JPH085528A - Focused ion beam apparatus for producing cross-section sample for transmission electron microscope and method for producing the sample - Google Patents

Abstract

PURPOSE:To provide a focused ion beam apparatus. for producing a cross-section sample for a transmission electron microscope and a method for producing the sample Wherein a thickness of a worked surface of the sample for the transmission electron microscope can be quantitatively monitored to automatically detect a work finishing point with an optimum sample thickness and further uniformity in thickness of a part being worked can be easily determined. CONSTITUTION:A focused ion beam apparatus comprises a working chamber 60 with a cross-section sample 41 for a transmission electron microscope placed, an ion gun 10 for emitting an ion beam 11 to the sample 41 placed in the working chamber 60, an electron gun 20 for emitting an electron beam 21 to a worked part of the sample 41 at an angle of approximately 90 deg. with respect to the ion beam 11 emitted from the ion gun 10, a transmission electron detector 30 placed oppositely to the electron gun 20 for receiving the electron beam which has transmitted through the sample 41 to detect a current amount of the electron beam which has transmitted, and a low voltage electrode 50 placed in the vicinity of a position for fixing the sample 41 to surround the sample 41 for absorbing secondary electrons 12 generated by the ion beam 11 and the electron beam 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused ion beam device for preparing a cross-section sample for a transmission electron microscope and a method for preparing a cross-section sample for a transmission electron microscope, and particularly to a transmission electron microscope for a specific minute portion such as a defective portion of an LSI chip. The present invention relates to a focused ion beam device for preparing a cross-section sample for a transmission electron microscope for preparing a cross-section sample for a transmission electron microscope and a method for preparing a cross-section sample for a transmission electron microscope.

[0002]

2. Description of the Related Art Recently, miniaturization of LSI devices and LSI
As the material becomes thinner, it is very important to observe and evaluate the fine structure that determines the LSI device performance. In particular, an extremely thin film having a thickness of several nm is also used as a gate insulating film of a transistor, and a high spatial resolution of a comma of several nm or less is required for the observation and evaluation of such a fine structure. In addition, evaluation of crystal defects that cause various defects and cause leakage of fine transistors of an LSI device is also extremely important in improving the performance and yield of the LSI. A transmission electron microscope (TEM) is the only evaluation device that can meet these purposes.

The transmission electron microscope has the highest spatial resolution of the high-resolution observation and evaluation apparatus of about 0.2 nm, and is the only means for observing and evaluating even extremely thin LSI gate insulating films. Only the transmission electron microscope can directly observe crystal defects with high spatial resolution. In addition, the transmission electron microscope is not only for observation, but it can also be combined with an X-ray microanalyzer (EPMA) etc.
Elemental analysis with a spatial resolution of about 1 is possible, and has a spatial resolution of about 1/20 as compared with Auger electron spectroscopy (AES), which has the highest spatial resolution among other analysis methods. It is positioned as an extremely useful analysis method in LSI device analysis, which is becoming more and more miniaturized.

A projection image of an electron beam transmitted through the sample is used for observation and evaluation with a transmission electron microscope. Therefore, the sample for a transmission electron microscope needs to be processed to have a thickness that allows the electron beam to pass therethrough. Specifically, it is necessary to reduce the film thickness to about 500 nm or less, and particularly to perform high resolution observation for evaluating the crystal structure etc., it is necessary to thin the sample to about 100 nm or less.

Generally, in the preparation of a sample for a transmission electron microscope of an LSI, the sample is mechanically thinned and then finally thinned by an ion beam. This is a thin film formed in a wide range or the same shape. This is a case where an arbitrary position of an LSI pattern in which
When evaluating a specific part such as a defective transistor or open contact, the observation evaluation part may be lost if the position of the processed part for thinning is displaced. Therefore, in the sample preparation for the transmission electron microscope, the position accuracy is 1 μm or less. It is necessary to thin the specific part. This cannot be dealt with by simple mechanical polishing and ion beam processing, and several sample processing methods have been devised.

A method of mechanically polishing a sample for a transmission electron microscope for performing a transmission electron microscope observation or analysis of a cross section of a specific minute portion such as a defective portion of an LSI chip will be described below with reference to FIGS. 4a to 4g. To do.

