JPS6244936A - Ion beam generating method and device therefor - Google Patents

Abstract

PURPOSE:To form high purity ion beam by irradiating soft X-ray or vacuum ultra-violet beam into an ionization chamber filled with gas to ionize the gas in limited area and taking out the produced ion as an ion beam. CONSTITUTION:Gas is filled through gas lead-in nozzle 10 between the facing electrodes 11, 12 in an ionization chamber 9 then soft X-ray or vacuum ultraviolet beam L is irradiated from electronic synchrotron radiation unit 7 to ionize the gas. When applying predetermined voltage across the facing electrodes 11, 12 and maintaining the take-out electrode 13 at further negative potential than the cathode side electrode 12, positive ions in the produced ions are subjected to the function of electric field and taken out as an ion beam. Since soft X-ray or vacuum ultraviolet beam having high directivity is irradiated into the ionization chamber 9, the plasma forming area 16 is limited to a portion of the space in said chamber 9 to leave yet-excited gas in the space around the excited area 16. Consequently, the take-out ion beam can be prevented from lowering the purity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ion beam generation method and apparatus for exciting gas molecules in an ionization chamber and extracting the generated ions as an ion beam.

[Conventional technology]

Conventional ion beam generators, so-called ion sources, include those in which gas molecules within an ionization chamber are excited by DC glow discharge or high-frequency discharge, or those in which they are excited by an electron beam.

For details on these, see Reference (1) CR, G.

Edited by Vilson and G, R. Brewer,
Ion neams (with application)
ns to j, on jplantation).

John Wiley & 5ons Tnc, 19
73) is introduced. Typical examples are shown in FIGS. 8 and 9.

The example shown in FIG. 8 is a direct current glow discharge type, in which a direct current voltage is applied between the anode electrode 2 and the cathode electrode 3, and the gas introduced into the ionization chamber 1 from above is ionized by glow discharge. The generated ions are extracted as an ion beam by a voltage applied to the extraction electrode 4.

The example shown in FIG. 9 is of a high frequency discharge type, in which a high frequency electric field is applied to the ionization chamber 1 by the coil 5, and the gas introduced from above is ionized by the high frequency discharge. The generated ions are extracted as an ion beam by a voltage applied to the extraction electrode 4. In this example, the magnet 6 is used in combination to improve the ion production efficiency.

[Problem that the invention seeks to solve]

Figures 8 and 9 are typical examples of the prior art, but in these examples, it is difficult to limit the discharge region, that is, the excitation region where the gas is ionized, to a predetermined space. However, impurities were mixed into the gas from the vessel walls and electrodes due to collisions between the generated ions and electrons, reducing the purity of the ion beam. In addition, in these examples, the kinetic energy of ions in the plasma is distributed over a wide range, and the kinetic energy of the ions in the plasma is controlled to have a desired constant value suitable for use as an ion beam. was difficult.

Another example of conventional technology is a method in which the electron beam is used for excitation, but even in this method, it is necessary to apply a voltage to the excitation region without affecting the shape of the electron beam, that is, to increase the kinetic energy of the generated ions. was difficult to control as desired.

Furthermore, in these conventional technologies, the types of ion species generated and their excitation levels, that is, their internal energies, are also distributed over a wide range, so that a specific type of ion species suitable for use as an ion beam or a specific excited level is distributed over a wide range. It was difficult to concentrate and generate ionic species in the state.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new ion beam generation method and apparatus that solve the problems of the prior art described above.

[Means for solving problems]

The ion beam generation method of the present invention irradiates an ionization chamber filled with gas with a soft X-ray or vacuum ultraviolet light beam (preferably a wavelength of 10 to 2000 beams) to ionize the gas in a limited area within the ionization chamber. It is characterized by extracting the generated ions as an ion beam.

Further, the ion beam generator of the present invention includes an ionization chamber;
means for introducing gas into the ionization chamber; and a means for introducing a gas into the ionization chamber;
and a means for forming an electric field for extracting ions generated from an excitation region where gas is ionized by irradiation with the soft X-ray or vacuum ultraviolet light beam as an ion beam. The soft X-ray or vacuum ultraviolet light beam irradiation means is characterized in that it uses an electron synchrotron radiation device as a soft X-ray or vacuum ultraviolet light generation source.

