JP3029873B2 - Radiation detecting element and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation detecting element, and more particularly to a radiation detecting element having a large-area light receiving portion used for medical X-ray photography or the like.

BACKGROUND ART In medical and industrial X-ray photography, an X-ray photosensitive film has been conventionally used. However, a radiation imaging system using a radiation detecting element has become widespread from the viewpoint of convenience and preservation of a photographed result. . In such a radiation imaging system, two-dimensional image data due to radiation is acquired as an electric signal using a radiation detecting element having a plurality of pixels, and this signal is processed by a processing device and displayed on a monitor. . A typical radiation detecting element has a structure in which a scintillator is arranged on a photodetector arranged one-dimensionally or two-dimensionally, and incident radiation is converted into light by the scintillator and detected.

CsI, a typical scintillator material, is a hygroscopic material that absorbs and dissolves water vapor (moisture) in the air.
As a result, there is a problem that the characteristics of the scintillator, particularly the resolution, are deteriorated.

As a radiation detecting element having a structure for protecting a scintillator from moisture, a technique disclosed in Japanese Patent Application Laid-Open No. 5-196742 is known. In this technique, the scintillator is protected from moisture by forming a moisture-impermeable moisture-proof barrier above the scintillator layer.

DISCLOSURE OF THE INVENTION However, in this technique, it is difficult to make the moisture barrier at the outer peripheral portion of the scintillator layer adhere to the substrate of the radiation detecting element. Since the length is long, the moisture-proof barrier is easily peeled off, and the scintillator layer is not completely sealed, so that moisture penetrates into the scintillator layer and its characteristics are apt to deteriorate.

Also, in this technology, the moisture sealing layer of the moisture barrier is
After applying the silicone potting material etc. to the scintillator layer in a liquid state, or applying this silicone potting material etc. to the inside of the window material installed on the light receiving surface side of the radiation detection element, before drying the moisture seal layer A manufacturing method for fixing the moisture sealing layer by disposing the window material on the scintillator layer is disclosed. In this manufacturing method, it is difficult to uniformly form the moisture seal layer on the scintillator layer having an irregular surface shape, and there is a possibility that the adhesiveness is reduced. This point is particularly likely to occur in a radiation detection element having a large area.

In view of the above problems, an object of the present invention is to provide a radiation detecting element having a protective film which is uniform and easy to manufacture for moisture prevention of a scintillator, and a method of manufacturing the same.

In order to solve this problem, the radiation detecting element according to the present invention includes: (1) a method in which a plurality of light receiving elements are one-dimensionally or
A light receiving element array having a plurality of bonding pads electrically connected to the light receiving elements in each row or each column of the light receiving section, the light receiving elements being arranged in a three-dimensional manner,
(2) a scintillator layer for converting radiation deposited on the light receiving element into visible light; and (3) a radiation-permeable moisture-resistant protective film covering the scintillator layer and exposing the bonding pad portion of the light receiving element array. And (4) a coating resin that coats the moisture-resistant protective film along an edge that is a boundary with the exposed portion of the light-receiving element array, and makes the edge of the moisture-resistant protective film adhere to the light-receiving element array. It is characterized by the following.

Thereby, the incident radiation is converted into visible light by the scintillator layer. By detecting this visible light image with light receiving elements arranged one-dimensionally or two-dimensionally, an electric signal corresponding to the incident radiation image is obtained. Although the scintillator layer has the property of deteriorating due to moisture absorption, according to the present invention, the scintillator layer is covered with a moisture-resistant protective film, and the edge of the moisture-resistant protective film is coated with a coating resin. Sealed from the outside air and protected from water vapor in the air.
Further, a bonding pad portion for connection to an external circuit is exposed.

On the other hand, the method for manufacturing a radiation detecting element of the present invention comprises the following steps:
A plurality of light receiving elements are arranged one-dimensionally or two-dimensionally on a substrate to form a light receiving section, and a plurality of bonding pads electrically connected to the light receiving elements in each row or each column of the light receiving section are formed outside the light receiving section. Depositing a scintillator layer for converting radiation into visible light on the light-receiving elements of the light-receiving element array disposed in (2), and (2) forming a radiation-permeable moisture-resistant protective film so as to surround the entire light-receiving element array; (3) cutting and removing at least a portion of the moisture-resistant protective film outside the scintillator layer and covering the bonding pad;
And (4) coating the moisture-resistant protective film with a resin along an edge portion that is a boundary with the exposed portion of the light-receiving element array, and exposing the moisture-resistant protective film to an edge including the bonding pad. In contact with the light receiving element array.