(1-1) As shown in FIG. 4a, a specific minute portion 4 desired to be observed by a transmission electron microscope by a laser marker equipped with a microscope, a focused ion beam device, or the like.
2 Marking 43 is performed by making a hole in the periphery. It should be noted that the marking is performed at a position about 20 μm or more away from the specific minute portion 42 so that the specific minute portion 42 is not affected by the thermal influence of the laser or the ion beam irradiation for the marking 43 and the scattered matter contamination of the holes. Good. Regarding the size and depth of marking, the larger the position, the better in terms of position confirmation in later processing. However, the size and depth are about 5 μm or less and the depth is 1 to 5 μm due to the need to suppress heat and flying objects during marking. The degree is considered good. When it is necessary to use a low-magnification microscope such as a stereomicroscope for sample processing, it is advisable to add a marking having a size of about 10 μm at a position further separated by 40 μm or more from the specific minute portion 42 in addition to the marking.

(1-2) Glass 44 is attached to the surface of the sample 41 for surface protection.

(1-3) With reference to the marking, the periphery of a specific minute region desired to be observed or analyzed is cut into about 1.5 mm □ or less which can be introduced into a transmission electron microscope by a high-speed rotating outer peripheral blade 61 of a dicing machine. . At this time, as the cutting plane, as shown in FIGS. 4b and 4c, a plane parallel to the cross section desired to observe or analyze the sample 41 for the transmission electron microscope and a plane perpendicular thereto are selected. Observation of sample 41 /
A narrower cutting width in the direction perpendicular to the cross section desired to be analyzed can shorten the time for the next polishing, and therefore, a narrow cut in a range where the specific minute portion 42 desired to be observed or analyzed at the time of cutting is not damaged, for example, 100 to 200 μm width. To do.

(1-4) Two cutting planes parallel to the desired cross section of the sample 41 for observation or analysis are mechanically polished by a polishing jig 70 and a rotary polishing plate 71 as shown in FIGS. 4d and 4e. . At this time, referring to the marking, the one side surface is polished until the distance becomes about 10 μm with respect to the specific minute portion 42 desired to be observed / analyzed. One side surface of the sample 41 and the other side surface facing the same are polished from the specific minute portion 42 to a distance of about 70 μm. As a result, the width of the sample 41, which is the distance between the polishing surfaces, becomes about 80 μm. Note that the polishing up to this point uses polishing particles of about 5 to 15 μm, which have a relatively high polishing rate. The polishing surface, which is one side surface of the sample 41 near the specific minute portion 42, is mirror-finished at this stage by using finer polishing particles of 1 μm or less.

(1-5) As shown in FIG. 4f, the sample 41 is rotated on the rotary stage 7 with the polished surface, which is the other side surface of the sample 41 away from the specific minute portion 42, which is not mirror-finished.
Then, the dimple grinder is polished around the desired portion for observation / analysis with the rotary polishing disk 72. In the dimple grinder polishing, a thickness of 20 to 30 μm near the analysis / observation desired portion is first obtained by using an abrasive material of 5 to 10 μm.
Grind until Then, a mirror finish of the analysis / observation desired portion is performed using abrasive grains of 1 μm or less.

(1-6) The sample 41 is attached to a transmission electron microscope mesh 80, as shown in FIG.

(1-7) Ion milling is performed from both sides with an ion milling device to obtain a thickness of 500 nm or less.

(1-8) Sample 41 by transmission electron microscope
Observe and analyze.

Next, a method of processing a sample for a transmission electron microscope by the focused ion beam apparatus disclosed in JP-A-2-132345 and JP-A-5-180739 will be described with reference to FIGS. 5A to 5G. .

(2-1) The aforementioned (1-1) and (1-3)
By the same method as described above, the sample is marked and the sample 41 is cut as shown in FIGS. 5a to 5c. If necessary, the observation / analysis desired region of the sample is further thinly cut by a high-speed rotating outer peripheral blade 61 of the dicing machine as shown in FIG. 5d.

