JPS6217934A - Ion source - Google Patents

Abstract

PURPOSE:To obtain a gas ion source applicable onto super high brightness ion beam by leading the weakly ionized gas produced from weakly ionized gas producing means through a hole of barrier board into first vacuum chamber then expanding freely with supersonic speed while arranging the take-out electrodes having plural holes at low gas temperature area of said freely expanded flow and taking out the ion flow into second vacuum chamber. CONSTITUTION:Ion source is provided with disharge chamber 1 and vacuum chambers 2, 3. The vacuum chamber 2 is maintained at higher vacuum than the discharge chamber 1 while the vacuum chamber 3 is maintained at higher vacuum than the vacuum chamber 2. The discharge chamber 1 is provided with a cathode 4, an intermediate electrode 5 and an anode 6. The intermediate electrode 5 is provided with an intermediate electrode hole 7 while the anode 6 is provided with an anode hole 9. The vacuum chamber 2 will contact through the anode 6 with the discharge chamber 1 while communicate through the anode hole 9 with the discharge chamber 1. Take-out electrodes 14a, 14b for taking out ion flow from the weakly ionized freely expanded flow formed in the vacuum chamber 2 are arranged between the vacuum chambers 2, 3. Said take- out electrodes 14a, 14b are provided with plural take-out electrode holes 15a, 15b for passing ions.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion source, and particularly to ion implantation, ion-based exposure, and
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] As a conventional device of this kind, for example, there is one shown in FIG. 4 published in Ion Implantation (Shokodo, 1976) by Kouji Ig et al.

First, the configuration of the conventional ion source shown in FIG. 4 will be explained. In FIG. 4, the conventional ion source includes a discharge chamber 1 and a vacuum chamber 25. The discharge chamber 1 includes a cathode 4 and an intermediate electrode 5.
and an anode 6 are provided, and the intermediate electrode 5 and the anode 6 are provided with an intermediate electrode hole 7 and an anode hole 24, respectively. Also,
The discharge chamber 1 includes a carrier gas introduction 09 for introducing carrier gas between the cathode 4 and the intermediate electrode 5, and a middle M electrode 5.
A sample gas inlet 10 for introducing sample gas is provided between the anode 6 and the anode 6 .

Vacuum chamber 25 is separated from discharge chamber 1 by anode 6 and communicates with discharge chamber 1 through anode hole 24 . Vacuum chamber 25
A vacuum outlet 28 for evacuation and an extraction electrode 26 for extracting ions close to the anode 6 are provided. This extraction electrode 26 has an extraction electrode hole 2 for extracting ions.
7 is provided.

Next, we will discuss the operation of a conventional ion source.

First, the vacuum chamber 25 is evacuated from the vacuum port 28,
The discharge chamber 1 and the vacuum chamber 25 are brought to a predetermined degree of vacuum. 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 4 and the intermediate electrode 5. Then, the carrier gas is ionized by glow discharge or arc discharge generated between the cathode 4 and the intermediate electrode 5, and plasma is generated. The generated plasma flows through the intermediate electrode hole 7.
and flows between the intermediate electrode 5 and the anode 6. Here, when the sample gas is introduced into the discharge chamber 1 from the sample gas inlet 10, the plasma of the carrier gas collides with the introduced sample gas to ionize the sample gas. The ionized sample gas passes through the anode hole 24 and is connected to the anode 6 and extraction electrode 2.
6. Since a DC voltage is applied between the anode 6 and the extraction electrode 26 and an electric field is generated, an ion flow is extracted from the extraction electrode hole 27 in the direction shown by arrow E in FIG. 4 due to this electric field. At this time, unionized neutral gas flows into the vacuum chamber 25 together with the ion flow in the form of a molecular beam.

[Problems to be Solved by the Invention] In the conventional ion source, as described above, the ion extraction electrode was provided close to the anode of the discharge chamber. For this reason,
Since the extraction electrode extracts an ion stream from the high-temperature plasma generated in the discharge chamber, the temperature of the resulting ion stream was high and the random motion of the ions was large. This 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 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 in that the ion flow rate is significantly lower than in the above-mentioned conventional ion source and the device is complex.

