JP2002216686A - Electron gun, electron source, electron beam apparatus and method for correcting optical axis of electron beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently provide an electron gun, an electron source and an electron beam apparatus without displacement of an optical axis of an electron beam and improve a productivity and a maintainability of the electron gun and the electron beam apparatus. SOLUTION: A structure can arbitrarily set a relative position between a needle electrode and a drawn electrode 5 by an optical axis correcting screw 17. A tilt of the needle electrode is previously measured by an optical microscope or other means. The needle electrode and the drawn electrode are decentered so as to be deflected at the same opposite angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device to which an electron beam is applied, such as an electron microscope and an electron beam lithography device, and an electron gun and an electron source used in these devices.

[0002]

2. Description of the Related Art A field emission type electron source for generating an electron beam by applying a strong electric field to a needle electrode having a sharply pointed tip, and a thermal field emission type electron source for simultaneously applying an electric field and heating by heating are made of heat. Compared to an electron emission type electron source, it has higher luminance and longer life, and has uniform energy of emitted electrons, so that it is suitable for an electron microscope or the like that requires high resolution. However, the electron beam emission angles of the field emission type electron source and the thermal field emission type electron source have a solid angle of about 0.3 to 0.5 sr. .03-0.0
The electron beam in a portion outside the range is about 5 sr, which has a large energy variation and contains a lot of noise components, and thus is not suitable for use in an electron beam application device such as an electron microscope. Therefore, in order to ensure the performance of the electron beam device, it is necessary to select and use only the radiated electrons near the center among the electron beams emitted from the electron source.

[0003] FIG. 16 shows that the needle-like electrode is made of a material having an axial orientation <3.
10> is a schematic cross-sectional view of a field emission electron source using a tungsten (hereinafter referred to as W) single crystal. The field emission type electron source includes a needle electrode 1 made of W single crystal, a filament 2 made of W polycrystalline fine wire, a current introduction terminal 3,
It is composed of a filament insulator 4. When a strong positive electric field is applied to the extraction electrode 5 with respect to the extraction electrode 5 using the extraction power source 6, W (31) formed at the tip of the extraction electrode 1 is formed.
Electron emission can be obtained from the 0) plane. The optical axis 105 of the electron beam emitted from the electron source is usually the center axis 10 of the needle electrode.
Matches 4. Therefore, the needle electrode 1 is connected to the extraction electrode center axis 1.
01, the inclination θe of the electron beam optical axis 105 with respect to the extraction electrode center axis 101 is θw.
Becomes equal to

FIG. 17 is a schematic sectional view of an electron gun equipped with the field emission type electron source or the thermal field emission type electron source. The electron source 11 includes a flange 1 inside an electron gun container 12.
3, it is installed at a position facing the extraction electrode 5 via the cylinder 21 and the insulator 14. The cylinder 21 is connected to the flange 13 by a bellows 22 and has a structure capable of moving in a horizontal direction while maintaining an internal vacuum, and the electron beam optical axis 105 due to an angular displacement of a needle electrode belonging to the electron source 11. When the inclination of θe with respect to the apparatus central axis 100 occurs, the four shaft adjusting screws 23 arranged at a 90 ° pitch in the circumferential direction.
Thereby, the electron source 11 is moved in parallel with the cylinder 21, the insulator 14, and the extraction electrode 5, and adjustment is performed so that the electron beam optical axis 105 passes through the aperture located at the central axis 100 of the apparatus. However, since the electron beam that has passed through the aperture still has a slope of θe, the electron beam deviates from the apparatus central axis 100 as it is. To correct this, a deflecting means 1 using a principle such as electrostatic deflection or electromagnetic deflection, which is disposed on the mirror 62, is used.
8 to electromagnetically deflect the electron beam to the central axis 100 of the apparatus.
It is necessary to match.