[Effect]

In the ion beam generation method of the present invention, gas molecules are excited only in a limited area within the ionization chamber by irradiation with soft X-rays or vacuum ultraviolet light beams, so plasma is formed without contacting the chamber wall or electrodes. This prevents impurities from entering the ion beam. In addition, since the excitation region is limited, the kinetic energy of the generated ions can be easily controlled, and by using soft X-rays or vacuum ultraviolet light beams of specific wavelengths, specific types of ion species can be Alternatively, it is possible to selectively generate ion species in a specific excited state,
The internal energy of ions can also be easily controlled. This allows the characteristics of the extracted ion beam to be varied as desired.

The ion beam generator of the present invention excites gas molecules in a limited area by irradiating an ionization chamber with a highly directional, high-intensity soft X-ray or vacuum ultraviolet light beam generated from an electron synchrotron radiation device. efficiently,
The generated ions can be extracted as an ion beam by the action of an electric field. Furthermore, if a wavelength selection means is used in conjunction with an electron synchrotron radiation device that is a source of soft X-rays or vacuum ultraviolet light, a soft X-ray or vacuum ultraviolet light beam having the specific wavelength can be easily obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 is a diagram showing one embodiment of the present invention, showing the basic device configuration.

In FIG. 1, numeral 7 schematically shows an electron synchrotron radiation device which is a source of soft X-rays or vacuum ultraviolet light. Regarding the electron synchrotron radiation device, see the literature (
2) (edited by C. Kunz, 5ynchrotron
radiation (Techniques and
d Appli-catj, ons), Spring
er-Verlag, 1979).

-'/- 8 is a beam propagation path consisting of a vacuum pipe, 9 is an ionization chamber, 10 is a gas introduction nozzle, 11.12 is a counter electrode, 13
is an extraction electrode, 14.15 is a DC bias power supply, 16
indicates an excitation region where gas is ionized by soft X-rays or vacuum ultraviolet light beam L incident on the ionization chamber 9.

Next, the operating principle, features, and main effects of the device of the present invention will be described based on FIG.

Figure 2 shows the wavelength distribution of the emitted light from the electron synchronized 1-ron radiator (above figure), and the methane (CH,) for the emitted light.
The absorption cross-section spectrum (lower figure) of silane (Sj, T(4) gas is shown. Many other gas molecules also show absorption spectra roughly similar to this figure, and gas molecules are ionized as a result of this light absorption. In other words, this figure shows that the emitted light from the electron synchrotron radiation device is light that efficiently ionizes gas molecules and has a wavelength distribution with a high absorption rate.

This wavelength component with high absorption rate is distributed in a range of about 10 to 2000.

Moreover, the intensity distribution of the synchrotron radiation of the electron synchrotron radiation device is given by the Schwinger equation in the above-mentioned document (2),
According to this formula, as shown in FIG. 3, it is expressed by the vertical direction of the soft X-ray or vacuum ultraviolet light beam L emitted from the electron synchrotron radiation device, where C is the speed of light.

From this, it can be seen that a soft X-ray or vacuum ultraviolet light beam with good directivity is generated.

Therefore, in FIG. 1, gas is filled between the gas introduction nozzle 10 and the opposing electrodes 11 and 12 of the ionization chamber 9, and the space is irradiated with soft X-rays or vacuum ultraviolet light beam L from the electron synchrotron radiation device 7. For example, the counter electrode 11.
The gas is ionized between the electrodes 11 and 12, and a predetermined voltage (a voltage that does not cause discharge) is applied to the opposing electrodes 11 and 12, for example, so that the electrode 11 becomes the anode and the electrode 12 becomes the cathode, and the extraction electrode 13 is Cathode side electrode 12
It is clear that by keeping the potential more negative than the ion beam, positive ions among the generated ions are affected by the electric field and are extracted to the outside as an ion beam.