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 by a weakly ionized gas generating means, passes this through one hole provided in a partition plate, and supplies it to a first vacuum. A plurality of holes each having a plurality of holes are introduced into the chamber and subjected to supersonic free expansion in a first vacuum chamber to generate a supersonic free expansion flow. An electric field is generated between the extraction electrodes by an electric field generating means to extract the ion flow into the second vacuum chamber.

[Function] The plurality of extraction electrodes in the present invention extract an ion flow from a region where the gas temperature has decreased in a supersonic free expansion flow of a weak electric gas that is free expanded at supersonic speed in the first vacuum chamber,
Since the gas temperature is lowered by introducing the gas into the second vacuum chamber and further expanding the gas in the second vacuum chamber, an ion flow with extremely small random motion is obtained. This ion source can be applied to ultra-high brightness ion beams such as focused ion beams.

[Example] Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram schematically showing an ion source according to an embodiment of the present invention. First, the general configuration of the ion source of this embodiment will be explained. In Figure 1, the ion source is discharge chamber 1.
A vacuum chamber 2 and a vacuum chamber 3 are provided. The discharge chamber 1 generates weakly ionized gas. The vacuum chamber 2 is for allowing the weakly ionized gas generated in the discharge chamber 1 to freely expand at supersonic speed. The vacuum chamber 3 serves to further expand the supersonic free expansion flow generated within the vacuum chamber 2. Therefore, the vacuum chamber 2 is made to have a higher vacuum than the discharge chamber 1, and the vacuum chamber 3 is made to have a higher vacuum than the vacuum chamber 2. For example, discharge chamber 1 during operation
is about 5 Q TOrr, and vacuum chamber 2 is about 10-” T
The vacuum chamber 3 is set to about 10-II Torr at orr Pj degrees.

The discharge chamber 1 is provided with a cathode 4, an intermediate electrode 5, an anode i6, etc. The intermediate electrode 5 is provided with an intermediate electrode hole 7, and the anode 6 is provided with an anode hole 9. Further, the discharge chamber 1 is provided with a carrier gas inlet 10 for introducing carrier gas and a sample gas inlet 11 for introducing sample gas.

The vacuum chamber 2 is in contact with the discharge chamber 1 through the anode 6 and communicates with the discharge chamber 1 through the anode hole 9 . The shape of the anode hole 9 may be circular, square or rectangular. The vacuum chamber 2 is provided with a vacuum outlet 12 for evacuation. vacuum chamber 2
An extraction electrode 14a is provided between the vacuum chamber 3 and the vacuum chamber 3 to separate the two vacuum chambers and to extract an ion flow from the supersonic free expansion flow generated within the vacuum chamber 2.

The vacuum chamber 3 is provided with a vacuum outlet 13 for evacuation and the other extraction electrode 14b. These extraction electrodes 14a and 1411 are provided with a plurality of extraction electrode holes 15a and 1511, respectively, through which ions pass. A DC voltage is applied to the extraction electrodes 14a and 14b from a DC voltage generation source not shown, and the extraction electrodes 148.14b
An electric field is generated between them. Such an extraction electrode is not limited to one consisting of two electrodes 14a and 14b as shown in FIG. An electric field may be generated by

The configuration of one embodiment of the present invention described above eliminates the drawbacks of conventional ion sources. That is,
In the conventional ion source, as shown in FIG. 4, the extraction electrode is provided close to the anode, which is a partition plate, so that there is a distance between the extraction electrode and the anode. Since the space between the electrode and the electrode is filled with gas, the weakly ionized gas cannot form a supersonic free expansion flow. Therefore, in this invention, in order to cause the weakly ionized gas obtained in the discharge chamber to freely expand at supersonic speed in the first vacuum chamber, the extraction electrode is provided at a sufficient distance from the anode, and the supersonic free expansion flow with a reduced gas temperature is provided. In order to extract ions from the ions, the extraction electrode is composed of a plurality of electrodes, an electric field is applied between these electrodes, and in order to lower the temperature of the extracted ion stream, the extracted ion stream is further guided into a second vacuum chamber and expanded.

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

After achieving a predetermined degree of vacuum, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 10.

