JP2004008406A - Method for manufacturing radiation detector, radiation detector, and x-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a radiation detector by which the yield of detection elements with respect to a wafer is improved, and to provide the detector and an X-ray CT apparatus. <P>SOLUTION: A plurality of the detection elements 3 are formed in a matrix state on the wafer 23 (S1). The wafer 23 is cut into a plurality of blocks 5 having a matrix size of m×n(S2). The blocks 5 are inspected individually (S3). The blocks 5 having passed through the inspection are arrayed to constitute a module 1 having a matrix size of M×N(which satisfies at least either M>m≥1 or N>n≥1)(S4). The module is arrayed to constitute the radiation detector (S5). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a radiation detector in which a plurality of detection elements that detect radiation such as X-rays as electric signals are arranged in a matrix, a radiation detector, and an X-ray CT apparatus.
[0002]
[Prior art]
A medical X-ray CT apparatus (X-ray computed tomography apparatus) has an X-ray tube and a radiation detector. X-rays generated by the X-ray tube pass through the subject and enter the detector. The detector includes a plurality of detection elements that generate electric charges according to the intensity of incident radiation such as X-rays. The detection element includes an indirect conversion type in which X-rays are converted into light by a phosphor (scintillator), and the light is converted into an electric signal by a photoelectric conversion element (photodiode); There is a direct conversion type using the generation of electron-hole pairs in the cell and transfer to the electrodes, that is, the photoconduction phenomenon. In the future, the direct conversion type that can realize a small, light, and flat plate type is considered to be widespread. ing.
[0003]
As a detector for X-ray CT, a single slice type detector has been widely used. The single slice type detector includes a plurality of detection elements arranged in a line. Multi-slice detectors in which the single-slice detectors are arranged in a plurality of rows have been widely used. Further, in recent years, practical use of a detector called a two-dimensional array type in which the density of detection elements is increased has been awaited.
[0004]
FIG. 13 schematically shows the structure of a two-dimensional array type detector. In the two-dimensional array type detector, a module design is adopted to increase the density of detection elements. One module 103 includes a photodiode 101 formed on one substrate with a matrix size of M × N. The modules 103 are arranged in a plurality of arcs in the channel direction. Thus, a detector having a large matrix size of L × N can be configured.
[0005]
FIG. 14 shows the creation of the module 103. The photodiodes 103 are formed on the silicon wafer 105 at a constant density. For example, two modules 101 are cut out from one wafer 105 at a matrix size of M × N.
[0006]
Here, as the number of columns of the detector increases, the matrix size of the module 101 also increases accordingly. Therefore, the number of modules 101 that can be cut out from one wafer 105 decreases, and accordingly, waste of the wafer increases. Further, the operation inspection of the detection element is performed on the module 101 cut out from the wafer 105. If one or several non-conforming detection elements are found, the module 101 itself is defective. As the matrix size of the modules 101 increases, the ratio (yield) of defective modules 101 deteriorates.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method of manufacturing a radiation detector, a radiation detector, and an X-ray CT apparatus capable of improving the yield of detection elements with respect to a wafer.
[0008]
[Means for Solving the Problems]
In the method for manufacturing a radiation detector according to the first aspect of the present invention, a plurality of detection elements are formed in a matrix on a wafer, and the wafer is cut into a plurality of blocks having a matrix size of m × n. A block having a matrix size of M × N (at least one of M> m ≧ 1 and N> n ≧ 1) is configured by arranging blocks that have been individually inspected and passed the inspection. The radiation detector is arranged.
[0009]
A method of manufacturing a radiation detector according to a second aspect of the present invention includes forming a plurality of detection elements on a wafer in a matrix, individually inspecting the detection elements formed on the wafer, and detecting elements not passing the inspection. Is cut off from the wafer, a piece of the detecting element that has passed the inspection is mounted on the wafer, the wafer is cut into a plurality of blocks, and the blocks are arranged to constitute a radiation detector.
[0010]
A method for manufacturing a radiation detector according to a third aspect of the present invention includes forming a plurality of detection elements on a wafer in a matrix, individually inspecting the detection elements formed on the wafer, and detecting elements not passing the inspection. , The wafer is cut into a plurality of blocks having a matrix size of m × n, and the blocks are arranged to satisfy at least one of M × N (M> m ≧ 1, N> n ≧ 1) A module having a matrix size of (1) is formed, and the modules are arranged to form a radiation detector.
[0011]
A method of manufacturing a radiation detector according to a fourth aspect of the present invention includes forming a plurality of detection elements on a wafer in a matrix, individually inspecting the detection elements formed on the wafer, and detecting elements not passing the inspection. Is avoided, the wafer is cut into a plurality of blocks, and the blocks are arranged to form a radiation detector.
