JP2000005883A - Sample cutting method by focused ion beam, cross section monitoring method, sample fixing structure, and fixing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a total cross section monitoring time by reducing a processing time of a sample when the cross section of the sample is monitored by a focused ion beam. SOLUTION: After a sample 5 is fixed to a sample holding plate 10 under a condition that a stress is generated in an inner part, the sample 5 is cut. Thereby, at least one of samples 5a, 5b after cutting is moved due to stress releasing. Then, a monitoring face 12 is formed to the sample 5a so as to carry out cross section monitoring. Thereby, the total time required for monitoring the cross section of the sample with the focused ion beam is significantly reduced compared to the conventional. More particularly, the total required time can be reduced to about 1/2-1/3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a sample and observing a cross section using a focused ion beam (hereinafter, simply referred to as "FIB").

[0002]

2. Description of the Related Art Conventionally, FIB has been used for failure analysis of semiconductor devices and the like. An example of a failure analysis method using this FIB is disclosed in, for example, a material for applied magnetic seminars (Japan Society of Applied Magnetics '93 12/8). In this document, a concave portion is formed on a sample surface by FIB, and the sample is tilted to observe / analyze the side surface of the concave portion.

[0003]

In recent years, for example, an ultrafine wire having a diameter of about several tens of μm has been used as a coil for a fine magnet or the like, and it is desired to suppress cutting of the ultrafine wire during processing. ing. In view of such a demand, the inventors of the present application have tried to observe the cross section of the ultrafine wire using FIB.

FIG. 13 shows an example of the observation method. FIG.
Referring to FIG. 3 (a), the ultrafine wire (sample 5) is fixed on the sample holder 10 by the fixing unit 9, and the sample holder 10 is set on the stage of the FIB processing apparatus.
Irradiate IB. Thus, the sample 5 is cut as shown in FIG. 13B, and divided into samples 5a and 5b. An observation surface is formed on one sample 5a, and the observation surface 12 is observed by tilting the stage as shown in FIG. 13 (c).

[0005] The cross section of the sample 5 was observed in this manner, but the following problems occurred at that time.

Here, the processing width D2 of the sample 5 shown in FIG. 13A will be described with reference to FIG. As shown in FIG. 14, when the angle between the observation direction and the observation surface 12 is θ and the diameter of the sample 5 is L, it is necessary to process and remove the sample 5 from the observation surface 12 to the near side with a width of Ltan θ or more. There is. Since the angle θ is preferably about 45 °,
The processing width D2 is substantially equal to the diameter of the sample 5. Although FIG. 14 shows a state in which a groove is formed in the sample 5 for convenience of explanation, the processing width D is usually as shown in FIG.
Sample 5 is processed and removed for 2 minutes.

As described above, it takes a considerable time to process and remove the sample 5 by the processing width D2 substantially equal to the diameter of the sample 5. Specifically, as shown in FIG.
When the thickness of 2 is about 20 μm, an enormous processing time of about 480 minutes is required. As a result, there is a problem that a long time is required for observing the cross section of the sample 5 using the FIB.

The present invention has been made to solve the above problems. An object of the present invention is to provide a FIB
An object of the present invention is to reduce the processing time of the sample 5 in the cross-sectional observation of the sample 5 using the method.

[0009]

A sample cutting method using an FIB according to the present invention includes the following steps. The sample is fixed to the sample holding table while a stress is generated inside. The sample is cut by FIB, and one of the samples is moved relatively to the other sample by releasing the stress.

[0010] As described above, by cutting a sample in which stress is generated therein, the stress is released after cutting, and the free end of at least one of the samples can be moved. At this time, by appropriately adjusting the cutting position,
After cutting, the cut surface of one sample can be shifted relative to the cut surface of the other sample by a desired size. Therefore, it is not necessary to increase the processing width as in the related art, and the processing width can be significantly reduced. In particular,
The processing width of about 20 μm could be reduced to about 2 to 3 μm. Thereby, the processing time of the sample can be reduced to about 1/8.

Preferably, only one sample is moved after cutting while the other sample is fixed.

