JPH05160005A - Electron beam reduced transfer device - Google Patents

Abstract

PURPOSE:To transfer the reduced image of a mask pattern of a wide visual field on a target in a highly precise manner. CONSTITUTION:In an electron beam reduced transfer device in which the electron beam, emitted from the cathode 8 of an electron gun, is made to irradiate on an electron beam transmission mask 7 through the intermediary of condensing lens systems 10, 11 and 13, and the electron beam which passed through the mask 7 is introduced on a target 19 through reduced image formation lens systems 16 and 18, and the tip part of the cathode 8 of the electron gun is widely formed so that a circle of 2mm in diameter can be contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam reduction transfer apparatus having a large field of view.

[0002]

2. Description of the Related Art An electron beam reduction transfer device for controlling an electron beam emitted from an electron beam source in an electron optical lens barrel when a mask pattern of an electronic circuit or the like is reduced and transferred onto a semiconductor substrate. It is used. FIG. 5 shows an example of a conventional electron gun as an electron beam source used in this type of transfer apparatus. In FIG. 5, 1 is lanthanum hexaboride (L).
The cathode is made of aB ₆ ). The tip of the conical tip portion 1a of the cathode 1 is a spherical surface having a radius of curvature R of 250 μm, and the inclination angle θ of the conical surface is about 45 ° to 55 °. The portion of the cathode 1 following the tip 1a is a prism having a width of about 0.6 mm and a thickness (thickness in the direction perpendicular to the paper surface of FIG. 5) of about 0.7 mm.

Electrodes 3A and 3B are attached in the width direction of the prismatic portion of the cathode 1 via carbon plates 2A and 2B, for example, the electrode 3A.
The cathode 1 is heated and an electron beam is emitted by passing a current from the electrode to the electrode 3B side. A Wehnelt 4 as a focusing electrode is arranged near the tip 1a of the cathode 1, and an anode 5 is arranged outside the Wehnelt 4. The electron beam EB is emitted through the opening of the Wehnelt 4 and the opening of the anode 5, and the electron beam EB is focused once near the center of the opening of the anode 5, and the diameter of the electron beam EB is an image of the electron beam source. A crossover 6 of d _g is formed. The emission angle of the electron beam from the crossover 6 is α _g .

In this regard, the diameter d _{g of the} crossover 6 and the emission full angle α are used as parameters representing the characteristics of the electron beam source.
_The emittance defined by the product with _g is used. That is, the following formula is established. Emittance = d _g · α _g Generally, the larger the emittance value, the wider the field of view can be illuminated with a uniform intensity distribution. Further, if the emission angle is increased in the subsequent electron optical system, the diameter of the crossover becomes smaller, and therefore the emittance value cannot be increased depending on the subsequent electron optical system. When the radius of curvature R of the tip 1a of the cathode 1 is 250 μm as in the example of FIG. 5, the electron beam emission angle α _g is 5 mr.
The diameter d _{g of the} crossover 6 is about 16 μm, and the emittance value is only about 80 μm · mrad.

An electron beam emitted from such an electron gun is applied to an electron beam transmission mask having a mask pattern formed thereon through a predetermined blanking deflector. By operating the deflecting device for blanking, irradiation of the electron beam to the electron beam transmission mask can be avoided, for example, during setting of the target. However,
Conventionally, optimization of the configuration of the deflecting device for blanking and the like have not been considered.

As shown in FIG. 6, a conventional electron beam transmission mask 7 is provided with a reticle portion PA on which a pattern such as an electronic circuit is formed and an alignment mark portion on which alignment beam holes AM1 to AM4 are formed. Has been. Generally, at the beginning of the transfer process, alignment beam holes AM1 to AM1
The electron beam transmission mask 7 and the target are positioned using M4, and then the pattern of the reticle portion PA is transferred to the target via the electron beam. Conventionally, a shutter that selectively shields one of the electron beam that passes through the reticle portion and the electron beam that passes through the alignment mark portion has been arranged below the electron beam transmission mask 7. That is, in the past, an electron beam was applied to the entire electron beam transmission mask, and the shutter disposed under the transmission mask,
Either the electron beam transmitted through the reticle portion or the electron beam transmitted through the alignment mark portion is selected.

