JP5360281B2 - Manufacturing method of radiation detector using gas amplification - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a novel pixel type radiation detector with a satisfactorily high detection sensitivity. <P>SOLUTION: An insulation member has a first electrode layer formed over a first surface and a second electrode layer formed over a second surface. The insulation member is subjected to a first exposure developing processing on the first electrode layer to form plural processing openings in the first electrode layer. The insulation member is irradiated with an energy ray via the plural processing openings; or subjected to photosensitive photolithography to form through holes in a thickness direction of the insulation member. Subsequently, the through holes are subjected to via-hole-filling plating to fill the through holes and to form a metal plating layer. The first electrode layer is subjected to a second exposure developing processing to form circular openings in the metal plating layer on the first electrode layer to thereby form a first electrode pattern. The front ends of the metal plating layer are subjected to sharpening processing to form convex portions of the metal plating layer the top of which is sharpened, and a second electrode pattern of the second electrode layer. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing a radiation detector using gas amplification by a pixel-type electrode.

  Conventionally, a pixel type radiation detector has been used as a radiation detector utilizing gas amplification. In this radiation detector, for example, a strip-like cathode electrode is formed on the surface of a double-sided printed circuit board, an anode strip is formed on the back surface, and openings are formed in the strip-like cathode electrode at regular intervals. A cylindrical anode electrode connected to the anode strip on the back, that is, a pixel electrode is formed at the center of the opening.

  The radiation detector is disposed in a mixed gas of He and methane, for example. Further, for example, a voltage of +600 V is applied to the pixel electrode.

  In the radiation detector, when predetermined radiation is incident on the detector, the gas is ionized to generate electrons, and the electrons are applied between the strip-like cathode electrode and the pixel electrode. Electron avalanche amplification is caused by a large electric field and a strong electric field generated due to the shape (shape anisotropy) of the pixel electrode as a point electrode. On the other hand, positive ions generated by the electron avalanche amplification drift toward the surrounding strip-like cathode electrode.

  As a result, holes and electrons are charged in the strip-like cathode electrode and the pixel electrode, respectively. By detecting the positions of the strip-like cathode electrode and the pixel electrode where the charges are generated, the incident position of the radiation in the detector can be specified, and the radiation can be detected (Patent Document). 1).

  In the radiation detector described above, when the voltage applied to the pixel electrode is increased, the intensity of the generated electric field also increases, and the above-described electron avalanche amplification becomes significant. Therefore, the radiation detector generates the strip-shaped cathode electrode and the pixel electrode. The amount of charge to be increased increases, and the radiation detection sensitivity is improved. On the other hand, when the voltage applied to the pixel electrode is increased, the pixel electrode may be damaged due to abnormal discharge caused by the shape of the pixel electrode or foreign matter in the atmosphere. Further, when the voltage applied to the pixel electrode is reduced, the above-described abnormal discharge is reduced, but the degree of the above-mentioned electronic avalanche amplification is also reduced, and the radiation detection sensitivity is lowered.

  From such a point of view, instead of adjusting the magnitude of the voltage applied to the pixel electrode, attempts have been made to narrow the pixel electrode and improve the strength of the generated electric field. However, since the pixel electrode is formed by via fill plating in a through hole formed in the printed board, the through hole needs to be narrowed in order to narrow the pixel electrode. On the other hand, if the through hole is narrowed, the via fill plating cannot be performed uniformly in the through hole, and a uniform pixel electrode cannot be formed, and problems such as abnormal discharge and dielectric breakdown occur in the pixel electrode. Arise. Therefore, the narrowing of the pixel electrode is naturally limited depending on the manufacturing method.

  As a result, at present, the applied voltage to the pixel electrode cannot be sufficiently improved, and the pixel electrode cannot be sufficiently narrowed, and the detection sensitivity of the pixel-type radiation detector is sufficiently improved. There was a problem that I could not.

JP 2002-6047

  An object of the present invention is to provide a method for manufacturing a novel pixel-type radiation detector having sufficiently high detection sensitivity.

In order to achieve the above object, the present invention provides:
Forming a first electrode layer on the first surface of the insulating member, and forming a second electrode layer on a second surface opposite to the first surface of the insulating member;
Subjecting the first electrode layer to a first exposure and development process to form a plurality of processing openings in the first electrode layer;
Irradiating the insulating member with energy rays through the plurality of processing openings of the first electrode layer, and forming a through hole in the thickness direction of the insulating member;
Applying via fill plating in the through hole and forming a metal plating layer so as to embed the through hole; and
A second exposure and development process is performed on the first electrode layer, and a circular opening centered on the metal plating layer is formed in the first electrode layer to form a first electrode pattern. And a process of
A step of narrowing a tip of the metal plating layer, and forming a second electrode pattern consisting of a convex portion with a narrowed tip made of the metal plating layer and the second electrode layer;
It is related with the manufacturing method of a radiation detector characterized by comprising.

  The inventors of the present invention have intensively studied to achieve the above object. As a result, the conventional pixel-type radiation detector has been conceived to narrow the tip of the convex portion in the second electrode pattern constituting the pixel electrode. In the case of a radiation detector using gas amplification, it is required to cause an electron avalanche amplification when radiation enters the detector. In order to cause the electron avalanche amplification, the first electrode pattern and the convex It is necessary to generate a strong electric field by applying a large voltage between the convex portions and / or narrowing the convex portions.

  However, the narrowing of the convex portion contributes to the generation of the electric field because the convex portion functions as a point electrode. From this viewpoint, in the present invention, only the tip of the convex portion is used. And a function as a point electrode is added to the convex part to generate the above-described strong electric field.

  As described above, the narrowing of the convex portion is extremely difficult due to its formation method (via fill plating method). However, in order to narrow the tip of the convex portion, According to the manufacturing method, after performing the usual via fill plating to form the convex portion, it can be easily realized by separately performing a narrowing process on the tip of the convex portion.

  According to the present invention, the tip of the convex portion of the second electrode pattern that functions as a pixel electrode is narrowed, and the function as a point electrode is increased in the convex portion, so that the first electrode Even if the voltage applied between the pattern and the convex portion is not increased so much, a strong electric field is generated around the convex portion based on the increased function of the convex portion as a point electrode. Can do. Therefore, even when the voltage applied between the electrodes does not increase so much when radiation enters the detector, electron avalanche amplification can be caused and the radiation can be detected.

  Moreover, since a large voltage is not applied to the convex portion, abnormal discharge in the convex portion can be prevented, and damage to the convex portion can be prevented.

  Also in the present invention, since the holes and electrons are charged in the convex portions of the first electrode pattern and the second electrode pattern, respectively, the convex portions where charges are generated, that is, By detecting the position of the pixel electrode, the incident position of the radiation at the detector can be specified, and the radiation can be detected.

  As described above, according to the present invention, it is possible to provide a method for manufacturing a novel pixel-type radiation detector having sufficiently high detection sensitivity.

It is a top view which shows schematic structure in an example of the radiation detector of this invention. It is a figure which expands and shows the pixel type radiation detector shown in FIG. It is sectional drawing which expands and shows the pixel electrode peripheral part of the said pixel-type radiation detector. It is a modification of the radiation detector regarding FIGS. Similarly, it is a modification of the radiation detector regarding FIGS. Similarly, it is a modification of the radiation detector regarding FIGS. It is process drawing in an example of the manufacturing method of this invention. Similarly, it is process drawing in an example of the manufacturing method of the present invention. Similarly, it is process drawing in an example of the manufacturing method of the present invention. Similarly, it is process drawing in an example of the manufacturing method of the present invention. Similarly, it is process drawing in an example of the manufacturing method of the present invention. Similarly, it is process drawing in an example of the manufacturing method of the present invention.

  Hereinafter, the features and other advantages of the present invention will be described based on embodiments for carrying out the invention.

  FIG. 1 is a plan view showing a schematic configuration of an example of a radiation detector manufactured by the method of the present invention, and FIG. 2 is an enlarged view of the pixel-type radiation detector shown in FIG. These are sectional drawings which expand and show the pixel electrode peripheral part of the pixel-type radiation detector.

  As shown in FIG. 1, the radiation detector 10 of this example includes a pixel-type radiation detector 20 and a current detection circuit and the like (not shown). As shown in FIG. 2, the pixel-type radiation detector 20 includes a detection panel 21 and an electrode plate 22 provided so as to face each other above the detection panel 21.

  As shown in FIG. 2, the detection panel 21 includes a first electrode pattern 212 having a plurality of circular openings 212 </ b> A formed on the main surface 211 </ b> A of the insulating member 211, and a back surface 211 </ b> B of the insulating member 211. And a second electrode pattern 213 formed on the substrate. The second electrode pattern 213 has a convex portion 214 that penetrates through the insulating member 211 and is exposed at the substantially central portion of the opening 212A of the first electrode pattern 212. The convex portion 214 constitutes a pixel electrode. Further, the tip 214A of the convex portion 214 is narrowed.

  In addition, in the detection panel 21 of the pixel-type radiation detector 20 shown in FIG. 2, a total of eight openings 212A are formed in the first electrode pattern 211A and arranged in two rows by four. The tips of the convex portions 214 are exposed in the openings 212A, so that a total of eight detection electrodes are formed. However, the number and arrangement method of the detection electrodes (the number and arrangement method of the openings 212A and the convex portions 214 in the first electrode pattern 21) can be arbitrarily set as necessary.

  Although not clearly shown in the drawing, the second electrode pattern 213 is also patterned in a strip shape in a direction substantially perpendicular to the arrangement direction of the first electrode patterns 212. However, the second electrode pattern 213 may be patterned in any direction as long as it is not parallel to the first electrode pattern 212.

  The thickness t1 of the insulating member 211 can be set to 20 μm to 100 μm, for example. Further, the thickness t2 of the first electrode pattern 212 and the thickness t3 of the second electrode pattern 213 can be set to 5 μm to 18 μm, respectively. Furthermore, the height L1 of the convex portion 214 can be the sum of the thickness t1 of the insulating member 211 and the thickness t2 of the first electrode pattern 212 due to the manufacturing method described below. The diameter D1 of the opening 212A can be set to, for example, 80 μm to 300 μm, and the distance D2 between the end surface of the tip 214A of the convex portion 214 and the end surface of the opening 212A of the first electrode pattern 212 is, for example, It can be set to 20 μm to 130 μm.

  The first electrode pattern 212 and the second electrode pattern 213 can be made of a conductive member such as copper, gold, silver, nickel, or aluminum. Moreover, the insulating member 211 can be comprised from the film or sheet | seat of a thermosetting resin.

  A predetermined voltage, for example, a voltage of about 600V is applied between the first electrode pattern 212 and the second electrode pattern 213. In this case, the first electrode pattern 212 can be a cathode and the second electrode pattern 213 can be an anode, or the first electrode pattern 212 can be an anode and the second electrode pattern 213 can be a cathode. it can.

  However, in order to cause the electron avalanche amplification of electrons described below, the shape of the convex portion 214 of the second electrode pattern 213 plays an extremely important role, so the first electrode pattern It is preferable that 212 is a cathode and the second electrode pattern 213 is an anode. Therefore, in the following, a case where the first electrode pattern 212 is a cathode and the second electrode pattern 213 is an anode will be described.

  A space between the detection panel 21 and the electrode plate 22 is filled with a predetermined gas, for example, a mixed gas of He and methane. Furthermore, the electrode plate 22 is biased to a predetermined voltage.

  When radiation is incident on the radiation detector 10 shown in FIG. 1, the radiation collides with the gas, thereby ionizing the gas and generating electrons. The generated electrons receive the bias voltage of the electrode plate 22 in the pixel-type radiation detector 20 and are guided to the detection panel 21, and between the first electrode pattern 212 and the convex portion 214 of the second electrode pattern 213. And a large electric field generated due to the shape of a point electrode in which the tip 214A of the convex portion 214 is constricted, causes an electron avalanche and accumulates in the convex portion 214. On the other hand, positive ions generated by the electron avalanche drift from the convex portion 214 toward the surrounding first electrode pattern 212.

