JP7567415B2 - Electron microscope analysis method - Google Patents

Description

The present invention relates to an analysis method using an electron microscope.

Electron microscopes are used to obtain magnified images of objects to be measured. Known types of electron microscopes include scanning electron microscopes (SEM), transmission electron microscopes (TEM), and scanning transmission electron microscopes (STEM). Test methods for SEMs are also specified, as described in Non-Patent Document 1.

JIS K 0132:1997 "General Rules for Scanning Electron Microscope Test Methods"

Electron microscopes are used to perform detailed analysis of objects to be measured. However, the inventors of the present invention encountered a situation in which detailed analysis using an electron microscope was difficult. Specifically, the inventors of the present invention encountered such a difficult situation when inspecting intermediate or final products on a production line for manufacturing at least one of metal particles and metal oxide particles.

When the amount of metal particles and/or metal oxide particles to be produced within a given period of time is relatively small, the speed at which the particles are produced can be low, and detailed analysis using an electron microscope does not have a significant effect on the overall production process.

On the other hand, when the amount of metal particles and/or metal oxide particles to be produced within a given period of time is relatively large, the speed at which the particles are produced must be increased, which means that many analyses must be performed in a limited time. In such a situation, if electron microscope inspection takes too long, the inspection becomes a bottleneck in the overall manufacturing process, and there is a risk that the target production volume will not be achieved. However, if electron microscope analysis is oversimplified, if not omitted, then it becomes difficult to guarantee the quality of the intermediate or final product of metal particles and/or metal oxide particles.

The objective of the present invention is to perform appropriate analysis using an electron microscope regardless of the number of analyses to be performed within a given period of time.

The aspects of the present invention made based on the above findings are as follows.
The first aspect of the present invention is a method for producing a cellular membrane comprising the steps of:
A method for analyzing at least one of metal particles and metal oxide particles during or after production by an electron microscope, comprising the steps of:
a mode selection step of selecting from a normal mode with high magnification and low resolution and a high-speed mode with low magnification and high resolution;
an analysis step of analyzing at least one of the metal particles and the metal oxide particles in the mode selected in the mode selection step;
This is an analytical method using an electron microscope,

A second aspect of the present invention is the invention according to the first aspect,
The magnification in the high speed mode is set to 0.5 times the magnification in the normal mode, and the resolution in the high speed mode is set to twice the resolution in the normal mode.

A third aspect of the present invention is the invention according to the first or second aspect,
In the mode selection step, a mode is selected depending on the number of analyses to be performed within a predetermined period.

A fourth aspect of the present invention is the invention according to any one of the first to third aspects,
The analysis step uses a scanning electron microscope.

The present invention allows appropriate analysis using an electron microscope regardless of the number of analyses to be performed within a given period of time.

The embodiment of the present invention is described below. In this specification, "~" refers to a value greater than or equal to a given value and less than or equal to a given value.

The present embodiment has the following configuration.
"A method for analyzing at least one of metal particles and metal oxide particles during or after production using an electron microscope,
a mode selection step of selecting from a normal mode with high magnification and low resolution and a high-speed mode with low magnification and high resolution;
an analysis step of analyzing at least one of the metal particles and the metal oxide particles in the mode selected in the mode selection step;
The present invention relates to an analysis method using an electron microscope.

Examples of the electron microscope used in this embodiment include SEM, TEM, and STEM. In this embodiment, the use of SEM is illustrated. SEM is suitable for observing the surface of at least one of metal particles and metal oxide particles. SEM is also preferable because it detects characteristic X-rays generated by electron beam irradiation and disperses them by energy, enabling EDS analysis for elemental analysis and composition analysis.

There are no limitations on the content of the analysis (so-called inspection content), but for example, foreign matter may be mixed into a manufactured product that is at least one of metal particles and metal oxide particles, and the manufactured product may be analyzed to detect this foreign matter. Note that this manufactured product includes not only the final product after manufacturing, but also materials during manufacturing, so-called intermediates.

As long as analysis using an electron microscope is possible, there are no limitations on the type or shape of at least one of the metal particles and metal oxide particles.

The above-mentioned foreign matter may be, for example, conductive particles (hereinafter also referred to as metallic foreign matter) that contain a metal different from at least one of the metal elements and metal oxide particles that are the product.

In other words, an example of the analysis would be to use an electron microscope to discover and analyze metallic foreign matter in a product that is at least one of metal particles and metal oxide particles.

The analysis of the metallic foreign matter may include, for example, qualitative and quantitative evaluation of the number, dimensions, etc. of the metallic foreign matter. In this case, the analysis method according to this embodiment is also a method for detecting metallic foreign matter contained in multiple particles.

In this embodiment, a mode selection process is performed to select from a normal mode with high magnification and low resolution and a high-speed mode with low magnification and high resolution depending on the production volume of at least one of the products, which are metal particles and metal oxide particles.

