JP4211473B2 - electronic microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron microscope capable of observing a sample while keeping the sample side under atmospheric pressure. More specifically, the present invention uses an electrode ring formed by forming various electrode films and resistance films on an insulating cylinder. The present invention relates to an electron microscope that increases the efficiency of pulling up secondary electrons emitted from deep and deep hole bottoms.
[0002]
[Prior art]
Today, semiconductor devices are highly integrated and miniaturized. As a result, it has become difficult to observe with the resolution of a conventional optical microscope as a means for analyzing the operation and failure of semiconductor devices. Therefore, an analysis method using a scanning electron microscope (SEM) instead of the optical method has been attracting attention as an effective means. For example, see Patent Document 1.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 6-78897
[0004]
The scanning electron microscope uses an extremely thin electron beam, so that even a highly uneven surface can be focused on almost the entire surface, and a microscopic world full of realism can be observed. The resolution of a scanning electron microscope is determined by the spot diameter of the electron beam, but not only the resolution but also the ability to observe hole bottoms with a large aspect ratio, such as contact holes, has been demanded as semiconductor devices become smaller. Yes.
[0005]
Conventionally, by the retarding method shown in FIG. 14, the acceleration voltage at the electron beam irradiation source is increased to reduce the aberration and improve the resolution, and a negative voltage is applied to the sample 20 to deepen the contact hole 21. A device for raising the emission trajectory a ′ of secondary electrons from the hole bottom or the like has been devised.
[0006]
[Problems to be solved by the invention]
However, if the semiconductor device is further miniaturized in the future and the contact hole has a high aspect ratio, it will be difficult to observe the bottom of the hole even with the retarding method. Since the energy of the secondary electrons is very small, in a contact hole with a large aspect ratio, most of the secondary electrons emitted from the bottom collide with the side wall portion before exiting from the contact hole and lose energy, and are not detected.
[0007]
Further, in order to prevent the electron beam from being scattered by collision with gas molecules, it is necessary to perform an inspection in a vacuum atmosphere, which increases the size of the apparatus, and TAT (turn In order to shorten the around time), it is common to provide a vacuum prechamber.
[0008]
For example, when inspecting a substrate of a 1 m × 1 m large flat panel display, an operating range of a stage that supports it and moves it in the XY direction requires a space of at least 2 m square. Maintaining a vacuum is not practical, and therefore, when inspecting a substrate of a flat panel display with a scanning electron microscope, the substrate is currently cut into a desired size and subjected to a destructive inspection.
[0009]
The present invention has been made in view of the above-mentioned problems. The object of the present invention is to enable observation of a sample with an electron beam without placing the sample side in a vacuum atmosphere, and to raise the efficiency of secondary electrons emitted from the sample. An object of the present invention is to provide an electron microscope having an improved height.
[0010]
[Means for Solving the Problems]
In solving the above-described problems, the electron microscope of the present invention is provided with a ring-like suction connected to an exhaust means around an electron beam emission hole of an irradiation head connected to a vacuum vessel containing an electron beam irradiation source. A groove is formed on the surface facing the sample, and an electrode ring is disposed in the electron beam passage path inside the irradiation head. The electrode ring includes an insulating cylinder having a hollow portion, and an insulating ring. A voltage application electrode film formed on one end face of the two end faces of the cylinder facing the sample with a minute gap therebetween and made equipotential with the sample, and formed on the other end face of the insulating cylinder And a grounding electrode film that is grounded, and a resistance film that is formed on the inner surface of the hollow portion and connects between the voltage application electrode film and the grounding electrode film.
[0011]
When the gap between the irradiation head and the sample is made very narrow and a gas is sucked from the suction groove, an electron beam (including secondary electrons) passes between the exit hole and the sample. The portion can be locally in a vacuum atmosphere. That is, with the irradiation head and the sample being in non-contact, the electron beam passage path can be hermetically blocked from the outside, and the electron beam collides with gas molecules and scatters. I can prevent it.
[0012]
Thus, it is not necessary to dispose the entire electron microscope including the sample and the supporting means for supporting the sample in a vacuum atmosphere, and it is not necessary to provide a preliminary vacuum chamber. As a result, the waiting time due to evacuation can be shortened, and further, non-destructive inspection can be performed even if the sample is a large substrate.