  As a result, holes and electrons are charged in the convex portions 214 of the first electrode pattern 212 and the second electrode pattern 213, respectively, so that the positions of the convex portions 214, that is, the pixel electrodes are not shown. By detecting with the detection circuit, the incident position of the radiation in the pixel radiation detector 20 can be specified, and the radiation can be detected.

  In this example, since the tip 214A of the convex portion 214 of the second electrode pattern 213 that functions as a pixel electrode is narrowed to increase the function of the convex portion 214 as a point electrode, the first electrode pattern 212 is increased. Even when the voltage applied between the convex portion 214 and the convex portion 214 is about 600 V as described above, a strong electric field around the convex portion 214 is obtained due to the increased function of the convex portion 214 as a point electrode. Can be generated. Accordingly, even when the voltage applied between the electrodes does not increase so much when radiation enters the radiation detector 10, an electron avalanche can be generated, and the detection of the radiation is performed with high sensitivity. Can do.

  In addition, since a large voltage is not applied to the convex portion 214, abnormal discharge in the convex portion 214 can be prevented, and damage to the convex portion 214 can be prevented.

  In addition, as described above, the tip 214A of the convex portion 214 can generate a huge electric field due to an increase in function as a point electrode by being constricted, and can prevent abnormal discharge accompanying an increase in applied voltage. If possible, the size, shape, etc. are not particularly limited. In this example, the tip 214A of the convex portion 214 is narrowed in a taper shape and has a truncated cone shape. In this case, when the diameter d1 of the convex portion 214 is 15 μm to 70 μm, the diameter d2 of the tip 214A can be in the range of 4 μm to 36 μm. The length L2 of the tip 214 can be 10 μm to 40 μm.

  The tip 214A of the convex portion 214 is narrowed by a predetermined narrowing process. As will be described in detail in the following manufacturing method, this depends on the method of forming the convex portion 214. That is, the convex portion 214 is formed by performing via fill plating on the through-hole formed in the insulating member 211, but the convex portion 214 must be formed as a uniform conductive layer. This is because if the portion 214 is narrowed, the uniformity is impaired, and a uniform conductive layer cannot be obtained.

  Therefore, after forming the convex part 214 as a uniform conductive layer by the via fill plating method, the tip 214A is narrowed by performing the narrowing process described above.

  As shown in FIG. 3, generally, the insulating member 211 around the tip 214A is partially cut by the narrowing process described above to form a gap 211C.

  FIGS. 4-6 is a modification of the radiation detector 10 regarding FIGS. In these modified examples, the shape of the tip 214A of the convex portion 214 in the second electrode pattern 213 is changed. Note that the same reference numerals are used for similar and identical components.

  In FIG. 4, the tip 214 </ b> A of the convex portion 214 is narrowed like a taper as in FIG. 3, but it is not a truncated cone shape but a hemispherical shape as shown in FIG. 3. In FIG. 5, the tip 214 </ b> A of the convex portion 214 is narrowed in a step shape, and this portion has a cylindrical shape. Further, in FIG. 6, the tip 214 </ b> A of the convex portion 214 is similarly narrowed in a step shape, and this portion has an inverted truncated cone shape. Also in these modified examples, the tip 214A of the convex portion 214 is narrowed, so that a huge electric field can be generated by increasing the function as a point electrode.

  Therefore, even if the voltage applied between the first electrode pattern 212 and the second electrode pattern 213 is not increased so much, the above-described electron gas amplification can be caused, and radiation can be detected with high sensitivity. become able to.

  The inverted frustoconical shape means a shape in which the truncated cone shape shown in FIG.

  The shapes shown in FIGS. 3, 5 and 6 can be easily obtained mainly when the narrowing is performed by laser processing, and the shapes shown in FIG. 4 are mainly performed by laser processing and etching. Can be easily obtained in some cases.

  Next, the manufacturing method of the radiation detector of this invention is demonstrated. 7-12 is process drawing in an example of the manufacturing method of this invention.

  First, as shown in FIG. 7, the first electrode layer 217 made of a conductive member such as copper and the like are formed on the main surface 211A and the back surface 211B of the insulating member 211 made of, for example, a thermosetting resin film or sheet. Two electrode layers 218 are formed. Next, as shown in FIG. 8, the first electrode layer 217 is subjected to photolithography to form a plurality of processing openings 217A in the first electrode layer 217, and at the same time, the electrode layer 218 is formed into a strip shape.

  Next, as shown in FIG. 9, the insulating member 211 is irradiated with energy rays through the plurality of processing openings 217 </ b> A of the first electrode layer 217, thereby forming a through hole 211 </ b> H in the thickness direction of the insulating member 211. . For example, a laser beam can be used as the energy beam, and a carbon dioxide laser is preferably used. This gas laser processes only the insulating member 211 from its wavelength characteristics, and does not process the electrode layer 218. Note that the through hole 211H may be formed by performing photosensitive photolithography instead of the energy beam irradiation.

  Next, as shown in FIG. 10, via fill plating is performed in the through hole 211H, and the metal plating layer 219 is formed so as to bury the through hole 211H. After that, as shown in FIG. 11, the first electrode layer 217 is subjected to a photolithography process again to form a circular opening 212 around the metal plating layer 219 in the first electrode layer 217. Then, the first electrode pattern 212 is formed.

  Next, as shown in FIG. 12, the tip of the metal plating layer 219 is narrowed by laser light irradiation, etching, or the like, and the convex portion 214 made of the metal plating layer 219 and the second electrode layer are constricted at the tip 214A. A second electrode pattern 213 made of 218 is formed.

  As described above, since the metal plating layer 219 to be the convex portion 214 is formed by the above-described via fill plating, it is necessary to reduce the diameter of the through hole 211H in order to narrow the convex portion 214. is there. When the hole diameter of the through-hole 211H is reduced, it becomes impossible to perform via fill plating well, and it becomes difficult to form a uniform metal plating layer 219. As a result, even if the convex portion 214 can be narrowed, the uniformity cannot be ensured, and abnormal discharge or dielectric breakdown occurs.

  However, in the manufacturing method of this example, as described above, the convex portion 214 itself is not narrowed, but only the tip thereof is narrowed by laser processing or the like. It can be avoided.

  Since the detection panel 21 is formed as described above, the electrode plate 22 and the like are thereafter disposed facing each other, filled with the mixed gas therebetween, and further subjected to casing as shown in FIG. A simple radiation detector can be obtained.

  The present invention has been described in detail based on the above specific examples. However, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Radiation detector 20 Pixel type radiation detector 21 Detection panel 22 Electrode plate 211 Insulating member 212 1st electrode pattern 212A Circular opening part of 1st electrode pattern 213 2nd electrode pattern 214 Convex of 2nd electrode pattern 214A The tip of the convex part of the second electrode pattern

Claims (3)

Forming a first electrode layer on the first surface of the insulating member, and forming a second electrode layer on a second surface opposite to the first surface of the insulating member;
Subjecting the first electrode layer to a first exposure and development process to form a plurality of processing openings in the first electrode layer;
Through holes are formed in the thickness direction of the insulating member by irradiating the insulating member with energy rays through the plurality of processing openings of the first electrode layer or by performing photosensitive photolithography. Process,
Applying via fill plating in the through hole and forming a metal plating layer so as to embed the through hole; and
A second exposure and development process is performed on the first electrode layer, and a circular opening centered on the metal plating layer is formed in the first electrode layer to form a first electrode pattern. And a process of
A step of narrowing a tip of the metal plating layer, and forming a second electrode pattern consisting of a convex portion with a narrowed tip made of the metal plating layer and the second electrode layer;
The manufacturing method of a radiation detector characterized by comprising.   The method of manufacturing a radiation detector according to claim 1, wherein the constriction processing is laser processing.   The method of manufacturing a radiation detector according to claim 1, wherein the narrowing process is an etching process.

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