JPH02114193A - Manufacture of thin film radiation detector - Google Patents

Abstract

PURPOSE:To obtain a radiation detector capable of projecting an image from the reverse side with high sensitivity without the generation of secondary radiation by sputtering an inorganic substance, whose main components are fluorescent substances of boron nitride and zinc sulfide, on an inorganic board. CONSTITUTION:Zinc sulfide in which silver, copper and the like are activated as zinc sulfide system fluorescent substance used together with boron nitride is used and specially silver activation zinc sulfide and the like are good. The boron nitride and zinc sulfide system fluorescent substance are formed separately or as a mixture. The rate of zinc sulfide system fluorescent substance to boron nitride of 100 weight parts is normally not much exceeding about 1-30 weight parts. An inorganic board endures desintering temperature and small neutron absorption coefficient is fine, for example, aluminium oxide or silicon carbide and the like are used. The thickness of the inorganic board is normally about 0.1-2.0mm. A sputtering method is applied to one which is generally performed. Thereby, because the sensitivity thereof is high to neutrons and it is thin, it is applied to wide applications.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a thin film radiation detector by a sputtering method.

(Prior Art) With the recent remarkable development of the nuclear power industry, radiation shielding in nuclear facilities has become important. Furthermore, the use of radiation is increasing in fields such as analytical chemistry and medicine, and there is an urgent need to develop radiation shielding materials and materials with radiation sensing performance. In particular, materials with radiation-sensing performance are widely sought after, not only to protect radiation workers from the danger of radiation exposure, but also for various analyzes that use radiation, structural analysis, and measurements of integrated intensity of radiation.

Conventionally, a method has been used in which a composition containing a fluorescent pigment (for example, calcium tungstate, silver-activated zinc sulfide) that emits light when exposed to radiation is applied to the surface of a molded article (for example, a sheet-like article).

In addition, some of the present inventors previously developed a polyethylene resin composition consisting of a polyethylene resin, a large amount of inorganic silicon compound, and a zinc sulfide-based phosphor (Japanese Patent Application Laid-Open No.
No. 6-133349).

(Problems to be Solved by the Invention) In the former coating method, the fluorescent pigment has low sensitivity and cannot be detected unless exposed to a considerable amount of radiation. In addition, there are problems such as the generation of secondary radiation, so it is not very effective as a sensing material for trace amounts of radiation.
There are safety issues, including the generation of secondary radiation, radiation operation issues, and environmental pollution.

On the other hand, in the case of the latter composition, when the molded product obtained by molding reflects and absorbs neutrons.

Demonstrates good effects. However, since it does not transmit neutrons, if you try to project an image from the other side, you will not be able to see it sharply.

Based on the above, the present invention aims to obtain a thin film radiation detector that has good sensitivity to trace amounts of radiation, does not generate secondary radiation, and can project an image from the opposite side.

(Means and effects for solving the problems) According to the present invention, these problems are solved by sputtering an inorganic substance containing boron nitride and zinc sulfide-based fluorescent substances onto an inorganic substrate. A method for manufacturing a thin film radiation detector.

It can be solved by The present invention will be specifically explained below.

(A) Zinc sulfide-based fluorescent substance and its ratio In the present invention, the zinc sulfide-based fluorescent substance used together with boron nitride includes zinc sulfide activated with metals such as silver, copper, manganese, and lead. can give. Among these, silver-activated zinc sulfide is preferred.

In carrying out sputter linking of lil nitride* and zinc sulfide-based fluorescent materials as described later, they are molded separately or as a mixture. The size of the molded product may generally be the size commonly used in the field of Suba Interlink. Generally, the diameter is 10 to 300 cm, and 10 to 2
A value of 50 cm is desirable, and a range of 20 to 2001 is particularly preferred. The shape may be disc-like or angular.

The ratio of zinc sulfide-based fluorescent substance to 100 parts by weight of boron nitride is usually 1 to 30 parts by weight, particularly 1 to 2 parts by weight.
If the ratio of zinc sulfide-based fluorescent material to 100 parts by weight of boron nitride is preferably 1 part by weight, the radiation sensing performance will be extremely low. On the other hand, if it exceeds 30 parts by weight, it becomes difficult to sinter the target material.

(11) Inorganic substrate Also, the inorganic substrate used in the present invention must be made of a material that can withstand the desintering temperature during sputtering, which will be described later. Furthermore, the substrate is required to be easily transparent to radiation, and it is desirable that the substrate has a small linear absorption coefficient for neutron beams.

Since the linear absorption coefficient increases as the atomic number of the substance increases, it is preferable that the atomic number be as small as possible. Also, a temperature higher than the melting point or desintering temperature, i.e. 6
00'C or higher (preferably 80,000 or higher). For these reasons, aluminum oxide (alumina, AL; L2
03), silicon carbide (5iC), silicon nitride (S
i3N4), aluminum nitride (AiN) is preferable.

Furthermore, the thickness of the inorganic substrate is usually 0.1 to 2.0 am.
(preferably 0.1 to 1.0 am). It is difficult to create an inorganic substrate with a thickness of less than 0.1 layer weight.

On the other hand, if it exceeds 2.0111, the absorption of neutrons will be large and the sensitivity will not be good.

