron beam EB1 passes only through the central region where the spherical aberration is small, among the equipotential surfaces 16 where the spherical aberration is small due to the aspherical shape, and the diameter of the electron beam EB1 is small. Can be converged more effectively and smaller.

The correction electrode 11 is easily contaminated because it is irradiated with the electron beam EB1. Therefore, a heating means such as a heater may be built in to heat the correction electrode 11.

Next, FIG. 2A shows a cross-sectional view of an electron lens according to a first modification of the first embodiment of the present invention, and FIG. 2B shows a plan view. In the figure, elements common to the constituent elements shown in FIG.

In the above-mentioned semiconductor device measurement system (EBSCOPE), it is used in general scanning electron microscopes (SEM), and not only electron beams with a circular cross section but also various special cross section shapes are used. Use this to observe and measure the sample. However, if the cross-sectional shape of the electron beam is different, the aberration component is different from that of the circular cross-sectional shape. Therefore, it is necessary to correct the aberration in accordance with the cross-sectional shape of the electron beam. In this modification, the required electron beam cross-sectional shape is a star shape as an example. I will explain.

As shown in the cross-sectional view of FIG. 2A, the present electron lens is an electrostatic lens having a structure in which the correction electrode 21 and the hole 28 are changed from the first embodiment. A correction electrode 21 having a star-shaped hole 28 smaller than the size of the objective lens (main lens) 10 is provided in the center of the electrode 13 so as to be electrically insulated from the electrode 13. The correction electrode 21 can locally apply a potential in the vicinity of the objective lens (main lens) 10.

[0030] Then, the objective lens (main lens) 10 and the correction electrode 21 are arranged in this order from the incident direction of the electron beam EB2. When the top surface force of this electron lens is also seen, as shown in FIG. 2B, a correction electrode 21 is installed at the center of the objective lens (main lens) 10, and a star-shaped hole 28 is formed at the center.

A voltage is applied to each electrode as in the first embodiment.

[0031] This modification is characterized in that the shape of the hole 28 formed in the correction electrode 21 is a star shape. When the shape of the hole 28 is a star shape, the equipotential surface 26 forming the electron lens is affected by the star shape and is different from the conventional equipotential surface 17. The electron beam EB2 that passes through the star-shaped tip of the hole 28 and the electron beam EB2 that passes through the central part differ in the strength of the electric field received by the electrons, and receive an aspheric lens action. The trajectory of the electron beam EB2 changes. Therefore, the aberration of the electron lens can be controlled by controlling the hole size of the correction electrode 21, the size of the correction electrode, the distance between the correction electrode and the objective lens, the potential of the correction electrode, and the like.

Since the energy of the electron beam also changes depending on the shape of the hole formed in the correction electrode, the characteristics of the electron lens can be corrected accordingly.

In this modification, a correction electrode in which a star-shaped hole is formed is shown as an example, but a correction electrode in which a V-shaped non-circular hole is formed can be used.

Next, FIG. 3A shows a cross-sectional view of an electron lens according to a second modification of the first embodiment of the present invention, and FIG. 3B shows a plan view. In the figure, elements common to the constituent elements shown in FIG.

A conventional electron microscope uses an electron beam having a circular cross-sectional shape. The child lens also had a circular shape. However, since the semiconductor device measuring apparatus (EBSCOPE) described above uses electron beams having various cross-sectional shapes, a circular electron lens is not always appropriate. This modification is characterized in that the shape of the objective lens is changed to a non-circular shape. The shape of the correction electrode is also changed to a star shape similar to the first modification described above.

As shown in the cross-sectional view of FIG. 3A, the present electron lens includes an objective lens (main lens) 30, a correction electrode 31, an electrode 32, an electrode 33, and a hole 38 from the first embodiment. It is an electrostatic lens with a modified structure. An objective lens (main lens) 30 consisting of a star-shaped cavity is formed on the electrode 32, and the center of the electrode 33 is provided with a star-shaped hole 38 that is smaller than the size of the objective lens (main lens) 30 The electrode 31 is provided so as to be electrically insulated from the electrode 33. The correction electrode 31 can locally apply a potential in the vicinity of the objective lens (main lens) 30.

[0034] Then, the objective lens (main lens) 30 and the correction electrode 31 are arranged in this order from the incident direction of the electron beam EB3. Looking at the surface force of this electron lens, as shown in Fig. 3B, a correction electrode 31 is installed at the center of the star-shaped objective lens (main lens) 30, and a star-shaped hole 38 is formed at the center. !

A voltage is applied to each electrode as in the first embodiment.

[0035] By using an objective lens having a star shape or other shapes in this way, it becomes possible to obtain an electron lens shape (shape of equipotential surface 36) different from a conventional circular objective lens. The aberration of the electron lens can be corrected. Only the objective lens may have a non-circular shape such as a star shape. By changing the angle at which the objective lens and the correction electrode are arranged in a plane, electron beams having various cross-sectional shapes can be obtained, and aberrations of the electron lens can be corrected.

Next, FIG. 4A shows a cross-sectional view of an electron lens according to a third modification of the first embodiment of the present invention, and FIG. 4B shows a plan view. In the figure, elements common to the constituent elements shown in FIG.

This modification uses isoelectric to determine the lens characteristics of an electrostatic lens by using mesh electrodes. The feature is that the shape of potential plane (potential surface) can be designed freely.

