Ion milling apparatus and ion milling method

Abstract

The present invention improves the milling speed and lengthen the maintenance cycle of an ion milling device. This ion generating unit of an ion gun comprises: a disk-shaped first cathode 11 and a disk-shaped second cathode 12 provided with an ion beam extraction hole 32, the first cathode and the second cathode being arranged opposite to each other; an anode arranged between the first cathode and the second cathode in a state of being electrically insulated from the first cathode and the second cathode; an ionization chamber 18 which is surrounded by the first cathode, the second cathode, and the anode and into which a gas is supplied from a gas supply mechanism 40; and a magnet 14 that generates a magnetic field in the ionization chamber, wherein the anode has a cylindrical shape with the longitudinal direction thereof being along the central axis of the ion generating unit, and at the inner wall that is in contact with the ionization chamber, a first protrusion is formed toward the central axis in a range from a position that is equidistant from both ends of the anode to the end opposite the first cathode.

Description

Technical Field

[0001] The present invention relates to an ion milling apparatus for creating a sample to be observed with a scanning electron microscope, a transmission electron microscope, or the like, and an ion milling method using the same.

Background Art

[0002] The ion milling method is a processing method that uses a sputtering phenomenon in which accelerated ions collide with a sample and the ions eject atoms and molecules to cut the sample. In addition, for the sample to be processed, a mask that serves as a shielding plate for the ion beam is placed on the upper surface, and a smooth cross-section can be processed by sputtering the protruding portion from the end face of the mask. This method is used for metals, glass, ceramics, electronic components, composite materials, and the like.

[0003] For example, in electronic components, it is used for applications such as analyzing internal structures, cross-sectional shapes, film thickness evaluation, crystal states, faults, and foreign object cross-sections. It is also used as a method for creating a cross-section sample for obtaining morphological images, sample composition images, channeling images, X-ray analysis, crystal orientation analysis, etc. by various measuring devices including scanning electron microscopes.

[0004] In such an ion milling apparatus, there is one in which a Penning discharge type ion gun with a simple configuration and small size is used as the ion gun. The basic structure of the Penning discharge type ion gun includes a gas supply mechanism for supplying gas into the ion gun, an anode disposed inside the ion gun to which a positive voltage is applied, a cathode for generating a potential difference with the anode, and a magnet. The Penning type ion gun is characterized in that a high milling speed can be obtained due to the large energy of the ion beam.

[0005] Patent Document 1 discloses a method of always maintaining the current value of the ion beam emitted from the ion gun at the maximum value in order to maintain a high milling speed.

[0006] In addition, Patent Document 2 discloses a method of controlling the region of an ionization chamber within a range in which ions can be emitted from an ion gun without colliding with the peripheral portion of the acceleration electrode outlet hole by using a magnet having a specific magnetic flux density and ideally forming the profile of an ion beam in order to increase the amount of ions emitted from the ion gun.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] With the recent progress of ion milling apparatuses, the market has been expanding significantly. For this reason, depending on the application field, the development of an ion gun capable of obtaining a higher milling speed than before is desired. As an example, analysis of three-dimensional mounting using a silicon through electrode (TSV: Through Silicon Via) attracting attention in the semiconductor field can be mentioned. When processing a stacked thick film sample, there is a problem that it takes a long time for processing at the conventional milling speed, which reduces the operating rate of the apparatus. In addition, in the case of an ion gun using a Penning discharge method, due to its mechanism, some of the ions generated inside head toward the cathode disposed opposite to the beam outlet, and the cathode is damaged by colliding with the cathode, resulting in a problem of reduced processing stability.

Means for Solving the Problems

[0009] An ion milling apparatus according to an embodiment of the present invention includes an ion generation unit and a gas supply mechanism that supplies gas to the ion generation unit, an ion gun that accelerates the ions generated by the ion generation unit and emits them as an ion beam, and a sample stage on which a sample irradiated with the ion beam from the ion gun is placed. The ion generation unit of the ion gun includes a disk-shaped first cathode and a disk-shaped second cathode provided with an ion beam extraction hole, which are arranged opposite to each other, and an anode arranged between the first cathode and the second cathode in a state of being electrically insulated from the first cathode and the second cathode. An ionization chamber surrounded by the first cathode, the second cathode, and the anode and supplied with gas from a gas supply mechanism, and a magnet that generates a magnetic field in the ionization chamber. The anode has a cylindrical shape with the direction along the central axis of the ion generation unit as the longitudinal direction. On the inner wall in contact with the ionization chamber, a first protrusion is formed in a range from a position equidistant from both ends of the anode to the end facing the first cathode.

Advantages of the Invention

[0010] It is possible to improve the milling speed by the ion milling apparatus and lengthen the maintenance cycle. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is an explanatory diagram showing the configuration of an ion milling apparatus. A so-called Penning discharge type or an ion gun 1 having a shape similar thereto has components necessary for generating ions disposed therein, and forms an irradiation system for irradiating a non-focused ion beam 2 onto a sample 6. Next, a gas source 201 is connected to the ion gun 1 via a gas supply mechanism 200, and a gas flow rate controlled by the gas supply mechanism 40 is supplied into the ionization chamber of the ion gun 1. The irradiation of the ion beam 2 and its ion beam current are controlled by an ion gun control unit 3. The vacuum chamber 4 is controlled to atmospheric pressure or vacuum by a vacuum exhaust system 5. The sample 6 is held on a sample stage 7, and the sample stage 7 is held by a sample stage 8. The sample stage 8 can be pulled out of the vacuum chamber 4 when the vacuum chamber 4 is opened to the atmosphere, and includes mechanical elements for tilting the sample 6 at an arbitrary angle with respect to the optical axis of the ion beam 2. The sample stage drive unit 9 can swing the sample stage 8 left and right and control its speed.

[0014] FIG. 2 is a diagram showing the configuration of a cross-section of an ion gun of a comparative example and the surrounding parts related thereto. The ion gun in FIG. 2 is an example including an anode having a shape schematically disclosed in Patent Document 1 as anode 500. First, the structure and operation of a Penning discharge type ion gun will be described using the ion gun shown in FIG. 2 as an example.

[0015] The first cathode 11 is formed in a disk shape of a conductive magnetic material such as pure iron, and is provided with holes for introducing gas into the ionization chamber 18 and holes for passing through anode pins (not shown) for supplying power to the anode 500. The magnet 14 is formed in a cylindrical shape, and one end of the magnet 14 is connected to the first cathode 11 made of a magnetic material. The second cathode 12 is formed in a disk shape of a conductive magnetic material such as pure iron, and a cathode exit hole 32 serving as an ion beam extraction hole is provided at the center. The diameter of the cathode exit hole 32 is, for example, 5 mm. The second cathode 12 is connected to the other end of the magnet 14, and a magnetic field is generated in the ion gun 1 by forming a magnetic path with the first cathode 11, the magnet 14, and the second cathode 12. It is desirable to use a samacoba magnet, which is a permanent magnet, for the magnet 14. Note that the magnet 14 is not limited to a permanent magnet, and an electromagnetic magnet may be used as the magnet 14 to generate a magnetic field. The insulator 16 formed in a cylindrical shape is disposed inside the magnet 14, and the outer surface of the insulator 16 is in contact with the inner surface of the magnet 14. The insulator 16 is formed of a non-magnetic material having electrical insulation properties such as ceramics. The anode 500 is fitted inside the insulator 16, the outer surface of the anode 500 is in contact with the inner surface of the insulator 16, and the inner surface faces the ionization chamber 18. The anode 500 is formed in a cylindrical shape of a non-magnetic material having conductivity such as aluminum. The anode 500 is electrically insulated from the first cathode 11, the second cathode 12, and the magnet 14 by the insulator 16. The acceleration electrode 15 is formed in a cylindrical shape of a non-magnetic material having conductivity such as stainless steel, and an acceleration electrode exit hole 33 serving as an ion beam extraction hole is provided at the center. The diameter of the acceleration electrode exit hole 33 is, for example, 5 mm. The acceleration electrode 15 maintained at the ground potential is fixed to the peripheral portion of the ion gun base 17 so as to surround the first cathode 11, the second cathode 12, and the magnet 14. The ion gun base 17 and the first cathode 11 are provided with holes, and for example, Ar gas introduced from the gas supply mechanism 40 is introduced into the ionization chamber 18. Although Ar gas is typical as the gas introduced into the ionization chamber 18, other inert gases may be introduced.

[0016] Among the ion guns, the first cathode 11, the second cathode 12, the magnet 14, the cathode, and the ionization chamber 18 defined by them for generating an electric field and a magnetic field for generating ions are collectively referred to as an ion generation unit. The ion generation unit and the acceleration electrode are arranged to be axisymmetric about the central axis B of the ion generation unit.

[0017] The Ar gas introduced into the ionization chamber 18 is maintained at an appropriate gas partial pressure, and a discharge voltage of about 0 to 4 kV is applied between the first cathode 11, the second cathode 12, and the anode 500 by the discharge power supply 21 to cause glow discharge to generate Ar ions. At this time, due to the presence of the magnet 14, the electrons generated by the discharge can be rotated, the electron orbit can be lengthened, and the discharge efficiency can be increased. Further, an acceleration voltage of about 0 to 10 kV (or more) is applied between the second cathode 12 and the acceleration electrode 15 by the acceleration power supply 22 to accelerate the Ar ions, thereby ejecting the ion beam out of the ion gun. Note that the magnet 14 and the first cathode 11 are electrically connected to the second cathode 12 and are kept at the same potential as the second cathode 12. By such voltage application, electrons are emitted from the surfaces of the first cathode 11 and the second cathode 12, and the emitted electrons are accelerated toward the anode 500. At that time, the electrons emitted from the surfaces of the first cathode 11 and the second cathode 12 have their orbits bent by the magnetic field formed by the first cathode 11, the second cathode 12, and the magnet 14 in the ionization chamber 18 and perform a swirling motion. When the electrons swirling in the ionization chamber 18 collide with the introduced Ar gas, the Ar gas receiving the collision is ionized, and cations are generated in the ionization chamber 18.

[0018] Some of the positive ions generated in the ionization chamber 18 pass through the cathode outlet hole 32 of the second cathode 12, are accelerated by the acceleration electrode 15, and are emitted from the acceleration electrode outlet hole 33 of the acceleration electrode 15 to the outside of the ion gun 1. The sample is processed by an ion beam composed of positive ions. On the other hand, another part of the positive ions generated in the ionization chamber 18 is attracted toward the first cathode 11, collides with the first cathode 11, and damages the first cathode 11.

[0019] As described above, the anode 500 of this comparative example has the shape disclosed in Patent Document 1. That is, the anode 500 has a cylindrical shape with the direction along the central axis B of the ion generation part as the longitudinal direction. On the inner surface of the anode 500 in contact with the ionization chamber 18, a protrusion is formed at the end facing the second cathode 12 toward the central axis B, and the inner diameter of the portion where the protrusion is formed is narrowed.

[0020] FIG. 3 is a diagram showing the cross-section of an ion gun of another comparative example and the configuration of the peripheral part related thereto. The ion gun of FIG. 3 is an example including an anode having the shape disclosed in Patent Document 2 as the anode 501. That is, the anode 501 is formed in a cylindrical shape of a non-magnetic material having conductivity such as aluminum. The anode 501 is not formed with a protrusion as in Comparative Example 1 and has a flat inner wall with respect to the central axis B of the ion generation part. In this comparative example and the embodiments described later, the structure and operation as an ion gun are the same as those described in FIG. 2, so duplicate explanations are omitted.

[0021] FIG. 4 is a diagram showing the electron orbit analysis result and the ion orbit analysis result in the ion gun of the comparative example. Comparative Example 1 is an ion gun having the anode shape shown in FIG. 2, and its analysis results are analysis results 101a and 101b. Comparative Example 2 is an ion gun having the anode shape shown in FIG. 3, and its analysis results are analysis results 102a and 102b. For comparison, simulations are performed with the same conditions except for the anode shape. The size of the ion gun used in the simulation is shown in analysis result 102a.

[0022] The electron trajectory in the ion gun is obtained by calculating the electric and magnetic fields generated inside the ion gun. From the electron trajectory analysis, an electron concentration point where electrons generated inside the ion gun are concentrated at a higher density is found. The electron concentration point is shown to be at a distance of 12.9 mm from the bottom surface of the first cathode in the analysis result 101a according to Comparative Example 1, and at a distance of 11.5 mm from the bottom surface of the first cathode in the analysis result 102a according to Comparative Example 2. The bottom surface of the first cathode refers to the surface facing the surface in contact with the ionization chamber 18 of the first cathode 11. In FIG. 4, with the bottom surface of the first cathode as the reference position (0 mm), a coordinate system along the central axis B of the ion generation unit is also shown.