By fixing the other sample in this manner, an observation surface can be formed on the other sample without correcting positional deviation after cutting the sample. Thereby, cutting of the sample and formation of the observation surface can be performed continuously, and a series of processing processes can be automated.

Preferably, the one sample is moved to a position where the cut surface of one sample does not face the cut surface of the other sample.

By moving one sample to the above position, the processing width can be reduced and the observation surface can be formed on the other sample.

[0015] Also, preferably, 50 mm from the sample fixing portion.
Cut the position within 0 μm. By performing cutting within the above range, the amount of movement of the sample after cutting can be suppressed to within 1.5 μm. Thereby, up to 500 μm
The amount of movement of the other sample can be detected by image recognition in the observation field at the angle, and the FIB irradiation position can be corrected accordingly. As a result, it is possible to automate a series of processing processes although the above-described correction is necessary. .

More preferably, the distance from the fixed part of the sample is 50
Cut the position within μm. Thereby, the movement amount of the other sample after cutting can be suppressed to 0.15 μm or less, and a series of processing processes can be automated without performing correction by image recognition.

[0017] Preferably, an observation surface is formed on the other sample, and this observation surface is observed through an observation visual field.
Then, the sample is cut so that the cut surface of the other sample remains within the observation visual field after cutting.

Since the cut surface of the other sample on the side forming the observation surface remains in the observation field after cutting, even if the other sample moves after cutting, the moving amount of the other sample can be easily recognized by image recognition. Detection can be performed, and the FIB irradiation position can be corrected.

The sample is preferably a wire or a plate. INDUSTRIAL APPLICABILITY The present invention is effective in observing a cross section of a wire or a plate using FIB.

When the sample is a wire, it is preferable to cut a portion within a length of three times the diameter of the sample from the fixed portion of the sample.

The inventors of the present application used a wire having a diameter of 23.5 μm as a sample, and cut a portion within 50 μm from the fixed portion. As a result, it was confirmed that the amount of movement of the sample on the side forming the observation surface was suppressed to 0.15 μm or less. This means that the diameter of the sample is 3 mm from the fixed part of the sample.
It is presumed that by cutting the portion within the double length, the moving amount of the other sample can be suppressed to about 0.15 μm or less.

The section observation method using the FIB according to the present invention includes the following steps. The sample is fixed to the sample holding table while a stress is generated inside. The samples are cut with FIB and one sample is moved relative to the other by release of the stress. Tilt the sample holder. The cross section is observed by irradiating the other sample with FIB.

In this case as well, the processing time of the sample can be reduced, as in the above-described cases. Thereby, the section observation time can be shortened. The inventors of the present application examined the ratio of the sample processing time within the total time required for cross-sectional observation, and found that about 70% or more of the cross-sectional observation time was required for sample processing. I learned. Therefore, since the processing time of the sample can be significantly reduced as described above, the time required for cross-sectional observation can be significantly reduced as compared with the related art. Specifically, the cross-section observation time was reduced to about half or less. This effect becomes more remarkable by automating the processing process.

It is assumed that the sample fixing structure according to the present invention is a sample fixing structure processed by FIB. Then, with the stress generated inside the sample, the sample is fixed to the sample holder.

By using such a fixing structure, the sample can be automatically moved after cutting, and the processing time can be reduced.

The method for fixing a sample according to the present invention is a method for fixing a sample to be processed by FIB, and includes the following steps. A stress is generated inside the sample. The sample in the state where the stress is generated is fixed to the sample holder.

By employing the above fixing method, stress can be generated inside the fixed sample, and each sample can be moved after cutting the sample.

The method for fixing the sample may be such that a stress is generated inside the sample after the sample is fixed to the sample holding table.

Even when stress is generated inside the sample after fixing the sample to the holding table as described above, each sample can be moved after cutting the sample, as in the above-described case. As a method of generating stress inside the sample after fixing the sample, for example, a sample holder having a different thermal expansion coefficient from the sample is prepared, and stress is generated in the sample using the difference in thermal expansion between the sample and the sample holder. And a method of deforming the fixed sample.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, an FIB processing apparatus 1 capable of performing a method for observing a cross section of a sample according to the present invention will be described with reference to FIG. As shown in FIG. 1, the FIB processing apparatus 1
An ion source 2, lenses 3a and 3b, an aperture 4,
A stage 6, a detector 7, and a control unit 8 are provided.

The Ga ions from the Ga ion source 2 are focused finely by the lenses 3a and 3b, the aperture 4 and the like, and are irradiated on a sample 5 such as a wire or a plate placed on the stage 6.
Thereby, a desired position of the sample 5 is cut (rough processing),
After processing (medium processing) such that the surface of the sample 5 and the cut surface are substantially perpendicular to each other, finish processing is performed to form an observation surface. Thereafter, the observation surface is irradiated with FIB, and the crystal orientation and the like of the observation surface are observed based on information obtained through the detector 7.

Next, a method for observing a cross section of a sample according to the present invention will be described more specifically with reference to FIG.

Referring to FIG. 2A, a sample 5 which is an ultra-fine wire having a diameter of about several tens of μm is fixed on a sample holding table 10 by a fixing section 9 while a stress is generated inside. I do. The fixing portions 9 are provided on both ends in the longitudinal direction of the sample 5 and are formed by, for example, curing a carbon paste.

In the area 11a shown in FIG.
To cut the sample 5. Since the stress is generated inside the sample 5 as described above, at least one of the free ends of each of the samples 5a and 5b divided by cutting the sample 5 releases the stress as shown in FIG. Move by. As described above, since at least one of the samples 5a and 5b can be moved after the sample 5 is cut, the processing width D1 at the time of cutting the sample 5 may be much smaller than the conventional processing width D2. Thereby, the processing time of the sample 5 can be significantly reduced. Specifically, as shown in FIG.
Since it may be about 3 μm, the processing time can be greatly reduced to about ８ of the conventional one.

Here, the optimum processing width will be described with reference to FIG. The inventors of the present application independently investigated the relationship between the processing time and the processing width of the sample 5, and found that the relationship was 1 μm as shown in FIG.
It has been found that the machining time increases with the following machining widths. In addition, it was also found that when the processing width was smaller than 2.5 μm, the texture of the cut surface was altered. From this result, it was found that a processing width of about 2.5 μm was optimal. In addition, as long as the processing width D1 is smaller than the diameter of the wire, the processing time can be reduced at least compared to the conventional example.

Referring again to FIG. 2B, FIG. 2B shows a case where the sample 5a on the side on which the observation surface is formed is fixed and the other sample 5b moves. This can be realized by cutting the vicinity of the fixing portion 9. At this time, as shown in FIG. 2B, it is preferable to move the free end of the sample 5b to a position where the cut surfaces of the samples 5a and 5b do not face each other. Thereby, cross-section observation can be performed while the processing width D1 is kept small as described above.

Next, the processing position and the amount of movement of the sample 5a on the side forming the observation surface will be described with reference to FIGS.

As shown in FIG. 5, as the distance from the fixed portion 9 increases, the moving amount of the sample 5a on the observation surface forming side also increases. Unless efficiency and automation including the processing in the next step are considered, even if the sample 5a on the side forming the observation surface moves greatly, it is necessary to find the destination manually and perform the processing in the next step. Since it is possible, the processing position does not need to be particularly limited.

However, when considering efficiency and automation including the processing in the next step, it is necessary to devise a cutting position. That is, the sample 5 on the side where the observation surface is formed
It is necessary to adjust the cutting position so that the movement amount of a is within a predetermined value. For example, if the movement amount is within 1.5 μm, it is considered that efficiency and automation including processing in the next step can be performed.

In order to make the moving amount fall within the above range,
According to FIG. 5A, the area within 500 μm from the fixing part 9 may be cut. More preferably, the fixed portion 9 is 50 μm.
Cut within the range of m or less. Thereby, the sample 5a
Can be suppressed to 0.15 μm or less, which can be regarded as substantially zero, and a series of processing processes can be automated without correcting the FIB irradiation position by image recognition.

