Scanning ion microscope and secondary particle control method

The present invention is provided to enable a detailed inspection of a specimen and preventing a distortion of an observation image even when a specimen containing an insulating material is partially charged. For a scanning ion microscope utilizing a gas field ionization ion source, a thin film is disposed between an ion optical system and a specimen, and an ion beam is applied to and transmitted through this thin film in order to focus a neutralized beam on the specimen. Furthermore, an electrode for regulating secondary electrons discharged from this thin film is provided in order to eliminate mixing of noises into an observation image.

FIELD OF THE INVENTION

The present invention relates to a scanning ion microscope that can form a specimen image by scanning with uncharged particles and a secondary particle control method.

BACKGROUND ART

Patent Document 1 and Patent Document 2 disclose focused ion beam (FIB) devices that have gas field ionization ion source (GFIS) and use gas ions such as hydrogen (H2), helium (He), and neon (Ne). Such gas focused ion beams (gas FIB) has an advantageous effect in that they do not bring Ga contamination to the specimen as in a gallium (Ga: metal) focused ion beam (Ga-FIB) from a liquid metal ion source (LMIS), which is used often nowadays.

In addition, the energy width of the gas ions extracted from GFIS is narrow and the size of an ion generation source is small in GFIS, and thus GFIS can form minute beams than Ga-FIB.

Such gas FIB devices are used as a scanning ion microscope having a high resolution. That is, an image of the specimen is formed by detecting secondary particles emitted from the specimen, synchronizing with the scanning the specimen with the ions.

Patent Document 3 discloses a pattern inspection device that use an ion beam, wherein the ion beam that has converged and scanned is neutralized and irradiates onto the specimen. The neutralization is performed by an electron emission source (grid etc. to which negative voltage is applied) which is provided to cross the ion beam.

Patent Document 4 discloses a surface analysis device that uses an ion beam, wherein the ion beam is charge-neutralized for irradiation of the specimen. The charge-neutralizing means is provided by exchanging charges in gas (and in a capillary). Here, in order to make energy of uncharged particle beams uniform and to remove particles other than uncharged particles, there are further provided a means for removing multivalent ions as pre-treatment and a means for removing charged particles as post-treatment.

Patent Document 5 discloses an analysis apparatus that uses ion beams of high energy (MeV level), wherein ion beams led from vacuum are applied to the specimen in atmospheric pressure such that the ion beams are transmitted through an exit window (pressure bulkhead). The pressure bulkhead is formed by attaching a gold thin film on a metal net-structured object. Here, since the net-structured object partially supports the pressure difference between inside and outside of the pressure bulkhead, the gold thin film through which the ion beams are transmitted can be made relatively thin. Thereby, analysis accuracy has improved. Patent Documents 6, 7 and 8 disclose techniques similar to those in Patent Document 5. Here, for example, methods for cooling the pressure bulkhead, methods for monitoring a beam amount, and methods for reinforcing the pressure bulkhead are disclosed.

Patent Document 9 describes an arrangement of a film that can transmit ion beams on an ion beam path in order to remove contamination of low energy that comes from, for example, inner walls, in an ion implantation device. The film is a high polymer thin film. Degradation is prevented by exchanging the film once in every fixed service period.

PRIOR TECHNICAL DOCUMENTS

Patent Document

Patent Document 1:

Japan Patent Application Publication JP 07-192669 APatent Document 2:

Japan International Patent Application Publication JP 2009-517846 WPatent Document 3:

Japan Patent Application Publication JP 62-298708 APatent Document 4:

Japan Patent Application Publication JP 2008-185336 APatent Document 5:

Japan Patent Application Publication JP 08-240542 APatent Document 6:

Japan Patent Application Publication JP 09-033462 APatent Document 7:

Japan Patent Application Publication JP 2010-203805 APatent Document 8:

Japan Patent Application Publication JP 2011-095154 APatent Document 9:

Japan Patent Application Publication JP 2002-134060 A

SUMMARY OF THE INVENTION

Object of the Invention

In a case where a specimen containing an insulator is observed with a scanning ion microscope, there is an issue that an image of the specimen is distorted with respect to an actual image as a result of the path of the ion beam being locally bent by partial electrification of the specimen. This cannot be completely solved by reducing electrification on the specimen. The best solution is to neutralize the ion beam itself (i.e., remove electric charge).

