JPS6127043A - Ion beam generator - Google Patents

Abstract

PURPOSE:To greatly improve the ionization efficiency and the ionic specificity of an ion beam generator by resonantly exciting the ionization substance to a Rydberg state immediately before ionizing the substance. CONSTITUTION:Beryllium vapor 10 is introduced into a case 1 through a gas introduction hole 1a and electrons produced by RF electric discharge induced by an induction coil 11 strike the beryllium vapor 10 to excite it to a metastable state. Synchronously with the above excitation of the beryllium vapor 10, light (B3) radiated by a synchrotron is introduced into the case 1 through the slit 1c to resonantly excite the beryllium vapor 10 to a Rydberg state. After that, the excited beryllium vapor 10 is ionized by an electric field produced by a field generator 15. D.C. voltage is applied across an electrode 6 and a sample base 8a and the ionized beryllium vapor 10 is irradiated upon a sample 8 as an ion beam 9 consisting of beryllium ions alone.

Description

[Detailed description of the invention] [Technical field of invention] The present invention is applicable to material modification including semiconductor processing equipment.

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 irradiate it onto a gas or liquid. to create plasma and use it as an ion source.
One is to use a variable wavelength light source to ionize a substance to be ionized by resonating a single wavelength such as a laser beam with the energy level of the substance to be ionized (Japanese Patent Laid-Open No. 1983-1993).
0-22999).

The present invention relates to the latter, and uses synchrotron radiation rather than laser light as a light source.

[Summary of the invention]

The present invention uses the Rydberg state of a substance to be ionized as the state immediately before the substance is ionized by resonant light excitation in the above-mentioned resonant light excitation and ionization type ion beam generation apparatus, thereby improving the conventional resonance light excitation and ionization method. .

It is an object of the present invention to provide an ion beam generator that can improve the ionization efficiency for input light energy by several orders of magnitude 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 using an example in which a beryllium ion beam is generated. FIG. 1 is an energy level diagram of beryllium neutral atoms.

Conventional ionization methods, for example, have wavelengths of 2349 and 3
This is a method of irradiating the beryllium vapor to be ionized with two laser beams Bl and B2 of 2,000 people, that is, the beryllium atoms in the ground state 2s (Is) are first ionized into 2349
The first excited state fi 2 p is generated by the human laser beam B1.
(1p O), and then ionized by a laser beam B2 of 3°00A.

The ionization method in the apparatus of the present invention differs from the conventional ionization method described above in that synchrotron radiation, particularly relativistic synchrotron radiation, is used as an excitation light source. Synchrotron synchrotron radiation has directionality like laser light, and has much higher intensity and higher energy photons than laser light. Therefore, as shown in Figure 1, beryllium vapor can be relatively Can be excited from a lower excited state to a higher excited state. Furthermore, the fundamental difference between the method of the present invention and the conventional method is that the final excited state is set to the Rydberg state, and ionization from the excited state is performed by the Stark effect by applying an electric field as shown in the following equation.

E (V/cm) =0.3125x109 n-4 where n is the effective quantum number of the Rydberg state.

In the case of the ionization method in this inventive device, the collision cross section for ionization is several orders of magnitude higher than in the conventional ionization method, in which beryllium vapor is directly ionized from the energy level 2p (IPO) using a laser beam B2 with a wavelength of 3000. . Therefore, the output energy of single-wavelength synchrotron radiation is small, and since the excitation is not from the ground state but from a metastable state, the wavelength of the photon can be short. By selecting the wavelength of the synchrotron radiation light so that it does not match the energy level of the impurity atoms, only the substance to be ionized can be ionized, and the substance can be highly purified.

Furthermore, by changing the wavelength and electric field strength of the synchrotron radiation light, ion beams of other 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. You can leave it there. The method of the present invention, which allows the type of ion beam generated to be easily changed, is different from conventional methods, and has the advantage of being able to perform two or more processing steps using an ion beam in succession. be.

