JPS60208034A - Ion beam generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 Rydberg state (R
Our objective is to provide an ion beam generator that can improve the ionization efficiency with respect to the input hole 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, taking as an example the case of generating a magnesium ion beam. FIG. 1 is an energy level diagram of a neutral magnesium atom.

Conventional ionization methods, for example, have wavelengths of 2853 and 555
This is a method of irradiating the magnesium vapor to be ionized with two laser beams Bl and B2 of 28 people, that is, the magnesium atoms in the ground state 3s (Is) are first ionized into 285
The first excited state 3p (IP
O), then the 5528 laser beam B
2 to resonantly excite it to energy level 3d (I D), and further ionize it with the laser beam B1 of 2853.

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.
For example, when the Rydberg state 13d (ID) that can be ionized by the Stark effect from p(IP') is
Nine people are resonantly excited by the laser beam B3, and furthermore, an electric field expressed by the following formula is applied to the excited vapor by the laser beam B3.
3, ionization is performed from this excited state by the Stark effect.

E (V/am) -0,3125X109 ・n-4
Here, n is the effective principal view number of the Rydberg state.

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 and electric field strength of the laser beam mentioned above, ion beams of other types of substances can be easily generated. You can leave it there. 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 invention. In the figure, I
is a container into which the substance to be ionized is introduced, la is a gas introduction hole for introducing the substance into the container 1, lb
3a and 3b are windows for introducing the laser beams Bl and B3 from a laser beam generating section (not shown) into the container 1, and the laser beams Bl and B3 in the container 1 are
The space where these intersect is the ion generation space 4. The laser beam generation section is provided with two lasers (not shown) such as a wavelength tunable laser or a free electron laser, and a pulse generation circuit that generates an electric signal pulse that triggers the oscillation of each laser. ing.

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
The electric field generating section 15 pulses the ionizing electric field using an operation signal that can be synchronized in time with the pulse signal of the pulse generating circuit.

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 1o is introduced into the container 1 through the gas introduction hole 1a.

In the laser beam generating section, a trigger pulse is applied to each laser from the pulse generating circuit. Then, each laser oscillates and the wavelength is 2853 people's laser beam B
1 is introduced into the container 1 through the window 3a, and 385
Nine laser beams B3 are similarly introduced through the window 3b, and both beams Bl and B3 enter the ion generation space 4 in the container 1.
, thereby intersecting the magnesium vapor 1o
is the ground state 3s by the laser beam Bl of 2853 people
('S) to the first excited state 3p (IPO), and then from the first excited state 3p (IPO) to the Rydberg state 13 by the laser beam B3 of 3859 people.
It is resonantly excited stepwise to d(ID). 1. In addition, a voltage is applied to each of the electrodes 5 and 6 through the terminals 5a and 6a in time synchronization with the laser oscillation, thereby creating an electric field in the magnesium vapor 1o in the Rydberg-like IW 13d (ID). As a result, the magnesium vapor 1o 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 volume Bl, in this case, Even if it contains impurities other than magnesium, such as oxygen, nitrogen, carbon, hydrogen, etc., and even if the amount is greater than magnesium, the energy level of the laser beam will change.

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 is performed by resonant optical excitation. As a result, the temperature of the target sample 8 to be irradiated with the ion beam, such as a substrate in the case of a semiconductor, does not increase (low-temperature processing can be performed).

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. 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 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. The laser beam Bl of 2,853 people and the laser beam B3 of 3,859 people are introduced into the container 1 through the windows 3a and 3b and irradiated on the vapor 10, and at the same time, a voltage is applied to the electrodes 5 and 6. An electric field is applied to the vapor 10. This causes the vapor 10 to change from the ground state 3s (Is) to the first excited state 3.
Rydberg state 13d (ID) via p (IPO)
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 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 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 FIG. 4 shows an example of a synchronization method.

This laser oscillation device 20 includes three lasers 2 with different wavelengths.
2, 23, and 24, and one trigger generator 21 that provides each of the lasers 22 to 24 with an electric signal pulse serving as a trigger for laser oscillation. In this way, each laser 2
2 to 24 are configured to be oscillated by a trigger pulse from one trigger generator 21, the oscillating laser beam ω1. ω2. ω3 becomes temporally synchronized. By simultaneously generating pulses from the trigger generator 21 and applying voltage to the electrodes 5 and 6, the laser beam and the electric field can be synchronized in time.

FIG. 5 shows a configuration example of a laser oscillation device of an ion beam generator according to a fourth embodiment of the present invention.
Reference numerals 5 to 27 are laser heads of solid-state lasers, 28 is a flash lamp power supply, and 29 is a Q-switch Ponkel cell power supply, and the power supplies 28 and 29 serve as a trigger arm 30 for triggering each of the lasers 25 to 27. In this example,
Each laser head 25 to 27 is connected to one set of power supplies zs and 29.
Since the oscillating laser beams ω1 to ω3
are temporally synchronized.

〔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 Niedberg state by irradiation with a laser beam, and the substance is further ionized by applying an electric field. Since the excited state is changed to the ion state, 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 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, 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, and FIG. 5 is a diagram of a fourth embodiment of the present invention. FIG. 2 is a block diagram of a laser beam oscillator of an ion beam generator according to an example. DESCRIPTION OF SYMBOLS 1... Container, 15... Electric field generation part, 20... Laser beam generation part, 21.30... Trigger means, B1~
B3...Laser beam. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1! Figure 3 Figure 4 Figure 5 Procedural amendment (voluntary) 3. Person making the amendment 5. Detailed explanation of the invention in the specification subject to amendment 6. Contents of the amendment (11 Specification page 4, No. 19) Row rRydberg 1e
vel" is corrected to rRydberg 5tate J. (2) In the first line of page 6, “Karastarck” was changed to “kara,”
Stark”. (3) Correct "electrode J in synchronization" on page 9, line 15 of the same page to "electrode J synchronized and with a delay of about 1 μsec". Corrected to "electrode after some delay."

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. In the apparatus for generating an ion beam of the substance, the laser beam generating unit includes a trigger means for generating an electric signal to trigger laser oscillation, and a device for generating an ion beam of the substance from the ground energy level to the Rydberg state. and a laser that generates a laser beam having a wavelength that causes resonant optical excitation in An ion beam generator characterized by: (2) The laser beam generator 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. The ion beam generator according to claim 1, characterized in that the ion beams are generated in time synchronization with each other by one trigger pulse from the trigger means. An ion beam generation device according to claim 1 or 2, characterized in that a variable laser is used. (4) A patent characterized in that a free electron laser is used as the laser beam generation section. The ion beam generator according to claim 1 or 2. (5) The electric field also serves as an extraction electric field for extracting the ionized substance as an ion beam. The ion beam generator according to any one of items 1 to 4. (6) The electric field generating section pulses the electric field using an operation signal that can be synchronized in time with the pulse signal of the pulse generating circuit. The ion beam generator according to any one of claims 1 to 5. (7) The trigger means of the laser beam generator includes one trigger for each of the plurality of lasers. Claim 2, characterized in that it is a trigger pulse generator that provides a trigger pulse.
The ion beam generator described in Section 1. (8) Ion beam generation according to claim 2, characterized in that the trigger means of the laser beam generation section comprises one flash lamp power source and one Bockel cell power source for driving a plurality of laser heads. Device. (91) The ions according to any one of claims 1 to 8, wherein the substance is introduced into the container as a vapor generated by heating and vaporizing a solid or liquid substance. Beam generator.