JPS60208033A - Ion beam generator - Google Patents

Abstract

PURPOSE:To improve the ionization efficiency by irradiating a beam from a laser beam generating section comprised of a flush lamp and two color element lasers onto the material to be ionized. CONSTITUTION:Magnesium vapor 10 to be ionized is led into a container 1 while two laser beams B1, B3 from laser beam generating section comprised of a flush lamp and two color element lasers are led through windows 3a, 3b to perform resonance excitation of vapor 10 into first exciting condition through 2,853Angstrom beam B1 in the crossing ion producing space 4 then perform resonance excitation into Rydberg condition through 3,859Angstrom beam then perform ionization through Shutalk effect under the electric field to be produced between the eletrodes 5, 6 synchronously with the laser oscillation thus to take out as an ion beam 9 under the voltage between the electrodes 6, 8a and to irradiate 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 provides an ion beam generator using resonant light excitation and ionization as described above, in which the substance to be ionized is set in the Rydberg state (R
To provide an ion beam generator that can improve the specific beam ionization efficiency by several orders of magnitude compared to conventional resonant optical excitation and ionization methods and has excellent selectivity in selective ionization by using an excited state of ydberg 1evel or a high excitation state close to this. The purpose is to

(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 magnesium ion beam is generated. 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 (
IPO), then resonantly excited to energy level d (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.
The point is to excite p('PO) to Rydberg-like Lt13d(ID), which can be ionized by the Stark effect, or a highly excited state close to this, and then apply an electric field to the excited vapor to ionize it. For example, Rydberg state 1
In the case of 3d (ID), the Rydberg state is resonantly excited by the laser beam B3 of 3859 wavelengths, and in order to further ionize the excited vapor, an electric field expressed by the following formula is applied to the vapor together with the laser beam B3. As a result, ionization is performed from this excited state by the Stark effect.

E (V/an) =0.3125X109·n-4 where n is the effective principal view 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, which directly ionizes from energy level 3d (ID>).Therefore, the output energy of the laser beam can be small. , and because it uses only resonance, the energy level of the laser beam.

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 and electric field strength 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 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 unlike any conventional method.
There is an advantage that two or more steps of processing with an ion beam can be performed in succession.

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

FIG. 2 shows a first embodiment of the first invention of the present application. 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, 1b is a gas exhaust hole, and 3a and 3b are laser beam generating parts (not shown). This is a window that introduces the laser beams Bl and B3 from the inside of the container 1 into the container 1, and the laser beam B1 inside the container 1.

The space where B3 intersects is the ion generation space 4.

Although not shown, the laser generating section is composed of a Franche lamp and two dye lasers excited by the lamp.

Reference numerals 5.6 and 5.6 are electrodes arranged across the ion generation space 4, and 5a and 5a are terminals for applying voltage to the electrodes 5.6, which are used to ionize the substance in the ion generation space 4. Electric field generating section 15 that applies an ionizing electric field
It consists of 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 magnesium ion beam is generated by the apparatus of this embodiment. First, magnesium vapor 10 is introduced into the container l through the gas introduction hole 1a.

In the laser beam generating section, power is supplied to the Franche lamp, thereby exciting the dye laser. Then, the laser beam B1 of 2853 people has a wavelength of 2853 and enters window 3.
a into the vessel 1, and the 3859 laser beam B3 is likewise introduced through the window 3b, and both beams Bl, B3 intersect in the ion production space 4 in the vessel 1, thereby causing the above-mentioned Magnesium vapor 10 is 28
Ground state 3s ('S) by 53 people's laser beam B1
is resonantly excited from the first excited state 3p (IP') to the first excited state 3p (IP'), and then the first excited state 3p (1PO) is resonantly excited to the Rydberg state 13d (ID
) is resonantly excited in a stepwise manner.

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, thereby applying an electric field to the magnesium vapor 10 in the Rydberg state 13d (ID), and as a result, the magnesium vapor 10 is ionized by the Stark effect. Further, a DC voltage is applied between the electrode 6 and the sample stage 8a, whereby the ionized magnesium vapor 10 is extracted as an ion beam 9 consisting only of magnesium 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, It contains impurities other than magnesium, such as oxygen, nitrogen, carbon, and hydrogen, and the amount is higher than that of magnesium (but the energy level of the laser beam.