Here, since the ionization chamber 9 is irradiated with a soft X-ray or vacuum ultraviolet light beam with good directionality, an excitation region where gas is ionized, that is, plasma is formed by irradiation with the soft X-ray or vacuum ultraviolet light beam. The excitation region 16 is limited to a part of the space within the ionization chamber 9, and unexcited gas still exists in the space around the excitation region 16.

Therefore, it is possible to avoid impurities from being mixed into the gas from the vessel wall or electrodes due to collisions between the generated ions and electrons and reducing the purity of the extracted ion beam.

That is, the apparatus of the embodiment shown in FIG. 1 can be used as an apparatus for implementing the ion beam generation method of the present invention.

FIG. 4 shows another embodiment of the present invention.

In this embodiment, a cylindrical mirror 1 is provided in the middle of a beam propagation path 8 to transmit radiation light from an electron synchrotron radiation device 7.
7 to condense the light into a flat shape parallel to the electrode surfaces of the counter electrodes 11 and 12 and make it enter the ionization chamber 9, which faces the flat soft X-ray or vacuum ultraviolet light beam L inside the ionization chamber. The relative positional relationship with electrodes 11 and 12 is shown in FIG.

As mentioned above, the emitted light from the electron synchrotron radiation device 7 has good directivity, so it can be collected into a flat surface with a thickness of about 1 mm by condensing it with a cylindrical mirror, toroidal mirror, hyperbolic mirror, etc., or focusing it with a slit. You can easily obtain a beam of Using such a flat beam not only meets the purpose of the present invention to limit the excitation region 16 inside the ionization chamber, but also because the entire excitation region is approximately equidistant from the electrode surface. Since the ions generated by the ion beam are uniformly affected by the electric field, by changing the strength of the electric field, it is possible to control the kinetic energy of the ions forming the ion beam with high precision, making it the most suitable for use as an ion beam. A desired amount of kinetic energy can be imparted to all ions.

FIG. 6 shows another embodiment of the present invention, which is equipped with wavelength selection means for irradiating a soft X-ray or vacuum ultraviolet light beam of a specific wavelength component.

In this embodiment, as an example of wavelength selection means, a spectroscope 18 made of a diffraction grating is installed in the middle of the beam propagation path 8, and only a specific wavelength component of the emitted light from the electron synchrotron radiation device 7 is selected by the spectrometer 18. The selected light is focused into a flat shape by the cylindrical mirror 17 and made to enter the ionization chamber 9.

When gas molecules are ionized, the soft X involved in ionization
The type of ions produced (for example, Si
It is known that there is a certain relationship between the excitation level and the excitation levels thereof. Therefore, by selecting the wavelength of the soft X-ray or vacuum ultraviolet light beam irradiated to the ionization chamber 9 using the embodiment apparatus shown in FIG. This enables selective generation.

FIG. 7 also shows another embodiment of the present invention having a similar wavelength selection means, but in this embodiment, a lens (for example, a Fresnel zone plate) 19 By installing a soft X-ray or a vacuum ultraviolet light beam, the soft X-ray or vacuum ultraviolet light beam is focused on a minute spot (diameter of 10 m to 10 o, t, m) and is made to enter the ionization chamber 9. Such an ion beam generator is suitable as an ion source for an ion beam apparatus for forming fine patterns because the excitation region 20 in which ions are generated can be limited to an extremely small area. There are conventional micro ion sources for ion beam devices that use liquid metal.
While there are devices that only generate ions of a few limited types of atoms, this example device can generate ion beams of a wide variety of atoms or molecules by simply changing the type of gas introduced. It has the advantage of being able to

In addition, an undulator is installed in the electron synchrotron radiation device.
When a device for making electron orbits meander (introduced in literature (2)) is installed, the wavelength distribution of the emitted light shown in Fig. 2 changes to a specific wavelength λ. The intensity increases by nearly two orders of magnitude, and by further changing the strength of the magnetic field, the wavelength λ. can vary widely. Therefore, in the embodiment apparatus shown in FIG. 1 or 4, by using an electron synchrotron radiation device equipped with an undulator as a soft A certain high intensity soft X-ray or vacuum ultraviolet light beam can be obtained.

〔Effect of the invention〕

As described above, the ion beam generation method of the present invention excites gas molecules in a limited area within the ionization chamber by irradiation with soft X-rays or vacuum ultraviolet light beams, and extracts the generated ions as an ion beam. It is possible to form a highly pure ion beam that is not contaminated by impurities from the electrodes.

Further, according to the ion beam generator of the present invention, gas molecules in a limited region are excited by using a highly directional, high-intensity soft X-ray or vacuum ultraviolet light beam generated from an electron synchrotron radiation device. In addition, it is possible to efficiently extract the ion beam.

The unique effects of each embodiment other than the above are as described in the Examples section.

The ion beam generation method and device of the present invention are suitable for application to dry etching in LSI processes, ion beam devices for fine pattern formation, and the like.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the basic device configuration of the present invention;
The figure shows the wavelength distribution of electron synchrotron radiation and the spectral distribution of the absorption cross section of gas molecules. Figure 3 shows the radiation angle distribution of electron synchrotron radiation. Figure 4 shows the condensed light. A schematic diagram showing another example of the device configuration of the present invention with additional means; FIG. 5 is a diagram showing the relative positional relationship between the counter electrode and the soft X-ray or vacuum ultraviolet light beam; FIGS. 6 and 7;
The figure is a schematic diagram showing another example of the device configuration of the present invention that uses a condensing means and a wavelength selection means in combination, FIG. 8 is a schematic diagram showing a conventional DC glow discharge type ion beam generator, and FIG. FIG. 1 is a schematic diagram showing a conventional high-frequency discharge type ion beam generator. 7.8.17.18.19... Soft X-ray or vacuum ultraviolet light beam irradiation means (7... Electron synchrotron radiation device, 8... Beam propagation path, 17... Cylindrical mirror for focusing , 18... wavelength selection spectrometer, 19...
9... Ionization chamber 10... Nozzle 11, 12.13.14.15... Electric field forming means (1
1, 12... Counter electrode, 13... Extraction electrode, 1
4.15...DC bias power supply) 16.20...Excitation region L...Soft X-ray or vacuum ultraviolet light beam Patent applicant: Nippon Telegraph and Telephone Corporation Representative Patent Attorney Junnosuke Nakamura Figure 18 Figure 29

Claims (8)

[Claims] (1) Ionization characterized by irradiating an ionization chamber filled with gas with a soft X-ray or vacuum ultraviolet light beam, ionizing the gas in a limited area within the ionization chamber, and extracting the generated ions as an ion beam. Beam generation method. (2) The soft X-ray or vacuum ultraviolet light beam is composed of a specific wavelength component, and the specific wavelength component ionizes the gas into a specific type of ion species. The ion beam generation method described in section. (3) The ion beam generation method according to claim 1 or 2, wherein the soft X-ray or vacuum ultraviolet light beam has a flat shape. (4) Ion beam generation according to any one of claims 1 and 2, characterized in that the soft X-ray or vacuum ultraviolet light beam is focused and irradiated onto a minute spot. Method. (5) an ionization chamber, a means for introducing gas into the ionization chamber, a means for irradiating the ionization chamber with a soft X-ray or vacuum ultraviolet light beam, and a gas is irradiated with the soft X-ray or vacuum ultraviolet light beam; means for forming an electric field for extracting ions generated from the excitation region to be ionized as an ion beam; An ion beam generator characterized by having a configuration used as a light generation source. (6) The soft X-ray or vacuum ultraviolet light beam irradiation means:
6. The ion beam generator according to claim 5, further comprising wavelength selection means for selecting a specific wavelength component from the soft X-ray or vacuum ultraviolet light beam. (7) The soft X-ray or vacuum ultraviolet light beam irradiation means:
7. The ion beam generator according to claim 5, further comprising condensing means for flattening the soft X-ray or vacuum ultraviolet light beam. (8) The soft X-ray or vacuum ultraviolet light beam irradiation means:
The ion beam generator according to any one of claims 5 and 6, characterized by having a condensing means for condensing the soft X-ray or vacuum ultraviolet light beam onto a minute spot. .