[0013]
Further, the electron beam is irradiated to the sample through the hollow portion of the insulating cylindrical body of the electrode ring. At this time, a gentle potential distribution is generated from the voltage application electrode film to the ground electrode film on the resistance film formed on the inner surface of the hollow portion. For this reason, the lens aberration of the electron beam irradiated on the sample through the hollow portion can be reduced.
[0014]
Further, the secondary electrons emitted from the sample pass through the hollow portion and reach the secondary electron detector. At this time, since the voltage application electrode film formed on the end face of the electrode ring facing the sample is equipotential with the sample, the sample is released from the sample between the sample and the end face of the electrode ring facing the sample. An electric field that prevents acceleration of the generated secondary electrons is not generated. As a result, the emission trajectory of secondary electrons can be raised, and secondary electrons from the deep hole bottom can be detected efficiently.
[0015]
Further, in the electrode ring, if a recess is formed on the end surface facing the sample, and the electrode film for voltage application is formed in the recess with a film thickness smaller than the depth of the recess, the sample and voltage application Contact with the electrode film can be avoided. As a result, it is possible to prevent the sample from being electrically destroyed by causing a current to flow through the sample due to a short circuit between the sample and the voltage application electrode film. This is particularly effective when the sample is a semiconductor wafer on which an integrated circuit is formed.
[0016]
Also, if the resistive film is formed on the inner surface of the hollow portion so as to be axially symmetric, even if a current flows through the resistive film and a magnetic field is generated, the magnetic fields due to the current flowing in the opposite locations cancel each other, and the inside of the hollow portion No magnetic field is formed. Thereby, the influence of the magnetic field on the electron beam and secondary electrons passing through the hollow portion can be avoided.
[0017]
For example, there is a form in which a hollow part is formed as a space where a cylinder is extracted, and a resistance film is intermittently formed axially symmetrically along the circumferential direction on the inner surface of the hollow part, or a form continuously formed along the circumferential direction. Can be mentioned. If formed continuously, an axially symmetric resistive film can be obtained easily without requiring highly accurate mask alignment.
[0018]
In addition, if there is not enough space on the end face side if the voltage application electrode lead part connected to the voltage application electrode film and the ground electrode lead part connected to the ground electrode film are formed on the side surface of the insulating cylinder Even when the gap between the end surface on which the voltage applying electrode film is formed and the sample is very narrow, for example, the electrode films can be easily connected to the outside.
[0019]
Further, in the electron microscope of the present invention, the irradiation head is connected to the vacuum container by a coupling means that can be expanded and contracted along the irradiation direction of the electron beam, and a compressed gas supply means is provided around the suction groove of the irradiation head. A ring-shaped gas ejection groove to be connected is formed so as to open on a surface facing the sample.
[0020]
The coupling means is, for example, formed in a bellows shape or a rubber shape and can be expanded and contracted, and the irradiation head follows the micro unevenness on the sample surface while the irradiation head floats on the sample by the compressed gas ejected from the gas ejection groove. Beam irradiation can be performed. Thereby, the sample can be inspected with high resolution.
[0021]
Moreover, if it is set as the structure which fitted the ventilation pad to opening of a gas ejection groove, it can eject stably, without compressed gas concentrating on one place and being ejected biased. Thereby, the space | interval of an irradiation head and a sample can be stably hold | maintained at a desired space | interval.
[0022]
In addition, if a step is formed on the outer peripheral side surface of the electrode ring and the step is brought into contact with the edge of the emission hole so that the electrode ring is fitted into the emission hole, the electrode ring can be utilized using the step. Can be accurately positioned.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exemplary embodiment of the present invention will be described with reference to the drawings.
[0024]
FIG. 1 is a schematic configuration diagram of an electron microscope 40 according to the present embodiment.
[0025]
The electron microscope 40 is roughly composed of a vacuum container 41 and an irradiation head 50 connected to the vacuum container 41 so as to be movable up and down. Opposite to the irradiation head 50, a support means 51 for the sample 20 is disposed, and this support means 51 is movable in the plane direction by an XY stage 52.
[0026]
The support means 51 is, for example, a vacuum chuck or an electrostatic chuck. When inspection of an area on the sample 20 (electron beam irradiation) is completed, the XY stage 52 is moved in the horizontal direction to inspect other areas.
