JPH0560871A - Radiation detection element - Google Patents

Abstract

PURPOSE:To facilitate the hermetical sealing of a scintillator and to enhance detection efficiency without lowering resolving power by laminating a panel constituted by embedding scintillators in a plurality of recessed parts and a light detecting panel having a plurality of pixels to integrate both of them. CONSTITUTION:A two-dimensional optical sensor 300 has many pixels 30 formed on a glass substrate 200 as a two-dimensional array and a scintillator embedded panel 400 has many scintillators 42 embedded in many recessed parts of a silicon substrate 41. The pixels 30 and the scintillators 42 respectively correspond to each other at symmetric positions. Since the scintillators 42 are separated at every openings of the substrate 41, cross talk is reduced and, therefore, high resolving power is realized. Further, since the interior of the substrate 41 functions as the reflecting surface of scintillation light, detection efficiency is high. Furthermore, since a reflecting film 44 is provided, detection efficiency further becomes high. Since the deliquescent scintillators are protected by the adhesion of the panel too or the sensor 300, the deterioration of sensitivity is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detecting element.

[0002]

2. Description of the Related Art A radiation detecting element is constructed by combining a scintillator and a light detecting panel. As such a conventional technique, there is one in which a scintillator is attached to the entire surface of a two-dimensional photosensor. However, this has the drawbacks that the resolution decreases due to the crosstalk of the scintillator, and the two-dimensional optical sensor is easily damaged.

On the other hand, there is also known a radiation detecting element in which a scintillator is attached to the upper part of the optical fiber plate and the light passing through the optical fiber plate is received by a two-dimensional optical sensor. However, the optical fiber plate is expensive and the device becomes large. Moreover, if the scintillator is made thick to increase the detection efficiency, the resolution is likely to be lowered.

In order to overcome the above-mentioned drawbacks of the prior art, a large number of irregularities are formed on the surface of the optical fiber plate,
A technique in which a scintillator is attached here is disclosed in, for example, JP-A-61
-225739 and 63-212279.

[0005]

However, according to the technique of the above-mentioned publication, in order to achieve pixel separation, it is necessary to provide a step difference in the core glass and the clad glass, which is about the same as or more than the thickness of the scintillator. .. If this step is approximately the same as the fiber diameter, scintillator filling is possible, and when detecting low-energy radiation with a high S / N detector, there is not much problem. However, in order to detect high-energy radiation with a two-dimensional optical sensor made of an amorphous semiconductor, the scintillator is required to have a thickness of about 300 μm.

For example, a step of 300 μm is formed on a core or clad of a fiber having a diameter of about 10 μm,
If a scintillator having a particle size of 1 is attempted to be packed, it is very difficult to fill the entire surface of the fiber plate without any defect, and insufficient filling amount or non-uniformity causes insufficient signal amount and uneven sensitivity. When a fiber plate with a large fiber diameter is used (for example, a diameter of about 100 μm), the scintillator is uniformly filled, but the scintillator cannot be positionally matched with the light receiving part of the two-dimensional optical sensor, and the scintillator is embedded by etching the entire surface. However, the light from the fiber at the position where there is no light receiving part is also picked up by the surrounding sensors as stray light, which causes a decrease in resolution.

Further, in the technique of the above publication, the excitation light in the scintillator of the clad portion is not incident light to the sensor, so that the aperture ratio becomes small and the amount of light inevitably decreases, so that the aperture ratio is 100%. The thickness (that is, the etching amount) of the scintillator must be made thicker than that of. This further increases the difficulty of filling the scintillator.

Further, in any of the above-mentioned prior arts, in the case of a deliquescent scintillator, the sensor itself is
Must be packaged in a vacuum or N ₂ sealed package.
According to Japanese Patent Laid-Open No. 63-215987, a method of depositing CsI and then depositing a xylene-based resin by a CVD method is described as a measure against deliquescent. However, it completely covers a scintillator surface having a large number of irregularities and engravings. It is very difficult to do so, and the sensitivity deteriorates even with one pinhole.

An object of the present invention is to provide a radiation detecting element which solves the problems of the prior art.

[0010]

A radiation detecting element according to the present invention comprises a scintillator-embedded panel having scintillators embedded in a plurality of recesses formed in a substrate at a predetermined pitch, and a light having a plurality of pixels. It is characterized in that it is attached to a detection panel and integrated.

[0011]

According to the structure of the present invention, since the scintillator-embedded panel and the light detection panel are bonded and integrated, the scintillator can be easily sealed. Further, since the scintillator is embedded in the recess, the scintillator can be thickened according to the depth of the recess, and the detection efficiency can be improved without lowering the resolution. Further, by forming the moisture-proof protective film and the reflective film, it is possible to further improve the moisture resistance and the detection efficiency.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments of the present invention will be described below with reference to the accompanying drawings.

First, prior to the description of the main part of the embodiment, the overall construction of a radiation detecting apparatus using the radiation detecting element of the present invention will be explained. FIG. 10 is a perspective view showing the entire structure, in which a radiation shield plate 100 made of lead is floated and drawn. A two-dimensional optical sensor 300 including a photodiode (PD) and a thin film transistor (TFT) is formed in the center of the glass substrate 200, and the scintillator-embedded panel 4 is formed thereon.
00 is pasted together. In addition, the two-dimensional optical sensor 30
The vertical shift register 500 is provided on the glass substrate 200 along one side of 0, and the horizontal shift register 600 is provided on the glass substrate 200 along the other side of 0. The vertical shift register 500 is for pixel scanning, the horizontal shift register 600 is for data output, and the output data is taken out as an image signal from an amplifier 700 provided on the glass substrate 200.

The present embodiment is characterized in that the two-dimensional optical sensor 300 and the scintillator-embedded panel 400 are attached to each other in the above-mentioned substrate structure, which is shown in FIG.
It is as the perspective view shown by the partial cross section of FIG. That is,
The two-dimensional optical sensor 300 has a plurality of pixels 30 formed as a two-dimensional array on the glass substrate 200, while the scintillator-embedded panel 400 has a plurality of scintillators 42 embedded in a plurality of recesses of a silicon substrate 41. Have,
Each pixel 30 and each scintillator 42 correspond at symmetrical positions.

In such a radiation detecting element, when a radiation such as an X-ray or a gamma (γ) ray is incident from the upper side of FIG.
Detected as 0. This output is the vertical shift register 50
0 is read by the horizontal shift register 600, amplified by the amplifier 700, and output.

Each pixel 30 of the two-dimensional photosensor 300
Are configured as shown in FIG. FIG. 2A shows the pixel 3
0 is a plan view, and FIG. 3B is a sectional view. Each pixel 3
Reference numeral 0 has a photodiode 31 as a photo-detecting cell and a thin film transistor 32 as a switch. The photodiode 31 is configured as a Pin silicon photodiode on the source electrode 33 of the thin film transistor 32.
The anode electrode 34 of the photodiode 31 is connected to the common line 35, the drain electrode of the thin film transistor 32 is connected to the drain line 36, and the gate electrode thereof is connected to the gate line 37. The drain line 3
6 is connected to the horizontal shift register 600, and the gate line 37 is connected to the vertical shift register 500. Then, a light shielding film 38 is provided on the thin film transistor 32 with an insulating film interposed therebetween so that scintillation light does not enter the thin film transistor 32.

FIG. 3 is a sectional view showing a correspondence relationship between the pixel 30 and the scintillator 42. Scintillator embedded panel 40
Openings are formed in the silicon substrate 41 forming the main body of 0 corresponding to each pixel 30 of the two-dimensional photosensor 300, and the scintillator 42 is embedded therein. Then, the upper surface is covered with a protective film (SiO ₂ film) 43, and a reflective film 44 made of aluminum, chromium or the like is formed thereon. According to this structure, X-rays and gamma rays from above are reflected by the reflection film 4.
4 and the protective film 43 to reach the scintillator 42 to cause scintillation light emission. This photon enters the photodiode 31 and is detected. On the other hand, the scintillation light emitted upward is also reflected by the reflection film 44 and enters the photodiode 31, so that the detection efficiency is high. The scintillator 42 in this case is C
sI (cesium iodide) or the like is used.

FIG. 4 is a cross-sectional view of another example showing the correspondence between the pixels 30 and the scintillators 42. Also in this case, the opening provided in the silicon substrate 41 corresponds to the photodiode 31, and Gd ₂ O ₂ S is embedded therein as the scintillator 42. In this case, since the scintillator 42 has no deliquescent property, the opening of the silicon substrate 41 is not configured to be sealed by the two-dimensional optical sensor 300. The details will be described later.

Next, the manufacturing process of the bonded structure of the two-dimensional optical sensor 300 and the scintillator embedded panel 400 will be described.

