JP2002090464A - Production method of radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can produce a detector with a highly efficient X-ray conversion at a less cost by improving the productivity of a radiation detector using an X-ray conversion layer for converting X rays directly into a charge signal. SOLUTION: An X-ray conversion layer comprising CdZnTe formed into an electrode is bonded on a metal sheet allowing dicing and then, a CdZnTe chip 1a on the metal sheet chip 4a cut out in a square pole per channel is discriminated by inspecting the performance thereof. A flexible board having a flexible cable 8 on a board 7 is set at a recess of a comb-shaped jig 13 and the meal sheet chip 4a with the CdZnTe chip 1a is bonded on the board 7 so as to let a comb part 11 guide the part of the metal sheet chip 4a. After the bonding, the comb-shaped jig 13 is taken off and the metal sheet chip 4a is electrically connected to a terminal 9 by a wire bonding 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector used in a single-slice, dual-slice, multi-slice, cone-beam X-ray CT apparatus, and more particularly to a scattered radiation preventing collimator and an X-ray direct charge signal. The present invention relates to a method for manufacturing an array-type radiation detector using an X-ray conversion layer that converts light into an X-ray.

[0002]

2. Description of the Related Art In an X-ray CT apparatus, an X-ray radiated from an X-ray tube is narrowed down to a fan-shaped X-ray beam by a collimator of a radiation port, and an X-ray tube and an object facing the X-ray tube are focused on a subject. An arc-shaped collimator and detector arranged in a rotating manner are rotated, the detector captures X-ray information transmitted through the subject, and the signal is processed by a computer to obtain an X-ray tomographic image of the subject. is there.

[0003] X-rays emitted from an X-ray tube are classified into two types: X-rays that pass straight through an object and are scattered by the object. The X-rays take in only the former information and remove scattered rays entering obliquely. In order to prevent the crosstalk, a collimator is provided in front of the detector. In this collimator, an X-ray shielding wall is formed of a material that is difficult to transmit X-rays for each channel in front of detectors arranged one-dimensionally.

The detector comprises an X-ray tube comprising an X-ray detecting element comprising a scintillator element for converting X-rays into light and a photodiode for detecting the light converted by the scintillating element and outputting it as an electric signal. And about 500 to 1000 channels arranged in an arc with the center as the center. Due to the mechanical arrangement in manufacturing, a combination of a scintillator and a photodiode, which are optically bonded and combined, and 8 to 30 units are arranged on a substrate is considered as one module. It is continuously arranged in a substantially arc shape on the upper side and combined with a collimator to constitute a radiation detector for CT.

FIG. 6 shows a conventional collimator 20, and FIG. 7 shows a sectional structure of a single slice radiation detector in a slice direction. The collimator 20 includes an X-ray shielding plate 21 in the channel direction, an arc-shaped main support plate 22 provided before and after in the slice direction, a support plate 23, and a detector mounting plate 25 supporting the support plate 23. . An X-ray shielding plate 21 in the channel direction is inserted and fixed between the two main support plates 22 and the support plate 23 in the slice direction in the direction of incidence of the X-ray beam from the X-ray tube. Then, both ends of the collimator 20 are reinforced by support rods 24. The collimator 20 includes a scintillator 28 and a P
Substrate 2 on which DA (photodiode array) 27 is mounted
6 and the mounting screw 32 are combined so that the upper and lower positions are aligned. At this time, the positional accuracy of the collimator 20 and the detector unit is set accurately, and the detection sensitivity of each detector is made uniform and maximum. And the bottom plate 29, the side plate 3
0. The protection plate 33 is attached to protect the detector unit, and is integrally attached to the rotating body of the CT apparatus via the main support plate 22.

The X-ray shielding plate 2 in the channel direction
The first fixing and bonding operation has a hollow space having a shape along the entire outer shape of the collimator 20, and a jig frame having a number of vertical grooves along which the X-ray shielding plate 21 can be inserted. The X-ray shielding plate 21 cut in advance in the channel direction is inserted in the vertical direction along the groove, and
After the main support plate 22 and the support plate 23 are integrally bonded to both end surfaces of the wire shielding plate 21, the main support plate 22 and the support plate 23 are pulled out from the frame body to one of upper and lower sides. Thereafter, in the manufactured collimator 20, the detector mounting plate 25 is fixed to the support plate 23 by screws. The direction in which the X-ray shielding plate 21 is fixed in the channel direction is processed so that the directions of the grooves are respectively converged in the focal direction of the X-ray tube so that the directions of the grooves converge in the direction of the focal point of the X-ray tube. .

