KR100711198B1 - Scanning electron microscope - Google Patents

Abstract

It is an object of the present invention to provide a scanning electron microscope capable of obtaining a spatially high spatial resolution in a low-speed voltage region.

The acceleration cylinder 9 is arranged in the electron beam passage of the objective lens 8 and the rear end acceleration voltage 10 of the first electron beam ratio is applied. A superimposed voltage 13 is applied to the sample 12 to form a decelerating electric field for the primary electron beam between the acceleration cylinder 9 and the sample 12. [ The secondary signal 23 such as a secondary electron or a reflection electron generated from the sample 12 is sucked into the acceleration cylinder 9 by an electric field immediately before the sample (decelerating electric field) and is placed above the acceleration cylinder 9 And detected by the secondary signal detectors 24-27.

Description

Scanning electron microscope

The present invention relates to a scanning electron microscope which obtains a two-dimensional scanning image representing the shape or composition of a surface of a specimen by scanning an electron beam on the surface of the specimen to be inspected. More particularly, the present invention relates to a scanning electron microscope, And to a scanning electron microscope suitable for obtaining.

A scanning electron microscope accelerates electrons emitted from a heating or field emission type electron source to form a fine electron beam (primary electron beam) by an electrostatic or magnetic field lens, and this primary electron ratio is detected by a scanning deflector And the secondary signal such as secondary electrons or reflection electrons secondaryly generated from the sample by the primary electron beam irradiation is detected and the detected signal intensity is synchronized with the primary electron beam scanning And inputting the luminance modulation to the cathode ray tube being scanned, thereby obtaining a two-dimensional dominant image. In a typical scanning electron microscope, electrons emitted from the electron source are accelerated between the electron source applying the negative potential and the anode at the ground potential, and the electron beam is injected into the inspection sample at the ground potential.

As a result of the use of a scanning electron microscope in the process of fabricating a semiconductor device or the inspection after completion (for example, measurement of dimension by an electron beam or inspection of an electric operation), a low- A high resolution of 10 nm or less is required from a voltage.

A factor that hinders the high resolution in the low-speed voltage region is the blur of the electron beam due to the chromatic aberration caused by the energy dispersion of the electron beam emitted from the electron source. In a scanning electron microscope having a low-speed voltage, a field emission-type electron source having a small energy scattering of an emitted electron beam is mainly used in order to reduce fog caused by the chromatic aberration. However, even in the case of a field emission type electron source, the spatial resolution at 500 volts is limited to 10 to 15 nm, which can not satisfy the requirement of the user.

As a solution to this problem, acceleration of the first electron charge ratio between the electron source and the anode at the ground potential is set to a voltage value higher than the final acceleration voltage, and between the objective lens at the ground potential and the inspection sample (See IEEE 9th Annual Symposium on Electron, pp. 176 to 186 page Ion and Laser Technology) by decelerating the primary electrons.

Although the effect of this method has already been confirmed by experiments, it is difficult to detect secondary electrons in the body by the decelerating electric field due to the application of a high voltage to the sample, and a sample stage with high insulating properties is required Therefore, there are few examples employed in a commercial apparatus.

The present invention is intended to solve the above-described problems. In the present invention, by providing a means for detecting a secondary signal such as a secondary electron or a reflected electron which has been attracted into the opening of the objective lens by the electric field applied between the objective lens and the sample after passing through the objective lens, The problem of differential signal detection is solved and a negative acceleration applied to the sample is lowered to a practicable value by providing a post acceleration means in the objective lens passage so that the structure can be employed in a commercial apparatus will be.

The present invention relates to an electron source, an electron source, a scanning deflector for scanning a sample on a first electron to electron ratio generated by the electron source, an objective lens for converging a first electron content, a secondary signal generated from the sample And a secondary signal detector for obtaining a two-dimensional scanning image of the specimen. In the scanning electron microscope, an acceleration cylinder arranged in the electron beam passage of the objective lens and a rear stage acceleration voltage in the acceleration cylinder are applied to the acceleration cylinder And means for forming a decelerating electric field for the primary electron beam between the acceleration cylinder and the sample, wherein the secondary signal detector is arranged at a position closer to the electron source than the acceleration cylinder.

According to the present invention, it is possible to solve the problem of difficulty in detecting secondary electrons or reflected electrons, the problem of handling caused by the application of a high voltage to the sample, and the reduction in chromatic aberration in the low- The microscope can be realized. The secondary signal detector may include a conductive reflective plate having an opening for passing the primary electron beam, a suction means for drawing the secondary electrons generated by the reflection plate, and a detection means for detecting the secondary electron have. The attracting means may be made of an electric field and a magnetic field orthogonal to the electric field, and the deflection of the first-order electric potential by the electric field may be canceled by the magnetic field. The secondary signal detection method of this method can be applied to the case where the acceleration cylinder is not provided or when the acceleration cylinder is set to 0 V (ground potential).

The secondary signal detector may be constituted by a multi-channel plate having an opening for passing a primary electromotive force, or may be constituted by a phosphor having an opening for passing the primary electromotive force and a photodetector for detecting the light emission of the phosphor .

The installation position of the secondary signal detector can be either between the acceleration cylinder and the scanning deflector, or between the scanning deflector and the electron source, or both. When a secondary signal detector is provided at two locations, either one of the detection signals may be used to form a dominant image, or a detection image of two detectors may be calculated to form a dominant image. The method of forming the main image by any method may be automatically selected in accordance with the magnification of the main image or the observation condition already given. The method using these two secondary signal detectors can also be applied to the case where the acceleration cylinder is not provided or when the acceleration cylinder is set to 0 V (ground potential).

The primary deflection beam scanning deflector can combine the electrostatic deflection and the magnetic field deflection to give the desired deflection to the primary electron beam, but not to the secondary signal attracted from the sample side. The deflection method for combining the electrostatic deflection and the magnetic field deflection can be applied to the case where the acceleration cylinder is not provided.

When the ratio of the rear end acceleration voltage applied to the acceleration cylinder to the electron gun voltage applied to the electron source and the ratio of the voltage applied to the sample to the electron gun voltage applied to the electron source are kept constant and the rear end acceleration voltage and the sample application voltage are controlled , The crossover point of the secondary signal generated from the sample can be maintained at a predetermined position.

By making the center of the lens made by the magnetic field of the objective lens coincide with the center of the lens of the electrostatic lens formed between the acceleration cylinder and the sample, the distortion of the scanning image due to the electrostatic lens action formed by the decelerating electric field can be eliminated.