(2-2) Focused ion beam 11 is irradiated with the focused ion beam 11 in the vicinity of the specific minute portion 42 desired to be observed / analyzed from the sample surface direction as shown in FIGS. 5e and 5f. At this time, the focused ion beam 11 is as shown in FIG.
As shown in (1), a rectangular region 81, 82 having one side parallel to the desired observation / analysis cross section is raster-scanned, and this region is sputter-etched. While appropriately selecting the beam current, beam diameter, etc. of the focused ion beam 11, the raster scanning region is gradually brought closer to the desired cross section for observation / analysis, and the cross section is processed as shown in FIG. 5f. By performing this processing from both sides of the specific minute portion 42 desired to be observed / analyzed, the minute portion is thinned and used as a sample for a transmission electron microscope.

The focused ion beam 11 is shown in FIG.
As shown in (c), it has an inverted conical shape, and when a beam is irradiated perpendicularly to the sample surface, a vertical cross section cannot be obtained. Therefore, as shown in FIG.
Only tilt to get a vertical cross section. Since this angle θ differs depending on the focused ion beam device and processing conditions, it is necessary to set the conditions in advance, and processing is generally performed with an inclination of about 3 to 5 degrees. Also, during the actual processing, the processing is interrupted intermittently, and the processed shape is observed by a secondary ion image or secondary electron image by a focused ion beam, observation by moving the sample to a scanning electron microscope, and electron beam. In a focused ion beam apparatus having an irradiation function, evaluation is performed by observing secondary electron images by electron beam irradiation in the apparatus, and if there is a problem, adjustment of focused ion beam, change of conditions, and angle adjustment of sample are appropriately performed.

(2-3) As shown in FIG. 5g, the sample 41 is attached to a transmission electron microscope mesh 80, centering on the desired portion for analysis / observation.

(2-4) Sample 41 by transmission electron microscope
Observe and analyze.

The end point of the focused ion beam processing is determined by the following method.

(1) The shape of the processed portion is observed with a secondary ion image or secondary electron image obtained by ion beam irradiation, the thickness of the processed portion is judged from the observed image, and the processing end point is determined. The image resolution is several tens of nm.

(2) Focused ion beam processing and scanning electron microscope observation are performed alternately, the thickness of the processed portion is determined from the observation image of the processed portion by the scanning electron microscope, and the processing end point is determined. Alternatively, focused ion beam processing and scanning electron microscope observation are alternately performed, and the sample perfection is determined from the resolution of the transmission electron microscope observation image.

(3) As disclosed in Japanese Patent Laid-Open No. 4-76437, a focused ion beam device equipped with an electron gun in addition to an ion gun or a focused ion beam device capable of irradiating an electron beam using the ion gun In the above, in the focused ion beam device, focused ion beam processing and observation with an electron beam are alternately performed, the thickness of the processed portion is judged from the observed image, and the processing end point is determined.

[0025]

In the conventional method of processing a sample for a transmission electron microscope by mechanical polishing, the processing position accuracy for a minute portion desired to be observed and evaluated is several μm at the mechanical polishing stage, and The accuracy of 1 μm or less required for processing for observing a defective portion cannot be obtained.

In the conventional method for processing a sample for a transmission electron microscope using a focused ion beam apparatus, a secondary ion image by a focused ion beam or a secondary electron image by a focused ion beam is used to evaluate a processed shape, or a secondary ion by a focused ion beam is used. When the processing end point is judged by evaluating the thickness of the processed surface by observing an image or a secondary electron image, the processing target thickness is several tens to one hundred and several tens nm, whereas the focused ion beam beam system is used. Is at least 10
Since it is about 0 nm, and the resolution of the obtained secondary ion image and secondary electron image conforms to the ion beam diameter, it is difficult to accurately determine the thickness on the image, and the success rate of sample preparation becomes low.
Since the observation with the focused ion beam is performed alternately with the processing, there is a possibility that the processing may be performed beyond the processing end point. Since the cross-section is processed by the inverted conical focused ion beam, the sample is tilted and processed as shown in FIG. 6C. However, the processed cross section is different from the surface for each processing due to variations in adjustment of the focused ion beam. It deviates from the vertical plane. For example, when the angles of both sides of the processed surface are inclined by 2 degrees, the width of each part of the outermost surface is 3
At the position of μm depth, the thickness is deviated by 100 nm.
In this state, the width of the processed part on the outermost surface 9 is 100 nm which is the target.
2 is reached at a depth of 3 μm depending on the tilt direction.
The width becomes 00 nm or 0 nm, and a hole is opened. The depth of 3 μm corresponds to the thickness from the surface of the LSI device structure. Further, when the width of the processed portion is 200 nm, high resolution observation such as lattice image observation is difficult. It is impossible to evaluate such an angular error with respect to the vertical direction of the machined surface with the observation resolution of the focused ion beam, and it is impossible to observe it from above. The success rate of preparing a sample for a microscope is low.