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

FIG. 2 shows a first embodiment of the present invention, in which 1
1a is a container into which the substance to be ionized is introduced; 1a is a gas introduction hole for introducing the substance into the container 1; 1b is a gas introduction hole for introducing the substance into the container 1;
is an exhaust passage connected to a vacuum evacuation device (not shown) for evacuating the container 1, IC is a slit, and 3 is 19
This is a synchrotron radiation generating section that generates synchrotron radiation B3 with a narrow wavelength width.

Further, 5 and 6 are electrodes arranged to sandwich the synchrotron radiation light B3, and 5a and 6a are terminals for applying voltage to the electrodes 5 and 6, and these apply an electric field to the substance in the container 1. An electric field generating section 15 is configured. Further, 11 is an induction coil which is an RF discharge generating section that generates RF discharge in the above-mentioned material atmosphere. Note that the substance to be ionized may be a compound or a gas in a molecular state, which also serves as a gas discharge.

8 is a sample, and 8a is a sample stand that holds the sample 8. A direct current voltage is applied between the sample stand 8a and the electrode 6, and a drawer is used to extract the ionized substance as an ion beam. An electric field is generated. Note that the ionization electric field may also serve as the extraction electric field.

Next, the operation will be explained.

Let us consider the case where a beryllium ion beam is generated by the apparatus of this embodiment. First, beryllium vapor 10 is introduced into the container 1 through the gas introduction hole 1a. and the above induction coil 1
1 causes an RF discharge, and in synchronization with this, the synchrotron radiation light generating section 3 oscillates, and further, in time synchronization with the oscillation, a voltage is applied to each of the electrodes 5 and 6 from the terminals 5a and 5a. applied. As a result, the beryllium vapor 10 in the ground state 2s (Is) is bombarded with electrons due to the RF discharge, and as a result, the beryllium vapor 10 is excited to the metastable state 2p (3PO).

Also, due to the oscillation of the synchrotron radiation light generating section 3, 1
907 people's synchrotron radiation B3 is Sri Nodo IC
The beryllium vapor 10 is thereby resonantly excited from the metastable state 2p (3PO) to the Rydberg state 12d (3D), and finally the excited vapor is Ionized by an electric field. Further, a DC voltage is applied between the electrode 6 and the sample stage 8a, whereby the ionized beryllium vapor 10 is extracted as an ion beam 9 consisting only of beryllium ions. The sample 8 is irradiated.

The characteristics of this embodiment in the above operation description are as follows: First of all, since this embodiment performs selective ionization completely using only resonance, the substance to be ionized in the container 1, in this case, Beryllium contains impurities such as 2 oxygen, nitrogen, carbon, and hydrogen, and the amount thereof is higher than that of beryllium (but the wavelength of the synchrotron radiation light must not match the energy level of the impurity atoms mentioned above). A pure beryllium ion beam is obtained in which only the desired element, in this case beryllium, 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.

Third, if you want to change the type or characteristics of the ion beam, you only need to change the wavelength of the spectroscopic single-wavelength synchrotron radiation light and the applied voltage. There is no need to open and close the container, 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 those in FIG. serves as an oven in which the substance 12 is evaporated.

Further, 14 is an extraction electrode that extracts the beryllium vapor 1o as an ion beam 9.

Next, the operation will be explained.

When beryllium 12, which is a substance to be ionized, is placed in the oven 13 and the oven 13 is heated by the heater 13a, the beryllium 12 is melted.