[0012]
A radiation detector according to a fifth aspect of the present invention is a radiation detector in which a plurality of modules each having a detection element arranged in an M × N matrix size are arranged, wherein the modules are m × n (M> m ≧ m). 1, at least one of N> n ≧ 1) is arranged in a matrix.
[0013]
The X-ray CT according to the sixth aspect of the present invention can rotate an X-ray tube that generates X-rays, a radiation detector that detects X-rays transmitted through a subject, and the X-ray tube and the radiation detector. A gantry to support, based on data of a predetermined angle range derived from the output of the radiation detector, a reconstruction unit for reconstructing image data, and a display unit for displaying the reconstructed image data And the radiation detector includes a plurality of modules having detection elements arranged in a matrix size of M × N, and the module includes m × n (M> m ≧ 1, N> n ≧ (Satisfies at least one of the two).
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the X-ray CT apparatus, a rotation / rotation (ROTATE / ROTATE) type in which an X-ray tube and a radiation detector rotate as one body around the subject, and a large number of detection elements arranged in a ring, There are various types such as a fixed / rotated (STATIONARY / ROTATE) type in which only the X-ray tube rotates around the subject, and the present invention is applicable to any type. Here, the rotation / rotation type which occupies the mainstream at present is described. The mechanism of converting incident X-rays into electric charges is as follows: an indirect conversion type in which X-rays are converted into light by a phosphor such as a scintillator, and the light is converted into electric charges by a photoelectric conversion element such as a photodiode; There is a direct conversion type utilizing the generation of electron-hole pairs in the inside and transfer to the electrodes, that is, the photoconductive phenomenon. As the X-ray detecting element, any of those methods may be adopted, but here, the former indirect conversion type will be described.
[0015]
FIG. 1 is a system diagram of the X-ray CT apparatus of the present embodiment. The X-ray tube 131 is rotatably supported around the subject 132 together with the radiation detector 127. The X-ray tube 131 generates a so-called cone beam X-ray that spreads in two directions, a channel direction C and a slice direction A (a direction parallel to the rotation axis (a direction perpendicular to the paper surface)). The X-ray transmitted through the subject 132 is detected by the radiation detector 127. The data acquisition circuit (DAS) 134 amplifies the signal detected by the radiation detector 127 and converts the signal into a digital signal. The preprocessing device 135 corrects data output from the DAS 134. The storage device 136 stores the data corrected by the preprocessing device 135.
[0016]
The host controller 138 includes a high-voltage generator 139 for supplying power to the X-ray tube 131, a gantry driving unit 140 for rotating a gantry for rotating the X-ray tube 131 and the like, a reconstructing device 137 for reconstructing data, a reconstructing device. A display device 141 for displaying the reconstructed image by the 137 is connected.
[0017]
FIG. 2 is a plan view showing the structure of the radiation detector 127, focusing on the photodiode element array. In FIG. 2, the horizontal direction (horizontal direction) of the drawing represents the channel direction, and the vertical direction (vertical direction) of the drawing represents a slice direction substantially parallel to the body axis and the rotation axis of the subject. The radiation detector 127 has a plurality of modules 1 mounted on a module mount base (not shown). The plurality of modules 1 are arranged in the channel direction, or in two directions of the channel direction and the slice direction. Each module 1 has a plurality of photodiode elements 3 arranged in an M × N matrix size. In the entire detector, the photodiode elements 3 are arranged in a matrix size of L × N, where L is the number of M × modules.
[0018]
FIG. 3 shows an arrangement of the photodiode elements 3 constituting each module 1. The module 1 has a block mine (not shown) and a plurality of blocks 5 mounted on a base. The plurality of blocks 5 are arranged in two directions, a channel direction and a slice direction, or one of them. Each block 5 has a plurality of photodiode elements 3 formed in a matrix of m × n on a lump semiconductor substrate. M> m ≧ 1 and N> n ≧ 1 are satisfied, that is, the matrix size (m × n) of the photodiode elements 3 forming the block 5 is the matrix size (M × n) of the photodiode elements 3 forming the module 1. It is designed to be smaller than N).
[0019]
Actually, as shown in FIG. 4, a scintillator 4 is mounted on the front side of the module 1, and a switch board 7 for signal reading and scanning is mounted on a rear surface thereof via a multilayer wiring board 6. In order to connect the module 1 to the multilayer wiring board 6 on its back side, the signal electrodes of the module 1 are connected to a plurality of Al wirings 15 formed on the surface of the semiconductor substrate 24, as shown in FIG. The Al wiring 15 is connected to bumps 19 on the rear surface of the substrate via a plurality of through wirings 17 penetrating from the front surface to the rear surface of the substrate 24. The bumps 19 are connected to a plurality of corresponding bumps formed on the surface of the multilayer wiring board 6 by soldering.
[0020]
The switch board 7 mounted on the back of the multilayer wiring board 6 is mounted on a rigid printed wiring board 9. A DAS chip 11 and a connector 13 are attached to the printed wiring board 9 together with the switch board 7. The plurality of printed wiring boards 9 on which the modules 1 and the like are mounted are mounted on a module mount base 21, as shown in FIG.
[0021]
FIG. 7 shows a procedure of a first manufacturing method of the detector having such a configuration. First, usually, the photodiode elements 3 are formed at a constant density almost all over a circular silicon wafer (S1). Next, as shown in FIG. 8, the wafer 23 is vertically and horizontally cut at a pitch corresponding to the above-mentioned m × n matrix size. Thereby, a plurality of blocks 5 having a matrix size of m × n are cut out from one wafer 23. Since the block 5 has a smaller matrix size than the module 1, the amount of wafer waste left after cutting out the plurality of blocks 5 from one wafer 23 is reduced by one or a small number of modules 1 from one wafer 23. The amount of wafer waste remaining after cutting can be reduced. Thereby, the number of photodiode elements 3 cut out from one wafer 23 can be increased.
[0022]
Next, a performance test of each photodiode element 3 is performed for each of the cut-out blocks 5 (S3). Here, the block 5 having the photodiode element 3 in which even one of the predetermined performances could not be achieved is discarded as a defective product. By performing the inspection in units of blocks 3 smaller than the module 1, it is possible to reduce the number of photodiode elements 3 discarded together with defective photodiode elements 3 in spite of good quality.
[0023]
In this way, by cutting out the wafer 23 in small block units and performing inspection and disposal in units of blocks, the photodiode elements that can be used for products (detectors) from one wafer 23 through inspections are obtained. 3 can be increased, that is, the yield can be improved.
[0024]
A plurality of blocks 5 that have passed the inspection are tiled on a block mount base to create a module 1 (S4). Further, a plurality of modules 1 are tiled on a module mount base to create a detector (S5).
[0025]
As shown in FIG. 9, a 1 × 1 matrix size block unit, that is, the photodiode elements 3 may be individually cut out from the wafer 23, and the photodiode elements 3 may be individually inspected. In this case, the non-defective element is not discarded together with the defective element, and the highest yield can be achieved. However, in consideration of the accuracy and workability of the cutting process and the module integration process, it is considered that it is preferable to cut out the photodiode elements 3 from the wafer 23 in a certain size such as 10 × 10 rather than cutting out the photodiode elements 3 individually in units of one element. Can be
[0026]
FIG. 10 shows a procedure of the second manufacturing method of the detector. The photodiode elements 3 are formed at a constant density over substantially the entire area of the silicon wafer 23 (S11). In the second manufacturing method, a performance test of each photodiode element 3 is performed in a state of the wafer 23 before cutting (S12). This can be realized by drawing out the signal electrode of the photodiode element 3 from the rear surface via the through wiring 17 as shown in FIG.
[0027]
As a result of the inspection, a small pixel region (surface layer portion or penetration) including the defective photodiode element 3 and its wiring, etc., which could not achieve the predetermined performance, is cut off from the wafer 23 by a laser (S13). A small pixel component including a non-defective photodiode element 3 having achieved a predetermined performance and its wiring and the like is embedded and adhered to the cut and vacant portion (S14). As a result, all the photodiode elements 3 on the wafer 23 are formed of non-defective products.
[0028]
This wafer 23 is vertically and horizontally cut at a pitch corresponding to the mxn matrix size. As a result, a plurality of non-defective blocks 5 having a matrix size of m × n are cut out from one wafer 23 (S15). A plurality of cut-out blocks 5 are tiled on a block mount base to create a module 1 (S16), and a plurality of modules 1 are tiled on a module mount base to create a detector (S17).
[0029]
According to the second manufacturing method, although the steps of removing defective elements and embedding non-defective elements are required, non-defective elements are not discarded together with defective elements, and the highest yield can be achieved.
[0030]
FIG. 11 shows a procedure of the third manufacturing method of the detector. The photodiode elements 3 are formed at a constant density over substantially the entire area of the silicon wafer 23 (S21). As in the second manufacturing method, a performance test of each photodiode element 3 is performed in the state of the wafer 23 before cutting (S22).
[0031]
Next, as shown in FIG. 12, the area of the non-defective photodiode element 3 excluding the area 27 of the defective photodiode element 3 where the predetermined performance could not be achieved is expressed in units of m × n matrix unit or Is designed as a minimum unit (S23). The wafer 23 is cut according to the cutting pattern 25. As a result, a plurality of non-defective blocks 5 having a matrix size of m × n or a piece of an integral multiple thereof are cut out from one wafer 23. A plurality of cut-out blocks 5 are tiled on a block mount base to create a module 1 (S25), and a plurality of modules 1 are tiled on a module mount base to create a detector (S26).
[0032]
According to the third manufacturing method, the steps of removing defective elements and embedding non-defective elements are not required, and the number of non-defective elements discarded together with defective elements can be reduced, thereby improving the yield.
[0033]
(Modification)
The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention at the stage of implementation. Furthermore, the above-described embodiment includes various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed components. For example, some components may be deleted from all the components shown in the embodiment.
[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the yield of the detection element with respect to a wafer can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an X-ray CT apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of the radiation detector of FIG.
FIG. 3 is a schematic plan view of the module of FIG. 2;
FIG. 4 is a side view of the module of FIG. 2;
FIG. 5 is a sectional view of the module of FIG. 2;
FIG. 6 is a diagram showing an arrangement of the modules in FIG. 4;
FIG. 7 is a flowchart showing the procedure of the first detector manufacturing method according to the embodiment;
FIG. 8 is a supplementary diagram of the cutting step S2 in FIG. 7;
FIG. 9 is a view showing another example of the cutting step S2 in FIG. 7;
FIG. 10 is a flowchart showing a procedure of a second detector manufacturing method according to the embodiment.
FIG. 11 is a flowchart showing a procedure of a third detector manufacturing method according to the embodiment.
FIG. 12 is a view showing an example of the cutting pattern of FIG. 11;
FIG. 13 is a schematic plan view of a conventional radiation detector.
FIG. 14 is a view showing a conventional wafer cutting pattern.
[Explanation of symbols]
1 ... Module,
3. Photodiode element,
5 ... block,
6 ... multilayer wiring board,
7 ... Switch board,
9 ... relay wiring board,
11 ... DAS unit,
13. Connector unit,
131 ... X-ray tube,
127 ... radiation detector,
132 ... subject,
134 data collection circuit
135 ... data processing device,
136 ... Storage device,
137 ... reconstruction device,
138 ... Host controller,
139 high voltage generator,
140 ... gantry drive unit,
141 display device,
143 input device.

Claims (6)

Forming a plurality of detection elements in a matrix on the wafer,
Cutting the wafer into a plurality of blocks having a matrix size of m × n,
Inspecting said blocks individually,
A block having a matrix size of M × N (where at least one of M> m ≧ 1 and N> n ≧ 1 is satisfied) is configured by arranging the blocks that have passed the inspection,
A method for manufacturing a radiation detector, comprising arranging the modules to form a radiation detector. Forming a plurality of detection elements in a matrix on the wafer,
Individually inspecting the detection elements formed on the wafer,
Severing from the wafer the sensing elements that the test has not passed,
A piece of the detection element that has passed the inspection is mounted on the wafer,
Cutting the wafer into a plurality of blocks;
A method for manufacturing a radiation detector, comprising arranging the blocks to constitute a radiation detector. Forming a plurality of detection elements in a matrix on the wafer,
Individually inspecting the detection elements formed on the wafer,
Cutting the wafer into a plurality of blocks having a matrix size of mxn, avoiding the inspection elements that the inspection does not pass,
By arranging the blocks, a module having a matrix size of M × N (at least one of M> m ≧ 1, N> n ≧ 1) is configured,
A method for manufacturing a radiation detector, comprising arranging the modules to form a radiation detector. Forming a plurality of detection elements in a matrix on the wafer,
Individually inspecting the detection elements formed on the wafer,
Cutting the wafer into a plurality of blocks, avoiding detection elements that the inspection does not pass,
A method for manufacturing a radiation detector, comprising arranging the blocks to constitute a radiation detector. In a radiation detector in which a plurality of modules having detection elements arranged in an M × N matrix size are arranged,
The module is configured by arranging a plurality of blocks arranged in a matrix size of m × n (satisfies at least one of M> m ≧ 1, N> n ≧ 1). . An X-ray tube for generating X-rays,
A radiation detector for detecting X-rays transmitted through the subject;
A gantry that rotatably supports the X-ray tube and the radiation detector,
Based on data for a predetermined angle range derived from the output of the radiation detector, a reconstruction unit that reconstructs image data,
Comprising a display unit for displaying the reconstructed image data,
The radiation detector includes a plurality of modules having detection elements arranged in a matrix size of M × N, and the module includes at least one of m × n (M> m ≧ 1, N> n ≧ 1). An X-ray CT apparatus comprising a plurality of blocks arranged with a matrix size of

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