JPS60208035A - Ion beam generator - Google Patents

Abstract

PURPOSE:To improve the ionization efficiency by irradiating two laser beams having different wavelength onto material to be ionized and forming a gas discharge producing section at the crossing section of beams and causing resonant light excitation. CONSTITUTION:Magnesium 10 to be ionized is led into a container 1 while two laser beams B1, B3 are led through the windows 3a, 3b to form a gas discharge producing section 15 in an ion producing space 4 at the crossing section to perform resonant excitation of vapor 10 into first exciting condition through 2,853Angstrom beam B1 while to perform resonant excitation into Rydberg condition through 3,859Angstrom beam. Thereafter, the vapor 10 is collided against electrons under the electric field to be produced synchronously with the laser oscillation between the electrodes 5, 6 and ionized to be taken out as an ion beam 9 composed only of magnesium ions and irradiated onto a specimen 8. Consequently, the ionization efficiency and the selectivity of ion can be improved considerably.

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 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 to ionize a substance by resonating a single wavelength such as a laser beam with the energy level of the substance to be ionized. It is related to.

[Summary of the invention]

The present invention uses the Rydberg-like Q (RydbergIeνel) of the 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. .

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, taking as an example the case of generating a magnesium ion beam. FIG. 1 is an energy level diagram of a neutral magnesium atom.

In the conventional ionization method, for example, the wavelength is 2853.

This is a method of irradiating the magnesium vapor to be ionized with two laser beams Bl and B2, that is, the magnesium atoms in the ground state 3s ('S) are first ionized into 2
The first excited state 3p is generated by the laser beam B1 of 853 people.
CI PO), then resonantly excited to energy level 3d (I D) by the laser beam B2 of 5528 people, and further ionized by the laser beam B1 of 2853 people.

The ionization method in the device of the present invention differs from the conventional ionization method described above in that magnesium vapor is brought into the first excited state 3.
p ("P') to Rudberg-like 13d (ID) is resonantly excited by, for example, a laser beam B3 with a wavelength of 3859, and the ionization of the excited vapor from the excited state is achieved by electron collision due to gas discharge, etc. It is in.

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 energy level 3d (ID). Therefore, the output energy of the laser beam is small, and since only resonance is used, the energy level of the laser beam can be reduced.

By selecting wavelengths that do not match those of impurity atoms, it is possible to ionize only the substance to be ionized, and moreover, it is possible to ionize the substance with high purity.

Furthermore, by changing the wavelength of the laser beam, ion beams of other types of substances can be easily generated.In this case, various types of substances to be ionized may be introduced into the ion beam generation container in advance. . 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, 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;
3a and 3b are gas exhaust holes, and 3a and 3b are laser beams J, B1. This is a window for introducing B3 into the container 1, and the laser beams B1 and B in the container 1 are
The space where 3 intersects is the ion generation space 4. Note that as the laser beam generating section, a laser such as a wavelength tunable laser or a free electron laser is used.

Reference numerals 5.6 and 5.6 are electrodes arranged across the ion generation space 4, 5a and 5a are terminals for applying voltage to the electrodes 5.6, and these are the gas that generates high frequency gas discharge in the ion generation space 4. The gas discharge generator 15 comprises a Takaoka 1fflffi source that resonates sufficiently to change the substance from its Rydberg state to an ionic state. In addition, when the substance to be ionized is introduced into the container l as a gas in a compound or molecular state, the gas discharge for ionization should also serve as the gas discharge for converting the substance into a neutral element 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 magnesium ion beam is generated by the apparatus of this embodiment. First, magnesium vapor 1O is introduced into the container 1 through the gas introduction hole 1a.

Then, the laser beam generator oscillates, and as a result, the laser beam B1 of 2853 people with a wavelength is introduced into the container 1 through the window 3a, and the laser beam B3 of 3859 people is introduced into the container 1 through the window 3a.
is similarly introduced through window 3b, and both beams Bl, B3
intersect in the ion generation space 4 in the container 1, and as a result, the magnesium vapor 10 is resonantly excited from the ground state 3s (IS) to the first excited state 3p ('PO) by the 2853 laser beam B1, and further The first excited state 3p ('PO
) is resonantly excited in a stepwise manner to the Lurid Helgian state 13d (ID).

Also, in time synchronization with the laser oscillation, the electrode 5 and the electrode 6 are
A voltage is applied to each of the terminals 5a and 6a, whereby electrons due to gas discharge collide with the magnesium vapor 10 in the Rydberg state 13d (ID), and as a result, the magnesium vapor 10 is ionized. Further, a DC voltage is applied between the electrode 6 and the sample stage 8a, so that the ionized magnesium vapor 1
0 is an ion beam 9 consisting only of magnesium ions
The sample 8 is irradiated with the ion beam 9.

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 l, in this case, Even if impurities other than magnesium, such as oxygen, nitrogen, carbon, hydrogen, etc. are included, and the amount is greater than magnesium, the energy level 5 wavelength of the laser beam should not be made to match those of the above impurities, etc. A pure magnesium ion beam is obtained in which only the desired element, in this case magnesium, 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 can simply change the wavelength of the laser beam and the applied voltage, and there is no need to open and close the container to take out the sample or replace the ion source, as in the past. 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. 2 indicate the same or equivalent parts, 13 is an oven containing the substance 12 to be ionized, 13a is a heater provided on the outer periphery of the open 13, and 11 is ionized magnesium vapor. 10 is a magnet for focusing on the axis of the container 1, and 14 is an extraction electrode for extracting the focused magnesium vapor 10 as an ion beam 9.

