JP4583067B2 - Ion source - Google Patents

Description

  The present invention provides a small-diameter ion beam used for, for example, a surface physical analysis device, a semiconductor manufacturing inspection device, an ion probe for a defect repair device, ion implantation, ion beam exposure, ion beam deposition, ion beam etching, ion beam drawing, etc. It relates to an ion source for use.

As this type of ion source, the present applicant has previously developed and proposed in Japanese Patent Laid-Open No. 2001-283745 (Patent Document 1). The ion source proposed in Patent Document 1 will be described with reference to the schematic diagram of FIG. In other words, in the proposed ion source 31, a voltage is applied by the anode power source 36 between the cathode electrode 32 and the source gas introduction part 35 serving as an anode electrode having a small opening 34 smaller than the opening 33 of the cathode electrode 32. As a result, the source gas injected at a high pressure from the minute opening 34 of the source gas introduction part 35 toward the opening 33 of the cathode electrode 32 is turned into plasma. As shown in FIG. 5c, the plasma generation region is limited to a minute region 41 substantially along the injection direction of the source gas.
In order to turn the source gas into plasma, it is necessary to emit electrons from the cathode electrode 32 to supply the source gas. There are secondary electron emission and field emission as typical techniques for emitting electrons to the high-pressure-injected source gas in order to turn the source gas into plasma.
The secondary electron emission means that a predetermined voltage is applied between the electrodes to generate an electric field at the cathode electrode, and the source gas injected toward the cathode electrode is caused to collide with the cathode electrode to The electrons emitted at this time are referred to as secondary electrons.
The field emission is a method of forcibly emitting electrons from the cathode electrode 32 as described in Patent Document 2. Specifically, a strong voltage (several hundreds to thousands of volts) is applied between the electrodes to generate a strong electric field (about 10 ⁹ V / m) in the vicinity of the surface of the cathode electrode 32. By lowering the potential barrier, field emission of electrons is performed by the tunnel effect in quantum mechanics.

  An extraction electrode 38 having an opening 37 larger than the opening 33 of the cathode electrode 32 is arranged on the opposite side of the cathode electrode 32 from the source gas introduction portion 35 side. When a voltage is applied between the electrode 32 and the electrode 32 by the extraction power source 39, ions are extracted from the plasma in the minute region through the opening 33 of the cathode electrode 32, and ions are released from the opening 37 of the extraction electrode 38.

Furthermore, in order to satisfactorily generate plasma from the raw material gas injected at high pressure, the magnitude of the voltage applied between the raw material gas introduction part 35 and the cathode electrode 32, the injection pressure of the raw material gas, The relationship between the distance from the minute opening 34 to the cathode electrode 32 may be determined based on Paschen's law. By determining the relationship based on Paschen's law, even in the region 41 where the high-pressure injected source gas exists (see FIG. 5c), the pressure does not decrease due to diffusion, and the particle directions are relatively aligned. It is possible to generate a discharge in the minute region 40 and to generate plasma in the minute region 40 satisfactorily.
JP 2001-283745 A Japanese Patent No. 3436219

  Incidentally, in the ion source proposed in Patent Document 1 above, the gas pressure in the vicinity of the minute opening 34 of the anode electrode 35 is about the same as the pressure of the source gas introduction part 35 and about atmospheric pressure. At this time, according to Paschen's law, when the source gas is helium (He) gas, the discharge voltage is minimum when the product of the pressure of the He gas and the distance between electrodes (gap shown in FIG. 5b) is about 5 Pa · m. Become. When this is calculated at atmospheric pressure, the distance between the electrodes is 50 μm. However, it is difficult to accurately fix the positional relationship such as the mutual axis and parallelism of the anode electrode 35 and the cathode electrode 32 with such a narrow distance. is there. Therefore, it is inevitable that the discharge voltage rises to some extent, and the interelectrode distance is about 200 μm, but this is still a narrow interelectrode distance.