A pure magnesium ion beam in which only the desired element, in this case magnesium, is ionized can be obtained by making the wavelength not coincident with those of the above-mentioned impurities.

Second, as mentioned above, this embodiment performs selective ionization and ionization by optical resonance excitation, so that electrons and other elements are excited and the temperature rises 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. (Thus, continuous operations such as ion implantation and annealing can be easily performed.

FIG. 3 shows a second embodiment of the first invention of the present application. In the figure, the same reference numerals as in Figure 2 indicate the same or equivalent parts,
13 is an oven containing the substance 12 to be ionized; 13a is a heater provided around the outer periphery of the oven 13; 11 is a container 1 for storing the ionized magnesium vapor 10;
A magnet 14 is an extraction electrode that extracts 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. The laser beam B1 for 2853 people and the laser beam B3 for 3859 people are introduced into the container 1 through the windows 3a and 3b and irradiated onto the vapor 10, and at the same time a voltage is applied to the electrode 5.6. An electric field is applied to the vapor 10. This causes the vapor 10 to change from the ground state 3s (1S) to the first excited state 3.
Rydberg state 13d(ID) via p('PO)
Further, due to the Stark effect, the electrons of the magnesium vapor 10 in the Rydberg state 13d (ID) become free electrons, and thereby magnesium ions are generated in the ion generation space 4, and the magnesium ions are generated by the magnet 11. After being focused on the axis, the ions are emitted as an ion beam 9 by the extraction electrode 14 .

FIG. 4 shows a configuration example of a laser oscillation device in an ion beam generator according to a third embodiment of the first invention of the present application, and FIG. 5 shows a dye cell portion thereof.

In the present invention, the laser beam and electric field 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 also necessary to synchronize the laser beams, and FIGS. 4 and 5 show an example of a synchronization method.

In the figure, 21 is a reflector cell of the laser oscillation device 20;
22 is two dye cells, 23 is one flash lamp, 24 is a mirror, 25 is a plane mirror, 26 is a diffraction grating, 27.2
8 is a laser beam.

In this laser oscillation device 20, one Franche lamp 2
3, the two dye cells 22 are excited, whereby dye laser beams ω1°ω2 having different wavelengths are synchronously oscillated. In this example device, two laser beams ω
1. Due to ω2, the substance to be ionized is resonantly excited stepwise from the ground state to the Rydberg state through the intermediate state.

The above laser beam ω1. In order to make the wavelength of ω2 different, the wavelength can be changed by using different dyes as the 11 dye cells 22, or using the same dye as the two dye cells 22, The wavelengths can be mutually changed by adjusting the coordination angles θ1 and θ2 between the plane mirror 25 and the diffraction grating 26. In this way, the wavelength that resonates with the substance to be ionized can be selected, and each laser beam can be time-synchronized with each other. As a result, substances can be excited stepwise.

Furthermore, the above-mentioned flash lamp 23 is started, and the above-mentioned electrode 5.
By simultaneously applying voltage to 6, the laser beam and the electric field can be temporally synchronized.

In each of the embodiments of the first invention described above, a case has been described in which the substance to be ionized is excited to the Rydberg state and then ionized, but in the second invention of the present application, the substance is excited to a level slightly lower than the Rydberg state. , the material may be excited to a highly excited state that can be ionized by the Stark effect, and then an electric field may be applied to the material to ionize it. Even in this case, substantially the same effect as in each embodiment of the first invention is achieved. be effective.

