JP2013178098A - Radiation detector and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector capable of improving detection characteristics, and to provide a method for manufacturing the radiation detector.SOLUTION: The radiation detector having a detection layer responding to radiation on a substrate forms a polycrystalline film whose average particle diameter is a pixel pitch or less as the detection layer. A film Cl concentration is included within a range of 1 to 10 wtppm, more preferably 3.1 wtppm, and Cl (chlorine) is positively doped to form a polycrystalline film composed of CdZnTe (cadmium zinc telluride) e.g. (CdZnTe film A). Since the polycrystalline film whose average particle diameter is the pixel pitch or less is formed as the detection layer, an image having fine characteristics (spatial resolution, sensitivity, etc.) between pixels can be obtained by the radiation detector. Further, temporal fluctuation also is reduced and detection characteristics related to response characteristics can be also improved. Consequently the detection characteristics can be improved.

Description

  The present invention relates to a radiation detector having a function of detecting radiation including X-rays, γ-rays, light, etc., and used in the medical field, industrial field, and nuclear field, and a method of manufacturing the same, and more particularly to radiation. The present invention relates to a technique in which a sensitive detection layer is composed of a semiconductor and is composed of polycrystal.

  Conventionally, various semiconductor materials, especially CdTe (cadmium telluride), ZnTe (zinc telluride) or CdZnTe (cadmium zinc telluride) crystals have been researched and developed as materials for highly sensitive radiation detectors, and some products It has become. However, in order to apply to a radiation detector for medical diagnosis or a radiation imaging apparatus, it is necessary to form a radiation conversion layer having a large area (for example, 20 cm square or more). Formation of such a large-area crystal is not practical in terms of technology and cost, and a method of forming a polycrystalline film or a polycrystalline laminated film by proximity sublimation is disclosed ( For example, see Patent Document 1).

In a small radiation detector using a CdTe bulk single crystal, zinc (Zn) is doped to reduce leakage current, and halogen such as chlorine (Cl) is used to improve carrier running performance and improve detection performance. The effectiveness of doping is known. As a Cl doping method for the CdTe or CdZnTe polycrystalline film in the proximity sublimation method, a first material containing at least one of CdTe, ZnTe, and CdZnTe, and at least one of CdCl ₂ (cadmium chloride) and ZnCl ₂ (zinc chloride) are used. A method of forming a polycrystalline film or a polycrystalline laminated film by vapor deposition or sublimation using a mixture with a second material containing two as a source is disclosed (for example, see Patent Document 2).

  The evaluation of the grain size composition in the growth of the CdTe polycrystalline film is disclosed (for example, see Non-Patent Document 1), and the spectral analysis of the CdTe polycrystalline film when doped with Cl is disclosed (for example, non-patent document 1). Patent Document 2). Non-Patent Document 2 mentioned above suggests that the crystal grain size is refined by an appropriate amount of Cl doping.

JP 2001-242255 A Japanese Patent No. 4269653

JOURNAL OF APPLIED PHYSICS 103, 063529 (2008) JOURNAL OF APPLIED PHYSICS 99, 053502 (2006)

  However, in order to capture and detect high-energy radiation for medical use by the detection layer, the detection layer needs to have a thickness of several hundred μm or more. When the detection layer is a polycrystalline film such as CdTe, as shown in FIG. 4 of Non-Patent Document 1, the crystal grain size generally increases as the thickness of the detection layer increases. There is a tendency to grow. However, the crystal grain size of the polycrystalline film greatly affects the characteristics (for example, spatial resolution, sensitivity, noise, etc.) of the two-dimensional radiation detector.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the radiation detector which can improve a detection characteristic, and the method of manufacturing it.

  As a result of earnest research to solve the above problems, the inventors have obtained the following knowledge.

  That is, in the past, detection characteristics have been improved by increasing the crystal grain size. However, when the crystal grain size is large, the difference in crystallinity of individual crystal grains and the influence of crystal grain boundaries become remarkable, and the variation in characteristics (for example, leakage current and sensitivity) between pixels becomes large. Furthermore, since temporal fluctuations also increase, these variations become noise sources, making sensitivity correction difficult and degrading image characteristics (detection efficiency). Therefore, the idea of increasing the particle size as in the prior art was changed, and knowledge was obtained that the detection characteristics are improved by suppressing the variation by reducing the particle size.