In this specification, "magnification" refers to the observation magnification when capturing a reflected electron image, and "resolution" refers to the resolution (unit: pixel) when capturing a reflected electron image. In addition, "high" and "low" in the above paragraph are relative values between normal mode and high-speed mode. There are no limitations on the absolute numerical values of magnification and resolution, whether in normal mode or high-speed mode.

"Normal mode" is a mode for normally analyzing at least one of the manufactured products, which are metal particles and metal oxide particles. On the other hand, in normal mode, it is preferable to set the magnification relatively high. For example, as shown in the examples below, it may be set to 50 times or more, and even better to set it to 100 times or more. In that case, the manufactured product can be analyzed at a higher magnification. Therefore, even if the resolution is relatively low (for example, even if the resolution is set to 512 pixels), it does not have much effect on the analytical accuracy.

On the other hand, the "high-speed mode" is, as the name suggests, a mode for analyzing at least one of the manufactured products, namely, metal particles and metal oxide particles, at high speed. In high-speed mode, the magnification is set lower than in normal mode, while the resolution is set higher than in normal mode.

In high-speed mode, there is no limit to the degree to which the magnification is reduced or the resolution is increased. However, preferably, a value n times (n is a natural number equal to or greater than 2) (more preferably 2 times) the resolution in normal mode is adopted as the resolution in high-speed mode. And, preferably, a value 0.4 to 0.6 times the magnification in normal mode (more preferably, the reciprocal of the value n multiplied by the resolution, for example 0.5 times) is adopted as the magnification in high-speed mode. In one example, in high-speed mode, the number of observation fields is reduced by lowering the magnification, making it possible to reduce the time required in normal mode by more than 50%.

In this embodiment, the above two modes are selected depending on the number of analyses required within a specified period (for example, the target production volume of at least one of metal particles and metal oxide particles). For example, the production volume of at least one of metal particles and metal oxide particles (target production volume within a specified period) may be divided into five stages beginning with the lowest production volume, with normal mode remaining in stages 1 to 3, and high-speed mode being selected in stages 4 and 5.

The mode selection may be performed manually by an operator, or may be automatically selected based on the production volume of at least one of the metal particles and metal oxide particles input into the system.

When the automatic selection method is adopted, an analysis system using an electron microscope may be constructed that includes an input unit for inputting the number of analyses (e.g., the production volume of at least one of simple metal particles and metal oxide particles) and a mode selection unit for selecting one of the above two modes depending on the number of analyses (e.g., the production volume of at least one of simple metal particles and metal oxide particles). This analysis system includes an analysis unit, which corresponds to an electron microscope (e.g., SEM).

When the automatic selection method is adopted, the technical idea of the present invention is also embodied in a program that causes a computer to function as an input unit for inputting the number of analyses (e.g., the production amount of at least one of metal particles and metal oxide particles), a mode selection unit for selecting one of the above two modes depending on the number of analyses (e.g., the production amount of at least one of metal particles and metal oxide particles), and an analysis unit.

In the analysis step of this embodiment, there are no limitations as long as at least one of metal particles and metal oxide particles can be analyzed in the mode selected in the mode selection step. As mentioned above, the surface of the metal foreign matter may be observed, or the metal foreign matter may be automatically detected from the captured image and at least one of the particle shape and dimensions may be automatically measured. In addition, EDX analysis using an energy dispersive X-ray spectrometer (EDS) may be performed on the automatically detected metal foreign matter. For this reason, it is preferable to use a SEM-EDX device in the analysis step.

There are no limitations on the device used in this case, and any known SEM or TEM device may be used. With this device, in high-speed mode, automatic detection of metallic foreign bodies from captured images can be performed appropriately, and the time required for high-speed mode can be reduced by more than 50% compared to the time required for normal mode.

In the analysis process, it is advisable to attach at least either metal particles or metal oxide particles to a conductive adhesive member, set the conductive adhesive member in the above-mentioned device, and perform the analysis. This makes it possible to perform the analysis without carrying out special pretreatment (metal vapor deposition, etc.) associated with SEM observation. There are no limitations on the shape or type of material of the conductive adhesive member, but an example is carbon tape.

According to this embodiment, it is possible to perform appropriate analysis using an electron microscope regardless of the number of analyses to be performed within a given period of time.

The technical scope of the present invention is not limited to the above-described embodiment, but includes various modifications and improvements within the scope of the specific effects that can be obtained by the constituent elements of the invention and their combinations.

For example, in this embodiment, an example was given in which the mode is selected according to the target production volume of at least one of the products, which are simple metal particles and metal oxide particles. However, in other cases, when there are a large number of analyses and this takes time, the high-speed mode may be selected in the above mode selection to save time.

In addition, although an example of the analysis content in this embodiment is to discover metallic foreign matter and analyze the metallic foreign matter, at least one of the manufactured products, the metal particles and the metal oxide particles, may be analyzed qualitatively and/or quantitatively. For example, the method according to this embodiment may be applied to at least one of the metal particles and the metal oxide particles embedded in resin. These examples are collectively referred to as "analyzing at least one of the metal particles and the metal oxide particles with an electron microscope."

The present invention may include switching between normal mode and high-speed mode (e.g., one switching (e.g., normal mode → high-speed mode), preferably two switchings (e.g., normal mode → high-speed mode → normal mode)). If this condition is met, for example, after two switchings, there is nothing to prevent SEM observation at half the magnification while maintaining the resolution specified in normal mode.

The following describes this embodiment. Note that the technical scope of the present invention is not limited to the following embodiment.

[Determine the magnification and resolution to be used in normal mode]
The magnification and resolution in normal mode are determined by the tests described below.

「画素サイズ」は、１画素（ｐｉｘｅｌ）あたりの実空間内の寸法である。
「検出粒子サイズ」は、自動検出の対象となる粒子の画像上での輝度の閾値である。この項目の値が２０の場合、輝度閾値以上のピクセル数が２０以上集まって存在する場合、この集まりを所定の金属異物として検出する。
「デュエルタイム」は、反射電子像を撮像する際の電子ビームの１スキャンに要する時間である。
「ＥＤＸ収集時間」は、ＥＤＸ分析時の積算時間である。
「測定時間」は、上記試験を終了するまでに要した時間である。 The time required to detect three particles of a metal having a size of 50 μm or more was investigated for a sample (metal oxide powder) containing a certain metal foreign matter. Specifically, the powder sample was attached to the adhesive surface of a carbon tape measuring 8 mm x 40 mm, and the carbon tape was set in a SEM-EDX device (FlexSEM1000 manufactured by Hitachi High-Tech Corporation, Aztec manufactured by Oxford Instruments for EDS, acceleration voltage: 20 kV) and detection was performed (hereinafter, the same method was adopted). The results are shown in Table 1 below.

"Pixel size" is the dimension of one pixel in real space.
"Detection particle size" is the brightness threshold on the image of particles to be automatically detected. If the value of this item is 20, when there are 20 or more pixels with brightness levels equal to or greater than the brightness threshold, the group is detected as a specified metallic foreign object.
"Dwell time" is the time required for one scan of the electron beam when capturing a reflected electron image.
"EDX collection time" is the integration time during EDX analysis.
"Measurement time" is the time required to complete the test.

Considering the results in Table 1, in this test, the magnification in normal mode was set to 100x and the resolution to 512 pixels. Accordingly, the magnification in high-speed mode was set to 50x and the resolution to 1024 pixels.

[Measurement time in high speed mode]
The measurement times in the high speed mode were obtained by the tests described below.

なお、実施例２は、実施例１での測定を同一試料にて再度行った試験である。 The time required to complete automatic detection of particles of the above-mentioned specified metals having a size of 20 μm or more was investigated for samples containing the metal particles, and the results are shown in Table 2 below.

In Example 2, the measurement in Example 1 was repeated on the same sample.

As shown in Table 2, in Comparative Example 1, the magnification was set to 0.5 times that of the normal mode, while the resolution was set to the same value as in the normal mode, but only one particle could be detected in the measurement time of 10 minutes. In Comparative Example 2, the detection particle size conditions were set to be loose, but only seven particles could be detected in the measurement time of 10 minutes.

On the other hand, in Examples 1 and 2, the measurement time was reduced by more than 50% compared to the measurement time required for the normal mode condition setting test. Moreover, even though the measurement time was just over 10 minutes, just under 40 metal foreign objects were detected.

This embodiment enabled speedy and appropriate analysis. This means that appropriate analysis can be performed using an electron microscope by switching modes depending on the number of analyses to be performed within a given period of time.

Claims (3)

A method for analyzing at least one of metal particles and metal oxide particles during or after production by an electron microscope, comprising the steps of:
a mode selection step of selecting from a normal mode having a predetermined magnification and a predetermined resolution and a high-speed mode having a lower magnification and a higher resolution than the normal mode ;
an analysis step of analyzing at least one of the metal particles and the metal oxide particles in the mode selected in the mode selection step;
having
In the mode selection step, the normal mode is selected when the number of analyses to be performed within a specified period is small, and the high-speed mode is selected when the number of analyses to be performed within a specified period is large . The method of analysis using an electron microscope according to claim 1, wherein the magnification in the high-speed mode is 0.5 times that in the normal mode, and the resolution in the high-speed mode is twice that in the normal mode. 3. The method for analysis by an electron microscope according to claim 1 , wherein a scanning electron microscope is used in the analyzing step.