KR101099139B1 - scintillator manufacturing method for scanning electron microscope - Google Patents

Abstract

A scintillator having a structure capable of increasing durability is provided. The scintillator includes a substrate, a visible light conversion layer formed on the substrate and converting the charged particles into visible light, and a graphene layer receiving the charged particles and transmitting the visible particles into the visible light conversion layer. .

Description

Scintillator manufacturing method for scanning electron microscope

The present invention relates to a detection apparatus, and more particularly, to an apparatus for detecting charged particles emitted from a specimen scanned by a scanning electron microscope or the like.

Scanning Electron Microscope (Scanning Electron Microscope) is a device for observing the shape and microstructure of the sample, the distribution of members, qualitative, quantitative analysis. Samples are mainly solid, powder and thin film samples of conductors such as metals, semiconductors such as ICs and oxides, insulating materials such as polymer materials and ceramics. Scanning electron microscopy uses a magnetic lens to narrow the electron beam and detect secondary electrons generated by scanning the electron beam on a sample surface. Since the amount of secondary electrons depends on the type of material on the surface and the curvature of the surface, a fine magnified image of the surface can be obtained. The scanning electron microscope includes a scintillator which collects charged particles emitted from the specimen and converts the collected charged particles into a visible light image.

Conventional scintillators usually consist of insulators, such as phosphorus based fluorescent materials. When charged particles collide with the insulator, the charged particles are charged up in the insulator, and the charged particles remain charged until the charged particles exit the insulator. When the insulator is charged to reach the saturation state, newly input charged particles and repulsive force are generated, so that the charged particles are no longer introduced into the scintillator, and thus do not obtain a desired image.

Therefore, a metal coating such as aluminum (Al) is usually applied to the scintillator. The metal coating serves to discharge the high voltage charged particles accumulated in the specimen through the specimen stage of the specimen holder and the grounded scanning electron microscope. However, when a metal coating such as aluminum is used for the scintillator, charged particles collide with the metal coating layer, causing cracks in the metal coating, and the metal coating layer is oxidized over time. Therefore, the discharge performance of the charged particles accumulated in the scintillator decreases. In addition, in the case of the scintillator included in the vacuum chamber of the scanning electron microscope, the vacuum chamber is opened to replace the scintillator, and in this case, the durable scintillator may be damaged because other components in the vacuum chamber may be damaged. Is required.

It provides a scintillator and a scintillator manufacturing method having a structure that can increase the durability.

Scintillator (Scintillator) according to one aspect, is formed on the substrate, a visible light conversion layer for converting the input charged particles into visible light, and graphene (graphene) for receiving the charged particles to pass through the visible light conversion layer Layer.

The scintillator further includes a ground terminal formed in the graphene layer and discharging the charged particles accumulated in the graphene layer to the outside.

According to another aspect, a scanning electron microscope including a scintillator displaying a structure of a specimen under test, wherein the scintillator is formed on a substrate, and the visible light converts the received secondary electrons into visible light. A conversion layer and a graphene layer that receives secondary electrons generated as charged particles collide with the specimen to be measured and transmits the secondary electrons to the visible light conversion layer.

According to another aspect of the present invention, a method of manufacturing a scintillator includes the steps of growing graphene on a substrate, etching the substrate to form a graphene thin film, and depositing the graphene thin film on a visible light conversion layer that converts charged particles into visible light. The step of placing in the presence of water.

The scintillator manufacturing method further includes forming a ground terminal for discharging charged particles that are incident and accumulated in the graphic thin film to the outside.

By using a scintillator having a graphene thin film coated on the visible light converting layer, the scintillator's durability can be increased, and a high sensitivity image showing the structure of the specimen can be obtained by increasing the transmittance of charged particles incident on the visible light converting layer. have.

1 is a diagram illustrating an example of a structure and operation of a scanning electron microscope.
FIG. 2 is a diagram illustrating an example of a structure of a detector and a PMT included in the scanning electron microscope of FIG. 1.
3 is a diagram illustrating an example of a structure of the scintillator of FIG. 2.
4 is a diagram illustrating an example of a scintillator manufacturing method.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that detailed descriptions of related well-known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be based on the contents throughout this specification.

1 is a diagram illustrating an example of a structure and operation of a scanning electron microscope.

