JPH08304243A - Sample having cross sectional thin-film, its manufacture, and its holder - Google Patents

Abstract

PURPOSE: To provide a sample which has a cross sectional thin-film and the specific part of which can be analyzed at once in two direction, its manufacturing method, and its holder. CONSTITUTION: An area 1 of a material including a specific part is machined in a project-like or island-like state and two or more thin film sample pieces 3 inclined against each other are manufactured in the radial direction from a certain point in the specific part by drilling the material with a converged ion beam 5. A holder which holds the sample pieces 3 is constituted of a sample fixing bar 11 provided with an O-ring 15 for maintaining a TEM sample chamber in a vacuum when the bar 11 is inserted into the sample chamber, supporting bar 12 which supports the bar 11, ring 16 fitted to the front end section of the bar 11 in a tiltable state, and disk 17 which is rotatably supported by the ring 16 and can fix the sample pieces 3. Therefore, at least two or more different samples which can be observed and have cross sectional thin-films can be manufactured in the specific part of the material and the specific part can be analyzed collectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross-section thin film used for structural analysis and composition analysis, a method for producing the same, and a cross-section thin film sample holder.

[0002]

2. Description of the Related Art The structural analysis and composition analysis techniques of materials are very important for understanding the material properties (electrical, mechanical properties, etc.). X-ray analyzers, electron microscopes, Auger electron spectrometers, secondary ion mass spectrometers, etc. have been used. Among them, Transmission Electron Microscop
e; hereinafter abbreviated as TEM. ) Is applied to many material developments as an apparatus for analyzing the morphology, structure and composition in the micro region of a material.

In many cases, this sample for TEM observation is
It was produced by the electrolytic polishing method or the ion milling method.
However, since these methods make it difficult to sample a specific portion of the material, direct observation of the specific portion is impossible.

On the other hand, in order to solve the above problem, a method for producing a cross-sectional thin film sample for TEM observation at a specific location using a focused ion beam (electron microscope, 28 (1993) 119 "FI
New TEM sample preparation method using B ", JP-A-6-2
31719) is being considered. A cross-section thin film at a specific location is obtained by a method of machining the sample surface including the specific location and performing fine processing with a focused ion beam.

However, in the above method, the processing size is only suitable for producing a thin film of a cross section by a focused ion beam in only one direction with respect to a specific location, and the processing area is very large in other directions. Only a thin film sample with one cross section could be prepared. Therefore, in the conventional sample preparation method, it was not possible to prepare at least two cross-sectional thin film materials having different directions with respect to a specific location. For this reason, structural analysis and composition analysis in two or more directions at once can be performed on specific locations that were previously required, such as analysis of precipitates in steel materials and failure locations in semiconductor integrated circuits. There was a problem that it was impossible.

[0006]

In view of the problems of the prior art as described above, the main object of the present invention is to provide a sample holder in which at least two cross-sectional thin film samples having different directions are prepared at a specific location. It is an object of the present invention to provide a cross-sectional thin film sample that can be supported and efficiently perform structural analysis and composition analysis, a method for manufacturing the same, and a cross-sectional thin film sample holder.

[0007]

According to the present invention, such an object is provided in the convex and island-shaped region including a specific portion for performing structural analysis and composition analysis of a material. A cross-section thin film sample characterized by forming at least two cross-section thin films radially existing from one arbitrary point of a particular place and forming an angle with each other, or a region including a particular part of a material having a convex and island shape After pre-machining into a sample shape, drilling is performed with a focused ion beam or laser to produce at least two or more cross-sectional thin-film portions that are radially present at an arbitrary point within the specific location and form an angle with each other. A method for producing a thin film sample having a cross section, or a sample fixing device comprising an O-ring for fixing a sample and holding a vacuum when the holder is inserted into a sample chamber of a transmission electron microscope. And a support rod for supporting the sample fixing rod, the tip of the sample fixing rod, a disk having a mechanism capable of fixing the sample and rotatable, and supporting the disk and This is achieved by providing a holder for a thin film sample having a cross section, which is provided with a ring supported at two points with respect to the sample fixing rod so as to be tiltable.

[0008]

By doing so, at least two cross-sectional thin film samples, which have different directions from each other, are obtained at a specific location.
It is possible to fabricate one or more of them, and it is possible to simultaneously observe cross-sections with different angles at the same place, and it is possible to analyze the crystal structure by an electronic analysis method that grasps the morphology of a three-dimensional specific place. In addition, by using a composition analysis technique such as characteristic X-ray energy dispersive spectroscopy (EDS) or electron energy loss spectroscopy (EELS) mounted on an electron microscope, it is possible to obtain a small area for each thin film of a cross section at a specific location. It is possible to determine the composition of, and a comprehensive characterization of specific points is realized. For example, by applying it to the analysis of a failure point in a semiconductor integrated circuit, it becomes possible to examine the cause of the failure from various viewpoints.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 (a) is a bird's-eye view of the entire sample showing the procedure for preparing the sample according to the present invention, so that the position of the specific portion can be recognized when processing the sample with respect to the region 1 including the specific portion. , Marking 2 is applied to the surrounding area by marking or the like. The marking 2 may be of any size and shape that can recognize a specific portion during cutting.

