Active matrix substrate, X-ray imaging panel with the same, and method for producing the same

An active matrix substrate includes: a photoelectric conversion element 15; an electrode 14b provided with a first opening h1 and disposed on one surface of the photoelectric conversion element 15; an organic insulating film 106 provided with a second opening h2 and covering the photoelectric conversion element 15 and the electrode 14b; and a conductive film 16 for supplying a bias voltage to the electrode 14b. The first opening h1 and the second opening h2 overlap each other when viewed in plan view. The conductive film 16 is provided inside the first opening h1 and the second opening h2 so as to be in contact with the electrode 14b.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention disclosed herein relates to an active matrix substrate, an X-ray imaging panel with the same, and a method for producing the active matrix substrate.

2. Description of Related Art

Conventionally, an active matrix substrate having pixels each provided with a photoelectric conversion element connected to a switching element has been used in X-ray imaging devices. For example, JP 2011-114310 A discloses such an X-ray imaging device. The X-ray imaging device disclosed in JP 2011-114310 A includes an array substrate in which light-receiving pixel regions are arrayed. Each light-receiving pixel region is provided with a photodiode that includes a lower electrode, a photoelectric conversion layer, and an upper electrode, and a passivation film is provided so as to cover surfaces of the photodiode, upper electrode, and lower electrode. A contact hole that passes through the passivation film is formed above the upper electrode, and a bias line connected to the upper electrode through the contact hole is provided on the passivation film.

By the way, during the production process of an active matrix substrate, components contained in an upper electrode, an organic insulating film provided on the upper electrode, etc. may be deposited and accumulate on the upper electrode. When a bias line is formed on the upper electrode with a deposit being present on the upper electrode, contact failure may occur between the bias line and the upper electrode. When contact failure occurs, a bias voltage is not applied to the upper electrode, and imaging cannot be performed properly. This causes a reduction in yield of an array substrate.

SUMMARY OF THE INVENTION

An active matrix substrate developed in light of the above-described problem is an active matrix substrate including: a photoelectric conversion element; an electrode provided with a first opening, the electrode being disposed on one surface of the photoelectric conversion element; an organic insulating film provided with a second opening, the organic insulating film covering the photoelectric conversion element and the electrode; and a conductive film for supplying a bias voltage to the electrode. The first opening and the second opening overlap each other when viewed in plan view. The conductive film is provided inside the first opening and the second opening so as to be in contact with the electrode.

According to the present invention, it is possible to suppress a reduction in yield of an active matrix substrate.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail below with reference to the drawings. Components that are identical or equivalent to each other in the drawings are given the same reference numerals, and descriptions thereof are not repeated.

First Embodiment

FIG. 1is a schematic view showing an X-ray imaging device that uses an active matrix substrate according to the present embodiment. An X-ray imaging device100includes an active matrix substrate1and a control unit2. The control unit2includes a gate control section2A and a signal readout section2B. A subject S is irradiated with X-rays emitted from an X-ray source3. X-rays that have passed through the subject S are converted to fluorescence (referred to as “scintillation light” hereinafter) by a scintillator4disposed over the active matrix substrate1. The X-ray imaging device100acquires an X-ray image by capturing the scintillation light using the active matrix substrate1and the control unit2.

FIG. 2is a schematic view showing a schematic configuration of the active matrix substrate1. As shown inFIG. 2, a plurality of source lines10and a plurality of gate lines11that cross the plurality of source lines10are formed on the active matrix substrate1. Each gate line11is connected to the gate control section2A, and each source line10is connected to the signal readout section2B.

The active matrix substrate1has a plurality of pixels, which are bounded by the source lines10and the gate lines11, as light-receiving regions for receiving scintillation light converted from X-rays that have passed through the subject S. Each pixel is provided with a TFT13and a photodiode12.

The gate lines11on the active matrix substrate1are sequentially switched to a selected state by the gate control section2A, and TFTs13connected to the gate line11that is in the selected state are turned ON. In each pixel, when the TFT13is turned ON, a signal corresponding to a charge obtained through conversion of the scintillation light by the photodiode12is output to the signal readout section2B through the source line10.

FIG. 3is an enlarged plan view showing one of the pixels on the active matrix substrate1shown inFIG. 2. As shown inFIG. 3, a pixel P1is provided with a photodiode12and a TFT13.

The TFT13includes a gate electrode13aconnected to a gate line11, a semiconductor active layer13b, a source electrode13cconnected to a source line10, and a drain electrode13d. The drain electrode13dand the photodiode12are connected to each other through a contact hole CH1.

In this example, in the pixel P1, a bias line16is disposed substantially in parallel to the gate lines11and such that it overlaps the photodiode12when viewed in plan view, and the photodiode12and the bias line16are connected to each other through a contact hole CH2. The bias line16supplies a bias voltage to the photodiode12.

Next, the configuration of the pixel P1will be described specifically with reference toFIGS. 4A and 4B.FIG. 4Ais a schematic cross-sectional view of the pixel P1taken along line A-A inFIG. 3.FIG. 4Bis an enlarged view of a portion including a region where the photodiode12is provided inFIG. 4A.