The carrier gas introduced is, for example, argon gas. Here, when a DC voltage is applied between the cathode 4 and the intermediate electrode 5, 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 7 and
and the anode 6. The inflowing plasma ionizes the sample gas introduced from the sample gas inlet 11.

The sample gas introduced is, for example, sodium vapor.

The plasma of the ionized sample gas and carrier gas passes through the anode hole 9, 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 zone of silence 1d.
), but this quiet region 16 is called a barrel-shaped shock wave (Bar
rel 5hock) 17 and Matsuha disc (Mach
D lsk ) 19.

Outside the quiet region 16, there is a Jet Boundary near the barrel-shaped Ili strike wave 17.
18 is formed, and a reflection vfJ is formed downstream of Matsuha disk 19.
Shock wave (Re41ected 5hock) 20 is formed. Matsuha disk 19 and reflected shock wave 2 shown in Figure 1
0 is a drawer! This figure shows the ideal shape that would occur if the influence of the presence of tIIi 14a and 14b could be ignored; in reality, the shape would be disturbed by the extraction electrode.

In the quiet region 16, the plasma undergoes adiabatic expansion, and as it moves downstream, the plasma density, humidity, and interparticle W! The J steepness decreases and the electric 11 degrees freezes, but on the contrary, the plasma flow velocity increases. The density due to adiabatic expansion is 1/1000 of the plasma density in the discharge chamber 1 &! decreases over time,
The temperature will be about 1/100 of the temperature inside the discharge chamber 1. Therefore, when the plasma in the discharge chamber 1 is generated by a typical glow discharge or arc discharge, the temperature due to adiabatic expansion remains at an absolute temperature of 12,000 to 1,000 degrees for electrons, but for neutral atoms, molecules, ions, etc. For free particles it drops to 20 to several degrees.

Since the above-mentioned Matsuha disk 19 is a shock wave, the gas temperature increases downstream of the Matsuha disk 19. Therefore,! Since the gas temperature in the 3i-dark region 16 is lowest in front of the Matsuha disk 19, it is preferable that ions be extracted in this region.
It will be installed 10-20m before 111 of 119.

By the way, the quiet region 16 is defined by the shape and size of the anode hole 9, the gas pressure in the discharge Ng1, and the pressure in the vacuum chamber 2. Further, as described above, the nature of the flow in the quiet region 16 is such that the gas expands as it goes downstream, the cross-sectional area of the region becomes larger, the flow velocity increases, and the gas density and temperature decrease. Therefore, in order to optimally maintain the extraction of ions from the quiet region 16 of the supersonic free expansion flow in response to changes in various conditions such as the pressure inside the vacuum chamber, it is necessary to adjust the extraction electrode to the supersonic free expansion flow. It is preferable to provide it movably. An outline of such a movable mechanism is shown in FIG. In FIG. 2, for example, a vacuum with backing 22! The outer wall 31 of No. 3 is fitted into the inner wall 21 of the vacuum chamber 2. Extracting electrodes 14a and 14b provided in the vacuum chamber 3
can be freely moved by sliding the outer wall 31 relative to the inner wall 21 in the directions of arrows C and D shown in FIG.
Ion currents can be extracted at optimal positions according to conditions.

A DC voltage is applied to the extraction electrodes 148.14b shown in FIGS. 1 and 2, and the extraction electrodes 14a and 141)r
An electric field is generated at -. Ions move in the vector direction of the electric field, and electrons move in the opposite vector direction of the electric field. Thereby, the ion flow is extracted into the vacuum chamber 3 through the extraction electrode holes 15a and 15b. The ion flow extracted by the electric field between extraction electrodes 14a and 14b is indicated by arrow B in FIG. Since the extraction electrodes 14a and 14b are provided with a plurality of extraction electrode holes 15a and 15b, respectively, ions can be extracted efficiently. The extracted ion stream expands within the vacuum chamber 3, and the gas temperature further decreases.