(C) Sputtering method To sputter an inorganic material containing boron nitride and zinc sulfide-based fluorescent materials as main components onto the inorganic substrate,
A commonly used method may be applied. The sputtering conditions are RF (high frequency) output or usually 1.0 to 6.
0 W/cm'', especially from 1.0 to 5.0
W/c rn” or preferably.RF specific output 1.0W/
If the temperature is less than cm', the plasma will not be stable.

On the other hand, if it exceeds 6.0 W/cm', there is a possibility that the target material will be destroyed due to thermal shock. In addition, as a sputtering gas source, argon gas is generally used,
At this time, the gas pressure is generally 1.0×10-' to 5.
Ox 10-2 torr, especially 1.0x10
1. Ox 10-2 torr is preferable. If the gas pressure is less than 1. Particles may get mixed into the membrane, deteriorating membrane performance.

Furthermore, the sputter link temperature is usually between room temperature and 200°C.
°C, particularly room temperature to 150 °C. Further, the obtained film thickness is generally 0.1-10 .mu.m, preferably 0.2-10 .mu.m.

If the film thickness is less than 0.1 μl, the radiation sensing performance of the resulting radiation detector will be low. On the other hand, if it exceeds 10 μι, problems arise from the viewpoints of film strength and cost.

The laminate sputtered in this way has a thickness of 600 to 15
It is sintered at 00°C (preferably 600-1200°C).

(Examples and Comparative Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The sputter link target material used in the examples was boron nitride (average particle size: 3.5 pm, purity: 9
9.99%) is sintered by hot pressing method to a thickness of 6. A disc (diameter: 10100a) was used.
cm', average particle size 7p-m) was sintered in the same way,
A disk (diameter 1001 mm) with a thickness of 6.0+ss was used.

Furthermore, as an inorganic substrate, an alumina substrate (diameter: 50 mm) with a thickness of about 0.5 ms was used, which had been degreased, cleaned, and etched in advance.

Example l The boron nitride sputtering target material and the silver-activated zinc sulfide sputtering target material obtained as described above were placed in a high-frequency magnetron sputtering machine (manufactured by Nippon Shinku Co., Ltd., model SMH2304RH), and the sputtering target material of silver-activated zinc sulfide was placed under argon pressure. The output of the boron nitride target material is 30OW (: 1.7W /
crn'), the output of the silver-activated zinc sulfide target material was adjusted to 200W (2.6W/crn'),
The alumina substrate was kept at 250° C. and sputtering was performed for 100 minutes.

An end view of the obtained radiation detector is shown in FIG.

In FIG. 1, 1 is an alumina substrate, and 2 is a mixed film of boron nitride and silver-activated zinc sulfide.

The thickness of the thin film of the obtained radiation detector was 2. OILtm, and the ratio of silver-activated zinc sulfide in this film is 10% of boron nitride.
It was 101 parts by weight compared to 0 parts by weight.

Example 2 The ratio of silver-activated zinc sulfide in the thin film of the radiation detector obtained in Example 1 was 20 parts by weight to 100 parts by weight of boron nitride.
A radiation detector was produced in the same manner as in Example 1, except that the parts by weight were changed (the thickness of the thin film was the same as in Example 1).

Example 3 A radiation detector was manufactured in the same manner as in Example 1, except that the thickness of the thin film of the radiation detector obtained in Example 1 was changed to 0.5 μl (silver-activated sulfurization of boron nitride in the thin film). The proportion of zinc is the same as in Example 1).

Example 4 As in Example 1, only boron nitride was first sputtered. Then, only silver-activated zinc sulfide was sputtered on the thin film (the thickness of the obtained thin film and the ratio of silver-activated zinc sulfide to boron nitride were the same as in Example 1). FIG. 2 is an end view of a thin film radiation detector. In this drawing, 1 is an alumina substrate, and 3 is a boron nitride film. Further, 4 is a silver-activated zinc sulfide film.

Each of the radiation detectors obtained in Examples 1 to 4 was heat-treated for spatter film (thin film) at 800° C. for 2 hours in a nitrogen atmosphere. By performing this heat treatment, the silver-activated zinc sulfide particles crystallize in the thin film of the detection object obtained in Example 4 as in Examples 1 to 3, and neutron-photoconversion occurs at the interface with the boron nitride particles. or had been formed.

Trigger II
When exposed to thermal neutrons emitted from a nuclear reactor, the photosensitive paper placed in front of the detector was exposed, confirming that the sensitivity was superior to conventional products.

(Effects of the Invention) The thin film radiation detector of the present invention is highly sensitive to neutrons, and a thin detector can be manufactured, which can be used for a wide range of applications. An example of its use is a television converter.

[Brief explanation of drawings]

FIG. 1 is an end view of a radiation detector obtained in Examples 1 to 3, and FIG. 2 is an end view of a radiation detector obtained in Example 4. l... Alumina substrate 2... Mixed film of boron nitride and silver-activated zinc sulfide 3
...Boron nitride film 4...Silver activated zinc sulfide film

Claims (1)

[Claims] A method for producing a thin film radiation detector, characterized by sputtering an inorganic substance containing boron nitride and zinc sulfide-based fluorescent substances onto an inorganic substrate.