JP6499505B2 - Mask, method of using mask, and ion milling apparatus provided with mask - Google Patents

Description

  The present invention relates to a mask used for forming a cross section of a sample by an ion beam, a method of using the mask, and an ion milling apparatus including the mask.

  The ion milling apparatus is an apparatus that uses a sputtering phenomenon in which ions are accelerated to irradiate a sample and atoms of the sample are blown off from the surface of the sample. As a method of cutting a sample with an ion milling apparatus, there are a planar milling method and a cross-sectional milling method. Among these, the cross-sectional milling method is a method in which a mask is disposed between an ion gun and a sample, and the sample is projected from the mask by about 50 to 200 μm to perform ion milling of a portion protruding from the end face of the mask. This is a processing method for producing a cross section. The surface of the sample cut by the cross-sectional milling method is very smooth and has the feature that the destruction of the structure and structure is extremely small. Therefore, the cross-sectional milling method is widely used in various fields such as the material field and the device field as a method for preparing a sample of a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Yes.

  As described above, when the cross-sectional milling method is performed, a mask is disposed between the ion gun and the sample in the ion milling apparatus. The mask is made of a material (composition) with a sputtering yield smaller than that of the sample, that is, a material that is harder to be cut by the ion beam than the sample to be ion milled. Gradually scraped. Recently, it is required to perform ion milling over a wide range as a sample for an electron microscope of about several centimeters. In order to perform ion milling over a wide range, a long milling process using an ion gun corresponding to a high milling speed is required. The mask needs to have a high milling speed and resistance to shield the sample from the ion beam during a long milling process. The resistance to shielding from the ion beam specifically refers to the amount of the mask that can be milled and scraped by the ion beam up to the lower surface of the mask end surface irradiated with the ion beam, This means that it is below the processing accuracy of the sample (that is, it is harder to cut than the sample). The degree to which the mask is shaved by the ion beam is determined by the intensity of the ion beam to be irradiated (can be approximated by arithmetic operation of the type of ion beam, the acceleration voltage of the ion beam, the number of ions), the irradiation angle of the ion beam, and the mask Depends on material and composition.

Under such circumstances, for example, Patent Document 1 discloses an ion milling apparatus and a mask used therefor.
Specifically, Patent Document 1 describes a gas supply source that supplies gas to the inside of an ion gun, an anode that is disposed inside the ion gun and to which a positive voltage is applied, and the anode. In an ion milling apparatus including a cathode that generates ions by generating a potential difference therebetween, the cathode separates a space in which a gas is supplied from the gas supply source and a space on the sample side to which the ions are irradiated. An ion milling device is provided that includes an opening that pressurizes and allows the ions to pass therethrough and that accelerates the ions that have passed through the opening toward the sample. Patent Document 1 describes that a mask is made of a metal material such as titanium or molybdenum, or is made of carbon graphite.

JP 2012-156077 A

However, when the mask is formed of a material as described in Patent Document 1, the following points are concerned.
For example, when the mask is formed of a metal material such as titanium or molybdenum, the mask is likely to be scraped by an ion beam and tends to have a short lifetime.
For example, when the mask is made of carbon graphite, it is difficult to be scraped off by an ion beam, but due to the nature of the material, it is easily broken and difficult to handle.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a mask that is difficult to be scraped by an ion beam and that is easy to handle, a method of using the mask, and an ion milling apparatus including the mask. .

  The mask according to the present invention that has solved the above-described problem is a mask used in an ion milling apparatus that includes a sample stage for fixing a sample and an ion gun that irradiates an ion beam toward the sample. The sample and the ion gun Between the metal and carbon, with the balance being tungsten and an alloy of inevitable impurities.

  A method of using a mask according to the present invention includes: a sample stage for fixing a sample; and an ion mill that irradiates an ion beam toward the sample. In addition, a mask formed of an alloy containing carbon and the balance being tungsten and an inevitable impurity is disposed, and then the sample is processed by irradiating the sample with the ion beam.

  An ion milling apparatus according to the present invention includes a sample stage for fixing a sample, and an ion gun that irradiates an ion beam toward the sample, and includes carbon between the sample and the ion gun, with the balance being tungsten. And a mask formed of an alloy which is an inevitable impurity.

  ADVANTAGE OF THE INVENTION According to this invention, the ion milling apparatus provided with the mask which is hard to be scraped by an ion beam, and is easy to handle, the usage method of a mask, and a mask can be provided.