When the acceleration pole is electrically insulated from the remainder of the objective lens and the acceleration pulse is applied to the phase pole by applying a rear end acceleration voltage thereto, the center of the magnetic lens coincides with the center of the electrostatic lens .

Example

1 is a schematic view of an embodiment of a scanning electron microscope according to the present invention. When the lead voltage 3 is applied between the field emission cathode 1 and the extraction electrode 2, the emission electrons 4 are emitted. The emission electrons 4 accelerate again (sometimes decelerating) between the extraction electrode 2 and the anode 5 at the ground potential. The energy (acceleration voltage) of the electron beam passing through the anode 5 coincides with the electron gun acceleration voltage 6. In the present invention, this accelerated electron beam 7 is rearranged by the acceleration cylinder 9 provided through the objective lens 8 again. The energy of the electron beam when passing through the objective lens 8 is the sum of the electron gun acceleration voltage 6 and the rear end acceleration voltage 10 applied to the acceleration cylinder 9. [ The primary electron beam 11 accelerated in the latter stage is decelerated by the negative superimposed voltage 13 applied to the sample 12 to obtain a desired acceleration voltage. The actual acceleration voltage of this method is independent of the rear end acceleration voltage 10, and is the difference between the electron gun acceleration voltage 6 and the superimposition voltage 13.

The primary electron beam 7 having passed through the anode 5 is deflected by the condenser lens 14, the residual scanning deflector 15 and the lower scanning deflector 16, And receives the acceleration of the rear end acceleration voltage 10 again by the acceleration cylinder 9 provided in the passage. The primary electron beam 11 accelerated in the post-stage is narrowly condensed on the sample 12 by the objective lens 8. The primary electron beam 11 having passed through the objective lens 8 is decelerated by the decelerating electric field 17 created between the objective lens 8 and the sample 12 and reaches the sample 12. [

According to this configuration, the acceleration voltage of the primary electrons when passing through the objective lens 8 is higher than the final acceleration voltage. As a result, the chromatic aberration in the objective lens is reduced as compared with the case where the first electron beam ratio of the final acceleration voltage is passed through the objective lens 8, and a thinner electron beam (high resolution) is obtained. The opening angle of the objective lens 8 at any first-order charge ratio is determined by the diaphragm 18 placed below the condenser lens 14. The centering of the diaphragm 18 is performed by the adjustment knob 19. Although mechanical adjustment is performed in the drawing, a static electricity or magnetic field deflector may be provided before and after the diaphragm 18 to adjust the electron beam by deflecting it.

The electron beam that has been converged by the objective lens 8 is scanned on the sample 12 by the resident deflector 15 and the underscan deflector 16. At this time, The deflection direction and the intensity of the scanning deflector 16 are adjusted so that the scanned electron beam always passes through the center of the objective lens 8. [ The sample 12 is fixed on the sample holder 20 to which the superposition voltage 13 is applied. The sample holder 20 is put on the sample stage 22 via the insulating plate 21 so that the horizontal position can be adjusted.

The secondary electron 23 is generated by irradiating the sample 12 with the primary electron beam 11. Since the decelerating electric field 17 formed between the objective lens 8 and the sample 12 acts as an accelerating electric field for the secondary electrons 23 and is thus attracted into the passage of the objective lens 8, And is raised while being subjected to a lens action by a magnetic field. The secondary electrons 23 that have passed through the objective lens 8 are attracted by the transverse electric field of the attracting electrode 24 placed between the objective lens 8 and the lower scanning deflector 16, 24 and is accelerated by a scintillator 25 to which 10 kV (constant potential) is applied to shine the scintillator 25. The emitted light is guided by the light guide 26 to the photomultiplier tube 27 and converted into an electric signal. The output of the opto-electronic expansion tube 27 is further amplified and becomes an intensity modulation input of a cathode ray tube (not shown).

This configuration is characterized in that the acceleration voltage of the electron beam when passing through the condenser lens 14, the diaphragm 18 and the objective lens 8 is higher than the final energy. Particularly, the objective lens 8, which governs the chromatic aberration, When you pass it, you will have more backward acceleration. In a typical example, the electron gun acceleration voltage is 1000 volts, the rear end acceleration voltage is 1000 volts, the negative overlapping voltage to the sample 18 is 500 volts, and the substantial acceleration voltage is 500 volts. When passing through the objective lens 8, the chromatic aberration is reduced to about 50% since it is 2000 volts, and the beam diameter (resolution), which was 15 nm when the acceleration voltage is 500 volts, is improved to 7 nm.

In the above-described embodiment, the secondary electrons 23 are extracted out of the electron path by the suction electrode 24 and detected. In this method, since the energy of the secondary electrons 24 is increased when the superposition voltage 13 is high, it is necessary to increase the voltage applied to the suction electrode 24 in correspondence thereto. As a result, the primary electron beam (accelerated electron beam 7) is also deflected.

The embodiment using the reflector shown in Fig. 2 solves the above-described problems and enables high-efficiency detection. In this embodiment, a reflector 29 having a central hole 28 is provided in the electron beam passage. The reflector is coated with a material such as gold, silver, and platinum that is easy to generate secondary electrons by electron irradiation. The accelerated primary electron beam 7 passes through the central hole 28 of the reflection plate 29 and then enters the acceleration cylinder 9. [ The diameter of the central hole 28 is set such that the electron beam deflected by the scanning deflectors 15 and 16 does not collide with the reflecting plate 29. [ The secondary electrons 23 accelerated by the superimposed voltage 13 generated in the sample 12 pass through the acceleration cylinder 9 while being diverged by the lens action of the objective lens 8, . The reflected electrons generated in the sample 12 also collide with the back surface of the reflection plate 29 similarly to the secondary electron and the orbit.

The secondary electrons 30 produced on the back surface of the reflector 29 are attracted by the electric field of the attracting electrode 24 and are attracted to the scintillator 25, the light guide 26, the photoelectron amplifier tube 27 And then converted into electrical signals. The feature of this method is that even when the superposition voltage 13 applied to the sample is high and the acceleration of the secondary electrons 23 becomes high, the secondary electrons 30, which are produced by the reflection plate 29 which is not accelerated, Therefore, the voltage applied to the suction electrode 24 can be low. Therefore, the influence of the electric field generated by the suction electrode 24 on the primary electron beam 7 can be reduced. Although the scintillator 25 is used for detection of the secondary electrons inhaled here, an electron detection amplifier such as a channel plate or a multi-channel plate may be used.