As described above, the ion beam neutralization method described in Patent Document 3 is described as having a grid structure in which negative voltage applied so as to intersect the flight path of the ion beam is applied.

Patent Document 4 needs to add, for example, a means for removing remaining ions to the latter stage. Such means serves as a big hindrance when converging ion beams minutely.

It should be noted that the conventional thin film utilizing methods described in Patent Documents 6, 7 and 8 do not describe whether the transmitted beam has electric charge. However, since energy of ions is large, existence of electric charge does not influence the measurement and thus it is presumed that the neutralization ratio itself is low. Furthermore, since the conventional thin film utilizing method described in Patent Document 9 does not care about convergence characteristics of the beam, existence of electric charge or secondary electrons in the transmitted beam has not been paid attention.

The present invention has been achieved in view of the above-described issues and an object of the present invention is to provide a scanning ion microscope that can observe a specimen minutely and prevent distortion of an observation image even if a specimen containing an insulator is charged partially and a secondary particle control method.

Means for Solving the Problem

In order to achieve the above-described object, the scanning ion microscope according to the present invention uses a gas field ionization ion source and arranges a thin film onto which ions are irradiated between a specimen and an ion optical system which makes ions converge and deflect onto the specimen. This thin film is supported by an electrically-conductive support member. There is provided a means for controlling an electric potential of the support member Furthermore, there are provided an electrode having an opening between the thin film and the specimen, and a means for controlling the electric potential of the electrode (e.g., power source83).

The present invention utilizes that most of the ions applied to the thin film are neutralized after going through a first layer on the surface of the thin film, and are emitted as uncharged particles when transmitting through the thin film. In addition, ions applied to the thin film also emit secondary electrons. There is provided a means for controlling the secondary electrons emitted from the thin film appropriately for preventing a part of the secondary electrons penetrating through the thin film (e.g., power source84).

EFFECT OF THE INVENTION

According to the present invention, it is possible to observe a specimen minutely and prevent distortion of an observation image even if a specimen containing insulators is charged partially.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of scanning ion microscopes according to the present invention will be described in detail with reference to the drawings.

FIG. 1shows an entire configuration of a scanning ion microscope according to the present embodiment. The scanning ion microscope200according to the present embodiment is configured by incorporating a gas field ionization ion source (GFIS)100utilizing helium (He) into a focused ion beam (FIB) device produced for a conventional gallium-liquid metal ion source (Ga-LMIS) instead of the Ga-LMIS.

InFIG. 1, a scanning ion microscope200has a configuration in which a helium (He) ion beam5emitted from a GFIS100enter into an ion optical system300(ion optical series system) which cause the ion beams5to converge by the ion optical system300, and thus irradiates a specimen6placed on a specimen stage101with the ion beams5. Acceleration voltage of ions is 30 kV.

The GFIS100includes: an emitter tip1; an extraction electrode2; and a gas discharge outlet3of gas supplying piping, which supplies gas for ionization to an apex of the emitter tip. The emitter tip1ionizes gas that is supplied from the gas discharge outlet3and resides at the apex of the tip with a high voltage (the emitter tip1side is positive and the extraction electrode2side is negative) applied from the extraction voltage application unit4between the emitter tip1and the extraction electrode2. The extraction electrode2extracts ions generated by the emitter tip1and emits the ions as an ion beam5to the ion optical system300.

The ion optical system300includes: a lens system102(lens series system) containing electrostatic lenses102a,102b, a beam limiting aperture102c, and an aligner102d; and a deflector system103(deflector series system) including deflectors103a,103b. The ion beam5that has entered the ion optical system300converges with the electrostatic lenses102a,102bin the ion optical system300and is applied to the specimen6. At this time, the position where the ion beam5is irradiated onto the specimen6is adjusted by deflecting the ion beam5with the deflectors103a,103b.