The present invention based on such knowledge has the following configuration.
That is, the radiation detector according to the present invention is a radiation detector provided with a detection layer sensitive to radiation on a substrate, wherein a polycrystalline film having an average grain size equal to or less than a pixel pitch is formed as the detection layer. It is what.

  [Operation / Effect] According to the radiation detector of the present invention, since a polycrystalline film having an average particle diameter equal to or smaller than the pixel pitch is formed as a detection layer, an image having good characteristics (spatial resolution, sensitivity, etc.) between pixels Can be obtained with a radiation detector. In addition, the temporal fluctuation can be reduced, and the detection characteristic regarding the response characteristic can be improved. As a result, detection characteristics can be improved.

  An example of the above-described polycrystalline film is CdTe (cadmium telluride), ZnTe (zinc telluride), or CdZnTe (cadmium zinc telluride). In addition, when the pixel pitch is 200 μm or less, it is possible to acquire an image (high-definition image) having a high spatial resolution of 200 μm or less. In addition, when the thickness of the detection layer is 300 μm or more, for example, it has a sufficient capture capability for X-rays with a tube voltage of several tens of kV or more frequently used in the medical diagnostic region, and has high sensitivity and quantum detection efficiency (DQE). Is obtained. When the average grain size is ½ or less of the pixel pitch, it is possible to reduce the situation where the crystal grains straddle between the pixels and to further improve the detection characteristics.

  In the method of manufacturing the radiation detector according to these inventions described above, a radiation detector having a large-area detection layer can be obtained by forming the detection layer by the proximity sublimation method. In the above-described method for manufacturing the radiation detector according to the invention, the polycrystalline film is CdTe, ZnTe, or CdZnTe, and the polycrystalline film is doped with 1 wtppm to 10 wtppm Cl (chlorine). Therefore, it is possible to stably manufacture a radiation detector that can efficiently suppress the particle size and obtain an image with good characteristics (spatial resolution, sensitivity, etc.). In addition, the unit of wtppm shows a mass part per million.

  According to the radiation detector and the method of manufacturing the same according to the present invention, since the polycrystalline film having an average particle size equal to or smaller than the pixel pitch is formed as the detection layer, the detection characteristics can be improved.

It is a longitudinal cross-sectional view which shows the structure of the radiation detector which concerns on an Example. It is a side view which shows schematic structure of a radiation imaging device. It is a circuit diagram which shows the structure of a switching matrix board | substrate and a peripheral circuit. It is a schematic diagram which shows the longitudinal cross-section of a radiation imaging device. It is a schematic diagram which shows the state of 1 process which forms a detection layer into the radiation detector which concerns on an Example. It is experimental data showing the relationship between crystal grain size and pixel variation in sensitivity. Experimental data representing a temporal change in the pressure of each component in the chamber when using only CdCl ₂ as a source. It is an experimental data showing the time change of the pressure for each component in the chamber when CdCl ₂ is used as a source and HCl is used as an additional source.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a configuration of a radiation detector according to the embodiment, FIG. 2 is a side view showing a schematic configuration of the radiation imaging apparatus, and FIG. 3 is a configuration of a switching matrix substrate and peripheral circuits. FIG. 4 is a schematic diagram showing a longitudinal section of the radiation imaging apparatus.

  The radiation detector 1 includes a supporting substrate 3 that is transparent to radiation, a common electrode 5 for bias charge application formed on the lower surface thereof, an electron injection blocking layer 7 on the lower surface of the common electrode 5, A detection layer 9 that generates electron-hole pair carriers in response to incident radiation, a hole injection blocking layer 11 formed on the lower surface of the detection layer 9, and a detection electrode 13 for collecting carriers are laminated. Prepared in state. However, if there is no problem in the characteristics of the radiation detector 1, either or both of the electron injection blocking layer 7 and the hole injection blocking layer 11 may be omitted.