It is vaporized to generate beryllium vapor 1o. Then, an RF discharge is generated by the induction coil 11, and in synchronization with this, the synchrotron radiation B3 of 1907 people is released)Ic
The vapor 10 is introduced into the oven 13 through the electrodes 5 and 6, and a voltage is applied to the electrodes 5 and 6 to generate an electric field, which causes the vapor 10 to change from the ground state 2S (Is) to the excited state 2p (3P
O) is excited to the Rydberg state 12d (3D), and the electrons of the beryllium vapor 10 in the Rydberg state 12d (3D) become free electrons, thereby generating beryllium ions in the oven 13, and the beryllium The ions are emitted as an ion beam 9 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, 21 is linearly accelerated steam, 2
2 is an electron storage ring, and 24 is a spectroscopic system, which constitute a synchrotron radiation generating device 20. 33 is a container to which synchrotron radiation light from the generator 20 is irradiated.

In the synchrotron radiation introduced into the container 33, electrons are first accelerated by 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. is,
Further, the emitted light is introduced into a spectroscopic system 24, where it is made into a single wavelength.

〔Effect of the invention〕

As described above, according to the ion beam generator of the present invention, a substance to be ionized is excited to a relatively lower excited state by gas discharge, and is changed from the excited state to the Rydberg state by irradiation with synchrotron radiation light. Since the material is resonantly optically excited and then brought from the excited state to the ion state by applying an electric field, the ionization efficiency and ion selectivity can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is an energy state diagram of beryllium neutral atoms a=4-≠flame≠〒Φ, Fig. 2 is a schematic configuration diagram of a shower-type ion beam generator according to the first embodiment of the present invention, and Fig. 3 4 is a schematic diagram of a focused ion beam generator according to a second embodiment of the present invention, and FIG. 4 is a schematic diagram of a synchrotron radiation generator used in the present invention. 1.13.33... Container, 3.20-... Synchrotron radiation generating section, 11... Gas discharge generating section, 15.
...Electric field generation part, B3... Synchrotron radiation light. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (10)

[Claims] (1) A container that contains a substance to be ionized, a synchrotron radiation generation section that irradiates the substance in the container with synchrotron radiation light, and an electric field generation section that applies an electric field to the substance in the container. and a gas discharge generation unit that generates a gas discharge in the atmosphere of the substance in the container, the apparatus for generating an ion beam of the substance, wherein the gas discharge generation unit sets the substance to an energy level by gas discharge. The synchrotron radiation light generating section excites the substance from the ground state to a relatively lower excited state, and the synchrotron radiation light generating section has a synchrotron radiation having a wavelength that resonantly excites the substance from the relatively lower excited state to the Rydberg state. An ion beam generator that generates synchrotron radiation, wherein the electric field generator generates an electric field that changes the substance from the Rydberg state to the ion state by the Stark effect. (2) The synchrotron radiation generating section generates a plurality of synchrotron radiation beams having different wavelengths to resonantly excite the substance in a stepwise manner from the relatively lower excited state to the Rydberg state via the intermediate state. The ion beam generator according to claim 1, wherein the ion beam generator generates an ion beam. (3) The synchrotron radiation light generating section has an accelerator and a spectrometer or a spectroscopic system, and generates light in which the output from the accelerator is made into a narrow line spectrum by passing through the spectrometer 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 one or both of an electron storage ring and an electron cyclotron is used as the accelerator. (5) The ion beam generator according to any one of claims 1 to 4, wherein the relatively lower excited state is a metastable state. (6) The ion beam according to any one of claims 1 to 5, characterized in that the electric field for ionization due to the Stark effect of the electric field generating section also serves as an extraction electric field for extracting ions as a beam. Generator. (7) The ion beam generator according to any one of claims 1 to 6, wherein the gas discharge generating section generates radio frequency (RF) discharge. (8) The substance is introduced into the container as a compound or molecular gas, and the gas discharge also serves as a gas discharge to bring the substance introduced into the container into a neutral atomic state. An ion beam generator according to any one of claims 1 to 7, characterized in that: (9) The synchrotron radiation, gas discharge, and electric field are as follows:
9. The ion beam generator according to claim 1, wherein the phases of at least two of these can be temporally synchronized. (10) According to any one of claims 1 to 9, the substance is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. ion beam generator.