[0027]
In the vacuum chamber 1, an electron gun 42 that is an electron beam irradiation source, a condenser electron lens 43 that converges the electron beam emitted from the electron gun 42, an electron beam modulator 44, and an electron beam aperture having an opening in the center. A plate 45, an electron beam deflecting means 46, a secondary electron detector 47, an electron beam scanning means 48, and the objective lens 23 are provided.
[0028]
The electron beam modulating means 44 is composed of, for example, opposing deflection electrode plates, deflects the electron beam by applying a required voltage between them, and modulates the electron beam transmitted through the opening of the electron beam diaphragm plate 45. Do.
[0029]
The electron beam deflecting means 46 guides secondary electrons emitted from the sample 20 to the secondary electron detector 47. The electron beam scanning means 48 performs raster scanning of the electron beam.
[0030]
In addition, although not shown, the vacuum vessel 41 is connected to an exhaust means, and the inside of the vacuum vessel 41 can be evacuated.
[0031]
Next, the irradiation head 50 will be described with reference to FIGS. FIG. 3 is a plan view of the lower surface side facing the sample 20 in the irradiation head 50.
[0032]
The irradiation head 50 is a cylindrical block body made of, for example, a ceramic material. A through hole 63 serving as an electron beam passage path is formed in the center of the irradiation head 50 along the axial direction. An exit hole 56 for electron beam is formed on the surface facing 20.
[0033]
Around the emission hole 56, a ring-shaped suction groove 57 is formed concentrically with the emission hole 56 so as to open on the surface facing the sample 20. Further, around the suction groove 57, a ring-shaped suction groove 58 is formed concentrically with the emission hole 56 so as to open on the surface facing the sample 20.
[0034]
In addition, a ring-shaped gas ejection groove 59 is formed around the suction groove 58 so as to be concentric with the emission hole 56 and open on the surface facing the sample 20. The gas ejection groove 59 is connected to the compressed gas supply means 55. A ring-shaped ventilation pad 60 made of, for example, a porous material is fitted into the opening of the gas ejection groove 59.
[0035]
The irradiation head 50 is connected to the vacuum container 41 by a coupling means 49. The coupling means 50 is a bellows-like member made of, for example, a rubber material, and is configured to be stretchable along an electron beam irradiation direction (a direction connecting the irradiation source 42 and the sample 20). When the coupling means 50 expands and contracts, the irradiation head 50 can change the distance from the sample 20 freely. The coupling means 50 is configured to surround the electron beam passage path from the vacuum vessel 41 to the through hole 63 of the irradiation head 50 in a ring shape, and airtightly blocks the electron beam passage path from the outside. Yes.
[0036]
The electron beam passage paths in the vacuum vessel 41 and the irradiation head 50 are evacuated by a high vacuum pump (not shown) such as a cryopump, a turbo molecular pump, or an ion sputtering pump.
[0037]
Vacuum pumps 53 and 54 are also connected to the above-described suction grooves 57 and 58 as exhaust means, and are evacuated. The suction groove 57 closer to the center side, that is, the electron beam emission hole 56 is evacuated to a higher degree of vacuum.
[0038]
Next, the electrode ring 1 fitted in the emission hole 56 will be described.
[0039]
FIG. 5 shows a plan view of one end face of the electrode ring 1 according to the present embodiment. FIG. 6 is a cross-sectional view taken along line [6]-[6] in FIG. FIG. 7 is a side view of the direction [7]-[7] in FIG. FIG. 8 shows a plan view of the other end face of the electrode ring 1. FIG. 9 is a side view of the direction [9]-[9] in FIG. FIG. 10 is a side view of the [10]-[10] line direction in FIG.
[0040]
The electrode ring 1 is formed by forming a voltage applying electrode film 3 on one end face of an insulating cylinder 2, a grounding electrode film 4 on the other end face, and a resistance film 11 on a hollow portion 6.
[0041]
The insulating cylinder 2 has a substantially cylindrical shape having a flange portion 5 on the end face side where the ground electrode film 4 is formed. Further, the side surface of the insulating cylinder 2 is partially cut away to form flat portions 12a and 12b. The flat electrode portions 12a and 12b are provided with a voltage application electrode lead portion 9 and a ground electrode lead portion 10 described later. They are formed adjacent to each other with the protruding portion 8 left so as to protrude radially outward by the notch.
[0042]
In the insulating cylinder 2, a recess 7 is formed on the end face side where the voltage application electrode film 3 is formed. The recess 7 extends radially outwardly toward a ring-shaped portion concentric with the hollow portion 6 and a flat portion 12a integrally connected to the ring-shaped portion and where the voltage application electrode lead-out portion 9 is formed. (See FIG. 5). The depth of the recess 7 is, for example, about 100 μm.