It is a schematic block diagram explaining the structure of an ion milling apparatus. It is a schematic sectional drawing which shows the one aspect | mode of the mask which concerns on this invention. It is a graph which shows the result of having compared the depth amount which can be shaved by irradiating an ion beam for a predetermined time with respect to the mask made from pure titanium as an example of the mask which concerns on this invention, and the mask used conventionally. The horizontal axis represents the ion beam irradiation time, and the vertical axis represents the amount of cutting depth. It is the optical microscope photograph of the mask which concerns on this invention at the time of A time passage shown in FIG. 3, the time of B time passage, and C time passage, and the mask made from a pure titanium.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Embodiments of a mask, a method of using the mask, and an ion milling apparatus including the mask according to the present invention will be described below in detail with reference to the drawings as appropriate.
For convenience of explanation, before describing the mask according to the present invention, an ion milling apparatus used with the mask according to the present invention will be briefly described. FIG. 1 is a schematic configuration diagram illustrating the configuration of the ion milling apparatus.

(Ion milling equipment with mask)
As shown in FIG. 1, the ion milling apparatus 1 includes a vacuum chamber 2. The ion milling apparatus 1 includes a sample stage 3 inside a vacuum chamber 2, and an ion gun 5 so that the ion beam 4 can be irradiated toward the sample stage 3. That is, the ion gun 5 is provided so that the ion beam 4 can be irradiated toward the fixed sample 7 disposed on the sample table 3.

  The ion gun 5 is controlled by an ion gun control unit 6, and on / off of irradiation of the ion beam 4, beam output (current density), beam irradiation time, etc. based on an input signal input by an input unit (not shown). Is arbitrarily adjusted. The ion gun control unit 6 is connected to the discharge power source and the acceleration power source, and controls the discharge voltage and the acceleration voltage. Examples of the ion beam 4 include, but are not limited to, an argon ion beam. Any ion can be used as long as the cross section of the sample 7 can be processed (produced) by a sputtering phenomenon. Beams can also be used.

Although details will be described later, the sample 7 is arranged at a predetermined position between the sample stage 3 and the mask 8 according to the present invention.
Although details of the mask 8 will be described later, the mask 8 is disposed between the sample stage 3 and the ion gun 5 (more specifically, between the sample 7 and the ion gun 5). The mask 8 can be moved freely in the direction close to and away from the sample table 3 by the mask holder 9. When the mask holder 9 is operated to move the mask 8 in the direction approaching the sample table 3, the mask 8 can be fixed so as to press the sample 7.
In this state, the mask 8 shields at least a part of the ion beam 4 irradiated to the sample 7 (more specifically, near the boundary between the sample 7 fixed to the sample stage 3 and the mask 8), and the ion beam 4 is shielded from the sample. A flat cross section along the end face of the mask 8 is produced by cutting a part of 7.
The sample 7 may be fixed so that the end of the sample 7 protrudes from the mask 8 by about 10 to 200 μm. As described above, the ion beam 4 is irradiated toward the sample stage 3. To be precise, it is preferable that the center of the ion beam 4 corresponds to the sample 7 protruding from the mask 8 by about 10 to 200 μm.

  The operation of projecting the sample 7 from the mask 8 is confirmed by a magnifying observation means (not shown) such as an optical microscope separate from the ion milling apparatus 1, and the sample mask unit fine movement mechanism 10 is used to pass the mask holder 9. This is done by finely moving the mask 8. The sample mask unit fine movement mechanism 10 is detachably attached to the sample unit base 11. FIG. 1 shows a state in which the sample mask unit fine movement mechanism 10 is attached to the sample unit base 11. As shown in FIG. 1, the sample mask unit fine movement mechanism 10 includes the sample stage 3 described above.

The sample unit base 11 is disposed via a sample stage 13 (rotation mechanism) mounted on a flange 12 that also serves as a part of the container wall of the vacuum chamber 2. The sample unit base 11 is configured such that the flange 12 can be pulled out or pushed in along the linear guide 14. That is, the sample unit base 11 is drawn out along the linear guide 14 so that the sample unit base 11 is drawn out of the vacuum chamber 2 when the vacuum chamber 2 is opened to the atmospheric state. When performing ion milling, a sample mask unit fine movement mechanism 10 in which a sample 7 is fixed between the sample table 3 and the mask 8 is attached to the sample unit base 11 and the flange 12 is pushed along the linear guide 14 to thereby form a vacuum chamber. The sample unit base 11 can be accommodated in 2. The positioning of the sample 7 accommodated in the vacuum chamber 2 can be performed by a rotation mechanism (not shown) incorporated in the sample stage 13 and the sample unit base 11.
The ion milling apparatus 1 shown in FIG. 1 includes an evacuation system 15, and the inside of the vacuum chamber 2 can be evacuated or depressurized as necessary. In addition, the ion milling apparatus 1 may include a cooling mechanism (not shown) that cools the sample 7 indirectly via the mask 8.

(mask)
Next, the mask 8 according to the present invention will be described in detail. As described above, the mask 8 according to the present invention is disposed between the sample stage 3 and the ion gun 5, more specifically, between the sample 7 and the ion gun 5.
The mask 8 is made of an alloy containing carbon and the balance being tungsten and inevitable impurities. When such a mask 8 is used, a higher hardness can be obtained as compared with a tungsten cemented carbide containing a binder (binder) such as cobalt or nickel. Further, it can be made difficult to be scraped off by the ion beam 4, and the life of the mask 8 can be extended and the ion beam 4 can be irradiated for a long time. Further, if such a mask 8 is used, it is possible to make the mask 8 easier to handle because it can be made harder to crack than when formed with carbon graphite.

  Further, since the mask 8 has conductivity, the charge due to the ion irradiation is not charged, and the sample 7 can be normally irradiated with the ion beam 4. Further, since the mask 8 is difficult to be scraped by the ion beam 4, redeposition can be suppressed. In addition to these, the mask 8 is mostly composed of tungsten and carbon and has a small number of compositions. Therefore, the energy dispersive X-ray analysis (EDS) and the wavelength dispersive X-ray analysis (Wavelength Dispersive) are used. X-ray spectroscopy (WDS) or the like at the time of composition analysis can reduce the obstruction of analysis due to the overlap between the composition to be analyzed of the sample and the composition derived from the mask.

  Further, although the mask 8 has high hardness, it can be easily mirror-finished compared to a pure titanium mask, and the surface irregularities of the mask 8 can be easily reduced. Therefore, the cross section of the sample 7 can be processed smoothly. Further, since such a mask 8 has a high thermal conductivity, the thermal energy from the ion beam 4 is easily released to the mask holder 9 through the mask 8. Therefore, thermal damage to the sample 7 can be reduced, whereby a clear (smooth) processed cross section can be obtained.

  Further, since the mask 8 has a lower coefficient of thermal expansion than that of a pure titanium mask, the heat fluctuation during processing is reduced by the heat of the ion beam 4. Therefore, the processing accuracy of the sample 7 by the mask 8 can be increased. In addition to the effects described above, since the mask 8 is a non-magnetic material, it is possible to obtain a clear observation image with no image obstruction when observed with an electron microscope.

  The carbon content of the mask 8 is preferably 5 to 12% by mass, for example. When the carbon content is within this range, a high hardness can be obtained more reliably, and therefore it can be made more difficult to be scraped by the ion beam 4. Further, in this way, it is possible to make the mask 8 easier to handle because it can be made more difficult to crack as compared with the case of forming with carbon graphite.

  Examples of unavoidable impurities include O, Cr, and Mo. Since these inevitable impurities do not inhibit the effects of the present invention as long as they are 5% by mass or less in total, they may be contained as long as they are below the contents.

  The mask 8 according to the present invention preferably does not contain cobalt. When the mask 8 is shaved by the ion beam 4, fine particles having a composition that forms the shaved mask 8 are redeposited (redeposition) on the sample 7. Even in such a case, since the mask 8 does not contain cobalt, cobalt is not detected when the composition analysis is performed. Therefore, it is possible to obtain suitable analysis data for composition analysis such as EDS and WDS.

  In general tungsten carbide, cobalt is added as a binder in order to improve toughness. That is, unless it is artificially added, cobalt cannot be contained in such a content that it can be detected by an analyzer or the like. Therefore, it is preferable not to add cobalt when manufacturing the mask 8 according to the present invention. Moreover, since the mask 8 does not contain cobalt, the hardness can be increased as compared with the case where it contains this. Therefore, the resistance to the ion beam 4 can be further improved.

  The mask 8 is preferably a plate material having a predetermined thickness, and the shape in plan view (specifically, the shape perpendicular to the traveling direction of the ion beam 4) is preferably rectangular. However, the shape is not limited to this, and may be a circle, a triangle, a pentagon, a hexagon, or the like.

  The thickness of the mask 8 can be set to 1 to 3 mm, for example. When the thickness of the mask 8 is within this range, the mask 8 can be prevented from being penetrated from the front surface to the back surface by being irradiated with the ion beam 4 while the sample 7 is being processed. Therefore, it is preferable because the sample 7 can be sufficiently processed. If the thickness of the mask 8 is within this range, for example, when ion milling is performed by irradiating the ion beam 4 while indirectly cooling the sample 7 via the mask 8 (hereinafter referred to as cooling milling). The sample 7 can be easily cooled. Note that the thickness of the mask 8 is not limited to the above-described range, and may be less than 1 mm or may be greater than 3 mm.

  The mask 8 has an arithmetic average roughness Ra of 0.1 μm or less of a surface (end surface) that is parallel or substantially parallel to at least an irradiation angle of the ion beam 4 to the sample stage 3 (more specifically, the sample 7). Is preferred. As described above, in the cross-sectional milling method, at least a part of the ion beam 4 irradiated on the sample 7 is shielded, and a part of the sample 7 is cut along the end face of the mask 8. Therefore, the property of the end face of the mask 8, that is, the arithmetic average roughness Ra affects the roughness of the processed surface of the cross section of the sample 7. When the arithmetic average roughness Ra of the end face of the mask 8 is 0.1 μm or less, the cross section of the sample 7 can be made sufficiently smooth for observing with a SEM. In addition, arithmetic mean roughness Ra can be calculated | required based on JISB0601: 2001.

  Moreover, when the ion beam 4 is irradiated to the mask 8, the end surface of the mask 8 is shaved. The mask end face at this time is provided with irregularities according to the grain size of the material in addition to the processing roughness. Therefore, it is desirable that the material of the mask 8 has a particle size of 0.1 μm or less. The particle size of the material of the mask 8 can be reduced to 0.1 μm or less by finely pulverizing the above-described alloy by a bead mill or the like and then removing the particles having a particle size exceeding 0.1 μm with a classifier. .

Here, FIG. 2 is a schematic cross-sectional view showing one aspect of the mask 8.
The mask 8 can have a rising angle θ from the surface 81 in contact with the sample 7 of 90 °. However, as described above, the amount of protrusion of the sample 7 from the mask 8 is adjusted under the optical microscope observation. As shown in FIG. 2, it is preferable to set the rising angle θ to 88.5 to 89.5 ° so that the boundary between the sample 7 and the mask 8 can be focused with a microscope and observation is easy. In FIG. 2, the angle is exaggerated for easy understanding that the end face of the mask 8 is inclined. The mask 8 can obtain high resistance to the ion beam 4 when the rising angle θ from the surface 81 is 90 °. On the other hand, when the rising angle θ is 88.5 to 89.5 °, when the sample 7 is set to protrude about 10 to 200 μm from the mask 8 using the optical microscope, the brightness is sufficient with the optical microscope. The specular reflection from the end face of the illumination mask 8 for observation can be reduced, the contrast is improved, and the boundary between the sample 7 and the mask 8 becomes easy to see. Therefore, with such an angle, the sample 7 can be easily set. Even when the rising angle θ is set to 88.5 to 89.5 °, sufficiently high resistance to the ion beam 4 can be maintained. The rising angle θ is preferably as described above, but is not limited to this, and may be less than 88.5 °.

(How to use the mask)
Next, a method for using the mask according to the present invention will be described. Note that the items described regarding the mask 8 have the same configuration in the method of using the mask according to the present invention, and can achieve the same effects as described above. Therefore, in describing the method of using the mask, detailed description of the mask 8 is omitted.

  The method of using a mask according to the present invention comprises an ion stage 3 that fixes a sample 7 and an ion gun 5 that irradiates an ion beam 4 toward the sample stage 3 (more specifically, toward the sample 7). In the ion milling in the milling apparatus 1, between the sample stage 3 and the ion gun 5 (more specifically, between the sample 7 and the ion gun 5), carbon is contained, and the balance is formed of an alloy of tungsten and inevitable impurities. After the mask 8 is placed, the sample 7 is processed by irradiating the sample stage 3 with the ion beam 4. In detail, it carries out as follows.

  First, the flange 12 is pulled out along the linear guide 14, and the sample mask unit fine movement mechanism 10 is removed from the sample unit base 11. Then, the sample 7 is arranged at a predetermined position between the sample stage 3 and the mask 8 provided in the sample mask unit fine movement mechanism 10. Next, the mask 8 is moved in the direction close to the sample stage 3 by the mask holder 9 to fix the sample 7.

