Ion milling device, inspection system, and sample processing method

Abstract

An ion milling device (100) is capable of processing a sample (6) by: irradiating the sample (6) with a first ion beam that uses Ar; subsequently switching from the first ion beam to a second ion beam that uses a noble gas that has a molecular weight larger than that of Ar; and irradiating the sample 6 with the second ion beam.

Description

Ion milling apparatus, inspection system, and sample processing method

[0001] The present invention relates to an ion milling apparatus, an inspection system including the ion milling apparatus, and a method for processing a sample using the ion milling apparatus.

[0002] In an ion milling system, a sample, such as a semiconductor, metal, glass, or ceramic, is irradiated with an unfocused ion beam accelerated to several kV, which sputters atoms off the surface of the sample without stress. This results in a smooth, machined surface. The smooth, machined surface can be observed using a charged particle beam device such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0003] For example, in Patent Document 1, first, a specimen is extracted from a specimen using a Ga ion beam. Next, an amorphous layer (damaged layer) containing Ga ions is removed using a Xe ion beam. During this removal process, an SEM image is obtained by irradiating the specimen with an electron beam. The presence or absence of Ga ions or the Ga ion content is confirmed from the obtained SEM image. If an amorphous layer remains, the removal process is performed again.

[0004] JP 2017-150840 A

[0005] In ion milling, an amorphous layer is generated by implanting ions into the sample. When analyzing the internal microstructure of a sample using SEM images, a thick amorphous layer reduces the contrast of the SEM image, making analysis of the SEM image difficult. Therefore, ion milling requires processing that minimizes the amorphous layer.

[0006] In processing using an ion milling device, Ar (argon) ions are generally used. For example, an ion beam using Xe (xenon), which has a larger molecular weight than Ar, is less likely to implant ions into the interior of the sample, thereby suppressing the generation of an amorphous layer. However, long-term processing using a Xe ion beam can result in significant unevenness on the processed surface.

[0007] The main objective of the present application is to provide an ion milling apparatus capable of performing ion milling that can suppress the generation of an amorphous layer and reduce the unevenness of the processed surface of a sample. If such an ion milling apparatus can be provided, the contrast of images acquired by a charged particle beam device can be maintained and image analysis can be automated, thereby automating a series of processes from ion milling to image analysis.

[0008] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0009] A brief summary of a representative embodiment of the present invention will be given below.

[0010] In one embodiment, the ion milling apparatus processes a sample by irradiating the sample with an ion beam. The ion milling apparatus processes the sample by irradiating the sample with a first ion beam using Ar, and then switches from the first ion beam to a second ion beam using a noble gas having a molecular weight larger than that of Ar, and irradiates the sample with the second ion beam.

[0011] In one embodiment, a method for processing a sample is performed using an ion milling apparatus, and includes the steps of: (a) irradiating a sample with a first ion beam using Ar to process the sample; (b) after the step (a), switching from the first ion beam to a second ion beam using a noble gas having a molecular weight larger than that of Ar; and (c) after the step (b), irradiating the sample with the second ion beam to process the sample.

[0012] According to one embodiment, an ion milling apparatus can be provided that can perform ion milling that can suppress the generation of an amorphous layer and reduce unevenness on the processed surface of a sample. In addition, a series of processes from ion milling to image analysis can be automated.

[0013] FIG. 1 is a schematic diagram showing an ion milling apparatus in embodiment 1. FIG. 2 is experimental data obtained by the inventors of the present application. FIG. 3 is experimental data obtained by the inventors of the present application. FIG. 4 is experimental data obtained by the inventors of the present application. FIG. 5 is a flowchart showing a sample processing method in embodiment 1. FIG. 6 is a schematic diagram showing an inspection system in embodiment 1. FIG. 7 is a schematic diagram showing an inspection system in embodiment 1. FIG. 8 is a schematic diagram showing an inspection system in embodiment 1. FIG. 9 is a schematic diagram showing an ion milling apparatus in a modified example.

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0015] (Embodiment 1) <Structure of Ion Milling Apparatus> An ion milling apparatus 100 according to embodiment 1 will be described below with reference to Fig. 1. The ion milling apparatus 100 processes a sample by irradiating the sample with an ion beam (ion milling). The ion milling apparatus 100 is also used as a pretreatment apparatus for preparing a sample to be observed with a charged particle beam apparatus such as an SEM or a TEM.