By the way, when the supersonic free expansion flow in the quiet region 16 collides with the extraction electrode 14a, a shock wave is formed, and the temperature of the gas increases downstream thereof. Therefore, in order to prevent a rise in gas temperature, it is preferable that the extraction electrode be shaped so that it does not generate shock waves as much as possible. FIG. 3 is an enlarged view showing an example of such an extraction electrode. In FIG. 3, the extraction electrode 14a has a tip portion 140 that projects toward the supersonic free expansion flow indicated by arrow A at 33 in FIG. Wt1 generated when the supersonic free expansion flow collides with the tip 140 etc.
Since the attack wave 23 is weak, the rise in gas temperature is suppressed.

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. It may be generated by electric discharge, and in such a case, the same effects as in the above-mentioned embodiments can be achieved.

Further, in the above embodiment, the vacuum chamber 2 and the vacuum chamber 3 are separated by the extraction electrode 14a, but the vacuum chamber 2 and the vacuum chamber 3 are separated by the extraction electrode 14a.
A partition plate having holes or nozzles formed therein may be provided between the two vacuum chambers, and the two vacuum chambers may be separated by this partition plate, and an extraction electrode may be provided within the vacuum chamber 3.

In this case, the supersonic free expansion flow in the vacuum chamber 2 expands further in the vacuum chamber 3, resulting in a much lower temperature gas flow, and in particular, the extraction electrode 14.8.14b is separated from the two vacuum chambers. When installed separated by -I on the downstream side from the partition plate, a lower temperature ion flow can be extracted from a lower temperature gas flow compared to the case where the vacuum chamber 2 and the vacuum chamber 3 are separated by the extraction electrode 14a. I can do it.