Since the value of 50 μm is about 2 to 3 times the diameter of the sample 5, when the sample 5 is a wire rod, by cutting a range within 3 times the diameter of the wire, It is considered that the amount of movement of the sample 5a on the side where the observation surface is formed can be extremely small.

Next, a case where the amount of movement of the sample 5 is detected by image recognition and the FIB irradiation position is corrected will be described. In this case, as shown in FIG. 6, the position of the sample 5a on the side where the observation surface is formed after the cutting is cut from the fixed portion 9 so that the sample 5a does not come out of the observation field 13 of, for example, 500 μm square. As a result, the amount of movement can be detected by image recognition,
The FIB irradiation position can be corrected accordingly, and the processing of the sample 5 can be automated.

To perform such automation, the control unit 8 of the FIB processing apparatus 1 shown in FIG.
It is preferable to provide a beam irradiation position control unit. By providing the movement amount detecting means, the movement amount of the sample 5a moved after the cutting processing can be detected, and by providing the beam irradiation position control means, the detected sample 5a can be detected.
The FIB irradiation position can be corrected according to the amount of movement of. By having such a function, the processing of the sample 5 can be automated.

After cutting the sample 5 as described above, the sample holder 10 is tilted and the observation surface 12 is observed, as shown in FIG. In this way, the crystal observation of the cross section of the sample 5 can be performed.

Next, a sample fixing structure and a fixing method according to the present invention will be described with reference to FIGS.

First, referring to FIG. 7, the sample 5 is fixed to the sample holder 10 by the fixing unit 9 with tension applied to both ends of the sample 5, and then the tension is released and removed. Thereby, stress is generated inside the sample 5 located between the fixing portions 9.

Next, as shown in FIGS. 8A and 8B, the sample holder 10 is connected to the first and second sample holders 10a and 10a.
0b, each of which is movable. After the sample 5 is fixed to the first and second sample holding tables 10a and 10b, they are moved. Thereby, a stress is generated inside the sample 5.

Further, after fixing both ends of the sample 5 to the sample holder 10 as shown in FIG. 9, a part of the sample 5 may be displaced and fixed. Also in this case, stress can be generated inside the sample 5.

Further, as shown in FIG. 10, a concave portion 15 is provided in the sample holder 10, and after fixing the sample 5 to the sample holder 10, a part of the sample 5 is pushed into the concave portion 15 from above by a weight 14 or the like. May be deformed. Again, in this case,
Stress can be generated inside the sample 5.

Further, as shown in FIG. 11, the sample holder 10 is divided into first and second sample holders 10a and 10b.
One may be configured to be tiltable with respect to the other. FIG.
As shown in FIG. 11A, the sample 5 is fixed across the first and second sample holders 10a and 10b in a state where the second sample holder 10b is inclined, and then as shown in FIG. 11B. The second sample holder 10b is displaced downward. Thereby, tension is applied to the sample 5, and stress can be generated inside the sample 5.

Further, as shown in FIGS. 12A and 12B, the sample 5 may be fixed to the sample holding table 10 in a state where a loop portion or a bent portion is provided. Also in this case, sample 5
Stress can be generated inside.

As described above, by fixing the sample 5 to the sample holders 10, 10a and 10b in a state where a stress is generated inside, the free end of the sample 5 can be displaced after cutting.

The fixing structure and the fixing method shown in FIGS. 7 to 12 are merely examples, and the present invention is not limited thereto. Stress may be generated inside the sample 5 by a method other than the above. For example, a material having a different thermal expansion coefficient from that of the sample 5 may be selected as the sample holding table 10, the temperature of the surrounding may be increased after the sample 5 is fixed, and a stress may be generated inside the sample 5 due to a difference in thermal expansion.

Although the embodiments of the present invention have been described above, it should be understood that the embodiments disclosed herein are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims, and includes all modifications within the scope and meaning equivalent to the claims.

[0056]

As described above, according to the present invention, the free end of the sample can be moved after cutting the sample by FIB, so that the processing time of the sample can be significantly reduced. Thereby, the total time required for observing the cross section of the sample by the FIB can be significantly reduced as compared with the conventional case. Specifically, the total required time can be reduced to about 1/2 to 1/3.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an FIB processing apparatus capable of performing cross-sectional observation by FIB according to the present invention.

