JPH02155157A - Scintillator and manufacture of its light shielding membrane - Google Patents

Abstract

PURPOSE:To make it possible to take in a secondary electron image under a visible light by using a scintillator which has a light shielding membrane, and a backing membrane consisting of a light permeable high polymer closely attached to the light shielding membrane, at the upper side of a phosphor layer. CONSTITUTION:Electron beams 52 are radiated on a sample 53, and the secondary electrons 52 released from the sample 53 are detected. A scintillator 11 or 55 to be a secondary electron detector of a scanning type electron microscope, an electron beam tester, or the like, has a light shielding membrane 4 which consists of C, or a metal or an alloy of Be, Al, and the like, and a backing membrane 5 closely attached to the light shielding membrane 4, which consists of a light permeable high polymer, on the upper side of a phosphor layer 3. That is, since the membrane 4 for light shielding purpose which is smooth with almost no pinhole is formed on the surface, the external light never invades in a light guide 58 even though the secondary electron image is taken in in a bright condition. Consequently, a good secondary electron observation image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a scintillator used in a secondary electron detector such as a scanning electron microscope, and particularly to a method for manufacturing a light shielding film thereof.

2. Description of the Related Art An example of a conventional secondary electron detector such as a scanning electron microscope or an electron beam tester is shown in FIG. FIG. 5 shows an enlarged cross-sectional view of the scintillator portion at the tip, and FIG. 6 shows a further enlarged cross-sectional view of the phosphor layer. An electron beam 52 emerging from an electron optical system 51 is irradiated onto a sample 53, and secondary electrons 54 are emitted from the sample. The secondary electrons 54 are accelerated toward a scintillator 55 to which a positive DC bias potential of about 10 kV is applied, and then captured.

That is, the secondary electrons 54 pass through the metal back 56 and enter the phosphor layer 57, stimulating it. The phosphor layer 57 emits fluorescence. This fluorescence passes through a light guide 58 and enters a photomultiplier tube 59 . In the photomultiplier tube 69, due to the external charging effect, the incident light signal is converted into electrons again, amplified, and sent as an electric signal to a subsequent amplifier.

The above is the mechanism of secondary electron detection. Usually, the photoelectric conversion unit consisting of the metal back 56, the phosphor layer 57, etc. is called a scintillator (55), and the scintillator 55 that amplifies and converts the secondary electron signal into an electric signal to the photomultiplier tube 59 is collectively called 2. It is called a secondary electron detector (60). Note that 61 is a corona ring and 62 is a cap.

In recent years, scanning electron microscopes have been applied to develop TF for LCD TVs.
There have been attempts to detect defective pixels in T-arrays (for example, Japanese Patent Laid-Open No. 83-48473). This captures the potential difference between a defective pixel and a normal pixel as a contrast difference between secondary electron images. With this device, there is no need to assemble it into a liquid crystal panel, but at the TFT array stage.
Many defective pixels caused by TFT arrays can now be detected. However, there are some defective pixels in an actual liquid crystal panel that cannot be detected when the TFT array is observed using the above-mentioned apparatus.

This is because the actual driving state and the driving state of the device described above are not completely equal. One reason for this is that in actual driving conditions, defective pixels may be induced by leakage light from a backlight or the like that enters the transistor portion of the TFT.

On the other hand, in the conventional secondary electron detector using a scintillator as described above, even if an attempt is made to capture a secondary electron image in bright conditions, the metal back 56 transmits the light, so the photomultiplier tube 59 does not receive the light. It was impossible to observe the image because it appeared on the displayed image as a background. This means that the metal back 56 used in conventional scintillators is usually made by depositing several hundred aluminum layers on the phosphor layer 57, and as shown in FIG. This is because there are countless pinholes and cracks through which light enters. Therefore, in the past, it was not even possible to know whether or not there was a photo-induced defective pixel, so to speak.

In addition to the above examples, SEM with the sample irradiated with light
Even if you want to observe images or SEM images of the light-emitting body itself, it is difficult to do so using conventional scintillators.

Problems to be Solved by the Invention An object of the present invention is to provide a light shielding film for a scintillator that can capture a secondary electron image under visible light.

Means for Solving the Problems The scintillator of the present invention has a light-shielding film made of a thin film of C, Be, Al, or other metal or alloy, and a light-transmitting polymer in close contact with the light-shielding film, on the top of the phosphor layer. It is characterized by retaining a backing film consisting of.

As a method for producing a light shielding film having a lining film, a base layer that is soluble in a solvent is smoothly formed on a substrate, a lining film that is insoluble in the solvent is formed on the surface of the base layer, and a light shielding film is formed on the surface of the backing film. A thin film for the shielding film is formed, and then the thin film for the light shielding film is peeled off together with the backing film by immersing it in the solvent to dissolve and remove the underlayer.

Function The scintillator of the present invention has a thin light-shielding film on its surface that is smooth and has almost no pinholes, so even when capturing a secondary electron image in bright conditions, external light no longer enters the light guide. No intrusion occurs, no background appears in the displayed image, and a good observation image can be obtained. Furthermore, since the thin film of the light shielding film has a backing film, the strength is increased and the yield rate during scintillator manufacturing is improved.

Embodiment FIG. 1 is a sectional view showing an embodiment of the scintillator of the present invention. Cylindrical light guide tip 1 with a diameter of 10 mm
A transparent conductive film 2 is formed on the surface of the phosphor layer 3.
is formed. In this embodiment, a light shielding film 4 made of Al having a thickness of 500 mm and a backing film 5 having a thickness of 200 mm are formed in close contact with the upper part of the phosphor layer 3.

The secondary electrons incident from above pass through the light shielding film 4 and the lining film 5, enter the phosphor layer 3, and stimulate it.

The phosphor layer 3 emits fluorescence. This fluorescence enters the photomultiplier tube 59 from the light guide tip 1 through the light guide below it.

The light guide tip 1 is made of glass, and both end faces and side surfaces are polished and smooth to improve light transmission efficiency. This may be an acrylic resin or the like, depending on the case. The transparent conductive film 2 thereon is provided to prevent charge-up of the phosphor layer 3. This is also indium-
It is desirable to use a material having a high light transmittance for fluorescence from the phosphor layer 3, such as tin oxide (hereinafter abbreviated as ``TO'').

In this example, an ITO vapor-deposited film having a thickness of approximately 200 to 400 mm was used. Area resistance is 1Ω/mouth, wavelength 400
The visible light transmittance from n to 700 r+m was 90%.

P47 was used as the phosphor powder for the phosphor layer 3. The phosphor layer 3 was formed to a thickness of about 10 to 20 μm by a normal precipitation method using Improper Tool as a dispersant.

In this embodiment, Al was used as the light-shielding film material of the scintillator of the present invention, but other materials may be used as long as they have light-shielding properties, appropriate conductivity, and high electron transmittance. for example,
A thin film made of a light metal element such as Be or an alloy thereof, or a thin film made of C or another metal element has the same effect.

The backing film 5 may be made of acrylic resin, polyimide, or gelatin (polymer l with an average molecular weight of 110,000 or more).
Interspersed polymeric thin films can be used. Backing film 5
The necessary conditions for this are that the light shielding film 4 should not be dissolved in a solvent during lift-off, and that the light shielding film 4 should have adhesive properties.

Next, a method for manufacturing the Al light shielding film 4 and the backing film 5 will be explained based on FIG. 2. First, on a glass substrate 6 (20 mm x 20++ m), a gelatin aqueous solution was applied to a gelatin RX12. A smooth gelatin film 7 with an average molecular weight of 40,000 Å and a thickness of about 2000 Å was formed using a spin cord. Spin code polyimide resin (Toshi Semico Fine 5P810) on this surface to a film thickness of 200.
A backing film 5 was prepared.

An Al film 8 was deposited on top of this. The deposited Al film 8 was immersed together with the glass substrate θ in hot water at 40° C. and lifted off.