[0016] As shown in FIG. 1 , the ion milling apparatus 100 mainly includes an Ar gas cylinder 1, a regulator 2, a valve 3, a mass flow controller (MFC) 4, an ion gun 5, a Xe gas cylinder 7, a regulator 8, a valve 9, a mass flow controller 10, an ion gun 11, a sample chamber 17, an observation window 20, a shutter 21, a computer 22, a controller 23, a stage control unit 24, an exhaust system control unit 25, a stage 26, a first monitoring mechanism MM1, and a second monitoring mechanism MM2.

[0017] The sample chamber 17 is provided with an ion gun 5 capable of irradiating an Ar ion beam, an ion gun 11 capable of irradiating a Xe ion beam, a stage 26 on which a sample 6 can be placed, and a quartz oscillator 14. The sample 6 is, for example, a semiconductor, a metal, glass, or ceramic.

[0018] It should be noted that, with the sample 6 held by the sample holder HL, the sample holder HL is placed on the stage 26. In the following description, the description of the sample holder HL will be omitted, and it may be expressed simply as "the sample 6 is placed on the stage 26."

[0019] When an ion beam using Ar (Ar ion beam) is irradiated from the ion gun 5, Ar gas is supplied from the Ar gas cylinder 1 to the ion gun 5. The regulator 2 adjusts the pressure of the Ar gas. The flow path of the Ar gas is opened and closed by operating the valve 3. The mass flow controller 4 controls the flow rate of the Ar gas.

[0020] When an ion beam using Xe (Xe ion beam) is irradiated from the ion gun 11, Xe gas is supplied from a Xe gas cylinder 7 to the ion gun 11. A regulator 8 adjusts the pressure of the Xe gas. A flow path for the Xe gas is opened and closed by operating a valve 9. A mass flow controller 10 controls the flow rate of the Xe gas. Note that the gas used in the ion gun 11 is not limited to Xe, and a noble gas having a molecular weight greater than that of Ar may also be used.

[0021] The ion gun 5 and the ion gun 11 are arranged so that the central axis 12 of the Ar ion beam emitted from the ion gun 5 and the central axis 13 of the Xe ion beam emitted from the ion gun 11 are rotated by an angle θ2 on the XY plane.

[0022] The first monitoring mechanism MM1 and the second monitoring mechanism MM2 are provided to monitor ion milling. The first monitoring mechanism MM1 is provided to measure the amount of sputtering particles generated from the sample 6 by ion beam irradiation. The first monitoring mechanism MM1 includes a quartz oscillator 14, an oscillation circuit 15, and a detection circuit 16, which are arranged near the sample 6.

[0023] During ion milling, the oscillation circuit 15 oscillates the quartz oscillator 14 to output an oscillation signal, and the detection circuit 16 detects the frequency of the oscillation signal. Sputtered particles generated from the sample 6 during ion milling adhere to the quartz oscillator 14, causing a change in the frequency of the oscillation signal. Utilizing this phenomenon, the computer 22 measures the amount of sputtered particles deposited on the quartz oscillator 14 from the change in the frequency of the oscillation signal. From this measured amount, the amount of sputtering of the sample 6 due to ion milling can be estimated.

[0024] The second monitoring mechanism MM2 is provided to capture an image of the processed surface of the sample 6 after irradiation with the ion beam. The second monitoring mechanism MM2 includes an illumination 18 and an imaging device 19 provided outside the sample chamber 17. The illumination 18 is configured, for example, by an LED. The imaging device 19 is configured, for example, by an optical microscope, a white light interference microscope, or an electron microscope. By operating the illumination 18, the processed surface of the sample 6 can be enlarged and imaged by the imaging device 19. The computer 22 measures the shape of the processed surface from the image of the processed surface. The measurement contents include, for example, the depth and half-width of the processed surface, but are not limited to these.

[0025] An observation window 20 is provided on the upper surface of the sample chamber 17. An image of the processed surface of the sample 6 can be captured by an imaging device 19 through the observation window 20. The inner surface of the observation window 20 is protected by a shutter 21 to prevent sputtered particles from adhering to the observation window 20. During ion milling, the shutter 21 is closed to prevent sputtered particles from adhering to the observation window 20.

[0026] By driving the exhaust system control unit 25, the inside of the sample chamber 17 is changed from atmospheric pressure to a high vacuum (for example, 1.0×10 －３ The pressure inside the sample chamber 1 can be adjusted to a range of 100 Pa or less. During ion milling, the inside of the sample chamber 1 is maintained at a high vacuum. Therefore, a stable ion beam can be irradiated onto the sample 6 without being affected by gases in the atmosphere.

[0027] The overall control of the ion milling apparatus 100 is performed by the computer 22 and the controller 23. Therefore, the computer 22 and the controller 23 are sometimes collectively referred to as the "controller."

[0028] The control unit (computer 22 or controller 23) also has a storage unit 28. The storage unit 28 stores information such as programs, tables, and files for implementing each process performed by the ion milling apparatus 100. The storage unit 28 is, for example, a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or a storage medium such as an IC card, an SD card, or a DVD. The computer 22 can control the reading of information stored in the storage unit 28 and the storing of new information in the storage unit 28.

[0029] The computer 22 sets the ion milling conditions set by the user in the controller 23, monitors the ion milling, and changes the control values ​​of the controller 23. Based on the set or changed control values, the controller 23 controls the operation of each component included in the ion milling apparatus 100, such as the ion gun 5, the ion gun 11, the mass flow controllers 4, the mass flow controllers 10, the illumination 18, the imaging device 19, the stage control unit 24, and the exhaust system control unit 25.

[0030] The stage control unit 24 controls the attitude of the stage 26. The stage control unit 24 controls the rotation of the stage 26. A sample rotation central axis 27 is the central axis when the stage 26 performs a rotation operation.

[0031] The stage control unit 24 also controls tilting of the stage 26. By arbitrarily tilting the stage 26, an angle θ1 formed between the sample rotation central axis 27 and the central axis 12 of the Ar ion beam, and an angle θ3 formed between the sample rotation central axis 27 and the central axis 13 of the Xe ion beam are controlled. That is, the angle θ1 is the angle of incidence of the Ar ion beam with respect to the sample 6, and the angle θ3 is the angle of incidence of the Xe ion beam with respect to the sample 6.

[0032] The computer 22 and the controller 23 control the mass flow controller 4 and the mass flow controller 10 to switch between the Ar ion beam emitted from the ion gun 5 and the Xe ion beam emitted from the ion gun 11. The timing to switch the ion beams is determined by using the amount of sputtering particles measured by the first monitoring mechanism MM1 and the result of measuring the shape of the processed surface of the sample 6 imaged by the second monitoring mechanism MM2.

[0033] The findings obtained by the present inventors regarding ion milling using an Ar ion beam and a Xe ion beam will be described below with reference to Figures 2 to 5. In this example, a silicon-containing thin piece that constitutes part of the internal structure of a semiconductor chip is used as the sample 6.

[0034] 2 shows the relationship between the incident angle θ1 of the Ar ion beam and the sputtering yield when the Ar ion beam is used to process a sample 6. Also shown in FIG. 2 are cases where the intensity of the Ar ion beam (the sum of the acceleration voltage and the discharge voltage) is 3 kV, 4 kV, 5 kV, and 6 kV.

[0035] As shown in Fig. 2, when the incident angle θ1 is 60 degrees or more and 80 degrees or less, the sputtering yield is high. A high sputtering yield means a high processing rate. Since the purpose of ion milling using an Ar ion beam is to increase the processing rate, the incident angle θ1 of the Ar ion beam is preferably 60 degrees or more and 80 degrees or less.

[0036] 3 shows the relationship between the ion beam intensity and the sputtering yield when a sample 6 is processed using an Ar ion beam or a Xe ion beam. As shown in FIG. 3, the sputtering yield increases as the ion beam intensity increases. However, when the ion beam intensity exceeds 3 kV, the increase in the sputtering yield becomes gradual.

