JPH0562712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation detection device, and more particularly to a radiation detection device that is provided with the function of a photodetection element to improve radiation detection sensitivity.

[Technical background of the invention and its problems] Conventionally, as a device for detecting radiation such as X-rays,
Various radiation detection devices made of semiconductors are used. FIG. 4 shows an example of a semiconductor radiation detection device. In the figure, 41 is a W collimator, 42 is an Al electrode,
43 is N-Si, 44 is Au electrode, 45 is NaI (Tl)
A scintillator and 46 indicate a current amplifier, respectively. A multichannel radiation detection device is one in which this device is configured in multiple stages in a direction perpendicular to the X-rays, and is mainly applied to an X-ray CT (computer tomography) device. this is,
In addition to directly detecting X-rays with the detection section consisting of the N-Si 43 and electrodes 42 and 44, the X-rays that have passed through the detection section are further utilized to cause the NaI (Tl) scintillator 45 to emit light, and this light ( The light (indicated by the broken line arrow in the figure) is received again by the detection unit to increase the sensitivity. Therefore, the detection section has two roles: X-ray detection and photodetection.

The problems with this semiconductor radiation detection device are as follows. That is, the depletion layer, which is a part sensitive to light, is formed only on the Au electrode 44 side, and has almost no sensitivity to light incident on the Al electrode 42 side.
The problem is that the light usage efficiency is low.

FIG. 5 is a cross-sectional view showing an example of a semiconductor radiation detection device that has improved the above-mentioned problems (Japanese Patent Laid-Open Publication No.
58-118163). This device has the detection unit
An N ⁺ a-Si:H (N-type amorphous silicon layer) 51, a-Si:H (non-doped amorphous silicon layer) 52, and an Au electrode 53 are laminated on the Al electrode 42. In this structure, X-rays are
- NaI (Tl) scintillator 45 detected by Si 43 and depletion layer formed under Au electrode 44
It is the same as that shown in FIG. 4 in that it receives light (indicated by a broken line in the figure) from the outside. However, the amorphous silicon layers 51 and 52 deposited on the Al electrode 42 operate as a Schottky-type amorphous photodetector, and the NaI (Tl) scintillator 45
In order to be able to detect more light from
It has sensitivity characteristics superior to the semiconductor radiation detection device shown in FIG.

However, even with this type of device, there are the following problems. That is, the NaI (Tl) scintillator 45 receives X-rays, but the emission peak is around 410 [nm], and if the emission intensity at this wavelength is 100 [%], even at a wavelength of 500 [nm].
It has a luminescence intensity of about 30 to 40%. On the other hand, the sensitivity of the Schottky type amorphous photodetecting element to light has a peak at 500 to 600 [nm]. Therefore, the emission of light from the scintillator 45
It has a characteristic that it can fully utilize light of 500 [nm] or more. On the other hand, the sensitivity to light in the depletion layer formed by the Au electrode 44 formed on the N-Si 43 generally has its peak at a wavelength around 700 to 800 [nm], so Sensitivity tends to decrease significantly as the wavelength increases to 500
It is known that the sensitivity near [nm] is very low. Therefore, the degree of utilization of the light emitted by the scintillator is extremely small. Furthermore, there are problems in that the N-Si used in the detection section is expensive and it is not possible to produce crystals with a large diameter, so the device inevitably becomes smaller. Furthermore, the Au used for the shot key electrode was expensive, leading to problems such as high manufacturing costs.

[Purpose of the invention]

The present invention was made in consideration of the above circumstances, and
Its purpose is to have extremely high detection sensitivity when used in combination with a scintillator.
Another object of the present invention is to provide a radiation detection device that can be manufactured in any size at a low cost.

[Summary of the Invention] The gist of the present invention is to form an amorphous semiconductor layer on both sides of a light-transmitting substrate, and to provide the semiconductor layer with a function as a radiation and light detection element.

That is, the present invention provides a radiation detection device that has the function of a photodetection element and improves detection sensitivity. an amorphous semiconductor layer, and a scintillator that is disposed on the opposite side of the substrate and semiconductor layer to the incident side of radiation incident thereon and emits light when irradiated with radiation that has passed through the substrate and semiconductor layer, The semiconductor layer is made to have the functions of both a radiation detection element and a photodetection element.