[0037] As shown in the sectional view of FIG. 4A, this electron lens is composed of an objective lens (main lens) 40, a mesh electrode 41, an electrode 42, and an electrode 43, and operates as an electrostatic lens. To do. An objective lens (main lens) 40 having a rectangular cavity force is formed on the electrode 42, and a mesh electrode 41 is electrically insulated from the electrode 42 inside the objective lens (main lens) 40. It is prepared. The electrode 43 is also provided with a rectangular cavity having the same size as the objective lens (main lens) 40.

The mesh electrode 41 is formed of a conductive metal or a material in which nickel, copper, silver, gold, or the like is attached or coated on a fiber, and an externally applied voltage is generated on the surface of the mesh electrode 41. It can be made. The mesh electrode 41 has a mesh structure and is an electrode that allows electrons to pass through the gaps between the electrodes.

[0038] The mesh electrode 41, the objective lens (main lens) 40, and the electrode 43 are arranged in this order from the incident direction of the electron beam EB4. When this electron lens is viewed from the top, as shown in FIG. 4B, a mesh electrode 41 is placed inside a rectangular objective lens (main lens) 40, and the mesh electrode 41 is connected to the pad electrode 47 by a lead wire 48. Electrically connected. By applying a voltage through the pad electrode 47 and changing the applied voltage, the surface potential of the mesh electrode 41 can be changed.

Further, the voltage 45c is applied to the mesh electrode 41, and the voltage 45b is applied to the electrode 42 and the voltage 45a is applied to the electrode 43. Each voltage may be an arbitrary voltage.

A conventional electrostatic lens is made of a circular planar electrode or cylinder having a space for allowing an electron beam to pass therethrough, and an electrostatic lens is formed by applying a voltage thereto. For this reason, the equipotential surface that the electrostatic lens can produce is a function only of the distance from the circular electrode, which causes aberrations in the electrostatic lens.

In this modification, the shape of the equipotential surface 46 that functions as an electrostatic lens can be freely controlled by changing the shape of the mesh electrode 41, so that an electronic lens having an arbitrary characteristic that does not cause various aberrations is manufactured. It is possible to do. The electron beam incident on the electron lens passes through the hole of the mesh and is converged while being influenced by the equipotential surface formed by the mesh electrode 41. In FIG. 4, a voltage is applied only to the force mesh electrode 41, which shows an example in which a voltage is also applied to the electrode 42 and the electrode 43, and it can be operated as an electrostatic lens with corrected aberration.

[0040] The shape of the mesh electrode 41 is optimally designed to have the required electrostatic lens characteristics using electron beam simulation or the like.

The kamaboko type electrostatic lens shown in this modification forms a curved lens surface in the uniaxial direction (long side direction of the electrode 42), and can be used when the electron beam shape is changed only in the uniaxial direction. . For example, this is effective when the cross-sectional shape of the incident electron beam is distorted into an ellipse and converted into a true circle.

[0041] <Fourth Modification of First Embodiment>

Next, FIG. 5A shows a cross-sectional view of an electron lens according to a fourth modification of the first embodiment of the present invention, and FIG. 5B shows a plan view. In the figure, the same reference numerals are given to the same elements as those shown in FIGS. 1 to 4 and the description thereof is omitted.

In this modification, the mesh electrode is curved with respect to two XY axes orthogonal to each other.

[0042] As shown in the sectional view of FIG. 5A, the present electron lens includes an objective lens (main lens) 50, a mesh electrode 51, an electrode 52, and an electrode from the third modification of the first embodiment. This is an electrostatic lens having a structure modified from 53. The electrode 52 is formed with an objective lens (main lens) 50 formed of a circular cavity. Inside the objective lens (main lens) 50, a mesh electrode 51 is electrically insulated from the electrode 52. Is provided. The electrode 53 is also provided with a circular cavity having the same size as the objective lens (main lens) 50.

The mesh electrode 51 is formed of the same material as that of the third modification of the first embodiment. The mesh electrode 51 has a mesh structure and is an electrode through which electrons can pass through the gaps between the electrodes.

When this electron lens is viewed from the top, as shown in FIG. 5B, a mesh electrode 51 is installed on the top of a circular objective lens (main lens) 50, and the mesh electrode 51 is filtered by a lead wire 58. The lead electrode 47 is electrically connected. The large and small circular electrodes constituting the mesh electrode 51 are supported by the lead wires 58 to form a three-dimensional shape.

By having such a structure, the shape of the equipotential surface 56 can be changed. [0044] As in the third modification described above, the mesh electrode 51 is obtained by performing a simulation or the like to obtain a shape that minimizes aberrations such as spherical aberration, and is manufactured according to the shape. In order to correct aberrations, depending on the design value of the mesh electrode, one mesh electrode may be sufficient for correction, or several mesh electrodes for correction with other shapes are stacked in the vertical direction. In some cases, it can be corrected. When superimposing mesh electrodes, it is necessary to obtain the optimum values by simulation and use them in combination with respect to the spacing between mesh electrodes, the size of the mesh electrodes, the curvature, the applied voltage, etc.

Next, FIG. 6A shows a sectional view of an electron lens according to a fifth modification of the first embodiment of the present invention, and FIG. 6B shows a plan view. In the figure, elements common to the components shown in FIGS. 1, 4, and 5 are given the same reference numerals, and descriptions thereof are omitted.

This embodiment is characterized in that an electron Fresnel lens is formed by bending a lens surface and planarizing the lens surface as is generally known for optical lenses. A Fresnel lens has a structure in which a normal lens is disassembled into minute parts, and only the curved surface part of the lens is taken out, and the position is shifted and flattened so that the lens height is almost constant.

As shown in the cross-sectional view of FIG. 6A, the present electronic lens is an electrostatic lens having a structure in which the mesh electrode 61 is changed from the fourth modification of the first embodiment. The objective lens (main lens) 50 is provided inside the mesh electrode 611S electrode 52 and is electrically insulated! / The mesh electrode 61 is formed of the same material as that of the third modification of the first embodiment. The mesh electrode 61 has a mesh structure, and is an electrode through which electrons can pass through the gaps between the electrodes.

When this electron lens is viewed from the top, as shown in FIG. 6B, a mesh electrode 61 is installed inside a circular objective lens (main lens) 50, and the mesh electrode 61 is filtered by a lead wire 68. The lead electrode 47 is electrically connected. The large and small electrodes constituting the mesh electrode 61 are supported by lead wires 68.

By having such a structure, the shape of the equipotential surface 66 can be changed. In this modification, the surface of the electron lens can be planarized in the same manner as the optical Fresnel lens, and spherical aberration can be reduced by adjusting the angle of each electrode. By further disassembling the original lens shape, it becomes possible to produce an electronic Fresnel lens closer to a flat surface. For example, with the recent electron beam exposure technology, it is possible to add an order of several nanometers, so that it is possible to manufacture an electron Fresnel lens that has such a lens step size and can be regarded as almost flat.

[0049] <Sixth Modification of First Embodiment>

Next, FIG. 7A is a cross-sectional view of an electron lens according to a sixth modification of the first embodiment of the present invention, and FIG. 7B is a plan view. In the figure, elements common to the components shown in FIGS. 1, 4, and 5 are given the same reference numerals, and descriptions thereof are omitted.

This modification is characterized in that an independent voltage is applied to each electrode forming the electron lens.

[0050] As shown in the sectional view of FIG. 7A, this electron lens is an electrostatic lens having a structure in which the electrodes 71a, 71b, 71c, and 7 Id are changed from the fourth modification of the first embodiment. is there. In the objective lens (main lens) 50, circular electrodes 71a, 71b, 71c, 71d 1S electrodes 52 of different sizes are formed so as to be electrically insulated.

The electrodes 71a, 71b, 71c, 71d are made of the same material as in the third modification, and a voltage applied from the outside can be generated on the surfaces of the electrodes 71a, 71b, 71c, 71d.

[0051] When the electron lens is viewed from above, circular electrodes 71a, 71b, 71c, 71d with different diameters are installed on the upper part of a circular objective lens (main lens) 50 as shown in FIG. 7B. The lead electrodes are electrically connected to the pad electrodes 77a, 77b, 77c, and 77d, respectively. By applying different voltages through the pad electrodes 77a, 77b, 77c and 77d and changing the applied voltage, the surface potentials of the electrodes 71a, 71b, 71c and 71d can be changed independently. The electrodes 71a, 71b, 71c, 71d are supported by an insulating support member 79 to form a three-dimensional shape.

The electrodes 71a, 71b, 71c, and 71d are respectively subjected to voltages 78a, 78b, 78c, and 78d with a force S. Each voltage may be an arbitrary voltage.

[0052] In this way, by applying an independent voltage to each electrode, the shape of the equipotential surface 76 is obtained. The desired equipotential surface shape can be obtained by freely changing the shape, and as a result, the aberration can be reduced. Furthermore, the equipotential surface shape can be changed instantaneously by changing the applied voltage. For example, when the acceleration voltage of the electron beam is changed, the aberration component changes. By changing the equipotential surface shape, aberration correction can be optimized dynamically.

In FIG. 7, various shapes such as a lattice shape and a dot shape can be used as the shape of the force electrode, which shows concentric electrodes as an example.

Next, FIG. 8A is a plan view that is displayed separately for each correction electrode in order to show the arrangement angle of each correction electrode of the electron lens according to the seventh modification of the first embodiment of the present invention. 8B is a plan view, and Fig. 8C is a cross-sectional view.

The feature of this modification is that the correction electrode has a multi-stage configuration, and the arrangement angle of each correction electrode is changed little by little at each stage so that the voltage applied to each correction electrode can be freely changed.

FIG. 8A is a plan view that is displayed separately for each correction electrode in order to show the arrangement angle of each correction electrode. As shown in the figure, the correction electrode 80b is offset by an angle of 8 lb, the correction electrode 80c is offset by an angle of 81c, and the correction electrode 80d is relative to the position of the correction electrode 80a consisting of a pair of opposing metal electrode forces. Is shifted by an angle of 8 Id, the correction electrode 80e is shifted by an angle of 81 e, and these five correction electrodes are sandwiched by insulators 82 as shown in the sectional view of FIG. . As a result, the shape shown in the plan view of FIG. 8B is obtained.

Voltages 83a, 83b, 83c, 83d, and 83e are applied to the correction electrodes 80a, 80b, 80c, 80d, and 80e, respectively, and these voltages can be changed arbitrarily.

