JP2000285839A - Electron gun, and exposure device and exposure method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly prevent deterioration of aberration of emission electrons by forming at least one of electrodes by use of a high magnetic permeability material having a magnetic permeability of a specified value or more. SOLUTION: A suppressor 2 and extractor 3 which are electrodes, an outside magnetic pole 7b, and an inside magnetic pole 7c are formed of a high magnetic permeability material having a magnetic permeability (at 0 deg.C) of 10 or more such as electromagnetic soft iron, pure iron, silicon steel, permalloy or the like. A magnetic pole unit 7 arranged in the rear of the extractor 3 is formed of a permanent magnet 7a, the outside magnetic pole 7b and the inside magnetic pole 7c. The extractor 3 is integrally formed with the outside magnetic pole 7b through an insulator 9a, and the suppressor 2 is integrally formed with the inside magnetic pole 7c through an insulator 9b. Since the flow of magnetic flux is in a narrow gap between the suppressor 2 and the extractor 3, and this position is extremely close to Z-axis, a steep magnetic field having a high peak can be applied to the vicinity of an emitter 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun and an observation device (SEM or TEM) using the electron beam.
Etc.) and a fine pattern exposure apparatus (EB exposure apparatus) for producing semiconductor devices.

[0002]

2. Description of the Related Art In general, a fine pattern exposure apparatus used in the production of a semiconductor device requires high brightness in order to obtain a fine pattern.

For this purpose, it is necessary to irradiate the wafer with a high current density, but it is desirable that the irradiation angle be small due to aberration of the electron lens electrode.

[0004] The brightness is the electron current density (current angular density) per unit area. However, since the value of this brightness cannot be increased by the lens of the electron optical system after the electron gun,
It is important that the electron gun has high brightness. A major factor that lowers the brightness of the electron gun is the aberration of the electron lens electrode in the electron gun.

The aberration of the electron lens electrode can be roughly classified into
(A) geometric aberration (spherical aberration, axial asymmetric aberration), (b) diffraction aberration, and (c) chromatic aberration. Of these aberrations, reduction of chromatic aberration (chromatic aberration is proportional to the energy width) is particularly important as fine processing is performed.

[0006] Chromatic aberration occurs when the acceleration voltage of the anode of the electron gun and the lens current of the electron lens electrode fluctuate, and as a result, the magnification and the rotation angle vary depending on the distance from the beam axis, and the image is blurred. Would. Therefore, in order to reduce chromatic aberration, both the acceleration voltage power supply and the electron lens electrode excitation current power supply need to have high stability.

An electron gun used in an EB exposure apparatus or the like is a thermoelectron using a conventional LaB6 (lanthanum hexaboride) as a FEG (field emission electron gun) / TFEG (thermal field emission electron gun) in terms of performance. Energy width is 1 compared to a radiation gun
/ 5, which is a preferable performance.

However, the tip of the emitter (cathode) of the field emission type electron gun and the thermal field emission type electron gun is formed in a very small needle shape (radius of 1 μm or less), and the electrons radiate from the cathode and diverge. I do. For this reason, in order to obtain a large current, it is necessary to collect electron beams having a large aperture angle, and the electron beam diameter increases due to the spherical aberration of the electron lens electrode system of the electron gun, and the brightness decreases.

That is, the emitter cathode of the FEG / TFEG has a drawback that it is difficult to obtain a large angular current density (collecting the electron beam to the aperture efficiently / in other words, collecting the electron beam to the aperture with a small aberration). Was.

For this reason, an electron gun as shown in the cross-sectional view of FIG. 9A has been proposed. That is, the electron gun 40 has an emitter 43 made of, for example, zirconium oxide / tungsten (ZrO / W) arranged along the beam axis 42, and a suppressor 44, an extractor 45,
An electron lens 46 and an anode 47 are sequentially arranged.
A magnetic pole tip of a magnetic pole unit 51 constituted by a permanent magnet 48, an outer magnetic pole 49, and an inner magnetic pole 50 is connected to an extractor 45 and an electron lens 46 via an insulator 52.

