JPH08315999A - Neutral atomic beam focusing device - Google Patents

Abstract

PURPOSE: To provide a device for focusing a neutral atomic beam by use of a standing wave formed by laser beam in which the bottom spreading of the focused neutral atomic beam is minimized. CONSTITUTION: A standing wave 3 is formed in the direction orthogonal to a neutral atomic beam 4 by a laser beam 1 having a frequency smaller than the resonance frequency of the neutral atomic beam 4 to focus the neutral atomic beam 4 in this orthogonal direction. In such a neutral atomic beam focusing device, an opening plate 6 is arranged in a position just before the position where the neutral atomic beam 4 is incident to the standing wave 3, and an opening 7 having a width smaller than the space between the adjacent nodes N, N of the standing wave 3 is formed in the opening plate 6 so that the center is situated in the position of the loop W of the standing wave 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutral atom beam focusing apparatus that enables ultrafine processing.

[0002]

2. Description of the Related Art Neutral atoms, unlike ions and electrons, do not have an electric charge, and are therefore less susceptible to the action of electromagnetic force, and the neutral atom beam cannot be focused using electromagnetic force. Therefore, conventionally, as a method of focusing a neutral atomic beam, a technique has been developed in which a standing wave is formed by a laser beam, the atomic beam is passed through the standing wave, and the force is applied by the laser beam. ing. As an example, Science, Vol.262, pp.877-880
There is. As shown in FIG. 4, the laser light 1 is reflected by the mirror 2
Then, the laser beam 1 is reflected in a direction opposite to the traveling direction to form a standing wave 3, and an atomic beam 4 is passed perpendicularly to the standing wave 3 to be focused on the substrate 5. A fine pattern having a width of 65 nm is formed by this method.

[0003]

However, in the above conventional technique, as shown in FIG. 5 showing the orbits 8 of atoms in the standing wave, the atomic beam 4 incident near the antinode W of the standing wave 3 is antinode. Although focused at the position of W, there is a problem that the atomic beam 4 incident near the node N of the standing wave 3 is not focused at the position of the antinode W. As a result, the distribution of atoms on the substrate 5 has a widened skirt as shown in FIG. 6, and a finer pattern cannot be formed. It is an object of the present invention to provide a device for focusing a neutral atomic beam using a standing wave formed by a laser beam, which has a small spread of the skirt as described above.

[0004]

The present invention has been made in order to achieve the above-mentioned object, that is, a laser beam having a frequency lower than the resonance frequency of the neutral atomic beam is used to make it orthogonal to the neutral atomic beam. Form a standing wave in the direction
In a neutral atom beam focusing device for focusing a neutral atom beam in the orthogonal direction, an aperture plate is arranged at a position immediately before the neutral atom beam enters the standing wave, and the standing wave of the standing wave is placed on the aperture plate. The neutral atom beam focusing device is characterized in that an opening having a width shorter than a space between adjacent nodes is formed so that a center thereof is located at an antinode of a standing wave. The present invention also forms a standing wave in a direction orthogonal to the neutral atom beam by laser light having a frequency higher than the resonance frequency of the neutral atom beam, and focuses the neutral atom beam in the orthogonal direction. In the neutral atomic beam focusing device, the aperture plate is arranged at a position immediately before the neutral atomic beam enters the standing wave, and the aperture plate has a width shorter than the interval between adjacent nodes of the standing wave. The neutral atom beam focusing device is characterized in that the opening is formed so that the center is located at the position of the node of the standing wave.

[0005]

[Function] In a focusing device using a laser beam having a frequency lower than the resonance frequency of a neutral atomic beam, the atomic beam incident near the antinode of the standing wave is focused at the antinode position, Atom beams incident near the node of the wave do not focus at the antinode position, and atom beams incident at the node of the standing wave are not focused at all. However, in the present invention, only the atomic beam that is going to enter near the antinode of the standing wave is made incident, and the atomic beam that is going to enter near the node of the standing wave is arranged so as to cut the opening. , Atomic beams can be accurately focused on the antinode of the standing wave. On the other hand, in the focusing device that uses a laser beam with a frequency higher than the resonance frequency of the neutral atomic beam, the atomic beam incident in the vicinity of the node of the standing wave is focused at the position of the node. Atomic beams incident near the antinode of the are not focused at the node position, and atomic beams incident on the antinode of the standing wave are not focused at all. However, in the present invention, only the atomic beam that is about to enter the vicinity of the node of the standing wave is incident, and the atomic beam that is about to enter near the antinode of the standing wave is arranged with an opening so as to be cut. , Atomic beams can be focused with high accuracy at the nodes of standing waves.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the neutral atom beam focusing device according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the structure of a vacuum vapor deposition apparatus adopting a neutral atomic beam focusing apparatus according to the present invention. A slit plate 23 having a slit 23a having a width of 1 mm is arranged below the Na atomic beam source 22, that is, in the y direction in the drawing.
The Na atomic beam 4 emitted by heating 2 to 230 degrees is shaped by the slit 23a. An opening plate 6 having an opening 7 having a diameter of 100 nm is arranged below the slit plate 23, a Si substrate 5 is arranged below the opening plate 6, and the Si substrate 5 is placed on a sample table 26. Has been done.

A beam splitter 10, a beam splitter 15, a quarter-wave plate 24, and a lens 25 are arranged in that order on the right side of the laser beam generator 9, that is, in the z direction in the drawing, and further, the aperture plate 6 is provided. A mirror 2 is arranged on the lower side of the opening 7. The laser light generator 9 is
A linearly polarized laser beam 1 having a frequency slightly lower than the resonance frequency of the Na atom is generated, and the lens 25 has a focal point of the mirror 2.
The mirror 2 is arranged so as to reach the top, and the mirror 2 is mounted on the sample table 26.
It is fixed on. A beam splitter 11 and a mirror 14 are arranged above the beam splitter 10 and the beam splitter 15, respectively, and an acousto-optic modulator 12 and a beam splitter 13 are arranged in this order between the beam splitter 11 and the mirror 14. Has been done. A mirror 16 and a beam splitter 17 are arranged above the beam splitter 11 and the beam splitter 13, respectively. To the right of the mirror 16, that is, in the z direction in the drawing, the acousto-optic modulator 1 is connected to the beam splitter 17 following
8 are arranged, and further the slit 2 of the slit plate 23
A quarter wave plate 20 and a mirror 19 are arranged in that order on the lower side of 3a.

Of the linearly polarized laser light 1 generated by the laser light generator 9 in this way, the beam splitter 1
The laser beam 1a transmitted through 0 is reflected by the beam splitter 1
After passing through 5, the light enters the quarter wave plate 24. The laser beam 1b reflected by the beam splitter 10 and the beam splitter 11, transmitted through the beam splitter 13, and reflected by the mirror 14 and the beam splitter 15 is frequency-modulated by the acousto-optic modulator 12 on the way, It is incident on the quarter-wave plate 24 together with the laser light 1a. These laser beams 1a and 1b are transmitted by the quarter wavelength plate 2
It is converted into circularly polarized light by passing through 4 and the lens 2
The light is focused on the mirror 2 by passing through 5. Further, the laser beams 1a and 1b are reflected by the mirror 2 and are converted into a circular direction which is a reverse rotation of the forward path, and the forward polarized light and the backward polarized light are superposed on each other.
A region of the standing wave 3 is formed in a space between the substrate 5 and the substrate 5.

The standing wave 3 has a plurality of nodes N in the z direction as shown in FIG. 2, and therefore has an antinode W at the center of the adjacent nodes N, N, and the interval between the adjacent nodes N, N. Is equal to half the wavelength of the laser light 1a, 1b. Here, the width in the z direction of the aperture 7 of the aperture plate 6 is formed sufficiently narrower than the interval between the adjacent nodes N of the standing wave 3, that is, the half of the wavelength of the laser light 1a, 1b. Further, the center of the opening 7 in the z direction is arranged so as to coincide with any antinode W of the standing wave 3.

On the other hand, of the linearly polarized laser light 1 generated by the laser light generator 9, the beam splitter 10
The laser light 1c reflected by the laser beam 1c and transmitted through the beam splitter 11 is reflected by the mirror 16 and transmitted through the beam splitter 17 to enter the acousto-optic modulator 18. Also, the laser beam 1d reflected by the beam splitter 11 and reflected by the beam splitter 13 and the beam splitter 17
Is subjected to frequency modulation by the acousto-optic modulation element 12 on the way, and then the acousto-optic modulation element 1 together with the laser beam 1c.
It is incident on 8. These laser lights 1c and 1d are frequency-modulated by the acousto-optic modulator 18 and then 1
It is converted into circularly polarized light by passing through the quarter wave plate 20. Further, the laser beams 1c and 1d are reflected by the mirror 19 and converted into a circular direction which is the reverse rotation of the outward path, and are transmitted through the quarter wavelength plate 20 to be converted into linearly polarized laser light 21 orthogonal to the outward path. To be done. In this way, in the space between the slit plate 23 and the aperture plate 6, a collimated region where the + z direction laser lights 1c and 1d and the −z direction laser light 21 coexist is formed. Of the above members, Na
The atomic beam source 22, the slit plate 23, the aperture plate 6, the mirror 2, the sample stage 26, and the Si substrate 5 are installed in a vacuum container 27.

However, y generated from the Na atomic beam source 22
Although the Na atom beam 4 in the direction is shaped by the slit 23a, it naturally has a velocity component in the ± z direction and a velocity component in the front or back side of the paper surface, that is, in the ± x direction.
Of these, Na atoms having a velocity component in the + z direction feel the frequency of the laser light 21 from the −z direction high and the frequencies of the laser lights 1c and 1d from the + z direction low due to the Doppler effect. In the case of the present embodiment, the frequency of the laser light is set lower than the resonance frequency of the Na atom, so that the frequency is − compared to the laser light 1c and 1d from the + z direction.
The laser light 21 from the z direction is absorbed more. Therefore, the Na atom having the velocity component in the + z direction receives the momentum of the laser light in the −z direction and loses the velocity component in the + z direction. Similarly, a Na atom having a velocity component in the −z direction is + z
It loses the velocity component in the −z direction due to the momentum of the laser light in the direction. In this way, the Na atomic beam 4 is collimated in the z direction in the space between the slit plate 23 and the aperture plate 6.

The collimated Na atomic beam 4 has an opening 7
And then passes through the area of the standing wave 3. In this region, an electric field having nodes N and antinodes W alternately is formed in the z direction,
A dipole is induced in the Na atom by this electric field. In the present embodiment, the frequency of the electric field oscillates at a frequency slightly lower than the resonance frequency of the Na atom, so that the frequency of the dipole vibration tries to follow the frequency of the electric field, and thus the Na atom has the strongest antinode W of the electric field, that is, Z toward the belly W of standing wave 3
The orbit is bent in the direction and deposited on the Si substrate 5.

At this time, the Na atomic beam 4 incident near the antinode W of the standing wave 3 is focused on the position of the antinode W, but the Na atomic beam 4 incident near the node N of the standing wave is not completely generated. The Na atomic beam 4 which is not focused on the antinode W and is incident on the node N of the standing wave
Is not focused at all. However, in the present embodiment, only the Na atomic beam 4 that is about to enter the antinode W of the standing wave is incident, and N about to enter the node N of the standing wave.
Since the opening 7 is arranged so as to cut the a atom beam 4, the Na atom beam 4 can be accurately focused at the position of the antinode W of the standing wave. FIG. 3 shows N deposited on the Si substrate 5.
The result of having calculated the distribution of a atom is shown. As shown in the figure, it was possible to form a fine pattern with no skirt expansion.

The ground state of Na atom is divided into a plurality of fine structure levels. Therefore, if irradiation with light of a single wavelength is continued in the collimating region, an optical pumping effect occurs in the process of repeating absorption and emission of light, and the interaction with irradiation light gradually weakens. Therefore, in this embodiment, the light 1c that does not pass through the acousto-optic modulator 12 and the light 1d that is frequency-modulated by the acousto-optic modulator 12 are irradiated to prevent the optical pumping effect. Similarly, standing wave 3
Also in the region (2), the standing wave 3 is formed by the light 1a that does not pass through the acousto-optic modulator 12 and the light 1b that is frequency-modulated by the acousto-optic modulator 12 to prevent the optical pumping effect. On the other hand, the acousto-optic modulator 18
Is for adjusting the interaction between Na atoms and laser light in the collimating region to be the strongest.

Further, in order to avoid the influence of the diffraction of the Na atomic beam 4 by the opening 7, it is desirable that the distance between the opening plate 6 and the standing wave 3 be as close as possible. Also, the standing wave 3 and S
It is preferable that the i-substrate 5 and the i-substrate 5 are also brought close to each other. Further, although a circular opening is provided as the opening 7 in this embodiment, it may be a slit that is long or short in the x direction. Further, in this embodiment, the frequency of the standing wave 3, that is, the laser beam 1
As the frequency of the laser beam 1, a frequency slightly lower than the resonance frequency of the Na atomic beam was used.
It is also possible to use a frequency slightly higher than the resonance frequency of the a atom beam. However, at this time, the Na atom receives repulsive force,
Therefore, since the Na atomic beam is focused on the node N of the standing wave 3 by passing through the standing wave region, the center of the opening 7 is also located at the node N of the standing wave 3.

[0016]

As described above, according to the present invention, since the neutral atomic beam can be focused on the substrate in the size of nanometer, it is possible to form, for example, a nanometer-sized ultrafine structure. It can be applied as a manufacturing apparatus for electronic devices, optical devices, etc. using mechanical effects.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a vacuum vapor deposition apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of the embodiment.

FIG. 3 is a view showing a fine pattern produced in the example.

FIG. 4 is a schematic diagram showing a conventional technique.

FIG. 5 is a diagram showing a trajectory of a neutral atom beam in a conventional technique.

FIG. 6 is a view showing a fine pattern produced by a conventional technique.

[Explanation of symbols]

1, 1a to 1d, 21 ... Laser light 2, 14, 16, 19 ... Mirror 3 ... Standing wave 4 ... Na atomic beam 5 ... Substrate 6 ... Aperture plate 7 ... Aperture 8 ... Orbit of atom in standing wave 9 ... Laser light generator 10, 11, 13, 15, 17 ... Beam splitter 12, 18 ... Acousto-optic modulator 20, 24
... 1/4 wavelength plate 22 ... Na atomic beam source 23 ... Slit plate 23a ... Slit 25 ... Lens 26 ... Sample stage 27 ... Vacuum container

Claims (2)

[Claims] 1. A standing wave is formed in a direction orthogonal to the neutral atom beam by a laser beam having a frequency lower than the resonance frequency of the neutral atom beam, and the neutral atom beam is formed in the orthogonal direction. In the neutral atom beam focusing device for focusing, the aperture plate is arranged at a position immediately before the neutral atom beam is incident on the standing wave, and in the aperture plate, an interval between adjacent nodes of the standing wave. A neutral atomic beam focusing device, characterized in that an opening having a width shorter than that of the above is formed such that the center thereof is located at the position of the antinode of the standing wave. 2. A laser beam having a frequency higher than the resonance frequency of the neutral atom beam forms a standing wave in a direction orthogonal to the neutral atom beam, and the neutral atom beam is in the orthogonal direction. In the neutral atom beam focusing device for focusing, the aperture plate is arranged at a position immediately before the neutral atom beam is incident on the standing wave, and in the aperture plate, an interval between adjacent nodes of the standing wave. A neutral atomic beam focusing device, wherein an opening having a width shorter than that of the above is formed so that the center thereof is located at the position of the node of the standing wave.