FIG. 5 and FIG. 6 are cross-sectional views by manufacturing process corresponding to the embodiment of FIG. First, the top and bottom
A silicon substrate 41 having a 100> surface is prepared, and a protective film 4 made of SiO ₂ and having a thickness of about 1 μm is formed by a thermal oxidation method.
3 is formed (see FIGS. 5A and 5B). By thermal oxidation, a pinhole-free film can be formed.

Next, a large number of openings 46 are formed in the protective film 43 on the upper surface by using the photolithography technique. Then, the number and position of the openings 46 correspond to the pixels 30 of the two-dimensional optical sensor 300 to be bonded (FIG. 5).
(See (c)). Here, the opening 46 is constituted by a line of intersection of the <110> plane of the <111> plane and a <110> plane, and when the opening 46 is placed in a potassium hydroxide solution, the difference in etching rate (in the lateral direction) (Vertical direction is 400 times)
Thus, a vertical opening 47 is formed in the silicon substrate 41 (see FIG. 5D).

Next, the protective film 4 on the lower surface of the silicon substrate 41.
By vacuum-depositing aluminum or the like on the film 3, a reflection film 44 for reflecting scintillation light is formed (FIG.
(See (a)). After that, for example, CsI (Na) is used as the material of the scintillator 42 and the opening 4
7 and removes unnecessary portions (see FIG. 6B).

Next, after being appropriately processed, the two-dimensional optical sensor 300 separately manufactured on the glass substrate 200.
Together with the glass substrate 200, the scintillator-embedded panel 4
No. 00 (see FIG. 6C) and are bonded by an adhesive 49. At this time, the scintillator 42 and the photodiode 31 correspond to each other (see FIG. 6).
(See (d)).

In the radiation detecting element manufactured by the above process, one of the scintillators 42 embedded in the opening 47 of the silicon substrate 41 is covered with a protective film 43 by thermal oxidation without pinholes, and the other is a two-dimensional light. Sensor 300
Since it is hermetically sealed via the adhesive 49, it is not breathable, and therefore the deliquescent problem peculiar to CsI or the like does not occur. Further, Si ₃ N _{4 is provided} between the protective film 43 and the reflective film 44.
If the film is formed by a sputtering method or a CVD method, the film strength is improved and the yield in operation becomes good.

FIG. 7 shows a process corresponding to the embodiment of FIG. First, as shown in FIG. 7A, an opening 47 is formed in the silicon substrate 41 by the same steps as those shown in FIGS.
To form. Next, Gd ₂ O ₂ S having a low deliquescent property is embedded as a material of the scintillator 42 by the sedimentation method (FIG. 7B).
reference). At this time, Gd ₂ O ₂ is also applied to the portion other than the opening 47.
S is deposited, but the protective film (S
An iO ₂ film) 45 and a reflective film 44 of aluminum or the like are formed. Then, the two-dimensional optical sensor 300 is attached together with the glass substrate 200 from the lower surface (see FIG. 7C).

In the case of the process of this embodiment, since the scintillator 42 is Gd ₂ O ₂ S having no deliquescent property, the two-dimensional photosensor 300 can be attached to the lower surface of the silicon substrate 41. Further, since the silicon substrate 41 has a function of blocking scintillation light, it is not necessary to remove Gd ₂ O ₂ S on the upper surface of the silicon substrate 41.

FIG. 8 shows the steps when the scintillator manufacturing process does not damage the two-dimensional optical sensor 300. First, the glass substrate 200 having the two-dimensional optical sensor 300 formed thereon and the silicon substrate 41 having the protective film 43 formed on the surface thereof are prepared and bonded. At this time, the alignment mark 9 is placed outside the light receiving area on the glass substrate 200.
1 is formed. Then, a photoresist film 92 is coated on the protective film 43 and exposed using a photomask 93. At this time, the alignment mark 99 is provided on the photomask 93 together with the chrome pattern 94 on the glass substrate 20.
It is provided so as to correspond to the alignment mark 91 above 0 (see FIG. 8A).

In this way, the photomask 93 is aligned, and the opening 46 is formed by exposure, phenomenon, and selective etching of the protective film 43. Then, by the sedimentation method, Gd ₂
After the scintillator 42 made of O ₂ S is embedded and unnecessary portions are removed, the protective film 45 and the reflective film 44 are formed (see FIG. 8C). According to this process, the alignment of the scintillator 42 and the pixel 30 is adjusted by the alignment mark 91.
And the alignment mark 99 enables accurate operation.

FIG. 9 shows a modification of the radiation detecting element according to FIG. In this case, the opening 47 is formed by etching the silicon substrate 41 with an etchant having weak anisotropy. Therefore, the opening 47 is tapered and the scintillator 42 is embedded therein. When the aperture ratio of the light receiving surface of the two-dimensional optical sensor 300 is small, the effective area for radiation detection is expanded, so that the S / N ratio can be improved.

The effects and advantages of the embodiments described above are listed below. First, as a characteristic advantage,
Since the scintillator 42 is separated for each opening 47 of the silicon substrate 41, crosstalk is small, and therefore high resolution can be realized. Moreover, since the inside of the silicon substrate 41 functions as a reflection surface of scintillation light, the detection efficiency is increased. Further, by providing the reflective film 44, the efficiency can be further improved. Furthermore, since the window material of the scintillator portion is formed to be very thin, it has excellent radiation transmittance.

Next, as an advantage of the manufacturing process, since it can be manufactured by the silicon wafer process established as a semiconductor process, the manufacturing cost is low. Moreover, since the pattern design and change of the opening 47 in which the scintillator 42 is embedded are easy, it is possible to match with the various two-dimensional optical sensors 300. Furthermore, the two-dimensional optical sensor 30
The scintillator manufacturing process can be performed without damaging 0.

Further, as an advantage on the device, it is cheaper than the optical fiber plate and can have a high aperture ratio. Further, it is relatively easy to increase the size. Furthermore, if the adhesion of the two-dimensional optical sensor 300 and the scintillator embedded panel 400 to protect the scintillator SiO ₂ film and the reflection film 44 with a deliquescent (e.g. CsI (Na), etc.), vacuum or N ₂ filled You do n’t have to put it in a package,
There is no concern about sensitivity deterioration.

[0033]

As described above in detail, according to the structure of the present invention, the scintillator-embedded panel and the light detection panel are bonded and integrated, so that the scintillator can be easily sealed. Also, because I decided to embed it in the recess,
The scintillator can be thickened according to the depth of the recess, and the detection efficiency can be improved without lowering the resolution. further,
By forming the moisture-proof protective film and the reflective film, it is possible to further improve the moisture resistance and the detection efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross section of a part of a radiation detecting apparatus using a radiation detecting element according to an exemplary embodiment.

FIG. 2 is a diagram showing a configuration of one pixel 30 of the two-dimensional photosensor 300 of the embodiment.

FIG. 3 is a sectional view of a main part of the embodiment.

FIG. 4 is a cross-sectional view of a main part of another embodiment.

FIG. 5 is a manufacturing process diagram corresponding to the embodiment of FIG. 3;

FIG. 6 is a manufacturing process diagram corresponding to the embodiment of FIG. 3;

FIG. 7 is a manufacturing process diagram corresponding to the embodiment in FIG. 4;

FIG. 8 is a manufacturing process diagram according to a modification.

FIG. 9 is a cross-sectional view of a modified example.

FIG. 10 is a perspective view of a radiation detection apparatus to which the radiation detection element according to the exemplary embodiment is applied.

[Explanation of symbols]

 100 ... Radiation shielding plate 200 ... Glass substrate 300 ... Two-dimensional photosensor 30 ... Pixel 31 ... Photodiode 32 ... Thin film transistor 36 ... Drain line 37 ... Gate line 400 ... Scintillator embedded panel 41 ... Silicon substrate 42 ... Scintillator 43 ... Protective film 44 ... Reflective film 49 ... Adhesive agent 500 ... Vertical shift register 600 ... Horizontal shift register 700 ... Amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuya Honme 1 1126 Ichinomachi, Hamamatsu City, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Toshio Takabayashi 1126 Hamamatsu City, Hamamatsu City, Shizuoka Prefecture 1 Hamamatsu Photonics Within the corporation

Claims (5)

[Claims] 1. A scintillator-embedded panel configured by embedding a scintillator in a plurality of recesses formed in a substrate at a predetermined pitch, and a photodetection panel having a plurality of pixels are bonded and integrated. Radiation detecting element. 2. The plurality of pixels of the photodetection panel are formed at the same pitch as the plurality of recesses of the scintillator-embedded panel, and each of the plurality of pixels and each of the plurality of recesses are positioned. Claim 1
The radiation detection element described. 3. The radiation detection element according to claim 1, wherein the plurality of recesses in which the scintillator is embedded are sealed by the light detection panel. 4. The radiation detecting element according to claim 1, wherein the surface of the scintillator is covered with a moisture-proof protective film. 5. The radiation detecting element according to claim 1, wherein a light reflecting film is formed on a surface of the scintillator-embedded panel opposite to the light detecting panel.