By forming the first organic film so as to surround the entire light receiving element array, the degree of adhesion between the scintillator layer and the moisture-resistant protective film is improved, and a uniform film is formed. After forming a uniform moisture-resistant protective film in this manner, the bonding pad is reliably exposed by removing the moisture-resistant protective film on the bonding pad portion. Further, by coating the moisture-resistant protective film with a resin along the edge portion which is a boundary with the exposed portion, the edge of the moisture-resistant protective film adheres to the surface of the light receiving element array thereunder, and the scintillator layer under the moisture-resistant protective film is sealed. Is stopped.

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: These are given by way of example only and should not be considered as limiting the invention.

Further areas of applicability of the present invention will become apparent from the following detailed invention. However, while the detailed description and specific examples illustrate preferred embodiments of the present invention, they are provided by way of example only, and various modifications and improvements in the spirit and scope of the invention may be made. Will be apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG.

3 to 10 are diagrams sequentially showing the manufacturing process of the embodiment according to FIG.

FIG. 11 is a top view of another embodiment of the present invention, FIG.
Is a sectional view taken along the line BB.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in order to facilitate understanding, the same components are denoted by the same reference numerals as much as possible in each of the drawings, and redundant description will be omitted. Further, dimensions and shapes in the drawings are not necessarily the same as actual ones, and some parts are exaggerated for easy understanding.

FIG. 1 is a top view of one embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view taken along line AA of an outer peripheral portion thereof.

First, the configuration of the present embodiment will be described with reference to FIGS. Light receiving elements 2 that perform photoelectric conversion are two-dimensionally arranged on an insulating, for example, glass substrate 1 to form a light receiving section. The light receiving element 2 includes a photodiode (PD) and a thin film transistor (TF) made of amorphous silicon.
T). Each of the light receiving elements 2 in each row or each column is electrically connected by a signal line 3 for signal reading. A plurality of bonding pads 4 for extracting a signal to an external circuit (not shown) are arranged along the outer periphery of the substrate 1, for example, along two adjacent sides.
It is electrically connected to a corresponding plurality of light receiving elements 2 via a signal line 3. An insulating passivation film 5 is formed on the light receiving element 2 and the signal line 3. This passivation film 5 is preferably made of silicon nitride or silicon oxide. On the other hand, the bonding pad 4 is exposed for connection with an external circuit. Hereinafter, this substrate and the circuit portion on the substrate will be referred to as the light receiving element array 6.
Call.

On the light receiving section of the light receiving element array 6, a scintillator 7 having a columnar structure for converting incident radiation into visible light is formed. Various materials can be used for the scintillator 7, but Tl-doped CsI or the like having good luminous efficiency is preferable. On the scintillator 7, a first organic film 8, which transmits X-rays and blocks water vapor, an inorganic film 9, and a second organic film
10 are laminated to form a protective film 11.

For the first organic film 8 and the second organic film 10, polyparaxylylene resin (trade name: Parylene, manufactured by ThreeBond), particularly polyparachloroxylylene (trade name: Parylene C, manufactured by the company) may be used. preferable. The parylene coating film has very low water vapor and gas permeability, high water repellency, high chemical resistance, excellent electrical insulation even in a thin film, and is transparent to radiation and visible light. , 10 have excellent characteristics. For more information on Parylene coating, see ThreeBond
It is described in Technical News (issued on September 23, 1992), and its features are described here.

Parylene can be coated by a chemical vapor deposition (CVD) method that deposits on a support in a vacuum, similar to vacuum deposition of metals. This involves thermally decomposing P-xylene as a raw material and rapidly cooling the product in an organic solvent such as toluene or benzene to obtain diparaxylylene, which is called a dimer. It comprises a step of generating xylylene gas, and a step of polymerizing and forming a polyparaxylylene film having a molecular weight of about 500,000 by adsorbing and polymerizing the generated gas on a material.

The pressure for parylene deposition is the pressure for metal vacuum deposition.
0.1-0.2 Torr which is higher than 0.001 Torr. Then, at the time of vapor deposition, after the monomolecular film covers the entire adherend, parylene is further vapor-deposited thereon. Therefore, 0.
A thin film with a thickness of 2 μm can be formed to a uniform thickness without pinholes, and it is also possible to coat sharp corners, edges, and narrow gaps on the order of microns, which were not possible with liquid material coating. is there. Further, since heat treatment or the like is not required at the time of coating and coating can be performed at a temperature close to room temperature, no mechanical stress or thermal distortion due to curing occurs, and the coating has excellent stability. In addition, coatings on most solid materials are possible.

On the other hand, various materials such as transparent, opaque, and reflective materials can be used for the inorganic film 9 as long as it is X-ray permeable to visible light, such as oxide films of Si, Ti, and Cr, and gold. Metal thin films such as silver, aluminum and the like can be used. In particular, it is preferable to use a film that reflects visible light, because it has the effect of preventing the fluorescence generated by the scintillator 7 from leaking outside and increasing the sensitivity. Here, an example using Al which is easy to mold will be described. Al itself is easily corroded in the air, but the inorganic film 9
Is protected from corrosion because it is sandwiched between the first organic film 8 and the second organic film 10.

The outer circumference of the protective film 11 extends to the inside of the bonding pad 4 between the respective outer circumferences of the light receiving section and the light receiving element array 6, and the bonding pad 4 is exposed for connection to an external circuit. Here, the protective film 11 is formed by the above-described parylene coating, but is formed by the CVD method, and thus is formed so as to cover the entire surface of the light receiving element array 6. Therefore, in order to expose the bonding pad 4, it is necessary to cut the protection film 11 formed of the parylene coating inside the bonding pad 4 and remove the protection film 11 outside. in this case,
The protective film 11 is easily peeled from the outer peripheral portion that is the cut portion. Therefore, the coating resin 12 is coated so as to cover the outer peripheral portion of the protective film 11 and the portion of the passivation film 5 of the light receiving element array 6 on the outer peripheral portion.

The coating resin 12 includes a protective film 11 and a passivation film 5.
Good adhesion to resin, such as acrylic adhesive WORLD ROCK No.801-SET2 manufactured by Kyoritsu Chemical Industry Co., Ltd.
(70,000 cP type) is preferably used. This resin adhesive is hardened in about 20 seconds by ultraviolet irradiation of 100 mW / cm ^2, the cured film has flexibility and sufficient strength, moisture resistance, water resistance, resistance to electric tactile properties, is excellent in migration resistance, various It has good adhesion to materials, especially glass, plastics, and the like, and has favorable characteristics as the coating resin 12.

Next, a manufacturing process of this embodiment will be described with reference to FIGS. On the light-receiving surface of the light-receiving element array 6 as shown in FIG. 3, as shown in FIG. 4, a columnar crystal of CsI doped with T1 is grown to a thickness of 600 μm by vapor deposition to form a scintillator 7 layer. I do.

CsI forming this scintillator 7 layer has high hygroscopicity, and if left unexposed, will absorb and dissolve water vapor in the air. Therefore, in order to prevent this, as shown in FIG. 5, the first organic film 8 is formed by coating parylene on the entire surface of the substrate to a thickness of 10 μm by the CVD method. Although there is a gap in the columnar crystal of CsI, parylene enters this narrow gap, so that the first organic film 8 is in close contact with the scintillator 7 layer. Furthermore, the parylene coating provides a precise thin film coating with a uniform thickness on the surface of the seven-layer scintillator having irregularities. Also, parylene CV
As described above, D formation can be performed at a lower vacuum than at the time of metal deposition and at room temperature, so that processing is easy.

Further, as shown in FIG. 6, an inorganic film 9 is formed by laminating an Al film having a thickness of 0.15 μm on the surface of the first organic film 8 on the incident surface side by a vapor deposition method. Then, parylene was again applied to the surface of the entire substrate by 10 μm as shown in FIG.
The second organic film 10 is formed by coating with a thickness. This second organic film 10 prevents deterioration of the inorganic film 9 due to corrosion.

As shown in FIG. 8, the protective film 11 thus formed is cut using an excimer laser or the like along the outer periphery of the light receiving portion inside the bonding pad 4 between the light receiving portion and the outer peripheral portion of the light receiving element array 6, As shown in FIG. 9, the unnecessary protective film 11 on the outer side and the back side of the incident surface is removed from the cut portion to expose the bonding pad 4 for connection to an external circuit.
Since the passivation film 5 and the first organic film 7 as the lowermost layer of the protective film 11 have poor adhesion, if the cut outer peripheral portion is left as it is, the protective film 11 tends to peel off from the outer peripheral portion. Therefore, as shown in FIG. 10, the covering resin covers the outer peripheral portion of the protective film 11 and the portion of the passivation film 5 therearound.
Then, the coating resin 12 is irradiated with ultraviolet rays to cure the coating resin 12, and the protective film 11 is brought into close contact with the light receiving element array 6. As a result, the scintillator 7 is hermetically sealed, so that resolution degradation due to moisture absorption can be prevented.

Subsequently, the operation of this embodiment will be described with reference to FIGS. The incident X-rays (radiation) pass through a protective film 11 composed of a first organic film 8, an inorganic film 9, and a second organic film 10.
And reaches the scintillator 7. The scintillator 7 absorbs this X-ray and emits visible light proportional to the amount of X-ray. Of the emitted visible light, the light directed in the X-ray incident direction is reflected by the inorganic film 9, and thus almost all of the visible light emitted by the scintillator 7 is the scintillator 7.
To the light receiving element 2 at the end of the line. For this reason, efficient detection becomes possible.

In each light receiving element 2, an electric signal corresponding to the amount of this visible light is generated by photoelectric conversion and accumulated for a certain period of time. The amount of visible light reaching the light receiving element 2 is
Since the light signal corresponds to the light amount of the X-ray, the electric signal accumulated in each light receiving element 2 corresponds to the light amount of the incident X-ray, and becomes an image signal corresponding to the X-ray image. This image signal stored in the light receiving element 2 is sequentially read out from the bonding pad 4 via the signal line 3, transferred to the outside, and processed by a predetermined processing circuit to display an X-ray image. Can be.

In the above description, the structure in which the inorganic film 9 is interposed between the first organic films 8 and 10 made of parylene has been described as the protective film 11, but the first organic film 8 and the second organic film 8 have the same structure. The material of the film 10 may be different. If a material resistant to corrosion is used as the inorganic film 9, the second organic film is used.
It is not necessary to provide 10 itself.

Further, here, an example in which the coating resin 12 is formed on the passivation film 5 outside the light receiving element 2 portion of the light receiving element array 6 has been described, but the case where the light receiving element 2 and the bonding pad 4 are close to each other is described. It is difficult to form the coating resin 12 at the boundary. Bonding pad 4
It is preferable to shift the position of the coating resin 12 toward the light receiving element 2 in order to surely expose the protection film 11 and coat the periphery of the protective film 11 with the coating resin 12 without fail. for that purpose,
The scintillator 7 is not formed on the entire surface of the light receiving element 2, but is formed on the light receiving element 2 in the effective screen area excluding the pixels near the bonding pad 4, and covers the entire layer of the formed scintillator 7 to form the protective film 11. To form a protective film on the pixels of the light receiving element 2 where the scintillator 7 is not formed on the upper surface.
What is necessary is just to coat 11 with the coating resin 12. In this case, the pixels in the vicinity of the bonding pad 4 are covered with the coating resin 12 or the scintillator 7 does not exist on the front surface, so that the sensitivity to the radiation is reduced. As a result, these pixels cannot be used and the effective pixels of the light receiving element 2 are not used. Although the number and the effective screen area are reduced, when the light receiving element 2 has a large screen and a large number of all pixels, the ratio of invalid pixels is small, and there is an advantage that manufacture is easy depending on the element configuration.

Next, another embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a top view of the radiation detecting element of this embodiment, and FIG. 12 is an enlarged cross-sectional view taken along the line BB. The basic configuration of this element is the same as the element of the embodiment shown in FIGS. 1 and 2, and only the differences will be described below.
explain.

In this embodiment shown in FIGS. 11 and 12, the protective film 11 is formed on the front surface on the light receiving surface side and the back surface side of the light receiving element array 6, and only the bonding array 4 is exposed. Then, along with the boundary (edge) of the protective film 11, the covering resin is formed so as to surround the exposed bonding array 4.
12 are coated. Also in this embodiment, the bonding pad 4 is surely exposed, and the protective film is formed.
Since the coating resin 12 is securely adhered to the light receiving element array 6 by the coating resin 12, the scintillator 7 layer is sealed, and deterioration due to moisture absorption can be prevented.

This is especially a CCD or MOS with a small bonding pad 4
In the case of a type image sensor, the length of an edge portion, which is a boundary portion that may cause peeling of the protective film, can be effectively reduced.

Further, in the above description, a so-called front-incident type radiation detection element that emits radiation from the scintillator side on the light-receiving element has been described. Application to an element is also possible. Such a back-illuminated radiation detecting element can be used as a high-energy radiation detecting element.

As described above, according to the present invention, in order to protect a scintillator having high hygroscopicity, a protective film made of parylene or the like is formed on the scintillator, and the edge of the protective film is coated with a resin such as acrylic. As a result, the scintillator layer is hermetically sealed. In particular, since peeling from the edge of the protective film is prevented, the moisture resistance is improved.