As shown inFIG. 4A, the gate electrode13aand a gate insulating film102are formed on a substrate101. The substrate101is a substrate having insulating properties, such as, for example, a glass substrate.

In this example, the gate electrode13ais formed integrally with the gate line11(seeFIG. 3). In the present embodiment, the gate electrode13aand the gate line11have a laminate structure in which a lower layer made of tantalum nitride (TaN) and an upper layer made of tungsten (W) are laminated. It is preferable that, for example, the thickness of the tantalum nitride (TaN) is approximately between 30 nm to 100 nm inclusive, and the thickness of the tungsten (W) is approximately between 300 nm to 500 nm inclusive. The structures of the gate electrode13aand the gate line11are not limited to the two-layer structure, and they may be composed of a single layer or three or more layers. The material and the thickness of the gate electrode13aand the gate line11are described as illustrative examples, and they are not limited to those described above.

The gate electrode13aand the gate line11(seeFIG. 3) are covered with the gate insulating film102. In the present embodiment, the gate insulating film102has a laminate structure in which an inorganic insulating film made of silicon nitride (SiNx) as a lower layer and an inorganic insulating film made of silicon oxide (SiOx) as an upper layer are laminated. It is preferable that the thickness of the inorganic insulating film made of silicon nitride (SiNx) is approximately 325 nm and the thickness of the inorganic insulating film made of silicon oxide (SiOx) is approximately 50 nm. The structure of the gate insulating film102is not limited to the two-layer structure, and the gate insulating film102may be composed of a single layer or three or more layers. The material and the thickness of the gate insulating film102are not limited to those described above.

The semiconductor active layer13b, and the source electrode13cand the drain electrode13d, which are connected to the semiconductor active layer13b, are provided on the gate electrode13awith the gate insulating film102interposed therebetween.

The semiconductor active layer13bis formed in contact with the gate insulating film102. The semiconductor active layer13bis made of an oxide semiconductor. The oxide semiconductor, for example, an amorphous oxide semiconductor containing indium (In), gallium (Ga), and zinc (Zn) at a predetermined ratio, may be used. In this case, it is preferable that the thickness of the semiconductor active layer13bis approximately 100 nm, for example. It is to be noted that the material and the thickness of the semiconductor active layer13bare not limited to those described above.

The source electrode13cand the drain electrode13dare disposed on the gate insulating film102so as to be in contact with portions of the semiconductor active layer13b. In this example, the source electrode13cis formed integrally with the source line10(seeFIG. 3). The source electrode13cand the drain electrode13deach have a laminate structure in which three metal films made of titanium (Ti), aluminum (Al), and titanium (Ti), respectively, are laminated in this order from the lowermost layer. It is preferable that the thicknesses of these three layers are approximately 50 nm, approximately 300 nm, and approximately 50 nm in this order from the lowermost layer. The structure of each of the source electrode13cand the drain electrode13dis not limited to the three-layer structure, and they may be composed of a single layer or two or more layers. The material and the thickness of each of the source electrode13cand the drain electrode13dare not limited to those described above.

A first insulating film103is provided on the gate insulating film102so as to overlap the source electrode13cand the drain electrode13d. The first insulating film103has a contact hole CH1that passes through the first insulating film103at a position on the drain electrode13d. In this example, the first insulating film103is an inorganic insulating film containing silicon oxide (SiO2). It is preferable that the thickness of the first insulating film103is approximately 500 nm, for example. The structure of the first insulating film103is not limited to the single-layer structure, and may be a laminate structure in which an inorganic insulating film made of silicon oxide and an inorganic insulating film made of silicon nitride are laminated, for example.

On the first insulating film103, a cathode electrode (referred to as “lower electrode” hereinafter)14aof the photodiode12and second insulating films104are provided. The lower electrode14ais connected to the drain electrode13dthrough the contact hole CH1. In the present embodiment, the lower electrode14ahas a laminate structure in which three metal films made of titanium (Ti), aluminum (Al), and titanium (Ti), respectively, are laminated in this order from the lowermost layer. It is preferable that the thicknesses of these three metal films are, for example, approximately 50 nm, approximately 300 nm, and approximately 50 nm in this order from the lowermost layer. The structure of the lower electrode14ais not limited to the three-layer structure, and the lower electrode14amay be composed of a single layer or two or more layers. The material and the thickness of the lower electrode14aare not limited to those described above.

On the first insulating film103, the second insulating films104are provided such that they are spaced apart from each other on the lower electrode14a. In the present embodiment, the second insulating films104are inorganic insulating films made of silicon oxide (SiO2). The thickness of the second insulating films104is approximately 400 nm in this example. It is preferable that the thickness of the second insulating films104is approximately between 300 nm to 500 nm inclusive. It is to be noted that the material and the thickness of the second insulating films104are not limited to those described above.

A photoelectric conversion layer15is provided on the second insulating films104and the lower electrode14a. The photoelectric conversion layer15is obtained by laminating an n-type amorphous semiconductor layer151, an intrinsic amorphous semiconductor layer152, and a p-type amorphous semiconductor layer153in this order.

The n-type amorphous semiconductor layer151is made of amorphous silicon doped with an n-type impurity (e.g., phosphorus). The n-type amorphous semiconductor layer151is in contact with the lower electrode14a.

The intrinsic amorphous semiconductor layer152is made of intrinsic amorphous silicon. The intrinsic amorphous semiconductor layer152is formed in contact with the n-type amorphous semiconductor layer151.

The p-type amorphous semiconductor layer153is made of amorphous silicon doped with a p-type impurity (e.g., boron). The p-type amorphous semiconductor layer153is formed in contact with the intrinsic amorphous semiconductor layer152.

In this example, it is preferable that the thickness of the n-type amorphous semiconductor layer151is approximately between 10 nm to 100 nm inclusive and the thickness of the intrinsic amorphous semiconductor layer152is approximately between 200 nm to 2000 nm inclusive. It is preferable that the thickness of the p-type amorphous semiconductor layer153is approximately between 10 nm to 50 nm inclusive. It is to be noted that the dopants and the thicknesses of the n-type amorphous semiconductor layer151, the intrinsic amorphous semiconductor layer152, and the p-type amorphous semiconductor layer153are not limited to those described above.

On the p-type amorphous semiconductor layer153, an anode electrode (referred to as “upper electrode” hereinafter)14bof the photodiode12is provided. As shown inFIG. 4B, the upper electrode14bhas an opening h1at a position on the photoelectric conversion layer15. In the present embodiment, the upper electrode14bis, for example, a transparent conductive film made of indium tin oxide (ITO) or indium Zn oxide (IZO). It is preferable that the thickness of the upper electrode14bis approximately 100 nm, for example. It is to be noted that the material and the thickness of the upper electrode14bare not limited to those described above.

On the second insulating films104and the photodiode12, a third insulating film105is provided. As shown inFIG. 4B, an opening h2that passes through the third insulating film105is formed such that the opening h2overlaps the opening h1when viewed in plan view. The width W2of the opening h2in the X-axis direction is larger than the width W1of the opening h1.

In the present embodiment, the third insulating film105is an inorganic insulating film made of silicon nitride (SiN). It is preferable that the thickness of the third insulating film105is approximately between 300 nm to 500 nm inclusive, for example. It is to be noted that the material and the thickness of the third insulating film105are not limited to those described above.

On the third insulating film105, a fourth insulating film106is provided. As shown inFIG. 4B, an opening h3that passes through the fourth insulating film106is formed such that the opening h3overlaps the openings h1and h2when viewed in plan view. The width W3of the opening h3in the X-axis direction is smaller than the width W2of the opening h2and larger than the width W1of the opening h1. That is, in the present embodiment, the lengths W1to W3of the openings h1to h3in the X-axis direction satisfy the relationship of W1<W3<W2. A contact hole CH2is formed by the openings h1to h3. Although a cross-sectional view of a region in which the openings h1to h3are provided, taken along the extending direction of the bias line16is not shown, the widths of the openings h1to h3in the extending direction of the bias line16are substantially the same as the widths of the openings h1to h3in the X-axis direction, respectively. That is, the openings h1to h3each have an approximately square shape.

The fourth insulating film106is made of an organic transparent resin such as an acrylic resin or a siloxane resin, for example. It is preferable that the thickness of the fourth insulating film106is approximately 2.5 μm, for example. It is to be noted that the material and the thickness of the fourth insulating film106are not limited to those described above.

On the fourth insulating film106, the bias line16is provided. The bias line16is in contact with the upper electrode14band the p-type amorphous semiconductor layer153of the photoelectric conversion layer15through the contact hole CH2. The bias line16is connected to the control unit2(seeFIG. 1) and applies a bias voltage input from the control unit2to the photodiode12.

The bias line16has a laminate structure in which three metal films made of titanium (Ti), aluminum (Al), and titanium (Ti), respectively, are laminated, for example. It is preferable that the thicknesses of these metal films are approximately 50 nm, approximately 300 nm, and approximately 50 nm in this order from the lowermost layer. The structure of the bias line16is not limited thereto, and the bias line16may be composed of a single layer or two or more layers. The material of the bias line16is not limited to those described above.

A fifth insulating film107is provided so as to cover the fourth insulating film106and the bias line16. The fifth insulating film107is an inorganic insulating film made of silicon nitride (SiNx), for example. The thickness of the fifth insulating film107is approximately 300 nm in this example. It is preferable that the thickness of the fifth insulating film107is approximately between 200 nm to 500 nm inclusive. It is to be noted that the material and the thickness of the fifth insulating film107are not limited to those described above.

