WO2010092869A1 - Radiation detector and method for manufacturing radiation detector - Google Patents

Radiation detector and method for manufacturing radiation detector Download PDF

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Publication number
WO2010092869A1
WO2010092869A1 PCT/JP2010/050952 JP2010050952W WO2010092869A1 WO 2010092869 A1 WO2010092869 A1 WO 2010092869A1 JP 2010050952 W JP2010050952 W JP 2010050952W WO 2010092869 A1 WO2010092869 A1 WO 2010092869A1
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Prior art keywords
scintillator
radiation detector
base material
elements
metal
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PCT/JP2010/050952
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French (fr)
Japanese (ja)
Inventor
長友浩之
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日立金属株式会社
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Priority to JP2010550485A priority Critical patent/JP5170263B2/en
Publication of WO2010092869A1 publication Critical patent/WO2010092869A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/2006—Measuring radiation intensity with scintillation detectors using a combination of a scintillator and photodetector which measures the means radiation intensity

Definitions

  • the present invention relates to a radiation detector used in a computed tomography (CT) apparatus that handles radiation such as X-rays, ⁇ -rays, ⁇ -rays, and ⁇ -rays, and in particular, a high-resolution X-ray CT apparatus that uses a scintillator element.
  • CT computed tomography
  • the present invention relates to a radiation detector.
  • a radiation CT apparatus includes a radiation source (for example, an X-ray tube) and a radiation detector arranged symmetrically with respect to an object to be imaged, and measures the radiation intensity at each detection position to measure the inside of the object to be imaged. It is configured to observe the structure.
  • a radiation source for example, an X-ray tube
  • a radiation detector arranged symmetrically with respect to an object to be imaged, and measures the radiation intensity at each detection position to measure the inside of the object to be imaged. It is configured to observe the structure.
  • the basic structure of the radiation detector is one in which a scintillator element is arranged on a plurality of arranged semiconductor photodetecting elements, and the scintillator element opens to the radiation source side to receive radiation such as X-rays.
  • the scintillator element is generally made of a material such as CdWO 4 , Bi 4 Ge 3 O 12 , or Gd 2 O 2 S processed into a columnar shape, and a plurality of scintillator elements are two-dimensionally arranged with an interval between adjacent elements. ing.
  • the scintillator element When radiation is incident on the opening surface of the scintillator element, the scintillator element itself emits light to emit visible light, and the semiconductor light detecting element disposed on the opposite surface of the opening surface receives the light and outputs an electrical signal.
  • the scintillator element of the radiation detector is designed so as to be as small as possible and the distance between adjacent elements is narrowed to improve the resolution and resolution.
  • Patent Document 1 discloses an example in which a scintillator element is coated with a white paint (light reflecting material) in which a powder such as titanium oxide is kneaded with an epoxy resin or the like.
  • Patent Document 2 discloses a metal reflection such as Au, Ag, Al, Ni, etc. on the surface of the scintillator element by a method such as sputtering or CVD (chemical vapor deposition). An example of covering the material is disclosed.
  • Patent Document 3 discloses an example in which a sintered body of metal particles is used as a reflector.
  • a metal reflector is obtained by sintering a coating material in which metal fine particles having a particle size of 1 ⁇ m or less, preferably 0.1 ⁇ m or less are dispersed in a solvent.
  • the radiation detector using the scintillator element has been improved to have a small opening area of the scintillator element and a narrow interval between adjacent elements.
  • an interval between adjacent scintillator elements is required to be 100 ⁇ m or less.
  • the production of a radiation detector in which scintillator elements are arranged at such a narrow interval has the following problems in the prior art.
  • Patent Document 1 a gap between adjacent scintillator elements is filled with a white paint obtained by kneading a powder of titanium oxide or the like with an epoxy resin or the like as a reflector.
  • a white paint obtained by kneading a powder of titanium oxide or the like with an epoxy resin or the like as a reflector.
  • the visible light emitted from the scintillator element is reflected by the titanium oxide powder in the white paint and guided to the semiconductor photodetector element.
  • the white paint to be filled becomes thin, and part of the visible light emitted by the scintillator elements is not reflected by the titanium oxide powder, but passes through the white paint and adjoins. It will enter the scintillator element. This phenomenon is called crosstalk, and causes a reduction in the resolution and resolution of the radiation detector.
  • FIG. 8 shows the relationship between the thickness of the reflective material and the light transmittance of light having a wavelength of 500 nm in a white paint kneaded with titanium oxide powder and an epoxy resin.
  • the white paint which is a reflective material
  • the light transmittance tends to increase.
  • the thickness is 100 ⁇ m or less
  • the increase in light transmittance is remarkable. With such light transmittance, the occurrence of crosstalk is inevitable in the radiation detector.
  • the reflective material is metal
  • the thickness is approximately 0.1 ⁇ m or more, total reflection is possible without transmitting visible light. Therefore, if metal is used for the reflective material that covers the scintillator elements, crosstalk can be avoided even if the interval between adjacent scintillator elements is narrow.
  • FIG. 9 shows an Ag film thickness distribution in the groove depth direction when an Ag film is formed in a groove having a width of 100 ⁇ m and a depth of 1.7 mm by sputtering.
  • the film is formed so that the Ag film thickness at the top of the groove is 1 ⁇ m.
  • the film thickness of Ag formed on the side surface of the groove is reduced in proportion to the groove depth, and the depth from the surface is reduced.
  • the thickness is 0.2 mm or more, the Ag film is not formed on the side surface of the groove. Therefore, with the method as shown in FIG. 9, it is not possible to form a reflector in the gap between adjacent scintillator elements.
  • a method of forming a metal reflector on the side surface of a groove having a high aspect ratio a method of forming a metal film by applying and sintering a solution containing metal fine particles as disclosed in Patent Document 3 is considered. It is done. However, in this method, since the film structure becomes rough reflecting the particle size of the metal fine particles, light cannot be scattered and high light reflectance cannot be obtained.
  • FIG. 10 shows the reflection characteristics of an Ag film obtained by applying a solution in which Ag fine particles having an average particle diameter of 25 nm are dispersed to the surface of the scintillator element and sintering it.
  • a light reflectance of 50% or less can be obtained in the entire visible light region with a wavelength of 400 nm to 900 nm.
  • a solution containing metal fine particles becomes a very expensive solution because a step of producing metal fine particles and dispersing them in a solvent is required. Therefore, when a solution containing fine metal particles is used, there is a problem that the manufacturing cost of the radiation detector is increased.
  • the present invention solves the above problems, and provides a radiation detector and a method for manufacturing the same, in which crosstalk is small even when the interval between adjacent scintillator elements is narrow.
  • a plurality of scintillator elements are arrayed on a semiconductor photodetector element array in which a plurality of semiconductor photodetector elements are arranged in a matrix so that the bottom faces the semiconductor photodetector elements.
  • a radiation detector provided with a light reflecting material on a surface other than the bottom surface of the scintillator element,
  • the scintillator elements are arranged adjacent to each other with an interval of 100 ⁇ m or less, and the light reflecting material is formed by sequentially forming a base material and a metal reflecting material.
  • the base material may be a base material containing an inorganic oxide.
  • the inorganic oxide may include silicon oxide.
  • the inorganic oxide film may contain titanium oxide.
  • the inorganic oxide containing silicon oxide may be a fired product of SOG (Spin On Glass).
  • the inorganic oxide containing titanium oxide may be a fired product of a titanium oxide precursor.
  • the metal reflector may be a fired product of an organometallic compound containing at least one of Ag, Au, Al, and Ni.
  • a step of forming a processing groove having a grid shape of 100 ⁇ m or less on one side of a scintillator substrate, and an inorganic oxide base material and a metal reflecting material are sequentially formed on the side of the processing groove.
  • the inorganic oxide precursor solution is filled in the processed groove by one of a dip coating method, a screen printing method, a spin coating method, and a dispensing method and baked to form the base material. Also good. Further, the viscosity of the inorganic oxide precursor solution may be 20 cP (0.020 Pa ⁇ s) or less.
  • the metal reflector may be formed by filling the groove and firing.
  • the viscosity of the organometallic compound solution may be 20 cP (0.020 Pa ⁇ s) or less.
  • the radiation detector of the present invention can be used as a radiation detector for a high-resolution X-ray CT apparatus with high resolution and resolution.
  • FIG. 1 is a perspective view showing the radiation detector of the present embodiment.
  • a scintillator array 3 is attached to a semiconductor photodetector element array 2 via an adhesive layer 4.
  • the semiconductor photodetecting element array 2 has a plurality of semiconductor photodetecting elements 21 arranged on a flat plate.
  • N pieces are arranged in a row direction and M pieces are arranged in a column direction.
  • the arrangement method is not limited to this.
  • the scintillator array 3 includes scintillator elements 31 processed into a columnar shape. In this scintillator array 3, each scintillator element 31 is aligned so that its bottom surface coincides with the surface of the corresponding semiconductor photodetecting element 21, and is attached via an adhesive layer 4.
  • the scintillator element 31 for example, a ceramic scintillator material such as CdWO 4 , Bi 4 Ge 3 O 12 , Gd 2 O 2 S or the like can be used, and the adhesive layer 4 is an optical adhesive having a high light transmittance, such as Epoxy Technologies. Epo-Tek301 (trademark) manufactured by KK is used.
  • Epo-Tek301 (trademark) manufactured by KK is used.
  • a reflecting material that reflects visible light emitted from the scintillator element 31 is formed on the side surface and the upper surface of the scintillator element 31 (opposite surface opposite to the surface facing the semiconductor light detection element 31). Has been.
  • FIG. 2 is an enlarged schematic view of the cross section of the radiation detector 1 shown in FIG.
  • a base material 32 and a metal reflector 33 are sequentially formed on the side surface of the scintillator element 31, and the scintillator element 31 is attached to the corresponding semiconductor photodetecting element 21 through the adhesive layer 4.
  • the base material 32 is formed to a thickness of 10 nm to 10 ⁇ m using an inorganic oxide material having high light transmittance at the emission wavelength of the scintillator element 31 such as silicon oxide or titanium oxide.
  • the metal reflector 33 is made of a material containing at least one of Ag, Au, Al, and Ni and having a high light reflectivity at the emission wavelength of the scintillator element 31 to a thickness of 0.1 ⁇ m to 10 ⁇ m.
  • a protective material such as silicon oxide may be further coated on the metal reflector 33.
  • the filler 34 may be filled in the gap between the adjacent scintillator elements 31.
  • a resin such as an epoxy resin, an ultraviolet curable resin, or a polyimide resin can be used.
  • these resins are filled with a mixture of heavy metal powders such as tungsten and molybdenum, the radiation shielding effect between the scintillator elements 31 can be enhanced, and the occurrence of crosstalk can be further prevented.
  • An upper surface reflecting material 35 is formed on the surface of the scintillator element 31 opposite to the surface facing the semiconductor light detection element 21.
  • the upper surface reflecting material 35 may be formed by sequentially forming a base material 32 and a metal reflecting material 33, or titanium oxide powder or the like used as a reflecting material in a conventional radiation detector is epoxy. A white paint kneaded with a resin may be used.
  • step 1 grooves are formed in a lattice pattern at a substantially constant pitch on a Gd 2 O 2 S scintillator substrate 5 processed to a desired size (FIG. 3A).
  • step 2 the grooved scintillator substrate 5 is dipped in the SOG solution 6 of HSG-R7-13 manufactured by Hitachi Chemical Co., Ltd., and the SOG solution 6 is filled into the groove formed in the scintillator substrate 5.
  • filling may be performed using a method such as a screen printing method, a spin coating method, or a dispensing method.
  • a pretreatment for improving wettability such as HMDS (hexamethyldisilazane) treatment or oxygen plasma irradiation is performed before filling the groove with the SOG liquid 6. You can do it. Furthermore, when the SOG liquid 6 in the groove is excessive, the SOG liquid 6 is shaken off using centrifugal force, or the SOG liquid 6 is sucked off with a non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott). The SOG liquid 6 may be removed.
  • HMDS hexamethyldisilazane
  • the viscosity of the SOG liquid 6 is considered to be experimentally appropriate. It is preferable to prepare. In the present embodiment, an example in which the SOG liquid 6 having a viscosity of 15 cP (0.015 Pa ⁇ s) is used will be described.
  • step 3 the SOG liquid 6 is baked to form a base material 32 containing silicon oxide.
  • An electric furnace is used for firing, the temperature is raised from room temperature, and the temperature is kept at a predetermined temperature for a predetermined time.
  • the oxygen concentration during firing is sufficiently reduced, for example, 1000 ppm or less.
  • the base material 32 containing silicon oxide is formed on the groove processing surface, and the surface roughness of the groove processing surface is reduced.
  • the substrate is baked at 400 ° C. for 30 minutes, the thickness of the base material 32 on the grooved surface is 0.1 to 2 ⁇ m, and the surface roughness Ra of the grooved surface is 500 nm or less. (FIG. 3C) was obtained.
  • the SOG liquid 6 is filled in the groove of the scintillator substrate 5 and baked to form the base material 32 containing silicon oxide.
  • a base material containing another inorganic oxide may be formed.
  • the base material 32 containing titanium oxide may be formed by filling a precursor liquid of titanium oxide into the groove of the scintillator substrate 5 and baking it. Even when another oxide precursor liquid is used, the viscosity of the liquid is preferably 20 cP (0.020 Pa ⁇ s) or less from the viewpoint of easy filling into the grooves.
  • the metal is less likely to segregate from the organometallic compound liquid 7 on the base material 32 in the next step, and a uniform metal reflector 33 can be obtained.
  • This effect is considered to be because the base material 32 containing an inorganic oxide hardly reacts with the organic solvent contained in the organic compound liquid 7, and the starting point for segregation of the metal hardly occurs.
  • step 4 the scintillator substrate 5 on which the base material 32 is formed is immersed in the organometallic compound solution 7, and the organometallic compound solution 7 is filled in the grooves of the scintillator substrate 5.
  • the organometallic compound solution 7 Nano Dotite XA-9069 manufactured by Fujikura Kasei Co., Ltd., which is an organic silver compound solution, is used (FIG. 3 (d)).
  • the organometallic compound liquid 7 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by using other methods such as a screen printing method, a spin coating method, and a dispensing method. good. Furthermore, when the organometallic compound liquid 7 in the groove is excessive, the organometallic compound liquid 7 is shaken off using centrifugal force, or the non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott) is used. The excess organometallic compound liquid 7 may be removed by sucking off the liquid.
  • the organometallic compound liquid 7 When the viscosity of the organometallic compound liquid 7 is increased, bubbles are likely to be entrained when filling the grooves, and uniform filling becomes difficult. 6 is preferably prepared.