When the processing shape and the processing end point by the focused ion beam are judged by the scanning electron microscope or the observation image by the transmission electron microscope, the focused ion beam processing and the electron microscope observation are alternately carried out. It takes a long time to replace, and the processing time becomes long. Generally, the processing time is 3 to 5 hours, but if observation is added, it takes at least 1 hour at least once for sample exchange, observation, and focused ion beam readjustment, and only 2 to 3 times are added. Therefore, the time required from the start to the end of focused ion beam processing is 1.5 to 2 times. When the focused ion beam processing and the electron microscope observation are alternately performed, when reprocessing with the focused ion beam, as shown in FIGS. 6A and 6B, an error occurs in the processing direction due to the replacement of the sample, The thickness of the observation portion becomes non-uniform, and good observation becomes difficult. With an electron microscope, the observation resolution is several nm or less, and the thickness of the surface of the processed portion can be evaluated more accurately than in the observation method using an ion beam. However, it is difficult to observe and evaluate the processed shape, for example, the angle error with respect to the vertical direction of the processed surface, and it is difficult to accurately evaluate the film thickness of the observation desired portion.
When the focused ion beam is processed again after the observation, the focused ion beam needs to be readjusted, the conditions are changed, and the feedback from the evaluation result cannot be performed.

In a focused ion beam apparatus having an electron beam irradiation function, when the end point of the focused ion beam processing is judged by observing a secondary electron image or the like obtained by the electron beam, the ion gun also serves as an electron gun. However, even if the electron gun is provided separately from the ion gun, the secondary electron image cannot be observed by the electron beam because of the secondary electrons generated by the ion beam irradiation during the focused ion beam processing. Therefore, processing and observation cannot be performed at the same time, and there is a risk of processing beyond the processing end point. Since it is observed from above the machined part, the inclination of the machined surface with respect to the vertical direction cannot be accurately evaluated.

The present invention has been made to solve the above problems, and quantitatively monitors the thickness of the processed surface of a sample for a transmission electron microscope to automatically detect the best sample thickness. It is an object of the present invention to provide a focused ion beam device for preparing a cross-section sample for a transmission electron microscope and a cross-section sample preparation method for a transmission electron microscope, which enables the uniformity of the thickness of a processed portion to be easily determined during processing.

[0030]

According to the present invention, the above-mentioned object is to provide an ion gun means for emitting an ion beam for producing a cross-section sample for a transmission electron microscope, and an ion emitted from the ion gun means. Electron gun means for irradiating the processed portion of the cross-section sample for the transmission electron microscope with an electron beam at an angle of about 60 to 90 degrees with respect to the beam, and for the transmission electron microscope, the electron gun means being arranged to face the electron gun means. A focused ion beam device for preparing a cross-section sample for a transmission electron microscope according to claim 1, further comprising a detection unit that receives an electron beam that has passed through the cross-section sample and detects a current amount of the electron beam that has passed through the cross-section sample.

According to the present invention, the above-mentioned object is provided with an electrode means for absorbing secondary electrons generated by irradiation of an ion beam and an electron beam in the vicinity of a position where the cross-section sample for a transmission electron microscope is fixed. This is achieved by the focused ion beam device for producing a cross-sectional sample for a transmission electron microscope according to claim 2.

According to the present invention, the above-mentioned object is to cut a sample, which requires cross-sectional observation by a transmission electron microscope, into a thickness that can be mounted on the transmission electron microscope, and to further thin the observation region by a focused ion beam. The step of irradiating the processed portion of the sample with the electron beam while promoting the thinning with the focused ion beam, the step of detecting the current amount of the electron beam passing through the sample, and the step of measuring the sample based on the detected current amount. The method for producing a cross-section sample for a transmission electron microscope according to claim 3, further comprising the step of scanning the processed portion with an electron beam to evaluate the uniformity of the thickness of the processed portion.