Then, the voltage applied to the correction electrode at each stage is changed according to the magnitude of the asymmetric component of the electron lens, and control is performed so as to cancel the asymmetric component. As a result, it becomes possible to control the asymmetrical aberration of the original lens. For example, when the electron beam cross-sectional shape is an ellipse, the axis of the ellipse has various rotation axes, but if the correction electrode shown in this modification is used, correction is performed in the direction along the axis of the ellipse. The oval shape is true It can be converted to a circular shape.

In addition, the aberration can be corrected by applying another independent voltage to each set of the two correction electrodes shown in FIG. For example, if a voltage is applied to only one of the five correction electrodes (correction electrode 80b), only electrons near the correction electrode are affected, and the electron beam EB8 is slightly bent. As a result, the energy of a part of the electron beam component finally converged to one point can be changed and the electron beam trajectory can be changed, so that aberration can be corrected.

Next, FIG. 9A shows a cross-sectional view of an electron lens according to an eighth modification of the first embodiment of the present invention, and FIG. 9B shows a plan view.

This modification is characterized in that an asymmetric shape is preliminarily arranged on the multistage correction electrodes constituting the electron lens.

As shown in the cross-sectional view of FIG. 9A, this electron lens is provided with a correction electrode 91, a correction electrode 92, and a correction electrode 93 in this order also in the incident direction force of the electron beam EB9. Each is a multistage lens provided with an insulator 94. Each correction electrode can rotate independently and can be fixed at a desired position. Each correction electrode is provided with an objective lens 90 formed of a circular cavity at the center, and the electron beam EB9 is converged under the influence of an electric field when passing through the cavity. An independent voltage is applied to each correction electrode 91, 92, 93 (not shown).

Further, as shown in the plan view of FIG. 9B, the correction electrode 91 has an asymmetric shape 95 in the vicinity of the objective lens 90. The other correction electrodes 92 and 93 have a similar asymmetric shape (not shown). The asymmetric shape 95 has a structure in which a part of the correction electrode is concave. Alternatively, a part of the correction electrode may be convex.

The equipotential surface generated in the electron lens becomes an aspheric surface due to the asymmetric shape 95 in each correction electrode, and the shape of the equipotential surface can be changed by rotating each correction electrode.

A method of using this electronic lens will be described below. First, each of the correction electrodes 91, 92, and 93 is independently rotated little by little, and while measuring the aberration of the electron lens, the aberration is measured. Find the position of the correction electrode that minimizes. Since each correction electrode has an asymmetric component, the aberration of the electron lens can be set to the minimum depending on its rotation angle and combination. After the position where the aberration is minimum is determined, each correction electrode is fixed at a fixed position by using a not-shown cuff mechanism (position stop) attached to the electron lens.

[0060] By using the electron lens according to the first embodiment described so far to construct an electron lens of an electron microscope or a semiconductor measurement device (EBSCOPE), the characteristics of the electron lens can be changed instantaneously. It is possible to manufacture electron microscope equipment and semiconductor measuring equipment (E BSCOPE) with small aberration.

Here, an example of an electron beam scanning apparatus used in such an electron microscope apparatus will be described with reference to an example using the electron Fresnel lens shown in FIG.

First, Fig. 10 shows a cross-sectional view of an electron lens in which two electron Fresnel lenses are stacked.

The electron lens includes a first electron Fresnel lens 100, a second electron Fresnel lens 101, an electrode 102, an electrode 103, and an insulator 104.

Further, a voltage 105a is applied to the electrode 102 and a voltage 105b is applied to the electrode 103, and each voltage can be arbitrarily changed.

[0061] Electron beam source 106 force The emitted electron beam EB10 is first incident on the first electron Fresnel lens 100 and converged, and then incident on the second electron Fresnel lens 101 and converged to the required spot diameter. The

In this electron lens, the characteristics of the electron lens can be changed by changing the voltage applied to the electrodes 102 and 103. In addition, the angle of each electrode of the electron Fresnel lens can be freely changed as necessary. An electronic Fresnel lens can reduce spherical aberration, but a single electronic Fresnel lens may not be able to correct all aberrations. In such a case, aberration correction can be performed more accurately by using a plurality of electron Fresnel lenses like the present electron lens. For example, aberration correction along the X axis of the electron beam can be performed by the first electron Fresnel lens 100, and aberration correction along the Y axis of the electron beam can be performed by the second electron Fresnel lens 101. In particular, in the semiconductor device measurement apparatus (EBSCOPE) described above, the cross-sectional shape of the electron beam is not necessarily circular, so it is necessary to correct different aberrations for the X and Y axes. It is effective in such a case.

Next, FIG. 11 shows a cross-sectional view of an electron beam scanning device of an electron microscope using the electron lens shown in FIG. In the figure, elements common to the components shown in FIG. 10 described above are assigned the same reference numerals, and descriptions thereof are omitted.

This electron beam scanning apparatus also includes an electron beam source 116, an extraction electrode 117, an aperture 118, a deflection electrode 119a, a deflection electrode 119b, and the electron lens and force shown in FIG.

[0063] The operation of the present electron beam scanning apparatus will be described below.

The electron beam EB11 emitted from the electron beam source 116 is accelerated by the high voltage applied to the extraction electrode 117, the electron beam width is limited by the aperture 118, and the parallel beam is applied to the deflecting electrode. Led. The deflection electrode 119a deflects the electron beam E Bl1 so as to move back and forth, and the deflection electrode 119b deflects the electron beam so as to move left and right. The deflected electron beam EB11 is incident on an electron lens composed of the first Fresnel lens 100 and the second Fresnel lens 101. The incident electron beam EB11 is focused on the surface of a sample (not shown) or a necessary place by an electron lens.