  • the organometallic compound liquid 7 having a viscosity of 15 cP (0.015 Pa ⁇ s) is used.
  • the metal reflecting material 33 containing Ag is formed by baking the organometallic compound 7.
  • a hot plate is used and held at a predetermined temperature (for example, 150 ° C.) for a predetermined time (for example, 30 minutes).
  • the organometallic compound 7 before firing is colorless and transparent, but when Ag particles are deposited during firing, the color changes to brown, and then the Ag particles are bonded together to form a silver continuous film.
  • the thickness of the metal reflecting material 33 in the groove containing this Ag is 0.1 to several ⁇ m (FIG. 3E).
  • the metal metal compound liquid 7 is filled in the groove of the scintillator substrate 5 and fired to form the metal reflector 33 containing Ag.
  • a metal fine particle paste containing Ag, Au, Al, Ni, etc., which has a relatively high light reflectance with respect to visible light is filled in the groove of the scintillator substrate 5 and fired to obtain a fired metal fine particle.
  • the metal reflector 33 containing may be formed. Even when such a metal fine particle paste is used, the viscosity of the paste is preferably 20 cP (0.020 Pa ⁇ s) or less because of easy filling into the grooves.
  • step 6 the filler 34 is filled into the grooves of the scintillator substrate 5.
  • an epoxy resin mixed with a curing agent is used as the filler 34 and the grooves of the scintillator substrate 5 are filled by screen printing.
  • it may replace with the example which fills an epoxy resin using a screen printing method, and may use other filling methods, such as a dispensing method.
  • the epoxy resin is filled in a reduced-pressure atmosphere so that no bubbles remain inside the epoxy resin. Then, this epoxy resin is heated and cured for a predetermined time in an electric oven set at a predetermined temperature (FIG. 3 (f)).
  • step 7 the surface of the scintillator substrate 5 is ground.
  • the substrate surface grooved surface
  • the upper surface reflecting material 35 is formed.
  • the upper surface reflecting material 35 is made of epoxy resin mixed with a curing agent and further mixed with titanium oxide powder to form a white paint, and screen printing is performed on the surface (grooved surface) of the scintillator substrate 5. It will be applied by the method.
  • other application methods such as a dispensing method may be used.
  • the white paint is heated and cured for a predetermined time in an electric oven set at a predetermined temperature (FIG. 3 (h)).
  • a white paint in which an epoxy resin and titanium oxide powder are kneaded is used as the upper surface reflecting material 35.
  • white powder that reflects visible light emitted by the scintillator element 31, such as silicon oxide or A white paint using aluminum oxide powder or titanium oxide powder coated with silicon oxide may be used.
  • the base material and the metal reflecting material may be formed in order under the same conditions as in Steps 2 to 6 without using the white paint.
  • step 9 the back surface of the scintillator substrate 5 (the surface opposite to the groove processing surface) is ground to remove the base material 32, the metal reflector 33, and the filler 34 attached to the back surface of the scintillator substrate 5.
  • the scintillator substrate 5 is separated into a plurality of columnar scintillator elements 31, and the scintillator array 3 is formed (FIG. 3 (i)).
  • step 10 alignment is performed so that the plurality of scintillator elements 31 and the plurality of semiconductor light detection elements 21 face each other, and the opposite surface of the upper surface reflecting material 35 of the scintillator array 3 and the semiconductor light detection element array 2.
  • the surface is bonded through an adhesive layer 4.
  • the adhesive layer 4 is bonded to the scintillator array 3 and the semiconductor photodetecting element array 2 by using an optical adhesive and heating the adhesive layer 4 for a predetermined time in an electric furnace set at a predetermined temperature.
  • the radiation detector 1 of the present embodiment is completed (FIG. 3 (j)).
  • the interval between adjacent scintillator elements 31 is set to 100 ⁇ m or less.
  • step 1 a Gd 2 O 2 S scintillator substrate 5 machined to a width of 73 mm, a height of 22 mm, and a thickness of 2.0 mm is machined to form grooves having a width of 80 ⁇ m and a depth of 1.7 mm at a pitch of 1 mm. (FIG. 3A).
  • step 2 the grooved scintillator substrate 5 is dipped in the SOG solution 6 of HSG-R7-13 manufactured by Hitachi Chemical Co., Ltd., and the SOG solution 6 is filled into the groove formed in the scintillator substrate 5.
  • FIG. 3B the SOG solution 6 of HSG-R7-13 manufactured by Hitachi Chemical Co., Ltd.
  • the SOG liquid 6 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by a method such as a screen printing method, a spin coating method, or a dispensing method.
  • a pretreatment for improving wettability such as HMDS (hexamethyldisilazane) treatment or oxygen plasma irradiation is performed before filling the groove with the SOG liquid 6. You can do it. Furthermore, when the SOG liquid 6 in the groove is excessive, the SOG liquid 6 is shaken off using centrifugal force, or the SOG liquid 6 is sucked with a non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott). Excess SOG liquid 6 may be removed.
  • HMDS hexamethyldisilazane
  • the viscosity of the SOG liquid 6 When the viscosity of the SOG liquid 6 is increased, bubbles are likely to be involved when filling the groove, and uniform filling becomes difficult. As a result of making and studying SOG liquids 6 having various viscosities, the present inventor has found that if the viscosity of the SOG liquid 6 is 20 cP (0.020 Pa ⁇ s) or less, it can be uniformly filled without entraining bubbles. In this example, the SOG liquid 6 having a viscosity of 15 cP (0.015 Pa ⁇ s) was used with sufficient margin.
  • step 3 the SOG liquid 6 was baked to form a base material 32 containing silicon oxide.
  • An electric furnace was used for firing, and the temperature was raised from room temperature and held at 400 ° C. for 30 minutes.
  • the oxygen concentration during firing was set to 1000 ppm or less.
  • a base material 32 containing silicon oxide was formed on the groove processing surface, and the surface roughness of the groove processing surface was alleviated.
  • the thickness of the base material 32 on the groove processed surface was 0.1 to 2 ⁇ m, and the surface roughness Ra of the groove processed surface was 500 nm or less (FIG. 3C).
  • the surface roughness Ra is measured by using an atomic force microscope, that is, an AFM (Digital Instruments, Nano Scope III), and the surface of the groove processing surface in the region of 5 ⁇ m square (5 mm ⁇ 5 mm) in the tapping mode and the probe. The distance was measured, and the difference in the irregularities on the surface of the grooved surface was calculated.
  • the SOG liquid 6 is filled in the groove of the scintillator substrate 5 and baked to form the base material 32 containing silicon oxide.
  • the base material 32 containing titanium oxide may be formed by filling a precursor liquid of titanium oxide into the groove of the scintillator substrate 5 and baking it. Even when another oxide precursor liquid is used, the viscosity of the liquid is preferably 20 cP (0.020 Pa ⁇ s) or less from the viewpoint of easy filling into the grooves.
  • the base material 32 containing an inorganic oxide By setting it as the base material 32 containing an inorganic oxide, in the next process, it is hard to segregate a metal from the organometallic compound liquid 7 on the base material 32, and it can be set as the uniform metal reflector 33. This effect is considered to be because the base material 32 containing an inorganic oxide hardly reacts with the organic solvent contained in the organic compound liquid 7, and the starting point for segregation of the metal hardly occurs.
  • the base material 32 is selected from those that are not dissolved by the organometallic compound liquid described below.
  • the base material 32 containing silicon oxide or other inorganic oxide is formed by using a material such as SOG liquid 6 containing silicon dioxide or other inorganic oxide without containing silicone resin. To do.
  • step 4 the scintillator substrate 5 on which the base material 32 was formed was immersed in the organometallic compound solution 7, and the organometallic compound solution 7 was filled in the grooves of the scintillator substrate 5.
  • an organic silver compound solution manufactured by Fujikura Kasei Co., Ltd., Nano-Dotite XA-9069 was used as the organometallic compound solution 7 (FIG. 3 (d)).
  • the organometallic compound liquid 7 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by a method such as a screen printing method, a spin coating method, or a dispensing method. Furthermore, when the organometallic compound liquid 7 in the groove is excessive, the organometallic compound liquid 7 is shaken off using centrifugal force, or the non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott) is used. The excess organometallic compound liquid 7 may be removed by sucking off the liquid.
  • organometallic compound liquid 7 When the viscosity of the organometallic compound liquid 7 is increased, bubbles are easily involved when filling the groove, and uniform filling becomes difficult.
  • the inventor of the present application made organometallic compound liquids 7 having various viscosities, and as a result of repeated examination, as long as the viscosity of the organometallic compound liquid 7 is 20 cP (0.020 Pa ⁇ s) or less, it is uniform without entraining bubbles. In this example, the organometallic compound liquid 7 having a viscosity of 15 cP (0.015 Pa ⁇ s) was used with a sufficient margin.
  • step 5 the organometallic compound 7 was fired to form a metal reflector 33 made of Ag.
  • a hot plate was used and held at 150 ° C. for 30 minutes.
  • the organometallic compound 7 before firing was colorless and transparent, but when the Ag particles were precipitated during firing, the color turned brown, and then the Ag particles were combined to form a silver continuous film.
  • the thickness of the metal reflector 33 in the groove made of Ag was 0.1 to several ⁇ m (FIG. 3E).
  • FIG. 4 is an SEM image of the surface of the metal reflector 33 after firing
  • FIG. 11 is an image obtained by adjusting the contrast of FIG. 4 to make the grain noticeable.
  • a continuous Ag microstructure as shown in FIG. 4 (or FIG. 11) was formed by thermal decomposition of organic silver.
  • the light reflectance and light transmittance on the surface of the metal reflector 33 were measured at a wavelength of 500 nm, the light reflectance was 95.26% and the light transmittance was 0%.
  • the metal reflector 33 used in the radiation detector 1 It was confirmed that the light reflection characteristics were sufficient.
  • the ability to confine the visible light emitted by the scintillator element is improved, and the visible light emitted by the scintillator element is efficiently guided to the semiconductor photodetector element.
  • the output of the radiation detector can be increased.
  • Example 2 Next, examples in which the firing temperature in step 5 is varied will be described.
  • the metal reflector 33 is obtained by holding for 30 minutes on a hot plate set at a plurality of different firing temperatures. Then, 5 lines having a length of 2 microns are drawn from the SEM image of the metal reflector 33 at each firing temperature, and the average number is obtained by counting the number of Ag grains on the line, and 2 microns is divided by the average number. The results of calculating the particle size are shown below. 140 ° C firing: (Cannot be counted in a continuous film state)
  • 150 degreeC baking 38.4 counts, average particle diameter 52nm.
  • 160 degreeC baking 25.6 counts, average particle diameter 78nm.
  • the reflectance decreases as the area of the recesses formed between the Ag grains increases, but it has been found from experiments that the recesses tend to be conspicuous when the average particle size is 100 nm or more. Therefore, the reflectance characteristics as described above are achieved when the average particle size is less than 100 nm. Further, it has been confirmed that when the particle size of the structure of the metal reflective film is about 1/10 or less of the light wavelength of 500 nm, scattering is further suppressed and it contributes to an improvement in reflectance. Therefore, more preferable reflectance characteristics are achieved when the average particle diameter is less than 60 nm. Moreover, it is also preferable that the tissue is joined to form an integrated Ag film.
  • the firing temperature in step 5 is preferably 140 ° C. and 200 ° C. or less, more preferably 140 ° C. and less than 160 ° C., for example, about 150 ° C. Is preferred.
  • FIG. 5 is an SEM image of the surface of the metal reflector 33 obtained by firing the organometallic compound 7 by holding it on a hot plate at 250 ° C. for 30 minutes, and FIG. 12 is adjusted for contrast so that the granularity in FIG. 5 is conspicuous. Is.
  • the Ag microstructure became large and irregular in comparison with FIG. 4 (or FIG. 11).
  • grains has also increased.
  • the light transmittance and light transmittance on the surface of the metal reflector 33 were measured at a wavelength of 500 nm, the light transmittance was 0%, but the light reflectance was 92.54%. It was confirmed that the light reflectivity of the reflecting material 33 was lowered.
  • the SEM image of FIG. 4, 5 (or FIG. 11, 12) was observed with the sample for a measurement produced on the same conditions. That is, in the configuration of FIG. 2, force was continuously applied along the surface of the metal reflector 33, the base material 32 was cleaved, and the exposed surface was observed with an SEM to obtain a fine microstructure photograph of Ag. Is.
  • FIG. 6 shows the relationship between the light reflectance of the metal reflector 33 measured at a wavelength of 500 nm and the firing temperature. As the firing temperature increased, the light reflectance of the metal reflector 33 tended to decrease.
  • the reason why the light reflection characteristics of the metal reflector 33 are changed with respect to the firing temperature is considered to be due to the difference in the metal reflector structure with respect to the firing temperature.
  • the organometallic compound 7 is baked at a low temperature, the decomposition reaction of the organic silver is slow. Therefore, the precipitated Ag particles are bonded over time to form a continuous microstructure. It is thought that the structure of large and irregular particles is formed because the Ag particles precipitated before the formation of a continuous fine structure is fast and the reaction is completed. Accordingly, the temperature for firing the organometallic compound 7 is preferably as low as possible within the temperature range in which the thermal decomposition reaction occurs.
  • the metal metal compound liquid 7 is filled in the groove of the scintillator substrate 5 and baked to form the metal reflector 33 made of Ag.
  • the metal fine particle paste is put into the groove of the scintillator substrate 5.
  • the metal reflector 33 made of a fired metal fine particle may be formed by filling and firing.
  • the metal fine particles used for the metal fine particle paste are preferably metal fine particles containing Ag, Au, Al, Ni, etc., which have a high light reflectance with respect to visible light. Even when the metal fine particle paste is used, the viscosity of the paste is preferably 20 cP (0.020 Pa ⁇ s) or less from the viewpoint of easy filling into the grooves.
  • step 6 the filler 34 was filled into the grooves of the scintillator substrate 5.
  • the filler 34 a scintillator substrate manufactured by Three Bond Co., Ltd., mixed with epoxy resin of main agent 2023 and curing agent 2131D in a ratio of main agent 100: curing agent 30 (weight ratio) is used. 5 grooves were filled.
  • the epoxy resin is filled using a screen printing method, but other filling methods such as a dispensing method may be used. Furthermore, it is more preferable that the epoxy resin is filled in a reduced-pressure atmosphere so that no bubbles remain inside the epoxy resin.
  • the epoxy resin was cured by heating at 100 ° C. for 1 hour in an electric oven (FIG. 3 (f)).