3 shows an example in which the magnetic field B is applied perpendicularly to the electric field E for attracting the secondary electrons 30 produced by the reflection plate 29. In Fig. According to this structure, it is possible to correct any deflection of the first-order charge ratio by the above-described attractive electric field E (E). That is, the deflection of the primary electron beam 7 due to the attraction electric field E is corrected by the deflection by the magnetic field B. Here, reference numerals 31 'and 31' 'denote electric field deflection electrodes for generating a suction electric field, and reference numeral 31' 'denotes a mesh for allowing the secondary electrons 30 to be transmitted. 32 'and 32' 'are linearly polarized deflection coils (the coils 32' and 32 '' generating the magnetic field B are represented symbolically in the drawing). The magnetic field B generated by the orthogonal magnetic field deflection coils 32 'and 32' 'is orthogonal to the electric field E and the intensity of the magnetic field B is generated by the electric field E received by the accelerated electron beam 7 So as to cancel the deflection. In this embodiment, a pair of orthogonal magnetic field deflection coils 32 is used. If the orthogonal magnetic field deflection coils are two pairs arranged at an angle, the orthogonality with the electric field can be strictly adjusted by adjusting the currents flowing in the coils of each group . It goes without saying that the orthogonality between the electric field and the magnetic field can be strictly adjusted even if the direction of the electric field is adjusted by using two sets of electric field deflecting electrodes instead of two sets of orthogonal magnetic field deflection coils 32.

The secondary signal detection method using the reflection plate 29 shown in Figs. 2 and 3 works effectively even when the acceleration cylinder 9 is not provided or when the acceleration cylinder 9 is grounded.

Fig. 4 shows an embodiment in which the secondary signal detector is provided above the resilient deflector 15. Fig. In the figure, a secondary signal detector is provided between the resident deflector 15 and the iris 18. 2, the central hole 28 is provided in the reflection plate 29. However, since the primary electron beam is not yet scanned and deflected, the size of the central hole 28 limits the opening angle of the minimum primary electron ratio The diameter may be the same as that of the iris 18. In the embodiment shown in the drawing, a reflector 29 having a central hole 28 having a diameter of 0.1 mm is provided below the diaphragm 18. The diaphragm 18 and the reflecting plate 29 may be shared.

In the case where the reflection plate 29 is provided below the scanning deflector, the diameter of the center hole 28 is set so that the deflected electron beam does not collide. When the size of the center hole 28 is compared with a typical example, the size of the center hole 28 is required to be 3 to 4 mm when it is installed downward, but it may be 0.1 mm or less when it is installed upward. Thus, when the reflector is disposed above the scanning deflector, the center hole of the reflector can be made sufficiently small, so that the efficiency of capturing by the reflector of the secondary electron is improved.

In the embodiment of FIG. 4, the sample 12 is placed within the lens gap of the objective lens 8. This arrangement reduces the chromatic aberration coefficient of the objective lens 8, and is a shape seeking a higher resolution. The sample stage 22 is also installed in the objective lens 8.

5 shows an embodiment in which a secondary signal detector is provided at both positions above and below the scanning deflector. A phase detector 33 is provided on the resident yarn deflector 15 and a lower detector 34 is provided between the lower scanning deflector 16 and the acceleration cylinder 9. [ 3 and 4, the phase detector 33 and the bottom detector 34 are provided with reflection plates 29a and 29b, electric field deflection electrodes 31a and 31b, orthogonal magnetic field deflection coils 32a and 32b, Scintillators 25a and 25b, light guides 26a and 26b, and opto-electronic expansion tubes 27a and 27b.

In this embodiment, secondary electrons or reflected electrons that have escaped through the central hole 28b of the reflection plate 29b of the lower detector 34 can be detected by the phase detector 33. [ Since the secondary signal detected by the phase detector 33 contains a large amount of secondary electrons and reflected electrons emitted from the sample 12 in the vertical direction, the phase contrast is different from that of the bottom detector 34 Loses. For example, in the inspection of the contact hole in the manufacturing process of the semiconductor device, when the lower detector 34 is used, an image emphasizing a portion of the contact hole from the periphery is obtained. When the phase detector 33 is used, Phase. It is also possible to generate a contrast by emphasizing the characteristics of the sample by calculating the signals of the detectors 33 and 34.

Whether the upper and lower detector outputs are used to generate the sketch image can be selected by the operator, but it may be automatically selected according to the already determined conditions. For example, the lower detector 34 is selected when the observation magnification is 2000 times or less, and the phase detector 33 is selected at a higher magnification. It is also possible to select according to the sample to be observed. In this case, a procedure such as inputting the kind of the sample to be observed to the apparatus is performed. For example, when the observation of the contact hole of the semiconductor element is input, the phase detector 33 for emphasizing the inside of the hole is automatically selected, and when the resist on the surface is observed, the bottom detector 34 is selected.

In the embodiment shown in Fig. 4 or 5, even if the acceleration cylinder 9 is removed or the acceleration cylinder 9 is grounded, the effect is large and sufficiently practical.

6 is an embodiment for detecting a secondary signal using a multi-channel plate detector. The multi-channel plate detector main body 35 is formed in a circular plate shape, and has a central hole 28 passing through the primary electromagnetism ratio. A mesh 37 is provided below the multi-channel plate detector main body 35 and is grounded. In this configuration, the accelerated primary electron beam 7 passes through the central hole 28 of the microchannel plate, and is then converged by the objective lens and irradiated onto the sample. The secondary electrons 23 generated in the sample pass through the mesh 37 and enter the channel plate body 35. The secondary electrons 23 incident on the channel plate body 35 are accelerated and amplified by the amplification voltage 38 applied to both ends of the channel plate body 35. The amplified electrons 39 are accelerated again by the anode voltage 40 and are trapped in the anode 41. The captured secondary electron signal is amplified by an amplifier 42 and then converted into an optical signal 44 by a photoconversion circuit 43. The conversion into the optical signal 44 is because the amplifier 42 is floated by the amplification voltage 38 of the channel plate body 35. The optical signal 44 is again converted into an electric signal by the electric conversion circuit 45 of the ground potential and used as a luminance modulation signal of the scanning type.

Here, information on the emission direction of the secondary electrons 23 can be obtained by dividing the anode 41 into two or four divisions. Needless to say, in this case, it is needless to say that the number of amplifiers 42, the photoconversion circuit 43, and the electrical conversion circuit 45 is required for the number corresponding to the division, and that the signal processing for calculating the divided signals is performed.