[0064] The strength of the electron lens is determined by the voltage applied to the electrodes 102 and 103. Electron Fresnel lenses have very small spherical aberration, so the electron beam maintains a constant focal length even when the electron beam is scanned over a wide area and converged using all regions of the electron Fresnel lens. Then, it is converged to exactly one point and translated on the sample surface. Therefore, in the SEM using the conventional electromagnetic lens, if the position of the sample was fixed, high-resolution observation was possible only in the range of a few microns. It becomes possible to observe a wide range with high resolution.

Next, FIG. 12A shows a sectional view of an electron lens according to the second embodiment of the present invention, and FIG. 12B shows a plan view. In the figure, the same reference numerals are given to the same elements as those shown in FIGS. 1, 4, and 5, and the description thereof is omitted.

This embodiment includes a plurality of spatially arranged permanent magnets or rewritable magnets, Alternatively, the magnetic lens is formed of an electromagnet.

As shown in the cross-sectional view of FIG. 12A, this electron lens is a magnetic lens having a structure in which local magnets 121 are arranged instead of the mesh electrodes 51 of the fourth modification of the first embodiment. The magnet 121 can be made of a material that can be easily magnetized by an external magnetic field to become a permanent magnet, such as rare earth magnets such as ferrite and neodymium samarium, as well as cobalt and nickel. In addition, by using micromachining technology, several very small electromagnets with a size of several microns or less may be created instead of permanent magnets.

When this electron lens is viewed from the top, as shown in FIG. 12B, a concentric local magnet 121 is installed inside a circular objective lens (main lens) 50, and each local magnet is supported by a support line 12. Supported by 9.

[0068] Various aberrations occur in an electron lens (electromagnetic lens or magnetic lens) using a conventional coil or one magnet. In view of this, the present embodiment is characterized in that the magnetic lens is composed of a plurality of concentric magnets to correct aberrations that occur in the conventional magnetic lens. In the case of a conventional electromagnetic lens using only one coil, the interaction between the magnetic field generated from the coil and the electron beam is determined by the distance from the coil. For this reason, only an electron lens having a magnetic field strength distribution that is uniquely determined by the distance from the coil and the shape of the magnetic circuit can be formed, and this is the cause of various aberrations due to spherical aberration. .

[0069] In this embodiment, an electron lens having a magnetic field distribution 126 that is the sum of magnetic fields created by a plurality of magnets can be obtained. In this way, it is possible to create a magnetic field distribution with an arbitrary intensity and polarity in the space through which the electron beam passes, so by optimizing the magnetic field distribution by simulation etc., an electron lens with very small aberrations Can be configured.

In particular, electromagnetic lenses using conventional electromagnets could not make a diverging lens system even if a converging lens system could be made, but the electronic lens according to this embodiment can freely realize a converging lens and a diverging lens. it can. Therefore, the lens system can be designed more freely than in the past. Further, a voltage may be applied to the electrodes 52 and 53. In that case, the electron beam is affected by both the magnetic field and the electric field, and more advanced correction can be performed. <First Modification of Second Embodiment>

Next, FIG. 13A is a sectional view of an electron lens according to a first modification of the second embodiment of the present invention, and FIG. 13B is a plan view. In the figure, elements common to the constituent elements shown in FIGS. 1, 4, and 5 are given the same reference numerals, and descriptions thereof are omitted.

This modification is characterized in that the electron lens is configured by spatially arranging magnets concentrically.

As shown in the sectional view of FIG. 13A, the present electronic lens is a magnetic lens having a structure in which the local magnet 131 is changed from the second embodiment.

When the electronic lens is viewed from the top, as shown in FIG. 13B, a plurality of local magnets 131 are installed inside a circular objective lens (main lens) 50, and each is supported by a support line 139. ing.

[0072] The local magnet 131 may be a small fixed magnet, or may be manufactured using a magnetic film formed on a plastic film such as a magnetic tape. If such a material is used, a magnet can be formed at an arbitrary location.

The magnetic force, size, arrangement position, and polarity of the local magnet 131 are determined so as to realize an ideal magnetic field distribution using simulation or the like. In this modification, a magnetic field distribution having an arbitrary intensity and polarity can be realized, so that other aberrations than just spherical aberration can be corrected. Each local magnet 131 may have a different magnetic force depending on an arrangement position where the same magnetic force may be sufficient.

Further, a voltage may be applied to the electrodes 52 and 53. In that case, the electron beam is affected by both the magnetic field and the electric field, and more advanced correction can be performed.

Next, FIG. 14A is a sectional view of an electron lens according to a second modification of the second embodiment of the present invention, and FIG. 14B is a plan view.

In this modification, a magnetic lens in which magnets are spatially arranged is shown. By opening a plurality of holes 141 on the support substrate 140, and selecting several of the plurality of holes 141 and injecting a magnetic material, only the injected location becomes the magnet 142. When the electron beam that has also entered the upward force of the support substrate 140 passes through the hole 141, the electron beam from the magnet 142 that exists around the hole 141. The lens acts as a result of the generated magnetic field and converges or diverges. The aberration can be corrected by changing the arrangement position, strength, and polarity of the magnet 142. As the support substrate 140, various materials such as metal, ceramic, or organic material can be used. The shape of the hole 141 shown in FIG. 14 may be a circular force square, a polyhedron, or a mesh.