  • step 7 the surface of the scintillator substrate 5 was ground.
  • the substrate surface grooved surface
  • a top reflector 35 was formed.
  • a white paint obtained by kneading 3 ⁇ m titanium oxide powder was applied to the surface (grooved surface) of the scintillator substrate 5 by screen printing. In this embodiment, the white paint is applied by the screen printing method, but other application methods such as a dispensing method may be used.
  • the white paint was cured by heating in an electric oven at 100 ° C. for 1 hour. (FIG. 3 (h)).
  • the base material 32 and the metal reflecting material 33 formed up to step 6 are formed under conditions optimal for forming between the scintillator elements. For this reason, the base material and the metal reflector formed on the upper surface are thick on the upper surface side, and cracks may be formed at the bent corners and may be peeled off. Therefore, the base material 32 and the metal reflecting material 33 adhering to the upper surface side of the scintillator substrate 5 are temporarily removed in step 7, and then the upper surface reflecting material 35 is re-formed in step 8.
  • a white paint kneaded with an epoxy resin and titanium oxide powder was used as the upper surface reflector 35, but white powder that reflects visible light emitted by the scintillator element 31, for example, silicon oxide or aluminum oxide powder, You may use the white coating material which used the powder which coat
  • step 9 the back surface of the scintillator substrate 5 (the surface opposite to the groove processing surface) was ground.
  • the base material 32, the metal reflector 33, and the filler 34 attached to the back surface of the scintillator substrate 5 are removed, and the scintillator substrate 5 is ground until the thickness of the scintillator substrate 5 is reduced from 2.0 mm to 1.7 mm. 5 was separated into a plurality of columnar scintillator elements 31 to form a scintillator array 3 (FIG. 3 (i)).
  • step 10 the opposite surface of the upper surface reflector 35 of the scintillator array 3 and the surface of the semiconductor light detection element array 2 are bonded so that the plurality of scintillator elements 31 and the plurality of semiconductor light detection elements 21 face each other. Bonded through layer 4.
  • the adhesive layer 4 is made of Epoxy Technologies, Epo-Tek301 optical adhesive, and heated in an electric furnace at 80 ° C. for 1 hour, so that the scintillator array 3 and the semiconductor photodetector array 2 are cured and bonded. And the radiation detector 1 was completed (FIG.3 (j)).
  • Example 3 Next, the crosstalk between the radiation detector of the present invention and a conventional radiation detector using a reflective material of white paint was compared.
  • radiation detectors having different scintillator element intervals of 20 ⁇ m to 150 ⁇ m were produced by the same manufacturing method as in Example 1.
  • a radiation detector having the same scintillator element size as in the present embodiment and a different scintillator element interval of 20 ⁇ m to 150 ⁇ m was manufactured using Three Bond Co., Ltd., main agent 2023, curing agent 2131D epoxy resin, main agent 100: cured. It was prepared using a white paint reflecting material in which titanium oxide powder having an average particle size of about 0.3 ⁇ m was kneaded with the mixture of the agent 30 (weight ratio).
  • FIG. 7 shows the relationship between scintillator element spacing and crosstalk.
  • the crosstalk increased as the scintillator element interval narrowed.
  • the scintillator element interval was Even if it becomes narrow, crosstalk is kept small. From the above, it was confirmed that the radiation detector of the present example was superior in crosstalk as compared with the radiation detector of the comparative example.
  • 1 radiation detector 2 semiconductor photodetector array, 21 semiconductor light detection element, 3 scintillator array, 31 scintillator elements, 32 Base material, 33 metal reflector, 34 filler, 35 top reflector, 4 Adhesive layer, 5 Scintillator board, 6 SOG liquid, 7 Organometallic compound solution.

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Abstract

Disclosed is a radiation detector used for high-resolution X-ray CT apparatus wherein the interval between adjacent scintillator elements is 100 μm or shorter and wherein a reflective member having a small crosstalk is provided. A method for manufacturing such a radiation detector is also disclosed. Over a semiconductor light detecting element array wherein semiconductor light detecting elements are arrayed in a matrix, scintillator elements are attached and arrayed in such a way that the bottom of each scintillator element faces to the corresponding semiconductor light detecting element. A light reflective member is provided to the surfaces other than the bottom of each scintillator element. The light reflective member is formed by sequentially forming a base member and a metal reflective member.

Description

放射線検出器および放射線検出器の製造方法Radiation detector and method for manufacturing radiation detector
　本発明は、Ｘ線、α線、β線、γ線などの放射線を扱うコンピュータ断層撮影（ＣＴ）装置に用いられる放射線検出器に関するもので、特にシンチレータ素子を用いた分解能の高いＸ線ＣＴ装置用放射線検出器に関するものである。 The present invention relates to a radiation detector used in a computed tomography (CT) apparatus that handles radiation such as X-rays, α-rays, β-rays, and γ-rays, and in particular, a high-resolution X-ray CT apparatus that uses a scintillator element. The present invention relates to a radiation detector.
　放射線ＣＴ装置は、被撮影体を中心に対称の位置関係で放射線源（例えばＸ線管）と放射線検出器とを配置したもので、検出位置ごとの放射線強度を測定して被撮影体の内部構造を観察する構成になっている。 A radiation CT apparatus includes a radiation source (for example, an X-ray tube) and a radiation detector arranged symmetrically with respect to an object to be imaged, and measures the radiation intensity at each detection position to measure the inside of the object to be imaged. It is configured to observe the structure.
　放射線検出器の基本構造は、複数の配列した半導体光検出素子にシンチレータ素子を配置したものであり、シンチレータ素子が放射線源側に開口してＸ線などの放射線を受けるようになっている。シンチレータ素子は一般的に柱状に加工されたＣｄＷＯ４、Ｂｉ４Ｇｅ３Ｏ１２、Ｇｄ２Ｏ２Ｓなどの材料からなり、複数のシンチレータ素子が互いに隣接する素子と間隔をあけて２次元配置されている。放射線がシンチレータ素子の開口面に入射すると、シンチレータ素子自身が発光して可視光を発し、この可視光を開口面の反対面に配置された半導体光検出素子が受光して電気信号を出力する。放射線ＣＴ装置では、隣り合って配置された複数のシンチレータ素子がＣＴ画像の各画素に相当する。従って、放射線検出器のシンチレータ素子は、出来るだけ小さくかつ隣の素子との間隔が狭くなるように設計され、解像度、分解能の向上が図られている。 The basic structure of the radiation detector is one in which a scintillator element is arranged on a plurality of arranged semiconductor photodetecting elements, and the scintillator element opens to the radiation source side to receive radiation such as X-rays. The scintillator element is generally made of a material such as CdWO 4 , Bi 4 Ge 3 O 12 , or Gd 2 O 2 S processed into a columnar shape, and a plurality of scintillator elements are two-dimensionally arranged with an interval between adjacent elements. ing. When radiation is incident on the opening surface of the scintillator element, the scintillator element itself emits light to emit visible light, and the semiconductor light detecting element disposed on the opposite surface of the opening surface receives the light and outputs an electrical signal. In the radiation CT apparatus, a plurality of scintillator elements arranged adjacent to each other correspond to each pixel of the CT image. Therefore, the scintillator element of the radiation detector is designed so as to be as small as possible and the distance between adjacent elements is narrowed to improve the resolution and resolution.
　柱状に加工されたシンチレータ素子の外周面は、半導体光検出素子との対向面を除いて光反射材が被覆されている。特許文献１には、シンチレータ素子に酸化チタンなどの粉末をエポキシ系などの樹脂で混練した白色塗料（光反射材）を被覆する例が開示されている。このように、シンチレータ素子の外周面を光反射材で被覆することにより、シンチレータ素子で発光した可視光はシンチレータ素子内部に閉じ込められ、効率良く半導体光検出素子に導かれる。 The outer peripheral surface of the scintillator element processed into a columnar shape is covered with a light reflecting material except for the surface facing the semiconductor photodetecting element. Patent Document 1 discloses an example in which a scintillator element is coated with a white paint (light reflecting material) in which a powder such as titanium oxide is kneaded with an epoxy resin or the like. Thus, by covering the outer peripheral surface of the scintillator element with the light reflecting material, the visible light emitted by the scintillator element is confined inside the scintillator element and efficiently guided to the semiconductor photodetector element.
　シンチレータ素子を被覆する光反射材の他の例として、特許文献２には、スパッタリング法、ＣＶＤ（化学気相堆積）法などの方法でシンチレータ素子表面にＡｕ、Ａｇ、Ａｌ、Ｎｉ等の金属反射材を被覆する例が開示されている。 As another example of the light reflecting material for covering the scintillator element, Patent Document 2 discloses a metal reflection such as Au, Ag, Al, Ni, etc. on the surface of the scintillator element by a method such as sputtering or CVD (chemical vapor deposition). An example of covering the material is disclosed.
　また、金属反射材としては、特許文献３に金属粒子の焼結体を反射材とする例が開示されている。本文献では、溶媒に粒径１μｍ以下、好ましくは０．１μｍ以下の金属微粒子を分散させたコーティング材を焼結することで、金属反射材が得られるとしている。 Further, as a metal reflector, Patent Document 3 discloses an example in which a sintered body of metal particles is used as a reflector. In this document, a metal reflector is obtained by sintering a coating material in which metal fine particles having a particle size of 1 μm or less, preferably 0.1 μm or less are dispersed in a solvent.
特開平５―１９０６０号公報JP-A-5-19060 特開２００５―１８９２３４号公報JP 2005-189234 A 特開２００４－３３３３８１号公報Japanese Patent Laid-Open No. 2004-333381
　放射線ＣＴ装置の高解像度化の要求に伴い、シンチレータ素子を用いた放射線検出器は、シンチレータ素子の開口面積は小さく、隣の素子との間隔は狭く配置する改良がなされてきた。近年では、隣り合うシンチレータ素子の間隔は１００μｍ以下が要求されるようになってきている。このような狭い間隔でシンチレータ素子を並べる放射線検出器の作製では、従来技術において以下のような問題があった。 With the demand for higher resolution of the radiation CT apparatus, the radiation detector using the scintillator element has been improved to have a small opening area of the scintillator element and a narrow interval between adjacent elements. In recent years, an interval between adjacent scintillator elements is required to be 100 μm or less. The production of a radiation detector in which scintillator elements are arranged at such a narrow interval has the following problems in the prior art.
　従来技術では、特許文献１のように、隣り合うシンチレータ素子の隙間に酸化チタンなどの粉末をエポキシ系樹脂などで混練した白色塗料を充填して反射材としていた。この方法では、シンチレータ素子が発した可視光は、白色塗料中の酸化チタン粉末で反射して、半導体光検出素子に導かれる。 In the prior art, as in Patent Document 1, a gap between adjacent scintillator elements is filled with a white paint obtained by kneading a powder of titanium oxide or the like with an epoxy resin or the like as a reflector. In this method, the visible light emitted from the scintillator element is reflected by the titanium oxide powder in the white paint and guided to the semiconductor photodetector element.
　ところが、隣り合うシンチレータ素子の間隔が狭くなると、充填される白色塗料が薄くなってしまい、シンチレータ素子が発した可視光の一部は酸化チタン粉末で反射せず、白色塗料を透過して隣り合うシンチレータ素子に侵入してしまう。この現象はクロストークと呼ばれるもので、放射線検出器の解像度、分解能を下げる原因となってしまう。 However, when the interval between adjacent scintillator elements becomes narrow, the white paint to be filled becomes thin, and part of the visible light emitted by the scintillator elements is not reflected by the titanium oxide powder, but passes through the white paint and adjoins. It will enter the scintillator element. This phenomenon is called crosstalk, and causes a reduction in the resolution and resolution of the radiation detector.
　図８は、酸化チタン粉末とエポキシ系樹脂を混練した白色塗料の、反射材厚みと波長５００ｎｍの光の光透過率との関係を示したものである。反射材である白色塗料が薄くなると光透過率は増大する傾向がある。特に１００μｍ以下の厚さになると光透過率の増大が顕著であり、このような光透過率では、放射線検出器においてクロストークの発生は避けられない。 FIG. 8 shows the relationship between the thickness of the reflective material and the light transmittance of light having a wavelength of 500 nm in a white paint kneaded with titanium oxide powder and an epoxy resin. When the white paint, which is a reflective material, becomes thinner, the light transmittance tends to increase. In particular, when the thickness is 100 μm or less, the increase in light transmittance is remarkable. With such light transmittance, the occurrence of crosstalk is inevitable in the radiation detector.
　この問題を解決する方法として、エポキシ系樹脂と混練する酸化チタン粉末の量を増やし、酸化チタン粉末の密度を上げて光が透過しないようにする方法が考えられる。しかし、酸化チタン粉末の量を増やすほど白色塗料の粘度が高くなり、隣り合うシンチレータ素子の隙間に充填しにくくなる。 As a method of solving this problem, a method of increasing the density of the titanium oxide powder to be kneaded with the epoxy resin and increasing the density of the titanium oxide powder so that light is not transmitted can be considered. However, as the amount of the titanium oxide powder increases, the viscosity of the white paint increases, and it becomes difficult to fill the gaps between adjacent scintillator elements.
　従って、隣り合うシンチレータ素子の間隔が狭い放射線検出器に、酸化チタンなどの粉末をエポキシ系樹脂などで混練した白色塗料を充填することは、充填性と光学特性の両立の観点から困難であることがわかっている。 Therefore, it is difficult to fill a white detector in which powders such as titanium oxide are kneaded with an epoxy-based resin into a radiation detector in which the interval between adjacent scintillator elements is narrow from the viewpoint of both filling properties and optical characteristics. I know.
　一方、反射材が金属の場合、概ね厚さが０．１μｍ以上の金属であれば、可視光を透過することなく全反射することが可能である。従って、シンチレータ素子を被覆する反射材に金属を用いれば、隣り合うシンチレータ素子の間隔が狭くなってもクロストークを回避することができる。 On the other hand, when the reflective material is metal, if the thickness is approximately 0.1 μm or more, total reflection is possible without transmitting visible light. Therefore, if metal is used for the reflective material that covers the scintillator elements, crosstalk can be avoided even if the interval between adjacent scintillator elements is narrow.