Next, the sample piece 3 is cut from the material having the marking 2 by a precision cutting machine such as a dicing saw. At this time, cutting is performed so that the region 1 including the specific portion has a convex shape and is located near the center of the sample piece 3. FIG.
(B) is the figure which showed the cutting procedure, A and B have shown the vertical and horizontal width of the sample piece 3, and C and D have shown the vertical and horizontal width of the convex area | region. The sizes of A and B are such that the sample can be fixed with a sample holder for TEM observation after processing, and
The size is such that it can be inserted into the sample chamber of the EM. On the other hand, the sizes of C and D are determined by the size of a specific place to be observed.

First, with respect to the Y direction which is the vertical direction of FIG. 1B, the surface of the region on the left and right sides in the width A excluding the broken line region is adjusted to an appropriate depth at which a specific portion can be observed. Shave shallowly. Next, X, which is the left-right direction in FIG.
The region 1 is left in the width B with respect to the direction, and the region is shallowly cut to the same depth as the process performed in the Y direction. In this way, the cross-sectional thin film having different directions is formed in the region 1 including the specific portion.
One or more convex shapes (convex in the front direction in the figure) and island shapes are machined in advance. Next, the lines indicated by four imaginary lines are cut to separate the sample piece 3 from the entire sample.

2 (a) and 2 (b) are a bird's-eye view and a side view of the sample piece 3 machined by the above-mentioned method. The dimension E is the thickness of the sample piece 3, and its size is subject to the same restrictions as A and B described above.

Next, there will be described a method of determining a processing position for a convex region including a specific portion by using a focused ion beam, a laser or the like, and performing fine processing for producing a thin film in a cross section.

First, a method of determining the processing position will be described. When the surface of the sample 3 is irradiated with the focused ion beam, secondary electrons are generated from the surface. By detecting and imaging this secondary electron, a secondary electron image corresponding to the morphology of the sample surface can be obtained. From this secondary electron image, the position of a specific place in the convex region is grasped, and the specific processing position for forming the cross-sectional thin film is determined. It should be noted that in determining the processing position, an ion beam having a sufficiently weak intensity that does not process the sample surface is used.

Next, a specific procedure of fine processing with a focused ion beam will be described. FIG. 3A is a bird's-eye view of the convex region 1 processed into a convex shape and an island shape as shown in FIG. For the three blank areas 4a, 4b, and 4c not hatched in FIG.
As shown in (b), drilling is sequentially performed with the focused ion beam 5. At the time of drilling, first, rough drilling is performed with a large beam diameter, then the beam is converged finely, and medium processing is performed. Further, the beam is focused and fine finishing is performed. In particular, in the middle processing and finishing processing, in order to obtain a smooth cross-section thin film sample 6, the focused ion beam 5 is scanned parallel to the cross section.

In this manner, it is possible to manufacture the cross-sectional thin film 6 having a thickness of about 0.1 μm, which enables image observation, structure analysis and composition analysis in two different directions. In addition, F
And G are the widths of the thin film in cross section, and depend on the size of a specific portion. 7a and 7b are walls for the purpose of supporting the cross-sectional thin film sample 6 and protecting it against damage.

FIG. 3B is a perspective view showing an example of the convex region 1 after fine processing, and J in the drawing is a processing depth, which is determined by the size of the specific portion 8. The thickness of the cross-sectional thin film sample 6 is preferably 0.1 μm or less. This is because if the film thickness is 0.1 μm or more, it becomes difficult to perform image observation and structural analysis with a TEM at an acceleration voltage of 200 kV that is normally used.

When the widths of F and G are small, the ions constituting the surface of the sample are redeposited and deposited on the opening or the side wall during the ion beam processing, and the structural analysis or composition analysis of the thin film sample 6 in cross section is performed. It may be a hindrance to and needs attention.

Further, by the above-mentioned manufacturing method, the specific portion 8
On the other hand, cross-section thin film samples 9a, 9b, 9c in three directions as shown in FIG. 4A, or cross-section thin film samples 10a, 10b, 10c, 10d in four directions as shown in FIG. 4B.
Can also be manufactured.

Next, the sample holder for TEM of the present invention will be described below with reference to FIG. The sample holder includes a sample fixing rod 11, a supporting rod 12, and a grip 13.

The sample fixing rod 11 is a rod that directly supports the sample piece 3 at its tip, and has a diameter and a length that can be inserted between the objective lenses in the TEM sample chamber. The support rod 12 is a TEM
The size is set so that it can be inserted into the sample chamber, and the length thereof is especially set when the sample piece 3 is fixed to the tip of the sample fixing rod 11.
4 (see FIG. 3 (b)) has a length such that it can be appropriately incident on the cross-sectional thin film sample 6. In addition, the support rod 12 has
An O-ring 15 is provided at an appropriate position in order to maintain a vacuum when it is inserted into a TEM sample chamber which is a high vacuum. The grip portion 13 is for facilitating insertion and removal of the sample holder into and from the TEN sample chamber, and it is preferable to provide the grip portion 13 in this sample holder. As a material for the sample fixing rod 11 and the supporting rod 12, a non-magnetic and easily workable metal material such as A1 is suitable.

5 (b) and 5 (c) are views showing the structure of the tip of the sample fixing rod 11, and as shown in the figure, a ring 16 is provided at the tip of the sample fixing rod 11. And disk 1
7 are provided. The ring 16 is supported at two points on the tip of the sample fixing rod 11 so as to be tiltable around an axis orthogonal to the axis of the sample fixing rod 11 as shown by an arrow K in FIG. As shown in, the sample fixing rod 11
When the axis line of is the X axis, it can be inclined up to 90 degrees with respect to the plane including the X axis. Further, the disk 17 is the ring 1
6 is mounted via a rotating mechanism, and is capable of rotating 360 degrees in the end face of the ring 16. The diameter of the circular plate 17 is set so that the fixing surface of the sample piece 3 does not contact the ring 16 when the sample piece 3 is fixed. This ensures smooth rotation of the sample piece 3. The processed sample piece 3 is fixed to the circular plate 17 so that the convex region 1 where the cross-sectional thin film sample 6 is present at a specific position faces upward. Disk 1
The sample piece 3 can be fixed to the sample 7 by applying an electrically conductive adhesive or using an electrically conductive adhesive tape.

The tilting mechanism of the ring 16 and the rotating mechanism of the circular plate 17 make it possible to easily change the electron beam 14 to a position where the electron beam 14 is appropriately incident on each thin film in cross section. That is, the newly developed sample holder enables efficient image observation, structural analysis and composition without changing the sample piece 3 to the sample holder for each observation for each thin film sample 6 having a different direction at a specific location. Analysis is realized.

Furthermore, in the focused ion beam device, as shown in FIG.
When the sample holder for TEM shown in (a) is inserted, a sample stage capable of supporting the sample holder is provided so that the focused ion beam 5 is attached with the sample piece 3 at the machining stage attached to the tip of the TEM holder. Can be processed. Furthermore, after processing, it is not necessary to remove the sample piece 3 from the holder, and the sample piece 3 can be directly inserted into the TEM, and the cross-sectional thin film sample 6 can be observed quickly.

FIG. 5B is an enlarged view of the tip of the holder during machining with the focused ion beam 5. First, the machined sample piece 3 is fixed to the disk 17 at the tip of the holder so that the convex region 1 in which the specific portion is present faces upward. For fixing, a conductive adhesive is applied or a conductive adhesive tape or the like is used. Next, the holder is inserted into the sample chamber of the focused ion beam apparatus. After that, the ring 16 is tilted so that the focused ion beam 5 is appropriately irradiated to the convex region 1 including the specific portion, and the cross-sectional thin film sample 6 is formed in the convex region by drilling with the focused ion beam 5. After the processing is completed, the sample holder is taken out from the focused ion beam device.

Next, in order to observe and analyze the cross-section thin film sample 6, the sample holder is inserted into the TEM. FIG. 5 (c) shows
It is an enlarged view of the tip of a sample holder at the time of TEM observation. Ring 1 which was almost horizontal when processed by focused ion beam 5
6 is tilted to a position where the electron beam 14 can be appropriately incident,
Further rotation of the disk 17 enables image observation and composition analysis of each cross-section thin film sample piece 6.

As a result, not only the work from sample preparation to TEM observation can be performed efficiently, but also the sample can be directly exchanged between the focused ion beam device and the TEM via the holder. Can be observed each time, and each cross-sectional thin film sample 6 can be realized to have an appropriate sample thickness for TEM observation.

The sample produced according to the present invention is T
Not only EM but also a sample for a scanning electron microscope or an Auger electron spectroscope can be used for analysis.

FIG. 6 is a diagram showing an embodiment of the present invention. FIG. 6A is a schematic view of a portion of the Al wiring in the semiconductor integrated circuit where the poor conductivity occurs, and the hatched area in the drawing is the Al wiring 21. A sample was shaped from this sample by mechanical polishing with a dicing saw, and a cross-sectional thin film was formed at a position indicated by a broken line in FIG. 6A by a focused ion beam device. Roughly drilling was performed with a beam diameter of about 1 μm, and then medium processing was performed with a beam diameter of about 0.5 μm. Further, finishing processing was performed with a beam diameter of about 0.05 μm or less.