According to the manufacturing method of the present invention, the unnecessary portion is removed after the formation of the protective film, so that the formation of the protective film in a uniform state is easier than in the case where the protective film is formed only on the necessary portion, and the bonding pad can be reliably formed. It is exposed to. Further, the protective film penetrates into the gaps between the crystals of the deposited scintillator, so that the adhesion between the protective film and the scintillator layer is increased.

It is apparent from the above description of the present invention that the present invention can be variously modified. Such modifications cannot be deemed to depart from the spirit and scope of the invention,
Modifications obvious to all persons skilled in the art are intended to be included within the scope of the following claims.

INDUSTRIAL APPLICABILITY The radiation detection element of the present invention is applicable to a large-area radiation imaging system used in medical and industrial X-ray photography. In particular, it can be used for chest X-ray photography and the like instead of the X-ray film widely used at present.

Continuation of front page (56) References JP-A-5-60871 (JP, A) US Patent 5,227,635 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/20

Claims (8)

(57) [Claims] A plurality of light receiving elements are arranged on a substrate one-dimensionally or two-dimensionally to form a light receiving part, and a plurality of bonding elements electrically connected to the light receiving elements in each row or each column of the light receiving part. A light-receiving element array having a pad outside the light-receiving unit, a scintillator layer for converting radiation deposited on the light-receiving element into visible light, and covering the scintillator layer, and bonding the bonding pad portion of the light-receiving element array. An exposed radiation-transmissive moisture-resistant protective film, and coating the moisture-resistant protective film along an edge of the moisture-resistant protective film, which is a boundary portion between the exposed portion of the light-receiving element array, to form an edge of the moisture-resistant protective film. A radiation detecting element comprising: a coating resin that is in close contact with the light receiving element array. 2. The method according to claim 1, wherein the bonding pad is located at an outer peripheral portion of the substrate, and the moisture-resistant protective film is formed so as to cover between an outer edge of the light receiving portion and an outer edge of the light receiving element array. The radiation detecting element according to claim 1, wherein a coating resin coats an outer peripheral portion of the moisture-resistant protective film. 3. The device according to claim 1, wherein the moisture-resistant protective layer is composed of two or more multilayer films including at least an organic film.
Or the radiation detection element according to any one of 2. 4. The radiation detecting element according to claim 3, wherein said moisture-resistant protective film includes at least one inorganic film. 5. A plurality of light receiving elements are arranged one-dimensionally or two-dimensionally on a substrate to form a light receiving part, and a plurality of bonding elements electrically connected to the light receiving elements in each row or each column of the light receiving part. Depositing a scintillator layer for converting radiation into visible light on the light receiving element of a light receiving element array in which a pad is arranged outside the light receiving section; and a radiation-permeable moisture-resistant protective film so as to surround the entire light receiving element array. Forming, and cutting and removing at least a portion of the moisture-resistant protective film outside the scintillator layer that covers the bonding pad, and removing the light-receiving element array portion at least in a region including the bonding pad. Exposing; coating the moisture-resistant protective film with resin along an edge portion which is a boundary with the exposed portion of the light receiving element array; Method of manufacturing a radiation detecting device having a step of adhering the edges of the moisture-resistant protective film on the light-receiving element array. 6. A plurality of bonding elements electrically arranged with a plurality of light receiving elements arranged one-dimensionally or two-dimensionally on a substrate to form a light receiving part, and electrically connected to the light receiving elements in each row or each column of the light receiving part. Depositing a scintillator layer for converting radiation into visible light on the light-receiving element of the light-receiving element array in which pads are arranged on the outer periphery of the substrate; and a radiation-permeable moisture-resistant so as to wrap the entire light-receiving element array. Forming a protective film, and cutting the moisture-resistant protective film along the outer periphery of the scintillator layer at a position between the outer periphery of the scintillator layer and the bonding pad portion. Removing the formed moisture-resistant protective film to expose the bonding pad; and coating the cut outer peripheral portion of the moisture-resistant protective film with a resin. Method of manufacturing a radiation detecting device having a step of the wet protective layer peripheral portion is adhered to the light receiving element array. 7. The step of forming the moisture-resistant protective film comprises: forming a radiation-transparent first organic film; and further laminating at least one film on the first organic film. 7. A method for manufacturing a radiation detecting element according to claim 5, wherein: a step of forming a radiation-permeable moisture-resistant protective film composed of two or more multilayer films. 8. The method according to claim 7, wherein the moisture-resistant protective film includes at least one inorganic film.