A sixth insulating film108is provided so as to cover the fifth insulating film107. The sixth insulating film108is made of an organic transparent resin such as an acrylic resin or a siloxane resin, for example. It is preferable that the thickness of the sixth insulating film108is approximately 3.0 μm, for example. It is to be noted that the material and the thickness of the sixth insulating film108are not limited to those described above.

Next, a method for producing the active matrix substrate1in the present embodiment will be described with reference toFIGS. 5A to 5F.FIGS. 5A to 5Fare cross-sectional views for illustrating steps of producing the active matrix substrate1. These cross-sectional views show a region in which the photodiode12of the pixel P1is formed in the respective production steps.

Although not shown in the drawings, first, the TFT13(seeFIGS. 4A and 4B, etc.), the gate insulating film102, and the first insulating film103are formed on the substrate101using a known method, and then, the photodiode12is formed on the first insulating film103.

Thereafter, as shown inFIG. 5A, the third insulating film105made of silicon nitride (SiN) is formed so as to cover the photodiode12through chemical vapor deposition (CVD), for example.

Subsequently, the third insulating film105is patterned by performing photolithography and dry etching. As a result, the opening h2of the third insulating film105is formed at a position on the upper electrode14b(seeFIG. 5B).

Next, the fourth insulating film106made of an acrylic resin is formed so as to cover the third insulating film105. Thereafter, through exposure and development of the fourth insulating film106, the opening h30that passes through the fourth insulating film106is formed inside the opening h2of the third insulating film105(seeFIG. 5C). The opening h30has a reverse tapered shape with the opening width W30in the X-axis direction on the upper electrode14bside being smaller than the opening width on the side opposite to the upper electrode14bside.

After the opening h30has been formed, a portion of the upper electrode14bbelow the opening h30of the fourth insulating film106is subjected to etching using the fourth insulating film106as a mask (seeFIG. 5D). When the upper electrode14bis made of ITO, the upper electrode14bis subjected to wet etching using oxalic acid as an etchant. As a result, the portion of the upper electrode14boverlapping the opening h30of the fourth insulating film106is removed by etching, whereby the opening h1that passes through the upper electrode14bis formed. Since the upper electrode14bis isotropically etched using the fourth insulating film106as a mask, the width W1of the opening h1of the upper electrode14bin the X-axis direction is larger than the width W30of the opening h30of the fourth insulating film106. As a result, end portions of the fourth insulating film106in the opening h30protrude farther than end portions of the upper electrode14bin the opening h1.

Subsequently, the fourth insulating film106is subjected to a plasma ashing process (seeFIG. 5E). As a result, the opening h30of the fourth insulating film106is expanded to form the opening h3. The width W3of the opening h3in the X-axis direction on the upper electrode14bside is larger than the width W30prior to the ashing process. As a result, the widths W1, W2, and W3of the openings h1to h3in the X-axis direction satisfy the relationship of W1<W3<W2. Since only oxygen is used as plasma in the plasma ashing process, the upper electrode14band the p-type amorphous semiconductor layer153of the photodiode12are not etched.

Then, the metal films made of titanium (Ti), aluminum (Al), and titanium (Ti), respectively, for forming the bias line16are formed sequentially so as to cover the fourth insulating film106through sputtering, for example. Thereafter, these three metal films are patterned by performing photolithography and dry etching (seeFIG. 5F). As a result, the bias line16is formed on the fourth insulating film106so as to cover the opening h3and the opening h1, whereby the bias line16is connected to the upper electrode14band the p-type amorphous semiconductor layer153.

After the bias line16has been formed, the fifth insulating film107(seeFIG. 4Aetc.) made of silicon nitride (SiNx) is formed so as to cover the bias line16through, e.g., CVD (this step is not shown). Then, the sixth insulating film108(seeFIG. 4Aetc.) made of, e.g., an acrylic resin is formed so as to cover the fifth insulating film107(this step is not shown). In the above-described manner, the active matrix substrate1on which the pixel P1shown inFIG. 4Ais formed is produced.

As described above, in the present embodiment, the opening h1passing through the upper electrode14bis formed, and the bias line16is connected to the p-type amorphous semiconductor layer153and the upper electrode14bthrough the opening h1. With this configuration, contact failure between the bias line16and the upper electrode14bis less likely to occur. The reason for this will be described specifically below.

Through analysis by the inventors of the present invention, it has been revealed that contact failure between the bias line16and the upper electrode14bmay be caused owing to the presence of a deposit containing a component such as Sb (antimony), In (indium), or Si (silicon) between the bias line16and the upper electrode14b. Such a deposit tends to be formed in the vicinity of the opening provided in the fourth insulating film106made of an acrylic resin in order to connect the bias line16to the upper electrode14b. Specifically, in the configuration of the above-described embodiment, after the step of exposing and developing the fourth insulating film106to form the opening h30, deposits are formed on the portion of the upper electrode14boverlapping the opening h30when In (indium) contained in the upper electrode14band Sb (antimony) contained in the fourth insulating film106react with each other or cause electric corrosion.