　しかし、隣り合うシンチレータ素子の隙間に金属反射材を形成するのは、隙間に対してシンチレータ素子が厚いので非常に困難である。例えば、隣り合うシンチレータ素子の隙間が１００μｍ、シンチレータ素子の厚みが１．７ｍｍとすると、幅１００μｍ、深さ１．７ｍｍの溝の側面に金属反射材を形成しなければならないことになる。このように、アスペクト比の高い溝の側面に、特許文献２に開示されるような、蒸着法、スパッタリング法、ＣＶＤ法などを用いて金属反射膜を形成しようとしても、溝の底面に近くなるほど膜厚は薄くなってしまうので、反射材として機能する厚さの金属をシンチレータ素子側面全体に形成するのは非常に困難である。 However, it is very difficult to form a metal reflector in the gap between adjacent scintillator elements because the scintillator element is thick with respect to the gap. For example, if the gap between adjacent scintillator elements is 100 μm and the thickness of the scintillator element is 1.7 mm, a metal reflector must be formed on the side surface of the groove having a width of 100 μm and a depth of 1.7 mm. As described above, even when an attempt is made to form a metal reflective film on the side surface of a groove having a high aspect ratio by using a vapor deposition method, a sputtering method, a CVD method, or the like as disclosed in Patent Document 2, the closer the surface is to the bottom surface of the groove. Since the film thickness becomes thin, it is very difficult to form a metal having a thickness that functions as a reflector on the entire side surface of the scintillator element.
　図９は、スパッタリング法を用いて、幅１００μｍ、深さ１．７ｍｍの溝内にＡｇ膜を形成したときの、溝深さ方向のＡｇ膜厚分布である。図９では溝最上部のＡｇ膜厚が１μｍになるように膜を形成しているが、溝の側面に形成されるＡｇの膜厚は溝深さに比例して薄くなり、表面からの深さが０．２ｍｍ以上になると溝側面にはＡｇ膜は形成されなくなってしまう。従って、図９のような方法では、隣り合うシンチレータ素子の隙間に反射材を形成することはできない。 FIG. 9 shows an Ag film thickness distribution in the groove depth direction when an Ag film is formed in a groove having a width of 100 μm and a depth of 1.7 mm by sputtering. In FIG. 9, the film is formed so that the Ag film thickness at the top of the groove is 1 μm. However, the film thickness of Ag formed on the side surface of the groove is reduced in proportion to the groove depth, and the depth from the surface is reduced. When the thickness is 0.2 mm or more, the Ag film is not formed on the side surface of the groove. Therefore, with the method as shown in FIG. 9, it is not possible to form a reflector in the gap between adjacent scintillator elements.
　他に、アスペクト比の高い溝の側面に金属反射材を形成する方法として、特許文献３に開示されるような、金属微粒子を含む溶液を塗布・焼結して金属膜を形成する方法が考えられる。しかしこの方法では、膜組織が金属微粒子の粒径を反映して粗くなるため、光が散乱して高い光反射率を得ることはできない。 In addition, as a method of forming a metal reflector on the side surface of a groove having a high aspect ratio, a method of forming a metal film by applying and sintering a solution containing metal fine particles as disclosed in Patent Document 3 is considered. It is done. However, in this method, since the film structure becomes rough reflecting the particle size of the metal fine particles, light cannot be scattered and high light reflectance cannot be obtained.
　図１０は、平均粒径２５ｎｍのＡｇ微粒子を分散させた溶液をシンチレータ素子表面に塗布して焼結したＡｇ膜の反射特性を示したものである。図１０のＡｇ膜では、波長４００ｎｍから９００ｎｍの可視光域全域において、５０％以下の光反射率しか得られない。 FIG. 10 shows the reflection characteristics of an Ag film obtained by applying a solution in which Ag fine particles having an average particle diameter of 25 nm are dispersed to the surface of the scintillator element and sintering it. In the Ag film of FIG. 10, only a light reflectance of 50% or less can be obtained in the entire visible light region with a wavelength of 400 nm to 900 nm.
　さらに、金属微粒子を含む溶液は、金属微粒子を作製して溶媒に分散させる工程が必要になることから、非常に高価な溶液になる。従って、金属微粒子を含む溶液を用いると、放射線検出器の製造コストが高くなってしまう問題がある。 Furthermore, a solution containing metal fine particles becomes a very expensive solution because a step of producing metal fine particles and dispersing them in a solvent is required. Therefore, when a solution containing fine metal particles is used, there is a problem that the manufacturing cost of the radiation detector is increased.
　本願発明は、以上の問題を解決するものであり、隣り合うシンチレータ素子の間隔が狭くても、クロストークが小さい、放射線検出器およびその製造方法を提供するものである。 The present invention solves the above problems, and provides a radiation detector and a method for manufacturing the same, in which crosstalk is small even when the interval between adjacent scintillator elements is narrow.
　本発明の放射線検出器は、複数の半導体光検出素子がマトリクス状に配列された半導体光検出素子アレイ上に、複数のシンチレータ素子の各々がその底面を各半導体光検出素子に対向して配列され、シンチレータ素子の底面以外の面に光反射材を設けた放射線検出器であって、 In the radiation detector of the present invention, a plurality of scintillator elements are arrayed on a semiconductor photodetector element array in which a plurality of semiconductor photodetector elements are arranged in a matrix so that the bottom faces the semiconductor photodetector elements. A radiation detector provided with a light reflecting material on a surface other than the bottom surface of the scintillator element,
　前記シンチレータ素子は互いに１００μｍ以下の間隔をもって隣り合って配列され、光反射材は下地材と金属反射材とが順に形成されたものであることを特徴としている。 The scintillator elements are arranged adjacent to each other with an interval of 100 μm or less, and the light reflecting material is formed by sequentially forming a base material and a metal reflecting material.
　ここで、前記下地材が無機酸化物を含む下地材であってもよい。また、前記無機酸化物が酸化シリコンを含んでもよい。さらに、前記無機酸化膜が酸化チタンを含んでもよい。 Here, the base material may be a base material containing an inorganic oxide. The inorganic oxide may include silicon oxide. Furthermore, the inorganic oxide film may contain titanium oxide.
　また、本発明の放射線検出器の一態様によると、前記酸化シリコンを含む無機酸化物がＳＯＧ（Spin On Glass）の焼成物であってもよい。また、前記酸化チタンを含む無機酸化物が酸化チタン前駆体の焼成物であってもよい。また、前記金属反射材がＡｇ、Ａｕ、Ａｌ、Ｎｉの少なくとも一つを含む有機金属化合物の焼成物であってもよい。 Further, according to one aspect of the radiation detector of the present invention, the inorganic oxide containing silicon oxide may be a fired product of SOG (Spin On Glass). The inorganic oxide containing titanium oxide may be a fired product of a titanium oxide precursor. The metal reflector may be a fired product of an organometallic compound containing at least one of Ag, Au, Al, and Ni.
　本願発明の放射線検出器の製造方法は、シンチレータ基板の片面に格子状で幅１００μｍ以下の加工溝を形成する工程、前記加工溝側面に無機酸化物の下地材と金属反射材とを順に形成する工程、前記シンチレータ基板の溝加工面と反対の面を加工して複数のシンチレータ素子からなるシンチレータアレイを形成する工程、複数の半導体光検出素子からなる半導体光検出素子アレイと前記シンチレータアレイとを、半導体光検出素子とシンチレータ素子とが対向するように接着する工程を備えたこと特徴としている。 In the manufacturing method of the radiation detector of the present invention, a step of forming a processing groove having a grid shape of 100 μm or less on one side of a scintillator substrate, and an inorganic oxide base material and a metal reflecting material are sequentially formed on the side of the processing groove. Forming a scintillator array composed of a plurality of scintillator elements by processing a surface opposite to the groove processing surface of the scintillator substrate, a semiconductor photodetector element array composed of a plurality of semiconductor photodetector elements, and the scintillator array, The semiconductor photodetecting element and the scintillator element are provided with a step of bonding so as to face each other.
　また、ここで無機酸化物の前駆体溶液を、ディップコーティング法、スクリーン印刷法、スピンコーティング法、ディスペンス法のいずれかの方法で前記加工溝に充填し焼成して、前記下地材を形成してもよい。さらに前記無機酸化物の前駆体溶液の粘度を２０ｃＰ（０．０２０Ｐａ・ｓ）以下としてもよい。 In addition, the inorganic oxide precursor solution is filled in the processed groove by one of a dip coating method, a screen printing method, a spin coating method, and a dispensing method and baked to form the base material. Also good. Further, the viscosity of the inorganic oxide precursor solution may be 20 cP (0.020 Pa · s) or less.
　また、本発明の放射線検出器の製造方法の一態様では、有機金属化合物溶液を、ディップコーティング法、スクリーン印刷法、スピンコーティング法、ディスペンス法のいずれかの方法で前記下地材を形成した前記加工溝に充填し焼成して、前記金属反射材を形成してもよい。また、前記有機金属化合物溶液の粘度を２０ｃＰ（０．０２０Ｐａ・ｓ）以下としてもよい。 Further, in one aspect of the method for producing a radiation detector of the present invention, the processing in which the base material is formed from an organometallic compound solution by any one of a dip coating method, a screen printing method, a spin coating method, and a dispensing method. The metal reflector may be formed by filling the groove and firing. The viscosity of the organometallic compound solution may be 20 cP (0.020 Pa · s) or less.
　本発明によれば、隣り合うシンチレータ素子の間隔が狭くても、クロストークが小さい放射線検出器とすることができる。そして、本発明の放射線検出器は、解像度、分解度が高い、高解像度Ｘ線ＣＴ装置用放射線検出器として用いることができる。 According to the present invention, even if the interval between adjacent scintillator elements is narrow, a radiation detector with small crosstalk can be obtained. The radiation detector of the present invention can be used as a radiation detector for a high-resolution X-ray CT apparatus with high resolution and resolution.
本発明の実施の形態に係る放射線検出器の斜視図である。It is a perspective view of a radiation detector concerning an embodiment of the invention. 本発明の実施の形態に係る放射線検出器の断面拡大図である。It is a cross-sectional enlarged view of the radiation detector which concerns on embodiment of this invention. 本発明の実施の形態に係る放射線検出器の製造方法を示す説明図である。It is explanatory drawing which shows the manufacturing method of the radiation detector which concerns on embodiment of this invention. 本発明の実施の形態に係る金属反射材のＳＥＭ像を表す説明図である。It is explanatory drawing showing the SEM image of the metal reflecting material which concerns on embodiment of this invention. 本発明の実施例の一例に係る金属反射材のＳＥＭ像を表す説明図である。It is explanatory drawing showing the SEM image of the metal reflecting material which concerns on an example of the Example of this invention. 本発明の一実施例で用いた有機金属化合物液の焼成温度と金属反射材の光反射率の関係を示す図である。It is a figure which shows the relationship between the calcination temperature of the organometallic compound liquid used in one Example of this invention, and the light reflectivity of a metal reflector. 本発明の他の実施例におけるシンチレータ素子間隔とクロストークとの関係を示す図である。It is a figure which shows the relationship between the scintillator element space | interval and crosstalk in the other Example of this invention. 従来の白色塗料反射材の厚さと光透過率の関係を示す図である。It is a figure which shows the relationship between the thickness of the conventional white coating material reflective material, and light transmittance. 従来の成膜方法で加工溝に金属反射材を形成したときの膜厚分布を示す図である。It is a figure which shows film thickness distribution when a metal reflecting material is formed in a processing groove with the conventional film-forming method. 従来の金属微粒子を用いたＡｇ反射材の光反射率を示す図である。It is a figure which shows the light reflectivity of Ag reflecting material using the conventional metal microparticle. 本発明の実施の形態に係る金属反射材のＳＥＭ像を表す説明図である。It is explanatory drawing showing the SEM image of the metal reflecting material which concerns on embodiment of this invention. 本発明の実施例の一例に係る金属反射材のＳＥＭ像を表す説明図である。It is explanatory drawing showing the SEM image of the metal reflecting material which concerns on an example of the Example of this invention.
　本願発明の放射線検出器及び製造方法に係る実施の形態を以下に図面を参照しながら詳細に説明する。図１は、本実施例の放射線検出器を示す斜視図である。本願発明の放射線検出器１は、半導体光検出素子アレイ２上にシンチレータアレイ３が接着層４を介して取り付けられたものである。半導体光検出素子アレイ２は、複数の半導体光検出素子２１を平板上に配列したもので、図１の例では行方向にＮ個、列方向にＭ個のマトリクス状に配列したものとしているが、配列の方法はこれに限られない。シンチレータアレイ３は、柱状に加工されたシンチレータ素子３１を含む。このシンチレータアレイ３は、各シンチレータ素子３１が、その底面がそれぞれ対応する半導体光検出素子２１の表面に一致するように位置あわせされ、接着層４を介して取り付けられる。 Embodiments according to the radiation detector and manufacturing method of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing the radiation detector of the present embodiment. In the radiation detector 1 of the present invention, a scintillator array 3 is attached to a semiconductor photodetector element array 2 via an adhesive layer 4. The semiconductor photodetecting element array 2 has a plurality of semiconductor photodetecting elements 21 arranged on a flat plate. In the example of FIG. 1, it is assumed that N pieces are arranged in a row direction and M pieces are arranged in a column direction. The arrangement method is not limited to this. The scintillator array 3 includes scintillator elements 31 processed into a columnar shape. In this scintillator array 3, each scintillator element 31 is aligned so that its bottom surface coincides with the surface of the corresponding semiconductor photodetecting element 21, and is attached via an adhesive layer 4.
　シンチレータ素子３１は、例えば、ＣｄＷＯ４、Ｂｉ４Ｇｅ３Ｏ１２、Ｇｄ２Ｏ２Ｓなどのセラミックスシンチレータ材料を用いることができ、接着層４は光透過率が高い光学用接着剤、例えばＥｐｏｘｙ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社製、Ｅｐｏ－Ｔｅｋ３０１（商標）などを用いる。図１中には示されていないが、シンチレータ素子３１の側面および上面（半導体光検出素子３１と対向する面の反対面）には、シンチレータ素子３１が発した可視光を反射する反射材が形成されている。 For the scintillator element 31, for example, a ceramic scintillator material such as CdWO 4 , Bi 4 Ge 3 O 12 , Gd 2 O 2 S or the like can be used, and the adhesive layer 4 is an optical adhesive having a high light transmittance, such as Epoxy Technologies. Epo-Tek301 (trademark) manufactured by KK is used. Although not shown in FIG. 1, a reflecting material that reflects visible light emitted from the scintillator element 31 is formed on the side surface and the upper surface of the scintillator element 31 (opposite surface opposite to the surface facing the semiconductor light detection element 31). Has been.
　図２は図１に示した放射線検出器１の断面を拡大した模式図である。シンチレータ素子３１の側面には、下地材３２、金属反射材３３が順に形成され、シンチレータ素子３１は、接着層４を介して対応する半導体光検出素子２１に対向して取り付けられる。 FIG. 2 is an enlarged schematic view of the cross section of the radiation detector 1 shown in FIG. A base material 32 and a metal reflector 33 are sequentially formed on the side surface of the scintillator element 31, and the scintillator element 31 is attached to the corresponding semiconductor photodetecting element 21 through the adhesive layer 4.
　ここで下地材３２は、酸化シリコンや酸化チタンなど、シンチレータ素子３１の発光波長において光透過率が高い無機酸化物材料を用いて、１０ｎｍ～１０μｍの厚さに形成する。金属反射材３３には、Ａｇ、Ａｕ、Ａｌ、Ｎｉの少なくとも一つを含み、シンチレータ素子３１の発光波長において光反射率が高い材料を用いて、０．１μｍ～１０μｍの厚さに形成する。金属反射材３３の酸化を防ぐために、金属反射材３３の上にさらに酸化シリコンなどの保護材をコーティングしても良い。 Here, the base material 32 is formed to a thickness of 10 nm to 10 μm using an inorganic oxide material having high light transmittance at the emission wavelength of the scintillator element 31 such as silicon oxide or titanium oxide. The metal reflector 33 is made of a material containing at least one of Ag, Au, Al, and Ni and having a high light reflectivity at the emission wavelength of the scintillator element 31 to a thickness of 0.1 μm to 10 μm. In order to prevent oxidation of the metal reflector 33, a protective material such as silicon oxide may be further coated on the metal reflector 33.
　側面に下地材３２と金属反射材３３を形成した複数のシンチレータ素子３１の間に隙間が生じる場合には、隣り合うシンチレータ素子３１との隙間に充填材３４を充填しても良い。充填材３４にはエポキシ樹脂、紫外線硬化性樹脂、ポリイミド樹脂などの樹脂を用いることができる。さらに、これらの樹脂にタングステン、モリブデンなどの重金属粉末を混練したものを充填すれば、シンチレータ素子３１間の放射線遮蔽効果を強め、クロストークの発生をより一層防ぐことができる。 When a gap is generated between the plurality of scintillator elements 31 having the base material 32 and the metal reflector 33 formed on the side surface, the filler 34 may be filled in the gap between the adjacent scintillator elements 31. For the filler 34, a resin such as an epoxy resin, an ultraviolet curable resin, or a polyimide resin can be used. Furthermore, if these resins are filled with a mixture of heavy metal powders such as tungsten and molybdenum, the radiation shielding effect between the scintillator elements 31 can be enhanced, and the occurrence of crosstalk can be further prevented.
　シンチレータ素子３１の半導体光検出素子２１と対向する面の反対面には、上面反射材３５が形成される。この上面反射材３５はシンチレータ側面と同様に、下地材３２と金属反射材３３を順に形成したものを用いても良いし、従来の放射線検出器で反射材として用いられる、酸化チタン粉末などをエポキシ系樹脂などで混練した白色塗料を用いても良い。 An upper surface reflecting material 35 is formed on the surface of the scintillator element 31 opposite to the surface facing the semiconductor light detection element 21. As the side surface of the scintillator, the upper surface reflecting material 35 may be formed by sequentially forming a base material 32 and a metal reflecting material 33, or titanium oxide powder or the like used as a reflecting material in a conventional radiation detector is epoxy. A white paint kneaded with a resin may be used.
　次に、図３を用いて、本実施の形態に係る放射線検出器の製造方法を、工程を追いながら説明する。 Next, the manufacturing method of the radiation detector according to the present embodiment will be described with reference to FIGS.
　まず工程１では、所望のサイズに加工したＧｄ２Ｏ２Ｓのシンチレータ基板５に、機械加工で溝を略一定のピッチで格子状に形成する（図３（ａ））。 First, in step 1, grooves are formed in a lattice pattern at a substantially constant pitch on a Gd 2 O 2 S scintillator substrate 5 processed to a desired size (FIG. 3A).
　次に工程２で、溝加工したシンチレータ基板５を、日立化成工業（株）製、ＨＳＧ－Ｒ７－１３のＳＯＧ液６に浸漬して、シンチレータ基板５に形成した溝内にＳＯＧ液６を充填する（図３（ｂ））。なお、このようなディップコーティング法でシンチレータ基板５の溝内部にＳＯＧ液６を充填する方法に代えて、スクリーン印刷法、スピンコーティング法、ディスペンス法などの方法を用いて充填を行ってもよい。 Next, in step 2, the grooved scintillator substrate 5 is dipped in the SOG solution 6 of HSG-R7-13 manufactured by Hitachi Chemical Co., Ltd., and the SOG solution 6 is filled into the groove formed in the scintillator substrate 5. (FIG. 3B). Instead of filling the SOG liquid 6 into the groove of the scintillator substrate 5 by such a dip coating method, filling may be performed using a method such as a screen printing method, a spin coating method, or a dispensing method.
　ＳＯＧ液６とシンチレータ基板５の濡れ性が悪い場合には、ＳＯＧ液６を溝内部に充填する前に、ＨＭＤＳ（ヘキサメチルジシラザン）処理や、酸素プラズマ照射などの濡れ性改善の前処理を行なっても良い。さらに、溝内のＳＯＧ液６が過剰な場合には、遠心力を使ってＳＯＧ液６を振り切るか、あるいは、不織布（旭化成せんい株式会社製、ベンコット）でＳＯＧ液６を吸い取るなどして、余分なＳＯＧ液６を除去しても良い。 If the wettability between the SOG liquid 6 and the scintillator substrate 5 is poor, a pretreatment for improving wettability such as HMDS (hexamethyldisilazane) treatment or oxygen plasma irradiation is performed before filling the groove with the SOG liquid 6. You can do it. Furthermore, when the SOG liquid 6 in the groove is excessive, the SOG liquid 6 is shaken off using centrifugal force, or the SOG liquid 6 is sucked off with a non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott). The SOG liquid 6 may be removed.
　ＳＯＧ液６は、粘度が高くなると溝内に充填される際に気泡を巻き込みやすく、均一充填が困難になるので、その粘度については実験的に適切になるように検討したうえでＳＯＧ液６を調製することが好ましい。本実施の形態では、１５ｃＰ（０．０１５Ｐａ・ｓ）の粘度のＳＯＧ液６を用いる例を示す。 When the viscosity of the SOG liquid 6 is increased, bubbles are likely to be entrained when filling the groove, and uniform filling becomes difficult. Therefore, the viscosity of the SOG liquid 6 is considered to be experimentally appropriate. It is preferable to prepare. In the present embodiment, an example in which the SOG liquid 6 having a viscosity of 15 cP (0.015 Pa · s) is used will be described.
　次に工程３では、ＳＯＧ液６を焼成して酸化シリコンを含む下地材３２を形成する。焼成には電気炉を用い、室温から昇温し、予め定めた温度で予め定めた時間だけ保持する。焼成中の酸素濃度は十分低減して、例えば１０００ｐｐｍ以下としておく。この焼成により、酸化シリコンを含む下地材３２が溝加工面に形成され、溝加工面の面荒れが緩和される。本実施の形態では、４００℃で３０分保持する焼成を行い、溝加工面上の下地材３２の厚さが０．１～２μｍ、溝加工面の表面粗さＲａが５００ｎｍ以下となった基板を得た（図３（ｃ））。 Next, in step 3, the SOG liquid 6 is baked to form a base material 32 containing silicon oxide. An electric furnace is used for firing, the temperature is raised from room temperature, and the temperature is kept at a predetermined temperature for a predetermined time. The oxygen concentration during firing is sufficiently reduced, for example, 1000 ppm or less. By this firing, the base material 32 containing silicon oxide is formed on the groove processing surface, and the surface roughness of the groove processing surface is reduced. In the present embodiment, the substrate is baked at 400 ° C. for 30 minutes, the thickness of the base material 32 on the grooved surface is 0.1 to 2 μm, and the surface roughness Ra of the grooved surface is 500 nm or less. (FIG. 3C) was obtained.
　本実施の形態では、ＳＯＧ液６をシンチレータ基板５の溝内に充填、焼成して、酸化シリコンを含む下地材３２を形成したが、他の無機酸化物を含む下地材を形成しても良い。例えば、酸化チタンの前駆体液をシンチレータ基板５の溝内に充填、焼成して、酸化チタンを含む下地材３２を形成しても良い。他の酸化物の前駆体液を用いる場合でも、溝への充填のし易さから、液の粘度は２０ｃＰ（０．０２０Ｐａ・ｓ）以下であるのが好ましい。 In the present embodiment, the SOG liquid 6 is filled in the groove of the scintillator substrate 5 and baked to form the base material 32 containing silicon oxide. However, a base material containing another inorganic oxide may be formed. . For example, the base material 32 containing titanium oxide may be formed by filling a precursor liquid of titanium oxide into the groove of the scintillator substrate 5 and baking it. Even when another oxide precursor liquid is used, the viscosity of the liquid is preferably 20 cP (0.020 Pa · s) or less from the viewpoint of easy filling into the grooves.
　無機酸化物を含む下地材３２とすることで、次工程において、下地材３２上の有機金属化合物液７から金属が偏析しにくくなり、均一な金属反射材３３とすることができる。この効果は、無機酸化物を含む下地材３２が有機化合物液７に含まれる有機溶剤と反応しにくく、金属が偏析する起点が生じにくいためと考えられる。 By using the base material 32 containing an inorganic oxide, the metal is less likely to segregate from the organometallic compound liquid 7 on the base material 32 in the next step, and a uniform metal reflector 33 can be obtained. This effect is considered to be because the base material 32 containing an inorganic oxide hardly reacts with the organic solvent contained in the organic compound liquid 7, and the starting point for segregation of the metal hardly occurs.
　次に工程４では、下地材３２を形成したシンチレータ基板５を有機金属化合物液７に浸漬して、シンチレータ基板５の溝内に有機金属化合物液７を充填する。本実施の形態のある例では、有機金属化合物液７として、有機銀化合物液である藤倉化成（株）製、ナノ・ドータイト　ＸＡ－９０６９を用いることとする（図３（ｄ））。 Next, in step 4, the scintillator substrate 5 on which the base material 32 is formed is immersed in the organometallic compound solution 7, and the organometallic compound solution 7 is filled in the grooves of the scintillator substrate 5. In an example of the present embodiment, as the organometallic compound solution 7, Nano Dotite XA-9069 manufactured by Fujikura Kasei Co., Ltd., which is an organic silver compound solution, is used (FIG. 3 (d)).
　なお、本実施の形態では、ディップコーティング法でシンチレータ基板５の溝内部に有機金属化合物液７を充填したが、スクリーン印刷法、スピンコーティング法、ディスペンス法など他の方法を用いて充填しても良い。さらに、溝内の有機金属化合物液７が過剰な場合には、遠心力を使って有機金属化合物液７を振り切るか、あるいは、不織布（旭化成せんい（株）製、ベンコット）で有機金属化合物液７を吸い取るなどして、余分な有機金属化合物液７を除去しても良い。 In this embodiment, the organometallic compound liquid 7 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by using other methods such as a screen printing method, a spin coating method, and a dispensing method. good. Furthermore, when the organometallic compound liquid 7 in the groove is excessive, the organometallic compound liquid 7 is shaken off using centrifugal force, or the non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott) is used. The excess organometallic compound liquid 7 may be removed by sucking off the liquid.
　有機金属化合物液７は、粘度が高くなると溝内に充填される際に気泡を巻き込みやすく、均一充填が困難になるので、その粘度については実験的に適切になるように検討したうえでＳＯＧ液６を調製することが好ましい。本実施の形態では、１５ｃＰ（０．０１５Ｐａ・ｓ）の粘度の有機金属化合物液７を用いることとする。 When the viscosity of the organometallic compound liquid 7 is increased, bubbles are likely to be entrained when filling the grooves, and uniform filling becomes difficult. 6 is preferably prepared. In this embodiment, the organometallic compound liquid 7 having a viscosity of 15 cP (0.015 Pa · s) is used.
　次に工程５では、有機金属化合物７を焼成してＡｇを含む金属反射材３３を形成する。焼成にはホットプレートを用い、予め定めた温度（例えば１５０℃）で予め定めた時間（例えば３０分間）だけ保持する。焼成前の有機金属化合物７は無色透明であるが、焼成中にＡｇ粒子が析出すると茶色に変色し、その後Ａｇ粒子同士が結合して銀色の連続膜となる。このＡｇを含む、溝内の金属反射材３３の厚さは０．１～数μｍとなる（図３（ｅ））。 Next, in step 5, the metal reflecting material 33 containing Ag is formed by baking the organometallic compound 7. For baking, a hot plate is used and held at a predetermined temperature (for example, 150 ° C.) for a predetermined time (for example, 30 minutes). The organometallic compound 7 before firing is colorless and transparent, but when Ag particles are deposited during firing, the color changes to brown, and then the Ag particles are bonded together to form a silver continuous film. The thickness of the metal reflecting material 33 in the groove containing this Ag is 0.1 to several μm (FIG. 3E).
　本実施の形態では、有機金属化合物液７をシンチレータ基板５の溝内に充填、焼成して、Ａｇを含んだ金属反射材３３を形成したが、本発明の実施の形態はこれに限られず、可視光に対して、他の金属に比べ比較的光反射率の高い、Ａｇ、Ａｕ、Ａｌ、Ｎｉなどを含む金属微粒子ペーストをシンチレータ基板５の溝内に充填、焼成して、金属微粒子焼成体を含んだ金属反射材３３を形成しても良い。このような金属微粒子ペーストを用いる場合でも、溝への充填のし易さから、ペーストの粘度は２０ｃＰ（０．０２０Ｐａ・ｓ）以下とするのが好ましい。 In the present embodiment, the metal metal compound liquid 7 is filled in the groove of the scintillator substrate 5 and fired to form the metal reflector 33 containing Ag. However, the embodiment of the present invention is not limited to this, A metal fine particle paste containing Ag, Au, Al, Ni, etc., which has a relatively high light reflectance with respect to visible light, is filled in the groove of the scintillator substrate 5 and fired to obtain a fired metal fine particle. Alternatively, the metal reflector 33 containing may be formed. Even when such a metal fine particle paste is used, the viscosity of the paste is preferably 20 cP (0.020 Pa · s) or less because of easy filling into the grooves.
　次に工程６では、シンチレータ基板５の溝内に充填材３４を充填する。本実施の形態では、この充填材３４として、硬化剤を混合したエポキシ樹脂を用い、スクリーン印刷法によってシンチレータ基板５の溝内に充填する。なお、スクリーン印刷法を用いてエポキシ樹脂の充填を行う例に代えて、ディスペンス法など、他の充填方法を用いても良い。さらに、エポキシ樹脂の充填は、減圧雰囲気中で行い、エポキシ樹脂内部に気泡が残留しないようにするのがより好ましい。そしてこのエポキシ樹脂を、予め定めた温度に設定した電気オーブン中で、予め定めた時間だけ加熱して硬化させる（図３（ｆ））。 Next, in step 6, the filler 34 is filled into the grooves of the scintillator substrate 5. In the present embodiment, an epoxy resin mixed with a curing agent is used as the filler 34 and the grooves of the scintillator substrate 5 are filled by screen printing. In addition, it may replace with the example which fills an epoxy resin using a screen printing method, and may use other filling methods, such as a dispensing method. Furthermore, it is more preferable that the epoxy resin is filled in a reduced-pressure atmosphere so that no bubbles remain inside the epoxy resin. Then, this epoxy resin is heated and cured for a predetermined time in an electric oven set at a predetermined temperature (FIG. 3 (f)).
　次に工程７では、シンチレータ基板５の表面を研削する。基板表面（溝加工面）を研削することで、シンチレータ基板５表面に付着した、下地材３２、金属反射材３３、充填材３４を除去するのである（図３（ｇ））。 Next, in step 7, the surface of the scintillator substrate 5 is ground. By grinding the substrate surface (grooved surface), the base material 32, the metal reflector 33, and the filler 34 adhered to the surface of the scintillator substrate 5 are removed (FIG. 3G).
　次に工程８では、上面反射材３５を形成する。本実施の形態では、上面反射材３５として、硬化剤を混合したエポキシ樹脂に、さらに酸化チタン粉末を混練して白色塗料としたものを用い、シンチレータ基板５の表面（溝加工面）にスクリーン印刷法で塗布することとする。なお、スクリーン印刷法で白色塗料の塗布を行う例に代えて、ディスペンス法など、他の塗布方法を用いても良い。さらにこの白色塗料を、予め定めた温度に設定した電気オーブン中で、予め定めた時間だけ加熱して硬化させる（図３（ｈ））。 Next, in step 8, the upper surface reflecting material 35 is formed. In the present embodiment, the upper surface reflecting material 35 is made of epoxy resin mixed with a curing agent and further mixed with titanium oxide powder to form a white paint, and screen printing is performed on the surface (grooved surface) of the scintillator substrate 5. It will be applied by the method. In addition, instead of the example of applying the white paint by the screen printing method, other application methods such as a dispensing method may be used. Further, the white paint is heated and cured for a predetermined time in an electric oven set at a predetermined temperature (FIG. 3 (h)).
　本実施の形態では、上面反射材３５としてエポキシ樹脂と酸化チタン粉末を混練した白色塗料を用いたが、これに代えて、シンチレータ素子３１が発光する可視光を反射する白色粉末、例えば酸化シリコンや酸化アルミニウムの粉末や、酸化チタンの粉末に酸化シリコンをコーティングした粉末を用いた白色塗料を用いても良い。また、白色塗料を用いずに、工程２～工程６と同様の条件で、下地材と金属反射材とを順に形成しても良い。 In the present embodiment, a white paint in which an epoxy resin and titanium oxide powder are kneaded is used as the upper surface reflecting material 35. Instead, white powder that reflects visible light emitted by the scintillator element 31, such as silicon oxide or A white paint using aluminum oxide powder or titanium oxide powder coated with silicon oxide may be used. Further, the base material and the metal reflecting material may be formed in order under the same conditions as in Steps 2 to 6 without using the white paint.
　次に工程９では、シンチレータ基板５の裏面（溝加工面の反対面）を研削し、シンチレータ基板５の裏面に付着した下地材３２と金属反射材３３、充填材３４を除去する。これにより、シンチレータ基板５が、複数の柱状のシンチレータ素子３１に分離され、シンチレータアレイ３が形成されることとなる（図３（ｉ））。 Next, in step 9, the back surface of the scintillator substrate 5 (the surface opposite to the groove processing surface) is ground to remove the base material 32, the metal reflector 33, and the filler 34 attached to the back surface of the scintillator substrate 5. As a result, the scintillator substrate 5 is separated into a plurality of columnar scintillator elements 31, and the scintillator array 3 is formed (FIG. 3 (i)).
　最後に工程１０として、複数のシンチレータ素子３１と複数の半導体光検出素子２１とが対向するように位置合わせをして、シンチレータアレイ３の上面反射材３５の反対面と半導体光検出素子アレイ２の表面とを接着層４を介して接着する。接着層４には、光学用接着剤を用い、予め定めた温度に設定した電気炉中で予め定めた時間だけ加熱することで、シンチレータアレイ３と半導体光検出素子アレイ２とを接着する。こうして本実施の形態の放射線検出器１が完成する（図３（ｊ））。 Finally, in step 10, alignment is performed so that the plurality of scintillator elements 31 and the plurality of semiconductor light detection elements 21 face each other, and the opposite surface of the upper surface reflecting material 35 of the scintillator array 3 and the semiconductor light detection element array 2. The surface is bonded through an adhesive layer 4. The adhesive layer 4 is bonded to the scintillator array 3 and the semiconductor photodetecting element array 2 by using an optical adhesive and heating the adhesive layer 4 for a predetermined time in an electric furnace set at a predetermined temperature. Thus, the radiation detector 1 of the present embodiment is completed (FIG. 3 (j)).
（実施例１）
　次に、本発明の実施例について述べる。本実施例において、隣り合うシンチレータ素子３１の間隔は１００μｍ以下とする。 Example 1
Next, examples of the present invention will be described. In this embodiment, the interval between adjacent scintillator elements 31 is set to 100 μm or less.
　まず工程１では、幅７３ｍｍ、高さ２２ｍｍ、厚さ２．０ｍｍに加工したＧｄ２Ｏ２Ｓのシンチレータ基板５に、機械加工で、幅８０μｍ、深さ１．７ｍｍの溝を１ｍｍピッチで格子状に形成した（図３（ａ））。 First, in step 1, a Gd 2 O 2 S scintillator substrate 5 machined to a width of 73 mm, a height of 22 mm, and a thickness of 2.0 mm is machined to form grooves having a width of 80 μm and a depth of 1.7 mm at a pitch of 1 mm. (FIG. 3A).
　次に工程２で、溝加工したシンチレータ基板５を、日立化成工業（株）製、ＨＳＧ－Ｒ７－１３のＳＯＧ液６に浸漬して、シンチレータ基板５に形成した溝内にＳＯＧ液６を充填した（図３（ｂ））。 Next, in step 2, the grooved scintillator substrate 5 is dipped in the SOG solution 6 of HSG-R7-13 manufactured by Hitachi Chemical Co., Ltd., and the SOG solution 6 is filled into the groove formed in the scintillator substrate 5. (FIG. 3B).
　本実施例では、ディップコーティング法でシンチレータ基板５の溝内部にＳＯＧ液６を充填したが、スクリーン印刷法、スピンコーティング法、ディスペンス法などの方法を用いて充填しても良い。 In this embodiment, the SOG liquid 6 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by a method such as a screen printing method, a spin coating method, or a dispensing method.
　ＳＯＧ液６とシンチレータ基板５の濡れ性が悪い場合には、ＳＯＧ液６を溝内部に充填する前に、ＨＭＤＳ（ヘキサメチルジシラザン）処理や、酸素プラズマ照射などの濡れ性改善の前処理を行なっても良い。さらに、溝内のＳＯＧ液６が過剰な場合には、遠心力を使ってＳＯＧ液６を振り切るか、あるいは、不織布（旭化成せんい（株）製、ベンコット）でＳＯＧ液６を吸い取るなどして、余分なＳＯＧ液６を除去しても良い。 If the wettability between the SOG liquid 6 and the scintillator substrate 5 is poor, a pretreatment for improving wettability such as HMDS (hexamethyldisilazane) treatment or oxygen plasma irradiation is performed before filling the groove with the SOG liquid 6. You can do it. Furthermore, when the SOG liquid 6 in the groove is excessive, the SOG liquid 6 is shaken off using centrifugal force, or the SOG liquid 6 is sucked with a non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott). Excess SOG liquid 6 may be removed.
　ＳＯＧ液６は、粘度が高くなると溝内に充填される際に気泡を巻き込みやすく、均一充填が困難になる。本願発明者は、種々の粘度のＳＯＧ液６を作製して検討を重ねた結果、ＳＯＧ液６の粘度が２０ｃＰ（０．０２０Ｐａ・ｓ）以下であれば気泡を巻き込まずに均一に充填できることを確認し、本実施例では、余裕をもって１５ｃＰ（０．０１５Ｐａ・ｓ）の粘度のＳＯＧ液６を用いた。 When the viscosity of the SOG liquid 6 is increased, bubbles are likely to be involved when filling the groove, and uniform filling becomes difficult. As a result of making and studying SOG liquids 6 having various viscosities, the present inventor has found that if the viscosity of the SOG liquid 6 is 20 cP (0.020 Pa · s) or less, it can be uniformly filled without entraining bubbles. In this example, the SOG liquid 6 having a viscosity of 15 cP (0.015 Pa · s) was used with sufficient margin.
　次に工程３で、ＳＯＧ液６を焼成して酸化シリコンを含む下地材３２を形成した。焼成には電気炉を用い、室温から昇温して４００℃で３０分間保持した。焼成中の酸素濃度は１０００ｐｐｍ以下とした。焼成後、酸化シリコンを含む下地材３２が溝加工面に形成され、溝加工面の面荒れが緩和された。溝加工面上の下地材３２の厚さは０．１～２μｍ、溝加工面の表面粗さＲａは５００ｎｍ以下となった（図３（ｃ））。ここで表面粗さＲａは、原子間力顕微鏡、すなわちＡＦＭ（Ｄｉｇｉｔａｌ　Ｉｎｓｔｒｕｍｅｎｔｓ社製：Ｎａｎｏ　Ｓｃｏｐｅ　ＩＩＩ）を用い、タッピングモードで５μｍ角（５ｍｍ×５ｍｍ）の領域における溝加工面の表面とプローブとの距離を測定し、溝加工面の表面の凹凸の差を算出したものである。 Next, in step 3, the SOG liquid 6 was baked to form a base material 32 containing silicon oxide. An electric furnace was used for firing, and the temperature was raised from room temperature and held at 400 ° C. for 30 minutes. The oxygen concentration during firing was set to 1000 ppm or less. After firing, a base material 32 containing silicon oxide was formed on the groove processing surface, and the surface roughness of the groove processing surface was alleviated. The thickness of the base material 32 on the groove processed surface was 0.1 to 2 μm, and the surface roughness Ra of the groove processed surface was 500 nm or less (FIG. 3C). Here, the surface roughness Ra is measured by using an atomic force microscope, that is, an AFM (Digital Instruments, Nano Scope III), and the surface of the groove processing surface in the region of 5 μm square (5 mm × 5 mm) in the tapping mode and the probe. The distance was measured, and the difference in the irregularities on the surface of the grooved surface was calculated.
　本実施例では、ＳＯＧ液６をシンチレータ基板５の溝内に充填、焼成して、酸化シリコンを含む下地材３２を形成したが、同様に他の無機酸化物を含む下地材を形成しても良い。例えば、酸化チタンの前駆体液をシンチレータ基板５の溝内に充填、焼成して、酸化チタンを含む下地材３２を形成しても良い。他の酸化物の前駆体液を用いる場合でも、溝への充填のし易さから、液の粘度は２０ｃＰ（０．０２０Ｐａ・ｓ）以下であるのが好ましい。 In this embodiment, the SOG liquid 6 is filled in the groove of the scintillator substrate 5 and baked to form the base material 32 containing silicon oxide. However, even if a base material containing another inorganic oxide is formed in the same manner, good. For example, the base material 32 containing titanium oxide may be formed by filling a precursor liquid of titanium oxide into the groove of the scintillator substrate 5 and baking it. Even when another oxide precursor liquid is used, the viscosity of the liquid is preferably 20 cP (0.020 Pa · s) or less from the viewpoint of easy filling into the grooves.
　無機酸化物を含む下地材３２とすることで、次工程において、下地材３２上の有機金属化合物液７から金属が偏析しにくく、均一な金属反射材３３とすることができる。この効果は、無機酸化物を含む下地材３２が有機化合物液７に含まれる有機溶剤と反応しにくく、金属が偏析する起点が生じにくいためと考えられる。
　もっとも、この下地材３２は、次に説明する有機金属化合物液によって溶かされないものを選択する。例えばシリコン樹脂コーティング材を下地材３２として利用すると、有機金属化合物液に、このシリコン樹脂コーティング材が溶解されてしまう。従って、ここではシリコーン（silicone）樹脂を含まず、二酸化ケイ素または他の無機酸化物を含んだＳＯＧ液６等の物質を用い、酸化シリコン、または他の無機酸化物を含んだ下地材３２を形成する。 By setting it as the base material 32 containing an inorganic oxide, in the next process, it is hard to segregate a metal from the organometallic compound liquid 7 on the base material 32, and it can be set as the uniform metal reflector 33. This effect is considered to be because the base material 32 containing an inorganic oxide hardly reacts with the organic solvent contained in the organic compound liquid 7, and the starting point for segregation of the metal hardly occurs.
However, the base material 32 is selected from those that are not dissolved by the organometallic compound liquid described below. For example, when a silicon resin coating material is used as the base material 32, the silicon resin coating material is dissolved in the organometallic compound liquid. Accordingly, here, the base material 32 containing silicon oxide or other inorganic oxide is formed by using a material such as SOG liquid 6 containing silicon dioxide or other inorganic oxide without containing silicone resin. To do.
　次に工程４で、下地材３２を形成したシンチレータ基板５を有機金属化合物液７に浸漬して、シンチレータ基板５の溝内に有機金属化合物液７を充填した。本実施例では、有機金属化合物液７として、有機銀化合物液である藤倉化成（株）製、ナノ・ドータイト　ＸＡ－９０６９を用いた（図３（ｄ））。 Next, in step 4, the scintillator substrate 5 on which the base material 32 was formed was immersed in the organometallic compound solution 7, and the organometallic compound solution 7 was filled in the grooves of the scintillator substrate 5. In this example, an organic silver compound solution manufactured by Fujikura Kasei Co., Ltd., Nano-Dotite XA-9069 was used as the organometallic compound solution 7 (FIG. 3 (d)).
　本実施例では、ディップコーティング法でシンチレータ基板５の溝内部に有機金属化合物液７を充填したが、スクリーン印刷法、スピンコーティング法、ディスペンス法などの方法を用いて充填しても良い。さらに、溝内の有機金属化合物液７が過剰な場合には、遠心力を使って有機金属化合物液７を振り切るか、あるいは、不織布（旭化成せんい（株）製、ベンコット）で有機金属化合物液７を吸い取るなどして、余分な有機金属化合物液７を除去しても良い。 In this embodiment, the organometallic compound liquid 7 is filled in the groove of the scintillator substrate 5 by the dip coating method, but it may be filled by a method such as a screen printing method, a spin coating method, or a dispensing method. Furthermore, when the organometallic compound liquid 7 in the groove is excessive, the organometallic compound liquid 7 is shaken off using centrifugal force, or the non-woven fabric (Asahi Kasei Fibers Co., Ltd., Bencott) is used. The excess organometallic compound liquid 7 may be removed by sucking off the liquid.
　有機金属化合物液７は、粘度が高くなると溝内に充填される際に気泡を巻き込みやすく、均一充填が困難になる。本願発明者は、種々の粘度の有機金属化合物液７を作製して検討を重ねた結果、有機金属化合物液７の粘度が２０ｃＰ（０．０２０Ｐａ・ｓ）以下であれば気泡を巻き込まずに均一に充填できることが確認し、本実施例では、余裕をもって１５ｃＰ（０．０１５Ｐａ・ｓ）の粘度の有機金属化合物液７を用いた。 When the viscosity of the organometallic compound liquid 7 is increased, bubbles are easily involved when filling the groove, and uniform filling becomes difficult. The inventor of the present application made organometallic compound liquids 7 having various viscosities, and as a result of repeated examination, as long as the viscosity of the organometallic compound liquid 7 is 20 cP (0.020 Pa · s) or less, it is uniform without entraining bubbles. In this example, the organometallic compound liquid 7 having a viscosity of 15 cP (0.015 Pa · s) was used with a sufficient margin.
　次に工程５で、有機金属化合物７を焼成してＡｇからなる金属反射材３３を形成した。焼成にはホットプレートを用い、１５０℃で３０分間保持した。焼成前の有機金属化合物７は無色透明であったが、焼成中にＡｇ粒子が析出すると茶色に変色し、その後Ａｇ粒子どうしが結合して銀色の連続膜になった。Ａｇからなる溝内の金属反射材３３の厚さは０．１～数μｍであった（図３（ｅ））。 Next, in step 5, the organometallic compound 7 was fired to form a metal reflector 33 made of Ag. For baking, a hot plate was used and held at 150 ° C. for 30 minutes. The organometallic compound 7 before firing was colorless and transparent, but when the Ag particles were precipitated during firing, the color turned brown, and then the Ag particles were combined to form a silver continuous film. The thickness of the metal reflector 33 in the groove made of Ag was 0.1 to several μm (FIG. 3E).
　図４は、焼成後の金属反射材３３表面のＳＥＭ像であり、図１１は、粒状を目立たせるために図４のコントラストを調整したものである。有機銀が熱分解することで図４（又は図１１）に示されるような連続したＡｇ微細組織が形成された。金属反射材３３表面の光反射率と光透過率を波長５００ｎｍで測定したところ、光反射率は９５．２６％、光透過率は０％であり、放射線検出器１に用いる金属反射材３３として十分な光反射特性であることが確認できた。
　光反射率を向上することで、シンチレータ素子で発光した可視光をシンチレータ素子内部に閉じ込める能力が向上し、該シンチレータ素子で発光した可視光が効率良く半導体光検出素子に導かれることとなって、放射線検出器の出力を高めることができる。 FIG. 4 is an SEM image of the surface of the metal reflector 33 after firing, and FIG. 11 is an image obtained by adjusting the contrast of FIG. 4 to make the grain noticeable. A continuous Ag microstructure as shown in FIG. 4 (or FIG. 11) was formed by thermal decomposition of organic silver. When the light reflectance and light transmittance on the surface of the metal reflector 33 were measured at a wavelength of 500 nm, the light reflectance was 95.26% and the light transmittance was 0%. As the metal reflector 33 used in the radiation detector 1, It was confirmed that the light reflection characteristics were sufficient.
By improving the light reflectance, the ability to confine the visible light emitted by the scintillator element is improved, and the visible light emitted by the scintillator element is efficiently guided to the semiconductor photodetector element. The output of the radiation detector can be increased.
（実施例２）
　次に工程５における焼成温度を異ならせた実施例について説明する。まず、互いに異なる複数の焼成温度に設定したホットプレートで３０分間保持して金属反射材３３を得る。そして各焼成温度での金属反射材３３のＳＥＭ像に対して２ミクロン長さのラインを５本引き、ラインにかかるＡｇ粒の個数をカウントして平均個数を求め、２ミクロンを平均個数で割って粒径を算出した結果を次に示す。
　１４０℃焼成：（連続膜状態でカウント不能）
　１５０℃焼成：カウント３８．４個、平均粒径　５２ｎｍ。
　１６０℃焼成：カウント２５．６個、平均粒径　７８ｎｍ。
　１８０℃焼成：カウント１７．６個、平均粒径１１４ｎｍ。
　２００℃焼成：カウント２８．２個、平均粒径　７１ｎｍ。
　２５０℃焼成：カウント１６．２個、平均粒径１２３ｎｍ。
　この実施例から焼成温度を高くするほど、カウント値は小さくなり、平均粒径が大きくなる傾向があると結論できる。なお、波長５００ｎｍで測定した光反射率は９０％を超え、例えば９３％以上、好ましくは９５％以上であることが、放射線検出器１に用いる金属反射材３３として十分な光反射特性と言える。反射率は、ＳＥＭ像の観察によると、Ａｇ粒間に生じる凹部の面積が大きくなるほど低下するが、この凹部は平均粒径が１００ｎｍ以上になると目立って生じる傾向があることが実験からわかった。したがって上述のような反射率の特性は、平均粒径が１００ｎｍ未満において達成される。また、金属反射膜の組織の粒径が、光の波長５００ｎｍの１／１０程度以下であると、さらに散乱が抑えられ、反射率の向上に寄与することが確かめられている。そこで、より好ましい反射率の特性は、平均粒径が６０ｎｍ未満において達成される。また、組織が接合され、一体化したＡｇ膜となっているのも好ましい。従って上の例から、工程５での焼成温度は、１４０℃を超え、２００℃以下とすることが好適であり、より好ましくは、１４０℃を超え、１６０℃未満、例えば１５０℃程度とすることが好適である。
　図５は、２５０℃のホットプレートで３０分間保持して、有機金属化合物７を焼成した金属反射材３３表面のＳＥＭ像であり、図１２は、図５における粒状が目立つようにコントラストを調整したものである。焼成温度を高くすることで、Ａｇの微細組織は図４（又は図１１）と比較して大きく不揃いな粒子となった。また、粒子間の凹部の面積も多くなっている。金属反射材３３表面の光反射率と光透過率を波長５００ｎｍで測定したところ、光透過率は０％であったものの、光反射率は９２．５４％であり、焼成温度を上げることで金属反射材３３の光反射率は低下することが確認された。
　なお、図４、５（又は図１１，１２）のＳＥＭ像は、同条件で作製した測定用サンプルで観察した。即ち、図２の構成で、金属反射材３３の面に沿うように力を加え続けていき、下地材３２をへき開させて、露出した面をＳＥＭで観察し、Ａｇの微細組織写真を得たものである。 (Example 2)
Next, examples in which the firing temperature in step 5 is varied will be described. First, the metal reflector 33 is obtained by holding for 30 minutes on a hot plate set at a plurality of different firing temperatures. Then, 5 lines having a length of 2 microns are drawn from the SEM image of the metal reflector 33 at each firing temperature, and the average number is obtained by counting the number of Ag grains on the line, and 2 microns is divided by the average number. The results of calculating the particle size are shown below.
140 ° C firing: (Cannot be counted in a continuous film state)
150 degreeC baking: 38.4 counts, average particle diameter 52nm.
160 degreeC baking: 25.6 counts, average particle diameter 78nm.
180 degreeC baking: 17.6 counts, average particle diameter 114nm.
200 degreeC baking: 28.2 counts, average particle diameter 71nm.
250 degreeC baking: 16.2 counts, average particle diameter 123nm.
From this example, it can be concluded that the higher the firing temperature, the smaller the count value and the larger the average particle size. Note that the light reflectance measured at a wavelength of 500 nm exceeds 90%, for example, 93% or more, and preferably 95% or more, can be said to be sufficient light reflection characteristics as the metal reflector 33 used in the radiation detector 1. According to the observation of the SEM image, the reflectance decreases as the area of the recesses formed between the Ag grains increases, but it has been found from experiments that the recesses tend to be conspicuous when the average particle size is 100 nm or more. Therefore, the reflectance characteristics as described above are achieved when the average particle size is less than 100 nm. Further, it has been confirmed that when the particle size of the structure of the metal reflective film is about 1/10 or less of the light wavelength of 500 nm, scattering is further suppressed and it contributes to an improvement in reflectance. Therefore, more preferable reflectance characteristics are achieved when the average particle diameter is less than 60 nm. Moreover, it is also preferable that the tissue is joined to form an integrated Ag film. Therefore, from the above example, the firing temperature in step 5 is preferably 140 ° C. and 200 ° C. or less, more preferably 140 ° C. and less than 160 ° C., for example, about 150 ° C. Is preferred.
FIG. 5 is an SEM image of the surface of the metal reflector 33 obtained by firing the organometallic compound 7 by holding it on a hot plate at 250 ° C. for 30 minutes, and FIG. 12 is adjusted for contrast so that the granularity in FIG. 5 is conspicuous. Is. By increasing the firing temperature, the Ag microstructure became large and irregular in comparison with FIG. 4 (or FIG. 11). Moreover, the area of the recessed part between particle | grains has also increased. When the light reflectance and light transmittance on the surface of the metal reflector 33 were measured at a wavelength of 500 nm, the light transmittance was 0%, but the light reflectance was 92.54%. It was confirmed that the light reflectivity of the reflecting material 33 was lowered.
In addition, the SEM image of FIG. 4, 5 (or FIG. 11, 12) was observed with the sample for a measurement produced on the same conditions. That is, in the configuration of FIG. 2, force was continuously applied along the surface of the metal reflector 33, the base material 32 was cleaved, and the exposed surface was observed with an SEM to obtain a fine microstructure photograph of Ag. Is.
　図６は、波長５００ｎｍで測定した金属反射材３３の光反射率と焼成温度との関係を調べたものである。焼成温度が高くなると、金属反射材３３の光反射率は低下する傾向が見られた。 FIG. 6 shows the relationship between the light reflectance of the metal reflector 33 measured at a wavelength of 500 nm and the firing temperature. As the firing temperature increased, the light reflectance of the metal reflector 33 tended to decrease.
　金属反射材３３の光反射特性が焼成温度に対して変化した原因は、焼成温度に対する金属反射材組織の違いによるものと考えられる。有機金属化合物７を低温で焼成すると有機銀の分解反応が緩やかなため、析出したＡｇ粒子は時間をかけて結合して連続した微細組織になるのに対し、高温で焼成すると有機銀の分解反応速度が速く、連続した微細組織になる前に析出したＡｇ粒子が結合し反応が完了してしまうので、大きく不揃いな粒子の組織になったと考えられる。従って、有機金属化合物７を焼成する温度は、熱分解反応が生じる温度範囲内でできるだけ低温であるのが好ましい。 The reason why the light reflection characteristics of the metal reflector 33 are changed with respect to the firing temperature is considered to be due to the difference in the metal reflector structure with respect to the firing temperature. When the organometallic compound 7 is baked at a low temperature, the decomposition reaction of the organic silver is slow. Therefore, the precipitated Ag particles are bonded over time to form a continuous microstructure. It is thought that the structure of large and irregular particles is formed because the Ag particles precipitated before the formation of a continuous fine structure is fast and the reaction is completed. Accordingly, the temperature for firing the organometallic compound 7 is preferably as low as possible within the temperature range in which the thermal decomposition reaction occurs.
　本実施例では、有機金属化合物液７をシンチレータ基板５の溝内に充填、焼成して、Ａｇからなる金属反射材３３を形成したが、同様にして、金属微粒子ペーストをシンチレータ基板５の溝内に充填、焼成して、金属微粒子焼成体からなる金属反射材３３を形成しても良い。金属微粒子ペーストに用いる金属微粒子は、可視光に対して光反射率の高い、Ａｇ、Ａｕ、Ａｌ、Ｎｉなどを含む金属微粒子を用いるのが好ましい。金属微粒子ペーストを用いる場合でも、溝への充填のし易さから、ペーストの粘度は２０ｃＰ（０．０２０Ｐａ・ｓ）以下であるのが好ましい。 In this embodiment, the metal metal compound liquid 7 is filled in the groove of the scintillator substrate 5 and baked to form the metal reflector 33 made of Ag. Similarly, the metal fine particle paste is put into the groove of the scintillator substrate 5. The metal reflector 33 made of a fired metal fine particle may be formed by filling and firing. The metal fine particles used for the metal fine particle paste are preferably metal fine particles containing Ag, Au, Al, Ni, etc., which have a high light reflectance with respect to visible light. Even when the metal fine particle paste is used, the viscosity of the paste is preferably 20 cP (0.020 Pa · s) or less from the viewpoint of easy filling into the grooves.
　次に工程６で、シンチレータ基板５の溝内に充填材３４を充填した。本実施例では、充填材３４として、（株）スリーボンド製、主剤２０２３、硬化剤２１３１Ｄのエポキシ樹脂を、主剤１００：硬化剤３０（重量比）で混合したものを用い、スクリーン印刷法でシンチレータ基板５の溝内に充填した。本実施例では、スクリーン印刷法を用いてエポキシ樹脂の充填を行ったが、ディスペンス法など、他の充填方法を用いても良い。さらに、エポキシ樹脂の充填は、減圧雰囲気中で行い、エポキシ樹脂内部に気泡が残留しないようにするのがより好ましい。エポキシ樹脂は、電気オーブン中１００℃で１時間加熱して硬化させた（図３（ｆ））。 Next, in step 6, the filler 34 was filled into the grooves of the scintillator substrate 5. In the present embodiment, as the filler 34, a scintillator substrate manufactured by Three Bond Co., Ltd., mixed with epoxy resin of main agent 2023 and curing agent 2131D in a ratio of main agent 100: curing agent 30 (weight ratio) is used. 5 grooves were filled. In this embodiment, the epoxy resin is filled using a screen printing method, but other filling methods such as a dispensing method may be used. Furthermore, it is more preferable that the epoxy resin is filled in a reduced-pressure atmosphere so that no bubbles remain inside the epoxy resin. The epoxy resin was cured by heating at 100 ° C. for 1 hour in an electric oven (FIG. 3 (f)).