Although not shown, these electrodes and the magnetic pole unit 51 are arranged inside the electron gun chamber and are placed in a high vacuum environment. A high voltage is applied to the emitter 43, the suppressor 44, the extractor 45, the electron lens 46, and the anode 47 by lead wires (not shown).

These high voltages are, for example, the suppressors 4
4 has an emitter reference of -500 V and an extractor 45
1 to 5 KV. The anode 47 has a voltage of 1 to 30 KV, and the electron lens 46 has a voltage of 1 to 30 KV. Also,
The voltage of the electron lens 46 is adjusted such that a crossover (focus) is formed on an aperture surface formed of a metal plate having a small hole provided in front of an anode 47 (not shown). These electrodes and the permanent magnet 48 are set to a high vacuum by a vacuum pump such as an ion pump (not shown).

The outer magnetic pole 49 and the inner magnetic pole 50 are made of a material having a high magnetic permeability such as pure iron or soft magnetic iron, and a permanent magnet 48 made of samarium cobalt or the like is disposed inside the outer magnetic pole 49 and the inner magnetic pole 50. It is installed so as to sandwich it. further,
The space portion forms a structure filled with a non-magnetic material such as copper.

FIG. 9B shows a magnetic field distribution B at each electrode position on the Z-axis due to the configuration in which the magnetic poles 49 and 50 are integrated with the extractor 45 and the electron lens 46 as described above. , B are the magnetic fields generated by the permanent magnets, which are curves determined by the inner magnetic pole 50 and the outer magnetic pole 49.

In the electron gun section, electrons emitted from the emitter 43 are converged on a blanking aperture (not shown) for use.
And the voltage applied to the electron lens 46.

At this time, the electron lens voltage Vl is a control for accurately converging to the position on the Z axis of the blanking aperture. Conversely, in the electron lens voltage, only the convergence position of the electrons on the Z axis is obtained. However, it is configured to be controllable.

[0017]

However, in the above-described structure, the action of the magnetic field B is such that electrons emitted from the emitter (radially diverging in the vicinity of the emitter, that is, rapidly moving away from the Z axis) The function of trying to quickly return to the Z-axis (the more the electron moves away from the Z-axis, the larger the aberration becomes. The larger the aberration, the more the deviation from the originally desired convergence characteristic) Therefore, in order to obtain an electron beam with small aberration, it is desired to apply a strong magnetic field near the emitter.

In order to apply a strong magnetic field to the vicinity of the emitter, it is assumed that the suppressor and the extractor should be part of the magnetic pole, judging from the configuration of FIG. However, in the past, this was not performed, and the inner and outer magnetic poles were brought closer to the respective electrodes and integrated.

The reason for this is that TFE (Thermal F
field Emitter) is 18 in actual use conditions.
Since it is used at a high temperature of 00K, the suppressor and the extractor can be used at this high temperature and can withstand heat generated by electron collision, specifically, molybdenum Mo and its alloys (tungsten W and titanium T).
This is because it is necessary to use a heat-resistant alloy such as i.

In a component actually supplied to the market as a TFEG, a needle-shaped emitter is formed at the center, and a plunger-like suppressor electrode is formed so as to surround the emitter. That is, at present, the emitter and the suppressor are supplied as an integral part. This is because the emitter is extremely small and difficult to handle, and at the same time, there is a restriction that Mo is used as a suppressor material (Mo is a material that can withstand high temperatures, but is extremely poor in workability). Such a supply form is taken in consideration of a very difficult point.

On the other hand, it is necessary to use a material having a high magnetic permeability such as electromagnetic soft iron or permalloy as a material used for the magnetic pole, and these metals do not have heat resistance of about 1800 K, and as a result, a sub-lesser or an extractor is required. It could not be turned into a magnetic pole.

The present invention has been made based on these circumstances, and an electron gun using a magnetic material (for example, electromagnetic soft iron) for a suppressor or an extractor, an exposure apparatus having the electron gun mounted thereon, and an exposure method thereof It is intended to provide.

[0023]

According to the first aspect of the present invention, a vacuum vessel, a cathode disposed in the vacuum vessel for generating an electron beam, and a magnetic field applied to the electron beam generated by the cathode are provided. A magnetic pole unit, an anode for accelerating an electron beam generated at the cathode in a beam axis direction to form an electron beam path, and an electron beam disposed between the anode and the cathode and accelerated by the anode. An electron lens that generates an electric field that causes the electric field to converge on the beam axis, wherein at least one of the electrodes is formed of a high magnetic permeability material having a magnetic permeability of 10 or more. It is a gun.

According to the second aspect of the present invention,
The electron gun is characterized in that the suppressor and the extractor among the electrodes are formed of a high magnetic permeability material having a magnetic permeability of 10 or more.

According to the third aspect of the present invention,
The suppressor and the extractor are electron guns using quartz glass as an insulating material.

According to the means of the invention of claim 4,
An electron gun, wherein a cooling device is provided inside an electrode of a high magnetic permeability material among the electrodes.

According to the invention of claim 5,
The cooling device is a circumferential cooling pipe, and is an electron gun.

According to the means of the invention of claim 6,
An exposure apparatus equipped with any one of the above-described electron guns.

According to the means of the invention of claim 7,
The electron beam is generated by the cathode arranged in the vacuum vessel,
In an exposure method for exposing an object to be processed with an electron beam generated by an electron gun, a magnetic field is applied to the electron beam generated by the cathode from a magnetic pole unit to adjust an electric field converged on a beam axis by an electron lens. The gun is an exposure method characterized in that at least one of the electrodes uses a material formed of a high magnetic permeability material having a magnetic permeability of 10 or more.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross sectional view of the electron gun of the present invention.
FIG. 3 is a schematic perspective view of an extractor unit.

In the electron gun, an emitter 1, a suppressor 2, an extractor 3, an electron lens 4, an anode 5, and a blanking aperture 8 are arranged along a Z axis which is a beam axis.

Further, a magnetic pole unit (magnet assembly) 7 is arranged behind the extractor electrode. The magnetic pole unit 7 includes a permanent magnet 7a, an outer magnetic pole 7b, and an inner magnetic pole 7c.
Is integrally formed with the outer magnetic pole 7b via an insulator 9a, and the suppressor 2 is integrally formed with the inner magnetic pole 7c via an insulator 9b.

Of these configurations, the suppressors 2 and extractors 3, which are electrodes, and the outer and inner magnetic poles 7b and 7c are made of a material having high magnetic permeability such as electromagnetic soft iron.

These high-permeability materials have a magnetic permeability (at 0 ° C.) of 10 or more, and it is possible to use pure iron, silicon steel, permalloy, etc. in addition to electromagnetic soft iron.

Although not shown, the electrodes 2, 3 and the magnetic pole unit 7 are arranged inside the electron gun chamber and are placed in a high vacuum environment. A high voltage is applied to the emitter 1, the suppressor 2, the extractor 3, the electron lens 4, and the anode 5 by lead wires (not shown).

For example, the high voltage is supplied to the suppressor 2 by -500 V with respect to the emitter 1 and the extractor 3
1 to 5 KV. The anode 5 has a voltage of 1 to 30 KV, and the electron lens 4 has a voltage of 1 to 30 KV. The voltage of the electron lens 4 is adjusted such that a crossover (focal point) is formed on an aperture surface formed of a metal plate or the like provided with a small hole in front of the anode 5 (not shown). . These electrodes and the permanent magnet 7a are set to a high vacuum by a vacuum pump such as an ion pump (not shown).

Further, as shown in FIG. 1, a cooling pipe 10 is provided inside the extractor 3 near the interface of the insulator 9a.
a are arranged circumferentially. Similarly, a circumferential cooling pipe 10b is arranged above the suppressor 2. And these circumferential cooling pipes 10a, 10b
Is configured to be cooled cyclically by a cooling liquid, such as low-temperature water, supplied from the atmosphere side via the pipes 10aa and 10bb.

FIG. 2 shows a cooling structure of the extractor 3 in which a pipe 10aa connected to a cooling pipe 10a is shown.
Is composed of a cooling water supply side pipe and a drain side pipe, so that the cooling liquid circulates. These also apply to the cooling configuration of the suppressor 2.

The insulators 9a and 9b are made of alumina ceramic mix or the like. Instead, a material having a low thermal conductivity such as quartz glass and a large electric resistance is used.

Next, the operation of the electron gun and the flow of the magnetic flux as an effect of these configurations will be described with reference to FIGS. 3A, 3B and 4A, 4A and 4A in comparison with the case of the conventional electron gun. b)
This will be described with reference to FIG.

FIG. 3A is an explanatory diagram of the flow of magnetic flux in the configuration of a conventional electron gun. FIG. 4A is an explanatory diagram of the flow of magnetic flux in the configuration of the electron gun of the present invention shown in FIG.

The flow of magnetic flux in the case of the conventional electron gun shown in FIG. 3 (a) is indicated by arrows, the magnetic flux that first exits the permanent magnet 17a passes through the inner magnetic pole 17c, and the magnetic pole tip. From the magnetic flux B1 → B2 → B3, the outer magnetic pole 17b
Enter the tip of. Further, the light passes through the inside of the outer magnetic pole 17b and returns to the permanent magnet 17a. At this time, the magnetic flux B1 → B2 →
Since the path of B3 has a relatively long spatial distance, the magnetic flux density B on the Z axis applied to the emitter 18 has a relatively gentle curve as shown in FIG.

On the other hand, in the embodiment of the present invention shown in FIG. 4A, the magnetic flux flowing out of the permanent magnet 7a passes through the inner magnetic pole 7c having a high magnetic permeability, as indicated by arrows. I do. However, unlike conventional electron guns, suppressor 2
Is also a high magnetic permeability material, the magnetic flux B4 is
Flows along. The magnetic flux B5 emitted from the suppressor 2 into the vacuum enters the tip of the extractor 3 also having high magnetic permeability, and becomes the magnetic flux B6 to enter the tip of the outer magnetic pole 7b. Further, the light passes through the inside of the outer magnetic pole 7b and returns to the permanent magnet 7a.

At this time, the path of the magnetic fluxes B4 → B5 → B6 flows along the structure of each electrode unlike the conventional electron gun. In particular, the magnetic flux density B on the Z axis applied to the emitter 1 has a steep curve as shown in FIG.

That is, the curve of the magnetic flux density is shown in FIG.
In the case of (1), a relatively gently curved line having a peak at the emitter 1 is obtained. However, in the case of FIG. 4B, the curve has a peak at the position of the emitter 1 and is very steep.

The reason for this is that the flow of the magnetic flux flies in a narrow gap between the suppressor 2 having a high magnetic permeability and the extractor 3 in FIG. 4 (a), and this position occurs very close to the Z axis. Because it is.

As a result, the magnetic flux density B on the Z axis becomes
It can be said that a steep curve having a high peak is obtained, and the peak position can be located near the emitter 1. As described above, since a steep magnetic field having a high peak can be applied to the vicinity of the emitter 1, the emitted electrons that are going to diverge radially near the emitter 1 are quickly returned to the Z-axis, and the deterioration of aberration is largely prevented. Will be able to

In the above embodiment, the suppressor 2 and the extractor 3 are connected via the insulators 9a and 9b.
Although the inner and outer magnetic poles 7c and 7b are fastened, the suppressor 2 and the inner magnetic pole 7c may be integrally formed as shown in FIG. 5, and in this case, the suppressor 2 is connected to the inner magnetic pole 7c.
And the same voltage is applied.

Further, as shown in FIG.
And the external magnetic pole 7c may be integrated. In this case, the same voltage as that of the extractor 3 is applied to the external magnetic pole 7b.

Further, as shown in FIG. 7, if the adjusting coil 11 is added to the permanent magnet 7a, the magnetic field of the above-described type of permanent magnet can be finely adjusted by the adjusting coil 11.

In the above-described embodiment, the circumferential cooling pipes 10a and 10b are embedded in the electrodes (suppressor 2 and extractor 3).
The place where 0b is embedded is not limited to the electrodes (suppressor 2, extractor 3), but may be made of insulators 9a and 9b. The same applies to the inner and outer magnetic poles 7b and 7c as long as they satisfy the cooling action of the electrodes (suppressor 2 and extractor 3).

Further, the shape of the cooling pipes 10a and 10b is not limited to the circumferential shape, and various shapes are possible. They may have not only a structure in which a pipe is incorporated, but also a structure in which a groove is engraved at a predetermined location such as an electrode (suppressor 2, extractor 3) or the like.

Also, instead of a type in which a cooling liquid flows inside, a highly efficient heat transporter such as a heat pipe is incorporated.
A structure in which heat exchange is performed in a place that is not near the electrodes may be used.

In the above embodiment, the material of the suppressor 2 and the extractor 3 is made of electromagnetic soft iron. However, the range in which the electromagnetic soft iron is used is limited to each of the suppressor 2, the extractor 3, the electron lens 4, and the anode 5. Adapting to any one or more of the electrodes also provides a corresponding effect.

As described above, since the magnetic field on the Z-axis can be made high and steep by using the electromagnetic soft iron for the magnetic pole, electrons which are going to diverge radially are quickly returned to the Z-axis. I can do it. As a result, the deterioration of aberration was largely prevented, and a large current density was obtained.

Further, by equipping the suppressor 2 and the extractor 3 with a cooling pipe, a magnetic material such as electromagnetic soft iron can be used for these electrodes. Furthermore, in addition to the effect of the current, materials such as molybdenum having poor workability can be avoided, so that an inexpensive electrode can be formed.

Further, not only alumina ceramics but also materials such as quartz glass can be used for the insulator inserted between the magnetic pole and the electrode.

The above-described exposure technique using the electron beam emitted from the electron gun can be used for direct drawing, reduced projection, step-and-repeat, one-time batch projection, and the like. An example used in an electron beam writing apparatus will be described below.

FIG. 8 is a structural view showing the structure of an electron optical system on which the electron gun 20 is mounted. Inside the housing, from above, an electron gun 20, a first forming aperture 21, a forming deflector 22,
A second shaping aperture 23, a swing-back deflector 24, a blanking electrode 25, a magnification correcting lens 26, a deflector and a focusing lens 27, and a processing chamber 2B are provided in this order.

A moving stage (not shown) for moving the sample is provided inside the processing chamber 28. This stage is a laser interferometer (not shown) that accurately measures the XY coordinates. The positioning is performed with an accuracy of several nm from. The positioning is performed by detecting a mark provided on the moving table or the sample.

[0062] Here, in order to take out the current long stable in the electron gun 20, it is necessary to reduce the influence of the gas generated from the wafer as a sample, the differential pumping, the electron gun chamber 5 × 10 ^- It is configured to maintain a high vacuum of ⁹ Torr or more.

The control system transfers data from a computer (not shown) to the drawing control system via an interface. The drawing control system selects an aperture figure corresponding to the pattern to be drawn on the wafer from the second forming aperture 23,
The required voltage from which this can be selected is input to the shaping deflector 22, and the beam is returned on-axis by the swing-back deflector 24. The selected drawing pattern is imaged on the sample (wafer) surface using the magnification correction lens 26 and the focusing lens 27.

At this time, an image is formed after the focus of the focusing lens 27 is accurately adjusted based on the accurate distance measured in advance from the focusing lens 27 to the sample. The deflector formed in the focusing lens 27 also forms an image of the drawing pattern on a portion other than the axis. The minimum size of a pattern that can be drawn is limited by aberrations and blurs of the electron optical system, and is approximately 0.1%.
Dimensions below μm are possible.

At this time, a single drawing pattern on the sample is exposed at, for example, L μm × L μm (3 μm × 3 μm), and N · N ′ solid components (eg, 10 × 12) are deflected by the deflector in the focusing lens. It deflects and performs exposure. As a result, N ·
The exposure of the area of L μm × N ′ · L μm (30 μm × 36 μm) is completed. Next, the sample is moved on the moving stage,
The on-axis exposure and the deflection exposure are repeated until the entire sample (for example, 1
The operation is performed to complete the exposure of the entire 2-inch wafer).

As described above, by mounting the electron gun of the present invention on an electron beam lithography apparatus, the electron gun can be reduced in size and inexpensive, so that an exposure apparatus such as an electron beam lithography apparatus can be reduced in size. Cost reduction has become possible.

[0067]

According to the present invention, a magnetic material such as electromagnetic soft iron can be used for the suppressor electrode and / or the extractor electrode (both or one) in the electron gun, and the suppressor electrode and the extractor electrode (both) can be used. Alternatively, as the material, not only heat-resistant alloys such as molybdenum, tungsten, titanium and their alloys, but also ordinary conductive materials can be used, so that an electrode with good workability and low cost can be obtained. Was.

Further, by using glass or the like as an electrical insulator, heat conduction is reduced and cooling efficiency is improved.
The desired cooling can be realized even with a thin cooling pipe.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electron gun according to the present invention.

FIG. 2 is a schematic perspective view of an extractor section of the electron gun of the present invention.

FIG. 3A is an explanatory diagram of a magnetic flux flow in a configuration of a conventional electron gun, and FIG. 3B is an explanatory diagram illustrating a magnetic flux density on a Z-axis applied to an emitter.

FIG. 4A is an explanatory diagram of a flow of a magnetic flux in the configuration of the electron gun according to the embodiment of the present invention, and FIG. 4B is an explanatory diagram showing a magnetic flux density on a Z axis applied to an emitter.

FIG. 5 is a modified example of the embodiment of the present invention.

FIG. 6 is a modified example of the embodiment of the present invention.

FIG. 7 is a modified example of the embodiment of the present invention.

FIG. 8 is a configuration diagram showing a structure of an electron optical system of an electron beam writing apparatus equipped with the electron gun of the present invention.

9A is a cross-sectional view of a conventional electron gun, and FIG. 9B is an explanatory diagram showing a magnetic field distribution thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Emitter, 2 ... Suppressor, 3 ... Extractor, 4 ... Electron lens, 5 ... Anode, 6 ... Magnetic unit, 7a ... Permanent magnet, 7b ... Outer magnetic pole, 7c ... Inner magnetic pole, 9a ... Insulator, 9b ... Insulation Object, 10a ... cooling pipe, 10b ... cooling pipe, 10aa ... piping, 10bb ...
Piping, 20 ... electron gun

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Hashimoto 33, Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Production Technology Research Institute (72) Inventor Atsushi Ando 8-8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa (72) Inventor Yuichiro Yamazaki 8th Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 2H097 AA03 BB01 CA01 CA16 EA01 LA10 5C030 BB05 BB06 BB12 BB17 CC01 CC03 5F056 CB02 CD05 EA02

Claims (7)

[Claims] 1. A vacuum vessel, a cathode disposed in the vacuum vessel for generating an electron beam, a magnetic pole unit for applying a magnetic field to the electron beam generated by the cathode, and a beam axis for generating an electron beam by the cathode. An anode that accelerates in the direction to form an electron beam path, and an electron lens that is disposed between the anode and the cathode and generates an electric field that causes the electron beam accelerated by the anode to converge on the beam axis. The electron gun according to claim 1, wherein at least one of the electrodes is formed of a high magnetic permeability material having a magnetic permeability of 10 or more. 2. The electron gun according to claim 1, wherein the suppressor and the extractor among the electrodes are formed of a high magnetic permeability material having a magnetic permeability of 10 or more. 3. The suppressor and the extractor according to claim 1,
3. The electron gun according to claim 2, wherein quartz glass is used as the insulating material. 4. The electron gun according to claim 1, wherein a cooling device is provided inside the electrode made of a material having a high magnetic permeability among the electrodes. 5. The electron gun according to claim 4, wherein said cooling device is a circumferential cooling pipe. 6. An exposure apparatus comprising the electron gun according to claim 1. 7. An electron beam is generated by a cathode disposed in a vacuum vessel, and a magnetic field is applied to the electron beam generated by the cathode from a magnetic pole unit to adjust an electric field by which an electron lens is converged on a beam axis. In an exposure method for exposing an object to be processed with an electron beam generated by an electron gun, at least one of the electrodes of the electron gun uses a material having a high magnetic permeability of 10 or more. Exposure method.