  Subsequently, by using an optical microscope (not shown) separate from the ion milling apparatus 1, the mask 8 is finely moved by the sample mask unit fine movement mechanism 10 through the mask holder 9, whereby the end portion of the sample 7 is moved. About 50 to 200 μm is projected from the mask 8.

  After projecting the end of the sample 7 from the mask 8 by about 50 to 200 μm, the sample mask unit fine movement mechanism 10 is attached to the sample unit base 11. Then, the flange 12 is pushed along the linear guide 14 to seal the vacuum chamber 2. By doing in this way, the sample stage 3, the sample 7, and the mask 8 can each be arrange | positioned in the predetermined position in the vacuum chamber 2. FIG.

  The vacuum evacuation system 15 is operated as necessary, and the inside of the vacuum chamber 2 is evacuated or decompressed, or the cooling means (not shown) is operated to indirectly cool the sample 7 via the mask 8. The ion beam 4 is input based on input signals for controlling the ion beam 4 irradiation ON, the beam output (current density), and the beam irradiation time input to the ion gun controller 6 from an input means (not shown). Is irradiated toward the sample stage 3 (more specifically, the ion beam 4 is irradiated toward the end of the sample 7 set on the sample stage 3 and protruding from the mask 8).

As shown in FIG. 1, the mask 8 shields at least a part of the ion beam 4 irradiated to the sample 7, and the ion beam 4 cuts a part of the sample 7 to produce a cross section. When the ion gun controller 6 receives an input signal of irradiation OFF of the ion beam 4 input from the input means at an arbitrary timing after the cross section is created, or when the irradiation time of the input beam elapses, the ion gun controller 6 finishes irradiation of the sample 7 with the ion beam 4. Then, the cross section of the sample 7 is observed, compositionally analyzed, or the like using SEM, TEM, EDS, WDS, or the like.
Note that the mask 8 is shaved by the irradiation of the ion beam 4, and if it is likely to penetrate from the surface (front surface) irradiated with the ion beam 4 to the back surface, for example, the sample mask unit finely moves. The mechanism 10 finely moves (moves) the mask 8 via the mask holder 9 to shield the ion beam 4 at a portion that is not irradiated with the ion beam 4 or a portion with a small amount cut by the ion beam 4. It is good to do. The fine movement of the mask 8 by the sample mask unit fine movement mechanism 10 may be performed manually by an operator or may be performed by an actuator such as a motor (not shown). The timing of the movement of the mask 8 can be arbitrarily determined based on the knowledge and experience of the operator, but it is preferable to automatically move the mask 8 after a predetermined time has passed by a program or the like. This makes it possible to irradiate the ion beam 4 for a longer time.

When the inside of the vacuum chamber 2 is evacuated or depressurized after the observation or composition analysis is completed, the evacuation system 15 is operated to return the inside of the vacuum chamber 2 to atmospheric pressure. Then, the flange 12 is pulled out along the linear guide 14, and the sample mask unit fine movement mechanism 10 is removed from the sample unit base 11. Next, the mask 8 is moved away from the sample stage 3 by the mask holder 9 to release the fixation of the sample 7, and the sample 7 is taken out between the sample stage 3 and the mask 8.
In this way, a series of operations using the mask 8 is completed (the method of using the mask 8 is finished).

  The sample 7 processed in the method of using the mask 8 according to the present invention is a sample to be observed and analyzed by an electron microscope. For example, a battery electrode, an organic electroluminescence element, a semiconductor substrate, or copper, a copper alloy , Aluminum, aluminum alloy, gold, gold alloy, silver, silver alloy, platinum, platinum alloy, palladium, palladium alloy, rhodium, rhodium alloy, iridium, iridium alloy, ruthenium, ruthenium alloy, osmium or osmium alloy Examples include metal structures, polymer materials, biological samples, and the like. Needless to say, the sample 7 to be processed in the method of using the mask 8 according to the present invention is not limited to the above.

  As an example of the mask 8 according to the present invention, which is made of particles (particle size of 1 μm or less) of an alloy (cobalt is not included) containing tungsten and the balance being tungsten and inevitable impurities, and a conventionally used mask. FIG. 3 shows the result of comparison of the amount of depth that can be cut by irradiating an ion beam for a predetermined time with respect to a pure titanium mask. In addition, the horizontal axis of FIG. 3 shows the irradiation time of an ion beam, and a vertical axis | shaft shows the amount of cutting depths. An argon ion beam was used as the ion beam, and the acceleration voltage was 6 kV.