[0005]

The electron beam optical axis of an electron beam emitted from a field emission type electron source or a thermal field emission type electron source coincides with the center axis of a needle-shaped electrode. The mounting accuracy of the electrode is important. However, the needle-shaped electrode is usually joined to the filament by spot welding in many cases, and there is a limit to the accuracy that can be achieved due to its structure, and the deviation of the electron beam optical axis due to the inclination of the needle-shaped electrode should be avoided. I can't pass. In the prior art, as described above, in addition to the parallel movement of the electron source and the extraction electrode in the electron gun, the electron beam is electromagnetically deflected by the deflecting means disposed on the mirror body side, and deviates from the central axis of the apparatus. It is necessary to correct the electron beam so that it coincides with the center axis of the device, which complicates the structure of the electron gun and the device using the electron beam,
The operation of correcting the optical axis of the electron beam using the above means is a factor that prolongs the stoppage time of the apparatus when manufacturing the apparatus or replacing the electron source.

In view of the above problems, the present invention corrects the electron beam optical axis deviation caused by the above-described needle electrode mounting accuracy without using a complicated mechanism, and provides an electron beam with a small electron beam optical axis deviation. An object of the present invention is to provide a gun, an electron source, and an electron beam device, and to further improve the productivity and maintainability of the electron gun and the electron beam device.

[0007]

In order to solve the above-mentioned problems, the present invention has a structure in which the relative positions of a needle electrode and an extraction electrode belonging to an electron source can be arbitrarily set, and the eccentricity of the needle electrode and the extraction electrode is determined. The optical axis of the electron beam is adjusted by using the deflection effect of the electron beam. The inclination of the needle electrode is measured in advance by an optical microscope or other means, and the needle electrode and the extraction electrode are eccentric so that they are deflected by the same angle in the opposite direction. The electron beam can be corrected parallel to the central axis of the device.

That is, an electron gun according to the present invention comprises a field emission type electron source or a thermal field emission type electron source having a needle-like electrode, and an extraction electrode for generating an electron beam by applying a strong electric field to the needle-like electrode. The electron gun provided with (1) has a function of arbitrarily setting the amount of eccentricity between the needle electrode and the extraction electrode by changing the fixing position of the extraction electrode.

An electron gun according to the present invention also includes a field emission type electron source or a thermal field emission type electron source having a needle electrode,
In an electron gun having an extraction electrode for generating an electron beam by applying a strong electric field to the needle electrode, the needle electrode is changed by changing a fixed position of the field emission electron source or the thermal field emission electron source. And a function of arbitrarily setting the amount of eccentricity of the extraction electrode.

An electron source according to the present invention is a thermoelectric field emission type electron source having a needle-like electrode and a suppressor electrode for suppressing the emission of thermoelectrons, wherein the eccentricity of the suppressor electrode and the needle-like electrode is arbitrarily set. It has a function to perform. An electron beam apparatus according to the present invention includes an electron beam apparatus including a sample stage for holding a sample, an electron gun, and an electron lens for converging an electron beam generated from the electron gun and irradiating the electron beam onto the sample. As the gun, the above-described electron gun or the above-described electron gun including the electron source is used.

The method for correcting the optical axis of an electron beam according to the present invention is directed to a field emission type electron source or a thermal field emission type electron source having a needle-like electrode and a drawer for generating an electron beam by applying a strong electric field to the needle-like electrode. An electron beam optical axis correction method for correcting an optical axis shift of an electron beam emitted from an electron gun having an electrode and an electron beam caused by an angle shift of a needle electrode belonging to a field emission type electron source or a thermal field emission type electron source. The electron beam optical axis shift is corrected by decentering the extraction electrode in a direction to offset the electron beam optical axis shift.

The method of correcting an optical axis of an electron beam according to the present invention is also intended to generate an electron beam by applying a strong electric field to a field emission electron source or a thermal field emission electron source having a needle electrode and a needle electrode. An electron beam optical axis correction method for correcting an optical axis shift of an electron beam emitted from an electron gun having an extraction electrode of the type described above, wherein an angle shift of a needle electrode belonging to a field emission type electron source or a thermal field emission type electron source is performed. The electron beam optical axis shift is corrected by decentering the electron source in a direction to offset the resulting electron beam optical axis shift.