At this time, the lens system102including the electrostatic lenses102a,102b, the beam limiting aperture102c, and the aligner102dis controlled by a lens system controller105by controlling the drive of the corresponding drivers (DV)102aD-102dD. In addition, the lens system controller105also controls the ion beam5emitted by the ion optical system300by controlling the drive of the extraction voltage application unit4. Meanwhile, the deflector system103containing the deflectors103a,103bis controlled by control of the corresponding drivers (DV)103aD,103bD by the deflector system controller106.

An ion controller120for controlling the ion optical system300is configured with the lens system controller105and the deflector system controller106together with a plurality of drivers.

Secondary electrons7generated from the specimen6as a result of the above-described irradiation with the ion beam5are detected by a secondary particle detector104and are converted into digital signals through an A/D signal conversion unit104D. Thereafter, the image processing unit110forms a secondary electron observation image (image) in which the signal intensity of the digital signal is associated with the deflection intensity, and the image is displayed onto the display unit110b. An image formed by the image processing unit110is stored in a storage unit110a(image memory). The image thus stored is used for image operations and image display. The user can specify a position to which the ion beam5is applied on the screen of the display unit110bwhile looking into the secondary electron observation image displayed on the display unit110b.

InFIG. 1, an operation to control the entirety of the lens system controller105, the deflector system controller106, and the image processing unit110is omitted.

A first feature of the present embodiment is in addition to a fundamental configuration of the scanning ion microscopes a thin film80is disposed between the ion optical system300and the specimen6to neutralize the charge of the ion beam5to convert the ion beam5into an uncharged particle beam50for irradiating the specimen.

That is, the present embodiment maintains characteristics of a microscope since the thin film80serves as a neutralization means of the ion beam5and does not change at all the advancing direction of ions in the ion beam5that converge and scan in the ion optical system300. The secondary electron image of the specimen6is substantially unchanged from that in a case where there is no thin film80. However, since kinetic energy of the ion decreases slightly, brightness of the secondary electron image is reduced slightly. In addition, since a small amount of component that has changed in the advancing direction as a result of a scatter in the thin film80is mixed also, a small amount of background noise is produced in the secondary electron image.

It should be noted that since conventional neutralization means of an ion beam, for example, methods that use charge exchange in gas or capillary penetration, not only have low neutralization ratio but also the advancing direction of the ion beams spreads by experiencing a lot of dispersion, such means cannot be used for the purpose of the microscope according to the present invention.

Here, in order for the thin film80to function as a neutralization means of an ion beam, it is necessary to meet the following two conditions. A first condition is that an acceleration voltage of the ion beam5(which represents kinetic energy upon entering into the thin film80) should be in a low speed to medium speed region, which is from several kV to about 100 kV.

When an ion subject to the acceleration voltage in a range from a low speed to medium speed enters into a solid, the speed of the entering ion is overwhelmingly lower than a speed of an electrically-conductive electron in a solid. Accordingly, an electric field produced by the ion is immediately shielded by electrically-conductive electrons. That is, the ion is neutralized. This has been confirmed experimentally also by checking ions that are scattered on a surface of a solid. The ion scattered in a first atomic layer of a surface of a solid comes out mostly unchanged as an ion. The ion scattered in a second atomic layer of a surface of a solid comes out mostly being neutralized. It should be noted that it is possible to provide distinction as to from what depth and by what atom the reflected ions and uncharged particles are scattered according to energy losses by energy discrimination of the reflected ions and uncharged particles with, for example, a semiconductor detector. In addition, the measurement may be performed by removing only ions with an electric field.

