JPH09264823A - Sample holding substrate and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sample holding substrate suitable for observing a munite sample and capable of obtaining a sharp image by pressing a sample to a metal thin film to fix the same and holding the sample wirhout embedding the same in an adhesive. SOLUTION: As a material of a substrate 6, any one capable of holding the mechanical strength of a sample holding substrate 2, for example, a conductive material such as metal, an insulating material such as glass or a flexible material like a resign can be used. A metal thin film 12 is formed on the surface to which a minute sample 4 is bonded of the sample holding substrate 2. The metal thin film 12 forms a cavity having a shape almost the same to that of the sample by pressing the sample 4 and the sample 4 is held to this cavity. As a material of the metal thin film 2, indium, gold, silver, lead, tin, aluminum, copper, platinum, palladium or an alloy material of them can be used. An intermediate layer 10 can be formed by using an adhesive, for example, an acrylic, chloroprene rubber type or polyvinyl acetate type adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample holding substrate for holding a sample when observing a sample such as various kinds of minute powders, and a sample holding method for the sample holding substrate.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing a method of observing fine powder by an electron microscope. As shown in the figure, when observing the fine powder with an electron microscope or the like, after the sample 4 is held on the sample holding substrate 2, the sample and its vicinity are scanned with an electron beam in the flow shown by the arrow in the figure. While irradiating, secondary electrons excited as a result are detected, and the shape of the powder sample is obtained by the change.

When observing a sample with an electron microscope, if the sample moves while scanning the electron beam, the obtained image becomes discontinuous and distorted, and a clear image cannot be obtained. Therefore, when observing a small sample that is easy to move such as a powder sample, it is necessary to hold the sample on the sample holding substrate in advance.

FIG. 3 is a diagram showing a conventional sample holding method. Conventionally, in order to hold a sample on the sample holding substrate 2,
Using a base 6 made of copper foil, and an adhesive tape obtained by applying an adhesive layer 8 in which fine copper particles are dispersed in an adhesive such as an acrylic adhesive on the base, the powder sample 4 is scattered on the adhesive layer 8. Further, the powder sample 4 was pressed to adhere the sample to the adhesive layer. However, when the powder sample is directly adhered to the surface of the adhesive layer and a finer powder sample is observed, there arises a problem that the image is distorted and a clear image cannot be obtained.

[0005]

As described above, when a conventional sample holding substrate is used and an attempt is made to observe a finer sample at a high magnification, there arises a problem that a clear image cannot be obtained. The present invention has been made in view of such a problem, and is suitable for observing a micro sample using an electron microscope,
An object of the present invention is to provide a sample holding substrate capable of obtaining a clear image.

[0006]

The first invention of the present application is a sample holding substrate having a substrate and a metal thin film having a thickness of 5 nm or more and a surface roughness of 10 μm (Rmax) formed on the substrate surface. A second invention of the present application is the sample holding substrate according to the first invention, wherein the metal thin film is made of a metal material having a Mohs hardness of 4 or less, a Brinell hardness of 30 or less, or a Vickers hardness of 40 or less.

A third invention of the present application is the sample holding substrate according to the first invention of the present application, wherein the metal thin film is formed on the surface of the substrate through an adhesive layer having a viscosity of 2000 (poise / 20 ° C.) or more. is there.

A fourth invention of the present application is a substrate, a thickness of 10 nm or more formed on the surface of the substrate, and a surface roughness of 10 μm (R
max), a step of spraying a sample on the surface of a sample holding substrate having a metal thin film having a Mohs hardness of 3 or less, a step of dropping a dispersion medium on the surface of the sample holding substrate, and a step of applying the dispersion medium so that the sample is dispersed. It is a sample holding method for a sample holding substrate, which comprises a step of stirring and a step of pressing the sample against the sample holding substrate after drying the dispersion medium.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has noticed that an image obtained is distorted when the shape of a micro sample is observed at a high magnification using an electron microscope using a conventional sample holding substrate. The present inventor has conducted extensive research to elucidate the cause, and has found that there is a problem in the adhesive layer formed on the surface of the sample holding substrate, resulting in the present invention.

An adhesive layer is formed on the surface of the conventional sample holding substrate, and the solvent component remaining on the adhesive layer is volatilized by irradiation with an electron beam. As a result, the adhesive layer contracts in the electron beam irradiation portion, and the sample slightly moves toward the electron beam irradiation portion. Therefore, it is assumed that the image of the vertical component and the scanning direction of the electron beam are not smoothly connected, and a clear image cannot be obtained.

The gist of the present invention is to form a surface layer without shrinkage on the sample holding substrate by forming a material having low volatility on the surface of the sample holding substrate. FIG. 1 is a schematic sectional view of a sample holding substrate of the present invention holding a sample.

The present invention will be described below with reference to the drawings. The substrate 6 according to the present invention can be used without particular limitation as long as it can maintain the mechanical strength of the sample holding substrate 2,
A conductive material such as metal, an insulating material such as glass, or a flexible material such as resin can be used.

For example, a plate-like or film-like material having a thickness of about 1 μm to 1 mm and made of copper, aluminum or polyimide can be used. Further, since it is necessary to smooth the surface of the metal thin film described later,
It is preferable to use a smooth surface for the sample holding side of the substrate 6, and it is desirable to use a substrate having a smoothness of 20 μm (Rmax) or less.

If the metal thin film 12 described later is thin,
Alternatively, when a metal thin film is formed without interposing the intermediate layer 10, a substrate having a hardness of 3 or less on the Mohs hardness, 20 or less on the Brinell hardness, or 30 or less on the Vickers hardness in order to form a sufficient depression in the metal thin film 12. Preference is given to using materials.

The metal thin film 12 according to the present invention is formed on the side of the surface of the sample holding substrate 2 to which the use is attached, and is for holding the sample instead of the conventional adhesive layer. The metal thin film 12 forms a recess having substantially the same shape as the sample shape by pressing the minute sample 4, and holds the sample in this recess.
If the hardness of the metal thin film 12 is high, or if the distance between the metal thin film 12 and the substrate 6 is extremely narrow with respect to the sample particle size, a dent having a size large enough to hold the sample is not formed or the sample is destroyed. The thickness needs to be 5 nm or more. Furthermore, the hardness is 3 or less Mohs hardness, 30 or less Brinell hardness,
Alternatively, it is preferable to use a base material having a Vickers hardness of 40 or less.

Further, the surface of the metal thin film 12 has a surface roughness of 1.
It should be 0 μm (Rmax) or less. When observing a sample with an electron microscope or the like, the sample is irradiated with an electron beam focused into a beam, but the surface roughness of the sample holding substrate 2 is 1
This is because if the thickness exceeds 0 μm, the sample may be placed at a position deviated from the focus of the electron beam, and a clear image cannot be obtained.

The reason for using metal as the thin film material is that the sample holding substrate 2 needs to be electrically conductive. When an insulator is used as the sample holding substrate, the sample surface is charged when the sample and the sample holding substrate are irradiated with an electron beam (charge-up phenomenon). When the sample holding substrate surface 2 is charged, the charged electric charges and the electron beam repel each other, and the electron beam cannot be irradiated to a desired position. In the present invention, the charge-up phenomenon can be suppressed by forming the surface of the sample holding substrate 2 with a conductive material.

As the material of the metal thin film 12 as described above, indium, gold, silver, lead, tin, aluminum, copper,
Platinum, palladium or alloy materials of these can be used,
For example, the film may be formed by a known thin film technique such as a sputtering method or a vapor deposition method.

The metal thin film 12 may be directly formed on the surface of the substrate, but is 10 nm or more, 2000 (p
It is desirable to form the intermediate layer 10 having a viscosity of (oise / 20 ° C.) or higher.

When the powder sample 4 is made of a material having a low hardness, the sample may be destroyed by the hardness of the metal thin film 12. In such a case, the metal thin film is thin, for example, a metal thin film having a thickness of 100 nm or less, preferably 50 nm or less, and a thickness of 10 nm or more, preferably 100 nm.
By forming the intermediate layer 10 having a thickness of not less than 10 nm, it becomes possible to make the depression more likely to occur. Also in this case, the thickness of the metal thin film 12 needs to be 5 nm or more.
This is because when the thickness of the metal thin film 12 is less than 5 nm, the solvent component contained in the adhesive layer vaporizes from the grain boundaries of the metal thin film 12 and shrinks.

For the intermediate layer 10, for example, an acrylic type adhesive, a chloroprene rubber type adhesive, a polyurethane type adhesive or a polyvinyl acetate type adhesive can be used. The simplest way to create such a sample-holding substrate is to use a commercially available double-sided tape for an electrophotographic microscope, use the double-sided tape film itself as the substrate, and use the adhesive layer as the intermediate layer. A metal thin film may be formed.

The sample holding substrate of the present invention further has the following advantages. The thickness of the conventional sample holding substrate that directly attaches the sample to the adhesive layer is several tens of nm in order to form an adhesive layer with a uniform thickness because it is difficult to control the thickness of the adhesive layer. Becomes When observing a sample using such a conventional sample measurement substrate, the sample is miniaturized, and if an attempt is made to measure a sample having a particle size of 10 nm or less, the sample is buried in the adhesive layer and the sample is measured. You may not be able to.

On the other hand, since the sample holding substrate of the present invention fixes the sample by pressing the sample on the solid metal thin film, the sample can be held without being buried in the adhesive. Become.

Further, by placing the sample on the surface of the sample holding substrate together with a liquid dispersion medium such as water or alcohol and stirring the liquid, the powder sample can be placed on the surface of the sample holding substrate in a dispersed state. It will be possible. When the sample is directly attached to the adhesive layer as in the conventional case, the adhesive force of the adhesive layer may be reduced and the sample holding force may be lost by contact with water or alcohol. On the other hand, in the sample holding substrate of the present invention, the metal thin film is formed on the surface, and the sample is held by the recess formed in the metal thin film. Therefore, the sample holding ability is affected by the liquid such as water or alcohol. Never receive.