The scanning electron microscope 100 includes a field emission tip 112, an anode 114, a focusing lens 116, 118, an aperture 120, a scanning coil 122, an objective lens 124. The detector 140 may include a photomultiplier 150.

The scanning electron microscope 100 scans the electron beam on the specimen 130 to provide information about the specimen 130. Components 112, 114, 116, 118, 120, 122, 124, 140 included in the scanning electron microscope 100 are included in the vacuum chamber 110. The reason for maintaining the vacuum is to prevent the charged particles emitted from the field emission tip 112 to collide with the molecules in the air until the specimen 130 is lost.

The electron beam 10 emerging from the field emission tip 112 is accelerated at the anode 114 to form a mono-chromatic electron beam that is focused by the focusing lenses 116, 118, which are electromagnetic lenses. The field emission tip 112 may be composed of a tungsten tip with a sharp tip. The configuration including the field emission tip 112 and the anode 114 may be referred to as an electron gun.

The focusing lenses 116 and 118 are cylindrical electromagnets in which coils are wound to collect charged particles in one place using a property of bending by an electromagnetic magnetic field. This electron beam forms a focal point on the specimen 130 through the objective lens 124. The electron beam 10 is scanned left and right and up and down using the scanning coil 122.

When the charged particles forming the electron beam 10 impinge on the surface of the specimen 130, secondary electrons are generated from the surface of the specimen 130. Since secondary electrons are emitted from the surface portion of the specimen 130, the secondary electrons provide information about the shape of the surface. Some of the electrons collided with the specimen 130 at high speed may be reflected or bounced off the surface. Back-scattered electrons are used for component analysis of the sample.

The detector 140 may include a scintillator and a light guide. A scintillator refers to a device (or material) that emits light when it is impacted by charged particles. When secondary electrons strike a fluorescently coated scintillator, the secondary electrons excite the fluorescent material and emit light, which travels along a light guide, which may be composed of lucite or quartz. do. The detailed configuration of the detector 140 will be described later with reference to FIG. 2.

The photomultiplier 150 (hereinafter referred to as PMT) converts the light reached along the detector 140 into electrical pulses. Although not shown, the output voltage of the PMT 150 may be amplified and converted into a digital signal, and image processing may be performed to provide an image of the scan area of the specimen 130. Since the secondary electrons eventually pass through a medium called an optoelectronic device, the secondary electrons appear brighter when the emission amount is large and darker when the secondary electrons are large, and thus an image of the contrast of the specimen 130 may be obtained.

Although not shown in FIG. 1, the scanning electron microscope 100 may further include various electronic circuits and components, such as a circuit for controlling a vacuum, a scanning circuit, and an image signal processing circuit.

FIG. 2 is a diagram illustrating an example of structures of the detector 140 and the PMT 150 included in the scanning electron microscope of FIG. 1.

Referring to FIG. 2, the detector 140 of FIG. 1 may include a collector 142, a grounding jig 143, a scintillator 144, and a light guide 146.

Secondary electrons generated in the specimen 130 are focused at a high pressure of the collector 142, input to the scintillator 144, and converted into light. The collector 142 may have a network structure. The grounding jig 143 fixes the collector 142 to the scintillator 144.

In order to prevent the charged particles from penetrating deeply into the specimen 130 so that a large number of secondary electrons are discharged, as shown in FIG. 2, the specimen 130 is not obliquely formed at an angle of 90 degrees with the incident electron beam. Can be arranged. The scintillator 144 receives the generated secondary electrons and converts the received secondary electrons into visible light. The visible light converted by the scintillator 144 impacts the photocathod 145 positioned at the end of the PMT 150.

Since the photocathode 145 is coated with a material that emits electrons when light collides, photoelectrons from the light enter the PMT 140, and the PMT 140 increases the number of photoelectrons proportionally. Converts photoelectrons to voltage. The weak voltage generated by the PMT 150 may be amplified by the preamp 155 and further amplified by an amplifier (not shown). In this case, the obtained electrical signal (analog signal) may be converted into a digital signal and then subjected to image processing.

According to one embodiment, scintillator 144 uses graphene instead of metal coating. Graphene refers to a two-dimensional carbon allotrope made by carbon atoms forming a honeycomb lattice structure. Graphene exhibits conductivity and exhibits anisotropy along the geometric direction in conduction.