FIG. 9shows a diagram illustrating a situation of neutralization of an ion beam in the present invention. The above situation of neutralization of the ion beam will be described now with reference toFIG. 9. In this diagram, “+” represents an ion, “N” represents an uncharged particle, and “−” represents an electron. A part of ions in the ion beam5that enters the thin film80are scattered at the surface. An ion scattered in the first atomic layer on the surface is emitted as an ion5b, and an ion scattered in the second atomic layer in the surface is emitted as an uncharged particle50b. If an ion is scattered in a location deeper than the second atomic layer, the ion hardly comes out from the thin film80but a part of the ions transmit through the thin film80as uncharged particles50c. Most ions in the ion beam5transmit through the thin film80as an uncharged particle beam50without changing the direction. Excited secondary electrons are emitted from the surface which the ion beam5enters and the surface the uncharged particle beam50is emitted. It should be noted that the scattered ions, uncharged particles, and secondary electrons are emitted with a broad angle distribution. In addition, re-ionization takes place rarely when the uncharged particle beam50is emitted. However, it is not illustrated since the probability is very low.

It should be noted that an ion beam having acceleration voltage of MV order, such as those used in RBS or PIXE, transmits through a thin film as ions with no change causing almost no interactions when entering into the thin film, and such an ion beam cannot be used for the present invention.

Another condition is that the thickness of the thin film80should be sufficiently thin as compared to a flying distance (“range”) of the ion beam5.

Near the “range”, the probability that an ion that has entered in to a solid scatters increases and the direction of the ions is broadened rapidly, and the ion stops near the “range”. At a distance sufficiently shorter than the range, the ion loses kinetic energy slightly as a result of inelastic scattering (dependent on the distance from the incident location) but the advancing direction is not changed. However, some ions change the advancing direction in a rare case as a result of elastic scattering. Such “range” varies with what the ion is (dependent on its mass), kinetic energy of the ion, and what the solid is (dependent on its element and density), and thus it is difficult to express the above condition with a short expression using an observable matter.

As to other expressions, it is considered that it is appropriate to express thickness of the thin film80with a transmission factor of the ion beam5. Fundamentally, the thickness of the thin film80is set such that 50% or more of ions in the ion beam5transmits through the thin film80. This condition is a practical limit. If this condition is not met, there are produced a lot of beams that have changed the direction as a result of the scattering in the thin film, thus causing a lot of background noise in the secondary electron image, for example. More preferably, it is possible to obtain an image of a specimen in which background noise is reduced by setting the thickness of the thin film80such that 90% or more of ions in the ion beam5transmit the thin film80. It should be noted that the neutralization ratio is reduced when the thickness of the thin film80is smaller than a two atom layer, and thus such a case is not suitable for the present invention.

Here, ionic species of the ion beam5is a monovalent helium ion in the present embodiment. Fundamentally, any ionic species can be used as long as the relation between the energy of the ion beam and the thickness of the thin film meets the above-described conditions (i.e., a multivalent ion or heavier ionic species is sufficient). Therefore, ion sources such as a plasma ion source, a liquid metal ion source, and an ionic liquid ion source can be used for the ion source instead of a gas field ionization ion source.

The reason why a helium ion is chosen in the present embodiment is that, since its normal state is gas, the ions come out from the thin film as gas when a small portion of the ions remain inside the thin film, and thus it is not likely to damage the thin film. If the ions are not gas, it is more likely that the ions remain and are accumulated in the thin film, changing the characteristics of the thin film. In this regard, neon ions and argon ions, which are gas, may also be used. In addition, another reason for selecting helium ions is because their transmission capability is high with respect to thin films that are currently available. In this regard, hydrogen ions having lighter mass may also be used. As to a heavy ion, it becomes more likely that thin films are damaged by sputtering.

The reason for selecting a gas field ionization ion source as an ion source in the present embodiment is that, since the ion source produces high brightness and the source size is small, it is easy to make an ion beam on the specimen minute and configure a microscope having a high resolution. In addition, since the electric current of the emitted ions is as small as several nA at most and ions turn into gas when neutralized, it is possible to make various kinds of damages done to the thin film80small.