7 is an embodiment for detecting a secondary signal using a single crystal scintillator. 7, the single crystal scintillator 46 is formed by cutting a circumferential YAG single crystal at an oblique angle and providing an opening 47 for passing a primary electromagnetism ratio through the cut surface. A metal or carbon The conductive thin film 48 is coated, and the conductive thin film 48 is grounded. The light emitted by the secondary electrons 23 emitted from the sample 12 to the scintillator 46 is reflected by the inclined portion and guided to the opto-electronic expansion pipe 27 by the light guide constituted by the circumferential portion, , And amplified. In the present embodiment, both the light emitting portion of the scintillator 46 and the light guide are made of YAG single crystal. However, it is also possible to use only the light emitting portion for detecting the secondary electrons as the YAG single crystal or the phosphor, Or the like may be used.

A control method for efficiently performing the secondary signal detection will be described with reference to FIG. Since the secondary signal (for example, the secondary electrons) 23 passes through the magnetic field of the objective lens 8, it is subjected to the lens action, and a crossover 49 of the secondary electron is produced. If the secondary electrons focus on the aperture 47 of the scintillator 46 due to the lens action, most of the secondary electrons pass through the aperture 47 and can not be detected. Therefore, the focus is adjusted so as to form before and after the reflection plate, thereby improving the detection efficiency. In the embodiment, the rear end acceleration voltage and the superimposed voltage to be applied to the sample are controlled so as not to change the focal position of the secondary electron when the acceleration voltage (substantial acceleration voltage) is changed.

The focal length of the magnetic field lens is a function of the variable (I N / V _1/2 ) where I is the current flowing through the lens coil, N is the number of turns of the coil, and V is the acceleration voltage of the electrons passing through the lens magnetic field . The acceleration voltage when the primary electrons pass through the lens magnetic field is (Vo + Vb) when Vo is the electron gun acceleration voltage and Vb is the post-injection acceleration voltage applied to the acceleration cylinder. Since the sample position (focal distance) is constant, I N / (Vo + Vb) _1/2 always becomes a constant (= a). The acceleration voltage when the secondary electrons pass through the lens magnetic field is expressed by the following equation (I · N / V _1/2 ) by (Vr + Vb) when the superimposed voltage applied to the sample is Vr do.

I · N / V _1/2 = a (Vo + Vb) _1/2 / (Vr + Vb) _1/2

= a {1+ (Vb + Vo)} _1/2 {Vr / Vo) + (Vb + Vo)} _1/2

From this equation, if the Vr / Vo and Vb / Vo ratios are controlled to be constant, the focal position of the secondary electrons becomes constant. That is, when the rear end acceleration voltage Vb and the superimposition voltage Vr of the sample are controlled by making the Vr / Vo and Vb / Vo ratios constant and do not depend on the acceleration voltage (substantial acceleration voltage) Can be constantly controlled.

8 shows an example in which a control electrode for controlling the electric field applied to the sample surface is added. A control electrode 36 is provided between the objective lens 8 and the sample 12 and a control voltage 50 is applied thereto. The control electrode 36 has a hole through which the electron beam passes. The control electrode 36 controls the electric field intensity applied to the surface of the sample 12 between the acceleration cylinder 9 and the sample 12. This configuration is effective when a strong electric field is applied to the sample, which is a problem. For example, there is a problem of device breakage due to a strong electric field of a wafer on which a semiconductor integrated circuit is formed.

And is effective for the problem of electrical non-contact with the sample holder 20 when the periphery of the wafer is covered with the oxide film. More specifically, it is impossible to make electrical connection for retarding and decelerating when the side surface and back surface of the sample (wafer) are covered with an insulator. The sample (wafer) 12 is in an electric field generated between the sample holder 20 and the objective lens 8, and when there is no control electrode, the superposition voltage 13 applied to the sample holder 20, This is because only the potential in the middle of the objective lens 8 in the potential is not applied and normal observation becomes impossible.

The potential of the control electrode 36 is raised to a potential higher than the potential of the sample holder 20 to which the superimposition voltage 13 is applied or to a potential which is several tens of volts larger than that of the sample holder 20, It is possible to prevent floating from the potential of the gate electrode 20. In this case, the control electrode 36 is always large enough to cover the sample (wafer).

9 is a diagram showing an example of a case where a control electrode is added.

A control electrode 60 having an opening 59 through which a primary electrification line passes is provided above a sample (wafer) 12, and a superimposed voltage 13 (13) applied to the sample holder 20 is applied to the control electrode 60 ) Is applied. When the control electrode 60 having the same potential as that of the sample holder 20 is provided on the sample (wafer) 12, the wafer is surrounded by the metal of the same potential, and the wafer becomes coincident with the potential of the surrounding metal . Strictly speaking, the intrusion of an electric field from the opening 59 passing through the primary electron beam 7 results in an error with the potential of the metal. This error is roughly a ratio of the area of the sample (wafer) 12 to the area of the opening 59. For example, if the wafer is 8 inches and the diameter of the opening 59 is 10 mm, the area ratio is 1/400, and the error of the potential becomes 1%, which is a sufficiently small value.

In the above configuration, the potential of the metal surrounding the wafer and the same potential can be applied to the wafer.

Thereby, even when the wafer is a wafer whose front and back surfaces are covered with an insulating film and can not be electrically connected to a sample stage or the like, a voltage for deceleration can be applied.

Fig. 10 shows another example of a case where a control electrode is added.

A control electrode 60 is provided between the sample (wafer) 12 and the objective lens 8 and a voltage equal to the superimposed voltage 13 applied to the sample holder 20 is applied to the control electrode 60 . As a result, the sample (wafer) 12 is surrounded by the sample holder 20 and the control electrode 60 to which the same voltage is applied, so that the sample (wafer) 12 is covered with the insulating film The voltage of the superimposed voltage 13 can be applied to the sample (wafer).

The opening 59 of the control electrode 60 is usually a circle or a circle. The size of the opening 59 is set so as not to interfere with the field of view to be observed. In this embodiment, the size of the opening 59 is 4 mm in diameter. Since the distance between the control electrode 60 and the sample (wafer) 12 is 1 mm, there is a field of view of 4 mm in diameter. Further, since the decelerating electric field reaches the wafer through the opening 59, the secondary electrons can be attracted to the objective lens 8 efficiently. When the diameter of the opening is made small, the decelerating electric field does not reach the sample (wafer) 12, but when the wafer is inclined or there is unevenness in the specimen, such conditions are favorable and astigmatism occurs, Can be reduced.

A stage 22 is provided to observe an arbitrary place of the sample (wafer) 12. Here, it is necessary to move a large number of samples (wafers) 12 when observing a large deviation from the center point of the sample (wafer) 12. At this time, if the sample (wafer) 12 deviates from the control electrode 60, the potential of the sample (wafer) 12 changes and a constant decelerating voltage can not be applied.