The scintillator 144 is included in a scanning electron microscope for scanning the electron beam radiated from the electron gun to the specimen to be measured 130 to display a structure for the specimen to be measured. Although the description has been made with respect to an example of receiving secondary electrons generated from the surface of the specimen 130 as charged particles and converting them into visible light, the present invention is not limited thereto and may be variously modified.

3 is a diagram illustrating an example of a structure of the scintillator 144 of FIG. 2.

Referring to FIG. 3, the scintillator 144 may include a substrate 300, a visible light conversion layer 310, a graphene layer 320 disposed on the visible light conversion layer 310, and a ground terminal 330.

The substrate 300 may be a glass substrate.

The visible light conversion layer 310 is composed of the phosphor-based fluorescent material described above converts the incident charged particles into visible light. The visible light converting layer 310 may generate visible light for secondary electrons generated by colliding with charged particles incident on the specimen to be measured 130 as illustrated in FIGS. 1 and 2.

The graphene layer 320 is composed of a graphene thin film. The graphene layer 320 is grounded and configured to discharge charged particles accumulated in the visible light conversion layer 310. To this end, a ground terminal 330 is formed on the graphene layer 320 to discharge charged particles accumulated in the graphene layer 320 to the outside. The ground terminal 330 may be formed of a metal electrode.

By using the scintillator 144 having a structure in which the graphene layer 320 is coated on the visible light conversion layer 310, the durability of the scintillator 144 may be increased. In addition, since the graphene layer 320 has a network structure, transmittance of the charged particles to the visible light conversion layer 310 may be increased as compared with the conventional metal coating layer. Therefore, by using the scintillator 144 structure to increase the transmittance of the charged particles incident on the visible light conversion layer 310, it is possible to obtain a high-sensitivity image representing the structure of the specimen 130.

4 is a diagram illustrating an example of a scintillator manufacturing method.

Graphene is grown (410) on a substrate that can be removed by etching, such as a glass substrate. Graphene may be grown on a substrate by a method such as chemical vapor deposition (CVD).

The substrate is etched to form a graphene thin film (420). In addition, in order to manufacture a scintillator, a visible light conversion layer is formed on a support substrate. The visible light converting layer may be formed by applying a solution including a phosphorescent component of a phosphorescent component on a support substrate and discharging water from a solution containing a phosphorous component of a phosphorous component. Since the method of forming a visible light conversion layer is well-known, detailed description is abbreviate | omitted.

The visible light conversion layer formed on the support substrate is coated with a film stabilizer, for example, collodion (430). The collodion coating may be performed by dropping a collodion solution on the visible light conversion layer by about one drop and then releasing moisture. Since the visible light conversion layer is unevenly formed, adding a film stabilizer such as collodion to the visible light conversion layer may fill a gap that may be formed in the visible light conversion layer. Therefore, it is possible to prevent the sensitivity of the image from being lowered by the gap formed on the surface of the visible light conversion layer.

The graphene thin film formed in step 420 is placed on the visible light conversion layer in the presence of moisture (440). Then, as the moisture evaporates, the graphene thin film is adhered to the visible light conversion layer, and as shown in FIG. 3, the visible light conversion layer 310 and the graphene layer 320 may be formed on the substrate 300. Then, the ground terminal 330 for discharging charged particles that are incident and accumulated in the graphene layer 320 may be formed (450).

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be construed to include various embodiments within the scope of the claims.

Claims (5)

As a scintillator for electron microscopy,
Board;
A visible light conversion layer formed on the substrate and converting input charged particles into visible light; And
A scintillator comprising a graphene layer that receives charged particles and transmits them to the visible light conversion layer. The method of claim 1,
The scintillator is formed on the graphene layer, and further comprising a ground terminal for discharging the charged particles accumulated in the graphene layer to the outside. A scanning electron microscope comprising a scintillator displaying the structure of a specimen under test,
The scintillator is,
Board;
A visible light conversion layer formed on the substrate and converting input secondary electrons into visible light; And
And a graphene layer that receives secondary electrons generated when the charged particles collide with the specimen to be transmitted and transmits them to the visible light conversion layer. As a method for producing a scintillator for an electron microscope,
Growing graphene on the substrate;
Etching the substrate to form a graphene thin film; And
And placing the graphene thin film on a visible light conversion layer for converting charged particles into visible light in a moist state. The method of claim 4, wherein
And forming a ground terminal for discharging charged particles that are incident and accumulated in the graphene thin film to the outside.

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