According to the present invention, the above-mentioned object is to cut a sample that requires cross-sectional observation with a transmission electron microscope to a thickness that can be mounted on the transmission electron microscope, and to further thin the observation region with a focused ion beam. The step of irradiating the processed portion of the sample with the electron beam while promoting the thinning with the focused ion beam, the step of detecting the current amount of the electron beam passing through the sample, and the step of measuring the sample based on the detected current amount. The method for producing a cross-section sample for a transmission electron microscope according to claim 4, further comprising the step of detecting a processing end point.

[0034]

According to the focused ion beam device for preparing a cross-section sample for a transmission electron microscope of claim 1, the focused ion beam is irradiated onto the sample surface by an ion gun means at an arbitrary accelerating voltage, beam current and beam diameter. Raster scan an arbitrary area on the sample surface. During ion beam processing, the electron beam is moved by an electron gun means at an arbitrary accelerating voltage, beam current, and beam diameter at an arbitrary position on the processing surface from 60 degrees to the ion beam.
The sample is irradiated at an angle of about 90 degrees, the electron beam transmitted through the sample is received by the detection unit, the current amount of the electron beam transmitted by the detection unit is detected, and the current value of the transmitted beam reaches a preset value. The processing is completed by the focused ion beam at the stage.

According to the focused ion beam device for preparing a cross-section sample for a transmission electron microscope of claim 2, electrons such as secondary electrons by the focused ion beam irradiated to the sample by the electrode means to which an arbitrary positive voltage is applied. Is absorbed so that it does not interfere with the detection of the amount of transmitted electron beam current reaching the detection means.

According to the method for preparing a cross-section sample for a transmission electron microscope of claim 3, when a cross-section sample for a transmission electron microscope is prepared, a thickness which allows a sample requiring cross-section observation by the transmission electron microscope to be mounted on the transmission electron microscope. Cut into small pieces, further thin the observation region with a focused ion beam, and irradiate the processed part with an electron beam while proceeding with thinning with a focused ion beam,
The amount of current of the transmitted beam is detected, the uniformity of the thickness of the processed portion of the sample is evaluated based on the detected current value, and a cross-sectional sample for a transmission electron microscope having a uniform thickness is created based on this evaluation.

According to the method for preparing a cross-section sample for a transmission electron microscope of claim 4, when a cross-section sample for a transmission electron microscope is prepared, a sample which requires cross-section observation by the transmission electron microscope can be attached to the transmission electron microscope. Cut into small pieces, further thin the observation region with a focused ion beam, and irradiate the processed part with an electron beam while proceeding with thinning with a focused ion beam,
A cross-sectional sample for a transmission electron microscope is created by the process of monitoring the electron beam passing through the sample and detecting the processing end point.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a focused ion beam device for producing a cross-section sample for a transmission electron microscope according to claim 1 will be described below with reference to FIG. In the present embodiment, the thickness of the processed surface of the sample for transmission electron microscope can be quantitatively monitored to automatically detect the best sample thickness, and the uniformity of the thickness of the processed portion can be easily made during the processing. An object of the present invention is to provide a focused ion beam device for cross-section sample preparation for a transmission electron microscope that can be judged.

This example is a cross-sectional sample 4 for a transmission electron microscope.
1 to the processing chamber 60, the ion gun 10 as the ion gun means for emitting the ion beam 11 to the sample 41 placed in the processing chamber 60, and the ion beam 11 emitted from the ion gun 10 is about 90. An electron gun 20 as an electron gun means for irradiating the processed portion of the sample 41 with an electron beam 21 at an angle of degrees, and an electron beam which is arranged so as to face the electron gun 20 and which has passed through the transmission electron microscope cross-section sample 41. The transmitted electron detector 30 as a detection means for detecting the amount of current of the electron beam that has been received and transmitted, and the ion beam 11 and the electron beam which are arranged so as to surround the sample 41 in the vicinity of the position where the sample 41 is fixed. Low voltage electrode 50 as an electrode means for preventing secondary electron 12 generated by 21 from being absorbed and preventing an accurate amount of transmitted beam current from being measured.
Is provided.