In order to cope with this situation, in this embodiment, a control electrode is formed along the movement trajectory of the sample (wafer) 12. With this configuration, even if the position of the sample (wafer) 12 is changed by the stage 22, a constant deceleration voltage can be applied and the electric field generated between the objective lens 8 and the sample (wafer) It is possible to prevent the device from being damaged.

In this embodiment, it is preferable to dispose a control electrode having a size larger than the moving range of the wafer. Specifically, the diameter of the control electrode for observing the entire surface of the 8-inch wafer is 400 mm in diameter. With this configuration, even if the wafer is moved a certain distance, the voltage applied to the wafer can be kept constant.

Although the control electrode is a plate-shaped electrode in the present embodiment, it is also possible to improve the vacuum evacuation property by providing a mesh shape, a plurality of holes or slits. In this case, the hole diameter and the slit width are preferably smaller than the interval between the wafer and the control electrode.

10, the secondary electrons 62 are generated when the primary electrons 63c pass through the opening 59 of the control electrode 60 and are irradiated to the sample (wafer) 12. [ The generated secondary electrons 62 are accelerated inversely by the decelerating electric field for the primary electrons 63c and are directed upward of the objective lens 8. At this time, due to the magnetic field of the objective lens 8, it is subjected to the lens action, and is guided to the upper side of the objective lens 8 while focusing, as shown in the figure.

The induced secondary electrons 62 collide with the reflection plate 29 and generate the secondary electrons 30. The secondary electrons 30 are deflected by the electric field generated by the deflecting electrode 31 ', to which a negative potential is applied, and the deflecting electrode 31' 'to which a positive potential is applied. Since the deflection electrode 31 '' is made by a mesh, the secondary electrons 30 pass through the mesh and are detected by the scintillator 25. 32 'and 32' are deflection coils, and a magnetic field orthogonal to the electric field generated by the deflection electrodes 31 'and 31' 'is generated. The magnetic field generated by the deflection electrodes 31' and 31 ' Thereby canceling the biasing action of the pin 63b.

Although not shown, it is possible to reduce contamination (contemination) generated by scanning the primary electron beam 63c to the sample by cooling the control electrode 64. [

Fig. 11 shows another example in which a control electrode is added.

The sample holder 12 and the sample holder 12 are arranged in the order of the field emission cathode 1, the extraction electrode 2, the anode 5, the condenser lens 14, the objective lens 8, the sample 12, 22 are housed in a vacuum box body 66. The vacuum evacuation system is not shown.

Here, in a state where a negative superimposed voltage is applied to the sample 12, it is necessary to avoid the sample exchange operation by the sample exchange mechanism 67 and the atmospheric pressure inside the vacuum box body 66. In other words, the superposition voltage 13 may be applied only when the electron beam is being scanned on the sample 12.

Therefore, in the present embodiment, the first condition in which the switch 68, which is the preparation operation at the time of sample loading and replacement, is closed and the acceleration voltage 6 is applied, and the first condition in which the electric field is applied between the field emission cathode 1 and the sample 12 A second condition in which both the valve 69 and the valve 70 are opened and the valve 71 through which the sample exchange mechanism 67 passes the sample 12 to load the sample 12 on the sample stage 22 are closed The switch 72 is closed and the superimposed voltage 13 is applied to the sample 12 only when the third condition is satisfied.

The sample holder 20 and the sample stage 22 are electrically connected via a discharge resistor 73. When the switch 37 is opened, the charge charged in the sample 12 is transferred to the sample holder 20, The sample stage 22 and the sample stage 22 are grounded, so that the sample 12 is rapidly discharged under a constant time constant and the potential of the sample 12 is lowered. The discharging resistance may be built in the power source of the superimposed voltage 13.

Only when the acceleration voltage 5 can be applied and the vacuum of the vacuum box body 66 is equal to or greater than the set value under the condition that the vacuum around the field emission cathode 1 is equal to or less than the set value, ) Is opened.

In the present embodiment, it has been described that the superimposed voltage 13 is applied when all three conditions are satisfied. However, the switch 72 may be closed when one or both of these conditions are satisfied.

Fig. 12 shows another example in which a control electrode is added, and is applied to a scanning electron microscope having a sample stage 22 capable of tilting the sample. In this embodiment, the control electrode 76 is provided so as to cover the upper surface of the upper portion of the sample 75. It can also be said that they are arranged according to the shape of the objective lens depending on the viewpoint. The shape of the objective lens is formed so as not to interfere with the movement of the sample 12. In the case of the apparatus having the tilting device as shown in FIG. 12, the shape of the objective lens is sharp toward the sample 12. By forming the control electrode in accordance with the objective lens formed under such conditions, the control electrode can be disposed without disturbing the movement of the sample.

In this case, the sample (wafer) 12 is surrounded by the sample holder 20 and the control electrode 76 regardless of the position of the sample (wafer) 12 and the inclination angle. According to this structure, an electric field is not generated on the surface of the sample (wafer) 12. Reference numeral 20a denotes a state in which the sample (wafer) 12 is inclined. Reference numeral 74 denotes an inclined mechanism provided in the sample stage 22. In this embodiment, the diameter of the opening 65 of the control electrode 76 is set such that the electric field generated between the control electrode 76 and the sample (wafer) In the present invention. Further, the detection efficiency of the secondary electrons can be improved by increasing the voltage applied to the control electrode 76 by several tens of volts more than the voltage applied to the sample 12.

At this time, for the purpose of applying a voltage for deceleration to the sample, considering the action of a complex electric field based on the voltage applied to the sample and the voltage applied to the control electrode, a desired potential is applied to the sample, It is preferable to set the voltage applied to each of the sample and the control electrode.

Further, an electric field for increasing the diameter of the opening and for attracting the secondary electrons may be applied to the sample 12. In this case, the observation position is shifted due to inclination, but the inclination angle and the deviation amount are measured in advance to deflect the electron beam. Or the sample stage 22 is horizontally moved, for example, so that this deviation can be eliminated. The control electrode 76 in this embodiment is made of a nonmagnetic material so as not to affect the characteristics of the objective lens 8. [

In this embodiment, the control electrode is disposed so as to cover the inside of the sample chamber, but this arrangement is not necessarily required. In other words, it is sufficient that the sample is formed along the minimum movement range of the sample. With such a configuration, the sample is surrounded by the sample holder and the control electrode. Although the sample holder has been described above as a conductor in the present invention, for example, the conductor may be arranged above or below the sample holder. Further, in the embodiment described above, by forming a large conductor on the sample, the sample (wafer) is substantially surrounded by the control electrode and the conductor, and a constant decelerating voltage can be applied.

Fig. 13 shows another example in which the control electrode is added. In this example, the control electrode is not grounded between the objective lens 8 and the sample 12, but the objective lens 8 composed of the exciting coil 78, the box furnace 77, and the defect furnace 79 , The defective path 79 located at a position opposite to the sample 12 is electrically insulated from the box path 77 and the superimposed voltage 13 is applied thereto. The secondary electrons can be efficiently guided onto the objective lens 8 by raising the potential applied to the defects path 79 to the potential at the sample 12. [

Fig. 14 is a view for explaining an electron beam scanning deflector in which an electric field and a magnetic field are combined; Fig. When the secondary electron detector is provided on the scanning deflector, secondary electrons generated in the sample are deflected by the scanning deflector when passing through the scanning deflector. Therefore, there is a possibility that the deflection of the secondary electrons becomes large at the time of low magnification where the scanning deflection angle of the electron beam becomes large, and the electron beam collides with the inner wall of the electron beam passage, making detection impossible. The present embodiment solves this problem. The scanning deflector comprises eight electrostatic deflectors 51a to 51h and magnetic field deflectors 52a to 52d.

Now, considering the deflection in the x-axis direction, a positive electric field is applied to the electrodes 51h, 51a and 51b, and a deflection electric field Ex is generated by applying a negative electric field to the electrodes 51d, 51e and 51f in the eight electrostatic deflectors . Here, as shown in Fig. 14, a potential of a magnitude Vx is applied to the electrodes 51a and 51e, and a potential of 1/2 of them is applied to the electrodes 51h, 51b, 51d, and 51f on both sides thereof. This is a well-known method of creating a uniform electric field. Simultaneously with the electric field, a current Ix flows through the coils 52a and 52c of the magnetic field deflector 52 to produce a magnetic field Bx perpendicular to the electric field Ex as shown in the figure. The electric field (Ex) and the magnetic field (Bx) cancel the deflection for the secondary electrons coming from below, and act strongly on the primary electrons from above.

The deflection? (S) with respect to the secondary electrons coming from the lower side is a difference between the deflection? (B) by the magnetic field and the deflection? (E) by the electric field as shown below.

? (S) =? (B) -? (E)

= L / 8 Ex / Vr- (e / 2m) _1/2 BxL / Vr _1/2

Here, L is the working distance of the electric field and the magnetic field, e and m are the electron charge and mass, respectively, and Vr is the acceleration voltage when the secondary electron passes through the scanning deflector. If the ratio of Ex to Bx is expressed by the following equation, the secondary electrons coming from below will not be deflected.

Bx / Ex = (2m / e) _1/2 / 8Vr / _1/2

On the other hand, as for the deflection of the primary electrons, the electric field deflection is added to the magnetic field deflection, and the following equation is obtained. In the formula, Vo is the electron gun acceleration voltage.

? (o) =? (B) +? (E)

= (e / 2m) _1/2 BxL / Vo _1/2 + L / 8 Ex / Vo _1/2

Therefore, the deflection angle [theta] (o) under the condition of not deflecting the secondary electrons becomes as follows.

θ (o) = (e / 2m) 1/2 BxL {1 + (Vr / Vo) 1/2} / Vo 1/2

Up to this point, the deflection in the x-axis direction has been described. The deflection in the y-axis direction is also performed. That is, when the potential of the electrode 51c is Vy and the potential of the electrodes 51b and 51d is Vy / 2 _1/2 , the potential of the electrode 51g is -Vy and the potential of the electrodes 51f and 51h is -Vy / 2 _1/2 , thereby generating a deflection electric field Ey in the y-axis direction. Simultaneously, a current Iy flows through the coils 52b and 52d of the magnetic field deflector to generate a magnetic field By perpendicular to the electric field Ey. As described above, the electric field Ey and the magnetic field By are canceled with respect to the secondary electrons coming from downward, and are strong enough to combine with the primary electrons coming from above.

Actually, deflection is made by combining deflection in the x-axis direction and deflection in the y-axis direction. Therefore, as shown in Fig. 14, the potential of each deflection electrode is the sum of the deflection potential in the x-axis direction and the deflection potential in the y-axis direction. Further, in an actual apparatus, this deflector is constituted of two stages of a resilient deflector and a sub-scanning deflector, so that the deflected primary electrons pass through the lens center of the objective lens. Then, the desired primary spin speed arbitrary scanning on the sample is realized by changing the potentials (Vx, Vy) and deflection coil current (Ix, Iy) of the deflection electrode with time while maintaining the above relationship.

Next, the relationship between the lens center of the magnetic-type objective lens and the lens center of the electrostatic lens made between the acceleration cylinder and the sample will be described. 15A illustrates a problem in the case where the center CB of the magnetic-field-type objective lens 8 and the center CE of the electrostatic lens formed between the acceleration cylinder 9 and the sample 12 do not coincide with each other . In this case, the primary electron beam 11 accelerated by the rear end is deflected to pass through the center CB of the magnetic field lens, and passes through the center CE of the electrostatic lens at a distance d. When the amount of misalignment d increases, spherical aberration is exerted by the lens action of the electrostatic lens, and the main image is distorted.

15B shows an example in which the lens center CB of the magnetic-field-type objective lens 8 and the lens center CE of the electrostatic lens formed between the acceleration cylinder 9 and the sample 12 coincide with each other. In this embodiment, the upper magnetic pole 53 of the objective lens 8 is projected so as to face the sample 12, and a magnetic field is formed between the sample 12 and the acceleration cylinder 9 where the electrostatic lens is formed, The center of the lens is matched. As a result, since the primary electron beam 11 accelerated in the subsequent stage is not subjected to the lens action of the electrostatic lens, a distortion-free scanning image can be obtained.

Fig. 16 shows the structure of the objective lens 8 that more effectively realizes coincidence of the magnetic lens and the center of the electrostatic lens. In the embodiments described so far, the acceleration cylinder 9 is inserted into the electron beam passage of the objective lens 8. In this case, if the axial centers of the electrostatic lens made by the acceleration cylinder and the magnetic lens made by the objective lens are shifted from each other, the resolution will be lowered. Therefore, it is necessary to precisely match the mechanical center of both. This embodiment focuses on this point and projects the phase stimulus 53 of the objective lens 8 up to the end level of the lower magnetic pole 54 to face the sample 12. In addition, the phase pole 53 is electrically insulated from the remainder of the objective lens by the insulating plate 55, and the rear end acceleration voltage 10 is applied thereto.