  As shown in FIG. 3, it was confirmed that the cutting depth amount of the mask 8 was smaller than the cutting depth amount of the mask made of pure titanium at any of the A time, B time, and C time, and it was difficult to cut. . The durability of the mask 8 with respect to the argon ion beam was found to be about 1.8 times that of a pure titanium mask when irradiated with an argon ion beam accelerated at an acceleration voltage of 6 kV for 12 hours, for example.

FIG. 4 shows optical micrographs of the end faces of the mask 8 and the pure titanium mask when the time A, the time B and the time C shown in FIG.
As shown in FIG. 4, when the A time has elapsed, the B time has elapsed, and the C time has elapsed, the cutting depth D of the mask 8 is the net value when the A time has elapsed, the B time has elapsed, and the C time has elapsed. It can be confirmed that the amount is smaller than the cutting depth D of the titanium mask.

As described above, the mask, the method of using the mask, and the ion milling apparatus including the mask according to the embodiment of the present invention have been described in detail. However, the gist of the present invention is not limited thereto, and various modifications are included. It is. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
Each of the above-described configurations, functions, processing units, processing means, control means, and the like may be realized by hardware by designing a part or all of them, for example, with an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

1 Ion milling equipment 2 Vacuum chamber (sample room)
DESCRIPTION OF SYMBOLS 3 Sample stand 4 Ion beam 5 Ion gun 6 Ion gun control part 7 Sample 8 Mask 9 Mask holder 10 Sample mask unit fine movement mechanism 11 Sample unit base 12 Flange 13 Sample stage 14 Linear guide 15 Vacuum exhaust system

Claims (18)

A sample stage for fixing the sample;
An ion gun that irradiates an ion beam toward the sample;
A mask used in an ion milling apparatus comprising:
A mask, which is disposed between the sample and the ion gun, contains carbon, and the balance is formed of tungsten and an alloy of inevitable impurities. In claim 1,
A mask characterized by not containing cobalt. In claim 1 or claim 2,
A mask having a thickness of 1 to 3 mm. In any one of Claims 1-3,
A mask formed by using, as a material, powder of the alloy having a particle size of 1 μm or less. In any one of Claims 1-4,
A mask having an arithmetic average roughness of 0.1 μm or less at least on a surface parallel or substantially parallel to an irradiation angle of the ion beam to the sample. In any one of Claims 1-5,
A mask characterized in that a rising angle from a surface in contact with the sample is 88.5 to 89.5 °. A sample stage for fixing the sample;
In ion milling in an ion milling apparatus comprising an ion gun that irradiates an ion beam toward the sample,
A mask formed of an alloy containing carbon and the balance being tungsten and an inevitable impurity is disposed between the sample and the ion gun, and then the sample is processed by irradiating the ion beam toward the sample. How to use a mask characterized by In claim 7,
A method for using a mask, wherein the mask does not contain cobalt. In claim 7 or claim 8,
A method of using a mask, wherein the mask has a thickness of 1 to 3 mm. In any one of Claims 7-9,
The method of using a mask, wherein the mask is formed using a powder of the alloy having a particle size of 1 μm or less as a material. In any one of Claims 7-10,
A method of using a mask, wherein the mask has an arithmetic average roughness of 0.1 μm or less at least on a surface parallel or substantially parallel to an irradiation angle of the ion beam to the sample. In any one of Claims 7-11,
The mask is characterized in that the rising angle from the surface in contact with the sample is 88.5 to 89.5 °. A sample stage for fixing the sample;
An ion gun for irradiating an ion beam toward the sample,
An ion milling apparatus, wherein a mask formed of an alloy containing carbon and the balance being tungsten and inevitable impurities is disposed between the sample and the ion gun. In claim 13,
The ion milling apparatus, wherein the mask does not contain cobalt. In claim 13 or claim 14,
An ion milling apparatus, wherein the mask has a thickness of 1 to 3 mm. In any one of Claims 13-15,
The ion milling apparatus according to claim 1, wherein the mask is formed by using a powder of the alloy having a particle size of 1 μm or less as a material. In any one of Claims 13-16,
The ion milling apparatus according to claim 1, wherein the mask has an arithmetic average roughness of 0.1 μm or less at least on a surface parallel or substantially parallel to an irradiation angle of the ion beam to the sample. In any one of Claims 13-17,
The ion milling apparatus according to claim 1, wherein a rising angle of the mask from a surface in contact with the sample is 88.5 to 89.5 °.