JPH0334248A - Electron beam sensor - Google Patents

Abstract

PURPOSE:To form an electron beam sensor offering excellent durability and efficiency as compared with fluorescent powder by forming the sensor into a circular truncated one while an Ag metal back coat is applied. CONSTITUTION:An electron beam sensor made up from a mono-crystal oxide, for example, CexY(1-x)AlO3, is formed into a circular truncated cone. In this case, an angle formed by an outgoing surface 1 and a side inclined surface 2 shall be 33 deg., and the whole of the surface of a mono-crystal element in a circular truncated cone shape which is as thin as 2mm for example, is polished to a mirror-like surface so that Ag is applied onto an incident surface 3 and the inclined surface 2 in the form of an Ag metal back coat 4 as thin as 500Angstrom . MgF2 with a specified refraction factor is deposited onto the incident surface of the specimen to the extent as thin as lambda/4 so that loss in refraction is minimized. Applying the metal back coating permits the electron beam sensor to be obtained, which offers excellent durability and emission efficiency as the electron beam sensor while being low in loss in refraction but high in efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to an electron beam sensor used in a scanning electron microscope (SEM), etc., and particularly relates to an oxide single crystal electron beam The present invention relates to a sensor element.

[Conventional technology]

Conventionally, as an electron beam sensor, an electron beam sensor using powder phosphor 9 (for example, commercially available phosphor P-47, etc.) has been used. As shown in FIG. 4, an electron beam sensor using a powder phosphor 9 is made by depositing the powder phosphor 9 on a glass substrate 8 and coating the surface with a metal backcoat such as A1. As the metal back material, AI gold metal, which has a relatively small atomic number and is easily transmitted by electron beams, is used. Light (hereinafter referred to as CL) from the phosphor excited by the electron beam transmitted through the A1 metal back coat 10 is generated, and the tip of the CL enters the glass substrate while diffusing inside the powder and is located behind it. After passing through a light guide tube (light pipe), the light reaches a photomultiplier tube (photomultiplier) and is converted into an electrical signal. At this time, since the refractive index (n2) of the glass substrate is different from the refractive index (nl) in vacuum, a reflection loss occurs as shown by the following equation.

R” (n2 n+ / n+ 10rl)2 (when the angle of incidence of light is 0 degrees) As the angle of incidence increases, the reflection loss increases, and total reflection occurs at a critical angle of 0 or more shown by the following formula. , is injected to the outside from the side of the glass substrate.

θ=si' (n+/n2) For the above reasons, an electron beam sensor using a conventional powder phosphor can only extract about 50% of the CL light.

On the other hand, when the phosphor is a single crystal, its refractive index is higher than that of glass, so the reflection loss is even greater.

For example, when a YAG single crystal with a refractive index of 1.8 is used as an element, the light detected by a photomultiplier is less than 25% of the actually emitted light.

Therefore, an electron beam sensor made of powdered phosphor, which can extract a large amount of light, is more advantageous. However, with phosphor powder, the light reflected from the glass surface in contact with the vacuum system is repeatedly scattered again by the phosphor surface, resulting in an apparent longer light lifetime and lower resolution. . Furthermore, when phosphor powder is used in an element, there is a problem in that it deteriorates due to ultraviolet rays or electron beams, so it must be replaced every few years.

[Problem to be solved by the invention]

The present invention aims to improve the efficiency of an oxide single crystal electron beam sensor, which is durable as an electron beam sensor, by improving its shape and surface condition, thereby providing a durable and highly efficient electron beam sensor.

9. Structure of the Invention [Means for Solving the Problems] The present invention provides an electron beam sensor made of an oxide single crystal having a truncated conical shape, and the electron beam irradiation surface of the single crystal element is coated with Ag (
The present invention attempts to provide an electron beam sensor element with low reflection loss, high resolution, and long life by applying a metal back coating to fi).

That is, the present invention provides an electron beam sensor using an oxide single crystal doped with fluorescent ions as a detector, wherein the oxide single crystal electron beam sensor element has a truncated conical shape; In the electron beam sensor,
The present invention provides an electron beam sensor characterized in that the electron beam irradiation surface of a truncated conical oxide single crystal electron beam sensor element is coated with Ag (#).

[Effect]

Most of the light traveling in the direction perpendicular to the surface of the electron beam sensor (
(excluding reflection loss of 8%) is emitted from the light exit surface, and light traveling at an angle close to the horizontal direction is also corrected in the vertical direction by the truncated conical side inclined surface and exits from the light exit surface. Since there is no scattering compared to when phosphor powder is used, the apparent lifetime of the fluorescence is not as long.