[0037] In the case of an Ar ion beam, increasing the intensity of the ion beam increases the number of ions penetrating into the sample 6, making it easier for an amorphous layer to form in the sample 6. Therefore, ion milling with an Ar ion beam intensity greater than 3 kV contributes to an increase in the processing rate, but also causes the thickness of the amorphous layer to increase. Note that, when ion milling at a high processing rate is important, an Ar ion beam intensity greater than 3 kV may be used. Considering the balance between an increase in processing rate and the thickness of the amorphous layer, the intensity of the Ar ion beam is preferably 3 kV or more and 6 kV or less.

[0038] 4 shows the measurement results of the thickness of the amorphous layer when a sample 6 processed using a Xe ion beam is further thinned and the thinned sample 6 is observed with a scanning transmission electron microscope (STEM). As shown in FIG. 4, the thickness of the amorphous layer decreases as the intensity of the Xe ion beam (the sum of the acceleration voltage and the discharge voltage) decreases. Furthermore, the thickness of the amorphous layer decreases as the incident angle θ3 of the Xe ion beam increases.

[0039] 5 shows the results of measuring the unevenness of the processed surface of sample 6, which was processed using a Xe ion beam, by observing the processed surface using a white light interference microscope, acquiring an image of the processed surface, and then measuring the unevenness of the processed surface based on the image. The unevenness values ​​shown in FIG. 5 are values ​​obtained by measuring the height of multiple points on the processed surface and averaging the height differences between these points.

[0040] 5, when the incident angle θ3 is 80 degrees and 85 degrees, the unevenness of the processed surface is smaller than when the incident angle θ3 is 75 degrees. Furthermore, the smaller the intensity of the Xe ion beam, the smaller the unevenness of the processed surface tends to be.

[0041] 4 and 5, in processing using a Xe ion beam, the incident angle θ3 is preferably 76 degrees or more and 85 degrees or less, and the intensity of the Xe ion beam is preferably 3 kV or more and 4 kV or less. Furthermore, the incident angle θ3 during irradiation with the Xe ion beam is preferably larger than the incident angle θ1 during irradiation with the Ar ion beam. Under these conditions, the generation of an amorphous layer can be suppressed, and unevenness on the processed surface of the sample 6 can also be suppressed.

[0042] As described above, according to the ion milling apparatus 100 of the first embodiment, the sample 6 is processed by irradiating the sample 6 with an Ar ion beam, and then the Ar ion beam is switched to a Xe ion beam, and the sample 6 is processed by irradiating the Xe ion beam. When switching from the Ar ion beam to the Xe ion beam, the operation of the ion gun 5 is stopped, and the operation of the ion gun 11 is started.

[0043] Ion beams using noble gases with larger molecular weights than Ar (e.g., Xe) can suppress the generation of amorphous layers more effectively than Ar ion beams, but there is a problem in that large irregularities tend to occur on the processed surface when processing is performed for a long period of time.

[0044] In the first embodiment, the Ar ion beam is used to perform most of the processing of the sample 6, and the Xe ion beam is used to process the sample 6 in a short time. That is, the irradiation time of the Ar ion beam is longer than the irradiation time of the Xe ion beam. The amorphous layer generated by the Ar ion beam is etched by the Xe ion beam. The thickness of the amorphous layer generated by the Xe ion beam is sufficiently smaller than the thickness of the amorphous layer generated by the Ar ion beam. Therefore, by switching from the Ar ion beam to the Xe ion beam, the generation of the amorphous layer can be suppressed as much as possible. At the same time, the unevenness generated on the processed surface of the sample 6 can be reduced.

[0045] In addition, by setting the intensity and incident angle θ1 of the Ar ion beam and the intensity and incident angle θ3 of the Xe ion beam under the conditions explained using Figures 2 to 5, it is possible to more effectively suppress the generation of an amorphous layer and reduce the unevenness generated on the processed surface of the sample 6.

[0046] <Sample Processing Method> A method for processing the sample 6 using the ion milling apparatus 100 according to the first embodiment will be described below with reference to the flowchart of FIG.