The support substrate 3 described above, the small ones are preferred absorption coefficient of radiation, for example, glass, ceramic _{(Al 2 O 3, AlN)} , although materials such as silicon can be adopted, conductive, such as graphite substrate The common electrode can be omitted by using a material. In this embodiment, as shown in the figure, radiation is incident from the support substrate 3 side, and the operation is performed with a negative bias voltage applied to the common electrode 5.

  The detection layer 9 is preferably manufactured as described later, and is a polycrystalline film made of any one of CdTe (cadmium telluride), ZnTe (zinc telluride), CdZnTe (cadmium zinc telluride), or at least one of them. In addition, it is composed of polycrystalline stacked films 9a and 9b including one, and is further doped with Cl.

The common electrode 5 and the detection electrode 13 are made of a conductive material such as ITO, Au, or Pt, for example. Examples of the electron injection blocking layer 7 include Sb ₂ Te ₃ , Sb ₂ S ₃ , and ZnTe films that form p-type layers, and examples of the hole injection blocking layer 11 include CdS and ZnS films that form n-type layers. Etc. are exemplified.

  As shown in FIG. 2, the radiation detector 1 configured as described above is configured integrally with the switching matrix substrate 15 and functions as a radiation imaging apparatus. Thereby, the carriers generated in the detection layer 9 of the radiation detector 1 are collected for each element by the switching matrix substrate 15, accumulated for each element, and read out as an electric signal.

  As shown in FIG. 3, the switching matrix substrate 15 has a capacitor 17 as a charge storage capacitor and a thin film transistor 19 as a switching element corresponding to the detection element 1a in FIG. For convenience of explanation, FIG. 3 shows a 3 × 3 (pixel) matrix configuration, but in actuality, it has more pixels such as 1024 × 1024.

  The detailed structure of the switching matrix substrate 15 is as shown in FIG. That is, on the upper surface of the insulating substrate 21, the ground-side electrode 17 a of the capacitor 17, the connection-side electrode 17 b of the capacitor 17 via the insulating film 23 on the gate electrode 19 a of the thin-film transistor 19, and the source electrode 19 b of the thin-film transistor 19. The drain electrode 19c is laminated. Further, the upper surface is covered with a protective insulating film 25.

  Further, the connection side electrode 17b and the source electrode 19b are formed simultaneously and are electrically connected. As the insulating film 23 and the insulating film 25, for example, a plasma SiN film can be adopted. The radiation detector 1 and the switching matrix substrate 15 are aligned, and the detection electrode 13 and the connection-side electrode 17b of the capacitor 17 are aligned. For example, an anisotropic conductive film (ACF), an anisotropic conductive paste, etc. In a state of interposing between them, they are bonded by heating and pressure bonding. As a result, the radiation detector 1 and the switching matrix substrate 15 are bonded and integrated. At this time, the detection electrode 13 and the connection-side electrode 17b are electrically connected by the interposed conductor portion 27.

  Further, the switching matrix substrate 15 includes a read drive circuit 29 and a gate drive circuit 31. The read drive circuit 29 is connected to a vertical read wiring 30 that connects the drain electrodes 19 c of the thin film transistors 19 in the same column. The gate drive circuit 31 is connected to a horizontal readout wiring 32 that connects the gate electrodes 19a of the thin film transistors 19 in the same row. Although not shown, a preamplifier is connected to each readout wiring 30 in the readout drive circuit 29.

  Different from the above, a circuit in which the readout drive circuit 29 and the gate drive circuit 31 are integrated on the switching matrix substrate 15 is also used.

  Next, the detail of the manufacturing method of said radiation detector 1 is demonstrated with reference to FIG. FIG. 5 is a schematic diagram illustrating a state of one step of forming a detection layer on the radiation detector according to the example.

  The common electrode 5 of the radiation detector 1 is formed on one side of the support substrate 3 by a method such as sputtering or vapor deposition. This is not necessary when using a conductive material such as a graphite substrate. Next, the electron injection blocking layer 7 is laminated on the lower surface of the common electrode 5 by a method such as proximity sublimation, sputtering, or vapor deposition. Then, the detection layer 9 is formed on the lower surface of the electron injection blocking layer 7 by using, for example, the “proximity sublimation method” shown in FIG.