[0043]
The hollow portion 6 of the insulating cylinder 2 has a perfect circle diameter as an inner diameter, and the inner diameter is constant in the axial direction. Therefore, the inner surface of the hollow portion 6 is an axisymmetric curved surface.
[0044]
The insulating cylinder 2 is made of a ceramic material such as alumina, but is not limited thereto, and a nonmagnetic and insulating material can be used.
[0045]
A voltage application electrode film 3 is formed on the bottom surface of the recess 7. The voltage application electrode film 3 includes a ring-shaped portion concentric with the hollow portion 6 and a portion that is integrally connected to the ring-shaped portion and covers the extending portion of the recess 7. The voltage applying electrode film 3 is made of, for example, a titanium material, but other metal materials may be used. Use of the titanium material provides advantages such as corrosion resistance, high durability, good adhesion to the ceramic material constituting the insulating cylinder 2, and small variations in film thickness due to sputtering. In order to improve the adhesion, a TiN film may be interposed between the insulating cylinder 2.
[0046]
The end face on the side where the voltage applying electrode film 3 is formed is an end face facing the sample with a minute gap when the electrode ring 1 is incorporated into an electron microscope, as will be described later. The film thickness of the voltage application electrode film 3 is about 1 μm with respect to the depth of the recess 7 of about 100 μm, and the voltage application electrode film 3 is contained in the recess 7. Due to such a configuration, even if the end surface edge of the insulating cylinder 2 located on the outer peripheral side of the recess 7 is in contact with the sample, the voltage applying electrode film 3 in the recess 7 is in contact with the sample. Thus, it is possible to prevent the sample and the voltage applying electrode film 3 from being short-circuited to cause a current to flow through the sample and electrically destroy the sample.
[0047]
A ground electrode film 4 is formed on the other end face of the insulating cylinder 2 (see FIG. 8). The ground electrode film 4 extends radially outward toward a flat portion 12b concentrically connected to the hollow portion 6 and a flat portion 12b that is integrally connected to the ring portion and in which the ground electrode lead portion 10 is formed. It consists of parts to do. The ground electrode film 4 is made of, for example, a titanium material like the voltage application electrode film 3, but other metal materials may be used. The thickness of the ground electrode film 4 is about 1 μm.
[0048]
With respect to the axial direction of the insulating cylindrical body 2, the distance L (see FIG. 6) between the voltage application electrode film 3 and the ground electrode film 4 is 2 mm, for example.
[0049]
A resistance film 11 is formed on the entire inner surface of the hollow portion 6 of the insulating cylinder 2. The resistance film 11 is formed by connecting the voltage application electrode film 3 and the ground electrode film 4 formed on both end faces. The resistance film 11 is a high resistance film made of, for example, a DLC (Diamond Like Carbon) material having an electrical resistance value of about 30 MΩ to 100 MΩ, but is not limited to DLC, and silicon carbide (SiC) may be used. Also, the electrical resistance value can be easily set to a desired value by controlling the composition ratio of the constituent materials. The film thickness of the resistance film 11 is about 1 μm.
[0050]
A voltage application electrode lead portion 9 and a ground electrode lead portion 10 are formed on the flat portions 12a and 12b formed on the side surfaces of the insulating cylinder 2, respectively. The voltage application electrode lead-out portion 9 is formed of the same material and the same thickness as the voltage application electrode film 3 and is connected to a portion extending from the ring-shaped portion of the voltage application electrode film 3. The ground electrode lead portion 10 is formed of the same material and the same thickness as the ground electrode film 4 and is connected to a portion extending from the ring-shaped portion of the ground electrode film 4.
[0051]
As will be described later, the voltage application electrode lead-out portion 9 is connected to an external power source to apply a negative voltage, and the ground electrode lead-out portion 10 is grounded. Therefore, a negative voltage is applied to the voltage application electrode film 3 via the voltage application electrode lead-out portion 9, and the ground electrode film 4 is grounded via the ground electrode lead-out portion 10.
[0052]
The inner diameter of the hollow portion 6 of the insulating cylinder 2 is the same as the inner diameters of the ring-shaped portions of the voltage application electrode film 3 and the ground electrode film 4 and is L1. If the outer diameters of the ring-shaped portions of the voltage application electrode film 3 and the ground electrode film 4 are L2, L2 is at least twice L1 so that the hollow portion 6 is not affected by noise from the external environment. It is preferable to set it as these dimensions. For example, if L1 is 4 mm, L2 is 8 mm or more.
[0053]
That is, the voltage application electrode film 3 and the ground electrode film 4 function as a shielding material for preventing an undesired electric field or magnetic field from being formed in the hollow portion 6 that is a region through which an electron beam and secondary electrons pass. I will let you. The voltage applying electrode film 3 and the grounding electrode film 4 may not have a circular ring shape as long as L2 is twice or more of L1.
[0054]
Next, the manufacturing method of the electrode ring 1 comprised as mentioned above is demonstrated. First, an insulating cylinder 2 made of, for example, an alumina material is prepared. At this time, the concave portion 7 and the plane portions 12 a and 12 b for forming the voltage application electrode lead portion 9 and the ground electrode lead portion 10 are formed in the insulating cylinder 2 in advance.
[0055]
A resistance film 11 made of, for example, a DLC material is formed on the entire inner surface of the hollow portion 6 of the insulating cylinder 2 by a CVD (Chemical Vapor Deposition) method. Thereafter, a film made of, for example, a titanium material is formed by, for example, a sputtering method at predetermined positions of the concave portion 7 formed on one end face side, the other end face, and the flat portions 12a and 12b.
[0056]
The electrode ring 1 described above is disposed between the objective lens 23 and the sample 20 as shown in FIG. The gap between the objective lens 23 and the sample 20 is, for example, about 2 mm to 3 mm. In the gap, the ground electrode film 4 is formed with the end face on which the voltage application electrode film 3 is formed facing the sample 20. The end surface is opposed to the objective lens 23, and the hollow portion 6 is further disposed on the path of the electron beam irradiated onto the sample 20. At this time, the gap between the end face on which the voltage applying electrode film 3 is formed and the sample 20 is several tens μm to several hundreds μm. For this reason, it is difficult to draw out the electric wire connected to the voltage applying electrode film 3 from the gap between the sample 20 and the electrode ring end face.
[0057]
Therefore, the electric wire 30a is joined to the voltage application electrode lead-out portion 9 formed on the side surface of the insulating cylinder 2 with, for example, a vacuum conductive adhesive, and is drawn out to be connected to the power source 22. Similarly, for the ground electrode film 4, an electric wire 30 b is joined to the ground electrode lead-out portion 10 formed on the side surface of the insulating cylinder 2 with, for example, a vacuum conductive adhesive, and the electric wire 30 b is grounded. Further, a negative voltage is applied to the sample 20 from the power source 22, and the objective lens (electrostatic lens) 23 is grounded.
[0058]
A more detailed mounting structure of the electrode ring 1 will be described with reference to FIG. In the insulating cylindrical body 2 of the electrode ring 1, a flange portion 5 is formed on the end face side where the ground electrode film 4 is formed. Accordingly, the step portion 16 is formed from the flange portion 5 toward the end face side where the voltage application electrode film 3 is formed. The step 16 is brought into contact with the edge of the emission hole 56 so that the electrode ring 1 is positioned and prevented from dropping to the sample 20 side.
[0059]
In this state, the electrode ring 1 is fixed by the holding ring 64 placed on the end surface on which the ground electrode film 4 is formed and the screw 65 screwed into the outer peripheral side of the emission hole 56. Specifically, the lower surface of the head 65 a of the screw 65 is brought into contact with the upper surface of the pressing ring 64, and the screw 65 is screwed to press the electrode ring 1. The holding ring 64 has a ring shape having a through hole having an inner diameter larger than the outer diameter of the ground electrode film 4. If the screw 65 is unfastened, it can be easily replaced with another electrode ring.
[0060]
The above-described extraction of the electric wires 30a and 30b from the electrode ring 1 is performed through a through hole formed in the block 61 inserted into the irradiation head 50 as shown in FIG.
[0061]
In the through hole of the block 61, the electric wires 30a and 30b are insulated and separated from each other and fixed with an insulating adhesive for high vacuum. This adhesive seals the through hole, so that the electron beam passage and the outside are hermetically cut off to prevent vacuum leakage. The electric wires 30a and 30b may be drawn out through separate through holes to prevent mutual short circuit.