A second feature of the present embodiment is in arranging an electrode82between the thin film80and the specimen. By handling the secondary electrons produced as a result of the thin film80appropriately, it is possible to avoid producing noise in the secondary electron observation image of the specimen. However, even if there is no such configuration and the secondary electrons are mixed in the image, substantially uniform background noise is reflected on the secondary electron image, and therefore observation of contrast that depends on the specimen can be performed sufficiently by applying suitable bias.

A third feature of the present embodiment is that front and back sides of the thin film80are kept in vacuum. Accordingly, it is possible to use thinner thin film for the thin film80since there is no need to support atmospheric pressure difference. Therefore, it is easier to increase the transmission factor of the ion beam5. However, even if gas at or below atmospheric pressure is arranged at the specimen side of the thin film80, there is no change in the essence of the present invention (the first feature described above).

Here, the thin film80is a silicon nitride thin film formed on a silicon substrate. The silicon substrate is etched in a shape of a window and a single silicon nitride thin film is placed in the window portion. The thin film is commercially available for holding specimens of transmission electron microscopes. Thickness of the silicon nitride thin film is 10 nm and the window size is 50 μm square. The thin film80is supported by a support body81having stainless characteristics and an electric potential thereof is controlled by the power source83. Usually, silicon nitride thin films are insulators and electrification may cause problems. However, large electrification is not produced on the silicon nitride thin films since electron hole pairs are produced inside as a result of irradiation of the ion beam5and thus the silicon nitride thin films are electrically conductive. Here, broadening the irradiation range of the ion beam5onto the outside of the window is effective for reducing the electric potential difference caused by resistance. Such broadening may be done upon performing blanking of the ion beam5.

An electric potential of the thin film80is made to be a ground potential, which is the same as the specimen6, by the power source83. If the thin film80is irradiated with the ion beam5by an acceleration voltage of 30 kV, the beam that has transmitted through the thin film80is neutralized to be an uncharged particle beam50. The uncharged particle beam50hardly is scattered in the thin film80, and thus applied to the same position on the specimen6to which the original ion beam5is converged and is deflected. Therefore, when an operation for acquiring a secondary electron observation image of the specimen6is caused to perform by the scanning ion microscope200, it is possible to acquire an image at the same location. As compared with a case where there is no thin film80, the amount of production of the secondary electrons7is reduced slightly, and in addition, the secondary electron observation image is not distorted when the specimen6is an insulator since the ion beam5is bent by the electrification of the specimen6.

Here, since the ion beam5does not converge on the thin film80, damage to the thin film80by the ion beam5is far smaller than damage to the specimen6. Furthermore, in the present embodiment, the thin film80can move slightly by the thin film slight movement mechanism800(thin film moving means) (refer toFIG. 1). Thereby, the degradation can be delayed using the entire region of the thin film80uniformly.

In addition, the thin film slight movement mechanism800can remove the thin film80from the ion optical axis of the ion optical system300. Thereby, larger secondary electron signals can be obtained when the specimen6is electrically-conductive.

FIG. 2shows a configuration near a thin film of the scanning ion microscope according to the first embodiment of the present invention. The periphery of the thin film80will be described in detail usingFIG. 2. When the thin film80is irradiated with the ion beam5, the secondary electrons70transmit through the specimen6side of the thin film80in addition to the uncharged particle beam50. When the secondary electrons70are mixed with the secondary electrons7produced at the specimen6and are detected by the secondary particle detector104(refer toFIG. 1), noise is mixed in the secondary electron observation image of the specimen6. Accordingly, in the present embodiment, the electric potential of the electrode82having an opening in the center is set by the power source84appropriately. That is, the secondary electron70is sent back to the thin film80side by setting the electric potential of the electrode82to minus several tens of V with respect to the electric potential of the support body81(ground potential in this case). Thereby, noise in the secondary electron observation image of the specimen6can be removed. It should be noted that no matter how the electric potential of the electrode82is set, the path of the uncharged particle beam50is not affected.

Now, a method for improving convergence performance of the uncharged particle beam50by setting the electric potential of the thin film80will be described. In the above descriptions, the acceleration voltage of the ion beam5is 30 kV and the electric potential of the thin film80(i.e., electric potential of the support body81) is a ground potential, which is the same as the specimen6. Convergence performance of the uncharged particle beam50in this case is fundamentally the same as convergence performance of the ion beam5.

Meanwhile, when the electric potential of the thin film80is set to a positive high potential, for example, 10 kV, by the power source83, and the acceleration voltage of the ion beam5is set to 40 kV, which is a value higher for an amount corresponding to the positive high potential, it is possible to improve the convergence performance of the uncharged particle beam50. By increasing the acceleration voltage of the ion beam5in this setting, the aberration of the ion optical system300becomes smaller, improving the convergence of the ion beam5. The ion beam5slows down immediately before the specimen6by being affected from the thin film80. This is because the lens effect in this part is small and thus the aberration thus produced is small also.

Meanwhile, the acceleration voltage (accelerating energy) of the uncharged particle beam50is incident energy of the ion beam5onto the thin film80([acceleration voltage of the ion beam5]−[electric potential of the thin film80]) and is 30 kV. This is the same as the above-described case. Accordingly, with such setting, it is possible to improve convergence performance of the uncharged particle beam50by making incident energy of the uncharged particle beam50onto the specimen6the same. That is, it is possible to reduce aperture as compared to the same beam electric current.

FIG. 3shows a configuration near a thin film of the scanning ion microscope according to a second embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that inFIG. 1but is different in that there are additional elements near the thin film80.FIG. 3shows a peripheral portion of the thin film80.

If the thin film80is irradiated with the ion beam5, a small amount of reflection particles and secondary electrons71are emitted to the side of the ion optical system300. When they enter an electrostatic lens or a deflector in the ion optical system300, the operation of the ion optical system300may become unstable as a result of inducement of unnecessary electrification onto the insulator portion. Accordingly, in the present embodiment, a shielding body85having an opening is arranged above the thin film80for blocking the reflection particles and secondary electrons71. Although a part of the particles enter into the ion optical system300, they do not directly enter insulators at least.

In addition, in the present embodiment, an electric current detector86is connected to the shielding body85and thus it is possible to monitor the electric current of the secondary electrons produced by the ion beam5. When the amount of electric current flowing into the shielding body decreases largely even though there is irradiation of the ion beam5, there is a possibility of abnormalities, such as when the thin film80is torn. In the scanning ion microscope in the present embodiment, the system is configured so as to at least alert the user by detecting abnormalities of the thin film80with the monitoring of the electric current. It should be noted that abnormalities, such as when the thin film80is torn, can be detected by monitoring the electric current flowing into the thin film80as well. Specifically, it is preferable if the power source83(means for controlling a first electric potential) detects abnormalities of the thin film80when the electric current flowing into the thin film80becomes a predetermined value or more by monitoring such electric current.

FIG. 4shows a configuration near a thin film of the scanning ion microscope according to a third embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that shown inFIG. 1but is different in that there are additional elements near the thin film80.FIG. 4shows a peripheral portion of the thin film80. It has a feature of having a several-molecules layer of ionic liquid80adispersed on the silicon nitride thin film80similar to the first embodiment. Here, C10H15F6N3O4S2 (C10H15F6N3O4S2) (CAS No. 174899-83-3) is used for the ionic liquid80a.

In the present embodiment, since the thin film80effectively becomes electrically-conductive as a result of the ionic liquid80a, restrictions in selecting the material for the thin film80itself are freed. That is, the thin film80may be a complete insulator. Since the acceleration voltage of the ion beam5is low, it is effective even when the electrical conductivity emerging effect as a result of the irradiation is small.

In addition, in the present embodiment, the ionic liquid80asolely is damaged by the ion beam5and is self-repaired as a result of the flow. Therefore, there is an advantageous effect of prolonging the lifetime of the thin film80. It should be noted that the ionic liquid80ashown here is good as long as it is electrically-conductive liquid and is not limited to the above-described composition.