In the above-described embodiment, after the opening h3of the fourth insulating film106has been formed, the opening h1is formed in the portion of the upper electrode14boverlapping the opening h3when viewed in plan view. If the opening h1is not provided, the deposits formed on the upper electrode14bcause contact failure between the bias line16to be formed thereafter and the upper electrode14b. In contrast, in the present embodiment, even if deposits are formed after the opening h3of the fourth insulating film106has been formed, the deposits are removed as a result of forming the opening h1. Accordingly, contact failure between the bias line16and the upper electrode14bis less likely to occur.

Operations of the X-ray imaging device100shown inFIG. 1will now be described. First, X-rays are emitted from an X-ray source3. At this time, the control unit2applies a predetermined voltage (bias voltage) to the bias line16(seeFIG. 3etc.). The X-rays emitted from the X-ray source3pass through the subject S to be incident on the scintillator4. The X-rays incident on the scintillator4are converted to fluorescence (scintillation light), and the scintillation light is then incident on the active matrix substrate1. When the scintillation light is incident on the photodiodes12provided in the respective pixels on the active matrix substrate1, the photodiodes12convert the scintillation light to charges corresponding to the amounts of the scintillation light. Signals corresponding to the charges obtained through the conversion by the photodiodes12are read out by the signal readout section2B (seeFIG. 2etc.) through the source lines10when the TFTs13(seeFIG. 3etc.) are in an ON state in response to a gate voltage (positive voltage) output from the gate control section2A through the gate lines11. Then, the control section2generates an X-ray image corresponding to the read-out signals.

Second Embodiment

In the above-described first embodiment, the bias line16is disposed on the photoelectric conversion layer15. Accordingly, it is preferable that the bias line16has a narrower width from the viewpoint of securing the light receiving area in the pixel P1. In the first embodiment, after the opening h1of the upper electrode14bhas been formed, the opening h30of the fourth insulating film106is expanded through an ashing process. However, the narrower the width of the bias line16, the more difficult it becomes to control the position and the size of the opening h3according to the width of the bias line16through the ashing process. As a result, it becomes difficult to reliably establish contact between the bias line16and the upper electrode14b. In particular, when the contact hole CH2for bringing the bias line16into contact with the upper electrode14bhas a stack structure composed of the plurality of openings h1to h3as in the first embodiment, the openings h1to h3have to be formed properly such that the contact between the bias line16and the upper electrode14bis established reliably. The present embodiment describes a configuration with which the contact between the bias line16and the upper electrode14bcan be established more reliably.

FIG. 6Ais a plan view schematically showing an opening h2of a third insulating film105, openings h30and h3of a fourth insulating film106before and after an ashing process, and a portion of a bias line16in the present embodiment.FIG. 6Bis a schematic cross-sectional view taken along line B-B inFIG. 6A, andFIG. 6Cis a schematic cross-sectional view taken along line C-C inFIG. 6A.FIGS. 6B and 6Cboth show the state after the fourth insulating film106has been subjected to an ashing process. For the sake of convenience of illustration, a fifth insulating film107and a sixth insulating film108are not shown in these drawings.

As shown inFIG. 6A, the openings h2, h30, and h3indicated with dashed lines have rectangular shapes with their long sides extending substantially parallel to the extending direction of the bias line16when viewed in plan view. When the opening h2and the opening h30are formed in such rectangular shapes, the opening h3is formed inside the opening h2more easily at least in the extending direction of the bias line16as compared with the case where they have square shapes. In this case, as shown inFIGS. 6B and 6C, in a contact hole CH2after the ashing process, both end portions of the third insulating film105are covered with the fourth insulating film106, and the bias line16and the upper electrode14bare in contact with each other.

AlthoughFIG. 6Aillustrates an example where the opening h3formed after the ashing process is entirely inside the opening h2, the opening h3need only be formed such that at least one long side thereof is inside the opening h2as shown inFIG. 7A. In other words, the opening h3may be formed such that one of the long sides thereof is located outside the opening h2.

The schematic cross-sectional view taken along line B-B inFIG. 7Ais as shown inFIG. 7B. InFIG. 7B, the fifth insulating film107and the sixth insulating film108are not shown for the sake of convenience of illustration. In this case, as shown inFIG. 7B, in the contact hole CH2, one end portion (on the negative side along the X-axis direction) of the third insulating film105is covered with the fourth insulating film106, whereas the other end portion (on the positive side along the X-axis direction) is not covered with the fourth insulating film106. However, even with such a configuration, the bias line16and the upper electrode14bare in contact with each other in the contact hole CH2, and accordingly, contact failure between the bias line16and the upper electrode14bis less likely to occur.

FIG. 7Aillustrates an example where one of the long sides of the opening h3is located outside the opening h2. However, for example, as shown inFIG. 7C, the two long sides of the opening h3may be located inside the opening h2and one of the short sides of the opening h3may be located outside the opening h2.