In addition, single crystals have fewer crystal defects than powders, so energy propagates smoothly within the crystal and can effectively excite light-emitting ions, so single crystals have lower optical efficiency than powders. A good element can be obtained. Further, the light emitted to the metal back coat side is reflected by the Ag metal back coat film and exits from the light exit surface, but since Ag has a higher reflectance than AI, more light can be obtained than with AI.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

In this example, CezY(1-χ)AIO, a single crystal oxide (hereinafter referred to as Ce:YAP), which is an oxide single crystal containing Ce3+ ions, was used as the fluorescent ion. The raw materials include Y2 (h, A12o3, and C
A single crystal with a cefi degree of 1.0 at% was grown using eO2. FIG. 1 shows a front sectional view of an electron beam sensor element according to the present invention. The light emitting surface 1 was 9φ, and the angle between the light emitting surface 1 and the side inclined surface 2 was 33 degrees. A truncated conical C with a thickness of 2 mm
e: After mirror-polishing the entire surface of the YAP single crystal element, the incident surface 3 and side inclined surfaces 2 were coated with Ag metal back coat 4 to a thickness of 500 angstroms. MgF2 with a refractive index of 1.38 was placed on the incident surface of this sample at λ/4 (
In this example, λ=0.38 μm) was deposited to minimize reflection loss. The truncated cone-shaped Ce: YAP single crystal 6 coated with Ag metal back coat 4 of this example
A sample (a) using an electronic sensor element according to the present invention, and a comparative sample (b) in which an element according to the present invention is coated with an AI metal back coat, and a disk-shaped sample with a diameter of 9 cm and a thickness of 2+ cm with a mirror finish on the entire surface. Ce: A comparison was made between a sample (c) using YAP single crystal 7 and a sample (d) using a commercially available electron beam sensor element (P-47) of powdered phosphor 9.

The composition of this P-47 is Cez Y(2-z)Sin
5 has an Al metal back coat 10. These samples were irradiated with an electron beam at an acceleration voltage of 10 KV, and the electron beam fluorescence intensity (CL) was measured.

The results are shown in FIG. When the open light intensity of a disk-shaped Ce:YAP single crystal element (sample (C)) with mirror polished surfaces on both sides is 1, the element of this example (sample (a)) has an intensity of 6.
, At metal back coated element (sample (b))
It was 5°5 for P-47 (sample d) and 2 for P-47 (sample d).

As shown in Figure 5, the deterioration due to electron beam irradiation is
It was observed only in single crystals, and was not observed at all in single crystals.

When the element according to the present invention and P-47 were attached to a SEM apparatus and images were observed, the images were brighter and had better resolution than P-47.

C. Bright effect [6. Bright effect] As described above, according to the present invention, the shape of the electron beam sensor is shaped like a truncated cone, and by coating it with an Ag metal back coat, it is more durable than powdered phosphor. A highly efficient electron beam sensor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing an electron beam sensor element according to an embodiment of the present invention. FIG. 2 is a front cross-sectional view showing another embodiment of the present invention, in which an At metal back coat film is deposited on an electron beam sensor element. FIG. 3 is a front sectional view showing a conventionally used disc-shaped electronic cotton sensor element, which is coated with an Ag metal back coat. Figure 4 shows the conventionally used powder phosphor (P-47).
FIG. 2 is a front sectional view of an electron beam sensor. Figure 5 shows the electron beam fluorescence intensity (CL) of this example and comparative example.
A graph showing changes over time. DESCRIPTION OF SYMBOLS 1... Light exit surface, 2... Side inclined surface, 3... Incident surface, 4... Ag metal back coat, 5... MgF2
Anti-reflection coating film, 6... truncated conical Ce: YAP
Single crystal, 7...Disc-shaped Ce:YAP single crystal, 8...
-Glass substrate, 9...Powder phosphor, 10...At metal back coat. Sample (a): A truncated cone-shaped Ce:YAP single crystal electron beam sensor element coated with an Ag metal backcoat according to an example of the present invention. Sample (b): A truncated cone-shaped Ce: YAP single crystal electron beam sensor element made of the same material and finished in the same shape as sample (a) and coated with an At metal back coat. Sample (c)...Same material as sample (a), diameter 9ma
L, 2IIIm thick disk-shaped C with mirror finish on the entire surface
e: YAP single crystal electron beam sensor element. Sample (d): A commercially available phosphor powder electron beam sensor element (P-47).

Claims (1)

[Claims] 1. An electron beam sensor using an oxide single crystal doped with fluorescent ions as a detector, characterized in that the oxide single crystal electron beam sensor element has a truncated conical shape. sensor. 2. In the electron beam sensor according to claim 1, A is provided on the electron beam irradiation surface of the truncated cone-shaped oxide single crystal electron beam sensor element.
An electron beam sensor characterized by being coated with g (silver).