JPS6217932A - Ion source - Google Patents

Abstract

PURPOSE:To obtain an ion source applicable onto super high brightness ion beam by leading the weakly ionized gas produced from weakly ionized gas producing means through a nozzle of barrier board into the vacuum chamber then expanding freely with supersonic speed while arranging plural take-out electrodes having plural holes at the low gas temperature area of said freely expanded flow to take out the ion flow. CONSTITUTION:Ion source has a discharge chamber 1 as means for producing weakly ionized gas. The discharge chamber 1 is provided with a cathode 3, an intermediate electrode 4 and an anode 5. The intermediate electrode 4 is provided with an intermediate electrode hole 6 while the anode 5 is provided with a nozzle 8 projecting into the vacuum chamber 2. Take-out electrodes 11a, 11b are arranged at the positions separated sufficiently from the anode 5 while having plural take-out electrode holes 12a, 12b respectively. Metal plate formed with plural take-out electrode holes 12a, 12b or metal mesh may be employed as the take-out electrodes 11a, 11b. In order to expand the weakly ionized gas produced from the discharge chamber freely with supersonic speed, the take-out electrodes are separated sufficiently from the anode while in order to take out ions from weakly ionized freely expanded gas flow having lowered gas temperature, the take-out electrode is constructed with plural electrodes to apply electrical field between them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to ion sources, particularly ion implantation, ion beam exposure, and ion beam exposure in the field of semiconductor device manufacturing processes.
The present invention relates to a high-intensity ion beam gas ion source used for microfabrication such as ion beam deposition, ion beam etching, or ion beam 1liiii.

[Prior Art] Conventionally, there is a device of this type as shown in FIG. 3 published in Illi Tatsuji et al.: Ion Implantation (Shokodo, 1976).

First, the configuration of the conventional ion source shown in FIG. 3 will be explained. In FIG. 3, a conventional ion source includes a discharge chamber 1 and a vacuum chamber 2. In FIG. The discharge chamber 1 includes a cathode 3, an intermediate electrode 4, and l! ! The intermediate electrode 4 and the anode 5 are provided with an intermediate electrode hole 6 and an anode hole 7, respectively. Also,
The discharge chamber 1 includes a carrier gas inlet 9 for introducing carrier gas between the cathode 3 and the intermediate electrode 4, and a sample gas inlet 9 for introducing the sample gas between the intermediate electrode 4 and the III electrode 5. An introduction 010 is provided.

The vacuum chamber 2 is separated from the discharge chamber 1 by an anode 5 and communicates with the discharge chamber 1 by an anode hole 7.

The vacuum chamber 2 is provided with a vacuum outlet 13 for evacuation and an extraction electrode 11 close to the anode 5 . The extraction electrode 11 is provided with an extraction electrode hole 12 for extracting ions.

Next, the operation of the conventional ion source will be explained.

First, the discharge chamber 1 and the vacuum chamber 2 are evacuated to a predetermined degree of vacuum by evacuation from the vacuum port 13. Subsequently, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 9, and a DC voltage is applied between the cathode 3 and the intermediate electrode 4. Then, the carrier gas is ionized by glow emission or arc discharge generated between the cathode 3 and the intermediate electrode 4, and plasma is generated.

The generated plasma passes through the intermediate electrode hole 6 and flows between the intermediate M electrode 4 and the anode 5. Here, when the sample gas is introduced into the discharge chamber 1 through the sample gas inlet 10, the plasma of the carrier gas collides with the introduced sample gas, thereby ionizing the sample gas. The ionized sample gas passes through the anode hole 7 and flows between and covers the anode 5 and extraction electrode 11 . Since a direct current voltage is applied between the anode 5 and the extraction electrode 11 and an electric field is generated, an ion flow is extracted from the extraction electrode hole 12 in the direction shown by arrow C in FIG. 3 due to this electric field. At this time, unionized neutral gas flows into the vacuum chamber 2 together with the ion flow in the form of a molecular beam.

[Problems to be Solved by the Invention] In conventional ion sources, as described above, the ion extraction electrode is provided close to the anode, and ions are extracted from the generated high-temperature plasma. The temperature of the stream was high and the random motion of the ions was large. This large random motion remains even in the ion beam obtained by accelerating the ion flow, so there is a limit to the diameter that can be focused using an electromagnetic field. It was impossible to apply it to ion beams.