The schematic cross-sectional view taken along line C-C inFIG. 7Cis as shown inFIG. 7D. InFIG. 7D, the fifth insulating film107and the sixth insulating film108are not shown for the sake of convenience of illustration. In this case, as shown inFIG. 7D, in the contact hole CH2, one end portion (on the negative side along the Y-axis direction) of the third insulating film105is covered with the fourth insulating film106, whereas the other end portion (on the positive side along the Y-axis direction) is not covered with the fourth insulating film106. However, even with such a configuration, contact failure between the contact between the bias line16and the upper electrode14bis prevented from occurring.

In the example described above, as shown inFIGS. 7B and 7D, in the contact hole CH2, the end portions of the upper electrode14bprotrude farther than the end portions of the third insulating film105and the fourth insulating film106. In this case, the bias line16is formed easily so as to extend over the entire interior of the contact hole CH2, whereby disconnection of the bias line16inside the contact hole CH2is prevented.

However, at the time of forming the opening h30of the fourth insulating film106prior to the ashing process (seeFIG. 5C), the position of the opening h30may be displaced in the X-axis direction. In this case, as shown inFIG. 8A, one end portion (on the negative side along the X-axis direction) of the third insulating film105in the opening h2protrudes farther than that of the fourth insulating film106. When the upper electrode14bis subjected to wet etching in this state using the fourth insulating film106as a mask, although an opening h1of the upper electrode14bis formed as shown inFIG. 8B, one end portion (on the negative side along the X-axis direction) of the third insulating film105in the opening h30protrudes farther than one end portion (on the negative side along the X-axis direction) of the upper electrode14bin the opening h1.

Thereafter, by subjecting the fourth insulating film106to a plasma ashing process, the opening h30of the fourth insulating film106is expanded to form the opening h3as shown inFIG. 8C. Then, by performing the same step as that shown inFIG. 5Fin the above-described first embodiment, the bias line16is formed in the contact hole CH2as shown inFIG. 8D. In this case, the bias line16is not formed in a portion encircled with the dashed line inFIG. 8D, i.e., a region covered with a portion of the third insulating film105protruding farther than the upper electrode14bin the contact hole CH2. Accordingly, the contact hole CH2includes a portion where the bias line16is not in contact with the upper electrode14b. However, in the contact hole CH2, the other end portion (on the positive side along the X-axis direction) of the upper electrode14bis in contact with the bias line16without being covered with the other end portion (on the positive side along the X-axis direction) of the third insulating film105. Accordingly, in this case, although the area of a portion where the bias line16and the upper electrode14bare in contact with each other is smaller than those inFIGS. 7B and 7D, contact failure between the bias line16and the upper electrode14bis less likely to occur.

When the openings h2, h30, and h3have rectangular shapes with their longitudinal directions coincide with the extending direction of the bias line16, even if the positions of the openings h30and h3are displaced toward the negative side along the X-axis direction relative to the opening h2, contact failure between the bias line16and the upper electrode14bis less likely to occur in the extending direction of the bias line16. Specifically, even when the positional relationship of the openings h1, h2, h30, and h3is as shown inFIG. 8E, contact failure is less likely to occur. As shown inFIG. 8E, the long sides of the openings h30and h2on the negative side along the X-axis direction are located outside the opening h2, whereas the long sides of the openings h30and h3on the positive side along the X-axis direction are located inside the opening h2. With this configuration, in the extending direction of the bias line16, end portions of the upper electrode14bin the opening h1are not covered with the third insulating film105and the fourth insulating film106, and accordingly, contact failure between the bias line16and the upper electrode14bis less likely to occur.

Third Embodiment

Although the first and second embodiments described above are directed to the configurations in which the bias line16is in direct contact with the upper electrode14b, the bias line16need not be in direct contact with the upper electrode14bas long as the bias line16and the upper electrode14bare electrically connected to each other. In the following, another configuration for connecting the upper electrode14band the bias line16will be described.

FIG. 9Ais a plan view showing a schematic configuration of a pixel P1in the present embodiment.FIG. 9Bis a schematic cross-sectional view taken along line D-D inFIG. 9Aand showing the structure of a portion of the pixel P1. InFIGS. 9A and 9B, the same components as those in the first embodiment are given the same reference numerals as used in the first embodiment. In the following, differences from the configuration of the first embodiment will be described.

As shown inFIGS. 9A and 9B, a transparent conductive film17is provided extending over the interior of a contact hole CH2and on a fourth insulating film106so as to be in contact with an upper electrode14band a p-type amorphous semiconductor layer153. The transparent conductive film17is made of ITO or IZO, for example.

Although not shown inFIG. 9B, a fifth insulating film107is provided so as to cover the surface of the transparent conductive film17and the surface of a bias line16(seeFIG. 4A), and a sixth insulating film108is formed so as to cover the fifth insulating film107(seeFIG. 4A).

The bias line16is provided on the transparent conductive film17on the outside of a contact hole CH2, and is electrically connected to the upper electrode14band the p-type amorphous semiconductor layer153via the transparent conductive film17.

