JPH0550267A - Electron beam working device - Google Patents

Abstract

PURPOSE:To form a beam that is made incident perpendicularly on a sample having a large area and a uniform current density. CONSTITUTION:A beam is emitted from plural wire-shaped cathodes 1 parallely arranged. The beam current is adjusted by a bias voltage impressed to a Wehnelt electrode 2. A large current is drawn out by impressing a positive high voltage on a drawing electrode 3, and by an anode 4 it is reduced to a low acceleration. The plural number of beams are composed before the arrival of the sample 8, and the uniform beam having large current, and large area is formed. By providing a magnetic coil on the outer periphery of the sample of this device or arranging a magnet directly below the sample, the divergence of the beam is also prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam processing apparatus used for etching, film forming, annealing of semiconductor films or welding and processing of mechanical parts.

[0002]

2. Description of the Related Art When a semiconductor film is etched, formed, annealed, or mechanical parts are welded or processed by using an electron beam apparatus, it is necessary to irradiate an area of a sample to be processed with an electron beam as uniformly as possible. desirable. Therefore, conventionally, a spot beam with a current density of Gaussian distribution was reciprocally scanned at high speed, or a linear cathode was directly used to form a linear beam with a uniform current density distribution, and this linear beam was scanned. , A sample has been processed (edited by Seikagakukai Energy Beam Subcommittee: Energy Beam Processing (Realize Co., 1985) p. 268).

[0003]

However, in general, in the processing which requires anisotropy such as groove processing in etching, it is necessary that the electron beam is perpendicularly incident on the sample. Since the apparatus converges or scans the beam, the beam incidence is not always vertical and high anisotropic processing cannot be performed. Further, since the beam acceleration is also in the keV order, there is a problem that the sample is damaged by the beam irradiation.

An object of the present invention is to solve such problems and to provide an electron beam processing apparatus capable of irradiating an electron beam uniformly over a wide area and perpendicularly to a sample.

[0005]

According to the present invention, there is provided an electron beam processing apparatus having a cathode, a Wehnelt electrode, an extraction electrode, an anode, a beam focusing system, a deflection system, a sample stage, and a drive system thereof as basic components. , An electron beam processing apparatus having a plurality of substantially rectangular holes in parallel in the Wehnelt electrode, each having a linear cathode, or in the above electron beam processing apparatus, coaxial with the beam axis An electron beam processing apparatus characterized by having a magnetic coil on the outer circumference of the sample, or an electron characterized by having a magnet having a magnetic pole area equal to or larger than the sample area directly below the sample in the electron beam processing apparatus. A beam processing device is obtained.

[0006]

In general, in a cathode that emits electrons by heating a high melting point metal cathode, an electron beam is extracted in proportion to the 3/2 power of the voltage applied to the cathode surface if the temperature of the cathode is uniform. In addition, the extracted beams expand due to repulsion caused by mutual charges and become a Gaussian distribution.

To irradiate a large-area beam, it is general to make the cathode a large area and to make the beam generation source a large area, or to draw the beam of a large current from the cathode and then spread the beam. In the case of a large-area cathode, the voltage applied to the front surface of the cathode becomes strong at the center due to the influence of the Wehnelt electrode, and the reason for spreading the large-current beam is the repulsion of electrons, and both of them have a Gaussian distribution for the above reason.

Therefore, according to the electron beam processing apparatus of the first aspect of the present invention, as shown in FIG. 1, the Wehnelt electrode has a substantially rectangular hole in parallel therewith, and a linear cathode is provided therein. . As shown in FIG. 1 (b), the electron beam emitted from the linear cathode has a uniform Gaussian distribution in the short-side direction, but a uniform current density in the long-side direction. Therefore, when the linear cathodes are arranged in parallel at an appropriate interval and the beam is emitted, the beam is not affected by the adjacent beams in the direction of the long side of the beam, and it is irradiated because the cathodes have the same shape and the same conditions. The beam will be uniform. On the other hand, the short-side direction is the sum of the adjacent beams, and a proper beam current density can be obtained by appropriately setting the interval between the beams. In this way, a beam having a uniform beam current density and a large area is formed by combining a plurality of beams.

Further, since the electron beam processing apparatus according to the present invention is provided with the extraction electrode and the anode, by applying a negative potential to the cathode, a positive potential to the extraction electrode, and a ground potential to the anode, the beam optical is processed. The system is an acceleration-deceleration system, and a large current can be drawn at a high voltage and then decelerated to a low acceleration, whereby the sample damage due to beam irradiation can be suppressed to a low level.

