JP2012103036A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector that prevents deterioration in characteristics of a semiconductor element.SOLUTION: In a radiation detector, a CdTe semiconductor element 2 is bonded to a base plate 11 by means of a conductive adhesive. The CdTe semiconductor element 2 includes a chamfered part 23 and a chamfered part 26 in which chamfering treatment is applied to end parts of surfaces thereof facing the base plate 11, thereby being able to avoid contact with the base plate 11 when the CdTe semiconductor element 2 is mounted and even when warpage occurs in the base plate 11 due to residual stress or the like caused by adhesion.

Description

  The present invention relates to a radiation detector.

  As a conventional semiconductor radiation detector, there is known a semiconductor radiation detector in which four semiconductor elements formed in a block shape on the surface side of a substrate are provided in a matrix of 2 rows and 2 columns with almost no gap (for example, , See Patent Document 1).

  The semiconductor radiation detector described in Patent Document 1 can improve resolution by arranging a plurality of semiconductor elements without gaps.

JP 2005-26419 A

  However, the semiconductor radiation detector according to Patent Document 1 does not consider the warpage of the substrate due to the residual stress caused by bonding the semiconductor element to the substrate and the damage of the semiconductor element due to the external force during assembly. May deteriorate.

  Accordingly, an object of the present invention is to provide a radiation detector that suppresses deterioration of characteristics of a semiconductor element.

  In order to achieve the above object, the present invention provides a radiation detection comprising a substrate and a semiconductor element that detects radiation and has a chamfered portion on which at least one side of the surface facing the substrate is chamfered. A vessel is provided.

  Moreover, it is preferable that said semiconductor element has a detection surface which detects a radiation, and a chamfer part is formed in the edge | side perpendicular | vertical to the detection surface of the surface facing a board | substrate.

  The semiconductor element has an electrode on a surface facing the substrate, and the chamfered portion includes a first chamfered portion formed on the semiconductor element, and a second chamfered portion formed on the electrode. It is preferable to consist of.

  Moreover, it is preferable that said chamfering part is a slope.

  The radiation detector according to the present invention can provide a radiation detector that suppresses deterioration of characteristics of a semiconductor element.

FIG. 1 is a perspective view of the radiation detector according to the first exemplary embodiment. 2A is a view of a surface of the CdTe element according to the first embodiment facing the substrate, FIG. 2B is a bottom view of the CdTe element, and FIG. 2C is a side view of the CdTe element. FIG. FIG. 3A is a schematic diagram regarding the mounting of the CdTe element according to the comparative example, and FIG. 3B is a schematic diagram regarding the mounting of the CdTe element according to the first embodiment. FIG. 4A is a top view of the radiation detector according to the first embodiment, and FIG. 4B is an enlarged view of the vicinity of the end of the radiation detector. FIGS. 5A to 5D are schematic views showing a CdTe element cutting-out process according to the first embodiment. FIG. 6 is a perspective view of a CdTe element according to the second embodiment.

[Summary of embodiment]
A radiation detector according to an embodiment includes a substrate and a semiconductor element that has a chamfered portion that detects radiation and is chamfered on at least one side of a surface facing the substrate.

[First Embodiment]
(Outline of configuration of radiation detector 1)
FIG. 1 is a perspective view of the radiation detector according to the first exemplary embodiment. 2A is a view of a surface of the CdTe element according to the first embodiment facing the substrate, FIG. 2B is a bottom view of the CdTe element, and FIG. 2C is a side view of the CdTe element. FIG. In addition, each figure shown below is schematic and the relationship of the magnitude | size between each structural member may differ from an actual thing.

  The radiation detector 1 according to the present embodiment is a radiation detector that detects radiation such as γ rays and X rays. In FIG. 1, the radiation 6 enters from the upper side to the lower side of the page. That is, the radiation 6 propagates along the direction from the CdTe element 2 as a semiconductor element of the radiation detector 1 toward the card holder 14 and enters the radiation detector 1. In the radiation detector 1, the radiation 6 enters the detection surface 20 a of the CdTe element 2 (that is, the surface facing upward in FIG. 1). Therefore, the side surface of the CdTe element 2 is a detection surface 20a for the radiation 6. Thus, the radiation detector in which the side surface of the semiconductor element is the detection surface 20a for the radiation 6 is referred to as an edge-on type radiation detector. The radiation detector 1 detects the radiation 6 through a collimator having a plurality of openings through which the radiation 6 incident along a specific direction (for example, a direction from the subject toward the radiation detector 1) passes. The radiation detector 1 for an edge-on type radiation detection apparatus configured by arranging a plurality of radiation detectors 1 arranged side by side can be configured. Further, the radiation detector 1 according to the present embodiment has a card shape.

  In addition, the radiation detector 1 which concerns on this Embodiment can be equipped with a collimator. The radiation detector 1 can also be used without a collimator. When using a collimator, a porous parallel collimator, a pinhole collimator, or the like can be used. In this embodiment, as an example, a porous parallel collimator is used.

  The substrate 11 is a thin substrate (for example, a glass epoxy substrate such as FR4) on which a conductive thin film (for example, copper foil) made of a conductive material such as a metal conductor is formed, and is made of an insulating material such as a solder resist. It is formed sandwiched between insulating layers.

  As shown in FIG. 1, the substrate 11 has four CdTe elements 2 on the first end side of the substrate 11, four on one surface of the substrate 11 and four on the other surface. It can be mounted so as to be plane-symmetric. Further, the substrate 11 has a width on the first end side on which each of the plurality of CdTe elements 2 is mounted, and a width of the second end opposite to the first end side on which the plurality of CdTe elements 2 are mounted. It is formed wider than the part side. The substrate 11 is supported by the card holder 13 and the card holder 14 on the second end side. Further, a card edge portion 112 provided with a plurality of patterns 111 capable of electrically connecting the radiation detector 1 and an external control circuit is provided on the second end side. In addition, a plurality of CdTe elements 2 and a plurality of electronic components such as resistors and capacitors that are electrically connected via the element connection portions are mounted between the element connection portion described later and the card edge portion 112. An electronic component mounting unit 110 is provided. Note that an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like can be mounted on the electronic component mounting unit 110.

  In addition, the board | substrate 11 has a length of about 40 mm in the wide direction, ie, a longitudinal direction, as an example. The substrate 11 extends from the end of the wide portion to the end of the narrowed portion, that is, from the end of the portion where the element connection portion is provided to the end of the card edge portion 112. In FIG. 2, the length is about 20 mm.

  Further, the substrate 11 extends from the surface of the substrate 11 along the normal direction of the surface between the element connection portion and the electronic component mounting portion 110 that are electrically connected to the respective electrodes 4a to 4h of the CdTe element 2. And a plurality of columnar substrate terminals 11a to 11d formed by protruding. In the present embodiment, as an example, four columnar substrate terminals 11 a to 11 d are formed on one surface of the substrate 11. The substrate terminals 11a to 11d can also be formed in a columnar shape with a rectangular cross section.

  In addition, each of the element connection portion, the board terminal 11a to the board terminal 11d, and the electronic component mounting section 110 has a conductive thin film positioned at the center in the thickness direction of the board 11 as a symmetry plane, and It is provided on each of the surface and the other surface. Here, the element connection portion and the electronic component mounting portion 110 are provided at substantially symmetrical positions on one surface and the other surface, respectively, with the substrate as a symmetry plane. On the other hand, the plurality of substrate terminals 11a to 11d are provided at positions that alternate between one surface and the other surface.

  The substrate 11 is sandwiched and supported by the card holder 13 and the card holder 14. The card holder 13 and the card holder 14 are formed to have the same shape, and the protrusion 17 of the card holder 14 is fitted into a grooved hole (not shown) of the card holder 13. The board | substrate 11 is supported by the projection part 19 which the card holder 13 has fitted in the grooved hole 18 which has.

  The radiation detector 1 has elastic member mounting portions 15 on both side surfaces in the longitudinal direction. The elastic member mounting portion 15 is an elastic member 16 that presses and fixes the radiation detector 1 to the radiation detector stand when the radiation detector 1 is inserted into the radiation detector stand that supports the plurality of radiation detectors 1. Is provided. The radiation detector stand has a connector into which the card edge portion 112 is inserted. In the radiation detector 1, the card edge portion 112 is inserted into the connector, and the connector and the pattern 111 are electrically connected. Thus, the circuit is electrically connected to a control circuit as an external electric circuit, an external power supply line, a ground line, and the like.

  As shown in FIGS. 1 and 2B, the radiation detector 1 includes a plurality of substrates provided on the substrate 11 and the electrode pattern 30 of each CdTe element 2 on the opposite side of the substrate 11 of the pair of CdTe elements 2. A flexible substrate 12 having a wiring pattern (not shown) that electrically connects each of the terminal 11a to the substrate terminal 11d is further provided.

  The flexible substrate 12 is provided on both the one CdTe element 2 side of the pair of CdTe elements 2 and the other CdTe element 2 side (in the present embodiment, one CdTe of the four pairs of CdTe elements 2). A flexible substrate 12 is provided on each of the element 2 side and each of the other CdTe element 2 side). Then, one ends of the plurality of wiring patterns of the flexible substrate 12 are electrically connected to the substrate terminals 11a to 11d, respectively.

(Details of CdTe element)
As shown in FIGS. 2A to 2C, the CdTe element 2 has a rectangular parallelepiped shape, and is spaced from the upper surface of the paper surface of FIG. By forming the plurality of groove portions 28a to 28g so as to face, eight pixels 27a to 27h are formed. That is, each portion of the CdTe element 2 divided by the groove 28a to the groove 28g corresponds to one pixel (pixel) that detects radiation. Thereby, one CdTe element 2 has a plurality of pixels. When one radiation detector 1 includes eight CdTe elements 2 (four pairs of CdTe elements 2) and one CdTe element 2 includes eight pixels 27a to 27h, one radiation detector. 1 will have a resolution of 64 pixels. The number of pixels of one CdTe element 2 can be increased or decreased by increasing or decreasing the number of grooves 28a to 28g. Therefore, since the element connection portion is formed for each pixel, 32 element connection portions are formed on one surface of the substrate 11.

  As shown in FIG. 2A, electrodes 4a to 4h are formed on the pixels 27a to 27h, respectively. The electrodes 4 a to 4 h are electrically connected to an element connection portion formed on the substrate 11.

  Moreover, the width | variety of the groove part 28a-the groove part 28g is 0.2 mm as an example, and is formed in 2 mm space | interval. The thickness of the CdTe element 2 is 2 mm as an example. Further, the width of one pixel is formed to have a width equal to the thickness of the CdTe element 2. In the present embodiment, the width of each of the groove portions 28a to 28g of each of the plurality of CdTe elements 2 can be determined according to, for example, the opening diameter of the collimator or the thickness of the wall separating the plurality of openings.

  The CdTe element 2 has a detection surface 20a on the upper side of the paper surface of FIG. 2A, and a bottom surface 20b located on the opposite side of the detection surface 20a faces the card holder 13 or the card holder 14.

  As shown in FIG. 2A, the CdTe element 2 has a chamfered portion 23 and a chamfered portion 26 formed on a surface 20e facing the substrate 11 and on a side perpendicular to the detection surface 20a. . The chamfered portion 23 is formed at a position where the surface 20e and the side surface 20c intersect. Further, the chamfered portion 24 is formed at a position where the surface 20e and the side surface 20d intersect.

  As shown in FIG. 2B, the chamfered portion 23 includes a first chamfered portion 21 formed in the CdTe element 2 and a second chamfered portion 22 formed in the electrode 4a. Further, as shown in FIG. 2B, the chamfered portion 26 includes a first chamfered portion 24 formed on the CdTe element 2 and a second chamfered portion 25 formed on the electrode 4h. Become. The chamfered portion 23 and the chamfered portion 26 are formed by a chamfering process to be described later. This chamfering is, for example, a process of obliquely cutting the surface 20e of the CdTe element 2. Note that the chamfering of the chamfered portion 23 and the chamfered portion 26 is not limited to the oblique cutting, and may be, for example, a process of cutting out the side of the CdTe element 2 to form a curved surface.

  FIG. 3A is a schematic diagram regarding the mounting of the CdTe element according to the comparative example, and FIG. 3B is a schematic diagram regarding the mounting of the CdTe element according to the first embodiment.

  When a CdTe element is mounted, the CdTe element and the substrate may come into contact with each other, and a minute crack may occur in the CdTe element. Further, when the CdTe element is fixed to the substrate with a conductive adhesive described later, the substrate may be warped due to residual stress due to adhesion, and the warpage may cause the CdTe element and the substrate to contact each other.

  As shown in FIG. 3A, the corner portion 70 of the CdTe element 7 according to the comparative example is not chamfered. When the CdTe element 7 is mounted on the substrate 11, as shown in FIG. 3A, if the substrate 11 and the CdTe element 7 are shifted from parallel, the corner portion 70 of the CdTe element 7 contacts the substrate 11. As a result, a minute crack enters the corner portion 70, and the characteristics of the CdTe element 7 deteriorate. Further, for example, even when the substrate 11 is slightly bent, the corner portion 70 of the CdTe element 7 may come into contact with the substrate 11.

  On the other hand, when the CdTe element 2 according to the first embodiment is mounted on the substrate 11, as shown in FIG. 3B, the substrate 11 and the CdTe element 2 are shifted from parallel as in the comparative example. Even so, contact with the substrate 11 can be avoided because the chamfered portion 23 is formed in the CdTe element 2. For example, even when the substrate 11 is slightly bent, contact with the substrate 11 can be avoided because the chamfered portion 23 is formed in the CdTe element 2.

  As shown in FIG. 2B, the CdTe element 2 has an electrode pattern 30 on a surface 20f facing the flexible substrate 12. The electrode pattern 30 is electrically connected to a wiring pattern formed on the flexible substrate 12.

  FIG. 4A is a top view of the radiation detector according to the first embodiment, and FIG. 4B is an enlarged view of the vicinity of the end of the radiation detector. FIG. 4A illustrates the CdTe element 2 mounted on one side surface of the substrate 11.

As an example, the interval w ₁ between adjacent CdTe elements 2 shown in FIG. 4A is 0.1 mm. In addition, the thickness t _{1 of the} substrate 11 is 0.2 mm as an example.

As shown in FIGS. 4A and 4B, the CdTe element 2 is fixed to the element connection portion 113 of the substrate 11 with the conductive adhesive 5. The conductive adhesive 5 is, for example, a silver paste. As an example, the thickness t ₂ of the element connection portion 113 is 30 μm. The thickness _{t 3} of the conductive adhesive 5 is, for example, 10 to 20 [mu] m. Therefore, the interval _{W 2} between the CdTe element 2 and the substrate 11 is, for example, is 40 to 50 .mu.m. The electrode pattern 30 and the electrode 4a~ electrode 4h, like the thickness _{t 3} of the element connection portion 113, as an example, a 30 [mu] m.

In the present embodiment, for example, CdTe is used as a compound semiconductor constituting the semiconductor element, but the compound semiconductor is not limited to this. For example, a compound semiconductor such as a CdZnTe (CZT) element or an HgI ₂ element that detects radiation such as γ-rays. An element can also be used.

(CdTe element cutting process)
FIGS. 5A to 5D are schematic views showing a CdTe element cutting-out process according to the first embodiment. Hereinafter, a process of cutting out the CdTe element 2 from the CdTe crystal 200 will be mainly described. In this process, a chamfered portion is formed in the CdTe element. It is assumed that the CdTe crystal 200 has a plate shape and is so large that a plurality of CdTe elements 2 are cut out. Further, in the CdTe crystal 200, the side parallel to the longitudinal direction of the CdTe element 2 is the longitudinal direction of the CdTe crystal 200. Further, in the CdTe crystal 200, the side parallel to the short direction of the CdTe element 2 is the short direction of the CdTe crystal 200.

  First, a CdTe crystal 200 is prepared. In this CdTe crystal 200, the electrode precursor film 4 is formed on one surface, and the electrode precursor film 3 is formed on the surface opposite to the one surface. The electrode precursor film 4 becomes the electrodes 4a to 4h by forming the groove portions 28a to 28g. The electrode precursor film 3 is formed with an electrode pattern, for example. Furthermore, the electrode precursor film 3 becomes an electrode pattern 30 by cutting the CdTe element 2 from the CdTe crystal 200.

  Next, as shown in FIG. 5 (a), the tip part 80 of the blade 8a is brought into contact with the surface on which the electrode precursor film 4 is formed, and moves so as to cross the lateral direction of the CdTe crystal 200. The electrode precursor film 4 and the CdTe crystal 200 are shaved to a predetermined depth (chamfering step). This chamfering process is performed a plurality of times depending on the number of CdTe elements 2 to be cut out. By this chamfering step, a plurality of grooves 201 are formed in the short direction of the CdTe crystal 200 as shown in FIG. By this chamfering step, a groove 201 that is obliquely cut in the electrode precursor film 4 and the CdTe crystal 200 is formed. In addition, the predetermined depth in the chamfering process is, for example, 500 to 600 μm.

  Here, the blade 8a has a disk shape, and a tip 80 is formed along the circumference of the disk. An angle θ between the side surface of the tip 80 and a plane parallel to the surface of the CdTe crystal 200 is, for example, 45 ° <θ <70 °. That is, by using the blade 8a having the above-described angle, the angle between the surface of the electrode precursor film 4 and the side surface of the groove 201 becomes an obtuse angle, and even if it contacts the substrate 11, chipping hardly occurs. The blade 8a is configured such that the object can be cut by bringing the tip 80 into contact with the object while rotating, with the center of the disc as the center of rotation. The tip portion 80 of the blade 8a in the present embodiment has a triangular cross section, but the present invention is not limited to this, and the cross section may have a round shape, a trapezoidal shape, or the like. good.

  Next, as shown in FIG. 5 (c), the blade 8b, which is thinner than the blade 8a, is brought into contact with the center of the groove 201, and the tip 81 of the blade 8b is the surface on which the groove 201 of the CdTe crystal 200 is formed. The electrode precursor film 4 and the CdTe crystal 200 are shaved until the opposite surface is reached, and the CdTe crystal 200 is cut. By this processing, as shown in FIG. 5D, the CdTe crystal 200 is divided into two. Also, by this processing, the first chamfered portion 21 is formed in one of the cut CdTe crystals 200, the second chamfered portion 22 is formed in the electrode precursor film 4, and the first chamfered portion is formed. A chamfered portion 23 composed of 21 and the second chamfered portion 22 is formed. At the same time, the first chamfered portion 24 is formed in the other cut CdTe crystal 200, the second chamfered portion 25 is formed in the electrode precursor film 4, and the first chamfered portion 24 and the second chamfered portion 24 A chamfered portion 26 made of the chamfered portion 25 is formed.

  Next, the longitudinal side of the CdTe element 2 that does not form the chamfered portion is cut, and each cross section is polished to obtain the desired CdTe element 2.

(Effects of the first embodiment)
According to the radiation detector 1 according to the first embodiment, since the chamfered portion 23 and the chamfered portion 26 are formed in the CdTe element 2, the CdTe element 2 is mounted on the substrate as compared with the case where it is not formed. 11 can prevent the occurrence of cracks due to the contact of the corners of the CdTe element 2 when mounted on 11, and suppress the deterioration of characteristics. Therefore, the characteristics of the radiation detector 1 are improved and the yield is improved.

  Moreover, since the radiation detector 1 processes the CdTe crystal 200 in two steps for the side forming the chamfered portion, the cutting of the electrode precursor film 4 is performed as compared with the case of processing at one time. Clogging of the blade accompanying the above is suppressed, and an increase in chipping and a decrease in dicing speed due to a decrease in the cutting performance of the blade can be prevented. Therefore, the cutting efficiency of the CdTe element 2 is improved, and the manufacturing cost of the radiation detector 1 is reduced.

[Second Embodiment]
The second embodiment is different from the first embodiment in that chamfering is performed on all sides of the CdTe element.

  FIG. 6 is a perspective view of a CdTe element according to the second embodiment. In the second embodiment, parts having the same configuration and function as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  As shown in FIG. 6, the CdTe element 2 according to the present embodiment is formed on one side in the longitudinal direction of the CdTe element 2, and the first chamfered portion 21 a formed on the CdTe element 2 and the electrode 4 a A second chamfered portion 22a formed uniformly on the electrode 4h, and a chamfered portion 23a. Further, the CdTe element 2 is formed on the other side in the longitudinal direction of the CdTe element 2, and the first chamfered portion 24a formed on the CdTe element 2 and the electrodes 4a to 4h are formed uniformly. Two chamfered portions 25a, and a chamfered portion 26a.

  Further, on the surface 20e of the CdTe element 2, groove portions 29a to 29g are formed with a certain width and interval. The grooves 29a to 29g have a V-shaped cross section. This shape is formed by a blade having a triangular cross-sectional shape at the tip. Hereinafter, a process of cutting out the CdTe element 2 from the CdTe crystal 200 will be described.

(Cut process of CdTe element 2)
For cutting out the CdTe element 2 from the CdTe crystal 200, first, the CdTe crystal 200 is processed according to the size of the CdTe element 2 to be cut out by the blade 8a used for chamfering. In other words, in the first embodiment, chamfering is performed only on the short side of the CdTe element 2, but in this embodiment, chamfering is also performed on the long side. Is done. At this time, the groove portion 29a to the groove portion 29g are formed by the blade 8a.

  Next, a groove formed along the periphery of the CdTe element 2 to be cut out is processed using the blade 8b, and a plurality of CdTe elements 2 are cut out from the CdTe crystal 200. Subsequently, each cross section is polished to obtain a desired CdTe element 2.

(Effect of the second embodiment)
According to the radiation detector 1 according to the second embodiment, since all of the sides of the CdTe element 2 facing the substrate 11 are chamfered, contact between the CdTe element 2 and the substrate 11 during mounting is performed. Can be prevented. In the present embodiment, the chamfered portion 23, the chamfered portion 23a, the chamfered portion 26, the chamfered portion 26a, and the groove portions 29a to 29g are formed using the blade 8a used for the chamfering process. Compared with the case where the blade is replaced when forming the film, the number of processes is reduced, and the manufacturing cost can be suppressed.

  As mentioned above, although embodiment of this invention and its modification were demonstrated, embodiment and modification which were described above do not limit the invention which concerns on a claim. In addition, it should be noted that not all combinations of features described in the embodiments and the modifications are necessarily essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1 ... Radiation detector 2 ... CdTe element 2 ... Semiconductor element 3 ... Electrode precursor film | membrane 4 ... Electrode precursor film | membrane 4a ... Electrode 4h ... Electrode 5 ... Conductive adhesive 6 ... Radiation 7 ... CdTe element 8a ... Blade 8b ... Blade DESCRIPTION OF SYMBOLS 11 ... Board | substrate 11a-11d ... Board terminal 12 ... Flexible board 13 ... Card holder 14 ... Card holder 15 ... Elastic member mounting part 16 ... Elastic member 17 ... Projection part 18 ... Groove hole 19 ... Projection part 20a ... Detection surface 20b ... Bottom surface 20c ... Side surface 20d ... Side surface 20e ... Surface 20f ... Surface 21 ... First chamfered portion 21a ... First chamfered portion 22 ... Second chamfered portion 22a ... Second chamfered portion 23 ... Chamfered portion 23a ... Chamfer 24 ... 1st chamfer 24a ... 1st chamfer 25 ... 2nd chamfer 25a ... 2nd chamfer 26 ... Chamfer 26a ... chamfers 27a-27h ... Pixels 28a to 28g ... Grooves 28a to 29g ... Grooves 30 ... electrode pattern 70 ... corner portion 80 ... tip 81 ... tip 110 ... electronic component mounting portion 111 ... pattern 112 ... card edge portion 113 ... device connection unit 200 ... CdTe crystal 201 ... groove

Claims (4)

A substrate,
A semiconductor element having a chamfered portion that detects radiation and is chamfered on at least one side of the surface facing the substrate;
A radiation detector comprising: The semiconductor element has a detection surface for detecting the radiation;
The radiation detector according to claim 1, wherein the chamfered portion is formed on a side of the surface facing the substrate that is perpendicular to the detection surface. The semiconductor element has an electrode on a surface facing the substrate;
3. The radiation detector according to claim 1, wherein the chamfered portion includes a first chamfered portion formed in the semiconductor element and a second chamfered portion formed in the electrode.   The radiation detector according to any one of claims 1 to 3, wherein the chamfered portion is a slope.

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