  In the case of the development examples so far, as shown in FIG. 5b, the opening diameter φa of the minute opening 34 of the anode electrode 35 is 50 μm, the opening diameter φb of the opening 33 of the cathode electrode 32 is 100 μm, and the interelectrode gap (gap) is 200 μm. It is. For this reason, as shown in FIG. 6, the jet-like gas ejected from the micro-openings 34 is blocked by the surface of the cathode electrode 32 and becomes a turbulent flow and accumulates between the electrodes. The performance of the proposed ion source was reduced, such as a decrease in the ion beam current due to the divergence of the ion and the deterioration of the ionization efficiency.

  The present invention has been made to solve the above-mentioned problems, and its object is to make the raw material gas injected at a high pressure from the minute opening of the anode electrode in the injection direction without staying between the cathode electrode. It is an object of the present invention to provide an ion source capable of improving the ionization efficiency of a flowing and jetted source gas to generate good plasma and reducing power consumption.

To achieve the above object, an ion source according to the present invention (claim 1), the ion of the cathode electrode having an anode electrode having fine openings, the large ion extraction aperture than the minute opening of the anode electrode the source gas pressure injected toward the extraction aperture, a discharge by a high voltage applied between the anode electrode and the cathode electrode, the ion source is formed by plasma, the cathode electrode, comprising the ion extraction aperture The discharge forming portion is disposed close to the minute opening of the anode electrode, and has a plurality of gas exhaust openings on the outer peripheral side of the ion extraction opening of the discharge forming portion.

  In the above configuration, it is inevitable that a part of the gas injected into the cathode electrode at a high pressure from the minute opening of the anode electrode collides with the discharge forming portion of the cathode electrode, but the ion in the discharge forming portion of the cathode electrode is unavoidable. Since the gas flows from the outlet opening and the outer peripheral opening of the discharge forming portion, the gas can be quickly exhausted without staying between the cathode electrode and a smooth jet-like gas flow can be obtained. This also prevents beam divergence and deterioration of ionization efficiency, and an expected ion beam current can be obtained.

In the ion source of claim 1, the cathode electrode is formed by a flat cathode electrode plate having a circular opening, and has the same length with a thickness of 250 μm or less from the periphery of the circular opening toward the center of the opening. a plurality of needle-like metal pin sharpened sharp tip with is has at equal intervals, are formed in a circular shape of the ion extraction aperture of and the circular opening concentric does not contact the tip of the metal pin, the A structure in which a space between adjacent metal pins is configured as the gas exhaust opening can be used. Even if the cathode electrode having such a configuration is used, the effect of the first aspect can be obtained. In this case, the thickness of the metal pin is set to 250 μm or less, and if it is thicker than this, the opening on the outer peripheral side of the discharge forming portion becomes small, depending on the number of metal pins provided at equal intervals, and the ion extraction This is because the ratio with respect to the opening (hereinafter referred to as the opening ratio) becomes small and gas stays between the cathode electrode and rapid exhaust cannot be expected. The reason for providing the metal pins at equal intervals is to ensure the symmetry of the circular shape formed at the tip of the metal pin and to make the electric field distribution uniform at the discharge forming site formed by the tip of the metal pin. . This is because if the uniformity of the electric field distribution is lost, the trajectory of the discharged and accelerated ions changes at that portion, which may adversely affect the ion beam trajectory and ion beam shape.

  In this case, it is desirable that the tip of at least one of the needle-like metal pins has a curvature, and the curvature radius of the tip is approximately 100 nm or less. This facilitates electron emission at the tip of the metal pin regardless of whether the electron supply method is secondary electron emission or field emission. For this reason, it is possible to reduce the power consumption in the ion source by setting the voltage between the electrodes lower than in the prior art. In addition, since it is possible to sufficiently supply the electrons necessary for ionization and plasmatization of the source gas, ionization efficiency is improved and good plasma is obtained.