FIG. 5shows a configuration near a thin film of the scanning ion microscope according to the fourth embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that shown inFIG. 1but is different in the configuration of the thin film80.FIG. 5shows a peripheral portion of the thin film80. In the present embodiment, the ionic liquid80ais impregnated into a net-structured object80b(mesh-structured object) made of carbon (thickness of several nm and average opening size of several μm), thus forming the thin film80. The ionic liquid80ais the same as that shown in the third embodiment.

From the ion beam5, the thin film80can be viewed as a thin layer of ionic liquid. This is because there are only few ions scattering at carbon. Therefore, the thin film80is electrically-conductive and has self-repairing characteristics as a result of the ionic liquid80a. The present embodiment also has an advantageous effect of prolonging the lifetime of the thin film80.

FIG. 6shows a configuration near a thin film of the scanning ion microscope according to the fifth embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that shown inFIG. 1but is different in the configuration of the thin film80.FIG. 6shows a peripheral portion of the thin film80. In the present embodiment, a crystalline body80cis used as the thin film80. Specifically, the thin film80is formed by partially reducing the thickness of a single crystal silicon substrate by etching. In addition, there is provided a thin film inclining mechanism801so as to enable change in the incident angle of the ion beam5onto the thin film80.

Here, there is a channeling phenomenon in the transmission of the ion beam through a crystalline body. That is, the channeling phenomenon is a phenomenon that the transmission capability of an ion beam entering in a specific crystal direction is high. The present embodiment adjusts such that the transmission capability of the ion beam5is the highest by inclining the crystalline body80cas appropriate by the thin film inclining mechanism801. Thereby, it is possible to prevent excessive scattered particles from existing above the thin film80. It should be noted that, when the thin film80is constituted by microcrystals, similar effect can be obtained with channeling if the directions of the microcrystals are aligned.

FIG. 7shows a configuration near a thin film of the scanning ion microscope according to the sixth embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that shown inFIG. 1but is different in portions near the thin film80. The portions near the thin film80are shown inFIG. 7. In the present embodiment, the electrode82is replaced with a mesh-structured electrode82a. Both the electrode82and the mesh-structured electrode82ahave a common feature of having an opening in the center portion of the transmission of the uncharged particle beam50. The electric potential of the thin film80is set to −100V with respect to the specimen6by the power source83. In addition, the electric potential of the mesh-structured electrode82ais set by the power source84to a ground potential, which is the same as the specimen6. By such electric potential setting, the secondary electron70produced at the thin film80is accelerated with 100 V to be irradiated to the specimen6. By irradiating the secondary electrons70onto the specimen6, it is possible to neutralize electrification on the surface if the specimen6is an insulator.

It should be noted that energy and the direction are completely different between such secondary electrons70and the secondary electrons7produced at the specimen6in an equipotential space surrounded by the specimen6and the mesh-structured electrode82a. For this reason, it is easy to detect only the secondary electron7selectively with an electric field produced at an end of the secondary particle detector104, and thus it is possible to achieve both the electrification neutralization and the specimen image formation. Of course, it is also possible to perform intermittently irradiation of the secondary electron70onto the specimen6by controlling the mesh electrode82a. Even if the electric potential of the mesh-structured electrode82ais controlled, there is no influence on the path of the uncharged particle beam50. In addition, even if the electrode82is not a mesh-structured electrode, it is possible to obtain the same effect as the above. However, in this case, the irradiation amount of the secondary electron70onto the specimen6is reduced slightly.

It should be noted that although the electric potential of the thin film80is negative in the present embodiment, it is good as long as the electric potential is relatively negative as compared to the electric potential of the specimen6. For example, it is possible to achieve a similar advantageous effect when the thin film80has a ground potential and the specimen has a positive electric potential. This case has an advantage that the accelerating energy of the ion beam5, that is, the accelerating energy of the uncharged particle beam50, can be made constant.

That is, it is preferable to accelerate secondary electrons emitted from the thin film80with several tens of V to several hundred V and inject them into the specimen6by maintaining a first electric potential, which is an electric potential of the support body81with respect to the electric potential of the specimen6, to negative relatively, and maintaining a second electric potential, which is an electric potential of the electrode82with respect to the first electric potential, to positive relatively.

FIG. 8shows a configuration near a thin film of the scanning ion microscope according to the seventh embodiment of the present invention. The scanning ion microscope in the present embodiment is fundamentally the same as that shown inFIG. 1but is different in that there are additional elements near the thin film80. The portions near the thin film80are shown inFIG. 8. In the present embodiment, there is provided an X ray detector700for detecting X rays72that come from the specimen6. The X ray detector700can conduct energy analysis of the X ray and can form a specimen image instead of secondary electron signals from the specimen6by outputting a part of the energy distribution as X ray intensity signals.

The X rays72are emitted from the specimen6according to the following setting in the present embodiment. That is, an electric potential of the thin film80is set to −10 kV with respect to the specimen6by the power source83. The electric potential of the electrode82is set by the power source84between an electric potential of the thin film80and a ground potential which is the electric potential of the specimen6. According to such electric potential setting, the secondary electron70produced in the thin film80is accelerated with 10 kV to irradiate the specimen6. A characteristic X ray which depends on the material of the specimen6is emitted as a result of the secondary electron70that is accelerated with several kV or more irradiating the specimen6. Scanning by the secondary electrons70is performed interlockingly as scanning by the ion beam5is performed by the ion optical system300. Accordingly, the configuration and setting in the present embodiment are equivalent to configuring an X ray analysis microscope that uses electron beams as a probe. Thus, there are advantageous effects of not only the specimen6being minutely observable by the neutral beam but also the material analysis being able to perform easily.

It should be noted that although the electric potential of the thin film80is negative in the present embodiment, there is a need to only be relatively negative with respect to the electric potential of the specimen6. For example, it is possible to obtain similar effects when the thin film80has a ground potential and the specimen has a positive electric potential. In this case, there is an advantage that the accelerating energy of the ion beam5, that is, the accelerating energy of the uncharged particle beam50, can be made constant.

That is, at least one of the secondary particle detectors104is an X ray detector700for X rays emitted from the specimen6. It is preferable if the first electric potential, which is an electric potential of the support body81with respect to the electric potential of the specimen6, is maintained relatively negative, and the second electric potential, which is an electric potential of the electrode82with respect to the first electric potential, is maintained relatively positive, and thus the secondary electrons emitted from the thin film6are accelerated with several kV to several tens of kV to be injected into the specimen such that the X rays emitted from the specimen are detected.

Here, if no special consideration takes place, the spread of the secondary electrons70on the specimen6is broad, resulting in low resolution of the secondary electrons70. Accordingly, in the present embodiment, the diameter of the opening and the electric potential setting of the electrode82are devised to have electrostatic lens functionality for the secondary electrons70. Thereby, the probe system of the electron beam on the specimen6can be made small to some extent. Specifically, resolution of the uncharged particle beam50is about 1 nm and resolution of the electron beam is about 1 μm. It should be noted that although the scanning range of the electron beam on the specimen6corresponds to the scanning range of the uncharged particle beam50, the size is different. Accordingly, the scanning ion microscope in the present embodiment has functionality to perform magnification correction when comparing both specimen images.

Although the present embodiment uses electrostatic lens functionality for converging the electron beams, the convergence performance of the electron beam can also be improved more using magnetic field utilizing lens functionality. Neither of the cases affects the path of the uncharged particle beam50at all.

It should be noted that the thin film80of the present invention is not limited to the above-described material and is preferably made of thin material that shows electrical conductivity at least by ion irradiation and is easily transmitted by ion beams. For example, thin films of carbon and metal, and a monomolecular film of electrically-conductive polymer may be used.

As described above, according to the scanning ion microscope in the present embodiment, the specimen image is formed by scanning with uncharged particles, and therefore it is possible to observe a specimen containing an insulator without distortion. In addition, since irradiation of electrons emitted from the thin film can be controlled, it is possible to prevent noise contamination in the specimen image. Furthermore, it is possible to prevent electrification of the specimen and perform analysis by making X rays emit from the specimen.

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