[Effects of the Invention] As described above, according to the present invention, a plurality of extraction electrodes each having a plurality of holes are formed on the partition plate between the weakly ionized gas generating means and the first vacuum chamber. It is installed in the supersonic free expansion flow region of the plasma that is formed in the first vacuum chamber through one hole in which the temperature of free particles such as neutral atoms, molecules, and ions decreases to an absolute temperature of 20 The configuration is such that ions are extracted from the plasma flow, which has been reduced to a temperature of ~ several degrees Celsius, into the second vacuum chamber through a plurality of holes provided in a plurality of extraction electrodes. A small ion flow with random motion can be efficiently extracted. 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 diagram showing a moving mechanism for the extraction electrode shown in FIG. 1. FIG. 3 is an enlarged view showing an example of an extraction electrode configured to weaken the intensity of a generated shock wave in an ion source according to an embodiment of the present invention. FIG. 4 is a diagram showing a conventional ion source. In the figure, 1 is a discharge chamber, 2 is a first vacuum chamber, and 3 is a second vacuum chamber.
vacuum chamber, 4 is a cathode, 5 is an intermediate electrode, 6 is an anode, 9 is an anode hole, 14a and 14b are extraction electrodes, 15a, 15b
1 indicates an extraction electrode hole, and 16 indicates a quiet region. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa 17 Ichihaku Figure 3 Procedural Amendment (Volunteer) Name of the Invention Relationship with the Person Who Amends the Ion Source Case Patent Applicant Address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative 廿：廿：
尤=pugoits Tenrijin Shiki Moriya Address 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo
, the details to be amended ("t", claims column, detailed explanation of the invention column, and brief explanation of drawings column 6, contents of the amendment as shown in the attached sheet. (Matters stated in the column to be amended) (Other than that, no changes have been made to the contents.) Above Description 1, Name of the Invention Ion Source 2, Claims <1) Weakly ionized gas generating means for generating a weakly ionized gas by partially defrosting gas atoms or gas molecules. and a first vacuum chamber for supersonic free expansion of the weakly ionized gas generated by the weakly ionized gas generating means, separating the weakly ionized gas generating means and the first vacuum chamber,
and a partition plate formed with one hole for introducing the weakly ionized gas generated by the weakly ionized gas generating means into the first vacuum chamber; A second vacuum chamber for further expanding the ionized gas, and a weakly ionized gas provided in a region where a supersonic free expansion flow of a weakly ionized gas whose gas temperature is lowered by supersonic free expansion in the first vacuum chamber exists. , comprising a plurality of extraction electrodes each having a plurality of holes formed therein, and an electric field generating means for generating an electric field in the plurality of extraction electrodes, the plurality of extraction electrodes provided on the plurality of extraction electrodes. An ion source characterized in that ions are extracted from a weakly supersonic free expansion flow with a reduced gas concentration into the second vacuum chamber through a plurality of holes. (2) The ion source according to claim 1, wherein the extraction electrode is provided movably with respect to the supersonic free expansion flow. (3) The weakly ionized gas generating means may include glow discharge, arc discharge, RF discharge, electron impact ionization, or laser ll! An ion source according to claim 1 or 2, characterized in that the ion source uses electrogenic ionization. (4) The ion source according to any one of claims 1 to 3, wherein the hole provided in the partition plate is circular. (5) The ion source according to any one of claims 1 to 3, wherein the hole provided in the partition plate is square or rectangular. 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an ion source, and particularly 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] Conventional devices of this type include, for example, the one written by I1114 et al.: AEON IMBRANTESI NIPPON (Shokodo, 1976).
There is one shown in Figure 4 published in . First, the configuration of the conventional ion source shown in FIG. 4 will be explained. In FIG. 4, the conventional ion source includes a discharge chamber 1 and a vacuum chamber 25. The discharge chamber 1 includes a cathode 4 and an intermediate electrode 5.
and an anode 6 are provided, and the intermediate electrode 5 and the anode 6 are provided with an intermediate electrode hole 7 and an anode hole 24, respectively. Also,
The discharge chamber 1 has a carrier gas inlet 9 for introducing carrier gas between the cathode 4 and the intermediate machine ff15, and a sample gas inlet for introducing the sample gas between the intermediate electrode 5 and the anode 6. 10 are provided. Vacuum chamber 25 is separated from discharge chamber 1 by anode 6 and communicates with discharge chamber 1 through anode hole 24 . Vacuum chamber 25
A vacuum outlet 28 for evacuation and an extraction electrode 26 for extracting ions close to the anode 6 are provided. This extraction electrode 26 has an extraction electrode hole 2 for extracting ions.
7 is provided. Next, the operation of the conventional ion source will be explained. First, the vacuum chamber 25 is evacuated from the vacuum port 28,