The electron beam optical axis correction method according to the present invention corrects the optical axis shift of an electron beam emitted from a thermal field emission type electron source having a needle electrode and a suppressor electrode for suppressing emission of thermoelectrons. In the electron beam optical axis correction method, the electron source is connected to the electron gun by decentering the needle electrode and the suppressor electrode in a direction to offset the electron beam optical axis deviation caused by the angular deviation of the needle electrode belonging to the electron source. The amount of eccentricity of the needle electrode and the extraction electrode when assembled is indirectly set to correct the electron beam optical axis shift.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In order to facilitate understanding, in the following drawings, portions having the same functions will be described with the same reference numerals. First, the principle of electron beam optical axis correction will be described with reference to FIGS. When the tip of the needle electrode 1 is located on the central axis 101 of the extraction electrode 5, the electron beam optical axis 1
05 coincides with the central axis 104 of the needle electrode. Therefore, FIG.
As shown in FIG. 6, when the needle electrode 1 is attached with a deviation of θw from the extraction electrode center axis 101, the inclination θe of the emitted electron beam optical axis 105 becomes equal to θw. However, when the tip of the needle electrode 1 is eccentric from the center axis 101 of the extraction electrode as shown in FIG. 1, the electron beam optical axis 105 is deflected by the bias of the electric field and deviates from the needle electrode center axis 104. In FIG. 1, φd is the hole diameter of the extraction electrode 5, a is the vertical distance between the needle electrode 1 and the extraction electrode 5, Ve is the extraction voltage,
e represents the amount of eccentricity between the needle electrode 1 and the extraction electrode 5, and θc represents the amount of deflection.

FIG. 2 shows an example of the relationship between the amount of deflection θc and the amount of eccentricity e. The horizontal axis in FIG. 2 represents the amount of eccentricity between the needle electrode and the extraction electrode, e.
_TH , and the vertical axis represents the deflection amount θc [゜]. When the hole diameter φd _{H of} the extraction electrode, the vertical distance a between the tip of the needle electrode and the extraction electrode, and the extraction voltage Ve are constant, the deflection amount θc is almost proportional to the eccentricity e, and the relationship θc = α × e is recognized. Can be As shown in the figure, a: 0.35 mm, φd _H : 1.0 mm, V
e: Under the condition of 2.0 to 2.5 kV, the proportionality constant α: 0.
A value of 03 [° / μm] was confirmed.

Utilizing the above principle, the optical axis of the electron beam emitted from the inclined needle electrode is deflected by the eccentricity of the needle electrode and the extraction electrode so that it is parallel to the central axis of the extraction electrode. FIG. 3 shows a schematic diagram of the correction method. By modifying the above relational expression, e = θc / α is obtained. Therefore, in order to correct the electron beam optical axis shift due to the inclination θw of the needle electrode, an eccentricity of e = θw / α may be given as an offset amount between the needle electrode and the extraction electrode. For example, when the needle electrode 1 is inclined by 1.5 ° in the (−) direction under the above-described conditions, the tip of the needle electrode 1 is eccentric in the (+) direction by 50 μm with respect to the extraction electrode 5. The electron beam optical axis 105 corrected parallel to the central axis of the extraction electrode can be obtained.

FIG. 4 is a longitudinal sectional view for explaining an example of an electron gun according to the present invention, and its AA 'sectional view. In the electron gun of this example, an electron source and an extraction electrode are arranged on the same flange, and have a function of arbitrarily decentering the extraction electrode with respect to the electron source. The electron source 11 is inside the electron gun container 12,
It is fixed on the flange 13 via an insulator 14 with a vacuum sealing bolt 16. The extraction electrode 5 is mounted at a position facing the electron source 11, and is connected to the extraction electrode base 1 by four optical axis correction screws 17 arranged at a 90 ° pitch on the circumference.
5 (in a direction perpendicular to the electron source central axis 102).