The sample 41 is carried into the processing chamber 60 by a sample introduction system (not shown), and is appropriately driven by a stage drive system (not shown). The ion beam 11 and the electron beam 21 can be raster-scanned, respectively, and the shape of the irradiation region of each beam can be observed by a secondary ion detector or a secondary electron detector (not shown). The operation of this embodiment is the same as the embodiment of the method for preparing a cross-sectional sample for a transmission electron microscope, which will be described later, and thus the description thereof will be omitted.

Next, an embodiment of the method for preparing a cross-section sample for a transmission electron microscope according to claims 3 and 4 will be described with reference to FIGS. 2a to 2g and 3a to 3h. In this example,
Transmission electron microscope that can quantitatively monitor the thickness of the processed surface of the sample for the transmission electron microscope and automatically detect the best sample thickness, and can easily determine the uniformity of the thickness of the processed part during processing. An object is to provide a method for preparing a cross-section sample for use.

As shown in FIG. 2A, a defective transistor or the like on the LSI chip 41 is observed by a transmission electron microscope around a specific minute portion 42 desired to be observed / analyzed by a focused ion beam device or a laser marker equipped with a microscope. The marking 43 is performed by making a hole. It should be noted that the marking is performed at a position about 20 μm or more away from the specific minute portion 42 so that the specific minute portion 42 is not affected by the thermal influence of the laser or the ion beam irradiation for the marking 43 and the scattered matter contamination of the holes. Good. Regarding the size and depth of marking, the larger the position, the better in terms of position confirmation in later processing. However, the size and depth are about 5 μm or less and the depth is 1 to 5 μm due to the need to suppress heat and flying objects during marking. The degree is good. With reference to the marking, the high-speed rotating outer peripheral blade 61 of the dicing machine can introduce the periphery of a specific minute region desired to be observed or analyzed into a transmission electron microscope.
Cut to less than m □.

At this time, as the cutting plane, as shown in FIG. 2B, a plane parallel to the cross section desired to observe or analyze the sample 41 for the transmission electron microscope is selected. Observation of sample 41 /
The narrower the cutting width in the direction perpendicular to the cross section where analysis is desired, the narrower the range of the focused ion beam processing to be performed later, so the cutting width in the vertical direction is the specific minute size desired to be observed / analyzed by chipping during cutting. Range where part 42 is not damaged,
For example, it is cut narrowly with a width of 100 to 200 μm. If necessary, further observe / analyze the sample near the surface of the desired portion, and as shown in FIG.
Cut thinly with 1.

The processed LSI chip is introduced into a focused ion beam device. When the LSI chip is introduced into the focused ion beam apparatus, the orientation of the LSI chip is set so that the processed cross section faces the electron gun 20 inside the focused ion beam apparatus. Observation / analysis by raster scanning with a focused ion beam device Rectangular area 8 with one side of desired cross section
The focused ion beam 11 is irradiated to the Nos. 1 and 82, and thinning processing of the desired cross section for observation / analysis is performed. The rectangular region 81 faces the transmission electron detector 30, and the rectangular region 82 is a region including a cross section facing the electron gun 20 in the focused ion beam apparatus. In this focused ion beam processing, the area 81 is processed first. The processing of the region 81 increases the position accuracy of the cross-section processing and the uniformity of the processed surface while gradually reducing the beam current / beam diameter of the focused ion beam 11.

General processing conditions are acceleration voltage 25 to 30.
Beam current 2000p using kV, Ga ion beam
The processing is performed at a position of about A to a position several μm away from the target specific minute portion 42, and then to a position of 1 μm from the specific minute portion 42 at a beam current of about 400 pA. Furthermore,
A beam current of about 100 pA is processed to a position including the specific minute portion 42, and finally a processed surface is finished with a beam having a beam current of about several tens pA. The focused ion beam 11
Is an inverted conical shape, and when a beam is irradiated perpendicularly to the sample surface, a vertical cross section cannot be obtained. Therefore, the sample 41 is processed with an inclination of about 3 to 5 degrees depending on the beam conditions.