  Specifically, the support substrate 3 is placed in the vapor deposition chamber 33. Since the lower susceptor 35 for placing the source S is provided in the vapor deposition chamber 33, the support substrate 3 is placed with the vapor deposition surface facing downward via the spacer 37. Heaters 39 are provided at the upper and lower portions of the vapor deposition chamber 33. The vacuum pump 41 is operated to bring the inside of the vapor deposition chamber 33 into a reduced-pressure atmosphere, and then the source S is heated by the upper and lower heaters 39. Further, the gas is supplied into the vapor deposition chamber 33 from outside the vapor deposition chamber 33 while controlling the flow rate of a Cl-containing gas such as HCl (hydrogen chloride). As a result, while the source S is sublimated, Cl supplied from the outside is taken in, and a polycrystalline film of CdTe, ZnTe or CdZnTe doped with a desired amount (1 wtppm to 10 wtppm) of Cl adheres to the lower surface of the support substrate 3. Thus, the detection layer 9 is formed. Here, after the detection layer 9 is formed as a thick film having a thickness of about 600 μm, the surface is flattened by polishing or the like for integrated bonding to the switching matrix substrate 15 and finished to a thickness of about 400 μm.

As the source S to be set in the lower susceptor 35, Cd (cadmium) simple substance, Te (tellurium) simple substance, Zn (zinc) simple substance, CdTe (cadmium telluride), ZnTe (zinc telluride), CdZnTe (telluride) And a mixture of a first material containing at least one of cadmium zinc and a _second material containing at least one of CdCl ₂ (cadmium chloride) or ZnCl ₂ (zinc chloride). Further, the mixture is sintered in advance by heating in a normal pressure inert atmosphere before film formation.

For example, CdTe containing CdCl ₂ is first set as the source S and processed while supplying a Cl-containing gas from the outside, then the source S is replaced with ZnTe containing CdCl _2, and the same process is performed again. . As a result, a CdTe film containing Cl is formed on the first layer 9a of the detection layer 9, and a ZnTe film containing Cl is formed on the second layer 9b. Note that the detection layer 9 may be composed of only one layer.

After the detection layer 9 is formed, if necessary, CdCl ₂ and ZnCl ₂ are further filled in the lower susceptor 35 as a source S, and the surface of the detection layer 9 is additionally doped by heat treatment. . Specifically, the detection layer 9 is doped with Cl by performing a heat treatment in a state where a powder containing at least one of CdCl ₂ and ZnCl ₂ or a sintered body thereof is disposed to face each other.

The heat treatment atmosphere at this time preferably includes at least one of N ₂ , O ₂ , H ₂ , and a rare gas (He, Ne, Ar) maintained at 1 atm. In addition, the heat treatment atmosphere at this time includes at least one of N ₂ , O ₂ , H ₂ , and a rare gas (He, Ne, Ar) maintained at 1.3 × 10 ^{−4 to} 0.5 atm. preferable.

  In such an atmosphere, processing can be performed at a low temperature. Therefore, when Cl is additionally doped after the detection layer 9 is formed, the leakage current can be further reduced. Further, if the temperature is the same, more Cl can be supplied, and processing can be performed in a short time. Alternatively, the source may not be set on the lower susceptor 35, and Cl may be additionally doped by heating while supplying a gas containing Cl atoms to the detection layer 9. By additionally doping Cl in this way, the grain boundary is suitably protected.

  Next, a semiconductor layer for the hole injection blocking layer 11 is laminated on the surface of the detection layer 9 by electrodeposition, sputtering, vapor deposition, or the like. The hole injection blocking layer 11 is patterned and formed separately for each pixel as necessary. However, the patterning is unnecessary if the hole injection blocking layer 11 has a high resistance and there is no adverse effect such as a decrease in spatial resolution due to adjacent pixel leakage. Similarly, after the metal film for the detection electrode 13 is laminated and formed, the detection electrode 13 is formed by patterning. The radiation detector 1 is formed by the above process.

  Then, as described above, the switching matrix substrate 15 and the radiation detector 1 are integrated to complete the radiation imaging apparatus. As one method, conductive bump electrodes such as carbon are formed by screen printing on the pixel electrode (detection electrode 13 in this case) on the surface of either the switching matrix substrate 15 or the radiation detector 1, and both are pasted by a press machine. A method of joining together is possible. Alternatively, a conductive bump electrode may be formed at a location corresponding to the pixel without forming the pixel electrode, and the two may be bonded together.