According to this embodiment, since the phase stimulus and the rear stage acceleration electrode, which determine the center of the lens of the objective lens 8, are used together, there is no possibility of causing the displacement between the electrostatic lens and the magnetic field lens as described above. In addition, since the phase pole 53 of the magnetic field lens directly faces the sample 12 and the rear end acceleration voltage is applied thereto, the position of the center of the lens as well as the center axis of the electrostatic lens can be matched have.

Figure 1 is a schematic diagram of one embodiment of the present invention,

2 is an explanatory diagram of an embodiment using a reflector for detecting a secondary signal,

3 is an explanatory diagram of an embodiment in which a reflection plate is used for detecting a secondary signal and the deflection of the primary electrons is prevented by using an electric field and a magnetic field orthogonal to the attraction of the secondary electrons,

Figure 4 is a schematic view of an embodiment in which the secondary signal detector is positioned above the scanning deflector,

5 is a schematic view of an embodiment in which a secondary signal detector is provided at two positions above and below the scanning deflector,

6 is an explanatory diagram of an embodiment in which a channel plate is used for detecting a secondary signal,

FIG. 7 is an explanatory diagram of an embodiment using a scintillator for detecting a secondary signal,

8 is a schematic view of an embodiment in which the electric field intensity applied to the sample is controlled,

9 is a view showing an example of an embodiment in which a control electrode is provided on a sample,

10 is a view showing an example of a charged particle microscope having a control electrode,

11 is a view showing another example of a charged particle microscope having a control electrode,

12 is a view showing an example of a charged particle microscope in which a control electrode is formed along the inner surface of a sample chamber,

13 is a view showing an example in which a part of an objective lens magnetic path is used as a control electrode,

14 is an explanatory diagram of an embodiment in which a scanning deflector is a combination of an electric field and a magnetic field,

Fig. 15 is an explanatory diagram of an embodiment in which the center of the lens of the magnetic lens and the lens of the electrostatic lens are aligned;

16 is an explanatory diagram of an embodiment in which the magnetic poles of the magnetic lens and the acceleration cylinder are shared.

[Description of Drawings]

1: Field emission cathode 2: Extraction electrode

3: output voltage 4: emission electron

5: anode 6: electron gun acceleration voltage

7: Electronic beam 8: Objective lens

9: Acceleration cylinder 10: Backward acceleration voltage

11: primary electron beam 12: sample

13: superposition voltage 14: condenser lens

15: Scent of resident leaves 16:

17: Deceleration field 18: Aperture

19: adjusting handle 20: sample holder

21: Isolation stage 22: Sample stage

23, 30: secondary electron 24: suction electrode

25: Scintillator 26: Light guide

27: Photoelectrolytic tube 28: Center hole

29: Reflector

Claims (34)