After the processing of the area 81 is completed, the area 82 is processed by the same method. In the processing of the region 82, when the thickness of the processed portion becomes about 1 μm, the electron beam 21 is irradiated substantially perpendicular to the desired cross section for observation / analysis, and the transmitted electrons transmitted through the processed portion of the cross section of the sample are detected by the transmitted electron. It is detected by the container 30.

The acceleration voltage of the electron beam is set to 10 kV or higher. In the case of silicon, the electron beam transmits a thickness of 1 μm if the acceleration voltage is 10 kV or higher. Therefore, the transmitted electrons are detected by the detector 30 by this electron beam irradiation. As the detector 30, a channeltron having a high sensitivity and a high detection speed is effective, but a Faraday cup or the like can be used depending on the material of the sample and the setting of the electron beam current. The voltage applied to the detector 30 and the electron beam current are appropriately set according to the detected transmitted electron beam current. As shown in FIGS. 3a and 3b, when the electron beam is operated up and down, left and right within the range of the same material, and the transmitted beam current is detected, if the processed portion has a uniform thickness, as shown in FIG. The waveform is obtained. On the other hand, as shown in FIGS. 3e, 3f, and 3g, when the thickness of the processed portion is not uniform, the transmitted beam current waveform becomes the waveform shown in FIG. 3d. The nonuniformity of the processed portion confirmed at this stage can be finally corrected by correcting the focused ion beam shape, the sample angle, and the like in the subsequent processing.

The region 82 is processed by focused ion beam processing while continuing to detect the transmitted beam current. The transmitted beam current increases as the thickness of the processed portion decreases. As the transmitted beam current detected increases, the electron beam 21
When the accelerating voltage of is gradually reduced, as shown in FIG.
Since the transmission thickness of the electron beam also decreases, it is possible to accurately detect the change in the thickness of the processed portion due to the change in the transmission beam current by appropriately selecting the acceleration voltage. In the case of a silicon material, if the final accelerating voltage of the electron beam 21 is set to about 3 kV or less, a thickness of about 500 to 1000 Å can be detected by the value of the transmitted beam current. If a good transmission electron microscope sample is used in advance to set the conditions for the amount of transmitted current and the amount of transmitted beam current to be the processing end point is determined, the processing end point can be detected automatically.

When detecting the transmitted electron beam,
By applying a positive low potential to the low-voltage electrode 50 and collecting a large amount of secondary electrons 12 generated by focused ion beam irradiation, deterioration of the transmitted electron beam current detection accuracy is prevented, and the transmitted electron beam is irradiated even during focused ion beam irradiation. It is possible to detect the current and prevent over-processing.

In order to prevent adverse effects on the ion beam and electron beam, a nonmagnetic metal is used as the material of the low voltage electrode 50 to prevent magnetization. The voltage applied to the low voltage electrode 50 is
It is set to + several tens V so as not to affect the focused ion beam or electron beam orbit of several kV to 30 kV and to improve the recovery efficiency of the secondary electrons of several tens eV generated by the irradiation of the focused ion beam.

The reason why the region 81 is processed first is as follows.
In the state where the focused ion beam 11 is applied to the processing area 81 on the cross section side facing the transmitted electron detector 30, the scattered ions of the focused ion beam enter the side of the transmitted electron detector 30, and the accurate transmitted beam current value is Since it is difficult to measure, the processing area of the cross section on the side of the transmission electron detector 30 is completed first, and at the processing stage of the area 82 where scattered ions of the focused ion beam are hard to enter the detector 30, the processing portion of the processing portion by the transmission beam current amount detection is processed. This is because the thickness is evaluated and the end point is detected.

The analysis / observation desired portion of the sample 41 is attached to a transmission electron microscope mesh 80, as shown in FIG. 2g. The sample 41 is observed and analyzed by a transmission electron microscope.
The processing with a focused ion beam has been described above.
It can also be used in processing such as ion milling to evaluate the film thickness and film thickness uniformity of the processed portion.

[0053]

According to the focused ion beam device for preparing a cross-section sample for a transmission electron microscope according to claim 1 and the method for preparing a cross-section sample for a transmission electron microscope according to claims 3 and 4, an observation cross section having a uniform thickness can be obtained. When it can be formed, it is possible to prevent excess processing. As a result, the variation in the thickness of the processed portion can be detected with an accuracy of 50% or less, and this can be corrected in the processing stage. Therefore, the variation in the thickness of the processed portion can be reduced to 50 nm or less at the final stage, and the variation in the processed area is almost the same. High-resolution observation can be performed over the entire area. Since the sample thickness can be numerically detected and detected in the cross-section sample preparation, the transmission electron microscope sample preparation of the optimum thickness can be performed without affecting the skill level of the operator if the conditions are set for each material.

According to the focused ion beam apparatus for preparing a cross-section sample for a transmission electron microscope of claim 2, secondary electrons generated by irradiation of an ion beam and an electron beam are detected by a transmission electron detector to detect a transmission electron beam current. It is possible to prevent the accuracy from deteriorating. Further, it becomes possible to detect the transmitted electron beam current even during irradiation of the focused ion beam, and it is possible to prevent the processing from being exceeded even during irradiation of the focused ion beam. Thereby, the processing accuracy of the cross-section sample can be improved, and the cross-section sample can be easily created.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a focused ion beam device for producing a cross-section sample for a transmission electron microscope of the present invention.

FIG. 2a is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 2b is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 2c is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 2d is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope according to the present invention.

FIG. 2e is a diagram showing an example of a method for producing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 2f is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 2g is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope according to the present invention.

FIG. 3a is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3b is a diagram showing an example of the method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3c is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3d is a diagram showing an example of the method for producing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3e is a diagram showing an example of a method for producing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3f is a diagram showing an example of the method for producing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3g is a diagram showing an example of a method for preparing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 3h is a diagram showing an example of the method for producing a cross-sectional sample for a transmission electron microscope of the present invention.

FIG. 4a is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4b is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4c is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4d is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4e is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4f is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 4g is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5a is a view showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5b is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5c is a view showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5d is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5e is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5f is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 5g is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

FIG. 6 is a diagram showing a conventional cross-sectional sample preparation method for a transmission electron microscope.

[Explanation of symbols]

 10 Ion gun 20 Electron gun 30 Transmission electron detector 40 Sample 50 Low voltage electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01J 37/31 9172-5E

Claims (4)

[Claims] 1. An ion gun means for emitting an ion beam for producing a cross-section sample for a transmission electron microscope, and 60 ° to 9 ° with respect to the ion beam emitted from the ion gun means.
Electron gun means for irradiating the processed portion of the cross-section sample for transmission electron microscope with an electron beam at an angle of about 0 degree, and an electron beam arranged to face the electron gun means and transmitted through the cross-section sample for transmission electron microscope. A focused ion beam device for producing a cross-section sample for a transmission electron microscope, comprising: a detection unit that detects the amount of current of an electron beam that has been received and transmitted. 2. The transmission electron microscope according to claim 1, further comprising an electrode means for absorbing secondary electrons generated by irradiation of an ion beam and an electron beam, in the vicinity of a position where the cross-section sample for the transmission electron microscope is fixed. Focused ion beam device for cross-section sample preparation. 3. A step of cutting a sample that requires cross-sectional observation with a transmission electron microscope into a thickness that can be attached to the transmission electron microscope, a step of further thinning an observation region with an ion beam, and a thinning with the ion beam. The step of irradiating the processed portion of the sample with an electron beam while advancing the step, the step of detecting the amount of current of the electron beam passing through the sample, and the processed portion of the sample by the electron beam based on the detected amount of current. A method for preparing a cross-section sample for a transmission electron microscope, comprising the step of scanning to evaluate the uniformity of the thickness of the processed portion. 4. A step of cutting a sample that requires cross-sectional observation with a transmission electron microscope into a thickness that can be attached to the transmission electron microscope, a step of further thinning an observation region with an ion beam, and a thinning with the ion beam. Irradiating the processed part of the sample with an electron beam while advancing the step, detecting the amount of current of the electron beam passing through the sample, and detecting the processing end point of the sample based on the detected amount of current. A method for preparing a cross-section sample for a transmission electron microscope, comprising: