JP3028078B2 - Sample for transmission electron microscope and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample for a transmission electron microscope having a specific structure used for performing energy dispersive x-ray analysis of the sample using a transmission electron microscope.
And a method for preparing the sample.

[0002]

2. Description of the Related Art Conventionally, a sample for this type of transmission electron microscope and a method for producing the sample are disclosed in, for example,
As shown in Japanese Patent No. 61132, a sample is sliced by a focused ion beam or the like, and a cross section is observed using a transmission electron microscope. FIG. 10 is a schematic diagram showing an example of a conventional sample for a transmission electron microscope.

As shown in FIG. 10, a section including a measurement area is selectively and uniformly formed thin from a sample surface to about 1000 angstroms using a focused ion beam, and a section perpendicular to the plane of the section is provided. And a groove 3 serving as a passage for the electron beam 6 in any direction. Further, the cross section is supported by the thick regions 2 of the sample on both sides of the groove.

[0004] When processing a sample in which the measurement area is located in a very limited area into a sample for a transmission electron microscope, this sample preparation method is considered in terms of ease of location and relatively high strength of the sample itself. Is an effective method.

[0005]

Using a sample produced by the prior art described above [0004], regarding the problem in the case of performing energy dispersive characteristic x-ray analysis, it will be described with reference to FIG. 10. The sample manufactured by the conventional technique has a structure in which a cross-sectional portion serving as a measurement region is supported by the thick region 2 of the sample on both sides of the groove 3.

For this reason, the electron beam 6 incident from just above the sample corresponds to the electron beam transmitted through the sample and the sample, and the characteristic x-ray 7 excited by the reflected electron 9, the scattered electron 10, or the electron beam 6 is formed into a groove. 3 may be incident on the thick region 2 of the sample on both sides. When the reflected electrons 9 and the scattered electrons 10 enter the thick region 2 of the sample, the characteristic x-rays of the constituent material are excited.

On the other hand, when a characteristic x-ray 7 having a large energy is emitted from the measurement region and enters the thick region 2 of the sample on both sides of the groove 3, the characteristic x-ray 8 of the constituent material in that portion is emitted by fluorescence excitation. . Therefore, the characteristic x-rays of the constituent material in the thick region 2 of the sample are captured by the x-ray detector 13.

Therefore, when the material in the measurement region 1 is the same as the material in the thick region 2 of the sample, the spectrum obtained by the energy dispersive characteristic x-ray analysis shows that the characteristic x-rays due to the constituent elements of the measurement region and the thick sample There is a problem that the characteristic x-ray peaks of the constituent elements in the region 2 overlap and a large error occurs in the quantitative result of the composition ratio.

An object of the present invention is to provide a sample having a measurement area in a very limited area without the above-mentioned problems by using a transmission electron microscope and performing energy dispersive x-ray analysis to obtain an accurate composition. capable of performing quantitative ratio, transmission electron microscope sample having a specific structure, and to provide a manufacturing method of the sample.

[0010]

The above objects and objects are solved and achieved by the present invention described below.

That is, the present invention provides a sample for a transmission electron microscope having irregularities , wherein a region other than the measurement region is covered with a film made of a substance different from the element constituting the measurement region. The present invention discloses a sample for a transmission electron microscope, characterized by having a configuration described above.

In the transmission electron microscope sample according to the present invention, the thickness of the sample is increased temporarily between the plane including the thinly formed measurement region and the crossing portion to the plane perpendicular to the plane including the measurement region. And a coating made of a substance of an element different from the element of the substance constituting the measurement region, characterized in that the coating is a metal film. The film thickness of the metal film is not less than 3000 angstroms, and the characteristic x-ray spectrum of the metal film is at least the characteristic x-ray spectrum of the element of the substance constituting the measurement region. The difference is at least 0.5 keV.

[0013] The present invention also provides a method for removing irregularities for a transmission electron microscope.
A method of manufacturing a sample having a step of selectively removing a part of the sample to a measurement region from both sides of the sample sandwiching a measurement region inside the sample, an element different from an element of a substance constituting the measurement region Depositing the substance on the sample,
A step of removing a substance of an element different from an element of a substance constituting the measurement area on both surfaces of the measurement area, wherein the method for preparing a sample for a transmission electron microscope is disclosed. .

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

The sample for a transmission electron microscope and the method for preparing the sample according to the present invention make it possible to improve the accuracy of quantitative determination of the composition ratio in energy dispersive x-ray analysis. More specifically, a means is provided in which the entire surface of the sample is covered with a substance that emits characteristic x-rays other than the constituent elements of the measurement region up to the vicinity of the measurement region.

In the sample form of the present invention, the sample is processed so as to cover up to the vicinity of the measurement area with a substance made of an element different from the constituent element of the measurement point. Secondary characteristic x-rays of the region,
It is possible to avoid the influence of characteristic x-rays in other regions due to fluorescence excitation.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments based on the drawings, but the present invention is not limited to these embodiments.

Embodiment 1 A first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a sample is cut out of a wafer or chip or the like in a convex shape using a dicing saw or the like so as to include the measurement region 1. The length of the sample is about 3 mm and the thickness is about 150 microns so that it can be accommodated in the holder of the transmission electron microscope.
The height of the convex region is about 50 microns, and the width is 30.
Make it about micron.

FIG. 2 is a schematic view showing an enlarged image of a projection including a measurement area. Etching is performed as shown by a dotted line from both directions of the measurement region using a focused ion beam or the like to form a groove 3 (see FIG. 3) serving as an electron beam passage supported by the thick region 2 of the sample. At this time, the thickness of the cross section including the measurement region is set to about 2000 angstroms in anticipation of the final finishing step.

FIG. 3 shows an enlarged image of the convex portion after the formation of the groove. Sputter or C on all surfaces of the sample after groove formation
Films 4 of elements such as Au and Pb by VD etc. (see FIG. 4)
Is deposited on the order of 3000 angstroms or more.

Here, the reason why Au and Pb were selected is that the spectrum of the characteristic x-ray of Au and Pb is equal to the spectrum of the characteristic x-ray of Si, As, P and Br constituting the wafer and the chip. This is to avoid overlapping of the peaks of the measured spectrum because they are separated by 5 keV or more.

The reason for depositing these metal films over 3000 angstroms is that reflected electrons, scattered electrons, and characteristic x-rays from the measurement region do not pass through the deposited film, so that characteristic x-rays from the sample outside the measurement region are not transmitted. This is because no occurrence occurs. The upper limit of the deposited film thickness of the metal film is determined by the measurement region, the components of the sample outside the measurement region, and the like.

The sample on which the thin film has been deposited is finally finished. Although it depends on the range of the measurement region, it is desirable that the region to be etched be as small as possible at the time of final finishing in order to avoid generation of characteristic x-rays from a portion other than the measurement region. The final finishing is performed by removing the film deposited around the measurement area with a focused ion beam or the like. As a result, the film is locally removed, and the sample having a thickness of about 1000 angstroms in the cross section of the sample including the measurement region (FIG. 5)
See).

FIG. 6 shows a case where energy dispersive x-ray analysis was performed using the transmission electron microscope sample of this embodiment.
This will be described with reference to FIG. Observation surface 5 of the sample after final finishing
(See FIG. 5).
Is incident. At this time, characteristic x-rays of the constituent elements of the measurement region are emitted from the measurement region. When a characteristic x-ray having high energy of about 10 keV is incident on a thick region of the sample supporting the cross section, and when the element existing in the thick region 2 of the sample supporting the cross section and the element present in the measurement region are the same, The characteristic x-rays 8 having the same energy are emitted by the fluorescence excitation.

Further, characteristic x-rays in the thick region 2 of the sample supporting the cross section are also generated by the reflected electrons 9 and the scattered electrons 10. For this reason, as shown in FIG. 8, the peak of the characteristic x-ray in the thick region of the sample and the peak of the characteristic x-ray in the measurement region overlap. However, in the sample structure of the present invention,
In order to deposit a film of a different material on the thick region of the sample supporting the cross section, characteristic x-rays having different energies than the elements present in the measurement region are emitted. As a result, overlapping of peaks can be avoided as shown in FIG.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 7, a thick region 2 of the sample supporting the measurement region is formed in a C shape.
By adopting such a sample shape, the coverage of the film deposited on the sample surface is increased, and the sample is easily manufactured.
Further, since the thick region of the sample is separated from the measurement region, the overlap of peaks on the spectrum is suppressed secondarily.

When the components in the measurement area are unknown, it is needless to say that the measurement can be performed in a state where nothing is deposited on the sample, the components are quantitatively measured, and a film to be deposited is selected based on the results. No.

[0028]

The first effect is that the energy dispersion type characteristic x
In the line analysis method, the quantitative accuracy in determining the composition ratio is improved. The reason is that, since the portion other than the measurement region is covered with the thin film of another element, the overlap between the characteristic x-ray peak emitted in the portion other than the measurement region and the characteristic x-ray peak emitted in the measurement region is avoided. This is because you can do it.

The second effect is that damage to the sample is reduced. The reason for this is that, since a portion other than the measurement region is covered with the thin film, the thickness of the sample increases to the vicinity of the measurement region, and the strength of the sample against impact increases.

[0030] The present invention as described above, to the sample the presence of the measurement region in a very limited area, using a transmission electron microscope, by performing the determination of the exact composition ratio by energy dispersive characteristic x-ray analysis A remarkable effect is obtained that an excellent sample for a transmission electron microscope that can be obtained and a specific method for producing the sample can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the whole of a cut sample.

FIG. 2 is a schematic diagram showing a part of a sample before etching including a measurement region.

FIG. 3 is a schematic view showing a part of a sample subjected to an etching process.

FIG. 4 is a schematic view showing a part of a sample after film deposition.

FIG. 5 is a schematic diagram showing a part of a sample after removing a film in a measurement region.

FIG. 6 is a schematic diagram illustrating an effect when a sample according to the present invention is used.

FIG. 7 is a schematic diagram showing a sample shape according to another embodiment.

FIG. 8 is an EDS spectrum diagram obtained by a conventional sample structure.

FIG. 9 is an EDS spectrum diagram obtained with the sample structure of the present invention.

FIG. 10 is a schematic diagram illustrating an effect when a sample according to a conventional example is used.

[Explanation of symbols]

 Reference Signs List 1 measurement region 2 thick region of sample supporting measurement region 3 groove through which electron beam passes 4 deposited film 5 region where film is removed 6 electron beam 7 generated characteristic x-ray 8 x-ray generated by fluorescence excitation 9 Backscattered electrons 10 scattered electrons 11 peaks created by characteristic x-rays 12 peaks of characteristic x-rays of the elements of the deposited film 13 x-ray detector

Claims (6)

(57) [Claims] 1. A sample for a transmission electron microscope having irregularities , wherein a region other than a measurement region is covered with a film made of a substance of an element different from an element of a substance constituting the measurement region. A sample for a transmission electron microscope, characterized in that: 2. A plane including a thinly formed measurement region,
The sample for a transmission electron microscope according to claim 1, characterized in that the sample has a configuration in which the thickness is temporarily increased between the transfer portions to a plane perpendicular to a plane including the measurement region. 3. The sample for a transmission electron microscope according to claim 1, wherein the coating made of a substance of an element different from the element constituting the measurement region is a metal film . 4. The sample for a transmission electron microscope according to claim 3, wherein the thickness of the metal film is 3000 angstroms or more. 5. The characteristic x-ray spectrum of the metal film is:
4. The sample for a transmission electron microscope according to claim 3, wherein the sample is different from the characteristic x-ray spectrum of an element of the substance constituting the measurement region by at least 0.5 keV. 6. A method for producing a sample having projections and depressions for a transmission electron microscope, the method comprising selectively removing a part of the sample from both sides of the sample sandwiching the measurement region inside the sample to the measurement region. A step of depositing a substance of an element different from the element of the substance constituting the measurement area on the sample, and a step of removing a substance of an element different from the element of the substance constituting the measurement area on both surfaces of the measurement area. A method for preparing a sample for a transmission electron microscope, comprising: