JPS60235347A - Ion beam generating apparatus - Google Patents

Abstract

PURPOSE:To sharply improve ionization efficiency and ion selectivity by exciting a substance to be ionized to a comparatively lower exciting condition through gasdischarge, resonant light exciting the Rydberg condition through irradiation of laser beam and to the ion condition through application of electric field. CONSTITUTION:The beryllium vapor 10 is supplied to a vessel 1 from a gas discharge hole 1a. The RF discharge is generated by an induction coil 16, simultaneously a laser beam generating part oscillates and a voltage is applied to electrodes 5 and 6 in synchronization with laser oscillation. Electrons by RF discharge collide with the beryllium vapor 10, the laser beams B3-B5 cross at the ion producing space 4 within the vessel 1, the beryllium vapor 10 is resonant- excited step by step to the Rydberg condition, and finally the excited vapor is ionized by pulse field generated from a field generating part 15.

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
The purpose of this project is to provide an ion beam generator that can improve the ionization efficiency for input light energy by several orders of magnitude compared to conventional resonant optical excitation and ionization methods, and has excellent selectivity in selective ionization. There is.

[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 4
This is a method of irradiating beryllium vapor to be ionized with two laser beams Bl and B2 of 573 people, that is, beryllium atoms in the ground state 2s (Is) are first ionized into 2349
The first excited state fi2p (IP
O), then the 4573 laser beam B
2 to resonantly excite it to energy level 3d (1D), and further ionize it with the laser beam B2 of 4573 people.

The ionization method in the device of the present invention differs from the conventional ionization method described above in that only resonance excitation is used.
Beryllium vapor is transformed into a metastable state 2p (3P) by gas discharge.
O) is resonantly excited to a dominant state, and the laser beam, the first
In the example shown, the wavelength is 3321A, 1.46μ, 6449
Resonantly exciting the excited vapor from this excited state to the Rydberg state using three human laser beams B3 to B5,
Furthermore, unlike the conventional ionization method, beryllium vapor is not brought into a free electronic state, that is, an ion state, by a laser beam, B2 in the example of FIG. state.

E (V/cI11) =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 3d (ID) using a laser beam B2 with a wavelength of 4573. . Therefore, the output energy of the laser beam is small, and since the excitation is from a metastable state rather than the ground state, the wavelength of the photon is short, and since only resonance is used, 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 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;
3a and 3b are gas exhaust holes, respectively, and laser beams B3. This is a window through which B5 or B4 is introduced into the container 1, and the space in the container 1 where the laser beams B3 to B5 intersect is an ion generation space 4. The laser beam generating section includes a Franche lamp as an excitation source and three lasers that are excited by the Franche lamp and generate the laser beams B3 to B5, and these lasers include a wavelength tunable laser, a dye laser,
Solid state lasers or excimers such as free electron lasers and alexandrite lasers.

A gas laser such as nitrogen is used.

Reference numerals 5.6 and 5.6 are electrodes placed across the ion generation space 4; 5a and 6a are terminals that apply voltage to the electrodes 5.6; 15. Reference numeral 16 designates an induction coil which is also placed across the ion generation space 4, and which generates high frequency (RF) waves in the ion generation space 4.
) It serves as an RF discharge generating section that generates electric 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.

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
6 generates an RF discharge, and at the same time, the laser beam generator oscillates, and a voltage is applied to each of the electrodes 5 and 6 from the terminals 5a and 6a in temporal synchronization with the laser oscillation. Then, due to this, the above ground state 2S
Electrons from the RF discharge collide with the beryllium vapor 10 at (IS), and as a result, the beryllium vapor 10 is excited to a metastable state 2p (3PO). In addition, the oscillation of the above laser caused laser beam B3 for 3,321 people and 6,449 people.
B5 is introduced into the container 1 through the window 3a, and 1, 4
A laser beam B5 of 6μ is similarly introduced through the window 3b, and each beam B3-B5 enters the ion production space 4 in the container 1.
This causes the beryllium vapor 10 to enter the metastable state 2p (
3PO) to excited state i! "13s (3S) is resonantly excited, and further excited from the excited state 3S (3S) to excited state 3p (3P') by the 1° 46μ laser beam B4, and further excited to the Rydberg state 12d by the 6449 laser beam B5. (3D), and finally the excited vapor is ionized by a pulsed electric field from the electric field generator 15. Also, the electrode 6 and the sample stage 8
A DC voltage is applied between the ion beam 10 and the ion beam 9. As a result, the ionized beryllium vapor 10 is extracted as an ion beam 9 consisting only of beryllium ions, and the ion beam 9 is irradiated onto the sample 8.

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 it contains impurities other than beryllium, such as oxygen, nitrogen, carbon, hydrogen, etc., and even if the amount is greater than beryllium, the energy level and wavelength of the laser beam should not be made to match those of the above impurities, etc. 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 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 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 oven 13, and 14 is ionized beryllium vapor. 10 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.

Beryllium vapor 10 is generated by vaporization, and this vapor 10 is introduced into the container 1 through the gas introduction hole 1a. Then, an RF discharge is generated by the induction coil 16, and at the same time 33
21 people, 6449 people laser beam B3.85 is window 3
Through a, a laser beam B4 of 1,46μ is also applied to the window 3.
b into the container 1, and further an electrode 5.6
A voltage is applied to generate a pulsed electric field, which causes the vapor 10 to change from the ground state 2s (13) to the excited state 2p (3
PO), 3s (3S), and 3p (3P') are excited stepwise to the Rydberg state 12d (3D), and furthermore, the electrons of the beryllium vapor 10 in the Rydberg state 12d (3D) become free electrons, As a result, beryllium ions are generated in the ion generation space 4, and the beryllium ions are emitted as an ion beam 9 by the extraction electrode 14.

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

In the present invention, in order to excite elements stepwise, a plurality of laser beams each having a specific frequency are required, and the plurality of laser beams must be synchronized. Fig. 4 shows the synchronization method. This is an example.

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.

Furthermore, by simultaneously oscillating the excitation laser 21 and applying voltage to the electrode 5.6 and the induction coil 16, the laser beam, electric field, and RF 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 excited to a relatively lower excited state by gas discharge, and the substance to be ionized is resonated from the excited state to the Rydberg state by laser beam irradiation. Since the substance is photoexcited 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 phase diagram of a singlet system of beryllium neutral atoms, 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. A schematic configuration diagram of a focused ion beam generator according to an embodiment, FIG. 4 shows an ion beam generation according to a third embodiment of the present invention...Gas discharge generation section, 20...Laser beam generation section, B1 to B5 ...Laser beam. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 3 Figure 4

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 an electric field generator that applies an electric field to the substance in the container. and a gas discharge generation section that generates a gas discharge in the atmosphere of the substance in the container, the device generating an ion beam of the substance, wherein the gas discharge generation section energizes the substance by gas discharge. The laser beam generator generates a laser beam having a wavelength that resonantly excites the substance from the relatively lower excited state to the Rydberg state. The ion beam generating device is characterized in that 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 The patent claim is characterized in that a plurality of laser beams having different wavelengths are generated to resonantly excite the substance stepwise from the relatively lower excited state to the Rydberg state via the intermediate state. The range of the ion beam generator according to item 1. (3) The laser beam generating section includes an excimer, a gas laser such as nitrogen, or a dye laser excited by harmonics of the gas laser, or both. (4) The ion beam generator according to claim 1 or 2, characterized in that the ion beam generator is used. The ion beam generating device according to claim 1 or 2. (5) Claim 1 or 2, characterized in that a dye laser is used as the laser beam generating section.
The ion beam generator described in Section 1. (6) As the laser beam generating section, one or both of a solid-state laser such as an alexandrite laser and a dye laser excited by harmonics from the solid-state laser is used. The ion beam generator according to item 1 or 2. (7) The ion beam generating device according to claim 1 or 2, wherein a free electron laser is used as the laser beam generating section. (8) The laser beam generating section includes one excitation source,
3. The ion beam generator according to claim 1, comprising a plurality of mutually time-synchronized dye lasers excited by the excitation source. (9) The ion beam generator according to any one of claims 1 to 8, wherein the relatively lower excited state is a metastable state. α0) Ion beam generation according to any one of claims 1 to 9, 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. Device. (11) The gas discharge generating section generates a high frequency (R'F)
An ion beam generator according to any one of claims 1 to 10, characterized in that the ion beam generator generates a discharge. (12) 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 11, characterized in that: (13) Claims 1 to 12 are characterized in that the phases of at least any two of the laser beams, gas discharges, and electric fields can be temporally synchronized. 2. The ion beam generator according to any one of paragraphs. (14) The substance is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. ion beam generator.