  In the ion source according to claim 1, the cathode electrode is formed by a flat cathode electrode plate having a circular opening, and an annular electrode having an ion extraction opening at the center of the circular opening is not more than 250 microns. Can be used that is fixed by 3 to 5 metal pins having the same length and the same length (claim 4). Even if the cathode electrode having such a configuration is used, the effect of the first aspect can be obtained. In this case, the reason for using 3 to 5 metal pins having a thickness of 250 microns or less and the same length to fix the annular electrode is to obtain a large aperture ratio. The number is sufficient to fix and support the annular electrode with sufficient strength, and is not limited to 3 to 5 in particular as long as the number of the electric field distributions generated on the metal pins is evenly dispersed.

In this case, it is preferable that minute projections are formed on the entire surface of the annular electrode or on the surface on the anode electrode side. It is also conceivable that the tip of at least one of the microprotrusions has a curvature, and the radius of curvature of the tip is approximately 100 nm or less. Even with the ion source of the present invention configured as described above, it is easy to emit electrons from the tip of the microprotrusions. As a result, power consumption in the ion source is reduced, ionization efficiency is improved, and good plasma is obtained.
Further, if the cathode electrode or a part of the cathode electrode is a field emission source that supplies electrons to the anode electrode by field emission (Claim 7), the electrons necessary for ionization and plasmatization of the source gas can be obtained. It is possible to supply sufficiently, and it is possible to prevent the efficiency of ionization and plasma conversion from being reduced due to the insufficient supply of electrons.

As described above, according to the ion source according to the present invention, the influence of the source gas injected from the minute opening of the anode electrode on the jet gas flow caused by the collision with the cathode electrode and the retention is reduced. Can be made. In addition, the ion source with a small diameter can be obtained with a simple configuration without impairing gas efficiency, and the characteristics of the ion source can be maximized, such as improving the discharge efficiency of neutral gas that is not ionized.
In addition, since the radius of curvature of the tip of the metal pin provided on the cathode electrode or the tip of the minute protrusion provided on the annular electrode is formed to be approximately 100 nm or less, electron emission is facilitated. As a result, electrons can be supplied at a lower inter-electrode voltage than before, so that power consumption in the ion source can be reduced.

<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiments are specific examples of the present invention, and do not limit the technical scope of the present invention.

  FIG. 1 is a schematic diagram of an ion source according to the first embodiment of the present invention. As shown in the figure, the ion source 1 includes a source gas introduction part 2, a cathode electrode 3, an extraction electrode 4, and an anode power source 5 for applying a voltage between the source gas introduction part 2 and the cathode electrode 3 as anode electrodes. An extraction power source 6 for applying a voltage between the cathode electrode 3 and the extraction electrode 4 is provided. The source gas introduction part 2 is provided with a micro-opening 7 smaller than the ion extraction opening 11 of the cathode electrode 3 and a source gas introduction port 8. By applying a voltage between the source gas introduction part 2 and the cathode electrode 3 by the anode power source 5, the source material injected at high pressure from the minute opening 7 of the source gas introduction part 2 toward the ion extraction opening 11 of the cathode electrode 3. The gas is turned into plasma.

  As shown in detail in FIG. 2, the cathode electrode 3 is made of a thick, disc-like metal such as stainless steel, and has an opening 9 having a diameter of about 5 mm for the purpose of gas flow at the center thereof. From the peripheral portion of the internal opening 9, 12 metal pins (cathode electrodes) 10 having a thin needle shape and sharpened toward the center of the opening 9 are arranged at 30 ° intervals. Each metal pin 10 has a thickness of 250 μm or less and the same length, and is supported by the peripheral portion of the internal opening 9 so that the tip does not contact with each other, and the tip of the metal pin 10 is respectively Collectively, a circular ion extraction opening 11 concentric with the circular opening 9 is formed. As a result, the circular opening 9 is partitioned into an opening 12 formed between the central ion extraction opening 11 and the metal pin 10 on the outside. Note that the tip of the metal pin 10 between the ion extraction opening 11 and the opening 12 serves as a discharge generation location, generates electrons, the electrons are accelerated toward the minute opening 7, and collide with the source gas to generate ions. . The ion extraction opening 11 is arranged coaxially with the central axis of the minute opening 7 of the anode electrode 2.