〔Effect of the invention〕

As described above, according to the ion beam generation/4' device according to the present invention, a substance to be ionized is resonantly excited from its ground state to a Rydberg state or a highly excited state close to it by irradiation with a laser beam, Furthermore, since the substance is changed 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 phase diagram of a singlet system of magnesium neutral atoms, Fig. 2 is a schematic configuration diagram of a shower type ion beam generator according to a first embodiment of the first invention, and Fig. 3 is a diagram of the first embodiment of the shower type ion beam generator. FIG. 4 is a schematic diagram of the laser beam oscillator of the ion beam generator according to the third embodiment of the first invention, and FIG. The dye cell part is shown, and the fifth
Figure (8) is a cross-sectional plan view thereof, and Figure (8) is a cross-sectional front view thereof. DESCRIPTION OF SYMBOLS 1... Container, 15... Electric field generating section, 20... Laser beam generating section, 22... Dye laser, 23... Frangulaan 7'', Bl to B3... Laser beam. The same reference numerals in the middle indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 3 Figure 5 Figure 4 Procedural amendment (voluntary) 59822 Showa year, month, day 3, person making the amendment Representative Hitoshi Katayama Part 4, Agent 5, Claims column of the specification to be amended and Detailed explanation of the invention column 6, Contents of amendment 11) Correct the claims of the specification as shown in the attached sheet. 2) rRydberg 1 on page 4, line 16 of the specification
evel” is corrected to rRydberg 5tate J. (3) Correct "kara Stark" on page 5, line 18 of the same page to "kara, Stark." (4) Correct "electrodes in synchronization" in line 10 of page 9 to "electrodes in synchronization and with a delay of about 1 μsec". (5) "Optical resonance excitation" on page 10, line 13 is corrected to "resonant optical excitation." (6) In the third line of page 12, “electrode at the same time” was changed to “electrode at the same time”
Corrected to ``electrode delayed by about μsec''. Claims +l) A container containing a substance to be ionized, a laser beam generator that irradiates the substance in the container with a laser beam, and an electric field that applies an electric field to the substance in the container. In the apparatus for generating an ion beam of the substance, the laser beam generating unit includes a Fransch lamp, and a laser beam generating unit that is excited by the Franch lamp and resonantly excites the substance from the ground state of the energy level to the Rydberg state. and a dye laser that generates a laser beam having a wavelength, and the electric field generating section generates an electric field that changes the substance from the Rydberg state to the ion state by the Stark effect. Generator. (2) The laser beam generating section is characterized in that it generates a plurality of laser beams with different wavelengths that resonantly excite the substance stepwise from the ground state to the Rydberg-like state through the intermediate state. An ion beam generator according to claim 1. (3) The laser beam generating section includes one flash lamp and a plurality of dye lasers that are excited by the flash lamp and can be synchronized with each other in time. Ion beam generator. (4) The substance according to any one of claims 1 to 1, wherein the substance is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. Ion beam generator. (5) Ion beam generation according to any one of claims 1 to 4, wherein the electric field also serves as an extraction electric field for extracting the ionized substance as an ion beam. Device. (6) A container containing a substance to be ionized, a laser beam generation unit that irradiates the substance in the container with a laser beam, and an electric field generation unit that applies an electric field to the substance in the container, In an apparatus for generating an ion beam of a substance, the laser beam generating section has a flash lamp and a wavelength that, when excited by the flash lamp, resonantly optically excites the substance from a ground state of energy level to a highly excited state close to the Rydberg state. and a dye laser that generates a laser beam, and the electric field generating section generates an electric field that changes the substance from the highly excited state to the ionic state by the Stark effect. .

Claims (1)

[Scope of Claims] fi+ A container that contains a substance to be ionized, a laser beam generator that irradiates the substance in the container with a laser beam, and an electric field generator that applies an electric field to the substance in the container. In the apparatus for generating an ion beam of the substance, the laser beam generating section includes a flash lamp, and a flash lamp that emits a wavelength that is excited by the flash lamp to resonantly excite the substance from the ground state of the energy level to the Rydberg state. and a dye laser that generates a laser beam having the following characteristics, and the electric field generating section generates an electric field that changes the substance from the Rydberg state to the ion state by the Stark effect. . (2) The laser beam generating section is characterized in that it generates a plurality of laser beams having 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 laser beam generating section is comprised of one flash lamp and a plurality of dye lasers that are excited by the laser beam from the flash lamp and can be time-synchronized with each other. The ion beam generator according to item 2. (4) The substance described in any one of claims 1 to 5 is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. Ion beam generator. (5) Ion beam generation according to any one of claims 1 to 4, wherein the electric field also serves as an extraction electric field for extracting the ionized substance as an ion beam. Device. (6) comprising a container containing a substance to be ionized, a laser beam generation unit that irradiates the substance in the container with a laser beam, and an electric field generation unit that applies an electric field to the substance in the container, In the apparatus for generating an ion beam of the substance, the laser beam generating section includes a flash lamp and a wavelength that is excited by the flash lamp and resonantly excites the substance from the ground state of the energy level to a highly excited state close to the Rydberg state. and a dye laser that generates a laser beam having the following characteristics, and the electric field generating section generates an electric field that changes the substance from the highly excited state to an ion state by the Stark effect. Generator.