According to the electron beam processing apparatus of the second aspect of the present invention, the structure is such that the outer periphery of the sample irradiated with the electron beam extracted as described above has a magnetic coil. Since the electron has a small mass and a large electric charge, the direction of motion is easily changed by the electromagnetic field. When an electron moves in a magnetic field, it performs a cyclotron motion that wraps around the magnetic field line. When the electron beam is emitted, even if it is a parallel beam, the electrons repel each other due to the charges of the electrons, and a certain spread angle is obtained. Therefore, when a magnetic field having a line of magnetic force perpendicular to the sample is formed, the electrons make a motion that wraps around the magnetic field, and as a whole, the spread of the electrons can be suppressed. A magnetic coil on the same axis as the beam is used to create this perpendicular magnetic field. The magnetic lines of force of the magnetic coil can be regarded as parallel to the axis when the coil is sufficiently long or near the center of the coil, and the spread of the electron beam incident on the sample can be suppressed by placing the sample in this region. Generally, the radius of cyclotron motion is expressed by the following equation.

A = mv / | q | B where a is the radius of circular motion, m is the mass of the electron, q is the charge of the electron, B is the magnetic field strength, and v is the velocity perpendicular to the magnetic field of the electron.

From the equation, it can be seen that in order to reduce the radius, the electrons should be accelerated to a low degree and the magnetic force should be increased.

A third aspect of the present invention is also a method of forming a magnetic field having the same effect as the second aspect. Here, a magnetic pole (N-pole or S-pole) having a size equal to or larger than the sample area is placed immediately below the sample. A magnetic field line is a system closed by itself, and N
The magnetic force emitted from the pole enters the S pole. At this time, since the light enters perpendicularly to the surface of the pole, by placing a magnetic pole having a plane parallel to the sample just below the sample, a magnetic force line perpendicular to the surface of the sample is formed, which is incident on the sample. The spread of the electron beam can be suppressed.

[0014]

The present invention will be described below with reference to the drawings. FIG. 1A is a diagram showing the configuration of an electron beam processing apparatus according to the first embodiment of the present invention. An electron beam is emitted from a plurality of linear cathodes 1 mounted in parallel due to the potential difference between the linear cathodes 1 and the extraction electrode 3. The beam current is adjusted by the bias voltage applied to the Wehnelt electrode 2. The electron beam that has passed through the extraction electrode 3 is decelerated by the anode 4 having the ground potential. The current density of the extracted beam is uniform in the long-side direction and the short-side direction as shown in FIG. The beam is focused on the sample 8 by the beam focusing system 6 and scanned by the beam deflecting system 7. The sample is fixed to the sample holder 9, and the sample holder 9 can be moved in a plane by the sample holder drive system 10. The electron beam can also be made to diverge without using a focusing system to form a larger area beam, and experiments have shown that
The accelerating voltage of V has a spread angle of 1/20 or less.

FIG. 2 is a view showing the arrangement of linear cathodes according to the present invention together with Wehnelt electrodes. Since the linear cathodes are arranged in parallel and surrounded by the Wehnelt electrodes, the voltages applied to the cathodes are the same and the same beam is emitted.

FIG. 3 is a view showing the arrangement of an electron beam processing apparatus according to the second embodiment of the present invention. A magnetic coil 11 is provided on the outer peripheral portion of the sample in the configuration diagram shown in FIG. Due to the magnetic field formed by the magnetic coil, an electron beam having a certain divergence angle is vertically incident on the sample.

FIG. 4 is a view showing the arrangement of an electron beam processing apparatus according to the third embodiment of the present invention. The magnet 12 is provided immediately below the sample in the configuration diagram shown in FIG. As in FIG. 3, an electron beam having a certain divergence angle is vertically incident on the sample by the magnetic field.

[0018]

As described above, according to the electron beam processing apparatus of the present invention, it is possible to vertically irradiate a sample with an electron beam of a large area with a uniform current density. Can be processed.

[Brief description of drawings]

1A and 1B are views showing a first embodiment of the present invention, wherein FIG. 1A is a configuration diagram of an electron beam processing apparatus, and FIG. 1B is a first embodiment of the present invention.
FIG. 3 is a schematic view of a long-side direction and a short-side direction profile of an electron beam emitted by the electron beam processing apparatus of the embodiment of FIG.

FIG. 2 is a view showing how to arrange linear cathodes according to the present invention together with Wehnelt electrodes.

FIG. 3 is a configuration diagram of an electron beam processing apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an electron beam processing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 1 linear cathode 2 Wehnelt electrode 3 extraction electrode 4 anode 5 electron beam 6 beam focusing system 7 beam deflection system 8 sample 9 sample holder 10 sample holder drive system 11 magnetic coil 12 magnet

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Claims (3)

[Claims] 1. An electron beam processing apparatus comprising a cathode, a Wehnelt electrode, an extraction electrode, an anode, a beam focusing system, a beam deflecting system, a sample stage and its driving system as a substrate structure. An electron beam processing apparatus having holes in parallel, each having a linear cathode. 2. The electron beam processing apparatus according to claim 1, wherein a magnetic coil is provided on the outer circumference of the sample coaxially with the beam axis. 3. The electron beam processing apparatus according to claim 1, further comprising a magnet having a magnetic pole area equal to or larger than the sample area immediately below the sample.