[0023] The ion trajectory in the ion gun is also obtained by calculating the electric and magnetic fields generated inside the ion gun. The ion trajectory analysis shows the region where ions generated inside the ion gun are emitted from the 100% acceleration electrode exit hole 33. From the analysis result 101b according to Comparative Example 1, ions generated in the region on the side of the second cathode 12 beyond a distance of 13.6 mm from the bottom surface of the first cathode are emitted to the outside. From the analysis result 102b according to Comparative Example 2, it is shown that ions generated in the region on the side of the second cathode 12 beyond a distance of 12.5 mm from the bottom surface of the first cathode are emitted to the outside. This means that ions generated on the side of the first cathode 11 beyond a distance of 13.6 mm from the bottom surface of the first cathode in Comparative Example 1 and ions generated on the side of the first cathode 11 beyond a distance of 12.5 mm from the bottom surface of the first cathode in Comparative Example 2 mainly collide inside the ion gun and contribute to damaging the cathode and the like.

[0024] FIG. 5 is a diagram showing the shape of the beam mark formed on the sample when machining is performed under the same conditions by an ion milling apparatus equipped with the ion gun of the comparative example. The beam mark 111 has the shape of the beam mark of Comparative Example 1, and its depth is about 75 μm. The beam mark 112 has the shape of the beam mark of Comparative Example 2, and its depth is about 155 μm. Thus, in Comparative Example 2, a machining depth approximately twice that of Comparative Example 1 is obtained.

[0025] From the above, in Comparative Example 2, the electron concentration point is shifted by 1.4 mm (from 12.9 mm to 11.5 mm) more toward the first cathode 11 than in Comparative Example 1, and the deepest part of the ion emission position is shifted by 1.1 mm (from 13.6 mm to 12.5 mm) more toward the first cathode 11 than in Comparative Example 1. It can be said that this has resulted in a machining depth that is approximately twice as large. Since ions generated by the collision of electrons and argon gas are generated at a high concentration in the vicinity of the electron concentration point, in Comparative Example 2, both the electron concentration point and the ion emission position are shifted toward the first cathode 11, and it is considered that an extremely large amount of ions are emitted from an ion emission range that is larger than that in Comparative Example 1.

[0026] Here, since the anode is formed of a non-magnetic material, there is no difference in the magnetic field generated in the ion generation part between Comparative Example 1 and Comparative Example 2. Therefore, what brings about the above-described changes is an electric field that has changed due to the anode shape. The inner wall of the anode in Comparative Example 2 is flat with respect to the central axis B of the ion generation part, whereas the anode in Comparative Example 1 generates a strong potential gradient in the direction of the central axis B in the ionization chamber 18 due to the protrusion formed at the end on the side of the second cathode 12. Based on the above findings, in the present embodiment, protrusions are formed on the inner wall of the anode in the range from a position equidistant from both ends of the anode toward the central axis B to the end facing the first cathode. As a result, in the present embodiment, both the electron concentration point and the ion emission position can be shifted further toward the first cathode 11 than in the comparative example, and it becomes possible to emit an extremely large amount of ions from an ion emission range that is larger than in the comparative example. At the same time, this makes it possible to reduce the amount of ions that collide with the components inside the ion gun.

[0027] FIG. 6 is a diagram showing the configuration of a peripheral portion related to the cross-section of the ion gun of the example (Example 1). The anode 600 is formed of a non-magnetic material having conductivity such as aluminum, for example. In this example, the anode 600 has a cylindrical shape with the longitudinal direction along the central axis B of the ion generation unit. On the inner surface of the anode 600 in contact with the ionization chamber 18, protrusions are formed at the end facing the first cathode 11 toward the central axis B, and the inner diameter of the portion where the protrusions are formed is narrowed. For example, the inner diameter of the end of the anode 600 facing the second cathode 12 is set to 6 mm, which is larger than the diameter (5 mm) of the cathode outlet hole 32 of the second cathode 12. On the other hand, at the end facing the first cathode 11, protrusions having a width of, for example, 1 mm and a height of 1 mm are formed toward the central axis B of the ion generation unit, so that the inner diameter of the portion where the protrusions are formed is 4 mm. Here, the size in the direction along the central axis B of the ion generation unit is referred to as the width, and the size in the direction orthogonal to the central axis B is referred to as the height.

[0028] FIG. 7 is a diagram showing the configuration of a peripheral portion related to the cross-section of the ion gun of another example (Example 2). The anode 700 is formed of a non-magnetic material having conductivity such as aluminum, for example. In this example, the anode 700 has a cylindrical shape with the longitudinal direction along the central axis B of the ion generation unit. On the inner surface of the anode 700 in contact with the ionization chamber 18, protrusions are formed at the end facing the first cathode 11 toward the central axis B, and the inner diameter of the portion where the protrusions are formed is narrowed. For example, the inner diameter of the end of the anode 700 facing the second cathode 12 is set to 8 mm, which is larger than the diameter (5 mm) of the cathode outlet hole 32 of the second cathode 12. On the other hand, at the end facing the first cathode 11, protrusions having a width of, for example, 3 mm and a height of 1 mm are formed toward the central axis B of the ion generation unit, so that the inner diameter of the portion where the protrusions are formed is 4 mm.

[0029] FIG. 8 is a diagram showing the electron trajectory analysis result and the ion trajectory analysis result in the ion gun of the embodiment. Example 1 is an ion gun having the anode shape shown in FIG. 6, and the analysis results are analysis results 103a and 103b. Example 2 is an ion gun having the anode shape shown in FIG. 7, and the analysis results are analysis results 104a and 104b. For comparison, simulations are performed with the same analysis as shown in FIG. 4 except for the anode shape.

[0030] It was shown that the electron focus point is at a distance of 10.9 mm from the bottom surface of the first cathode in the analysis result 103a according to Example 1, and at a distance of 9.9 mm from the bottom surface of the first cathode in the analysis result 104a according to Example 2. Further, from the analysis result 103b according to Example 1, ions generated in the region on the second cathode 12 side are emitted to the outside from a distance of more than 11.8 mm from the bottom surface of the first cathode, and from the analysis result 104b according to Example 2, ions generated in the region on the second cathode 12 side are emitted to the outside from a distance of more than 10.7 mm from the bottom surface of the first cathode.

[0031] Thus, in both Example 1 and Example 2, the deepest parts of the electron focus point and the ion emission position are shifted toward the first cathode 11 side compared with the comparative example, and a significantly larger amount of ions can be emitted from the enlarged ion emission range compared with the comparative example, and the milling speed can be improved compared with the comparative example. At the same time, in the comparative example, the ions that collided with the first cathode 11 are emitted to the outside, so that the damage to the first cathode 11 can be reduced, and the maintenance cycle can be lengthened.

[0032] FIG. 9 shows an example of the anode 600 of the embodiment. A plan view 601 and a cross-sectional view 602 taken along line AA are shown. At an end of the anode 600 facing the first cathode 11, a protrusion 650 having a width of 1 mm and a height of 1 mm is formed toward the central axis B of the ion generation section. Due to the protrusion 650, the inner diameter of the end of the anode 600 facing the first cathode 11 is made smaller than the inner diameter of the end facing the second cathode 12. In the example of FIG. 9, the protrusions 650 are formed continuously in a circumferential shape. Although an example of Example 1 is shown, the protrusions of Example 2 can be formed in the same manner.

[0033] FIG. 10 shows another example of the anode 600 of the embodiment. A plan view 603 and a cross-sectional view 604 taken along line AA are shown. In the example of FIG. 10, in the protrusion 660, a plurality of protrusions are formed at predetermined intervals in a circumferential shape. The protrusions provided on the anode 600 also become an obstacle to introducing Ar gas or electrons into the ionization chamber 18 in order to narrow the inner diameter of the anode 600. Therefore, as shown in FIG. 10, by forming the protrusions provided on the anode 600 discontinuously in a circumferential shape, it becomes easier to introduce Ar gas or electrons into the ionization chamber 18 than the protrusions formed continuously in a circumferential shape. Although an example of Example 1 is shown, the protrusions of Example 2 can be formed in the same manner.

[0034] The following shows a modified example of the ion gun of the embodiment.