FIGS. 2A to 2C are views showing a method for observing a cross section of a sample by FIB according to the present invention.

FIG. 3 is a diagram showing a relationship between a cutting width of a sample and a processing time.

FIG. 4 is a diagram showing a change in processing time in a processing width of 5 μm or less.

FIG. 5A is a diagram illustrating a relationship between a moving amount of a sample on a side where an observation surface is formed and a cutting position from a fixed portion.
(B) is a diagram showing the concept of the amount of movement and the distance from the fixed part in (a).

FIG. 6 is a diagram showing a movement of a sample within an observation visual field.

FIG. 7 is a plan view showing an example of a method for fixing a sample.

FIGS. 8A and 8B are plan views showing another example of a method for fixing a sample.

FIG. 9 is a plan view showing still another example of a method for fixing a sample.

FIG. 10 is a cross-sectional view showing still another example of a method for fixing a sample.

FIGS. 11A and 11B are side views showing still another example of a method for fixing a sample.

FIGS. 12A and 12B are plan views showing still another example of a method for fixing a sample.

13 (a) to 13 (c) are views showing a conventional cross-sectional observation method using FIB.

FIG. 14 is a view showing a problem in a conventional section observation method using FIB.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 FIB processing apparatus 2 Ga ion source 3a, 3b Lens 4 Aperture 5, 5a, 5b Sample 6 Stage 7 Detector 8 Control part 9 Fixed part 10 Sample holder 10a First sample holder 10b Second sample holder 12 Observation surface 13 Observation field of view 14 Weight 15 Recess

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Shigemitsu Kusachi, 1-3-1 Shimaya, Konohana-ku, Osaka-shi F-term in Osaka Works, Sumitomo Electric Industries, Ltd. (Reference) 4E066 AA01 BA13 BD01 BD04 CA14

Claims (12)

[Claims] A step of fixing a sample to a sample holding table in a state in which stress is generated therein; cutting the sample with a focused ion beam; and releasing one of the samples to the other of the samples by releasing the stress. A method for cutting a sample by a focused ion beam, comprising: 2. The sample cutting method using a focused ion beam according to claim 1, wherein only the one sample is moved while the other sample is fixed. 3. The method according to claim 1, wherein the one sample is moved to a position where the cut surface of the one sample and the cut surface of the other sample do not face each other. . 4. The sample cutting method using a focused ion beam according to claim 1, wherein a position within 500 μm from the fixed portion of the sample is cut. 5. The method for cutting a sample using a focused ion beam according to claim 1, wherein a position within 50 μm from the fixed portion of the sample is cut. 6. An observation surface is formed on the other sample, the observation surface is observed through an observation field, and the sample is cut so that a cut surface of the other sample remains in the observation field after cutting. A method for cutting a sample using a focused ion beam according to claim 1. 7. The method for cutting a sample using a focused ion beam according to claim 1, wherein the sample is a wire or a plate. 8. The method for cutting a sample using a focused ion beam according to claim 1, wherein the sample is a wire rod, and a portion within a length of three times the diameter of the sample is cut from a fixing portion of the sample. 9. A cross-sectional observation method using a focused ion beam, comprising: fixing a sample to a sample holding table in a state where stress is generated therein; and cutting the sample by the focused ion beam to release the stress. A step of moving one sample relative to the other sample, a step of inclining the sample holding table, and a step of observing a cross section by irradiating the other sample with a focused ion beam, , A cross-section observation method. 10. A fixing structure for a sample to be processed by a focused ion beam, wherein the sample is fixed to a sample holding table in a state where stress is generated inside the sample. . 11. A method of fixing a sample to be processed by a focused ion beam, wherein: a step of generating a stress inside the sample; and a step of fixing the sample in a state where the stress is generated to a sample holding table; A method for fixing a sample, comprising: 12. A method for fixing a sample to be processed by a focused ion beam, comprising: a step of fixing the sample to a sample holder; and a step of generating a stress inside the sample after fixing the sample. Also, how to fix the sample.