By the way, as an ion source for ultra-high H-degree ion beams for gas atoms or gas molecules, field emission of ions from a layer of gas atoms and molecules solidified on a metal surface cooled with liquid nitrogen or liquid helium has been used so far. and
Although the temperature of the extracted ion stream is low and the random motion of the ions is small, there are problems such as the ion flow rate is significantly lower than that of a gas ion source and the device is complicated.

Therefore, the present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain an ion source that can be applied to ultra-high-intensity ion beams such as focused ion beams.

[Means for Solving the Problems] The ion source according to the present invention generates a weakly ionized gas using a weakly ionized gas generating means, and introduces this into a vacuum chamber through one nozzle provided on a partition plate. , supersonic free expansion is performed in a vacuum chamber to generate a supersonic free expansion flow, and in the region where the gas temperature has decreased in this supersonic free expansion flow,
A plurality of extraction N poles each having a plurality of holes are provided, and an electric field is generated between the extraction electrodes by an electric field generating means to extract ions whose temperature has decreased.

[Function] In this invention, the plurality of extraction electrodes installed in the supersonic free expansion flow region where the gas temperature has decreased is such that the temperature of free particles such as neutral atoms, molecules, and ions is at an absolute temperature of 20 to several degrees. Since ions are extracted from a plasma flow that has been reduced to a low temperature, the temperature of the extracted ion flow is low and the random motion of the ions is small. Therefore, this ion source can be applied to ultra-high brightness ion beams such as focused ion beams.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a diagram schematically showing an ion source according to an embodiment of the present invention.

First, the general configuration of this ion source will be explained. This ion source includes a discharge chamber 1 as a weakly ionized gas generating means. A cathode 3, an intermediate electrode 4, and an anode 5 are provided in the discharge chamber 1. The intermediate electrode 4 is provided with an intermediate electrode hole 6, and the anode 5 is provided with a nozzle 8 that projects into the vacuum chamber 2. Further, the extraction electrodes 11a and 1 are placed at a position sufficiently away from the anode 5.
1b, and each extraction electrode is provided with a plurality of extraction electrode holes 12a and 12b, respectively.

A DC voltage is applied to the extraction electrodes 11a and 11b from a DC voltage generation source (not shown), and an electric field is generated between these electrodes. The extraction electrode is not limited to the one consisting of two extraction electrodes 11a and 11b as shown in FIG. Good too. Further, the extraction electrode 11a,
11b may be a metal plate in which a plurality of extraction electrode holes 12a, 12b are formed, or a metal net may be used instead.

The vacuum chamber 2 including the extraction electrodes 11a and 11b is in contact with the discharge chamber 1 via the anode 5, and communicates with the discharge chamber 1 through the nozzle hole 7. That is, the anode 5 functions as a partition separating the discharge chamber 1 and the vacuum chamber 2, and the nozzle hole 7 functions as a partition between the discharge chamber 1 and the vacuum chamber 2.
The weak NM gas generated is guided into the vacuum chamber 2. The shape of this nozzle hole 7 may be circular, square, or rectangular.

Further, the discharge chamber 1 is provided with a carrier gas inlet 9 and a sample gas inlet 10, as in the conventional ion source shown in FIG. 3, and the vacuum chamber 2 is provided with a vacuum outlet 13.

By the way, conventional ion sources are also equipped with a vacuum chamber similar to the vacuum chamber 2 shown in FIG. 1, but in the conventional ion source shown in FIG. Therefore, the space between the extraction electrode and the anode is filled with gas flowing in from the discharge chamber, so that the weak Nwi gas does not form a supersonic free expansion flow in the vacuum chamber. Therefore, in this invention, in order to cause the weakly ionized gas obtained in the discharge chamber to undergo supersonic free expansion in the vacuum chamber, the extraction electrode is provided at a sufficient distance from the anode, and ions are generated from the supersonic free expansion flow with a reduced gas temperature. In order to extract this, the extraction electrode is made up of multiple electrodes and an electric field is applied between them.

Next, the specific operation of the ion source shown in FIG. 1 will be explained in detail.

After a predetermined degree of vacuum is achieved, carrier gas is introduced into the N-released seedlings 1 from the carrier gas inlet 9.

For example, argon gas is used as the carrier gas. Here, when a DC voltage is applied between the cathode 3 and the intermediate electrode 4, glow discharge or arc discharge occurs between these electrodes, the carrier gas is ionized, and plasma is generated. This plasma passes through the intermediate electrode hole 6 and flows between the intermediate electrode 4 and the anode 5. The inflowing plasma ionizes the sample gas introduced from the sample gas inlet 10.

The sample gas introduced here is, for example, sodium vapor. The plasma of carrier gas and sample gas is transmitted through nozzle hole 7.
, flows into the vacuum chamber 2, and freely expands at supersonic speed. In FIG. 1, arrow A indicates the flow of supersonic free expanding plasma.

The region where this supersonic free expansion flow exists is called the quiet region (zo
This quiet region 14 is called a barrel-shaped shock wave.
ck) 15 and Matsuha circle W (Mach Disk)
) 17. Further, a jet boundary 16 is formed outside the quiet region 14 in proximity to the barrel-shaped ** wave 15, and
'7 Reflected shock wave downstream of disk 17
ed 5hock>18 is formed. The Matsuha disk 17 and reflected shock wave 18 shown in FIG.
This shows an ideal shape when the influence of the presence of a and 11b can be ignored; in reality, the shape is disturbed by the extraction electrode.

The shape and size of the above-mentioned quiet region 14 are influenced by the shape and size of the nozzle hole 7. In this invention, the nozzle 8 is provided on the anode 5, which is a diaphragm, because the quiet region 14 obtained is long and narrow, and the degree of expansion is small, but a large gas density can be obtained, compared to the case where holes are simply provided. be.

In the quiet region 14, the plasma undergoes adiabatic expansion and the density of the plasma decreases as it moves downstream.

The temperature and the frequency of collisions between particles decrease and the M separation freezes, but conversely the flow velocity of the plasma increases. The plasma density due to adiabatic expansion is 1 of the plasma density in the discharge chamber 1, /
1000), and the temperature becomes about 1/100 of the plasma temperature in discharge v1.

Therefore, when the plasma in the discharge chamber 1 is generated by a flat-shaped glow discharge or an arc discharge, the temperature due to adiabatic expansion is 2000 to 1,000 yen (absolute temperature) for electrons.
Although it remains at 00 degrees, the temperature decreases to 20 to several degrees for free particles such as neutral atoms, molecules, and ions.

Since the above-mentioned Matsuha disk 17 is a shock wave, the gas concentration increases downstream of the Matsuha disk 17. Therefore, since the gas temperature in the quiet region 14 is lowest immediately in front of the Matsuha disk 17, ion extraction must be performed in this region, and preferably one extraction electrode 11a is placed in front of the Matsuha disk 17, for example. 10-2oIII) DII equipment.

By the way, when the supersonic free expansion flow in the quiet region 14 collides with the extraction electrode 11a, a shock wave is formed, and the gas temperature rises downstream of the shock wave. therefore.

In order to prevent a rise in gas temperature, it is preferable that the extraction electrode has a shape that does not generate shock waves as much as possible. FIG. 2 is an enlarged view showing an example of such an extraction electrode. In FIG. 2, the extraction electrode 11a has a tip portion 11c that protrudes in the direction of the supersonic free expansion flow indicated by the arrow. Since the supersonic free expansion flow A collides with the tip portion 11c, the generated shock wave 19 is weak.

Since a DC voltage is applied to the extraction electrodes 11a and 11b, an electric field is generated between the extraction electrodes 11a and 11b. Here, ions move in the vector direction of the electric field, and electrons move in the opposite vector direction of the electric field.

This causes the ion flow to move along the vector direction of the electric field.
It is pulled out from the extraction electrode hole 12b. The ion flow drawn out by the electric field is indicated by arrow B in FIG. Extraction electrode 1
A plurality of extraction electrode holes 12 are provided in each of 1a and 11b.
a and 121), ions can be extracted efficiently. The resulting ion stream has low temperature and low random motion.

In addition, in the above embodiment, the case where the plasma in the discharge chamber 1 is generated by glow discharge or arc discharge was explained, but the plasma in the discharge chamber 1 can be generated by electrodeless ionization such as RF discharge discharge electron impact ionization or laser-induced ionization. The plasma may also be generated by electric discharge, and the same effects as in the above-described embodiments can be obtained with such plasma.

[Effects of the Invention] As described above, according to the present invention, a single partition plate provided between a discharge chamber and a vacuum chamber has a plurality of extraction electrodes each having a plurality of holes formed therein. It is installed in a region where the gas concentration of the supersonic free expansion flow of plasma that is formed in the vacuum chamber via the nozzle is reduced, and is configured to extract ions from the supersonic free expansion flow of plasma, so that the ion flow with a low temperature can be achieved. That is, it is possible to efficiently extract an ion flow with small random motion and high ion density.

Therefore, the ion source of the present invention can be applied to ultra-high brightness ion beams such as focused ion beams.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an ion source according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of an extraction electrode used in an ion source according to an embodiment of the present invention. FIG. 3 is a diagram showing a conventional ion source. In the figure, 1 is a discharge chamber, 2 is a vacuum chamber, 5 is positive, 7 is a nozzle hole, 8 is a nozzle, 11a and 11b are extraction electrodes, 12a and 12b are extraction electrode holes, 13 is a vacuum outlet,
14 indicates a quiet area. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masu Oiwa Okokokokod -IR'J- Takoyoshi Diagram 3 Procedural Amendment (Voluntary) 6152B Showa Year/Monday [1 1, Indication of Case Patent Application No. 156567/1988 2,
Name of the invention ion source 3, person making the amendment 5, claims column of the specification to be amended, detailed explanation column of the invention, and brief explanation column of drawings. 6. Details of the amendments are as shown in the attached sheet. (There is no change in the content other than the matters stated in the column subject to amendment) ↓Suite Description 1, Name of the invention ion source 2, Claims (1) Partial ionization of gas atoms or gas molecules a weakly ionized gas generating means for generating a weakly ionized gas; a vacuum chamber for freely expanding the weakly ionized gas generated by the weakly ionized gas generating means at a supersonic speed; and the weakly ionized gas generating means and the vacuum chamber. a partition plate formed with one nozzle for separating the weakly ionized gas generated by the weakly ionized gas generating means into the vacuum chamber; and a region within the vacuum chamber that freely expands at supersonic speed. This results in a decrease in gas temperature! - A plurality of extraction electrodes provided in an electric gas supersonic free expansion flow region, each having a plurality of holes, and an electric field generating means for generating an electric field between the plurality of extraction electrodes. , an ion source characterized by extracting ions from a supersonic free expansion flow of a weakly ionized gas with a reduced gas temperature. (2) The ion source according to claim 1, wherein the weakly ionized gas generating means uses glow discharge, arc discharge, RF discharge discharge electron impact ionization, or 1. L laser induced ionization. (3) The ion source according to item 1 or 2, characterized in that one nozzle provided on the partition plate has a circular cross section. (4) The ion source according to claim 1 or 2, wherein one nozzle provided on the partition plate has a square or rectangular cross section. (5) The ion source according to any one of claims 1 to 4, characterized in that it is constituted by the plurality of extraction electrode retaining metal nets. 3. Detailed description of the invention [Industrial Field of Application] This invention relates to an ion source, and in particular, to ion implantation, ion beam exposure, and ion beam exposure in the field of semiconductor device manufacturing processes.
The present invention relates to a high-intensity ion beam gas ion source used for microfabrication such as ion beam deposition, ion beam etching, or ion beam writing. [Prior art] Conventionally, this type of device has been used, for example, by Kouji Ito et al., Ion Implantation (Shokodo, 1976).
There is something shown in Figure 3 published in . First, the configuration of the conventional ion source shown in FIG. 3 will be explained. In FIG. 3, a conventional ion source includes a discharge chamber 1 and a vacuum chamber 2. In FIG. A cathode 3 and an intermediate electrode 4 are placed in the discharge chamber 1.
and an anode 5 are provided, and the intermediate electrode 4 and the anode 5 are provided with an intermediate electrode hole 6 and an anode hole 7, respectively. The discharge chamber 1 also includes a carrier gas inlet 9 for introducing carrier gas between the cathode 3 and the intermediate electrode 4, and a carrier gas inlet 9 for introducing carrier gas between the cathode 3 and the intermediate electrode 4.
A sample gas inlet 10 for introducing sample gas is provided between the anode 5 and the anode 5 . The vacuum chamber 2 is separated from the discharge chamber 1 by an anode 5 and communicates with the discharge chamber 1 through an anode hole 7 . The vacuum chamber 2 has a vacuum inlet 13 for evacuation and a positive ff1.
An extraction electrode 11 is provided adjacent to the electrode 5 . Output power t!
An extraction electrode hole 12 for extracting ions is provided in i11. Next, the operation of the conventional ion source will be explained. First, the discharge chamber 1 and the vacuum chamber 2 are evacuated to a predetermined degree of vacuum by evacuation from the vacuum port 13. Subsequently, while evacuating from the vacuum port 13, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 9, and a DC voltage is applied to el of the cathode 3 and intermediate electrode 4. Then, the carrier gas is ionized by glow discharge or arc discharge generated between the cathode 3 and the intermediate electrode 4, and plasma is generated. The generated plasma passes through the intermediate electrode hole 6 and is connected to the intermediate electrode a.
It flows between li4 and 11 pole 5. Here, when the sample gas is introduced into the discharge chamber 1 through the sample gas inlet 10, the sample gas is ionized by interaction with the carrier gas plasma. The carrier gas plasma containing the ionized sample gas passes through the 11-pole hole 7 and flows between the III pole 5 and the lead-out N pole 11 . Since a direct current voltage is applied between the anode 5 and the extraction electrode 11 and an electric field is generated, an ion flow is extracted from the extraction electrode hole 12 in the direction shown by arrow C in FIG. 3 due to this electric field. At this time, unionized neutral gas flows into the vacuum chamber 2 together with the ion flow in the form of a molecular beam. [Problems to be Solved by the Invention] In the conventional gas ion source, the ion extraction W1 pole is provided close to the discharge chamber as described above, and the ion extraction W1 pole is provided close to the discharge chamber to extract ions from the generated high-temperature plasma. The temperature of the ion stream was high and the random motion of the ions was large. This large random motion remains even in ion beams obtained by accelerating the ion flow, so there is a limit to the diameter that can be focused using an electromagnetic field. It was impossible to apply it to high-intensity ion beams. By the way, as an ion source for ultra-high-intensity ion beams related to gas atoms or molecules, up until now, the field emission of ions from a layer of gas atoms and molecules solidified on a metal surface cooled with liquid nitrogen or liquid helium has been used. Ori,
Although the temperature of the extracted ion stream is low and the random motion of the ions is small, there are problems such as the ion stream m is significantly smaller than that of a gas ion source and the device is complicated. Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a gas ion source that can be applied to ultra-high-intensity ion beams such as focused ion beams. Means for Solving Problem E] The ion source according to the present invention generates a weakly ionized gas by a weakly ionized gas generating means, and generates a weakly ionized gas by the ion source provided in the partition plate.
Introduced into a vacuum chamber through two nozzles and allowed to freely expand at supersonic speed in the vacuum chamber to form a weak 11111 gas supersonic free expanding flow, and in a region where the gas temperature has decreased in this weakly ionized gas supersonic free expanding flow, A plurality of extraction electrodes each having a plurality of holes are provided, and an electric field is generated between the extraction electrodes by an electric field generating means, so that the ion flow with a reduced temperature is not extracted. [Function] In this invention, the plurality of extraction electrodes installed in the weakly ionized gas supersonic free expansion flow region where the gas temperature has decreased is such that the temperature of heavy particles such as neutral atoms/molecules and ions is at an absolute temperature of 20 to
Since ions are extracted from a plasma stream whose temperature has dropped to several degrees, the temperature of the extracted ion stream is low and the random motion of the ions is small. Therefore, this gas ion source can be applied to ultra-bright ion beams such as focused ion beams. [Example] Hereinafter, an example of the present invention will be explained with reference to the drawings. 1st
The figure is a diagram schematically showing an ion source according to an embodiment of the present invention. First, the general configuration of this ion source will be explained. This ion source includes a discharge chamber 1 as a weakly ionized gas generating means. The discharge chamber 1 includes a negative electrode 4i[i3, an intermediate electrode 4, and an anode 5].
and is provided. The intermediate electrode 4 is provided with an intermediate electrode hole 6, and the anode 5 is provided with a nozzle 8 that projects into the vacuum chamber 2. Further, an extraction electrode 11a is placed at a position sufficiently away from the anode 5.
and 11b are provided, and each extraction electrode is provided with a plurality of extraction electrode holes 12a and 12b, respectively. A DC voltage is applied to the extraction electrodes 11a and 11b from a DC voltage generation source (not shown), and an electric field is generated between these electrodes. The extraction electrodes are two extraction electrodes 118 as shown in FIG. The extraction electrode is not limited to one composed of llb, but may be composed of a large number of electrodes, and an electric field may be generated between the electrodes. In addition, the extraction electrode 118.
11b may be a metal plate in which a plurality of extraction electrode holes 12a, 12b are formed, or a metal net may be used instead. The vacuum chamber 2 including the extraction electrodes 11a and 11b is in contact with the discharge chamber 1 via the anode 5, and communicates with the discharge chamber 1 through the nozzle hole 7. That is, l! The I pole 5 functions as a partition separating the discharge chamber 1 and the vacuum chamber 2, and the nozzle hole 7
It functions as a partition hole that guides the weakly ionized gas generated in the i-chamber 1 into the vacuum chamber 2. The cross-sectional shape of the nozzle 8 may be circular, square, or rectangular. Further, the discharge chamber 1 is provided with a carrier gas inlet 9 and a sample gas inlet 10, as in the conventional ion source shown in FIG. 3, and the vacuum chamber 2 is provided with a vacuum outlet 13. By the way, a vacuum chamber similar to the vacuum chamber 2 shown in FIG.
Although a conventional ion source is also provided, the conventional ion source shown in FIG. Since the electrode is placed close to the anode, which is a diaphragm, the space between the extraction electrode and the anode is filled with weakly ionized gas flowing from the discharge chamber, and the weakly ionized gas causes a supersonic free expansion flow in the vacuum chamber. It cannot be formed. Therefore, in this invention, in order to allow the weak 1 iM gas obtained in the discharge IN chamber to freely expand at supersonic speed in the vacuum chamber, the extraction electrode is provided sufficiently away from the anode, and the weakly ionized gas with a reduced gas temperature is allowed to freely expand at supersonic speed. To extract ions from the expanding flow, extraction electrodes are connected to multiple i! It consists of poles and an electric field is applied between them. Next, the specific operation of the ion source shown in FIG. 1 will be explained in detail. After the discharge chamber 1 and the vacuum chamber 2 are brought to a predetermined degree of vacuum, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 9 while performing evacuation. For example, argon gas is used as the carrier gas. Here, when a DC voltage is applied between the cathode 3 and the intermediate electrode 4, glow discharge or arc discharge occurs between these electrodes, the carrier gas is ionized, and plasma is generated. This plasma passes through the intermediate electrode hole 6 and
and the anode 5. The inflowing plasma ionizes the sample gas introduced from the sample gas inlet 10h). The sample gas introduced here is, for example, sodium vapor. The carrier gas and sample gas plasmas pass through the nozzle 8, flow into the vacuum chamber 2, and undergo free supersonic expansion. In Figure 1, arrow A indicates the flow of supersonic freely expanding plasma.
Indicated by This region of supersonic free expansion flow is called the quiet region (Zone o
f S lence), but this quiet area 1
4 is barrel-shaped shock wave (3arrel 5hock) 15
This is the area surrounded by the Mach D lsk 17 and the Mach D lsk 17. In addition, there is one outside of the quiet area 14.
There is a jet boundary (J et
BoundarV) 16 is formed, and a reflected shock wave (Ref'1ected) is formed downstream of the Matsuha disk 17.
5hock) 18 is formed. The Samach disk 17 and frontage J shock wave 18 shown in FIG.
This figure shows an ideal shape in the case where the influence of the presence of 11b and 11b can be ignored, and in reality it is disturbed by the extraction electrode. The shape and size of the above-mentioned quiet region 14 depend on the gas pressure in the discharge chamber 1, the length and cross-sectional shape and thickness of the nozzle 8,
as well as the pressure within the vacuum chamber 2. With this invention,
The reason why the nozzle 8 is provided on the anode 5, which is a partition plate, is that the quiet area 14 obtained is longer and narrower than when simply providing holes.
This is because although the degree of expansion is small, a large gas density can be obtained. In the quiet region 14, the plasma undergoes adiabatic expansion and the density of the plasma decreases as it moves downstream. The temperature and interparticle 11i burst frequency decrease and the degree of ionization freezes, but the plasma flow rate increases. The plasma density due to adiabatic expansion is 1/100 of the plasma density in the discharge chamber 1.
The temperature of the plasma decreases to about 0, and the temperature of the plasma becomes about 1/100 of the plasma temperature in the discharge chamber 1. Therefore, if the plasma in the spread 1 is generated by a typical glow discharge or arc discharge, the plasma concentration due to adiabatic expansion will remain at an absolute temperature of 2000 to 1000 degrees for electrons, but it will contain neutral atoms and molecules. For heavy particles such as ions, the temperature decreases to 20 to several degrees. Since the above-mentioned Matsuha disk 17 is a shock wave, the gas temperature increases downstream of the Matsuha disk 17. Therefore, since the gas temperature in the quiet region 14 is lowest immediately in front of the Matsuha disk 17, ion extraction must be performed in this region, and one extraction electrode 11a is placed, for example, 10 to 20 meters in front of the Matsuha disk 17. Install in a remote location. By the way, when the supersonic free expansion flow in the quiet region 14 is struck by an extraction electric charge, it generally forms a shock wave,
Downstream, the gas temperature increases. Therefore, in order to prevent the gas temperature from rising, it is preferable that the extraction electrode be shaped so that it does not generate shock waves as much as possible. FIG. 2 is an enlarged view showing an example of such an extraction electrode. In FIG. 2, the extraction electrode 11a has a tip portion 11c that projects in the direction of supersonic free expansion flow indicated by arrow A. The supersonic free expansion flow A collides with the tip 11c, and a shock wave 1 is generated.
9 is weak. Since a DC voltage is applied to the extraction electrodes 11a and 11b, an electric field is generated between the extraction electrodes 118 and 11b. Here, ions move in the direction of the electric field vector, and electrons move in the opposite direction of the electric field vector. This causes the ion flow to move along the vector direction of the electric field.
It is pulled out from the extraction electrode hole 12b. The ion flow drawn out by the electric field is indicated by arrow B in FIG. Extraction electrode 1
A plurality of extraction electrode holes 12 are provided in each of 1a and 11b.
a and 121) are provided, ions can be extracted efficiently. The resulting ion flow has a low temperature, which means that the random motion of the ions is small. In the above embodiment, the case where the plasma in the discharge chamber 1 is generated by glow discharge or arc discharge was explained, but the plasma in the discharge chamber 1 can be generated by electrodeless ionization such as RF discharge discharge electron impact ionization or laser-induced ionization. The plasma may also be generated by electric discharge, and the same effects as in the above-described embodiments can be obtained with such plasma. [Effects of the Invention] As described above, according to the present invention, a single partition plate provided between a discharge chamber and a vacuum chamber has a plurality of extraction electrodes each having a plurality of holes formed therein. It is installed in a region where the gas temperature of the supersonic free expansion flow of plasma that is formed in the vacuum chamber via the nozzle is low, and is configured to extract ions from the supersonic free expansion flow of plasma. An ion flow with small random motion and high density can be efficiently extracted. therefore,
The gas ion source of the present invention can be applied to ultra-high brightness ion beams such as focused ion beams. 4. Brief Description of the Drawings FIG. 1 is a diagram showing a schematic configuration of an ion source according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of an extraction electrode used in an ion source according to an embodiment of the present invention. FIG. 3 is a diagram without a conventional ion source. In the figure, 1 is a discharge chamber, 2 is a vacuum chamber, 5 is an anode, 7 is a nozzle hole, 8 is a nozzle, 11a and 11b are extraction electrodes, 12a and 12b are extraction electrode holes, 13 is a vacuum outlet, and 14 is a This shows the quiet region of supersonic free expanding flow. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (5)

