JPS6127041A - 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 an autoionization state immediately before ionizing the substance. CONSTITUTION:Boron vapor 10 is introduced into a case 1 through a gas introduction hole 1a and voltage is applied across electrodes 5 and 6. As the result, electrons produced by glow electric discharge or gas electric discharge strike the boron vapor 10 to resonantly excite it to a metastable state. Synchronously with the above voltage application, light (B4) radiated by a synchrotron is introduced into the case 1 through a slit 1c to resonantly excite the boron vapor 10 to an autoionization state and then ionized with a given transition probability. D.C. voltage is applied across the electrode 6 and a sample base 8a and the ionized boron vapor 10 is irradiated upon a sample 8 as an ion beam 9 consisting of boron ions alone.

Description

[Detailed description of the invention] [Technical field of invention] The present invention utilizes semiconductor processing equipment to modify materials.

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 that use light such as laser light. One is to irradiate a solid such as a metal with laser light and use the resulting plasma as an ion source, or 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 and resonates a single wavelength such as a laser beam with the energy level of the substance to be ionized, thereby ionizing the substance (Japanese Patent Application Laid-Open No. 1983-1991). (Refer to Publication No.-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 provides an ion beam generation apparatus using resonant light excitation and ionization, in which a substance to be ionized is set in an autoionization state (AutoionLzationstate) as a state immediately before the substance is ionized by resonant light excitation.
By using conventional resonant optical excitation.

The object of the present invention is 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, taking as an example the case of generating a boron ion beam. FIG. 1 is an energy level diagram of a boron neutral atom.

In the conventional ionization method, for example, the wavelength is 2497.

Three laser beams B1 of 1.17 μ and 8668 A
~B3 is a method of irradiating the boron vapor to be ionized, that is, boron atoms in the ground state 2s22p (2PO) are first resonantly excited to the excited state 3s (23) by the 2497 laser beam B1, and then 1.17μ ,
8668 people laser beam B2. 3p (2
PO), 5s (23), and further ionized by the laser beam B3.

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 radiation, like laser light, has directionality, and has much higher intensity and higher energy photons than laser light. Therefore, as shown in Figure 1, one photon B4 can excite a relatively low level. state can be excited to a highly excited state. Furthermore, the fundamental difference between the method of the present invention and the conventional method is that the final excited state is an auto-ionization state, and in this excited state, the excited vapor is exactly auto-ionized with a predetermined transition probability. Note that excitation from the ground state to the lower excited state is performed by glow discharge or the like.

In the case of the ionization method in the device of this invention, the collision cross section for ionization is several orders of magnitude higher than that in the conventional ionization method, which directly ionizes from the state of energy level 5s (2S). Therefore, the output energy of light is small,
Furthermore, since only resonance is used, if the wavelength of the synchrotron radiation light is selected so as not to match the energy level of the impurity atoms, only the substance to be ionized can be ionized.
Moreover, it can produce products with high purity.

In addition, by changing the wavelength of the spectroscopic single-wavelength synchrotron radiation, it is possible to easily generate ion beams of other types of substances. You can also install it inside. The method of the present invention, which can easily change the type of ion beam generated in this way, is unlike any conventional method. There are advantages to doing so.

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, ■
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;
3 is an exhaust passage connected to a vacuum evacuation device (not shown) for differentially evacuating the container 1 to create a vacuum, IC is a slit, and 3 is an accelerator equipped with a wiggler or an undulator. This is a synchrotron radiation generating section that generates synchrotron radiation light B4 having a narrow wavelength width.

Further, 5 and 6 are electrodes arranged to sandwich the synchrotron radiation light B4, and 5a and 6a are terminals for applying a voltage to the electrode 5.6.
It constitutes a gas discharge generating section 15 that generates F discharge.

Note that when the substance to be ionized is introduced into the container 1 as a gas in a compound or molecular state, the excitation gas discharge also serves as a gas discharge to bring the substance into a neutral atomic state. It's okay.

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.

Next, the operation will be explained.