  The extraction electrode 4 is provided with an opening 13 larger than the ion extraction opening 11 of the cathode electrode 3, and is disposed on the opposite side of the source gas introduction part 2 with the cathode electrode 3 interposed therebetween. By applying a voltage to the cathode electrode 3 by the extraction power source 6, ions are generated from the plasma generated between the source gas introduction part (anode electrode) 2 and the cathode electrode 3 through the ion extraction opening 11 of the cathode electrode 3. The ions are extracted and ions are released from the opening 13 of the extraction electrode 4.

  In the ion source 1 having the above configuration, the opening diameter φa of the minute opening 7 of the anode electrode 2 is 50 μm. The opening diameter φd of the opening 9 of the cathode electrode 3 is 5 mm, the opening diameter φb of the ion extraction opening is 200 μm, and the opening ratio is 87%. In this case, the flow of the source gas injected at high pressure from the minute opening 7 of the anode electrode 2 is indicated by an arrow 14 in FIG. The opening diameter φa of the minute opening 7 of the anode electrode 2 is 50 μm, whereas the opening diameter φd of the opening 9 of the cathode electrode 3 is sufficiently large as 5 mm, and the gas ejected from the minute opening 7 is the cathode electrode 3 flows smoothly from the ion extraction opening 11 and the opening 12 of the cathode electrode 3 and the performance of the ion source 1 can be exhibited well. A part of the gas inevitably collides with the tip part (discharge forming part) of the metal pin 10, but it stays between the anode electrode 2 and the cathode electrode 3 because of the high aperture ratio. Because it is exhausted promptly without any impact, there is little effect on the jet gas. In FIG. 2B, the aperture ratio is a value obtained by the aperture ratio = (open area of the ion extraction opening 11 and opening 12) × 100 / (area of the opening 9 of the cathode electrode 3).

  FIG. 3 shows an example in which the metal pins 10 are arranged at intervals of 45 °. Even in the cathode electrode 3 formed in this manner, the gas flow becomes even smoother because the aperture ratio becomes larger.

<< Second Embodiment >>
Next, the cathode electrode of the ion source according to the second embodiment of the present invention will be described with reference to FIGS. In the first embodiment described above, an example in which the metal pin (cathode electrode) 10 is used for the cathode electrode 3 of the ion source has been described. Here, the tip has a curvature, and the radius of curvature is 100 nm. An example using the formed metal pin 10a and the metal pin 10b formed to 10 nm will be described. FIG. 7 is an enlarged view around the tip of the metal pin 10 (10a, 10b), and FIG. 8 is a relationship between the field emission current and the voltage between the electrodes when the metal pins 10a, 10b formed of tungsten are used. It is a graph which shows (current-voltage characteristic). Since the constituent elements of the ion source of this example are the same as the constituent elements of the ion source 1 in the first embodiment described above, the description thereof is omitted, and the same reference numerals are given in the drawing.

ここに，上式（１）のβは電界集中係数，φはカソード電極の電子放出部（例えば電極表面）の物質の仕事関数である。上記電子放出部は，絶縁を保ちながら強電界を印加するために，電界集中計数βを大きくする構造（針状等の構造）を持たせる。今，図７に示すように，先端部が曲率を有するよう形成された前記金属ピン１０の先端部（電子放出部）の曲率半径をｒ，前記先端部と原料ガス導入部２との電極間距離をｄとすると，前記電界集中係数βは以下の式（２）で表すことができる。

上式（１）及び（２）から判るように，金属ピンの先端部（電子放出部）の曲率半径ｒが極小であるほど電界放出電流Ｉが増加し，即ち，前記先端部からの電子の電界放出が容易となる。 First, referring to FIG. 7, when electrons are emitted by field emission (see the description of the background art), the electrons emitted into the space between the metal pin and the source gas introduction part 2 (anode electrode) are shown. The relationship (current-voltage characteristics) between the electron current (field emission current) I and the interelectrode voltage V applied between the electrodes will be described. It is known that the current-voltage characteristic at this time can be approximated by the following equation (1) using the Fowler-Nordheim formula (hereinafter referred to as FN equation).

Here, β in the above equation (1) is the electric field concentration coefficient, and φ is the work function of the substance in the electron emission portion (for example, the electrode surface) of the cathode electrode. The electron emission portion has a structure (a needle-like structure) for increasing the electric field concentration count β in order to apply a strong electric field while maintaining insulation. Now, as shown in FIG. 7, the radius of curvature of the tip portion (electron emission portion) of the metal pin 10 formed so that the tip portion has a curvature is r, and the distance between the electrodes of the tip portion and the source gas introduction portion 2 is as follows. When the distance is d, the electric field concentration factor β can be expressed by the following equation (2).

As can be seen from the above formulas (1) and (2), the field emission current I increases as the radius of curvature r of the tip (electron emission portion) of the metal pin is minimized, that is, the electron emission from the tip is increased. Field emission is facilitated.

Here, the relationship (current-voltage characteristics) between the field emission current I and the interelectrode voltage V when the metal pins 10a and 10b formed of tungsten (work function φ: 4.5 eV) are used for the cathode electrode is shown. It is shown in FIG. The solid line P represents current-voltage characteristics when using a metal pin 10a having a tip radius of curvature of 10 nm, and the solid line Q represents a case using a metal pin 10b having a tip radius of curvature of 100 nm. Current-voltage characteristics, which are expressed using the above formulas (1) and (2), respectively. The inter-electrode distance d is 200 μm. From each solid line P, Q in FIG. 8, the radius of curvature of the tip of the metal pin (electron emission portion) increases, so that the interelectrode voltage for obtaining a constant field emission current I tends to increase. Understandable.
The reason why tungsten is used for the metal pin is that it is a material generally used in an electron microscope or the like. Of course, other carbon materials (including diamond, diamond-like carbon, carbon nanotubes, etc.), transition metal nitrides and carbides may be used as other electron emission materials. Or the said material should just cover the front-end | tip part of the said metal pin at least.

It has been experimentally and empirically found that a current of about 1 μA (1 × 10 ⁻⁶ A) is required to maintain the discharge start and stable discharge from the metal pin 10 (however, the electrode Distance between: 200 μm, using tungsten metal pins). Therefore, when using the metal pin 10a, if the interelectrode voltage applied between the electrodes is set to about 0.6 kV or more from the solid line P in FIG. 8, the discharge starts from the tip of the metal pin 10a. It is sometimes read that an electron current (space charge current) of about 1 μA flows through the space between the electrodes. However, the maximum value of the anode-cathode voltage is about 4 to 5 kV in terms of the insulation structure for high voltage resistance and the restriction on the ion source size. For this reason, in order to emit electrons at the tip of the metal pin or to maintain a stable discharge phenomenon, it is preferable that the radius of curvature of the tip of the metal pin is approximately 100 nm or less (see solid line Q).