FIG. 5 is a view for explaining the inclination measurement of the needle electrode belonging to the electron source 11. Before assembling the electron source into the electron gun, the needle electrode center axis 1 with respect to the electron source center axis 102
04 is measured separately in the X and Y directions.
Since the center axis 102 of the electron source is a virtual axis, the measurement of the amount of tilt is actually guaranteed in terms of mechanical dimensional accuracy such as the side surface of the filament insulator 4 or the side surface of the suppressor electrode 52 in the case of an electron source with a suppressor electrode. It is performed based on the surface that is An optical microscope with a length measuring function is used for the measurement.
Measurement with a scanning electron microscope is also effective for performing more accurate axis correction.

As a result of the measurement, the center axis 104 of the needle electrode is set to θw in the X and Y directions with respect to the center axis 102 of the electron source.
When there is a tilt amount of x and θwy, the extraction electrode 5 is fixed at a position eccentric to the needle electrode 1 belonging to the electron source 11 by ex = θwx / α and ey = θwy / α in the X and Y directions, respectively. I do. α is a constant determined by the use conditions of the electron source. Confirmation of ex and ey is performed by setting an optical microscope on the central axis of the apparatus. Α = shown in FIG.
In the example of 0.03, since the deflection amount of the electron beam optical axis per 1 μm of eccentricity is 0.03 °, if the eccentricity ex and ey can be set with an accuracy of ± 10 μm, the electron can be adjusted with an accuracy of ± 0.3 °. The amount of linear optical axis deflection can be controlled.

By the above operation, an electron beam corrected to be parallel to the center axis 102 of the electron source can be obtained even if the electron source has an inclined needle electrode. The electron beam 105 that has passed through the aperture located at the center of the electron gun container 12 and has reached the inside of the mirror body 62 has already been corrected so as to coincide with the central axis 100 of the apparatus. No special deflection means is required for axis correction.

FIG. 6 is a longitudinal sectional view for explaining another example of the electron gun according to the present invention, and its AA 'sectional view. The electron gun of this example has an electron source and an extraction electrode arranged on the same flange, and has a function of adjusting the eccentricity of the needle electrode and the extraction electrode belonging to the electron source by making the electron source movable. The extraction electrode 5 is located in the electron gun container 12 and is disposed on the flange 13 via the insulator 14. The electron source 11 is mounted at a position facing the extraction electrode 5 and includes four optical axis correction screws 17 arranged at a 90 ° pitch on the circumference.
Accordingly, it is possible to move in the horizontal direction (the direction perpendicular to the electron source central axis 102).

The inclination of the needle electrode belonging to the electron source 11 is measured in advance by an optical microscope or other measuring means, and the electron beam is deflected in a direction opposite to the expected inclination of the optical axis of the electron beam. By eccentrically fixing the source 11 with respect to the extraction electrode 5, an electron beam 105 corrected in a direction parallel to the electron source central axis 102 can be obtained. Further, the light passes through an aperture located at the center of the electron gun container 12 and passes through the mirror body 6.
The electron beam 105 that has reached the inside of the device 2
Therefore, no special deflecting means is required in the mirror body 62 for correcting the optical axis of the electron beam.

FIG. 7 is a schematic sectional view showing an example of the electron source according to the present invention. The electron source of this example is a thermoelectric field emission type electron source using a W single crystal having an axial orientation of <100> as a material of a needle-like electrode and having a suppressor electrode for suppressing emission of thermoelectrons. It has a structure in which the amount of eccentricity of the needle electrode can be set arbitrarily.

The thermal field emission type electron source includes a needle electrode 1, a filament 2, a current introduction terminal 3, a filament insulator 4, a suppressor electrode 52, and an optical axis correction screw 17. When a current is supplied to the filament 2 through the current introduction terminal 3 by the filament heating power supply 53, a coating substance supply source (not shown) generated on the side surface of the needle electrode 1
The zirconium oxide is thermally diffused to the surface of the needle electrode 1. The zirconium oxide has a function of lowering the work function of the W (100) plane formed at the tip of the needle electrode 1, and in this state, the extraction electrode 5
When a positive voltage is applied to the needle electrode 1, electron emission with a narrow energy width can be selectively obtained from the W (100) plane formed at the tip of the needle electrode 1. When the suppressor electrode 52 applies a negative voltage to the needle-shaped electrode 1 by the suppressor power supply 54, the energy generated from the filament 2 and the surrounding high-temperature portion varies greatly and is considered to be of low utility value. It has the function of shielding the existing thermoelectrons. Since the needle-shaped electrode 1 is always kept at a temperature of a hundred thousand K by the heating of the filament 2, there is no adsorption of gas molecules in the electron gun container.
Since zirconium oxide is continuously supplied from the coating material supply source by thermal diffusion, a low work function is maintained until the coating material is depleted, and stable electron emission is obtained. As coating materials for lowering the work function of the W (100) plane, those using oxides such as titanium, barium and scandium in addition to zirconium oxide have been studied for practical use or for practical use.

The needle electrode 1 is attached to the current introducing terminal 3 via the filament 2,
Are arranged so that the tip of the needle electrode 1 protrudes by a required length from a hole formed at the center thereof, and the suppressor electrode is provided by four optical axis correction screws 17 arranged at a 90 ° pitch on the circumference. The center axis of 52 and the eccentricity e of the needle electrode 1 can be set arbitrarily.

FIG. 8 shows a needle electrode 1 and a suppressor electrode 5.
FIG. 3 is a detailed diagram showing a relative positional relationship between a second electrode 2 and an extraction electrode 5. The amount of eccentricity between the needle electrode 1 and the suppressor electrode 52 is e
_TS , the eccentricity of the needle electrode and the extraction electrode is represented by e _TH , and the eccentricity of the suppressor electrode and the extraction electrode is represented by e _{S -H} .

The hole diameter φd _{S of the} suppressor electrode, the hole diameter φd _{H of} the extraction electrode, the vertical distance a between the tip of the needle electrode and the extraction electrode, the distance A between the suppressor electrode and the extraction electrode, the extraction voltage V
e (not shown), the suppressor voltage Vs (not shown) is fixed, and the eccentricity e _TS of the needle electrode 1 and the suppressor electrode 52 and the eccentric amount e _{TH of the} needle electrode 1 and the extraction electrode 5 are set.
Beam optical axis 105 when each is independently changed
FIG. 9 shows an example of a change in the deflection amount θc. expressed with respect to a change in the e _TH an e _TS zero, the deflection amount with respect to e _TH by θc (TH). Also, _let e _TH be zero and e
_{When the TS} is changed, the deflection amount with respect to e _TS is θc
Expressed by (TS). As can be seen from the figure, a: 0.35
mm, A: 0.6 mm, φds: 0.4 mm, φdH:
1.0 mm, Ve: 2.0 to 2.5 kV, Vs: 0.1
Under the condition of １．０1.0 kV, the amount of deflection depends only on the amount of eccentricity e _T-H between the needle electrode and the extraction electrode, and is hardly affected by the eccentricity e _T-S between the needle electrode and the suppressor electrode.

By ensuring the dimensional accuracy of the outer periphery of the suppressor electrode and the parts on the electron gun side into which it is incorporated,
When the electron source is incorporated in the electron gun, e _SH = 0, ie,
If the structure is such that the hole of the suppressor electrode and the hole of the extraction electrode are located on the same axis, e _{T− S} (eccentricity of the needle electrode and the suppressor electrode) = e _TH (eccentricity of the needle electrode and the extraction electrode) ). Utilizing this property, the inclination θw of the needle electrode 1 is measured by an optical microscope or other measuring means in the process of manufacturing the electron source, and the inclination θe (= θw) in the direction opposite to the expected inclination of the electron beam optical axis is measured. When the electron source is assembled by adjusting the eccentricity e _TS of the suppressor electrode 52 and the needle electrode 1 so that the electron beam is deflected, the extraction electrode 5 is indirectly mounted when the electron source is incorporated in the electron gun. And the required amount of eccentricity of the needle electrode 1 can be set.

FIG. 10 is a sectional view of an electron gun equipped with the electron source 51 shown in FIG. Since the optical axis correction has already been completed in the manufacturing process of the electron source 51, the insulator 14
The required amount of eccentricity is automatically set between the needle electrode belonging to the electron source 51 and the extraction electrode 5 only by incorporating the inner periphery of the electrode and the outer periphery of the suppressor electrode 52 using the fitting. Since the electron source is a consumable part, replacement work is periodically performed.
If an appropriate amount of eccentricity is given in advance between the suppressor electrode and the needle electrode in the manufacturing process of the electron source, it is not necessary to correct the electron beam optical axis every time the electron source is replaced, and the stopping time of the device can be reduced. Can be shortened.

FIG. 11 is a schematic view showing an example of a scanning electron microscope according to the present invention, which is equipped with the above-described electron gun. This device has an electron gun 61 as a main component,
The electron gun 61, the mirror body 62, and the sample chamber 63 are evacuated by a vacuum pump (not shown).
The electron beam 105 emitted from the electron source 11 (or 51) enters the mirror 62 in parallel with the central axis. Further, in the mirror body 62, it is narrowed down by the converging lens 621 and the objective lens 623, and focuses on the surface of the sample 632 set on the sample stage 631. Secondary electrons 106 generated when the sample surface is scanned by the scanning deflector 622 are detected by the secondary electron detector 6.
24, amplified and sent to the control unit to obtain image information.

Since the electron beam 105 has already been corrected so as to be parallel to the central axis of the converging lens 621 at the time of entering the mirror 62, no special deflecting means is required inside the mirror 62. As a result, the reliability of the device is improved and the device can be downsized. The electron gun and the electron source can be applied to a transmission electron microscope, an electron beam lithography apparatus, and the like in addition to the above-mentioned scanning electron microscope.

Next, the manufacturing process of the scanning electron microscope will be described. FIG. 12 shows a conventional manufacturing process, and FIG. 13 shows a manufacturing process according to the present invention. In the prior art shown in FIG. 12, (step 1) assembling of an electron gun, (step 2) assembling of an electron source,
(Step 3) Evacuation is performed, and (Step 4) electron beam emission is started. (Step 5) The optical axis is adjusted by the axis adjusting mechanism of the electron gun. (Step 6) When the measurement of the radiated current and the single performance test such as the withstand voltage test are passed, (Step 7) the electron beam emission is temporarily stopped. (Step 8) Mount the electron gun on the mirror body.
(Step 9) After the restart of the electron beam emission, (Step 10) the image observation of the sample becomes possible only after the optical axis adjustment by the deflection function on the mirror side is completed. (Step 11) The apparatus is completed through comprehensive adjustment such as magnification adjustment and resolution test.

FIG. 13 is a manufacturing process diagram of a scanning electron microscope employing the electron gun according to the present invention. Separately from the manufacture of the electron gun, the inclination of the needle electrode belonging to the electron source is measured, and the amount of eccentricity required to correct the expected inclination of the electron beam optical axis is calculated. The electron beam corrected parallel to the central axis of the extraction electrode can be obtained immediately after the start of the electron beam emission by fixing the needle electrode and the extraction electrode with the required eccentricity at the stage of assembling the electron source. . This eliminates the necessity of adjusting the optical axis of the electron beam shown in (Step 5) and (Step 10) of the prior art shown in FIG. 12, which is effective in shortening the manufacturing time of the electron gun and the apparatus body.

Next, a description will be given of a working process when the electron source of the active electron beam device reaches its end of life and is replaced with a new one. In the prior art shown in FIG. 14, after (Step 1) the apparatus is stopped, (Step 2) the inside of the electron gun is opened to the atmosphere to replace the electron source, (Step 3) evacuation is resumed, and (Step 4) electron beam emission is performed. After the restart, when (step 5) the optical axis adjustment by the axis adjustment mechanism of the electron gun and (step 6) the optical axis adjustment by the deflection function on the mirror body are completed, the operation of the apparatus can be restarted.

On the other hand, FIG. 15 shows a working process when the electron source according to the present invention is adopted. In the manufacturing process of the electron source, the amount of eccentricity is given between the needle electrode and the suppressor electrode based on the inclination angle of the needle electrode in advance, so that the electron source is simply incorporated according to the fitting of the electron source mounting portion. The required amount of eccentricity is automatically given between the needle electrode belonging to the electron source and the extraction electrode. As a result, an electron beam corrected in parallel with the central axis of the extraction electrode can be obtained immediately after the start of the electron beam emission, so that the prior art (step 5) shown in FIG.
Also, the electron beam optical axis adjustment work shown in (Step 6) becomes unnecessary. Therefore, since the apparatus stop time due to the exchange of the electron source can be minimized, the present invention is particularly effective for an electron beam apparatus used in a production line such as a semiconductor inspection electron microscope which operates continuously for 24 hours.

[0036]

According to the present invention, no special electron beam deflecting means is required on the side of an apparatus utilizing an electron beam, and the electron beam caused by the inclination of the needle electrode in the assembling stage of the electron gun or the electron source. Optical axis deviation can be predicted in advance and corrected in advance, and it is possible to efficiently obtain an electron beam with low noise, high current density and uniform energy, and at the same time, to use an electron gun and an electron beam device. This is also effective for improving productivity and reducing the downtime of the apparatus when replacing the electron source.

In addition, since a mechanism for adjusting the position in the horizontal plane from the atmosphere side, which is indispensable for the electron gun according to the prior art, becomes unnecessary, the size of the electron gun can be reduced. It is also effective in improving reliability, such as stabilizing radiation current and suppressing discharge by reducing the amount of gas emitted and improving the degree of vacuum. Further, a deflection means for correcting the optical axis of the electron beam inside the mirror body is not required, which is advantageous for miniaturization of the entire apparatus, and improvement in vibration resistance can be expected.

[Brief description of the drawings]

FIG. 1 is a view for explaining the relationship between the eccentricity of a needle electrode and the deflection of an electron beam optical axis.

FIG. 2 is a diagram illustrating an example of a relationship between a deflection amount θc and an eccentric amount e.

FIG. 3 is an explanatory diagram of a method of correcting an electron beam optical axis.

FIG. 4 is a longitudinal sectional view illustrating an example of an electron gun according to the present invention, and its AA ′ sectional view.

FIG. 5 is a view for explaining tilt measurement of a needle electrode belonging to an electron source.

FIG. 6 is a longitudinal sectional view for explaining another example of the electron gun according to the present invention, and its AA 'sectional view.

FIG. 7 is a schematic sectional view showing an example of an electron source according to the present invention.

FIG. 8 is a detailed diagram showing a relative positional relationship between a needle electrode, a suppressor electrode, and an extraction electrode.

FIG. 9 is a diagram showing an example of a change in the amount of deflection of the electron beam optical axis when the amount of eccentricity of the needle electrode and the suppressor electrode and the amount of eccentricity of the needle electrode and the extraction electrode are independently changed.

FIG. 10 is a sectional view of an electron gun equipped with the electron source shown in FIG. 7;

FIG. 11 is a schematic view showing an example of a scanning electron microscope according to the present invention.

FIG. 12 is an explanatory view of a manufacturing process of a conventional scanning electron microscope.

FIG. 13 is an explanatory diagram of a manufacturing process of the scanning electron microscope according to the present invention.

FIG. 14 is a work process diagram of conventional electron source replacement.

FIG. 15 is a work process diagram of an electron source exchange according to the present invention.

FIG. 16 is a schematic sectional view of a conventional field emission electron source.

FIG. 17 is a schematic sectional view of an electron gun equipped with a conventional field emission electron source or thermal field emission electron source.

[Explanation of symbols]

1: needle electrode, 2: filament, 3: current introduction terminal,
4: filament insulator, 5: extraction electrode, 6: extraction power supply,
100: central axis of device, 101: central axis of extraction electrode, 102
... Center axis of electron source, 103 ... Center axis of suppressor electrode, 1
04: Needle electrode central axis, 105: Electron beam optical axis, 106:
Secondary electron, 11: Field emission type electron source or thermal field emission type electron source, 12: Electron gun container, 13: Flange 14: Insulator, 15: Extraction electrode base, 16: Vacuum sealing bolt, 17: Optical axis Correction screw, 18 ... deflection means, 2
DESCRIPTION OF SYMBOLS 1 ... cylinder, 22 ... bellows, 23 ... shaft adjustment screw, 51 ... electron source with a suppressor electrode, 52 ... suppressor electrode, 5
3: filament heating power supply, 54: suppressor power supply,
Reference numeral 61: electron gun, 62: mirror body, 63: sample chamber, 64: high-voltage power supply, 65: control unit, 621: converging lens, 622: scanning deflector, 623: objective lens, 624: secondary electron detector, 631 … Sample stage, 632… Sample

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Kokubo 882-mo, Ota-shi, Hitachinaka-shi, Ibaraki Pref. Within the Measuring Instruments Group of Hitachi, Ltd. BB03 CA16 LA10 5C030 AA09 AB02 AB03 5F056 EA02

Claims (7)

[Claims] 1. An electron gun comprising: a field emission electron source or a thermal field emission electron source having a needle electrode; and an extraction electrode for generating an electron beam by applying a strong electric field to the needle electrode. The electron gun according to claim 1, further comprising a function of arbitrarily setting an eccentric amount between the needle electrode and the extraction electrode by changing a fixing position of the extraction electrode. 2. An electron gun comprising: a field emission electron source or a thermal field emission electron source having a needle electrode; and an extraction electrode for applying a strong electric field to the needle electrode to generate an electron beam. The electron gun according to any one of claims 1 to 3, further comprising a function of arbitrarily setting the amount of eccentricity between the needle electrode and the extraction electrode by changing a fixed position of the field emission electron source or the thermal field emission electron source. 3. A thermoelectric field emission type electron source having a needle electrode and a suppressor electrode for suppressing emission of thermoelectrons, wherein a function of arbitrarily setting an eccentric amount of the suppressor electrode and the needle electrode is provided. A thermal field emission type electron source characterized by having: 4. An electron beam apparatus comprising: a sample stage for holding a sample; an electron gun; and an electron lens for converging an electron beam generated from the electron gun and irradiating the electron beam onto the sample. An electron beam apparatus using the electron gun according to claim 1 or 2 or an electron gun including the electron source according to claim 3. 5. An electron gun comprising a field emission type electron source or a thermal field emission type electron source having a needle electrode and an extraction electrode for applying a strong electric field to said needle electrode to generate an electron beam. An electron beam optical axis correction method for correcting an optical axis deviation of an emitted electron beam, comprising: correcting an electron beam optical axis deviation caused by an angular deviation of a needle electrode belonging to the field emission type electron source or the thermal field emission type electron source. An electron beam optical axis correction method, wherein an electron beam optical axis shift is corrected by decentering an extraction electrode in a canceling direction. 6. A field emission type electron source or a thermal field emission type electron source having a needle-like electrode and an electron gun provided with an extraction electrode for generating an electron beam by applying a strong electric field to said needle-like electrode. An electron beam optical axis correction method for correcting an optical axis deviation of an electron beam to be performed, wherein an electron beam optical axis deviation caused by an angular deviation of a needle electrode belonging to the field emission type electron source or the thermal field emission type electron source is offset. And correcting the electron beam optical axis deviation by decentering the electron source in the direction of the electron beam. 7. An electron beam optical axis correction method for correcting an optical axis shift of an electron beam emitted from a thermal field emission type electron source having a needle electrode and a suppressor electrode for suppressing emission of thermoelectrons, By decentering the needle electrode and the suppressor electrode in a direction to offset the electron beam optical axis shift caused by the angle shift of the needle electrode belonging to the electron source, the needle when the electron source is incorporated in an electron gun An electron beam optical axis correction method, comprising indirectly setting the amount of eccentricity between the shape electrode and the extraction electrode to correct the electron beam optical axis deviation.