JPWO2013031128A1 - Two-dimensional image detector and manufacturing method thereof - Google Patents

Abstract

The diameter D of the pixel electrode 25 in the direction in which the bump electrodes 27 are arranged is formed to be relatively smaller than the diameter B of the bump electrodes 27. Therefore, the gap d between the pixel electrodes can be increased, and the tolerance of deviation until the bump electrode 27 comes into contact with the adjacent pixel electrode 25 can be increased. Therefore, it is possible to prevent a pixel defect from occurring due to the positional deviation of the bump electrode 27.

Description

  The present invention relates to a two-dimensional image detector for detecting images such as X-ray radiation, visible light, infrared rays, and the like, and a method for manufacturing the same.

  Conventionally, as this type of device, an active matrix substrate including a plurality of switching elements arranged in a grid pattern, a pixel array layer having a charge storage capacitor and a pixel electrode formed for each switching element, and a pixel array A counter substrate provided with an electrode portion arranged opposite to the layer and a semiconductor layer for converting light or the like into a charge signal, and the active matrix substrate and the counter substrate are electrically connected by a bump electrode formed by screen printing. (For example, refer patent document 1).

  This two-dimensional image detector includes pixel electrodes formed in a grid pattern on a pixel array layer of an active matrix substrate, and this portion and the counter substrate are connected by bump electrodes. In addition, the pixel electrode of the active matrix substrate is formed larger than the bump electrode so as to efficiently collect charges generated in the semiconductor layer of the counter substrate and so that the bump electrode does not protrude.

JP 2008-171833 A

However, the conventional example having such a configuration has the following problems.
That is, the conventional apparatus forms bump electrodes on the pixel electrodes by screen printing, but there is a manufacturing tolerance in the pitch of the plurality of through holes of the metal mask used for screen printing. Therefore, even if the metal mask is accurately aligned with respect to the active matrix substrate, the positional deviation is accumulated from the one end side where the alignment is performed toward the other end side. Misalignment increases. As a result, on the other end side, there may occur a problem that the bump electrode is detached from the pixel electrode or formed across the adjacent pixel electrodes. When the bump electrode is removed from the pixel electrode, the pixel becomes defective. When the bump electrode extends over the two pixel electrodes, the two pixels become defective.

  The present invention has been made in view of such circumstances, and by devising the relative size of the pixel electrode and the bump electrode, the position of the bump electrode can be shifted without making the bump diameter smaller than before. It is an object of the present invention to provide a two-dimensional image detector and a method for manufacturing the same that can prevent pixel defects from being caused by the above.

In order to achieve such an object, the present invention has the following configuration.
That is, the present invention includes an active matrix substrate including a plurality of switching elements arranged in a matrix direction, and a pixel array layer connected to each of the switching elements and including a charge storage capacitor including a pixel electrode, An electrode part formed facing the pixel array layer, and a counter substrate including a semiconductor layer provided between the pixel array layer and the electrode part and converting light or radiation into an electrical signal, The active matrix substrate and the counter substrate are arranged to face each other, and the pixel electrode of the active matrix and the counter substrate are electrically connected by a bump electrode formed by screen printing a conductive paste. In the two-dimensional image detector, the diameter of the pixel electrodes in the arrangement direction is smaller than the diameter of the bump electrodes in the arrangement direction. It is characterized in.

  According to the present invention, the active matrix substrate and the counter substrate are arranged to face each other, and the pixel electrode and the counter substrate are electrically connected by the bump electrodes by screen printing. Since the pixel electrode is formed smaller than the bump electrode, the interval between the pixel electrodes is widened, and the tolerance of deviation until the bump electrode comes into contact with the adjacent pixel electrode can be increased. Therefore, it is possible to prevent the occurrence of pixel defects due to the displacement of the bump electrodes. Even if the pixel electrode is made small, the electrical aperture ratio for collecting the charges collected on the counter substrate is not lowered as long as the size of the bump electrode in contact with the counter substrate is the same as the conventional one. Therefore, the charge collection efficiency is not lowered.

  Further, in the present invention, accumulation of pitch deviation when the pitch of the through holes for forming the bump electrodes at the time of screen printing grows is P, and the diameter of the bump electrodes in the arrangement direction of the bump electrodes is B, When the diameter of the pixel electrode in the arrangement direction of the bump electrode is D and the pitch of the pixel electrode is L, the diameter of the bump electrode and the diameter of the pixel electrode in the arrangement direction of the bump electrode is B / 2 + P <L It is preferable that the relationship of −D / 2 and P−B / 2 <D / 2 is satisfied.