Gelatin (average molecular weight 40,000) is easily dissolved in water at room temperature. As a result, water gradually penetrated into the gelatin layer from the edges, and the Al film forming the lining film was peeled off in 10 to 15 minutes. The Al film showed the property of floating on the water surface and becoming taut. This is thought to be due to the effect of a very small amount of oil remaining on the membrane surface. Note that the water temperature may be room temperature, but the gelatin will dissolve faster if the water temperature is slightly higher. However, when the water temperature exceeds 60°C, the Al film becomes transparent. This is considered to be because the Al film was oxidized. In order to prevent the film from turning over and breaking during peeling, the depth of water on the substrate surface is preferably about 5 mm. Furthermore, if 1 to 2 drops of an aqueous ethanol solution diluted to 50% or less is dropped on the surface of the film floating on the water surface, wrinkles can be smoothed out by the diffusing power of ethanol.

Next, as shown in Fig. 2 (g), the Al film stretched on the water surface, with the phosphor layer 3 formed on the tip 1 of the light guide, is scooped up from below, and the phosphor layer 3 is removed. An Al film 8 was placed on the body layer 3. At that time, be careful not to leave any wrinkles as much as possible. If there are wrinkles, moisture will remain there, and when the pressure is reduced, it will evaporate and break the membrane. In the method of this embodiment, a small amount of residual moisture may evaporate and create small holes in the membrane, but as will be described later, there is no problem in practice. In addition, we also attempted to stack two A1 films by drying the moisture in the air and repeating the process shown in FIG. 2 for another film. The purpose of this is to almost eliminate pinholes by overlapping them. Through the above operations, the light shielding film 4 with almost no pinholes could be formed using either method.

The scintillator 11 prepared as described above is set on the upper end of the light guide 58 using the corona ring 61. The gap between the side edge of the corona ring 61 and the periphery of the light shielding film 4 is filled with Ag paste. This is due to two reasons: preventing discharge and shielding the peripheral area from light. After the assembly is completed, apply a -degree vacuum and confirm that the gas remaining between the layers does not expand and break the A1 membrane.

Note that the side surface of the light guide 58 was shielded from light with black acrylic paint.

The performance of this scintillator was evaluated by trying it on the secondary electron detector of the defective pixel inspection device described above. As a result, the optimum thickness of the Al light shielding film was 400A to 100OA in total, regardless of whether it was monochrome or multilayered.

At the above film thickness, the pinholes in the film are from a single layer;
It was confirmed that if there were 3 to 5 pieces and two layers, the number would be 0 to 1 piece. Regarding light shielding properties, in the aforementioned defective pixel inspection system, no background appears in the image even when the sample surface illuminance is 20,001 ux, and in terms of sensitivity, the potential resolution is exactly the same as that of the conventional example, and the S/H We were able to obtain a good secondary electron image. The bias potential of a scintillator in a normal scanning electron microscope, such as the above-mentioned defective pixel inspection device, is about 10 kV, so when the film thickness exceeds 1500 A, the transmittance of secondary electrons decreases, resulting in a decrease in sensitivity.

In addition, in this example, when peeling the Al film, gelatin was used as the base layer film and water was used as the solvent. Combinations such as organic solvents and polyvinyl alcohol-water may also be used. When an organic solvent is used for lift-off, the backing film may be gelatin or polyvinyl alcohol that is insoluble in the organic solvent, and when water is used, the backing film may be polyimide or polyvinyl chloride that is insoluble in water. Furthermore, when controlling the lift-off conditions, it is also possible to utilize the difference in solubility of the interlayer film and the backing film in the solvent. For example, a low molecular weight gelatin is used as the interlayer film, a high molecular weight gelatin is used as the backing film, and water is used as the solvent.