  In the radiation detector 1 obtained by the above-described manufacturing method, an additional source (here, a Cl-containing gas of HCl) different from the source is doped from the initial stage to the end of film formation, so that the crystal grains are uniformized. The detection layer 9 is obtained. The detection layer 9 of this polycrystalline film is doped with 1 wtppm to 10 wtppm Cl.

<Comparison of experimental data>
The crystals obtained by the method of this example are confirmed by experiments. Comparison of experimental data will be described with reference to FIG. FIG. 6 is experimental data showing the relationship between crystal grain size and pixel variation in sensitivity.

  The CdZnTe film A is a film (average grain size <75 μm) in which Cl is positively doped (film Cl concentration 3.1 wtppm) and the crystal grains are refined by the method shown in this embodiment. The CdZnTe film B is a film having a coarse crystal grain (grain size: 200 μm to 300 μm) formed without intentionally doping conventional Cl (film Cl concentration: 0.5 wtppm). FIG. 6 shows each film characteristic (FIG. 6A is a sectional morphology, FIG. 6B is an XRD spectrum, and FIG. 6C is an input / output characteristic for each pixel).

  As is clear from the cross-sectional morphology of FIG. 6A, in the CdZnTe film A, it is confirmed that the crystal grains are made uniform by Cl and the average grain size is less than 75 μm. On the other hand, in the cross-sectional morphology of FIG. 6A, since Cl is not intentionally doped, Cl is supplied only to the substrate interface at the initial stage of film formation, and crystal grains near the interface and crystal grains other than the interface It is confirmed that the grain size of the crystal grains other than the interface is clearly large, and the grain size varies from 200 μm to 300 μm.

  As the CdTeZn film B grows, the crystal grain size grows as the film grows, and the XRD spectrum also shows a single orientation. Note that the (511) crystal plane has a twin relationship with the (111) crystal plane and does not exhibit multi-orientation. On the other hand, the CdTeZn film A maintains a fine grain size even when the film grows, and the XRD spectrum also shows typical multi-orientation.

  From the input / output characteristic data for each pixel, the radiation detector using the CdTeZn film B has a large sensitivity variation between pixels, whereas the radiation detector using the CdTeZn film A suppresses the sensitivity variation between pixels. It has been confirmed that a relatively uniform image is obtained (the image is not shown).

  In this embodiment, the pattern is formed on the switching matrix substrate 15 so that the pixel pitch is 200 μm. Therefore, as described in the above experimental data, when the detection layer 9 is doped with 3.1 wtppm of Cl, the average particle size is less than 75 μm, which is equal to or less than the pixel pitch of 200 μm, and further ½ of the pixel pitch of 200 μm. It becomes as follows.

  According to the radiation detector 1 described above, since a polycrystalline film having an average particle size equal to or smaller than the pixel pitch is formed as a detection layer, an image with good characteristics (spatial resolution, sensitivity, etc.) between the pixels is displayed on the radiation detector 1. Can be obtained. In addition, the temporal fluctuation can be reduced, and the detection characteristic regarding the response characteristic can be improved. As a result, detection characteristics can be improved.

  In this embodiment, the polycrystalline film is CdTe (cadmium telluride), ZnTe (zinc telluride) or CdZnTe (cadmium zinc telluride). In addition, when the pixel pitch is 200 μm or less, it is possible to acquire an image (high-definition image) having a high spatial resolution of 200 μm or less. Further, when the thickness of the detection layer 9 is 300 μm or more, for example, it has a sufficient capturing ability for X-rays with a tube voltage of several tens of kV or more frequently used in the medical diagnostic region, and has high sensitivity / quantum detection efficiency (DQE). ) Is obtained. Further, when the average grain size is ½ or less of the pixel pitch as in this embodiment, it is possible to reduce the situation where the crystal grains straddle between the pixels, and to further improve the detection characteristics.