In this example, the bias line16is formed by laminating metal films made of titanium (Ti), aluminum (Al), and titanium (Ti), respectively. In the case where the bias line16is in direct contact with the upper electrode14bas in the first embodiment, when there is a portion where the upper electrode14band the p-type amorphous semiconductor layer153are not covered with the lowermost layer made of titanium (Ti), the intermediate layer made of aluminum (Al) is in direct contact with the upper electrode14band the p-type amorphous semiconductor layer153. In this case, the bias line16may be disconnected owing to local electric corrosion of the bias line16, and characteristic defects of a photodiode12may be caused by diffusion of aluminum (Al) into silicon (Si) in a photoelectric conversion layer15.

In the present embodiment, the transparent conductive film17is in contact with the upper electrode14band the p-type amorphous semiconductor layer153, and the bias line16is not in direct contact with the upper electrode14band the p-type amorphous semiconductor layer153. Accordingly, as compared with the configuration of the first embodiment, disconnection of the bias line16and the characteristic defects of the photodiode12are prevented more effectively, whereby a reduction in yield of the active matrix substrate1can be suppressed.

Although the embodiments of the present invention have been described above, the above-described embodiments are merely illustrative examples of possible implementations. Therefore, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate without departing from the spirit and the scope of the present invention.

(1) In each of the above-described embodiments, an X-ray imaging panel can be produced by forming a scintillator4on the active matrix substrate1so as to cover the imaging region of the active matrix substrate1.

(2) In each of the above-described embodiments, the third insulating film105, which is an inorganic insulating film, is provided so as to cover the photodiode12, and the fourth insulating film106, which is an organic insulating film, is provided on the third insulating film105. It is to be noted, however, that the organic insulating film need only be provided as a layer positioned above at least the photodiode12.

(3) Each of the above-described embodiments describes an example where the opening h30of the fourth insulating film106is formed, the upper electrode14bis then formed, and thereafter, the opening h30is expanded through a plasma ashing process. However, the step of expanding the opening h30may be omitted in the following cases. The step of expanding the opening h30may be omitted in the case where, in the above-described step shown inFIG. 5D, the width W1of the opening h1of the upper electrode14bis substantially the same as or smaller than the width W30of the opening h30. In this case, the end portions of the upper electrode14bin the opening h1are not covered with the fourth insulating film106, and accordingly, contact failure between the bias line16to be formed thereafter and the upper electrode14bis less likely to occur.

The above-described active matrix substrate can be described as follows.

The active matrix substrate is an active matrix substrate including: a photoelectric conversion element; an electrode provided with a first opening, the electrode being disposed on one surface of the photoelectric conversion element; an organic insulating film provided with a second opening, the organic insulating film covering the photoelectric conversion element and the electrode; and a conductive film for supplying a bias voltage to the electrode, wherein the first opening and the second opening overlap each other when viewed in plan view, and the conductive film is provided inside the first opening and the second opening so as to be in contact with the electrode (first configuration).

According to the first configuration, the electrode disposed on one surface of the photoelectric conversion element has the first opening and the organic insulating film covering the electrode has the second opening. The first opening and the second opening overlap each other when viewed in plan view, and the conductive film for supplying a bias voltage is provided inside these openings so as to be in contact with the electrode. The first opening is formed in a portion where the conductive film and the electrode are in contact with each other. With this configuration, even if components contained in the electrode and the organic insulating film are deposited on the electrode during the production process of the active matrix substrate, such deposits are less likely to remain in the portion where the conductive film and the electrode are in contact with each other. Accordingly, contact failure between the conductive film and the electrode owing to the presence of the deposits is prevented, whereby a reduction in yield of the active matrix substrate can be suppressed.

In the first configuration, the electrode may be a transparent conductive film that contains indium, at least one of zinc and tin, and oxygen. (second configuration).

In the first or second configuration, the conductive film may be a bias line that is made of a metal material and extends in one direction on the photoelectric conversion element (third configuration).

In the third configuration, the active matrix substrate may be configured such that it further includes an inorganic insulating film provided with a third opening, the inorganic insulating film covering a surface of the electrode and a surface of the photoelectric conversion element, wherein the organic insulating film covers a surface of the inorganic insulating film, and the second opening is formed farther inward than the third opening, and the first opening is formed farther inward than the second opening (fourth configuration).

According to the fourth configuration, the surface of the electrode and the surface of the photoelectric conversion element are covered with the inorganic insulating film. With this configuration, even if moisture has entered the active matrix substrate, the moisture is less likely to penetrate into the surface of the photoelectric conversion element. Furthermore, out of the first opening, second opening, and third opening, the first opening is located on the innermost side. Accordingly, end portions of the electrode in the first opening are not covered with the organic insulating film or the inorganic insulating film, whereby contact failure between the bias line and the electrode is less likely to occur.

In the third configuration, the active matrix substrate may be configured such that it further includes an inorganic insulating film provided with a third opening, the inorganic insulating film covering a surface of the electrode and a surface of the photoelectric conversion element, wherein the organic insulating film covers a surface of the inorganic insulating film, and the second opening and the third opening have rectangular shapes with their long sides extending substantially parallel to an extending direction of the bias line when viewed in plan view (fifth configuration).