Next, another embodiment of the present invention is shown in FIG. In this example, the light shielding film 4 having the backing film 5 is not brought into close contact with the phosphor layer 3 as in the previous example, but is kept with a space between it and the phosphor layer 3 as shown in the figure. Deploy. Here, for reinforcement, a mesh 12 was provided inside the cylinder of the corona ring 13, and this was used as a support for the light shielding film 4 having the backing film 5. The mesh 12 has a pitch of 0.5 to 3 mm 1
A mesh having a diameter of 20 to 00 μm was used. The manufacturing method used was the same as in the example of the manufacturing method described above. During depressurization, the space between the light shielding film 4 and the phosphor layer 3 is made to have the same atmospheric pressure as the outside through the exhaust hole 14 so that the light shielding film 4 is not torn due to the pressure difference. In the present invention, the optical m film 4
has a backing membrane 5. When the lining M5 was not provided, the light shielding film 4 was often damaged when placed on the mesh, but by adding the lining film 5, the mesh 12
It is now less likely to be damaged when placed on. Even if the scintillator of this example is used, as in the previous example, no background appears in the image even when the sample surface illuminance is 20001 ux in the defective pixel inspection apparatus described above, and the sensitivity is also completely different from that of the conventional example. Secondary electron images with equivalent potential resolution and good S/N ratio could be obtained.

A TFT array for a liquid crystal television was observed using the aforementioned defective pixel inspection apparatus equipped with the scintillator of the present invention. Although it is a defective pixel in an actual liquid crystal panel, when observing the TFT array with the above device, in a dark state,
Some of the defective pixels that cannot be detected emit visible white light to T
It was discovered that when observed while irradiating an FT array, it appears as a defective pixel. This is considered to be because, for some reason, only the transistor of the relevant pixel exhibited greater photoconduction than that of the normal pixel, and the charges accumulated in the pixel electrode were discharged. As described above, the present invention has revealed the existence of photo-induced defective pixels for the first time. By observing the secondary electron image while irradiated with light, the detection ability of the defective pixel inspection apparatus described above can be improved.

Effects of the Invention By realizing the light-shielding scintillator of the present invention, it is possible to capture a secondary electron image under visible light.

TF makes it possible to capture secondary electron images under visible light.
The existence of photo-induced defective pixels in the T-array was revealed.

This can provide new guidelines for failure analysis of TPT transistors.

This also means that in many cases other than the above, SEM image observation with the sample irradiated with light or SEM image observation of the light emitting body itself is possible using the scintillator of the present invention.
It means the first time that this was possible. In other words, new possibilities for electron beam testing have been expanded, and the present invention has great significance, especially in terms of its application to material analysis, operation analysis of electronic devices, etc.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of one embodiment of the scintillator of the present invention, FIG. 2 is a process diagram showing one embodiment of the method for manufacturing the same scintillator, and FIG. 3 is a diagram showing another embodiment. 4 is a sectional view showing a conventional scintillator installed in a scanning electron microscope, FIG. 5 is a sectional view of a conventional scintillator, and FIG. 6 is a phosphor layer of the same scintillator. It is a sectional view of the vicinity. 2... Transparent conductive film, 3... Phosphor layer, 4... Light shielding film, 5... Backing film, 7... Gelatin film, 8...
・A11li, 9...Water, 11...Scintillator,
12...Metshu, 14...Exhaust hole agent's name Patent attorney Shigetaka Kurino Haka18 Iris figure 8Al# ＼j1 Shisochi radar/Tagaito destination j+・ump figure I2 Metosh＼ S6 Shining light figure

Claims (3)

[Claims] (1) A scintillator characterized by having a light-shielding film and a backing film made of a light-transmitting polymer in close contact with the light-shielding film above the phosphor layer. (2) The scintillator according to claim 1, wherein the light shielding film is made of at least a single-layer or multi-layer Al thin film, and has a total thickness of 1500A or less. (3) After sequentially forming a base layer that dissolves in a specific solvent, a backing film made of a transparent polymer that does not dissolve in the solvent, and a thin film for a light shielding film on the substrate, the substrate is immersed in the solvent. A method for producing a light shielding film for a scintillator, characterized in that the thin film of the light shielding film is peeled off together with the backing film by dissolving and removing the base layer.