As described above, in this example, the metal pins 10 formed so that the tips of all the metal pins have the same curvature are used as the cathode electrode of the ion source, and all of these metal pins 10 are electrons at the start of discharge. The example used for the field emission is described. For example, at least one of the metal pins 10 is used as an electrode for discharge by field emission, and the other metal pin is discharged by secondary electron emission. It may be an embodiment used as an electrode for (see the description of the background art).
In the ion source, when the source gas is first made into plasma, it is desirable to discharge by field emission that emits electrons by applying a high voltage between the electrodes and setting the tip of the cathode electrode to a high electric field. From the viewpoint of ion efficiency of the raw material gas, it is considered good to generate plasma first by the method. However, once the source gas is turned into plasma and ions are extracted from the generated plasma, the discharge by the field emission undesirably consumes power. On the other hand, depending on the atmosphere such as atmospheric pressure, gas pressure, temperature, etc., once the source gas is turned into plasma and ions are extracted from the generated plasma, the source gas collides with the metal pin 10. In some cases, a stable discharge phenomenon may be maintained by releasing secondary electrons. In this case, the voltage applied between the electrodes can be set somewhat lower than the voltage applied during the field emission. In such a case, at least one of the metal pins is used as a field emission electrode, that is, a high voltage electrode, and once the discharge is performed and plasma is generated, the field emission metal pin is used. It is conceivable that the voltage supply line is switched to supply the voltage to the other metal pins so that the secondary electrons can be generated (voltage lower than the voltage required for field emission). . In this case, in order to make the electric field distribution when the above high voltage for field emission is applied substantially axially symmetric, three or more metal pins are used as field emission electrodes, and these metal pins are made axially symmetric. It is desirable to arrange.

  As described above, in this example, the example in which the tip portions of all the metal pins are formed so as to have the same curvature is applied to the cathode electrode of the ion source. The tip of one metal pin may have a curvature, and the radius of curvature of the one tip may be approximately 100 nm or less.

<< Third Embodiment >>
Next, the cathode electrode 15 of the ion source according to the third embodiment of the present invention will be described with reference to FIG. Here, FIG. 4 is a diagram for explaining the cathode electrode 15, wherein a is an overall front view, b is an enlarged view of an E portion of a, and c is a cross-sectional view of b. The ion source of this example is the same as each component of the ion source 1 in the first embodiment described above except for the cathode electrode 15, and therefore, the description thereof is omitted using the same reference numerals. In FIG. 4, the same reference numerals are given.
In the cathode electrode 15 of this example, a large circular opening 17 is formed in a flat cathode electrode plate 16 and an annular cathode electrode 19 having a small diameter is formed by a small ion extraction opening 18 at the same center as the circular opening 17. It is arranged. The cathode electrode plate 16 and the annular cathode electrode 19 are fixed by four 100 μm-thick metal pins 20 in this example. The annular cathode electrode 19 is made of a metal having an outer diameter of 400 μm and an inner diameter of 200 μm. In this example, the aperture ratio is 95%, and when configured as an ion source, the gas flow is smoother than that of the cathode electrode 3 shown in FIGS. The number of the metal pins 20 is not limited to four, and is preferably 3 to 5 in order to obtain a sufficient aperture ratio.
It is also conceivable to use an annular cathode electrode 19a shown in FIG. 9 as the cathode electrode instead of the annular cathode electrode 19. The annular cathode electrode 19a is formed by forming a plurality of needle-like microprojections 21 on the surface 22 (hereinafter referred to as the anode surface 22) of the annular cathode electrode 19 on the source gas introduction part 2 side. The microprotrusions 21 can be easily formed by making micron and smaller processing possible by the recent progress of micromachining technology in the semiconductor element field (refer to Patent Document 2 for details). Thus, by using the annular cathode electrode 19a having the minute projections 21 as the cathode electrode of the ion source 1, the field emission of electrons from the tip of the minute projections 21 is facilitated, and the source gas is formed at the discharge forming location. It is possible to sufficiently supply electrons necessary for ionization and plasma formation. In the second embodiment, the example in which the microprojections 21 are cluttered over the entire anode surface 22 has been described. However, the central axis of the opening 18 of the annular cathode electrode 19a is the center. The minute projections 21 may be arranged in an orderly manner for each predetermined angle. Further, the surface is not limited to the surface of the anode surface 22, and the minute protrusions 21 may be formed on the surface of the opposite surface 23. If the tip of the microprojection 21 has a curvature and the radius of curvature of the tip is approximately 100 nm or less, electrons can be easily emitted, and the same effect as the metal pin 10 described above can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the ion source which concerns on embodiment of this invention, Comprising: a is a general view and b is the A section enlarged view of a. It is explanatory drawing of the cathode electrode which concerns on this invention, Comprising: a is a whole front view, b is the B section enlarged view of a, c is sectional drawing of b, d is C section enlarged view of b. It is explanatory drawing of the cathode electrode of another form which concerns on this invention, Comprising: a is an enlarged front view of a center part, b is the D section enlarged view of a. It is explanatory drawing of the cathode electrode of another form which concerns on this invention, Comprising: a is a whole front view, b is the E section enlarged view of a, c is sectional drawing of b. It is a schematic diagram of a conventional ion source, where a is an overall view, b is an enlarged view of the F portion of a, and c is an enlarged view of the G portion of b. Explanatory drawing of the gas flow in the conventional ion source. The enlarged view around the front-end | tip part of the metal pin 10 (10a, 10b). The graph which shows the relationship (current-voltage characteristic) of the field emission current when using the metal pins 10a and 10b formed with tungsten, and the voltage between electrodes. It is explanatory drawing of the cathode electrode of another form which concerns on this invention, Comprising: a is a whole perspective view, b is a side view.

Explanation of symbols

1: Ion source 2: Source gas introduction part (anode electrode)
3: Cathode electrode 4: Extraction electrode 5: Anode power supply 6: Extraction power supply 7: Micro opening 8: Source gas introduction port 9: Opening 10: Metal pin 10a: Metal pin (tip radius of curvature: 10 nm)
10a: Metal pin (tip radius of curvature: 100 nm)
11: ion extraction opening 12, 13: opening 14: gas flow arrow 15: cathode electrode 16: cathode electrode plate 17: opening 18: ion extraction opening 19: annular cathode electrode 19a: annular cathode electrode 20: metal pin

Claims (7)

From the anode electrode having fine openings, the source gas high-pressure injection toward the ion extraction aperture of the cathode electrode having a large ion extraction aperture than the minute opening of the anode electrode, between the anode electrode and the cathode electrode In an ion source that is discharged and turned into plasma by a high voltage applied between the cathode electrode, the discharge forming portion including the ion extraction opening is disposed close to the minute opening of the anode electrode, and the ion extraction at the discharge forming portion is performed. An ion source comprising a plurality of gas exhaust openings on an outer peripheral side of the opening. The cathode electrode is formed by a flat cathode electrode plate having a circular opening, and has a sharp pointed tip having the same length with a thickness of 250 μm or less from the periphery of the circular opening toward the center of the opening. A plurality of metal pins at equal intervals, the tip of each metal pin does not contact and is formed in a circular ion extraction opening concentric with the circular opening, and the space between the adjacent metal pins is the The ion source according to claim 1, wherein the ion source is configured as a gas exhaust opening .   The ion source according to claim 2, wherein a tip portion of at least one of the needle-like metal pins has a curvature, and a radius of curvature of the tip portion is approximately 100 nm or less.   The cathode electrode is formed by a flat cathode electrode plate having a circular opening, and an annular electrode having an ion extraction opening at the center of the circular opening has a thickness of 250 microns or less and the same length. The ion source according to claim 1, wherein the ion source is fixed by ˜5 metal pins.   The ion source according to claim 4, wherein minute projections are formed on the entire surface of the annular electrode or the surface on the anode electrode side.   The ion source according to claim 5, wherein a tip portion of at least one of the micro projections has a curvature, and a radius of curvature of the tip portion is approximately 100 nm or less.   The ion source according to any one of claims 1 to 6, wherein the cathode electrode or a part of the cathode electrode is a field emission source for emitting electrons to the anode electrode.

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