[Claims] (1) Weakly ionized gas generating means for partially ionizing gas atoms or gas molecules to generate weakly ionized gas, and a vacuum chamber for supersonic free expansion of the weakly ionized gas generated by the weakly ionized gas generating means. and a partition plate that separates the weakly ionized gas generating means from the vacuum chamber and is formed with one nozzle for introducing the weakly ionized gas generated by the weakly ionized gas generating means into the vacuum chamber; A plurality of holes are provided in a region inside the vacuum chamber where a supersonic free expansion flow with a reduced gas temperature obtained by supersonic free expansion exists, and each has a plurality of holes. An ion source comprising: an extraction electrode; and an electric field generating means for generating an electric field between the plurality of extraction electrodes, and extracting ions from a supersonic free expansion flow with a reduced gas temperature. (2) The ion source according to claim 1, wherein the weakly ionized gas generating means uses glow discharge, arc discharge, RF discharge, electron impact ionization, or laser-induced ionization. (3) The ion source according to claim 1 or 2, wherein one nozzle provided in the partition plate has a circular hole. (4) The ion source according to claim 1 or 2, wherein one nozzle provided in the partition plate has a square or rectangular hole. (5) The ion source according to any one of claims 1 to 4, wherein the plurality of extraction electrodes are formed of a metal mesh.