  In this embodiment, since the detection layer 9 is formed by the proximity sublimation method, the radiation detector 1 having the detection layer 9 having a large area can be obtained. As described above, the polycrystalline film is CdTe, ZnTe, or CdZnTe. By doping this polycrystalline film with 1 wtppm to 10 wtppm Cl (chlorine), the grain size can be efficiently suppressed, and the characteristics ( A radiation detector capable of obtaining an image having a good spatial resolution, sensitivity, etc.) can be stably produced.

<About the source made of the first material and the second material and the additional source>
By the way, in manufacturing the radiation detector 1 of the present embodiment, Cd (cadmium) alone, Te (tellurium) alone, Zn (zinc) alone, CdTe (cadmium telluride), ZnTe (zinc telluride). Then, a first material containing at least one of CdZnTe (cadmium zinc telluride) is used as a source, and a polycrystalline film or a polycrystalline laminated film is formed by vapor deposition or sublimation (this is also referred to as “first process”) ), During the start of the first process or in the middle of the process, an additional source (in this case, a Cl-containing gas of HCl) made of Cl (chlorine) alone or a Cl compound different from the source is supplied (this is referred to as “the first process”). Also referred to as “two processes”), a polycrystalline film or a polycrystalline laminated film is grown by heating. More preferably, as in the present embodiment, the source used in the first process described above includes a first material described above and at least one of CdCl ₂ (cadmium chloride) and ZnCl ₂ (zinc chloride). In the first process, a polycrystalline film or a multilayer film of a polycrystalline film is formed by vapor deposition or sublimation using a source made of a mixture of the first material and the second material. doing.

There is a reason why the additional source made of Cl alone or a Cl compound is separately supplied in this way. That is, in the conventional Cl doping method of Patent Document 2 described above, Cl compounds such as CdCl ₂ and ZnCl ₂ are consumed earlier at a lower melting point and higher vapor pressure than CdTe, ZnTe, and CdZnTe. Therefore, chlorine (Cl) is not supplied during the film formation, and the problem that Cl can be doped only in the vicinity of the substrate interface at the initial stage of film formation has been clarified.

  In the vicinity of the substrate interface doped with Cl, it has been confirmed that the crystal grains are small as shown in FIG. 6, and the crystal grains are large in a portion where Cl is not doped, so that the crystal grains cannot be made uniform. . If the crystal grains cannot be made uniform, uniform characteristics (for example, leakage current and sensitivity) cannot be obtained in each pixel, and temporal fluctuations also increase. These become noise sources, making sensitivity correction difficult and deteriorating image characteristics (detection efficiency).

  Therefore, it has been proposed that after forming a polycrystalline film or a polycrystalline laminated film by vapor deposition or sublimation with the above-mentioned source as in claim 3 of the above-mentioned Patent Document 2, additional doping with Cl is proposed. However, in this case, the crystal grains can be protected by additional doping with Cl, but the grain size that has grown greatly cannot be reduced, and the crystal grains cannot be made uniform.

In view of the fact that Cl is not supplied during film formation, a second material typified by CdCl ₂ (cadmium chloride) and ZnCl ₂ (zinc chloride) is used so that Cl is supplied until the end of the film formation process. It is also possible to increase the ratio. However, no matter how much the ratio of the second material is increased, the experimental data in FIG. 7 reveals that the second material disappears first during the film formation.

Figure 7 shows experimental data showing temporal changes in pressure for each component in the chamber when using only CdCl ₂ as the source, FIG. 8, HCl as a further additional source with CdCl ₂ as a source It is the experimental data showing the time change of the pressure for each component in a chamber when using.

In this experimental data, when a polycrystalline film or a polycrystalline laminated film is formed by proximity sublimation using only the source as shown in FIG. 7, among the components in the chamber, HCl (hydrogen chloride) components (Cl, H _2). ) Goes down over time. On the other hand, when HCl is supplied as an additional source as a Cl compound different from the source as shown in FIG. 8, it can be seen that among the components in the chamber, the HCl component does not decrease over time.