[0047] First, in step S1, ion milling conditions are set. The user sets the Ar ion milling conditions and the Xe ion milling conditions using the computer 22. The Ar ion milling conditions include, for example, the incident angle θ1 of the Ar ion beam, the intensity of the Ar ion beam (acceleration voltage, discharge voltage), and the irradiation time of the Ar ion beam. The Xe ion milling conditions include, for example, the incident angle θ3 of the Xe ion beam, the intensity of the Xe ion beam (acceleration voltage, discharge voltage), and the irradiation time of the Xe ion beam.

[0048] The conditions for Ar ion milling and Xe ion milling can be determined by storing the information obtained from FIGS. 2 to 5 in the storage unit 28 and using this information.

[0049] Furthermore, the desired processed surface shape of the sample 6 at the end of processing and the expected value of the thickness of the amorphous layer may be set as the conditions for Ar ion milling and Xe ion milling. The computer 22 may set the conditions for Ar ion milling and Xe ion milling based on the desired processed surface shape of the sample 6 and the expected value of the thickness of the amorphous layer set by the user.

[0050] In step S2, Ar ion milling is started based on the Ar ion milling conditions set in step S1.

[0051] In step S3, it is determined whether or not the monitoring conditions for the processed surface shape of the sample 6 are satisfied. The monitoring conditions for the processed surface shape may be when a certain time has elapsed since the start of processing of the sample 6, or when a certain time has elapsed since the previous monitoring. The time until the next monitoring may be determined from the measurement result of the processed surface shape.

[0052] If the monitoring conditions for the processed surface shape are satisfied (YES), the driving of the ion gun 5 is stopped, the irradiation of the Ar ion beam onto the sample 6 is stopped, and the process proceeds to step S4. If the monitoring conditions for the processed surface shape are not satisfied (NO), the irradiation of the Ar ion beam onto the sample 6 is continued until the monitoring conditions for the processed surface shape are satisfied.

[0053] In step S4, the shutter 21 is opened, and the image of the sample 6 is captured through the observation window 20 using the imaging device 19 to obtain an image of the processed surface of the sample 6. In step S5, the shape of the processed surface is measured from the image of the processed surface. The measurement contents are, for example, the depth and half-width of the processed surface, but are not limited to these.

[0054] In parallel with steps S3 to S5, step S6 is carried out. In step S6, the amount of sputtered particles is measured from the change in frequency of the oscillation signal detected by the detection circuit 16.

[0055] During the Ar ion beam irradiation, the intensity of the Ar ion beam may be reduced after a certain time has elapsed since the start of the Ar ion beam irradiation. For example, the intensity of the Ar ion beam may be reduced as the Ar ion beam irradiation time elapses. This makes it easier to suppress the generation of an amorphous layer due to the Ar ion beam.

[0056] In step S7, it is determined whether the ion beam switching conditions are satisfied. This determination is made using the results of measuring the processed surface shape of the sample 6 in step S5 and the results of measuring the amount of sputtered particles in step S6. If these results satisfy the ion beam switching conditions (YES), the process proceeds to step S9, and Ar ion milling is terminated.

[0057] If the results of measurements in steps S5 and S6 do not satisfy the ion beam switching conditions (NO), proceed to step S8, readjust the Ar ion milling conditions such as the incident angle θ1 and the intensity of the Ar ion beam, and resume Ar ion milling.

[0058] In step S10, the conditions of Xe ion milling, such as the incidence angle θ3 of the Xe ion beam and the intensity of the Xe ion beam, are confirmed. The irradiation time of the Xe ion beam may also be set based on information stored in the storage unit 28. For example, the irradiation time of the Xe ion beam may be set based on information regarding the change in the thickness of the amorphous layer generated on the surface of the sample 6 over time since the start of irradiation of the Xe ion beam and information regarding the change in the unevenness of the processed surface of the sample 6 over time since the start of irradiation of the Xe ion beam.

[0059] In step S11, Xe ion milling is started. In step S12, it is determined whether or not the termination conditions for Xe ion milling are met. If the termination conditions for Xe ion milling are met (YES), Xe ion milling is terminated. The termination of Xe ion milling is determined based on the elapsed time from the start of Xe ion milling irradiation. If the termination conditions for Xe ion milling are not met (NO), Xe ion milling is continued.

[0060] <Inspection System> An inspection system 400 according to the first embodiment will be described below with reference to Figures 7 to 10. As shown in Figure 7, the inspection system 400 includes an ion milling device 100, a sample exchange chamber 200, and a charged particle beam device 300.

[0061] The sample exchange chamber 200 connects the ion milling apparatus 100 and the charged particle beam apparatus 300, and is provided to transport the sample 6 between the ion milling apparatus 100 and the charged particle beam apparatus 300. The sample exchange chamber 200 is provided with a gate valve 40 and a gate valve 41.

[0062] The charged particle beam device 300 is an inspection device, such as a scanning electron microscope (SEM), for inspecting the internal structure of the sample 6 processed by the ion milling device 100. The charged particle beam device 300 mainly includes a stage 50, an electron gun 51, a lens 52, a deflector 53, a transport motor 54, a transport rod 55, a detector 56, an image conversion unit 57, an analysis unit 58, and a sample chamber 59. The stage 50, the electron gun 51, the lens 52, the deflector 53, and the transport rod 55 are provided inside the sample chamber 59. When inspecting the internal structure of the sample 6, the inside of the sample chamber 59 is maintained at a high vacuum by an exhaust device (not shown).

[0063] A sample holder HL for holding a sample 6 can be placed on the stage 50. An electron gun 51 can irradiate an electron beam EB1. The electron beam EB1 emitted from the electron gun 51 is focused by a lens 52 and scanned on the sample 6 by a deflector 53. A detector 56 can detect secondary electrons emitted from the sample 6 when the sample 6 is irradiated with the electron beam EB1.

[0064] The image conversion unit 57 is electrically connected to the detector 56 and includes an arithmetic processing circuit that processes the secondary electrons EB2 and creates an image. Therefore, the image conversion unit 57 can generate an image (SEM image) of the processed surface of the sample 6 from the secondary electrons EB2 detected by the detector 56. The analysis unit 58 is electrically connected to the image conversion unit 57 and can calculate the contrast of the generated image. Note that contrast is the difference in brightness between any two pixels in the image.

[0065] After Xe ion milling is completed in step S12 of FIG. 6, the sample 6 processed in the ion milling apparatus 100 is transported to the charged particle beam apparatus 300 via the sample exchange chamber 200, and the contrast of the image of the processed surface of the sample 6 is calculated in the charged particle beam apparatus 300.

[0066] First, as shown in Fig. 8, gate valves 40 and 41 are opened. Next, transport motor 54 is driven to move transport rod 55 into sample chamber 17, and sample holder HL is attached to transport rod 55. Next, as shown in Fig. 9, transport rod 55 with sample holder HL attached is moved into sample chamber 59, and sample holder HL is placed on stage 50.

[0067] Next, as shown in FIG. 10 , gate valves 40 and 41 are closed, and the inside of sample chamber 59 is maintained at a high vacuum. Next, electron gun 51 irradiates electron beam EB1. The irradiated electron beam EB1 is focused by lens 52 and scanned on sample 6 by deflector 53. Next, secondary electrons EB2 emitted from sample 6 are detected by detector 56. Next, image conversion unit 57 generates an image of the processed surface of sample 6 from secondary electrons EB2, and analysis unit 58 calculates the contrast of the image.

[0068] Here, if the thickness of the amorphous layer is large, the contrast of the image decreases, making image analysis difficult. Therefore, if the contrast is greater than a reference value, it is determined that the thickness of the amorphous layer is sufficiently small, and the inspection of the sample 6 is terminated. If the contrast is less than the reference value, the sample 6 is transferred together with the sample holder HL via the sample exchange chamber 200 to the ion milling device 100, where it is reprocessed. Steps S10 to S12 in FIG. 6 are performed as the reprocessing.

[0069] As described above, according to the inspection system 400 of the first embodiment, image analysis can be automated, and a series of steps from Ar ion milling and Xe ion milling to image analysis can be automated.

[0070] (Modification) An ion milling apparatus 100 according to a modification of the first embodiment will be described below with reference to Fig. 11. In the following description, differences from the first embodiment will be mainly described, and descriptions of points that overlap with the first embodiment will be omitted.