Next, FIG. 15 shows a plan view of an electron lens and a writing device according to a third modification of the second embodiment of the present invention.

This modification shows a magnetic lens in which micro magnets are locally arranged.

As shown in FIG. 15, this electron lens is composed of a circular magnet 151, and a cavity provided in the center serves as the objective lens 150. The circular magnet 151 includes a plurality of micro magnets 152 that are locally magnetized to n poles and a plurality of micro magnets 153 that are magnetized to s poles. By changing the arrangement position, polarity, and strength of each micro magnet 153, the magnetic field distribution in which these forces are also generated can be changed, and the aberration can be corrected to be small.

In addition, a writing control device 156 and a magnetic head 157 used for writing the magnet are provided, and writing is performed based on the digital signal 155. For example, when the signal 154 is used as an example of the digital signal 155, the n pole and the s pole are alternately written to the same magnitude with the same intensity, and the magnet 151 shown in the figure is obtained.

[0076] When the size is in millimeters, the micromagnet can be mechanically arranged using a robot such as a chip mounter. However, if the size is smaller than that, it is difficult to mechanically arrange the micromagnet. Therefore, in order to place a magnet with a size of a micron or smaller, prepare a material in which a magnetic material is formed in a thin film as described above, and use a magnetic head 157 for the material. Write the information.

The technology used for the magnetic disk can be applied to the magnetic head 157, and an electromagnetic magnetic head or a phase change magnetic writing method using a laser may be used.

For example, in writing using a magnetic head, a write current corresponding to magnet arrangement information that realizes a magnetic field distribution necessary to realize desired electron lens characteristics is magnetically generated. This is done by flowing through the head 157.

[0077] As a magnetic material that can be used for writing, a magnetic material generally used in a magnetic disk or a magnetic tape can be used, and a magnet having a size of a submicron unit is provided at an arbitrary interval. It becomes possible to arrange.

The direction of magnetizing can be selected from an in-plane direction or an arbitrary direction. As a method of changing the strength of the magnetic force, it can be performed discretely (digitally) by changing the ratio of magnets having a certain polarity or magnetic force arranged in a unit area. Alternatively, it is possible to use a method of changing the polarity and strength of each magnet continuously (analog) by changing the recording current applied to the magnetic head 157.

[0078] When sufficiently small magnets can be formed, the magnetic force of each magnet is made equal, and a magnetic lens that adjusts the strength of the magnetic field discretely (digitally) according to the number of magnets or the surface density Hope to do.

In FIG. 15, only an example of forming a magnet on a circular material such as a magnetic disk is shown, but a magnet may be written on a two-dimensional plane.

By using the electron lens according to the second embodiment described so far to construct an electron lens for an electron microscope or a semiconductor measurement device (EBSCOPE), an electron microscope device or a semiconductor measurement device (EBSCOPE ) Can be made.

[0079] <Third embodiment>

Next, FIG. 16A shows a cross-sectional view of an electron lens according to the third embodiment of the present invention, and FIG. 16B shows a plan view. In the figure, the same reference numerals are given to the same elements as those shown in FIGS. 1, 4, and 5, and the description thereof is omitted.

In the present embodiment, an example is shown in which an equipotential surface is arbitrarily designed by devising the shape of the mesh electrode to constitute an electron lens having two focal points. The conventional electron lens has only one focal point, but in this embodiment, two or more focal points can be freely obtained. For example, an electronic lens having a compound eye structure simulating the eyes of a dragonfly can be constructed. In addition, it is possible to provide a plurality of electron lenses having a focal point at the same position, and it is also possible to provide a plurality of electron lenses having a focal point at different positions.

As shown in the cross-sectional view of FIG. 16A, the present electron lens is a fourth modification of the first embodiment. The electrostatic lens has a structure in which the mesh electrode 161 is changed. A mesh electrode 161 is formed in the objective lens (main lens) 50 so as to be electrically insulated from the electrode 52. The mesh electrode 161 has two convex portions.

The mesh electrode 161 is formed of the same material as that of the third modification of the first embodiment, and a voltage to which an external force is applied can be generated on the surface of the mesh electrode 161.

When the electron lens is viewed from the top, as shown in FIG. 16B, a mesh electrode 161 is installed inside a circular objective lens (main lens) 50, and the mesh electrode 161 is padded by a lead wire 168. The electrode 47 is electrically connected. The large and small circular electrodes constituting the mesh electrode 161 are supported by the lead wires 168 to form a three-dimensional shape.

[0082] Usually, a measuring apparatus using an electron beam such as SEM has one electron beam source as shown in Fig. 8, and the generated electron beam is converged to a diameter of several nm. SEM images are obtained by irradiating the sample surface and scanning it two-dimensionally in the XY direction.

However, since the electron beam source has a lifetime, and it is often necessary to replace the electron beam source, the electron beam measuring device must be brought down during the replacement, and measurement cannot be performed.

Therefore, when an electron lens having a plurality of focal points is used in an electron microscope as in this embodiment, separate electron beam sources are installed at the plurality of focal points to obtain an electron beam that converges to one point. You can As shown in Fig. 16, the electron beams EB16a and EB16b have the same Cf standing at the position where the force incident on the electron lens from different positions converges. Furthermore, by changing the shape of the convex portion of the mesh electrode 161, it is possible to change the shape of the equipotential surface and correct the aberration.

[0084] In other words, a separate electron beam source is installed at the focal point position, operated one by one, and when the operating electron beam source is broken, it is switched to the next electron beam source and used in order. This makes it possible to always use the measuring device regardless of the lifetime of the electron beam source.

Also, if the above-mentioned plurality of electron beam sources are operated simultaneously, it is equivalent to obtaining a light source having higher brightness than before, so that a bright image or a large measurement signal can be obtained. . <First modification of third embodiment>

Next, FIG. 17A is a sectional view of an electron lens according to a first modification of the third embodiment of the present invention, and FIG. 17B is a plan view. In the figure, elements common to the constituent elements shown in FIGS. 1, 4, and 5 are given the same reference numerals, and descriptions thereof are omitted.

This modification is characterized in that an electron lens having a plurality of focal lengths is realized in one electron lens.

As shown in the cross-sectional view of FIG. 17A, this electron lens is an electrostatic lens having a structure in which the mesh electrode 171 is changed from the third embodiment. A mesh electrode 171 is formed in the objective lens (main lens) 50 so as to be electrically insulated from the electrode 52. The mesh electrode 171 has three convex portions.

The mesh electrode 171 is formed of the same material as that of the third modification of the first embodiment, and a voltage to which an external force is applied can be generated on the surface of the mesh electrode 171.

When this electron lens is viewed from above, as shown in FIG. 17B, a mesh electrode 171 is installed inside a circular objective lens (main lens) 50, and the mesh electrode 171 is padded by a lead wire 178. The electrode 47 is electrically connected. The large and small circular electrodes constituting the mesh electrode 171 are supported by the lead wires 178 to form a three-dimensional shape.

[0088] The operation of the present electron lens will be described below.

The electron beam EB 17a incident on the center of the electron lens has a focal length that converges on the sample surface, not shown. On the other hand, the electron beams EB17b and EB17c incident on the outer periphery of the electron lens have a longer focal length than the focal length of the electron beam EB17a. As a result, the electron beam is controlled so as to be focused and converged at the central portion of the sample, and is controlled so as not to be converged by shifting the focus at the peripheral portion. Furthermore, by changing the shape of the convex portion at the center of the mesh electrode 171, the shape of the equipotential surface can be changed, and the aberration of the electron beam converged on the center of the sample can be corrected.

In the above-described semiconductor device measurement apparatus (EBSCOPE), there are cases where it is desired to irradiate the electron beam having different densities to the peripheral portion of the measurement target and the measurement target. For example, when the electron beam is focused and irradiated onto the measurement target, a portion of the secondary electrons generated by the partial force of the target electron beam irradiation is recovered by the detector, but the secondary electrons that were not recovered are recovered. Are irregularly accumulated in the periphery of the object to be measured. Since the accumulated electrons have an irregular effect on the trajectory of the secondary electrons generated by the irradiation of the electron beam as needed, the amount of secondary electrons detected by the detector The measurement will become unstable.

[0090] In such a case, when the electron lens having two types of focal lengths of this modification is applied to the semiconductor device measurement device (EBSCOPE) and the electron beam is weakly irradiated to the periphery of the measurement target, A certain amount of electric charge is forcibly accumulated in. Due to the accumulated electric charge, the electrons existing in the vicinity are affected to a certain extent. Therefore, the secondary electrons generated at the measurement site are stably affected by a certain amount of charge in the vicinity, so the amount of secondary electrons detected by the detector stabilizes and the measurement is stabilized. You can do it.

[0091] <Second Modification of Third Embodiment>

Next, FIG. 18A is a cross-sectional view of an electron lens according to a second modification of the third embodiment of the present invention, and FIG. 18B is a plan view.

In this modification, in order to make it easier to apply a voltage to each electrode constituting the electron lens in addition to the upper part of the electron lens, a step is formed in the electrode and a pad electrode is provided above each electrode. There is a special feature.

As shown in the sectional view of FIG. 18A and the plan view of FIG. 18B, this electron lens has the same structure as that of the first modification of the third embodiment shown in FIG. The difference is that the size of the outer shape is smaller than the size of the outer shape of the electrode 183. A pad electrode 187a is provided above the electrode 182 and a pad electrode 187b is provided above the electrode 183 so as to be electrically connected to each electrode. A pad electrode 187c electrically connected to the mesh electrode 181 is provided on the electrode 182 so as to be electrically insulated from the electrode 182. With such a structure, the voltages 185a, 185b, and 185c are applied to each pad electrode from the upper part of the electron lens, respectively, and the degree of freedom in design increases when an electron microscope is manufactured using the electron lens.

It should be noted that the electrode arrangement shown in this modification can be adopted in all the above-described electron lenses.

[0093] The effects of the above-described embodiments are summarized below. In the present invention, an electron lens having characteristics required for an evaluation apparatus using an electron beam such as a semiconductor device measurement apparatus (EBSCOPE) can be obtained.

In other words, even if the characteristics of the electron lens are changed, it does not take time for the characteristics to stabilize, so a measurement method that frequently changes the acceleration voltage of the electron beam can be realized. In addition, it is possible to obtain an electron lens with extremely small spherical aberration without using a complicated correction device or correction method.