  For this reason, an additional source (here, Cl-containing gas of HCl) different from the source made of the first material is supplied at the start of the first process or during the process (second process). Since the additional source contains Cl, Cl is continuously supplied from the start of the first process or from the middle to the end of the process. Therefore, CdTe, ZnTe, or CdZnTe can be uniformly doped with Cl in the thickness direction from the start of the first film formation process or from the middle to the end of the film formation process (detection layer 9). . And the radiation detector 1 with favorable radiation detection characteristics (sensitivity, response characteristics, etc.) can be manufactured while keeping the leakage current low. As a result, the crystal grains can be made uniform and the detection characteristics can be made uniform.

In this embodiment, the source used in the first process is a mixture of the first material described above and a second material containing at least one of CdCl ₂ (cadmium chloride) and ZnCl ₂ (zinc chloride). In the first process, a polycrystalline film or a polycrystalline laminated film is formed by vapor deposition or sublimation using a source made of a mixture of the first material and the second material. In this case, since the source made of the mixture of the first material and the second material contains Cl, the detection layer formed of a polycrystalline film or a polycrystalline laminated film by vapor deposition or sublimation. Is formed in the first process, Cl is simultaneously contained in the detection layer. Even if Cl is not supplied from the source during the first process, an additional source (Cl-containing gas of HCl) different from the source is supplied during the start of the first process or during the process. Therefore, CdTe, ZnTe, or CdZnTe can be uniformly doped with Cl in the thickness direction from the beginning to the end of film formation. A radiation detector having good radiation detection characteristics (sensitivity, response characteristics, etc.) can be manufactured while keeping the leakage current low. As a result, the crystal grains can be made uniform and the detection characteristics can be made uniform.

  The second process may be performed by supplying the additional source simultaneously with the start of the first process, or the second process may be performed by supplying the additional source in the middle of the first process. The second process may be carried out by supplying an additional source at a point in time or slightly before the point in time when Cl is not supplied during film formation.

The source S is at least one of Cd (cadmium), Te (tellurium), Zn (zinc), CdTe (cadmium telluride), ZnTe (zinc telluride), and CdZnTe (cadmium zinc telluride). A mixture of a first material containing one and a second material containing at least one of CdCl ₂ (cadmium chloride) and ZnCl ₂ (zinc chloride). Only the material may be used as the source S. In this case, by supplying Cl or a Cl compound as an additional source, the same effect as in the embodiment can be obtained.

  Further, as described in the experimental data of FIGS. 7 and 8, when HCl is supplied as an additional source as a Cl compound different from the source, among the components in the chamber, the HCl component has elapsed over time. It does n’t go down. Therefore, it is confirmed from the experimental data in FIG. 8 that Cl is continuously supplied by the additional source without being consumed in the chamber during film formation.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In the embodiment described above, the radiation to be detected is not particularly limited as exemplified by X-rays, γ-rays, light, and the like.

  (2) It is not limited to the manufacturing method of the Example mentioned above.

DESCRIPTION OF SYMBOLS 1 ... Radiation detector 3 ... Support substrate 9 ... Detection layer

Claims (7)

A radiation detector provided on a substrate with a detection layer sensitive to radiation,
A radiation detector characterized in that a polycrystalline film having an average particle diameter equal to or smaller than a pixel pitch is formed as the detection layer. The radiation detector according to claim 1.
The radiation detector, wherein the polycrystalline film is CdTe (cadmium telluride), ZnTe (zinc telluride) or CdZnTe (cadmium zinc telluride). The radiation detector according to claim 1 or 2,
The radiation detector according to claim 1, wherein the pixel pitch is 200 μm or less. The radiation detector according to any one of claims 1 to 3,
The radiation detector is characterized in that the thickness of the detection layer is 300 μm or more. The radiation detector according to any one of claims 1 to 4,
A radiation detector, wherein a polycrystalline film having an average grain size of 1/2 or less of the pixel pitch is formed as the detection layer. A method for manufacturing the radiation detector according to any one of claims 1 to 5,
A method of manufacturing a radiation detector, wherein the detection layer is formed by proximity sublimation. A method for manufacturing the radiation detector according to any one of claims 1 to 5,
The polycrystalline film is CdTe (cadmium telluride), ZnTe (zinc telluride) or CdZnTe (cadmium zinc telluride),
A method of manufacturing a radiation detector, wherein the polycrystalline film is doped with 1 wtppm to 10 wtppm of Cl (chlorine).