[0071] In the first embodiment, an Ar ion beam is emitted from the ion gun 5, and a Xe ion beam is emitted from the ion gun 11. As shown in Fig. 11 , an ion milling apparatus 100 in this modified example includes one ion gun 29 and a valve 30. The ion gun 29 is provided inside the sample chamber 17 and is capable of emitting an Ar ion beam and a Xe ion beam. The valve 30 switches between a gas supply path 31 from the mass flow controller 4 to the ion gun 29 and a gas supply path 32 from the mass flow controller 10 to the ion gun 29.

[0072] When irradiating an Ar ion beam, the gas supply path 31 is opened and the gas supply path 32 is closed by the valve 30. In this state, Ar gas is supplied from the Ar gas cylinder 1 to the ion gun 29. When switching from the Ar ion beam to the Xe ion beam, the gas supply path 31 is closed and the gas supply path 32 is opened by the valve 30. In other words, the supply of Ar to the ion gun 29 is stopped and the supply of Xe to the ion gun 29 is started. Thereafter, irradiation with the Xe ion beam becomes possible.

[0073] In this manner, in the modified example, both the Ar ion beam and the Xe ion beam can be irradiated using only one ion gun 29. Therefore, in the modified example, the configuration of the ion milling apparatus 100 can be simplified compared to the first embodiment.

[0074] The present invention has been specifically described above based on the form for implementing the present invention, but the present invention is not limited to the above-described embodiment and can be modified in various ways without departing from the spirit of the present invention.

[0075] 100 Ion milling device 200 Sample exchange chamber 300 Charged particle beam device 400 Inspection system 1 Ar gas cylinder 2 Regulator 3 Valve 4 Mass flow controller 5 Ion gun 6 Sample 7 Xe gas cylinder 8 Regulator 9 Valve 10 Mass flow controller 11 Ion gun 12 Central axis of Ar ion beam 13 Central axis of Xe ion beam 14 Quartz oscillator 15 Oscillator circuit 16 Detection circuit 17 Sample chamber 18 Lighting 19 Imaging device 20 Observation window 21 Shutter 22 Computer 23 Controller 24 Stage control unit 25 Exhaust system control unit 26 Stage 27 Sample rotation central axis 28 Memory unit 29 Ion gun 30 Valve 31, 32 Gas supply path 40, 41 Gate valve 50 Stage 51 Electron gun 52 Lens 53 Deflector 54 Transport motor 55 Transport rod 56 Detector 57 Image conversion unit 58 Analysis unit EB1 Electron beam EB2 Secondary electrons HL Sample holder MM1 First monitoring mechanism MM2 Second monitoring mechanism

Claims

1. An ion milling apparatus capable of processing a sample by irradiating the sample with an ion beam, wherein the apparatus processes the sample by irradiating the sample with a first ion beam using Ar, and then switches from the first ion beam to a second ion beam using a noble gas having a larger molecular weight than Ar, and irradiates the sample with the second ion beam, thereby processing the sample.

2. The ion milling apparatus according to claim 1, wherein the noble gas is Xe.

3. An ion milling apparatus according to claim 1, wherein the irradiation time of the first ion beam is longer than the irradiation time of the second ion beam.

4. An ion milling apparatus according to claim 1, comprising: a first ion gun capable of irradiating the first ion beam; and a second ion gun capable of irradiating the second ion beam, wherein, when switching from the first ion beam to the second ion beam, the operation of the first ion gun is stopped and the operation of the second ion gun is started.

5. An ion milling apparatus according to claim 1, comprising an ion gun capable of irradiating the first ion beam and the second ion beam, wherein, when switching from the first ion beam to the second ion beam, the supply of Ar to the ion gun is stopped and the supply of the noble gas to the ion gun is started.

6. An ion milling apparatus according to claim 1, comprising a stage on which the sample can be placed, wherein the angle formed between the central axis of the sample rotation, which is the central axis around which the stage rotates when irradiating the first ion beam, and the central axis of the first ion beam is 60 degrees or more and 80 degrees or less.

7. An ion milling apparatus according to claim 6, wherein the intensity of the first ion beam during irradiation is 3 kV or more and 6 kV or less.

8. An ion milling apparatus according to claim 1, wherein, during irradiation of the first ion beam, the intensity of the first ion beam is reduced after a certain time has elapsed since the start of irradiation of the first ion beam.

9. An ion milling apparatus according to claim 1, comprising a stage on which the sample can be placed, wherein the angle formed between the central axis of the sample rotation, which is the central axis around which the stage rotates when irradiating the second ion beam, and the central axis of the second ion beam is 76 degrees or more and 85 degrees or less.

10. An ion milling apparatus according to claim 9, wherein the intensity of the second ion beam during irradiation is 3 kV or more and 4 kV or less.

11. An ion milling apparatus as claimed in claim 1, comprising a stage on which the sample can be placed, wherein, when irradiating the second ion beam, the angle formed between the sample rotation central axis, which is the central axis around which the stage rotates, and the central axis of the second ion beam is larger than the angle formed between the sample rotation central axis and the central axis of the first ion beam when irradiating the first ion beam.

12. An ion milling apparatus as defined in claim 1, comprising: a first monitoring mechanism for measuring the amount of sputtering particles generated from the sample by irradiation with the first ion beam; and a second monitoring mechanism for imaging the processed surface of the sample after irradiation with the first ion beam, wherein the ion milling apparatus determines whether to switch from the first ion beam to the second ion beam using the results of measuring the amount of sputtering particles and the results of measuring the shape of the processed surface of the sample that has been imaged.

13. An ion milling apparatus as defined in claim 1, wherein the irradiation time of the second ion beam is set based on information relating to the change in thickness of the amorphous layer generated on the surface of the sample over time since the start of irradiation of the second ion beam, and information relating to the change in the unevenness of the processed surface of the sample over time since the start of irradiation of the second ion beam.

14. An inspection system equipped with the ion milling apparatus of claim 1, comprising: a charged particle beam device for inspecting the internal structure of the sample processed by the ion milling apparatus; and a sample exchange chamber for transporting the sample between the ion milling apparatus and the charged particle beam device, wherein the charged particle beam device has: an electron gun capable of irradiating an electron beam; a detector capable of detecting secondary electrons emitted from the sample when the sample is irradiated with the electron beam; an image conversion unit capable of generating an image of the processed surface of the sample from the detected secondary electrons; and an analysis unit capable of calculating the contrast of the generated image, wherein the sample processed in the ion milling apparatus is transported to the charged particle beam device via the sample exchange chamber, the contrast of the image of the processed surface of the sample is calculated in the charged particle beam device, and if the calculated contrast is smaller than a reference value, the sample is transported to the ion milling apparatus via the sample exchange chamber and re-processed in the ion milling apparatus.

15. A method for processing a sample using an ion milling device, comprising: (a) a step of irradiating a sample with a first ion beam using Ar to process the sample; (b) after step (a), a step of switching from the first ion beam to a second ion beam using a noble gas having a larger molecular weight than Ar; and (c) after step (b), a step of irradiating the sample with the second ion beam to process the sample.

16. A method for processing a sample according to claim 15, wherein the noble gas is Xe.

17. A method for processing a sample according to claim 15, wherein the irradiation time of the first ion beam is longer than the irradiation time of the second ion beam.

18. A method for processing a sample as defined in claim 15, wherein the ion milling apparatus comprises a stage on which the sample can be placed, and further comprising the step of: (d) placing the sample on the stage before step (a), wherein, during irradiation with the first ion beam, the angle formed between the sample rotation central axis, which is the central axis around which the stage rotates, and the central axis of the first ion beam is 60 degrees or more and 80 degrees or less, and during irradiation with the first ion beam, the intensity of the first ion beam is 3 kV or more and 6 kV or less.

19. A method for processing a sample according to claim 15, wherein, during irradiation of the first ion beam, the intensity of the first ion beam is reduced after a certain time has elapsed since the start of irradiation of the first ion beam.

20. A method for processing a sample according to claim 15, wherein the ion milling apparatus comprises a stage on which the sample can be placed, and further comprises the step of: (d) placing the sample on the stage before step (a), wherein, during irradiation with the second ion beam, the angle formed between the sample rotation central axis, which is the central axis around which the stage rotates, and the central axis of the second ion beam is 76 degrees or more and 85 degrees or less, and during irradiation with the second ion beam, the intensity of the second ion beam is 3 kV or more and 4 kV or less.

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