An electron source, A scanning deflector for scanning the sample with a primary electron beam generated from the electron source, An objective lens for converging the primary electron beam, A scanning electron microscope comprising a secondary signal detector for detecting a secondary signal generated from a sample by irradiation with a primary electron beam and obtaining a two-dimensional scanning image of the sample, Acceleration means for accelerating the electron beam emitted from the electron source, An acceleration cylinder disposed in the electron beam passage of the objective lens and to which a positive voltage for accelerating the electron beam accelerated by the acceleration means is applied, Negative voltage applying means for applying a negative voltage to the sample; The negative voltage applying means, the secondary signal accelerated by the electric field formed by the voltage applied to the acceleration cylinder, or the secondary signal generated by colliding the secondary signal with the conductive reflecting plate, And a signal detector. The scanning electron microscope The method according to claim 1, The secondary signal detector includes a conductive plate having an opening through which the primary charge ratio passes, a suction means for drawing the secondary electrons reflected from the conductive plate, and a detection means for detecting the attracted secondary electrons Features a scanning microscope. 3. The method of claim 2, Wherein said attracting means forms an electric field and a magnetic field orthogonal to the electric field and eliminates any deflection of said first charge due to said electric field by the influence of said magnetic field. The method according to claim 1, Wherein the secondary signal detector is a multi-channel plate having an opening through which the primary charge ratio passes. The method according to claim 1, Wherein the secondary electron detector comprises a phosphor having an opening through which the primary electrification ratio passes and a photodetector for detecting light emission of the phosphor. The method according to claim 1, Wherein the secondary signal detector is provided between the acceleration cylinder and the scanning deflector. The method according to claim 1, And the secondary signal detector is provided between the scanning deflector and the electron source. The method according to claim 1, Characterized in that a first secondary signal detector is provided between the acceleration cylinder and the scanning deflector and a second secondary signal detector is provided between the scanning deflector and the electron source. . 9. The method of claim 8, Characterized in that a detection signal from said first or second secondary signal detector is used or a detection signal from said first and second secondary signal detectors is calculated to form a scan image, . 10. The method of claim 9, The selection of whether to use the detection signal from the first or second secondary signal detector alone or the calculation of the detection signal from the primary and the secondary secondary signal detectors is based on a scanning magnification or in advance Characterized in that it is automatically selected according to a given observation condition. The method according to claim 1, Characterized in that the scanning deflector is operated through a combination of electrostatic deflection and magnetic field deflection so as to give a desired deflection to the primary electron beam but not to deflect the secondary signal attracted from the sample Scanning microscope. The method according to claim 1, Wherein a ratio of a ratio of a rear end acceleration voltage applied to the acceleration cylinder to an electron gun voltage applied to the electron source and a voltage applied to the sample with respect to an electron gun voltage applied to the electron source are kept constant. microscope. The method according to claim 1, Wherein the center of the lens formed by the magnetic field of the objective lens and the center of the lens of the electrostatic lens formed between the acceleration cylinder and the sample coincide with each other. The method according to claim 1, Wherein the objective lens has a phase excitation pole, the phase excitation pole is electrically insulated from the remainder of the objective lens, and the insulated phase pole is replaced with the acceleration cylinder. In a scanning microscope for obtaining a two-dimensional scanning image of a sample, a. An electron source that emits a primary electron beam along the electron beam path, b. A scanning deflector for scanning the primary electron beam on the sample, c. The electron beam passage being extended, an objective lens converging the primary electron beam, d. A secondary signal detector for detecting secondary electrons generated from the sample, e. An acceleration cylinder disposed in the electron beam passage extending through the objective lens, f. A first voltage source for applying a rear end acceleration voltage for the primary electron beam to the acceleration cylinder, g. And a second voltage source for applying a negative potential to the conductive member of the sample support so as to be a decelerating electric field with respect to the primary electron beam formed between the acceleration cylinder and the sample. A scanning microscope for obtaining an image of said sample from electrons reflected or generated from said sample or reflected or generated by irradiating said sample with an electron beam emitted from said electron source, A sample support disposed below the sample and supporting a lower surface of the sample, the sample support including a conductive member underlying all of the samples; An electrode extending in a direction perpendicular to the irradiation direction of the electron beam and having a peripheral portion extending beyond the periphery of the sample and disposed above the sample having an opening for passing the electron beam; One or more electron detectors disposed on the electrode side closer to the electron source; And And a negative voltage source for applying a negative voltage substantially equal to the conductive member of the sample supporter and the electrode. 17. The method of claim 16, Wherein the electron beam is deflected to form a moving orbit on the sample, and the electrode extends in the direction of the moving orbit of the electron beam on the sample. 18. The method of claim 17, And a peripheral portion of the electrode extends beyond a periphery of the sample by an amount sufficient to include a moving region of the sample. 17. The method of claim 16, And a peripheral portion of the electrode extends beyond a periphery of the sample by an amount sufficient to include a moving region of the sample. 17. The method of claim 16, Wherein the electrode is formed so as to follow the shape of the objective lens disposed below the electron source. 17. The method of claim 16, Wherein the electrode is formed along the inner surface of the sample chamber in which the sample is enclosed. 17. The method of claim 16, Wherein a surface of the conductive member disposed under the sample is substantially the same size as the sample or larger than the sample. A scanning microscope for obtaining an image of the sample from an electron beam emitted from an electron source, the electron beam being reflected and generated from the sample or reflected or generated from the sample, A sample support including a surface on which the sample is disposed and movable in a direction perpendicular to the irradiation direction of the electron beam, the sample support including a conductive member disposed under all of the samples; The electron beam having a larger peripheral size than the peripheral portion of the region in which the sample can move, and an opening for passing the electron beam when the sample is moved by the sample support An electrode; One or more electron detectors disposed on the electrode side closer to the electron source; And And a negative voltage source for applying the same negative voltage to the conductive member of the sample support and the electrode. A scanning microscope for obtaining an image of the non-conductive sample from electrons reflected from and generated from a non-conductive sample by irradiating an electron beam emitted from the electron source, or reflected or generated, A sample table having a surface for supporting the non-conductive sample having a peripheral portion extending beyond a periphery of the non-conductive sample, the sample table including a conductive member underneath all of the samples; An electron beam having an aperture which is perpendicular to an irradiation direction of the electron beam and which is disposed between the objective lens and the sample table to converge the electron beam and has a peripheral portion larger than the peripheral portion of the sample, ; One or more electron detectors disposed on the electrode side closer to the electron source; And A scanning microscope comprising a sample table and a voltage source for applying a voltage to the electrode, Wherein a negative voltage is applied to the sample table and the electrode so as to create a space in which the sample is caught by a negative voltage and arranged so as to have few electric fields. A scanning microscope for obtaining an image of the specimen from an electron beam emitted from an electron source, the electron beam being reflected and generated from the specimen or reflected or generated, A sample having a peripheral portion extending beyond a peripheral portion of the sample and having a surface for supporting the sample, the sample being movable in a direction perpendicular to the irradiation direction of the electron beam, the sample including a conductive member table; And an objective lens for converging the electron beam and a sample table disposed between the objective lens and the sample table for converging the electron beam and having a peripheral portion larger than a peripheral portion of the region in which the sample can move, An electrode having an opening; One or more electron detectors disposed on the electrode side closer to the electron source; And A scanning type microscope including a conductive member of the sample table and a voltage source for applying a voltage to the electrode, Wherein a negative voltage is applied to the sample table and the electrode so as to create a space in which the sample is caught by a negative voltage and arranged so as to have few electric fields. A method of observing a sample using an electron beam apparatus for forming a sample image based on electrons obtained by irradiating a part of a non-conductive sample with an electron beam, Disposing the sample between two electrodes having a peripheral portion extending beyond the periphery of the sample and disposed perpendicularly to the irradiation direction of the electron beam onto the sample; Disposing one or more electron detectors on the electrode side closer to the electron source; And And applying a negative voltage to the two electrodes to make the region in which the sample is disposed a negative voltage region having substantially no electric field, and irradiating the sample with the electron beam. A scanning microscope for obtaining a sample image from an electron beam emitted from an electron source, the electron beam reflected and generated from the sample or reflected or generated by irradiating the sample, A sample support disposed above the sample supporting the lower surface of the sample and having a conductive member underlying all of the sample; An objective lens that focuses the electron beam and has a magnetic pole divided into an upper magnetic pole and a lower magnetic pole; And And a negative voltage source for applying a negative voltage substantially equal to the conductive member of the sample support and the lower magnetic pole, Wherein the lower magnetic pole has a peripheral portion extending perpendicularly to the irradiation direction of the electron beam and extending beyond a peripheral portion of the sample. A scanning microscope for obtaining an image of the wafer from an electron beam reflected or generated from the wafer by irradiating the wafer with an electron beam emitted from the electron source, A sample support disposed below the wafer, the support supporting a lower surface of the wafer and including a conductive member underlying both of the wafers; An electrode having an extension extending perpendicularly to the irradiation direction of the electron beam and extending beyond the periphery of the wafer, the electrode having an opening through which the electron beam passes; One or more electron detectors disposed on the electrode side closer to the electron source; And And a negative voltage source for applying a negative voltage substantially equal to the conductive member of the sample support and the electrode. A scanning electron microscope for obtaining an image of said sample from electrons generated from a sample by an electron beam emitted by an electron source and reflected or generated or reflected therefrom, And an objective lens for converging the electron beam, wherein the objective lens has an electrode divided into an upper magnetic pole and a lower magnetic pole; And And a positive voltage is applied to the phase magnetic pole. 30. The method of claim 29, Wherein the scanning electron microscope has an optical axis extending through the objective lens, each of the phase poles and the bottom poles of the objective lens has a magnetic pole end, And the magnetic pole end of the phase magnetic pole is disposed closer to the optical axis than the magnetic pole end of the lower magnetic pole. 30. The method of claim 29, Wherein the phase magnetic pole is connected to the lower magnetic pole via an insulator. A scanning electron microscope for obtaining an image of said sample from electrons generated from a sample by an electron beam emitted by an electron source and reflected or generated or reflected therefrom, Wherein at least a portion of one of the stimuli has a different polarity when viewed in a direction perpendicular to the irradiation direction of the electron beam, and the objective lens includes two stimuli, And is further arranged on the side of the electron beam, And a positive voltage is applied to the one magnetic pole. 33. The method of claim 32, And the one magnetic pole is connected to the other magnetic pole through an insulator. 33. The method of claim 32, Characterized in that said portions of the two stimuli are separated by a gap opening towards the sample.