JPH0441460B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to semiconductor processing equipment, material modification,
This relates to ion beam generators used for materials synthesis, etc.

[Prior art]

Conventionally, various methods have been considered and put into practical use as ion generation methods using ion beam generators. Most of them used electric discharge, but in recent years ion sources using laser light have been devised. There are two methods of using light such as laser light. One is to irradiate a solid such as a metal with light and use the resulting plasma as an ion source, and the other is to focus the laser light and convert it into gas or liquid. irradiation to create plasma, which is used as an ion source.
The other method uses a variable wavelength light source to resonate a single wavelength of light with the energy level of a substance to be ionized, and the present invention relates to the latter. It uses synchrotron radiation rather than laser light as a light source.

[Summary of the invention]

The present invention uses the autoionization level of a substance to be ionized as the state immediately before ionizing the substance by resonant light excitation in the above-mentioned resonant light excitation and ionization type ion beam generation apparatus. It is an object of the present invention to provide an ion beam generator that can improve the ionization efficiency with respect to input light energy by two orders of magnitude or more compared to the ionization method, and has excellent selectivity in selective ionization.

[Embodiments of the invention]

First, the ionization method in the apparatus of the present invention will be explained by comparing it with a conventional method, taking as an example the case of generating an aluminum ion beam. FIG. 1 is an energy level diagram of aluminum neutral atoms.

Conventional ionization methods, for example, have a wavelength of 3082 Å,
This is a method of irradiating the aluminum vapor to be ionized with two 6200 Å laser beams B1 and B2. In other words, aluminum atoms in the ground state 3p ( ² P ⁰ ) are first brought into the first excited state 3d ( 2 P 0 ) by the 3082 Å laser beam B1. ^2D ), and then ionized by a 6200 Å laser beam B2.

The ionization method in the device of the present invention differs from the conventional ionization method described above in that the final excited state is an auto-ionization state and that synchrotron radiation light, particularly relativistic synchrotron radiation light, is used as the excitation light source. It is in. Synchrotron synchrotron radiation has directionality similar to laser light, and is a photon with much greater intensity and energy than laser light. Therefore, as shown in Figure 1, a single photon can bring aluminum vapor out of the ground state. It can be excited to an autoionization state, and the excited vapor is ionized with a predetermined transition probability by autoionization.

In the case of the ionization method in this inventive device, the photoexcitation cross section from the two-electron excited state 3s3p ² to the autoionization state 3s3p4s by synchrotron radiation light with a wavelength of 3050 Å is σ _i =0.8×10 ⁻¹⁵ cm ² , and therefore the The excitation rate is W=1.22×10 ³ I (W/cm ² ) sec ⁻¹ , where I is the synchrotron radiation intensity. Since such an auto-ionization state spontaneously separates into ions and electrons at a high speed of 10 ¹² sec ^-1 or more, this excitation speed W is determined by synchrotron radiation with a wavelength of 3050 Å in the two-electron excited state 3s3p ^2. automatic ionization state 3s3p4s
It can be the ionization rate via . On the other hand, when photoionizing directly from the two-electron excited state 3s3p ² , which is an example of following the conventional ionization method,
Its photoionization cross section is σ _i =1.35×10 ^-28 [λ ₂ (Å)] ³
cm ² and therefore its ionization rate is W=6.82×
10 ^-14 [λ ₂ (Å)] ⁴ I (W/cm ² ) sec ^-1 . here,
The synchrotron radiation wavelength λ ₂ must satisfy λ ₂ <5205 Å in order to exceed the ionization limit. FIG. 5 shows this ionization rate W as a function of the synchrotron radiation wavelength λ ₂ for various synchrotron radiation intensities I. As shown in the figure, when the wavelength λ ₂ is changed at a certain synchrotron radiation light intensity, the ionization rate W changes continuously, but λ ₂ is the resonance between the two-electron excited state 3s3p ² and the autoionization state 3s3p4s. wavelength
At 3050 Å, the temperature increases discontinuously by more than two orders of magnitude.
Therefore, in the case of the ionization method in this invention,
Compared to conventional resonant optical excitation and ionization methods, the ionization efficiency for input light energy is more than two orders of magnitude higher, and since only resonance is used, the energy level and wavelength of synchrotron radiation light should not match those of impurity atoms. If you select , you can ionize only the substance you want to ionize, and you can achieve high purity.

Furthermore, by changing the wavelength of the synchrotron radiation light, ion beams of various types of substances can be easily generated.In this case, various types of substances to be ionized can be introduced into the ion beam generation container in advance. It's okay to stay. The method of the present invention, which can easily change the type of ion beam generated in this way, is different from conventional methods, and has the advantage of being able to perform two or more processes using ion beams in succession. There is.

Next, embodiments of the invention will be described with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. In the figure, 1 is a container into which a substance to be ionized is introduced, 1a is a gas introduction hole for introducing the substance into the container 1, and 1b is an evacuation device for evacuating the container 1 (see FIG. (not shown), 3 is a synchrotron radiation generating section which is formed by providing a wiggler or an undulator in an accelerator and generates synchrotron radiation B3 with a narrow wavelength width of 1762 Å; 11 is a synchrotron radiation generating section connected to the generating section 3 and the above A slit provided between the container 1 and the container 1, 6 is an electrode, and 6a is a terminal for applying a voltage to the electrode 6. 8 is the sample, 8a
is a sample stand that holds the sample 8, and the sample stand 8
A DC voltage is applied between a and the electrode 6,
This generates an extraction electric field for extracting the ionized substance as an ion beam.
This extraction electric field has a phase that is temporally synchronized with the synchrotron radiation light B3.

Next, the operation will be explained.

Let us consider the case where an aluminum ion beam is generated by the apparatus of this embodiment. First, aluminum vapor 10 is introduced into the container 1 through the gas introduction hole 1a. Then, the synchtron radiation generating section 3 is caused to oscillate. Then, synchtron radiation B3 with a wavelength of 1762 Å is introduced into the container 1 through the slit 11, and as a result, the aluminum vapor 10 changes from the ground state 3P ( ² P ⁰ ) to the autoionization state 3s3p ² ( ² P ⁰ ). The excited vapor is resonantly excited, and as a result, the excited vapor enters an ionic state with a predetermined transition probability.

Further, a DC voltage is applied between the electrode 6 and the sample stage 8a, whereby the ionized aluminum vapor 10 is extracted as an ion beam 9 consisting only of aluminum ions.
The ion beam 9 is irradiated onto the sample 8 .

The features of this embodiment in the above operation description are as follows: First of all, this embodiment performs selective ionization completely using only resonance, so the substance to be ionized and this If aluminum contains impurities other than aluminum, such as oxygen, nitrogen, carbon, hydrogen, etc., and even if the amount is greater than that of aluminum, the energy level and wavelength of the synchrotron radiation will not match those of the above impurities, etc. In this way, a pure aluminum ion beam is obtained in which only the desired element, in this case aluminum, is ionized.

Second, as mentioned above, this embodiment performs selective ionization and ionization by resonant optical excitation, so there is no possibility that electrons or other elements will be excited or that the temperature will rise due to energy absorption. As a result, low-temperature processing can be performed without increasing the temperature of the target sample 8 to be irradiated with the ion beam, such as a substrate in the case of a semiconductor.

Thirdly, if you want to change the type or characteristics of the ion beam, you just need to change the wavelength of the synchrotron radiation.
There is no need to open and close the container to take out a sample or replace the ion source as in the conventional method, and therefore continuous operations such as ion implantation and annealing can be easily performed.

FIG. 3 shows a second embodiment of the invention. In the figure, the same reference numerals as in FIG. 2 indicate the same or equivalent parts, 13 houses the substance 12 to be ionized, 13a is a heater provided on the outer periphery of the container 13, and the container 13 is thereby Above substance 1
It is an oven that evaporates the 2. 15 is a magnet that focuses the ionized aluminum vapor 10 on the axis of the container 1, and 14 is an extraction electrode that extracts the focused aluminum vapor 10 as an ion beam 9.

Next, the operation will be explained.

When aluminum 12, which is an ionized substance, is placed in the container 13 and the oven 13 is heated by the heater 13a, the aluminum 12 melts.
It is vaporized and aluminum vapor 10 is generated. Then, synchrotron radiation B3 is introduced into the container 13 through the slit 11 and irradiated onto the steam 10. As a result, the vapor 10 is excited from the ground state to the auto-ionization state 3s3p ² ( ² P ⁰ ), and as a result, the excited vapor is automatically electrified with a predetermined transition probability to generate aluminum ions, and the aluminum is axially moved by the magnet 15. After being focused in the mind,
The ion beam 9 is emitted by the extraction electrode 14 .

FIG. 4 shows an example of the configuration of a synchrotron radiation generator used in the present invention. In the figure, numeral 21 is a linear accelerator, 22 is an electron storage ring, and 24 is a spectroscopic system, which constitute a synchtron radiation generating device 20. 33 is the generator 20
This is a container that is irradiated with synchrotron radiation.

In the synchrotron radiation introduced into the container 33, electrons are first accelerated in the linear accelerator 21 and shot into the electron storage ring 22, and synchrotron radiation is emitted from the electrons that have reached relativistic speed in the ring 22. The emitted light is further introduced into the spectroscopic system 24, and is made into a single wavelength by the spectroscopic system 24.

〔Effect of the invention〕

As described above, according to the ion beam generator of the present invention, a substance to be ionized is resonantly excited from its ground state to an autoionized state by irradiation with synchrotron radiation light, and the excited vapor is generated with a predetermined transition probability. Since it is automatically ionized into an ionic state, it has excellent ion selectivity and has the effect of improving ionization efficiency with respect to input energy by more than two orders of magnitude compared to conventional resonance optical excitation and ionization methods.

[Brief explanation of drawings]

FIG. 1 is an energy state diagram of a singlet system of aluminum neutral atoms, FIG. 2 is a schematic diagram of the shower type ion beam generator according to the first embodiment of the present invention, and FIG. Schematic configuration diagram of the focused ion beam generator according to the embodiment, No. 4
The figure is a schematic configuration diagram of a synchrotron radiation generator used in the present invention, and FIG. 5 is a state diagram showing the wavelength dependence of the photoionization rate in the excited state 3s3p ² of aluminum neutral atoms. 1, 13, 33... Container, 9... Ion beam, 10... Substance to be ionized, 20...
Synchrotron radiation generation unit, 21...accelerator,
22...Electron storage ring, 24...Spectroscopy system, B3
... Synchrotron radiation. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A container containing a substance to be ionized;
A device for generating an ion beam of the substance, comprising a synchrotron radiation generation unit that irradiates the substance in the container with synchrotron radiation,
An ion beam generator, wherein the synchrotron radiation light generating section generates synchrotron radiation light having a wavelength that resonantly excites the substance from a ground state of energy level to an autoionization state. 2 The synchrotron radiation light generating section generates synchrotron radiation light having a plurality of line spectra with different wavelengths so as to resonantly excite the substance stepwise from the ground state to the autoionization state through the intermediate state. An ion beam generator according to claim 1, characterized in that: 3 The synchrotron radiation light generating section has an accelerator and a spectroscope or spectroscopic system, and generates light that is made from the output from the accelerator and made into a narrow line spectrum by passing through the spectroscope or spectroscopic system. An ion beam generator according to claim 1 or 2, characterized in that: 4. The ion beam generation device according to claim 3, wherein either or both of an electron storage ring and an electron cyclotron are used as the accelerator. 5. Claims 1 to 4, characterized in that the synchrotron radiation light generating section generates synchrotron radiation light having a phase temporally synchronized with the phase of the ion beam extraction electric field. 2. The ion beam generator according to any one of paragraphs. 6. The ion according to any one of claims 1 to 5, wherein the substance is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. Beam generator.