Next, the operation will be explained.

Magnesium 12, which is a substance to be ionized, is placed in the oven 13, and when the oven 13 is heated by the heater 13a, the magnesium 12 is melted and vaporized to generate magnesium vapor 10, and the vapor 10 passes through the gas introduction hole 1a into the container. 1. Laser beam B1 for 2,853 people and laser beam B3 for 3,859 people are introduced into the container 1 through the windows 3a and 3b and irradiated onto the steam 10, and at the same time, a voltage is applied to the electrodes 5 and 6. Electrons generated by the gas discharge collide with the vapor IO.

As a result, the vapor 10 is excited in a stepwise manner from the ground state 3s ('S) to the Rydherg state 13d (ID) via the first excited state 3p (IPO), and further to the Rydherg state 13d (ID) due to the electron collision caused by the gas discharge. I
The electrons in the magnesium vapor 10 in D) become free electrons, thereby generating magnesium ions in the ion generation space 4. After the magnesium ions are focused to the axis by the magnet 11, they are focused as an ion beam 9 by the extraction electrode 14. released.

FIG. 4 shows an example of the configuration of a laser oscillation device in an ion beam generator according to a third embodiment of the present invention.

In the present invention, the laser beam and gas discharge for ion generation need to be synchronized in time, and in order to excite the elements in a stepwise manner, a plurality of laser beams each having a specific frequency are required. Of course, it is necessary to synchronize a plurality of laser beams, and FIG. 4 shows an example of a synchronization method.

This laser oscillation device 20 includes three wavelength-tunable dye lasers 22, 23, 24, an excitation source laser 21 for exciting each of the dye lasers 22 to 24, and half mirrors 25, 2.
6 and a total reflection mirror 27. By configuring the excitation source with one laser 1 in this way, the oscillated laser beam ω1. ω2. ω3 becomes temporally synchronized. and oscillation of the excitation source laser 21,
By applying voltage to the electrodes 5.6 at the same time, the laser beam and the gas discharge can be synchronized in time.

〔Effect of the invention〕

As described above, according to the ion beam generator of the present invention, the substance to be ionized is resonantly excited from its ground state to the Rydberg state by irradiation with a laser beam, and the substance is then brought out of the excited state by gas discharge. Since it is made into an ionic state, it has the effect of greatly improving ionization efficiency and ion selectivity.

[Brief explanation of drawings]

FIG. 1 is an energy phase diagram of a singlet system of magnesium 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. A schematic configuration diagram of a focused ion beam generator according to an embodiment, and FIG. 4 is a block diagram of a laser beam oscillator of an ion beam generator according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Container, 15... Gas discharge generating part, 20...
Laser beam Q raw fa, B1 to B3... Laser beam. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa 1 Figure 3 Figure 4 procedural amendment (voluntary) 20 Name of the invention Ion beam generator 3, relationship to the person making the amendment Case Patent applicant address 2 Marunouchi, Chiyoda-ku, Tokyo Chome 2-3 Name
(601) Mitsubishi Electric Co., Ltd. Representative Hitoshi Katayama 4, Agent 5, Detailed description of the invention in the specification to be amended, and drawings (Figure 1) 6. Contents of the amendment (11th specification No. Set rlevel J on page 4, line 14 to [5
Corrected to tate J. (2) On page 6, lines 5 and 6, "the energy level and wavelength of the laser beam are related to those of impurity atoms" is corrected to "the wavelength of the laser beam is related to the energy level of impurity atoms." (3) On page 9, lines 19-20, ``The energy level and wavelength of the laser beam are related to those of the impurities, etc.'' is corrected to ``The wavelength of the laser beam is related to the energy level of the impurity atoms.'' (4) Correct Figure 1 as shown in the attached sheet. that's all

Claims (1)

[Scope of Claims] (11) A container containing a substance to be ionized, a laser beam generator that irradiates the substance in the container with a laser beam, and a laser beam that intersects with the substance in the atmosphere of the substance in the container. A device for generating an ion beam of the above substance, comprising: a gas discharge generating unit that generates a gas discharge;
The laser beam generating section generates a laser beam having a wavelength that resonantly excites the substance from the ground state of energy level to the Rydberg state, and the gas discharge generating section generates a laser beam that excites the substance from the ground energy level to the Rydberg state by gas discharge. An ion beam generator characterized in that it converts a state into an ion state. (2) The laser beam generating section is characterized in that it generates a plurality of laser beams with different wavelengths to resonantly excite the substance stepwise from the ground state to the Rydberg state via the intermediate state. An ion beam generator according to claim 1. (3) The ion beam generating device according to claim 1 or 2, wherein a wavelength tunable laser is used as the laser beam generating section. (4) The ion beam generating device according to claim 1 or 2, wherein a free electron laser is used as the laser beam generating section. (5) The laser beam generating section is comprised of one excitation laser and a plurality of dye lasers that are excited by the laser beam from the excitation laser and can be synchronized with each other in time. The ion beam generator according to scope 2. (6) The ion beam generator according to any one of claims 1 to 5, wherein the gas discharge generating section generates a high-frequency discharge. (7) The ion beam generator according to claim 6, wherein the gas discharge generating section has a high frequency power source that resonates so that the substance changes from its Rydberg state to an ionized state. (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 element state. An ion beam generator according to any one of claims 1 to 7.