[0094] Conventionally, the electrostatic lens is small, but the aberration is large! /. Therefore, the electrostatic lens according to the present invention has a small aberration because the electrostatic lens of the present invention has a small aberration. It can be used as an objective lens for such applications. Therefore, it is possible to produce SEMs and process evaluation devices that are smaller and have higher resolution observation than before.

In addition, since the size of the electron lens can be reduced, the electron beam column can also be reduced in size, and it is a very strong electron beam column that is not affected by external noise (especially vibration, electromagnetic waves, geomagnetism). Can be obtained.

In addition, since the aberration characteristics of the electron lens can be changed freely, an electron lens with negative aberrations that not only yields an electron lens with no aberrations, or an electron lens that can change aberrations and lens characteristics with respect to the time axis. It is possible to get.

The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope that does not depart from the gist of the present invention.

In the present embodiment, it is needless to say that the method of the present invention can be applied to all electron lenses regardless of the power use described as an example of the objective lens that needs to consider the aberration most.

In addition, various electrode and magnet arrangement methods other than those described in the embodiment and changes in the polarity of the magnets also have the effect of controlling aberrations. It is also effective to use a combination of each electrostatic lens and magnetic lens described in the present embodiment. In manufacturing lenses, it is important to use the latest micromachining technology to further reduce aberrations.

Industrial applicability

The present invention is applied to an electron lens used in a microscope or an evaluation apparatus using an electron beam. It is preferable.

Claims

The scope of the claims

[I] An electronic lens equipped with a correction mechanism that corrects the aberration of an electrostatic lens.

[2] In the electron lens according to claim 1,

The electron lens, wherein the correction mechanism is a correction electrode disposed in the vicinity of the objective lens.

[3] The electron lens according to claim 2,

The correction lens has a circular hole, and is an electron lens.

[4] The electron lens according to claim 2,

The correction lens includes an electron lens having a shape other than a circular shape.

[5] The electron lens according to claim 2,

An electron lens characterized in that the shape of the hole of the correction electrode is different from the shape of the objective lens.

[6] The electron lens according to claim 1,

An electron lens characterized in that the correction mechanism is an electrode formed of a conductive material and capable of passing electrons.

[7] The electron lens according to claim 6,

2. The electron lens according to claim 1, wherein the electrode is formed by changing a shape of the conductive material.

[8] The electron lens according to claim 6,

The electrode is in the shape of a Fresnel lens.

[9] The electron lens according to claim 8,

An electron lens characterized in that a plurality of the electrodes in the shape of a Fresnel lens are arranged in the incident direction of the electron beam.

[10] An electron beam scanning device, wherein the electron beam scanning range is expanded using the electron lens according to any one of [8] and [9].

[II] In the electron lens according to claim 1,

The correction mechanism is a multistage laser in which a plurality of correction electrodes each including a pair of electrodes facing in a direction substantially perpendicular to the incident direction of the electron beam are arranged in the incident direction of the electron beam. And

An electron lens comprising voltage application means for applying independent voltages to the correction electrodes.

[12] The electron lens according to claim 11,

An electronic lens, wherein the arrangement angle of each of the correction electrodes constituting the multistage lens is different.

[13] The electron lens according to claim 1,

The correction mechanism is a multistage lens having a circular hole, and a plurality of correction electrodes each having a concave portion or a convex portion on the circumference of the hole, which are superimposed in the incident direction of the electron beam. An electron lens comprising voltage application means for applying independent voltages to each other, wherein each of the correction electrodes is rotatable.

[14] The electron lens according to claim 1,

An electronic lens characterized by having multiple focal points.

[15] The electron lens according to claim 14,

The electron lens characterized in that the plurality of focal points exist at different positions, respectively.

[16] The electron lens according to claim 14,

An electron lens characterized in that each of the plurality of focal points has a long focal length and a short focal length.

[17] An electronic lens equipped with a correction mechanism for correcting aberration of the magnetic lens.

[18] The electron lens according to claim 17,

The electronic lens according to claim 1, wherein the correction mechanism is a concentric arrangement of a plurality of ring-shaped fixed magnets having different sizes.

[19] The electron lens according to claim 17,

The electronic lens according to claim 1, wherein the correction mechanism includes a plurality of small magnets arranged in a plane.

[20] In the electron lens according to any one of claims 17 to 19,

In addition, an electrostatic lens is provided, and the magnetic lens and the electrostatic lens have an incident direction of an electron beam. An electronic lens characterized by being arranged to be the same.

[21] The electron lens according to claim 17,

The electron lens according to claim 1, wherein the correction mechanism includes a plurality of holes formed in a support substrate and magnets are provided in one or more of the holes.

[22] The electron lens according to claim 17,

The electronic lens according to claim 1, wherein the correction mechanism is composed of a magnet capable of rewriting polarity and / or strength.

[23] The electron lens according to claim 22,

An electronic lens characterized by rewriting the polarity and / or strength of the magnet using a magnetic head.

[24] The electron lens according to claim 23,

An electronic lens, wherein the magnetic lens is configured by discretely changing the strength of the magnet.

[25] The electron lens according to claim 23,

An electronic lens, wherein the magnetic lens is configured by continuously changing the strength of the magnet.

[26] An electron beam apparatus using the electron lens according to any one of [1] or [17].