According to the fifth configuration, the surface of the electrode and the surface of the photoelectric conversion element are covered with the inorganic insulating film. With this configuration, even if moisture has entered the active matrix substrate, the moisture is less likely to penetrate into the surface of the photoelectric conversion element. Furthermore, the second opening and the third opening have rectangular shapes with their longitudinal direction coincide with the extending direction of the bias line when viewed in plan view. Accordingly, during the production process of the active matrix substrate, disconnection of the bias line owing to the misalignment between the second opening and the third opening in the extending direction of the bias line is less likely to occur.

In the first or second configuration, the conductive film may be made of a transparent conductive material, and the active matrix substrate may further include a bias line that is connected to the conductive film and to which the bias voltage is suppled (sixth configuration).

According to the sixth configuration, a bias voltage is supplied to the electrode from the bias line through the conductive film made of the transparent conductive material. When the bias line has a laminate structure in which a plurality of metal layers are laminated, the bias line may contain a metal that causes electric corrosion and the like when the metal is brought into direct contact with the electrode. With this configuration, the bias line and the electrode are not in direct contact with each other. Accordingly, even if such a metal is contained in the bias line, electric corrosion and the like are less likely to occur.

The above-described X-ray imaging panel may include an active matrix substrate with any of the first to sixth configurations and a scintillator for converting X-rays incident thereon to scintillation light (seventh configuration).

According to the seventh configuration, contact failure between the conductive film and the electrode is less likely to occur, and results of imaging by irradiation with X-rays can be obtained properly.

A method for producing the above-described active matrix substrate can be described as follows.

A method for producing an active matrix substrate is a method including: forming a photoelectric conversion element on a substrate; forming an electrode on one surface of the photoelectric conversion element; forming an organic insulating film that covers the photoelectric conversion element and the electrode and forming an opening of the organic insulating film at a position where the opening overlaps the electrode when viewed in plan view; forming, after the opening of the organic insulating film has been formed, an opening of the electrode at a position where the opening of the electrode overlaps the opening of the organic insulating film when viewed in plan view; and forming a conductive film inside the opening of the electrode and the opening of the organic insulating film so as to be in contact with the electrode (first method).

According to the first method, the opening of the electrode provided on one surface of the photoelectric conversion element and the opening of the organic insulating film covering the electrode overlap each other when viewed in plan view. The conductive film for supplying a bias voltage to the electrode is provided inside these openings so as to be in contact with the electrode. After the electrode has been formed, even if components contained in the electrode and the organic insulating film are deposited on the electrode in the step of forming the opening of the organic insulating film, the opening of the electrode is formed in a portion where the conductive film and the electrode are in contact with each other after the opening of the organic insulating film has been formed. Accordingly, the deposits are less likely to remain in the portion where the conductive film and the electrode are in contact with each other, and contact failure between the conductive film and the electrode owing to the presence of the deposits is less likely to occur. As a result, a reduction in yield of the active matrix substrate can be suppressed.

The first method may be configured such that it further includes, after the opening of the electrode has been formed, expanding the opening of the organic insulating film such that the opening of the organic insulating film is disposed farther outward than the opening of the electrode when viewed in plan view, and the opening of the electrode is formed using the organic insulating film as a mask (second method).

According to the second method, the opening of the electrode is formed using the organic insulating film as a mask. It is thus not necessary to provide a photomask for forming the opening of the electrode separately, whereby the number of steps required for producing the active matrix substrate can be reduced. Furthermore, as a result of expanding the opening of the organic insulating film, the opening of the electrode is located inside the opening of the organic insulating film. Accordingly, unlike the case where the opening of the organic insulating film is located inside the opening of the electrode, the end portions of the organic insulating film in the opening do not protrude farther than the end portions of the electrode. With this configuration, contact between the conductive film and the electrode can be established more reliably.

The first or second method may be configured such that it further includes, after the electrode has been formed, forming an inorganic insulating film that covers a surface of the electrode and a surface of the photoelectric conversion element and forming an opening of the inorganic insulating film at a position where the opening overlap the photoelectric conversion element when viewed in plan view, the opening of the inorganic insulating film overlaps the opening of the organic insulating film and the opening of the electrode when viewed in plan view, and the conductive film is formed inside the opening of the inorganic insulating film, the opening of the organic insulating film, and the opening of the electrode (third method).

According to the third method, the surface of the electrode and the surface of the photoelectric conversion element are covered with the inorganic insulating film. Thus, as compared with the case where they are not covered with the inorganic insulating film, even when moisture has entered the active matrix substrate, the moisture is less likely to penetrate into the surface of the photoelectric conversion element. Furthermore, since the conductive film is formed inside the opening of the inorganic insulating film, the opening of the organic insulating film, and the opening of the electrode, the conductive film can be brought into contact with the electrode.

LIST OF REFERENCE NUMERALS