[Invention effect]

According to the present invention, in addition to directly detecting X-rays with a detection section made of an amorphous semiconductor layer,
The X-rays that have passed through the detection section are further utilized to cause the scintillator to emit light, and most of this light is directly received by the detection section again to increase sensitivity. Moreover, since the substrate is transparent, light enters the semiconductor layers on both sides of the substrate from the substrate side, thereby further increasing the sensitivity. Therefore, very excellent sensitivity characteristics can be obtained. Furthermore, since the amorphous semiconductor layer can be very thin and utilizes plasma reaction, it has excellent selectivity in terms of substrate size and can be formed more easily. Therefore, it is also possible to reduce the manufacturing cost of the device.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a radiation detection device according to a reference example of the present invention. In the figure, reference numeral 10 denotes a detection section having the functions of both an X-ray detection element and a photodetection detection element, and this detection section 10 is arranged between two W collimators 21. The detection section 10 is formed of an Al substrate 11, amorphous silicon layers 12, 13, 14, a SnO ₂ film 15, etc., as described later. A NaI (Tl) scintillator 25 is arranged on the side opposite to the X-ray incident side of the detection unit 10. The scintillator 25 generates light when X-rays that have passed through the detection section 10 are incident thereon, and the detection section 10 is irradiated with the light. The detection signal of the detection section 10 is outputted via the current amplifier 26.

Now, the detection section 10 is formed as shown in FIGS. 2a and 2b. First, as shown in Figure 2a,
N-type a-Si:H (N-type amorphous silicon layers) 12a, 12b, I-type a-
Si:H (non-doped amorphous silicon layer) 1
3a, 13b and P-type a-Si:H (P-type amorphous silicon layer) 14a, 14b are sequentially deposited by glow discharge decomposition plasma CVD method or the like.
Next, as shown in FIG. 2b, SnO ₂ films 15a, 1
5b by sputtering or vapor deposition.

Here, the detection unit 10 is viewed from the X-ray incident side.
SnO ₂ /p-i-n(a-Si)/Al/n-i-p
(a-Si)/SnO ₂ structure, Al substrate 11
It has a parallel connection structure of PIN diodes via. That is, the detection section 10 is divided into a detection section 10b on the X-ray incident side and a detection section 10a on the scintillator side. Note that although the scintillator side of the Al substrate 11 is particularly mirror-finished, mirror-finishing may be applied to both surfaces without any problem. Also, W
The inner surface of the collimator 21 may be coated with Al or the like to increase the light reflection efficiency.

In this reference example, the film thicknesses of the p, i, and n amorphous silicon layers are 100 [Å] or more and 5 [μ
m] or more, and 100 [Å] or more, but for the amorphous silicon layer 13, considering the amount of detected X-rays and the amount of light detected by scintillator emission,
The film thicknesses of the amorphous silicon layer 13b on the line incidence side and the amorphous silicon layer 13 on the scintillator side are determined. Considering the X-ray absorption characteristics of amorphous silicon, the amorphous silicon layer 13b on the X-ray incident side is thicker than 5 [μm].
If possible, it is better to make the film thickness 10 [μm] or more to increase the amount of linear detection of X-rays as much as possible. Also,
The shape and size of the Al substrate 11 may be selected depending on the size of the desired radiation detection device.

In such a structure, the X-rays first enter the detection section 10b, where they are detected. Next, the X-rays that have passed through the detection section 10b are directed to the Al substrate 11.
The X-rays pass through and enter the detection unit 10a, where the X-rays are also detected. The X-rays that have passed through the detection units 10b and 10a are incident on the scintillator 25, causing the scintillator 25 to emit light. The light from the scintillator 25 travels as shown by the dashed arrow in FIG.
Most of the light enters the detection unit 10a, and some of the light is reflected by the W collimator 21 and is transmitted to the detection units 10a, 10a.
It is incident from the side of b. The detection unit 10 detects this light again.
a, 10b detect, and further Al of the detection unit 10a
The light incident on the surface of the substrate 11 is reflected and the detection unit 10
The X-ray detection process is such that the X-rays are detected again at point a.

Here, since most of the light emitted by the scintillator is directly incident on the detection section 10a, the efficiency of using that light is much higher than in the conventional devices shown in FIGS. 4 and 5. Additionally, NaI
(Tl) The emission wavelength of the scintillator 25 is 410 [nm]
Although there is a peak in the vicinity, the emission intensity is sufficient even around 500 [nm], and from the sensitivity characteristics of the detection section 10 (the peak is 500 to 600 nm, but it has sensitivity from about 400 nm), Light can be fully utilized.

As described above, according to this reference example, by providing the X-ray and light detection sections 10a and 10b made of amorphous silicon on both sides of the Al substrate 11,
It is possible to significantly improve the line detection sensitivity. That is,
Although the sensitivity to X-rays is the same or slightly lower than that of the conventional device, the sensitivity to light is significantly improved compared to the conventional device, so the sensitivity as a whole is also improved. Furthermore, since amorphous silicon is deposited using plasma CVD, the shape and size of the substrate can be arbitrarily selected. Furthermore, expensive
There is no need to use Au electrodes or the like. Therefore, it is possible to form a highly selective detection section relatively easily, and there are advantages such as reducing the manufacturing cost of the radiation detection device.

FIG. 3 is a schematic configuration diagram showing a radiation detection device according to an embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted. This example differs from the reference example described above in that an insulating transparent substrate was used instead of the Al substrate. That is, a SnO ₂ film 32a as a transparent conductive film is formed on both sides of the quartz glass substrate 31.
32b are formed respectively. Amorphous silicon layers 12a, 12b, 14a, 14 are formed on these conductive films 32a, 32b.
b and SnO ₂ films 15a and 15b, which are completely the same as in the previous embodiment.

Of course, even with such a configuration, effects similar to those of the previous reference example can be obtained. Moreover, since the light reflected by the collimator 21 and incident on the substrate 31 propagates within the substrate 31 and enters the detection section 10, there is an advantage that detection sensitivity is further improved.

Note that the present invention is not limited to the embodiments described above. For example, the structure of the radiation and light detection section may be a shot key type or a PN type instead of a PIN structure. Alternatively, it may have a nip/Al/pin structure when viewed from the radiation incident side. Furthermore, it is also effective as a tandem structure in which these are laminated. Further, when viewed from the radiation incident side, the structure may be a Schottky type/Al/nip type or the opposite structure, or various combinations thereof may be used. Furthermore, the present invention is also effective even if the I-type a-Si:H (non-doped amorphous silicon layer) is doped with a small amount of P, B, C, Zn, Ge, etc.

Furthermore, the transparent conductive film is not limited to SnO ₂ , and ITO or In ₂ O ₃ may also be used. moreover,
When a Schottky type is used as the detection part structure, it is also effective as a transparent conductive film by thinning a metal with a high work function such as Au, Pt, Ti, Ta, or Pd. In addition, as a conductive substrate, Be,
Any metal that is stable and transmits radiation, such as C, may be used. Similarly, the insulating substrate is not limited to a quartz substrate, and may be any substrate that transmits radiation. Further, although the substrate is arranged in a direction perpendicular to the radiation incident side, it is also possible to arrange the substrate in a horizontal direction. Furthermore, the materials and shapes of the scintillator, collimator, etc. can be changed as appropriate according to specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a radiation detection device according to a reference example of the present invention, FIGS. A schematic configuration diagram showing a radiation detection device according to an embodiment, and FIGS. 4 and 5 are schematic configuration diagrams showing conventional devices, respectively. 10, 10a, 10b... detection section, 11...
Al substrate (transparent conductive substrate), 12...N-type amorphous silicon layer, 13...Non-doped amorphous silicon layer, 14...P-type amorphous silicon layer, 15, 32...SnO ₂ film, 21 ...W
Collimator, 26... Current amplifier, 31... Quartz substrate (transparent insulating substrate).

Claims (1)

[Scope of Claims] 1. A light-transmitting substrate having a transparent conductive film formed on both sides, an amorphous semiconductor layer formed on both sides of this substrate via the transparent conductive film, and the above substrate and semiconductor layer. a scintillator disposed on the opposite side to the incident side of the radiation incident thereon and emitting light when irradiated with the radiation that has passed through the substrate and the semiconductor layer; A radiation detection device characterized by having both functions. 2. The radiation detection device according to claim 1, wherein the main surface of the substrate is arranged in a direction perpendicular to the incident radiation. 3. The radiation detection device according to claim 1, wherein the main surface of the substrate is arranged in a direction parallel to the incident radiation. 4. The radiation detection device according to claim 1, wherein the semiconductor layer has a PIN structure.