In order to hold the sample on the sample holding substrate, the sample is placed on the surface of the sample holding substrate in a dispersed state, and then the sample is pressed against the sample holding substrate with a force not to collapse the sample. Usually, an intermediate medium having low adhesiveness such as a medicine packing paper or a mouth paper is placed on the sample, and the intermediate medium is lightly pressed with a finger. It varies depending on the shape of the sample, the presence or absence of the adhesive layer, the material and the thickness of the metal thin film, but it is usually 30 to 300 g.
Press with a force of about / cm ² . By doing this,
When the metal thin film is recessed, the sample bites into the metal thin film, and the sample is held on the sample holding substrate.

[0026]

【Example】

Example 1 Preparation of Sample Holding Substrate As a substrate and an adhesive layer, thickness 200 μm, width 0.5 c
m, 1.0 cm long conductive tape (Nisshin EM, conductive carbon double-sided tape for SEM) was used to sputter coat one side of the adhesive layer with a gold thin film to a thickness of 1 μm. A sample holding substrate having a surface roughness of 5 μm (Rmax) was prepared.

Holding of Sample As a powder sample, a fine iron oxide powder sample having a particle size of 1 μm or less was used, 0.2 g of this powder sample was scattered on the surface of the sample holding substrate, and then ethyl was placed on the sample on the sample holding substrate. 1 g of alcohol was added dropwise and stirred.

The sample holding substrate was left to stand until the ethyl alcohol was evaporated, dried, and then the medicine packing paper was placed on the sample holding substrate and pressed with a force of about 100 g / cm. It was confirmed that the sample did not move even when the sample holding substrate was tilted at 45 °, and the sample was fixed and held.

Observation of Sample with Electron Microscope A sample holding substrate on which a sample is fixed and held is mounted on a sample stand for a scanning electron microscope, placed in an electron microscope apparatus (FESEM, Hitachi S-900), and accelerated. An image was output after observing on a monitor at a voltage of 5 kV and 50,000 times.

Example 2 A substrate having a thickness of 15 μm, a width of 0.5 cm and a length of 1.0
cm aluminum foil, an adhesive (Sony Bond T-4000: manufactured by Sony Chemical Co., Ltd.) was applied as an intermediate layer on the aluminum foil so as to have a film thickness of 10 μm, and platinum having a film thickness of 1 μm was further applied on the intermediate layer. The layer was deposited by sputtering. After that, the sample was held and observed in the same manner as in Example 1.

Comparative Example Next, the sample was directly sprinkled on the adhesive layer of the conductive tape used in Example 1 and adhered to fix it to the sample holding substrate.
Held.

Thereafter, the sample was observed with an electron microscope in the same manner as when the sample holding substrate of the present invention was used. In the observation using the sample holding substrate of the present invention (Examples 1 and 2), a clear image of powder could be obtained.

In the observation using the sample holding substrate of the comparative example, there were many parts where the samples were overlapped with each other and the focus was deviated, and it took a lot of time to find the part where the samples were dispersed. Also, an image was output for the dispersed portion of the sample of the comparative example, but the shape was discontinuous at the bottom of the image.

From this fact, in the comparative example, the sample on the sample holding substrate moved during the scanning of the electron microscope, but in the present example, the movement was not confirmed, and the sample was securely fixed and held. I was able to confirm that it is being done in.

[0035]

According to the present invention, it is possible to provide a sample holding substrate suitable for observing a minute sample using an electron microscope and capable of obtaining a clear image.

[Brief description of drawings]

FIG. 1 is a diagram showing how a sample is held when a sample holding substrate of the present invention is used.

FIG. 2 is a diagram showing a scanning method of an electron microscope.

FIG. 3 is a diagram showing how a sample is held when a conventional sample holding substrate is used.

[Explanation of symbols]

 2 ... Sample holding substrate 4 ... Sample 6 ... Substrate 8 ... Adhesive layer 10 ... Intermediate layer 12 ... Metal thin film

Claims (4)

[Claims] 1. A sample holding substrate comprising a substrate and a metal thin film having a thickness of 5 nm or more and a surface roughness of 10 μm (Rmax) formed on the surface of the substrate. 2. The sample holding substrate according to claim 1, wherein the metal thin film is made of a metal material having a Mohs hardness of 4 or less, a Brinell hardness of 30 or less, or a Vickers hardness of 40 or less. 3. The thin metal film comprises 2000 (poise)
The sample holding substrate according to claim 1, wherein the sample holding substrate is formed on the surface of the substrate through an intermediate layer having a viscosity of / 20 ° C or higher. 4. A step of spraying a sample on the surface of a sample holding substrate having a substrate, a thickness of 10 nm or more, a surface roughness of 10 μm (Rmax) and a metal thin film formed on the surface of the substrate, and the surface of the sample holding substrate. And a step of stirring the dispersion medium so that the sample is dispersed, and a step of pressing the sample onto the sample holding substrate after the dispersion medium is dried. Holding method for the sample holding substrate.