[0007]

Recently, it is required to obtain a reduced image having a wider field of view. For example, a reduced image of a visual field of 10 mm square is obtained, and the aperture angle at that time is 0.1 mra.
When the value of d is tried, the emittance value is 10 ⁴ μ
An electron gun of m · 0.1 mrad, that is, about 1000 μm · mrad is required. However, in the electron gun of FIG. 5, the emittance value is about 80 μm · mrad. Therefore, when the optimum aperture angle of 0.1 mrad is obtained in the visual field of 10 mm square by using the electron gun of FIG. 5, the intensity distribution in the visual field is deteriorated, and conversely, the uniform intensity distribution is obtained in the visual field. In such a case, there is a disadvantage that the aperture angle becomes small and the blur due to diffraction becomes large.

Further, in the conventional electron beam reduction transfer apparatus, the shutter for selecting either the alignment mark portion or the reticle portion is provided on the target (sample) side below the electron beam transmission mask. Therefore, the electron beam was always incident on the alignment mark portion and the reticle portion. Therefore, the electron beam is continuously incident on the electron beam transmissive mask to heat the mask, and the mask is deformed due to the linear expansion due to the temperature rise, resulting in the distortion of the pattern formed on the mask. was there.

Further, in the conventional electron beam reduction transfer apparatus, the blanking waveform for operating the blanking deflector has a finite rising time. on the other hand,
The position of the deflection center of the blanking deflector is not particularly optimized. Therefore, when the blanking waveform rises and falls, the reduced image may slightly move on the target (sample) when the electron beam is not yet shielded by the blanking aperture plate. For this reason, the electron beam is incident on a portion of the target that should not be exposed, which deteriorates the pattern accuracy on the target.

In view of the above problems, an object of the present invention is to provide an electron beam reduction transfer apparatus capable of transferring a reduced image of a mask pattern having a wider field of view onto a target with high accuracy.

[0011]

A first electron beam reduction transfer apparatus according to the present invention, for example, as shown in FIG. 1, uses an electron beam emitted from a cathode (8) of an electron gun as a condenser lens system (10, 11). , 13) for irradiating the mask (7) through the mask (7) and guiding the electron beam transmitted through the mask (7) onto the target (19) through the reduction imaging lens system (16, 18). At the tip of the cathode (8) of the electron gun, as shown in FIG.
It is formed on a plane (8a) having an area including a circle of m.

The second electron beam reduction transfer apparatus according to the present invention, for example, as shown in FIG. 1, uses an electron beam emitted from an electron beam source (8) as a condenser lens system (10, 11, 1).
The electron beam transmission mask (7) is irradiated with the electron beam through the electron beam transmission mask (3), and the electron beam transmitted through the electron beam transmission mask (7) is guided onto the target (19) through the reduction imaging lens system (16, 18). In the electron beam reduction transfer apparatus, an opening plate (12) having an electron beam blocking area on the electron beam source (8) side of the electron beam transmitting mask (7) and an electron beam blocking area are provided. Arrange the deflectors (14, 15) that shake the electron beam,
The center of the conjugate image of the electron beam transmission mask (7) with respect to the condenser lens system (10, 11, 13) and the deflection center of the deflector (14, 15) coincide with each other.

The third electron beam reduction transfer apparatus according to the present invention, for example, as shown in FIG. 1, uses an electron beam emitted from an electron beam source (8) as a condenser lens system (10, 11, 1).
The electron beam transmitting mask (7) having a reticle portion and a beam hole portion for alignment is irradiated through the electron beam passing through the electron beam transmitting mask (7), and the electron beam transmitted through the electron beam transmitting mask (7) is contracted to form a reduction imaging lens system (16, 18). In the electron beam reduction transfer apparatus for guiding the electron beam through the target (19), one of the reticle portion and the alignment beam hole portion is provided on the electron beam source (8) side with respect to the electron beam transmission mask (7). A shutter (20) for selectively blocking the electron beam to the is provided.

[0014]

According to the first electron beam reduction transfer apparatus of the present invention, as shown in FIG. 2, for example, the area of the surface (8a) of the cathode (8) where the electron beam emission occurs is less than a circle having a diameter of 1000 μm. growing. Therefore, the electron beam emission angle α _h is 1
In the range of 00 mrad, a strength distribution was obtained in which the difference in strength between the central portion and the peripheral portion was within 2.5%. The diameter d _h of the crossover (9) at this time was 20 μm. Therefore, the emittance of the electron beam source is 2000 μm · mra.
d or more, and the beam aperture angle of the electron beam is 0.1 mrad
However, the variation is 2.5% in the 40 mm square field of view.
A reduced image of the intensity distribution within can be obtained. The beam aperture angle of 0.1 mrad is a condition under which the blur due to diffraction and the blur due to the mechanical optical aberration are equal, and is the optimum condition as the aperture angle.

In the second electron beam reduction transfer apparatus of the present invention, the deflectors (14, 15) for blanking the electron beam.
And the aperture plate (12) are closer to the electron beam source (8) than the electron beam transmission mask (7). Therefore, when the deflector (14, 15) swings the electron beam in a predetermined direction to blank the electron beam, the electron beam does not enter the electron beam transmission mask (7), so that the electron beam is transmitted unnecessarily. The mask (7) is not overheated, the temperature rise is small, and the distortion of the mask pattern due to linear expansion is small.

In the present invention, the deflector (14, 15) is used to deflect the electron beam during blanking, and the deflection sensitivity of the deflector (14, 15) is adjusted so that the deflection center is the electron beam. It is adjusted so that it becomes the center of the conjugate image of the condenser lens system of the transmission mask (7). Therefore, for example, as shown in FIG. 4, even when the electron beam travels along the locus (22) passing through the peripheral portion of the opening (13a) of the aperture plate (13) during the blanking transition, the electron beam transmission mask ( 7)
Illuminate the same point above. Therefore, the reduced beam image on the target (19) does not move and the pattern accuracy does not deteriorate.

Further, in the third electron beam reduction transfer apparatus of the present invention, the shutter (20) for selecting either the reticle portion or the alignment beam hole portion of the electron beam transmission mask (7) is the mask (7). ) From the electron beam source (8) side. Therefore, the electron beam transparent mask (7) is less overheated and the mask pattern and the like are not distorted.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electron beam reduction transfer apparatus according to the present invention will be described below with reference to FIGS. 1 to 4, those parts corresponding to those in FIGS. 5 and 6 are designated by the same reference numerals, and a detailed description thereof will be omitted. FIG. 1 shows the main part of the electron optical lens barrel of the electron beam reduction transfer apparatus of this embodiment. In FIG. 1, the cathode 8, the Wehnelt 4 and the anode 5 constitute an electron gun. As shown in FIG. 2, the cathode 8 is obtained by processing the tip (8a) of a lanthanum hexaboride (LaB ₆ ) cylinder having a diameter φ of 2 mm into a flat surface. The diameter of the opening of the Wehnelt 4 through which the electron beam passes is 2 mm. The supporting portion 8b following the cylindrical portion of the cathode 8 is formed by cutting a pair of cylindrical portions facing each other into a plate shape, and both sides of the supporting portion 8b are provided with electrodes 3A via carbon plates 2A and 2B, respectively. And 3B
Attach. The shape of the tip (8a) of the cathode 8 may be a rectangle other than a circle, a polygon, or the like, and the width may be a width including a circle having a diameter of 2 mm.

In FIG. 2, a crossover 9 having a diameter d _h , which is an image of an electron beam source, is formed in the vicinity of the central portion of the opening of the anode 5 arranged outside the Wehnelt 4. The diameter d _h was 20 μm, and the electron beam emission angle α _h was 100 mrad. The brightness of this electron gun is 5
It was × 10 ⁴ A / (cm ² · sr). The emittance, which is the product of the diameter d _{h of the} crossover 9 and the emission angle α _h in this electron gun, is 2000 μm · mrad,
Subsequent electron optics set the aperture half angle to 0.05 mrad
When the aperture angle was adjusted to 0.1 mrad, the difference in intensity between the central portion and the peripheral portion was 2.5% or less within the visual field of 40 mm in diameter on the electron beam transmission mask. Diameter 40
Since the square inscribed in the circle of mm is about 28 mm square,
According to the electron gun of this example, a visual field of about 28 mm square can be exposed at one time with an aperture angle of 0.1 mrad and a substantially uniform intensity.

Returning to FIG. 1, in order from the anode 5 of the electron gun, a first condenser lens 10, a second condenser lens 11, a blanking aperture plate 12 having an opening 12a, a third condenser lens 13 and an electron beam. A transmission mask (stencil mask) 7 is arranged, and two-stage deflectors 14 and 15 are arranged inside the second condenser lens 11. Then, in order from the electron beam transmission mask 7 to the lower side,
A projection lens 16, an aperture plate 17 having a beam adjusting aperture, an objective lens 18, and a target (sample) 19 are arranged. Further, in this example, the shutter 20 is arranged near the electron beam transmission mask 7 on the electron gun side so as to be movable in the X direction perpendicular to the optical axis of the electron optical lens barrel.

FIG. 3 shows the structure of the shutter 20,
In FIG. 3, the rectangular opening 20a is a window for irradiating the electron beam only on the reticle portion PA of the electron beam transmission mask 7 shown in FIG. The four half-moon shaped openings 20b to 20e formed next to the opening 20a are windows for irradiating the alignment beam holes AM1 to AM4 shown in FIG. 6 with an electron beam. Therefore, by mechanically moving the shutter 20 in the X direction, it is possible to irradiate only the reticle portion PA of the electron beam transmission mask 7 with the electron beam at the time of exposure, and only the alignment mark portion is irradiated with the electron beam at the time of alignment. be able to.

To explain the operation of the embodiment shown in FIG. 1, during normal exposure, the electron beam emitted from the electron gun and forming the crossover 9 has its beam emission angle enlarged by the first condenser lens 10. It is then focused on the opening of the blanking aperture plate 12 by the second condenser lens 11.
As a result, an image of the crossover 9 is formed in the opening of the aperture plate 12. The electron beam emitted from the aperture plate 12 is converted into a parallel beam by the third condenser lens 13 and irradiates the electron beam transmission mask 7. The electron beam transmitted through an arbitrary point of the mask 7 is converted into a substantially parallel beam by the projection lens 16 and directed toward the opening of the aperture plate 17, and the electron beam passing through the aperture of the aperture plate 17 is converted into the objective lens. 1
It is focused on the target 19 by 8 and a reduced image of the pattern on the mask 7 is thereby formed on the target 19.

When it is desired to avoid the irradiation of the electron beam on the target 19, the electron beam is deflected to the outside of the opening of the blanking aperture plate 12 by the two-stage deflectors 14 and 15, and the electron beam is deflected by the blanking aperture plate 12. Shut off.
As a result, the incidence of the electron beam on the electron beam transmission mask 7 is suppressed, and thus the irradiation of the electron beam on the target 19 is suppressed. Further, in this case, the two-stage deflectors 14 and 15
The deflection sensitivity was adjusted so that the mask image would not move on the target 19 during the transition of passing a current through these deflectors to blank the electron beam.

Referring to FIG. 4, the two-stage deflector 14 is provided.
The method of adjusting the deflection sensitivity of Nos. 15 and 15 will be described in detail.
In FIG. 4 in which the condenser lens and the like are omitted, 7I
Is a conjugate image of the condenser lens of the electron beam transmission mask 7. At the time of normal exposure, the electron beam passing through a certain point of the conjugate image 7I passes through the center of the opening 12a of the blanking aperture plate 12 along, for example, the locus 21 to reach a corresponding point on the mask 7. Let's irradiate. In this example, the two-stage deflectors 14 and 15 are positioned so that the conjugate image 7I is located between the two-stage deflectors 14 and 15. Then, the deflectors 14 and 15 are made to oscillate the electron beam in the same direction, and the deflection center of the electron beam is made to substantially coincide with the formation surface of the conjugate image 7I.

With this adjustment, the electron beam that normally travels along the locus 21 is, for example, along the locus 22 at the opening 1 of the aperture plate 12 during the transition of the blanking of the electron beam.
Pass the peripheral part of 2a. However, since the electron beam emitted from one point of the conjugate image 7I is focused on the same point on the mask 7 even if it passes through different paths, the electron beam traveling along the trajectory 22 is the same as when traveling along the trajectory 21. The points on the mask 7 are irradiated. Therefore, the mask image does not move on the target 19 during the blanking transition, and the pattern accuracy does not deteriorate. When the deflection angle by the deflectors 14 and 15 becomes large and the electron beam travels along the trajectory 23 and is blocked by the blanking aperture plate 12, the blanking is completed.

In this example, since the reduced image on the target 19 does not move during the blanking transient, a current having a long rise time can be used as the blanking current supplied to the two-stage deflectors 14 and 15. , Easy to control. Further, an electromagnetic deflector having a slow response speed can be used as the blanking deflector, and it is not necessary to provide an electrostatic deflector in the electron optical lens barrel. Therefore,
The structure of the device is simplified and a stable electron beam can be obtained.

The brightness of the electron gun of this example is 5 × 10 ⁴ A
/ (Cm ² · sr), so half aperture angle is 0.05mr
Assuming that the resist on the target 19 is exposed with an exposure amount of ad and 1 μC / cm ² , the required exposure time T is 0.0025 seconds from the following equation. T = (1 × 10 ^-6 ) / {π (0.05 × 10 ^-3 ) ² × 5 × 10 ⁴ } = 0.0025 [seconds]

In this case, assuming that exposure is performed for one second per field of view of the electron beam transmission mask 7, the duty ratio with which the beam hits the mask 7 is 1/400, and the electron beam always hits the mask 7. Compared with the case, the heating amount of the mask 7 is 1/400. Therefore, the thermal deformation of the mask pattern on the mask 7 is reduced, and the accuracy of the pattern transferred onto the target 19 is improved. It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0029]

According to the first electron beam reduction transfer apparatus of the present invention, since the tip end portion of the cathode is formed in a plane having a width including a circle having a diameter of 2 mm, the total emission angle of the electron beam can be reduced. It can be remarkably large, and emittance of the electron gun is 2
It can be about 000 μm · mrad or more. Therefore, when the electron optical system is adjusted so that the half-angle of the aperture becomes 0.05 mrad, there is an advantage that a reduced image can be obtained by irradiating a wide field of view having a diameter of 40 mm with an electron beam having a substantially uniform intensity. .. This means that a wide field of view of approximately 28 mm square can be exposed at one time, and blurring due to diffraction can be suppressed.

Further, according to the second electron beam reduction transfer apparatus of the present invention, since the center of the conjugate image by the condenser lens system of the electron beam transmission mask and the deflection center of the deflector coincide, the electron beam The image of the electron beam transmission mask does not move on the target during the blanking transition. Therefore, there is an advantage that the pattern accuracy of the image transferred onto the target does not deteriorate. Further, there is an advantage that a blanking signal having a slow rising time can be used and blanking can be performed by an electromagnetic deflector having a slow response speed.

Further, according to the third electron beam reduction transfer apparatus of the present invention, since the shutter is provided on the electron beam source side with respect to the electron beam transmission mask, the irradiation amount of the electron beam with respect to the electron beam transmission mask. Is less. Therefore, there is an advantage that the thermal deformation of the mask pattern is reduced and the pattern accuracy of the pattern transferred onto the target is improved.

[Brief description of drawings]

FIG. 1 is an end view of a longitudinal section showing a main part of an electron optical lens barrel of an embodiment of an electron beam reduction transfer apparatus according to the present invention.

FIG. 2 is a configuration diagram showing an electron gun of an embodiment.

FIG. 3 is a partially cutaway plan view showing a configuration of a shutter according to an embodiment.

FIG. 4 is a diagram for explaining a deflection operation of a two-stage deflector according to an embodiment.

FIG. 5 is a configuration diagram showing a conventional electron gun.

FIG. 6 is a plan view showing a configuration of a conventional electron beam transmission mask.

[Explanation of symbols]

 4 Wehnelt 5 Anode 7 Electron Beam Transmission Mask 8 Cathode 9 Crossover 10 First Condenser Lens 11 Second Condenser Lens 12 Blanking Aperture Plate 13 Third Condenser Lens 14, 15 Deflector 16 Imaging Lens 17 Circular Aperture Plate 18 Objective lens 19 Target

Claims (3)

[Claims] 1. An electron beam reduced by irradiating an electron beam emitted from a cathode of an electron gun onto a mask through a condenser lens system and guiding the electron beam transmitted through the mask onto a target through a reduction imaging lens system. In the transfer device, the electron beam reduction transfer device is characterized in that the tip of the cathode of the electron gun is formed to have a width including a circle having a diameter of 2 mm. 2. An electron beam emitted from an electron beam source is irradiated onto an electron beam transmission mask through a condenser lens system, and the electron beam transmitted through the electron beam transmission mask is projected onto a target through a reduction imaging lens system. In the electron beam reduction transfer apparatus leading to, an opening plate having a region for blocking the electron beam on the electron beam source side of the electron beam transmission mask, and a deflector for swinging the electron beam in the region for blocking the electron beam. And a center of a conjugate image of the condenser lens system of the electron beam transmission mask and a deflection center of the deflector are aligned with each other. 3. An electron beam emitted from an electron beam source is irradiated onto an electron beam transmission mask having a reticle portion and a beam hole portion for alignment through a condenser lens system, and the electron beam transmitted through the electron beam transmission mask is irradiated with the electron beam. In an electron beam reduction transfer apparatus for guiding onto a target through a reduction imaging lens system, an electron beam to one of the reticle portion and the alignment beam hole portion on the electron beam source side with respect to the electron beam transmission mask. An electron beam reduction transfer device characterized by being provided with a shutter that selectively shuts off.