Thereafter, this sample was fixed to the tip of the sample holder according to the present invention with silver paste, dried, and then imaged of the defective portion was observed by TEM and composition analysis by EDS was performed.

FIGS. 6 (b) and 6 (c) are TEM images of two cross-section thin film samples, in which 22 is an insulating film, 23 is an abnormal contrast portion, and 24 is a Si substrate. is there. In both figures, an abnormal contrast portion 23, which is considered to be a compound, was observed at the Al / Si substrate interface in the images.

Next, an EDS analysis was performed to clarify the composition of the abnormal contrast portion 23. Figure 6
6D shows E of the abnormal contrast portion 23 in FIG. 6B.
It is a DS analysis result. From this EDS spectrum, it was found that the abnormal contrast portion 23 was composed of Al and Si. From the above analysis, it was clarified that the poor conductivity was due to the formation of the compound phase of Si and Al at the Al wiring / Si substrate interface.

As described above, according to the present invention, it is possible to quickly observe a defective portion from two directions, and it is also possible to perform elemental analysis of a minute portion of a specific portion. Further, it can be said that the material manufacturing method developed this time is also effective for failure analysis of semiconductor devices through the examples.

[0035]

As described above, according to the present invention, it is possible to prepare at least two cross-sectional thin film samples in different directions in which observation is possible at a specific portion of a material, and comprehensive structural analysis of the specific portion is possible. And compositional analysis decisions can be realized. In addition, the newly developed sample holder enables quick analysis of the prepared sample. Further, until now, in order to produce two or more cross-sectional thin film samples having different directions, it was necessary to produce each cross-sectional thin film sample one by one. Since it is possible to manufacture one or more thin-film cross-section samples, it is possible to significantly reduce the sample preparation time. Further, by using the sample holder for fixing the above-prepared cross-sectional thin film sample, efficient image observation, structure analysis and composition analysis are possible.

[Brief description of drawings]

FIG. 1 (a) is a bird's-eye view of the entire sample showing a procedure for producing a sample based on the present invention, and FIG. 1 (b) is a view showing a procedure for cutting a sample piece.

2A is a bird's-eye view of a sample piece 3 in which a convex region is machined, and FIG. 2B is a side view of FIG.

FIG. 3A is a bird's-eye view of a convex region, and FIG. 3B is a perspective view showing an example of the convex region after fine processing.

FIG. 4 (a) is a bird's-eye view similar to FIG. 3 (a) showing an example in which a cross-sectional thin film sample is prepared in three directions, and FIG. 4 (b) is a diagram showing an example in which a cross-sectional thin film sample in four directions is prepared. A bird's-eye view similar to (a).

5A is an overall view showing the structure of a sample holder for fixing a cross-sectional thin film sample of the present invention, FIG. 5B is an enlarged view of the tip of the holder during sample processing, and FIG. Enlarged view of the tip of the holder at the time.

6A is a schematic diagram of a sampling position of a sample, FIG. 6B is a diagram showing one cross section of the sample, FIG.
(C) is a diagram showing the other cross section of the sample,
(D) is a copy of the TEM image and the EDS composition analysis result.

[Explanation of symbols]

 1 area 2 marking 3 sample piece 4a, 4b, 4c area 5 focused ion beam 6 cross-section thin film sample 7a, 7b wall 8 specific location 9a, 9b, 9c cross-section thin film sample 10a, 10b, 10c, 10d cross-section thin film sample 11 sample fixing rod 12 Support Rod 13 Grip 14 Electron Beam 15 O Ring 16 Ring 17 Disc 21 Al Wiring 22 Insulating Film 23 Abnormal Contrast 24 Si Substrate

Claims (3)

[Claims] 1. In a region formed in a convex shape and in an island shape including a specific portion for conducting structural analysis and composition analysis of a material, radial points are present from any one point of the specific portion and form an angle with each other. A cross-sectional thin film sample, characterized in that at least two cross-sectional thin films are formed. 2. A region including a specific portion of the material is pre-machined into a convex and island-shaped sample shape, and then a hole is drilled by a focused ion beam or laser to select from any one point within the specific portion. A method for producing a cross-section thin-film sample, characterized in that at least two cross-section thin-film portions that radially exist and form an angle with each other are produced. 3. A sample fixing rod provided with an O-ring for fixing a sample and holding a vacuum when the holder is inserted into a sample chamber of a transmission electron microscope; and a sample fixing rod for supporting the sample fixing rod. A disc having a supporting rod and a mechanism capable of fixing and rotating the sample at the tip of the sample fixing rod, and the sample fixing rod for supporting and tilting the disc. A holder for a thin film sample having a cross section, comprising: a ring supported at two points.