[0035] FIG. 11 is a diagram showing the cross-section of the ion gun (modified example 1) of the embodiment and the configuration of the peripheral part related thereto. The anode 800 is formed of a non-magnetic material having conductivity such as aluminum, for example. In modified example 1, the anode 800 (length 9.5 mm) has a cylindrical shape with the direction along the central axis B of the ion generation section as the longitudinal direction, and on the inner surface of the anode 800 in contact with the ionization chamber 18, protrusions are formed at a position 2 mm from the end facing the first cathode 11 toward the central axis B, and the inner diameter of the portion where the protrusions are formed is narrowed. For example, the inner diameter of the end of the anode 800 facing the second cathode 12 is 6 mm, which is larger than the diameter (5 mm) of the cathode outlet hole 32 of the second cathode 12, while the inner diameter of the portion where the protrusions are formed is 4 mm.

[0036]

[0036] The manufacturing process of the anode 800 is more complex than that of the anodes in Examples 1 and 2. However, by providing protrusions in the range from the position equidistant from both ends of the anode 800 to the end facing the first cathode 11, it is possible to obtain the effect of shifting the electron concentration point and the ion emission position toward the first cathode 11 side.

[0037]

[0037] FIG. 12 is a diagram showing the configuration of the peripheral part related to the cross section of the ion gun of the Example (Modification 2). The anode 900 is formed of a non-magnetic material having conductivity such as aluminum, for example. In Modification 2, the anode 900 has a cylindrical shape with the direction along the central axis B of the ion generation part as the longitudinal direction. On the inner surface of the anode 900 in contact with the ionization chamber 18, protrusions are formed at both ends toward the central axis B, and the inner diameter of the portion where the protrusions are formed is narrowed. For example, by setting the height of the protrusion at the end facing the first cathode 11 to 1 mm and the height of the protrusion at the end facing the second cathode 12 to 0.5 mm, the inner diameter of the portion of the anode 900 where no protrusion is provided is 6 mm, the inner diameter of the end facing the second cathode 12 is 5 mm, while the inner diameter of the end facing the first cathode 11 is 4 mm. Even if protrusions are provided on the side facing the second cathode 12, the protrusions provided on the side facing the first cathode 11 generate a stronger potential gradient in the direction of the central axis B of the ion generation part, so that the effect of shifting the electron concentration point and the ion emission position toward the first cathode 11 side can be obtained.

[0038]

[0038] In addition, the shape of the protrusions in the above modifications may be a circumferentially continuous shape as shown in FIG. 9, or a circumferentially discontinuous shape as shown in FIG. 10.

[0039] FIG. 13 is a diagram showing the configuration of the peripheral part related to the cross section of the ion gun of the embodiment (Modification 3). The anode 1000 is formed of a non-magnetic material having conductivity such as aluminum, for example. In Modification 3, the inner diameter of the end of the anode 1000 facing the first cathode 11 is made smaller than the inner diameter of the end facing the second cathode 12, and the inner wall of the anode 1000 is formed so as to continuously connect the opening of the end facing the first cathode 11 and the opening of the end facing the second cathode 12. As shown in FIG. 13, it may be connected so that the cross section of the inner wall by the plane including the central axis B of the ion generation part becomes a straight line, or it may be connected so that the cross section of the inner wall becomes a curve. Even with such a shape, the effect of shifting the electron concentration point and the ion emission position to the first cathode 11 side can be obtained.

[0040] As described above, the present invention has been specifically described based on the embodiments and modifications, but the present invention is not limited to this, and various modifications can be made without departing from the gist thereof. Further, the effects can also be obtained by applying each embodiment and modification not alone but in combination.

Explanation of Reference Numerals

[0041] 1: Ion gun, 2: Ion beam, 3: Ion gun control unit, 4: Vacuum chamber, 5: Vacuum exhaust system, 6: Sample, 7: Sample stage, 8: Sample stage, 9: Sample stage drive unit, 11: First cathode, 12: Second cathode, 14: Magnet, 15: Accelerating electrode, 16: Insulator, 17: Ion gun base, 18: Ionization chamber, 21: Discharge power supply, 22: Accelerating power supply, 32: Cathode outlet hole, 33: Accelerating electrode outlet hole, 40: Gas supply mechanism, 101a, 101b, 102a, 102b, 103a, 103b, 104a, 104b: Analysis results, 111, 112: Beam marks, 200: Gas supply mechanism, 201: Gas source, 500, 501, 600, 700, 800, 900, 1000: Anode, 601, 603: Plan view, 602, 604: Cross-sectional view, 650, 660: Projection.

Claims

1. An ion gun including an ion generation unit and a gas supply mechanism for supplying gas to the ion generation unit, the ion gun accelerating the ions generated by the ion generation unit and emitting them as an ion beam, and a sample stage on which a sample irradiated with the ion beam from the ion gun is placed, wherein the ion generation unit of the ion gun includes a disk-shaped first cathode and a disk-shaped second cathode provided with an ion beam extraction hole, which are arranged to face each other, an anode disposed between the first cathode and the second cathode while being electrically insulated from the first cathode and the second cathode, an ionization chamber surrounded by the first cathode, the second cathode, and the anode, and supplied with gas from the gas supply mechanism, and a magnet for generating a magnetic field in the ionization chamber; the anode has a cylindrical shape with a longitudinal direction along the central axis of the ion generation unit, and on the inner wall in contact with the ionization chamber, first protrusions are formed in a range from positions equidistant from both ends of the anode toward the end facing the first cathode up to the end facing the first cathode.

2. According to claim 1, the first protrusion of the anode is formed at the end facing the first cathode.

3. According to claim 1, on the inner wall of the anode in contact with the ionization chamber, second protrusions are formed at the end facing the second cathode, and the height of the first protrusion is higher than the height of the second protrusion.

4. According to any one of claims 1 to 3, the first protrusion is formed continuously in a circumferential shape.

5. In any one of claims 1 to 3, the first protrusion is an ion milling device in which a plurality of protrusions are formed circumferentially at predetermined intervals.

6. In any one of claims 1 to 3, an ion milling device in which an inner diameter at an end of the anode facing the second cathode is equal to or greater than a diameter of an ion beam extraction hole of the second cathode.

7. an ion gun including an ion generation unit and a gas supply mechanism that supplies gas to the ion generation unit, and accelerating ions generated by the ion generation unit to emit them as an ion beam, a sample stage on which a sample irradiated with the ion beam from the ion gun is placed, the ion generation unit of the ion gun, a disk-shaped first cathode and a disk-shaped second cathode provided with an ion beam extraction hole, which are arranged to face each other, an anode disposed between the first cathode and the second cathode while being electrically insulated from the first cathode and the second cathode, an ionization chamber surrounded by the first cathode, the second cathode, and the anode, and supplied with gas from the gas supply mechanism, a magnet that generates a magnetic field in the ionization chamber, the anode has a cylindrical shape with a longitudinal direction along a central axis of the ion generation unit, an inner diameter at an end facing the first cathode is smaller than an inner diameter at an end facing the second cathode, and an inner wall of the anode in contact with the ionization chamber is formed to continuously connect an opening at an end facing the first cathode and an opening at an end facing the second cathode. The ion milling device is as described above.

8. In claim 7, an ion milling device in which a cross section of the inner wall of the anode by a plane including the central axis is linear.

9. In any one of Claim 7 or Claim 8, An ion milling apparatus in which an inner diameter at an end of the anode facing the second cathode is larger than a diameter of the ion beam extraction hole of the second cathode.

10. An ion milling method for processing a sample using an ion milling apparatus having an ion gun including an ion generation unit, an acceleration electrode, a discharge power source, an acceleration power source, and a gas supply mechanism, and a sample stage, The ion generation unit of the ion gun includes a disk-shaped first cathode and a disk-shaped second cathode provided with an ion beam extraction hole, which are arranged to face each other, and an anode arranged between the first cathode and the second cathode in a state of being electrically insulated from the first cathode and the second cathode, an ionization chamber surrounded by the first cathode, the second cathode, and the anode, and a magnet that generates a magnetic field in the ionization chamber. The anode has a cylindrical shape with a longitudinal direction along the central axis of the ion generation unit. On an inner wall in contact with the ionization chamber, protrusions are formed in a range from positions equidistant from both ends of the anode toward the first cathode up to an end facing the first cathode. The acceleration power source applies an acceleration voltage that becomes a positive voltage to the second cathode with respect to the acceleration electrode. The discharge power source applies a discharge voltage that becomes a positive voltage to the anode with respect to the first cathode and the second cathode. The gas supply mechanism supplies gas to the ionization chamber of the ion generation unit. An ion milling method for processing the sample placed on the sample stage with an ion beam emitted from the ion gun.

11. In Claim 10, An ion milling method in which the acceleration electrode of the ion gun is set to a ground potential.

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