[0062]
Further, an O-ring 62 is disposed near the insertion opening of the block 61 to prevent vacuum leakage from the electron beam passage path.
[0063]
Further, in order to deal with the replacement of the electrode ring 1, the electric wires 30a, 30b and the electrode ring 1 can be connected by melting the solder by, for example, joining the locations in the electron beam passage path with the solder in the electric wires 30a, 30b. It can be separated. Or you may make the middle part of the electric wires 30a and 30b detachable by connector connection.
[0064]
Next, the operation of the electrode ring 1 and the electron microscope 40 including the electrode ring 1 will be described.
[0065]
First, compressed gas is supplied from the compressed gas supply means 55 to the gas ejection groove 59. This gas is, for example, nitrogen, helium, neon, argon or the like. As will be described later, this gas does not enter the electron beam passage path, but even if it temporarily enters, it is an inert gas so as not to deteriorate the electron emission cathode material of the electron gun 42 that is the electron beam irradiation source. Is preferably used.
[0066]
The compressed gas is ejected from the ventilation pad 59. In this state, the irradiation operation is performed from the suction grooves 57 and 58, and the irradiation head is differentiated between the positive gas pressure ejected from the ventilation pad 59 and the negative gas pressure sucked from the suction grooves 57 and 58. The irradiation head 50 is levitated from the sample 20 so that a desired gap (for example, several tens μm to several hundred μm) exists between the sample 50 and the sample 20.
[0067]
That is, most of the gas ejected from the ventilation pad 59 is first sucked by the suction groove 58 and further sucked by the suction groove 57. At this time, since the gap between the irradiation head 50 and the sample 20 is very small, the ventilation conductance of the gap is made extremely small, and almost no gas leakage into the electron beam emission hole 56 is avoided. In this way, the electron beam passage path in the irradiation head 50 can be maintained at a high vacuum while the sample 20 side is kept under atmospheric pressure, and further, the path from the exit hole 56 to the sample 20 can be maintained at a high vacuum. .
[0068]
Then, after the degree of vacuum in the irradiation head 50 rises to a predetermined value, a gate valve (not shown) provided in the vacuum vessel 41 is opened, and an electron beam from the irradiation source 42 is transferred from the emission hole 56 to the sample 20. Irradiate.
[0069]
In the present embodiment, for example, as shown in FIG. 11, a case where a contact hole 21 formed in a sample 20 such as a semiconductor wafer is observed is considered as an example. When an electron beam (indicated by a solid arrow in the figure) passes through the objective lens 23 and the hollow portion 6 of the electrode ring 1 and the exit hole 56 and is irradiated to the contact hole 21 of the sample 20, the irradiated portion Secondary electrons (indicated by a dashed line arrow in the figure) are emitted from the surface.
[0070]
Since a negative voltage is applied to the sample 20, secondary electrons are emitted from the sample 20 so as to repel. At this time, since the negative voltage is applied to the voltage application electrode film 3 formed on the end face side facing the sample 20 in the electrode ring 1 to make it equipotential with the sample 20, the sample 20 faces the sample 20. An electric field that prevents acceleration of the emitted secondary electrons is not generated between the electrode ring end faces.
[0071]
As a result, the secondary electron emission locus a (indicated by a two-dot chain line in FIG. 11) in the conventional configuration shown in FIG. 14 (configuration in which the electrode ring 1 is not interposed between the objective lens 23 and the sample 20). It can be raised compared to the discharge locus a ′. As a result, secondary electrons from the bottom of the contact hole 21 can be emitted without being absorbed by the side wall of the contact hole 21. This is particularly effective when the bottom of a contact hole having a high aspect ratio is observed as the semiconductor integrated circuit becomes finer.
[0072]
The emitted secondary electrons pass through the hollow portion 6 of the electrode ring 1 and the objective lens 23 and are attracted to the positive potential applied to the secondary electron detector 47 shown in FIG. It collides with the phosphor screen coated on the surface and is converted into light, and this light is amplified by a photomultiplier tube. This signal is further amplified and then displayed on the display device.
[0073]
When a negative voltage is applied to the voltage application electrode film 3 of the electrode ring 1, a potential distribution as shown in FIG. 12 occurs in the resistance film 11 from the voltage application electrode film 3 to the ground electrode film 4. . As shown in FIG. 12, the potential −Vp generated at a position close to the voltage application electrode film 3 is a peak, and the potential gradually decreases toward the ground electrode film 4 and approaches the potential 0. As described above, since the resistance film 11 has a large resistance value, the change in the overall potential distribution becomes gradual.
[0074]
FIG. 15 shows a configuration using a conventional typical cylindrical electrostatic lens. The electrostatic lens having such a configuration is generally called an Einzel lens, and includes three cylindrical electrodes 25, 26, and 27. The upper and lower electrodes 25 and 27 are grounded, and the central electrode 26 is connected to the power source 22 to apply a negative voltage. The electron beam is emitted from the electron gun or crossover position 24 with a certain opening angle, converged by the electric field in the electrodes 25, 26, and 27 and irradiated onto the sample 20.
[0075]
FIG. 13 shows the potential distribution in the axial direction when a voltage equivalent to that of the electrode ring 1 of the present embodiment is applied in a configuration using a plurality of cylindrical electrodes. That is, as shown in FIG. 16, a negative voltage is applied from the power source 22 to the electrode 29 arranged facing the sample 20 out of two independent cylindrical electrodes 28 and 29, and the other electrode 28 is grounded. In the case of the above configuration, as shown in FIG. 13, the potential distribution on the central axis changes greatly in the vicinity of the electrode 29 to which a negative voltage is applied.
[0076]
On the other hand, in this embodiment, as shown in FIG. 12, the change in the potential distribution in the axial direction of the inner surface of the hollow portion 6 in the electrode ring 1 can be moderated. Lens aberration can be reduced as the change in potential distribution is more gradual. This change in potential distribution can be optimized by adjusting the thickness of the resistance film 11 and the height of the electrode ring 1.
[0077]
As described above, according to the electrode ring 1 of the present embodiment, not only can the secondary electron emission trajectory from the deep bottom of the contact hole 21 be raised, but also the sample 20 is irradiated. The lens aberration of the electron beam can also be reduced.
[0078]
Note that a minute current flows from the voltage application electrode film 3 to the grounded electrode film 4 through the resistance film 11 on the inner surface of the hollow portion 6, but the inner surface of the hollow portion 6 is formed to be axisymmetric, Since the resistance film 11 is formed on the entire inner surface, the magnetic field generated by the current flowing in the axial direction of the resistance film 11 cancels the magnetic field generated by the current flowing in the opposite location, and no magnetic field is generated in the hollow portion 6. . Thereby, it is possible to avoid the influence of the magnetic field when the electron beam irradiated on the sample 20 and the secondary electrons emitted from the sample 20 pass through the hollow portion 6.
[0079]
In addition, since a current flows through the resistance film 11, the charging problem in the resistance film 11 can be avoided even when the electron film is irradiated with the electron beam.
[0080]
Further, the electrode ring 1 of the present embodiment is obtained by covering the insulating cylinder 2 with the voltage applying electrode film 3, the grounding electrode film 4, and the resistance film 11, and two independent rings shown in FIG. Compared to the case where the cylindrical electrodes 28 and 29 are used, the incorporation into the electron microscope can be easily performed.
[0081]
In other words, in the case of a plurality of cylindrical electrodes 28 and 29, it is necessary to incorporate not only the positional accuracy of each cylindrical electrode but also the positional accuracy between the cylindrical electrodes with high accuracy.
[0082]
In the present embodiment, the voltage application electrode film 3 and the ground electrode film 4 are formed in a ring shape on both end surfaces with reference to the hollow portion 6 of the insulating cylinder 2 having a constant diameter in the axial direction. The positional deviation between the electrode films 3 and 4 can be prevented. That is, when the electrode ring 1 is assembled, it is not necessary to align the electrode films 3 and 4.
[0083]
The embodiment of the present invention has been described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.
[0084]
Although the example which used the alumina material as the insulating cylinder 2 was shown, it is not restricted to this, You may use the other machinable ceramic material etc. with high processing precision and usable in a vacuum. Further, the insulating cylindrical body 2 is not limited to a cylindrical shape, and may be a rectangular cylindrical shape or a polygonal cylindrical shape.
[0085]
The number of suction grooves 57 and 58 is not limited to two, and may be one or three or more. Two or more gas ejection grooves 59 may be provided.
[0086]
【The invention's effect】
As described above, according to the present invention, the ring-shaped suction groove connected to the exhaust means is provided around the electron beam emission hole of the irradiation head connected to the vacuum vessel containing the electron beam irradiation source. Therefore, even if the entire electron microscope including the sample and supporting means for supporting the sample is not placed in a vacuum atmosphere, the electron beam is prevented from being scattered by gas molecules. The sample can be observed with high accuracy.
[0087]
Further, a voltage that is equipotential to the sample on one end surface of the insulating cylinder having a hollow portion through which the electron beam and the secondary electrons can pass, facing the sample with a minute gap. The application electrode film is formed, the ground electrode film to be grounded is formed on the other end face, and the resistance film for connecting the voltage application electrode film and the ground electrode film is formed on the inner surface of the hollow portion. The observation trajectory of deep hole bottoms and the like can be improved by raising the emission trajectory of secondary electrons emitted from the sample without impairing the lens aberration of the electron beam irradiated onto the sample.
[Brief description of the drawings]
FIG. 1 is a schematic view of an electron microscope according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of the irradiation head in FIG.
FIG. 3 is a bottom view of the irradiation head.
FIG. 4 is an enlarged cross-sectional view for explaining a structure for attaching an electrode ring to an emission hole in the irradiation head.
FIG. 5 is a plan view of an end face on the side facing a sample in the electrode ring according to the embodiment of the present invention.
6 is a cross-sectional view taken along line [6]-[6] in FIG.
7 is a side view taken along line [7]-[7] in FIG.
FIG. 8 is a plan view of the other end face of the electrode ring.
9 is a side view taken along line [9]-[9] in FIG.
10 is a side view in the [10]-[10] line direction in FIG. 8;
FIG. 11 is a schematic diagram showing an arrangement relationship of the electrode ring with respect to a sample and an electrical connection relationship of each electrode film.
FIG. 12 is a graph showing an axial potential distribution in the hollow portion of the electrode ring.
13 is a graph showing the potential distribution in the axial direction of the two ring electrodes shown in FIG.
FIG. 14 is a schematic diagram illustrating a conventional retarding method.
FIG. 15 is a schematic diagram showing the structure of a conventional Einzeln electrostatic lens.
FIG. 16 is a schematic diagram showing a conventional electrostatic lens structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrode ring, 2 ... Insulating cylinder, 3 ... Voltage application electrode film, 4 ... Ground electrode film, 6 ... Hollow part, 7 ... Recessed part, 9 ... Voltage application electrode extraction part, 10 ... Ground electrode extraction part 11 ... resistance film, 16 ... step, 20 ... sample, 21 ... contact hole, 22 ... power supply, 23 ... objective lens, 30a, 30b ... electric wire, 40 ... electron microscope, 41 ... vacuum vessel, 42 ... irradiation source, 47 ... secondary electron detector, 49 ... coupling means, 50 ... irradiation head, 53, 54 ... exhaust means, 55 ... compressed gas supply means, 56 ... exit hole, 57, 58 ... suction groove, 59 ... gas ejection groove, 60 ... vent pad, 63 ... electron beam passage path.

Claims (3)

A vacuum container containing an irradiation source for irradiating the sample with an electron beam;
An exit hole for emitting the electron beam to the sample on a surface facing the sample, a ring-shaped suction groove connected to exhaust means around the exit hole, and a compressed gas around the suction groove An irradiation head formed with a ring-like gas ejection groove connected to the supply means;
A coupling means for connecting the vacuum vessel and the irradiation head, and extending and contracting along the irradiation direction of the electron beam;
The first hole facing the sample, the second surface opposite to the first surface, the electron beam irradiated on the sample, and the emission hole through which secondary electrons emitted from the sample can pass A single-layer insulating cylinder having an inner peripheral surface forming a single hollow portion communicating with the first surface and having a recess formed in the first surface; and a film formed on the bottom surface and concentric with the hollow portion An electrode film for voltage application that is a ring-shaped and equipotential with the sample, a ground electrode film that is formed on the second surface and is concentric with the hollow portion and grounded, An electron microscope comprising an electrode ring formed on an inner peripheral surface and having a resistance film connecting between the voltage application electrode film and the ground electrode film, and disposed at a central portion of the emission hole . The electron microscope according to claim 1,
The irradiation head has an electron microscope having a ventilation pad fitted in the opening of the gas ejection hole The electron microscope according to claim 2,
The said electrode ring is an electron microscope which has a step part which is formed in the outer peripheral side surface, contact | abuts to the edge of the said output hole, and is fitted in the said output hole .

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