　次に工程７で、シンチレータ基板５の表面を研削した。基板表面（溝加工面）を研削することで、シンチレータ基板５表面に付着した、下地材３２、金属反射材３３、充填材３４を除去した（図３（ｇ））。 Next, in step 7, the surface of the scintillator substrate 5 was ground. By grinding the substrate surface (grooved surface), the base material 32, the metal reflector 33, and the filler 34 adhered to the surface of the scintillator substrate 5 were removed (FIG. 3G).
　次に工程８で、上面反射材３５を形成した。本実施例では、上面反射材３５として、（株）スリーボンド製、主剤２０２３、硬化剤２１３１Ｄのエポキシ樹脂を、主剤１００：硬化剤３０（重量比）で混合したものに、平均粒径約０．３μｍの酸化チタン粉末を混練して白色塗料としたものを用い、シンチレータ基板５の表面（溝加工面）にスクリーン印刷法で塗布した。本実施例では、スクリーン印刷法で白色塗料の塗布を行ったが、ディスペンス法など、他の塗布方法を用いても良い。白色塗料は、電気オーブン中１００℃で１時間加熱して硬化させた。（図３（ｈ））。
　ここで工程６までの間に形成した下地材３２及び金属反射材３３は、シンチレータ素子同士の間に形成するのに最適な条件で形成したものである。そのため、上面に形成した下地材及び金属反射材は上面側としては膜が厚く、屈曲した角でクラックが入り、剥離することがある。そこで、工程７においてシンチレータ基板５の上面側に付着した下地材３２及び金属反射材３３を一旦除去し、その後に、工程８で上面反射材３５を形成し直す。 Next, in step 8, a top reflector 35 was formed. In this example, as the upper surface reflecting material 35, an epoxy resin of a main agent 2023 and a curing agent 2131D manufactured by Three Bond Co., Ltd. mixed with a main agent 100: a curing agent 30 (weight ratio) is mixed with an average particle size of about 0.1. A white paint obtained by kneading 3 μm titanium oxide powder was applied to the surface (grooved surface) of the scintillator substrate 5 by screen printing. In this embodiment, the white paint is applied by the screen printing method, but other application methods such as a dispensing method may be used. The white paint was cured by heating in an electric oven at 100 ° C. for 1 hour. (FIG. 3 (h)).
Here, the base material 32 and the metal reflecting material 33 formed up to step 6 are formed under conditions optimal for forming between the scintillator elements. For this reason, the base material and the metal reflector formed on the upper surface are thick on the upper surface side, and cracks may be formed at the bent corners and may be peeled off. Therefore, the base material 32 and the metal reflecting material 33 adhering to the upper surface side of the scintillator substrate 5 are temporarily removed in step 7, and then the upper surface reflecting material 35 is re-formed in step 8.
　本実施例では、上面反射材３５としてエポキシ樹脂と酸化チタン粉末を混練した白色塗料を用いたが、シンチレータ素子３１が発光する可視光を反射する白色粉末、例えば酸化シリコンや酸化アルミニウムの粉末や、酸化チタンの粉末に酸化シリコンをコーティングした粉末を用いた白色塗料を用いても良い。また、白色塗料を用いずに、工程２～工程６と同様の条件で、下地材と金属反射材を順に形成しても良い。 In this example, a white paint kneaded with an epoxy resin and titanium oxide powder was used as the upper surface reflector 35, but white powder that reflects visible light emitted by the scintillator element 31, for example, silicon oxide or aluminum oxide powder, You may use the white coating material which used the powder which coat | coated the silicon oxide to the powder of titanium oxide. Further, the base material and the metal reflecting material may be sequentially formed under the same conditions as in Steps 2 to 6 without using the white paint.
　次に工程９で、シンチレータ基板５の裏面（溝加工面の反対面）を研削した。シンチレータ基板５の裏面に付着した下地材３２と金属反射材３３、充填材３４を除去し、シンチレータ基板５の厚みが、当初の２．０ｍｍから１．７ｍｍになるまで研削したことで、シンチレータ基板５は複数の柱状のシンチレータ素子３１に分離され、シンチレータアレイ３が形成された（図３（ｉ））。 Next, in step 9, the back surface of the scintillator substrate 5 (the surface opposite to the groove processing surface) was ground. The base material 32, the metal reflector 33, and the filler 34 attached to the back surface of the scintillator substrate 5 are removed, and the scintillator substrate 5 is ground until the thickness of the scintillator substrate 5 is reduced from 2.0 mm to 1.7 mm. 5 was separated into a plurality of columnar scintillator elements 31 to form a scintillator array 3 (FIG. 3 (i)).
　最後に工程１０で、複数のシンチレータ素子３１と複数の半導体光検出素子２１とが対向するようにして、シンチレータアレイ３の上面反射材３５の反対面と半導体光検出素子アレイ２の表面とを接着層４を介して接着した。接着層４には、Ｅｐｏｘｙ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社製、Ｅｐｏ－Ｔｅｋ３０１の光学用接着剤を用い、電気炉中８０℃で１時間加熱することで、シンチレータアレイ３と半導体光検出素子アレイ２は硬化して接着し、放射線検出器１が完成した（図３（ｊ））。 Finally, in step 10, the opposite surface of the upper surface reflector 35 of the scintillator array 3 and the surface of the semiconductor light detection element array 2 are bonded so that the plurality of scintillator elements 31 and the plurality of semiconductor light detection elements 21 face each other. Bonded through layer 4. The adhesive layer 4 is made of Epoxy Technologies, Epo-Tek301 optical adhesive, and heated in an electric furnace at 80 ° C. for 1 hour, so that the scintillator array 3 and the semiconductor photodetector array 2 are cured and bonded. And the radiation detector 1 was completed (FIG.3 (j)).
（実施例３）
　次に、本願発明の放射線検出器と、従来の白色塗料の反射材を用いた放射線検出器とのクロストークを比較した。本実施例では、実施例１と同じ製造方法で、２０μｍから１５０μｍの異なるシンチレータ素子間隔の放射線検出器を作製した。また比較例として、本実施例と同じシンチレータ素子サイズで、２０μｍから１５０μｍの異なるシンチレータ素子間隔の放射線検出器を、（株）スリーボンド製、主剤２０２３、硬化剤２１３１Ｄのエポキシ樹脂を、主剤１００：硬化剤３０（重量比）で混合したものに、平均粒径約０．３μｍの酸化チタン粉末を混練した白色塗料反射材を用いて作製した。 (Example 3)
Next, the crosstalk between the radiation detector of the present invention and a conventional radiation detector using a reflective material of white paint was compared. In this example, radiation detectors having different scintillator element intervals of 20 μm to 150 μm were produced by the same manufacturing method as in Example 1. In addition, as a comparative example, a radiation detector having the same scintillator element size as in the present embodiment and a different scintillator element interval of 20 μm to 150 μm was manufactured using Three Bond Co., Ltd., main agent 2023, curing agent 2131D epoxy resin, main agent 100: cured. It was prepared using a white paint reflecting material in which titanium oxide powder having an average particle size of about 0.3 μm was kneaded with the mixture of the agent 30 (weight ratio).
　こうして作製した本実施例、及び比較例の放射線検出器の単一のシンチレータ素子に対し、直径約１００μｍに集光したＸ線を照射し、Ｘ線を照射したシンチレータ素子に取り付けられた半導体光検出素子の出力電流と、隣接するシンチレータ素子に取り付けられた半導体光検出素子の出力電流の比からクロストークを算出した。 Semiconductor photodetection attached to the scintillator element irradiated with X-rays by irradiating the single scintillator elements of the radiation detectors of this embodiment and the comparative example thus manufactured with X-rays condensed to a diameter of about 100 μm. The crosstalk was calculated from the ratio between the output current of the element and the output current of the semiconductor photodetecting element attached to the adjacent scintillator element.
　図７は、シンチレータ素子間隔とクロストークの関係である。白色塗料を光反射材として用いた比較例の放射線検出器は、シンチレータ素子間隔が狭くなるにつれクロストークが増大したが、金属反射材を用いた本実施例の放射線検出器では、シンチレータ素子間隔が狭くなってもクロストークが小さく抑えられている。以上から、本実施例の放射線検出器が比較例の放射線検出器と比較して、クロストークに優位性があることが確認できた。 FIG. 7 shows the relationship between scintillator element spacing and crosstalk. In the radiation detector of the comparative example using white paint as the light reflecting material, the crosstalk increased as the scintillator element interval narrowed. However, in the radiation detector of the present example using the metal reflecting material, the scintillator element interval was Even if it becomes narrow, crosstalk is kept small. From the above, it was confirmed that the radiation detector of the present example was superior in crosstalk as compared with the radiation detector of the comparative example.
１　放射線検出器、
２　半導体光検出素子アレイ、
２１　半導体光検出素子、
３　シンチレータアレイ、
３１　シンチレータ素子、
３２　下地材、
３３　金属反射材、
３４　充填材、
３５　上面反射材、
４　接着層、
５　シンチレータ基板、
６　ＳＯＧ液、
７　有機金属化合物液。
  1 radiation detector,
2 semiconductor photodetector array,
21 semiconductor light detection element,
3 scintillator array,
31 scintillator elements,
32 Base material,
33 metal reflector,
34 filler,
35 top reflector,
4 Adhesive layer,
5 Scintillator board,
6 SOG liquid,
7 Organometallic compound solution.

Claims (12)

  1. 　複数の半導体光検出素子がマトリクス状に配列された半導体光検出素子アレイ上に、複数のシンチレータ素子の各々がその底面を各半導体光検出素子に対向して配列され、シンチレータ素子の底面以外の面に光反射材を設けた放射線検出器であって、
    　前記シンチレータ素子は互いに１００μｍ以下の間隔をもって隣り合って配列され、光反射材は下地材と金属反射材とが順に形成されたものであることを特徴とする放射線検出器。     A plurality of scintillator elements are arranged on a semiconductor photodetection element array in which a plurality of semiconductor photodetection elements are arranged in a matrix, and the bottom surface of each of the scintillator elements is arranged opposite to each semiconductor photodetection element. A radiation detector provided with a light reflecting material,
    The scintillator elements are arranged adjacent to each other with an interval of 100 μm or less, and the light reflecting material is formed by sequentially forming a base material and a metal reflecting material.
  2. 　前記下地材が無機酸化物を含む下地材であることを特徴とする請求項１に記載の放射線検出器。 The radiation detector according to claim 1, wherein the base material is a base material containing an inorganic oxide.
  3. 　前記無機酸化物が酸化シリコンを含むことを特徴とする請求項２に記載の放射線検出器。 The radiation detector according to claim 2, wherein the inorganic oxide contains silicon oxide.
  4. 　前記無機酸化膜が酸化チタンを含むことを特徴とする請求項２に記載の放射線検出器。 3. The radiation detector according to claim 2, wherein the inorganic oxide film contains titanium oxide.
  5. 　前記酸化シリコンを含む無機酸化物がＳＯＧ（Spin On Glass）の焼成物であることを特徴とする請求項３に記載の放射線検出器。 4. The radiation detector according to claim 3, wherein the inorganic oxide containing silicon oxide is a fired product of SOG (Spin On Glass).
  6. 　前記酸化チタンを含む無機酸化物が酸化チタン前駆体の焼成物であることを特徴とする請求項４に記載の放射線検出器。 The radiation detector according to claim 4, wherein the inorganic oxide containing titanium oxide is a fired product of a titanium oxide precursor.
  7. 　前記金属反射材がＡｇ、Ａｕ、Ａｌ、Ｎｉの少なくとも一つを含む有機金属化合物の焼成物であることを特徴とする請求項１に記載の放射線検出器。 The radiation detector according to claim 1, wherein the metal reflector is a fired product of an organometallic compound containing at least one of Ag, Au, Al, and Ni.
  8. 　シンチレータ基板の片面に格子状で幅１００μｍ以下の加工溝を形成する工程、
    　前記加工溝側面に無機酸化物の下地材と金属反射材とを順に形成する工程、
    　前記シンチレータ基板の溝加工面と反対の面を加工して複数のシンチレータ素子からなるシンチレータアレイを形成する工程、
    　複数の半導体光検出素子からなる半導体光検出素子アレイと、前記シンチレータアレイとを、それぞれの半導体光検出素子とシンチレータ素子とが対向するように接着する工程、
    を備えたことを特徴とする放射線検出器の製造方法。     A step of forming a processing groove having a width of 100 μm or less on one side of the scintillator substrate,
    A step of sequentially forming an inorganic oxide base material and a metal reflector on the processed groove side surface;
    Forming a scintillator array comprising a plurality of scintillator elements by processing a surface opposite to the groove processing surface of the scintillator substrate;
    Bonding a semiconductor light detection element array composed of a plurality of semiconductor light detection elements and the scintillator array so that the respective semiconductor light detection elements and the scintillator elements face each other;
    A method of manufacturing a radiation detector, comprising:
  9. 　無機酸化物の前駆体溶液を、ディップコーティング法、スクリーン印刷法、スピンコーティング法、ディスペンス法のいずれかの方法で前記加工溝に充填し焼成して、前記下地材を形成することを特徴とする請求項８に記載の放射線検出器の製造方法。 An inorganic oxide precursor solution is filled in the processed groove by one of a dip coating method, a screen printing method, a spin coating method, and a dispensing method, and baked to form the base material. The manufacturing method of the radiation detector of Claim 8.
  10. 　前記無機酸化物の前駆体溶液の粘度を２０ｃＰ以下とすることを特徴とする請求項９に記載の放射線検出器の製造方法。 The method of manufacturing a radiation detector according to claim 9, wherein the viscosity of the inorganic oxide precursor solution is 20 cP or less.
  11. 　有機金属化合物溶液を、ディップコーティング法、スクリーン印刷法、スピンコーティング法、ディスペンス法のいずれかの方法で前記下地材を形成した前記加工溝に充填し焼成して、前記金属反射材を形成することを特徴とする請求項９に記載の放射線検出器の製造方法。 Filling the processed groove in which the base material is formed by any one of a dip coating method, a screen printing method, a spin coating method, and a dispensing method and firing the solution to form the metal reflector. The manufacturing method of the radiation detector of Claim 9 characterized by these.
  12. 　前記有機金属化合物溶液の粘度を２０ｃＰ以下とすることを特徴とする請求項１１に記載の放射線検出器の製造方法。
          12. The method of manufacturing a radiation detector according to claim 11, wherein the viscosity of the organometallic compound solution is 20 cP or less.
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