Let us consider the case where a boron ion beam is generated by the apparatus of this embodiment. First, boron vapor 10 is introduced into the container 1 through the gas introduction hole 1a. Then, a voltage is applied to each of the electrodes 5 and 6 from the terminals 5a, 5a, and as a result, electrons due to glow discharge or gas discharge collide with the boron vapor 10, and as a result, the boron vapor 10 is in its ground state 2s22
It is resonantly excited from p(2PO) to the metastable state 232p2 (4P). In addition, in time synchronization with the voltage application, synchrotron radiation B4 with a wavelength of 2067 people is introduced from the synchrotron radiation generating section 3 into the container 1 via the slit IC, thereby causing the metastable state 2S2.
The boron vapor 10 at p2 (4P) is automatically ionized 2s2p3 by the synchrotron radiation B4 of 2067 people.
s (4PO), and the excited vapor becomes 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 boron vapor 10 is extracted as an ion beam 9 consisting only of boron 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, Even if impurities other than boron, # elements, nitrogen, carbon, hydrogen, etc. are included, and the amount is greater than boron, the wavelength of the synchrotron radiation light should not be made to match the energy level of the impurity atoms. This results in a pure boron ion beam in which only the desired element, in this case boron, 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 can simply change the wavelength and discharge conditions of the spectroscopic single-wavelength synchrotron radiation.
There is no need to open or close the container to replace the ion source, 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, 11 is a magnet coil that focuses the ionized beryllium vapor 10 on the axis of the container 1, and 14 is the focused boron vapor 1.
This is an extraction electrode that extracts 0 as an ion beam 9.

Next, the operation will be explained.

First, boron vapor 10 is introduced into the container 1 through the gas introduction hole 1a.
to be introduced within. Then, a voltage is applied to the electrode 5.6, and the electrons of the gas discharge collide with the vapor 10, and synchrotron radiation B4 of 2067 people is generated in time synchronization with this.
is introduced into the container 1 through the slit IC and irradiated onto the steam 10. As a result, the steam 10 passes through the metastable state 2s2p2 (4p) and enters the autoionization state 2s2.
p3s (4pO), and the excited vapor is
It becomes an ion state with a certain transition probability, thereby generating boron ions in the ion generation space 4, which are focused to the axis by the magnet coil 11 and then emitted as an ion beam 9 by the extraction electrode 14.

FIG. 4 shows an example of the configuration of a synchrotron radiation generator 20 used in the present invention. In the figure, 21 is a linear accelerator of the synchrotron radiation light generating device 20, 22 is an electron storage ring, 23 is a wiggler, 24 is a spectroscopic system, and 33 is a container.

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,
The light is further introduced into the spectroscopic system 24 and made into a single wavelength by the spectroscopic system 24. In this example, Wiggler 2
3, the range of wavelength tunability can be expanded in addition to the wavelength tunability of the spectroscopic system 24, and ion beams of various materials can be generated.

〔Effect of the invention〕

As described above, according to the ion beam generator of the present invention, the substance to be ionized is excited from the ground state of its energy level to a relatively lower excited state by gas discharge, and the substance is further excited by synchrotron radiation. Since the excited state is changed to an automatic ionization state by irradiation with light, the ionization efficiency and ion selectivity can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is an energy state diagram of a neutral boron atom ゛, FIG. 2 is a schematic diagram of a shower-type ion beam generator according to a first embodiment of the present invention, and FIG. 3 is a diagram of a second embodiment of the present invention. FIG. 4 is a schematic diagram of a synchrotron radiation light generator used in the present invention. 1.33... Capacity a, 3.20... Synchrotron radiation generating section, 15... Gas discharge generating section, B4... Synchrotron radiation light. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (10)

[Claims] (1) A container containing a substance to be ionized, a synchrotron radiation light generating section that irradiates the substance in the container with synchrotron radiation light, and generating a gas discharge in the atmosphere of the substance in the container. and a gas discharge generating section for generating an ion beam of the substance, wherein the gas discharge generating section excites the substance from a ground state of energy level to a relatively lower excited state by gas discharge. , the synchrotron radiation light generating section is configured to include a wiggler or an undulator in an accelerator, and generate synchrotron radiation light having a wavelength that resonantly excites the substance from the excited state to the autoionization state. Features of the ion beam generator. (2) The ion beam generator according to claim 1, wherein the synchrotron radiation generating section generates channeling radiation as synchrotron radiation. (3) The synchrotron radiation light generating section generates a plurality of synchrotron radiation lights of different wavelengths to resonantly excite the substance stepwise from the relatively lower excited state to the autoionization state via the intermediate state. The ion beam generator according to claim 1 or 2, wherein the ion beam generator generates an ion beam. (4) The synchrotron radiation light generating section has an accelerator and a spectrometer or 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 any one of claims 1 to 3, characterized in that: (5) The ion beam generation device according to any one of claims 1 to 4, wherein one or both of an electron storage ring and an electron cyclotron is used as the accelerator. (6) The ion beam generator according to any one of claims 1 to 5, wherein the relatively lower excited state is a metastable state of the energy level of the substance. (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 ion beam generator according to any one of claims 1 to 8, wherein the synchrotron radiation light and the gas discharge are temporally synchronized in phase. (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.