[0007]

The conventional method of manufacturing a radiation detector is performed as described above. However, in a radiation detector using a semiconductor single crystal or polycrystal which has been recently proposed, an X-ray A semiconductor material that generates charges (electrons-holes) by being irradiated with such radiation is used, has high dark resistance, has a wide dynamic range with respect to X-ray irradiation, and has a high S / S ratio.
For example, CdZnTe polycrystal has been proposed as a material having good N and good photoconductive properties. It has been found that the sensitivity is about 3 to 10 times higher than the conventional one and is useful.

Further, since each channel can be separated by an electrode, there is an advantage that a separator or the like is not required as in the case of forming a scintillator array, and the channels can be easily separated. However, a semiconductor single crystal or a polycrystal has a problem that a crystal interface is present on a wafer, it is difficult to form a semiconductor single crystal or a polycrystal having a uniform large area, and the productivity is very low.

Therefore, if a module having a large area (including a volume) is separated into electrodes and manufactured as a module, it becomes expensive. In general, semiconductor crystals are very brittle, and there is a problem in that when the cut pieces are arranged and collected, if the crystals come into contact with each other, they are chipped or broken, resulting in damage in terms of performance. Therefore, it is necessary to assemble small-sized ones with high precision so that the crystals do not come into contact with each other.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and improves the productivity of a radiation detector using an X-ray conversion layer that directly converts X-rays into a charge signal, thereby reducing the cost. It is an object of the present invention to provide a method for manufacturing a detector with high X-ray conversion efficiency.

[0011]

In order to achieve the above object, a method of manufacturing a radiation detector according to the present invention comprises: an X-ray conversion layer having electrodes on upper and lower surfaces for converting X-rays directly into charge signals; A dicing-processable metal thin plate or a dicing-processable insulating thin plate on which a metal film is deposited is bonded and electrically connected to each other, cut into one-channel square prism shape together with the thin plate, and then combed. X using a tool
Positioning and bonding is performed on the substrate so that the portion other than the line conversion layer becomes a contact surface, and after removing the comb-shaped jig, the pad portion of the flexible cable on the substrate and the electrode portion of the X-ray conversion layer are separated. It is made by electrical connection.

Another method of manufacturing a radiation detector according to the present invention is directed to an X-ray conversion layer which has one electrode on an upper surface and two electrodes corresponding to two slices on a lower surface and directly converts X-rays into a charge signal. And a dicing insulative thin plate having electrodes divided into two by vapor deposition of a metal film corresponding thereto and bonding and electrically connecting each of the electrodes. Cut out into a shape, and then perform positioning bonding on the substrate using a comb-shaped jig so that the portion other than the X-ray conversion layer becomes a contact surface, remove the comb-shaped jig, and The flexible cable is manufactured by electrically connecting the pad portion of the flexible cable and the electrode portion of the X-ray conversion layer.

Further, another method of manufacturing a radiation detector according to the present invention is directed to an X-ray conversion apparatus having one electrode on an upper surface and a plurality of electrodes corresponding to a multi-slice on a lower surface for directly converting an X-ray into a charge signal. A layer, a dicing insulative thin plate having a wiring pattern and a plurality of divided electrodes formed by vapor deposition of a metal film corresponding thereto are bonded and electrically connected to each electrode, and a one-channel multi-slice is provided together with the thin plate. And then, using a comb-shaped jig, positioning and bonding are performed on the substrate so that the portion other than the X-ray conversion layer becomes a contact surface, and after removing the comb-shaped jig ,
A pad portion of the analog switching element on the substrate and X
It is manufactured by electrically connecting the electrode portion of the line conversion layer.

The method of manufacturing a radiation detector according to the present invention is performed as described above. The X-ray conversion layer for directly converting X-rays into charge signals has one electrode on the upper surface and the number of slices on the lower surface. Electrodes are formed, and correspondingly, electrodes and wiring patterns are formed on a dicing insulating thin plate by metal film deposition corresponding to the number of slices, and both are adhered to establish electrical continuity for each electrode. , And cut it into a quadrangular prism shape for one channel multi-slice together with the insulating thin plate. Then, using a comb-shaped jig, perform positioning and bonding on the substrate so that the portion other than the X-ray conversion layer becomes the hit surface. After the comb-shaped jig is removed, the pads of the analog switching elements on the substrate and the electrodes of the X-ray conversion layer are electrically connected to each other, so that the productivity is improved and the X-ray conversion is performed at low cost. Efficient radiation detection It is possible to obtain.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a radiation detector according to the present invention will be described with reference to FIGS. FIG. 1 is a view showing a manufacturing process up to the inspection of an X-ray detecting element cut into a quadrangular prism shape for one channel multi-slice of the radiation detector of the present invention. FIG. 2 is a diagram showing a manufacturing process of assembling the X-ray detection element cut into a quadratic prism shape for one channel multi-slice and the substrate 7 using a comb-shaped jig 13. FIG. 3 shows a one-slice radiation detector assembled by the method of manufacturing the radiation detector. The method of manufacturing the radiation detector includes the steps of (a) preparing a wafer,
(B) electrode deposition on the front and back surfaces of the wafer, (c) dicing cut of the wafer into a plate, (d) preparation of a thin metal plate, (e)
Bonding of CdZnTe plate, (f) dicing cut, (g) unit inspection, (h) preparation of flexible substrate,
(I) Comb jig preparation and (j) assembling steps.

(A) In the wafer preparation step, a CdZnTe polycrystalline wafer 1 is used as an X-ray conversion layer of a semiconductor. C
The dZnTe polycrystal was prepared by melting a polycrystal rod in a crucible together with active impurities for control and gradually pulling it up with a seed crystal rod, or by vertically drawing the polycrystal rod in a vacuum or in an inert gas. A fixed high frequency coil is moved to gradually melt and cool the polycrystal to form a single crystal, and the distribution of the active impurities for control contained in the core wire of the polycrystal rod is made uniform. The CdZnTe polycrystal thus manufactured is mechanically cut with a wire saw or the like to prepare a disc-shaped CdZnTe polycrystal wafer 1.

(B) In the step of performing electrode deposition on the front and back surfaces of the wafer, a metal such as Pt or Au is vacuum-deposited on the front and back surfaces of the CdZnTe polycrystalline wafer 1 to form the electrodes 2. (C) In the step of dicing and cutting the wafer into a plate, the CdZnTe polycrystalline wafer 1 is dicing and cut into a plate to produce a CdZnTe plate 3.
The dimension in this case is processed so that at least one side is the same as the dimension in the slice direction that is finally finished.

(D) In the metal thin plate preparing step, a dicing capable metal thin plate 4 or a dicing capable insulating thin plate on which a metal film is deposited is prepared. For example, A1100
Use a thin sheet of pure aluminum like. (E) In the bonding step of the CdZnTe plate, CdZn
The Te plate 3 and the thin metal plate 4 are bonded with a conductive adhesive or the like.

(F) In the dicing cut step, the bonded CdZnTe plate 3 is diced and cut to the size of one channel together with the metal thin plate 4, and the chip with the CdZnTe chip 1a mounted on the metal thin plate chip 4a. To finish. (G) In the single inspection step, each chip is inspected for dark current and X-ray characteristics one by one, and non-defective products and defective products are separated. A negative potential is applied to the upper electrode using a DC power supply 6, and X-rays are irradiated to amplify a signal current from a CdZnTe chip 1a, which is an X-ray conversion layer, with an amplifier 5 for inspection.

(H) In the flexible board preparation step, a flexible board in which a flexible cable 8 is connected to a pad portion having terminals 9 on one side of a board 7 on which a plurality of detector chips for one channel are to be mounted. Prepare (I) In the comb-shaped jig preparation step, a space is provided in the center portion where a chip having the CdZnTe chip 1a bonded thereto is placed on the metal thin plate chip 4a, and the comb portion 11 is provided inside the front and rear frames. A comb-shaped jig 13 having a jig frame 10 in which a concave portion 12 into which a substrate 7 can be inserted is prepared. The comb-shaped jig 13 is manufactured by inserting and fixing a metal plate into a groove formed by wire electric discharge machining.

(J) In the assembling step, the substrate 7 with the flexible cable 8 is
Is set, and the comb portion 11 of the comb-shaped jig 13 is CdZnT
The thin metal chip 4 with the CdZnTe chip 1a is guided so as to guide the thin metal chip 4a portion of the e chip 1a.
a is adhered onto the substrate 7. After bonding, the comb-shaped jig 13
Then, the terminal 9 of the pad portion of the flexible cable 8 and the CdZnTe
The metal sheet chip 4a of each channel of the chip 1a is electrically connected.

FIG. 3 shows a detector unit which has been assembled by the method of manufacturing the radiation detector. The detector section shown in the figure is
One detector module, which is arranged in a substantially circular arc shape continuously on the circumference, and a plurality of collimators 20 are arranged and combined to constitute a radiation detector for CT.

FIG. 4 shows a method for manufacturing a two-slice radiation detector. In this case, the electrode portion 15 on the lower surface of the plate-shaped CdZnTe 16 is formed by dividing it into two so that two slices can be performed. And this electrode part 15
Is formed by vapor deposition of Pt or Au. On the other hand, a dicable insulating thin plate 17 having an electrode portion 15a divided into two by a metal deposition film, for example, an insulating thin plate 17 made of a machinable ceramic, is connected to a conductive adhesive or an ACF (Anisotropic Conductive).
e Film: an anisotropic conductive film, which is made of an electrically connecting material in which conductive particles such as carbon black, nickel fine particles, and ball solder are dispersed or oriented in a resin) and adhered to the electrode portion 15 for electrical connection. Do. A dicing cut is performed on the resulting product in the same manner as in the case of a single slice. The subsequent steps (f) and thereafter are the same as in the case of the single slice.

FIG. 5 shows a method for manufacturing a multi-slice radiation detector. In this case, a plate-like CdZnTe16
The electrode portion 18 on the lower surface is divided into a plurality of pieces so that multi-slice can be performed. On the other hand, a dicing-resistant insulating thin plate 17 having a plurality of electrode portions 18a formed by metal film deposition and wiring patterns drawn therefrom and connection pad portions 19 formed thereon, for example, an insulating material made of machinable ceramic The thin plate 17 is adhered to the electrode portion 18 with an ACF, a solder bump, or the like to perform electrical connection. Using the pattern on the insulating thin plate 17 as a guide, the completed product is subjected to dicing cut as in the case of single slice. Subsequent step (f)
The following is the same as the case of the single slice, except that the flexible substrate has a switching element mounted thereon and uses a flexible substrate capable of switching channels.

[0025]

The method of manufacturing a radiation detector according to the present invention is performed as described above, and an X-ray conversion layer having electrodes formed thereon is bonded to an insulating thin plate which can be diced and has electrodes deposited on the upper surface. After that, it is cut into a quadrangular prism shape for one channel, separated, and assembled on a substrate using a dedicated comb-shaped jig, so that a radiation detector with high yield, low cost, and high X-ray conversion efficiency is obtained. be able to. Further, since the detector unit is assembled for each module, the module can be easily replaced. Further, since the detector is assembled by the jig, a highly accurate detector can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a method for manufacturing a radiation detector of the present invention.

FIG. 2 is a view showing a step subsequent to FIG. 1 in the method for manufacturing a radiation detector of the present invention.

FIG. 3 is a diagram showing one embodiment of a radiation detector according to the manufacturing method of the present invention.

FIG. 4 is a view showing another embodiment of the method for manufacturing a radiation detector of the present invention.

FIG. 5 is a view showing another embodiment of the method for manufacturing a radiation detector of the present invention.

FIG. 6 is a diagram showing a collimator of a conventional radiation detector.

FIG. 7 is a diagram showing a conventional radiation detector.

[Description of Symbols] 1 ... CdZnTe polycrystalline wafer 1a ... CdZnTe chip 2 ... Electrode 3 ... CdZnTe plate 4 ... Metal thin plate 4a ... Metal thin plate chip 5 ... Amplifier 6 ... DC power supply 7 ... Substrate 8 ... Flexible cable 9 ... Terminal 10 ... Jig frame 11 Comb part 12 Concave part 13 Comb jig 14 Wire bonding 15 Electrode part 15a Electrode part 16 Plate-shaped CdZnTe 17 Insulating thin plate 18 Electrode part 18a Electrode part 19 Pad part

Claims (3)

[Claims] An X-ray conversion layer having electrodes on upper and lower surfaces for directly converting X-rays into a charge signal, and a dicing-processable metal thin plate or a dicing-processable insulating thin plate on which a metal film is deposited. Adhesion and electrical continuity are taken, cut into a rectangular column shape for one channel together with the thin plate, and then, using a comb-shaped jig, a portion other than the X-ray conversion layer is brought into contact with the substrate so as to be a contact surface. After the positioning jig is removed and the comb-shaped jig is removed, the pad portion of the flexible cable on the substrate and the electrode portion of the X-ray conversion layer are electrically connected to each other to manufacture the radiation detector. Method. 2. An X-ray conversion layer having one electrode on an upper surface and two electrodes corresponding to two slices on a lower surface for directly converting X-rays into a charge signal, and correspondingly two layers by metal film deposition. A dicing insulative thin plate having divided electrodes is adhered and electrically connected to each electrode, and cut into a rectangular column of two slices per channel together with the thin plate, and then using a comb-like jig. Then, after positioning and bonding are performed on the substrate so that the portion other than the X-ray conversion layer becomes a contact surface, and the comb-like jig is removed, the pad portion of the flexible cable on the substrate and the electrode of the X-ray conversion layer are removed. A method for producing a radiation detector, wherein the radiation detector is manufactured by making an electrical connection with a part. 3. An X-ray conversion layer having one electrode on an upper surface and a plurality of electrodes corresponding to a multi-slice on a lower surface for directly converting X-rays into a charge signal, and a plurality of corresponding X-ray conversion layers formed by metal film deposition. The dicing insulative thin plate having the electrode and the wiring pattern divided and formed is adhered and electrically connected to each electrode, and cut into a rectangular column shape for one channel multi-slice together with the thin plate. Using a jig, positioning and bonding are performed on the substrate such that a portion other than the X-ray conversion layer becomes a contact surface, and the comb-like jig is removed. A method for manufacturing a radiation detector, comprising: manufacturing by electrically connecting an electrode portion of a line conversion layer.