The discharge chamber 1 and the vacuum chamber 25 are brought to a predetermined degree of vacuum. Subsequently, while exhausting air from the vacuum opening 28, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 9, and the cathode 4
A DC voltage is applied between the intermediate electrode 5 and the intermediate electrode 5. Then, the carrier gas is ionized by glow discharge or arc discharge generated between the cathode 4 and the intermediate electrode 5, and plasma is generated. The generated plasma passes through the intermediate electrode hole 7 and flows between the intermediate electrode 5 and the cathode 6. 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 anode hole 24 and flows between the anode w16 and the extraction electrode 26. A DC voltage is applied between the anode 6 and the extraction electrode 26,
Since an electric field is generated, arrow E in Figure 4 is caused by this electric field.
An ion flow is extracted from the extraction electrode hole 27 in the direction shown by . At this time, along with the ion flow, unionized neutral gas also flows into the vacuum chamber 25 in the form of a molecular beam. [Problems to be Solved by the Invention] In the conventional gas ion source, as mentioned above, the ion extraction electrode was installed close to the positive side of the discharge chamber. Since ions are extracted from the high-temperature plasma generated in the chamber, the temperature of the resulting ion stream was high and the random motion of the ions was large.This random motion remains even in the ion beam obtained by accelerating the ion stream. Therefore, there is a limit to the diameter that can be focused using an electromagnetic field, and it has been impossible to apply conventional gas ion sources to ultra-high-intensity ion beams such as focused ion beams.By the way, gas atoms or Until now, as an ion source for ultra-bright ion beams for 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.
Although the temperature of the extracted ion stream is low and the random motion of the ions is small, there are problems in that the ion flow rate is significantly lower than in gas ion sources and the device is complex. Therefore, the present invention was 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. c Means for Solving Problem] 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 diaphragm.
It is introduced into a first vacuum space through two holes and allowed to freely expand supersonically within the first vacuum chamber. A weakly ionized gas supersonic free expanding flow is formed, and in the 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 to extract the ion flow whose temperature has decreased into the second vacuum chamber. . [Function] The plurality of extraction electrodes in the present invention extracts the ion flow from the region where the gas temperature has decreased in the supersonic free expansion flow of the weakly ionized gas that is supersonically freely expanded in the first vacuum chamber,
Introduced into the second vacuum chamber. In the second vacuum chamber, the gas expands roughly and its temperature decreases, resulting in a stream of ions with very low temperature, ie, ions with very little random motion. Therefore, this gas 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. FIG. 1 is a diagram schematically showing an ion source according to an embodiment of the present invention. First, the general configuration of the ion source of this embodiment will be explained. In Figure 1, the ion source is discharge chamber 1.
A vacuum chamber 2 and a vacuum chamber 3 are provided. The discharge chamber 1 is for generating weakly ionized gas, the vacuum chamber 2 is for supersonic free expansion of the weakly ionized gas generated in the discharge chamber 1, and the vacuum chamber 3 is for generating weakly ionized gas in the vacuum chamber 2. This is to further expand the supersonic free expansion flow. Therefore, the vacuum chamber 2 is kept at a higher vacuum than the discharge chamber 1, and the vacuum chamber 3 is kept at a higher vacuum than the vacuum chamber 2. For example, during operation, the discharge chamber 1 is at about 50 Torr, and the vacuum chamber 2 is at about 10 Torr.
The vacuum chamber 3 is maintained at about 10-' Torr. The discharge chamber 1 is provided with a cathode 4, an intermediate electrode II 5, and an anode 6. The intermediate electrode 5 is provided with an intermediate electrode hole 7, and the anode 6 is provided with an anode hole 9. Further, the discharge chamber 1 is provided with a carrier gas inlet 10 for introducing carrier gas and a sample gas inlet 11 for introducing sample gas. The vacuum chamber 2 is in contact with the discharge chamber 1 through the anode 6 and communicates with the discharge chamber 1 through the electrode hole 9 . The shape of the +i electrode hole may be circular, square, or rectangular. vacuum chamber 2
is provided with a vacuum outlet 12 for evacuation. Between the vacuum chamber 2 and the vacuum chamber 3, these two vacuum chambers are separated,
Also, one extraction electrode 14a is provided for extracting an ion flow from a weakly ionized gas supersonic free expansion flow formed in the vacuum chamber 2. The vacuum chamber 3 is provided with a page emptying port 13 for evacuation and the other drawer 1fti14b. These extraction electrodes 14
A and 14b are provided with a plurality of extraction electrode holes 15a and 15b, respectively, through which ions pass. A DC voltage is applied to the extraction electrodes 14a and 14b from a DC voltage generation source (not shown), and the extraction electrodes 148.14b
An electric field is generated between them. Such extraction electrodes are not limited to those consisting of two electrodes 148 and 141 as shown in Fig. 1, but are formed by forming a groove with a large number of electrodes, and a voltage is applied between them. may be applied to generate an electric field. The configuration of one embodiment of the invention described above overcomes the drawbacks of conventional gaseous ion sources. That is, in the conventional ion source, as shown in FIG. 4, the extraction electrode is provided close to the anode, which is the partition plate.
The space between the extraction electrode and the anode is filled with weakly ionized gas, and the weakly ionized gas does not form a supersonic free expansion flow. Therefore, in this invention, in order to allow the weakly ionized gas obtained in the discharge chamber to freely expand at supersonic speed in the first vacuum chamber, the extraction electrode is provided at a sufficient distance from the anode, and the weakly ionized gas with reduced gas humidity is expanded at supersonic speed. In order to extract the ion flow from the free expanding flow, the extraction electrode is made up of multiple electrodes, an electric field is applied between them, and the gas is further expanded in a second vacuum chamber to further lower the temperature of the extracted ion flow. let Next, the specific operation of the ion source shown in FIG. 1 will be explained in detail. After the discharge chamber 1, vacuum chamber 2, and vacuum chamber 3 are brought to a predetermined degree of vacuum, carrier gas is introduced into the discharge chamber 1 from the carrier gas inlet 10 while performing evacuation. The carrier gas introduced is, for example, argon gas. Here, Yin t!
When a DC voltage is applied between i4 and the intermediate electrode 5, 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 7 and flows between the intermediate electrode 5 and the positive electrode [i6. The incoming plasma is sample gas inlet 1
The sample gas introduced from 1 is ionized. The sample gas introduced is, for example, sodium vapor. The plasma of carrier gas and sample gas is I! ! IM hole 9
, 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 fR region of this supersonic free expansion flow is called the zone of 511ence, and this quiet zone 16 is a barrel-shaped shock wave < B arreI
5hock) 17 and Matsu Hachienban (Mach D ls
k) is the area surrounded by 19. Outside the quiet region 16, a jet boundary 18 is formed close to the barrel-shaped shock wave 17, and a reflected shock wave (Re) is formed downstream of the Matsuha disk 19.
A reflected 5hock>20 is formed. Figure 1 shows the reflection of disk 19 on the pine tree! ! ! The i-striking wave 20 represents an ideal shape when the influence of the presence of the extraction electrodes 14a and 14b can be ignored, and is actually disturbed by the extraction electrodes. In the quiet region 16, the plasma undergoes adiabatic expansion, and as it moves downstream, the density, temperature, and frequency of collisions between particles decrease, and the degree of ionization freezes, but the flow velocity of the plasma increases. The density of plasma due to adiabatic expansion is
The plasma density decreases to about 1/1000 of the plasma density in chamber 1, and the plasma temperature decreases to 1/1000 of the plasma temperature in discharge chamber 1.
, / will be about 100. Therefore, when the plasma in the discharge chamber 1 is generated by a typical glow discharge or arc discharge, the temperature of the plasma due to adiabatic expansion remains at an absolute temperature of 2000 to 1000 degrees for electrons, but it is For heavy particles such as, the temperature decreases to 20 to several degrees. Since the above-mentioned Matsuha disk 19 is a shock wave, the gas temperature increases downstream of one Matsuha disk. Therefore, the gas temperature in the quiet region 16 is Matsuha Yen! ! ! Since the ion current is lowest in front of one region, it is preferable to extract the ion current in this region, and one of the extractors t11m''14a is installed, for example, in front of the 10 to 20I!l extraction of the Matsuha disk 19. [The shape and size of the region 16 is the same as that of the anode hole 9.
, the gas pressure in the discharge chamber 1 and the pressure in the vacuum chamber 2. Further quiet area 1
As described above, the gas expands as it goes downstream, the cross-sectional area of the region increases, the flow rate increases, and the density and temperature of the gas decrease. Therefore, in order to optimally maintain the extraction of the ion flow from the quiet region 16 of the supersonic free expansion flow in response to changes in various conditions such as the pressure inside the vacuum chamber, it is necessary to adjust the extraction electrode to the supersonic free expansion flow. It is preferable to provide it movably. An outline of such a movable mechanism is shown in FIG. In FIG. 2, the outer wall 31 of the vacuum chamber 3, for example with the backing 22, is fitted into the inner wall 21 of the vacuum chamber 2. Extracting electrode 1 provided in vacuum chamber 3
4a and 14b can be freely moved by sliding the outer wall 31 in the directions of arrows C and D shown in FIG. 2 with respect to the inner v21, so that the ion flow can be extracted at the optimum position according to the conditions. A DC voltage is applied to extraction electrodes 148.14b shown in FIGS. 1 and 2, and an electric field is generated between extraction electrodes 14a and 14b. The ions move in the direction of the electric field vector,
Electrons move in the opposite direction of the electric field vector. Thereby, the ion flow is extracted into the vacuum chamber 3 through the extraction electrode holes 15a and 15b. The ion flow extracted by the electric field between the extraction electrodes 14a and 141) is indicated by the arrow B in FIG.
Indicated by Since the extraction electrodes 14a and 14b are provided with a plurality of extraction electrode holes 15a and 15b, respectively, the ion flow can be efficiently extracted. The extracted gas containing the ion flow is further heated up in the vacuum chamber 3, and its temperature is further lowered. By the way, when the supersonic free expanding flow in the quiet region 16 impinges on the extraction electrode 14.8, it generally forms a shock wave, and the temperature of the gas increases downstream thereof. Therefore, in order to prevent a rise in gas temperature, it is preferable that the extraction electrode be shaped so that it does not generate shock waves as much as possible. FIG. 3 is an enlarged view showing an example of such an extraction electrode. In FIG. 3, the extraction electrode 14a has a tip portion 14c that projects toward the supersonic free expansion flow indicated by arrow A in FIG. It is generated when the supersonic free expansion flow collides with the tip portion 14c! i! Since there are 23 waves and 3 waves per wave, the rise in gas temperature is suppressed. In the above embodiment, the case where the plasma in the discharge seedling 1 is generated by glow discharge or arc discharge has been explained, but the plasma in the discharge 1 can be generated without ionization such as RF* electricity or L laser-induced ionization on the electron impact side. It may be generated by electrode discharge, and in such a case, the same effects as in the above-mentioned embodiments can be achieved. Further, in the above embodiment, the vacuum chamber 2 and the vacuum chamber 3 are separated by the extraction electrode 14a, but the vacuum chamber 2 and the vacuum chamber 3 are separated by the extraction electrode 14a.
A partition plate having holes or nozzles formed therein may be provided between the two vacuum chambers, and the two vacuum chambers may be separated by this partition plate, and an extraction electrode may be provided within the vacuum chamber 3. In this case, the weakly ionized gas supersonic free expansion flow in the vacuum chamber 2 further expands sufficiently in the vacuum chamber 3, so that an even lower temperature gas flow (q) is generated, and in particular, the extraction electrodes 14a, 14
b is installed sufficiently downstream from the partition plate that separates the two vacuum chambers, vacuum chambers 2 and 3 can be connected to the extraction electrode 1.
A lower temperature ion flow can be extracted from a lower temperature gas flow than when separated by 4a. [Effects of the Invention] As described above, according to the present invention, a plurality of electric drawers each having a plurality of holes are connected to the partition plate between the weakly ionized gas generating means and the first vacuum chamber. It is installed in the supersonic free expansion flow region of the plasma formed in the first vacuum chamber through one hole formed in the Since the configuration is configured to extract ions from the plasma flow whose temperature has dropped to 20 to several degrees Celsius to the second vacuum chamber using a plurality of extraction electrodes each having a plurality of holes, the ion flow with a low temperature, i.e. A small ion flow with random ion motion 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 diagram showing a moving mechanism for the drawer north pole shown in FIG. 1. FIG. 3 is an enlarged view showing an example of an extraction electrode configured to weaken the intensity of a shock wave generated in an ion source according to an embodiment of the present invention. FIG. 4 is a diagram showing a conventional ion source. In the figure, 1 is a discharge chamber, 2 is a first vacuum chamber, and 3 is a second vacuum chamber.
vacuum chamber, 4 is a cathode, 5 is an intermediate electrode, 6 is an anode, 9 is an anode hole, 14a and 14b are extraction electrodes, 15a, 15b
16 indicates the extraction M pole hole, and 16 indicates the quiet region of the supersonic free expansion 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 first means for freely expanding the weakly ionized gas generated by the weakly ionized gas generating means at supersonic speed. a vacuum chamber separating the weakly ionized gas generating means and the first vacuum chamber,
and a partition plate formed with one hole for introducing the weakly ionized gas generated by the weakly ionized gas generating means into the first vacuum chamber; a second vacuum chamber for further expanding the ionized gas; and a second vacuum chamber provided in the region where a supersonic free expansion flow with a reduced gas temperature obtained by supersonic free expansion in the first vacuum chamber exists, respectively. a plurality of extraction electrodes in which a plurality of holes are formed; and an electric field generating means for generating an electric field between the plurality of extraction electrodes, the plurality of holes provided in the plurality of extraction electrodes. The ion source is characterized in that the ions are extracted from the supersonic free expansion flow into the second vacuum chamber through the steps of the supersonic free expansion flow. (2) Claim 1, wherein the extraction electrode is provided movably with respect to the supersonic free expansion flow.
Ion source as described in section. (3) The ion source according to claim 1 or 2, wherein the weakly ionized gas generating means uses glow discharge, arc discharge, RF discharge, electron impact ionization, or laser-induced ionization. (4) The ion source according to any one of claims 1 to 3, wherein the hole provided in the partition plate is circular. (5) The ion source according to any one of claims 1 to 3, wherein the hole provided in the partition plate is square or rectangular.