  By satisfying the above two conditions, the bump electrode does not come into contact with the adjacent pixel electrode, and the bump electrode does not come off the pixel electrode.

  In the present invention, the semiconductor layer is preferably a CdTe or CdZnTe compound semiconductor.

  When the semiconductor layer is a CdTe or CdZnTe compound semiconductor, the active matrix substrate and the counter substrate are bonded to each other, and a connection is made with a bump electrode. Therefore, the effect can be most expected when the semiconductor layer is composed of these semiconductors.

  The present invention also provides an active matrix substrate including a plurality of switching elements arranged in a matrix direction and a pixel array layer connected to each of the switching elements and including a charge storage capacitor including a pixel electrode, An electrode unit formed opposite to the pixel array layer; and a counter substrate including a semiconductor layer provided between the pixel array layer and the electrode unit and converting light or radiation into an electric signal. In the method for manufacturing a two-dimensional image detector, a first step of forming an active matrix substrate including the pixel array layer and the switching elements, and a conductive paste bump on each pixel electrode of the active matrix substrate by screen printing A second step of forming an electrode; a third step of forming a counter substrate including the electrode portion and the semiconductor layer; and The pixel array layer and the semiconductor layer of the two substrates are electrically connected by the bump electrodes so that the pixel array layer of the Rix substrate and the semiconductor layer of the counter substrate face each other. And the diameter of the pixel electrodes in the arrangement direction in the first step is smaller than the diameter of the bump electrodes in the arrangement direction in the second step. .

  According to the present invention, an active matrix substrate is formed in the first step, a bump electrode is formed on each pixel electrode of the active matrix substrate in the second step, and a counter substrate is formed in the third step. The matrix substrate and the counter substrate are opposed to each other, and the pixel array layer and the semiconductor layer are electrically connected by a bump electrode formed by screen printing. Since the pixel electrode is formed smaller than the bump electrode, the interval between the pixel electrodes is widened, and the tolerance of deviation until the bump electrode comes into contact with the adjacent pixel electrode can be increased. Therefore, it is possible to prevent the occurrence of pixel defects due to the displacement of the bump electrodes.

  According to the two-dimensional image detector according to the present invention, the active matrix substrate and the counter substrate are arranged to face each other, and the pixel electrode and the counter substrate are electrically connected by the bump electrodes by screen printing. Since the pixel electrode is formed smaller than the bump electrode, the interval between the pixel electrodes is widened, and the tolerance of deviation until the bump electrode comes into contact with the adjacent pixel electrode can be increased. Therefore, it is possible to prevent the occurrence of pixel defects due to the displacement of the bump electrodes.

It is a longitudinal cross-sectional view which shows the 1st process of manufacturing the two-dimensional image detector which concerns on an Example. It is a longitudinal cross-sectional view which shows the 2nd process which manufactures the two-dimensional image detector which concerns on an Example, (a) shows the state which has arrange | positioned the metal mask, (b) shows the state which has arrange | positioned the electrically conductive paste. (C) shows a state in which the squeegee is moved. It is a longitudinal cross-sectional view which shows the 3rd process of manufacturing the two-dimensional image detector which concerns on an Example. It is a longitudinal cross-sectional view which shows the 4th process of manufacturing the two-dimensional image detector which concerns on an Example. It is a schematic diagram for demonstrating accumulation | storage of the pitch shift by the tolerance of a metal mask. It is a schematic diagram for demonstrating the conditions which make a bump electrode not straddle the adjacent pixel electrode. It is a schematic diagram for demonstrating the conditions which make a bump electrode not remove | deviate from a pixel electrode.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a first step of manufacturing the two-dimensional image detector according to the embodiment. FIG. 2 is a longitudinal sectional view showing a second step of manufacturing the two-dimensional image detector according to the embodiment, where (a) shows a state where a metal mask is arranged, and (b) shows a conductive paste is arranged. (C) shows a state where the squeegee is moved. FIG. 3 is a longitudinal sectional view showing a third step of manufacturing the two-dimensional image detector according to the embodiment, and FIG. 4 shows a fourth step of manufacturing the two-dimensional image detector according to the embodiment. It is a longitudinal cross-sectional view.

First step (FIG. 1)
In the first step, the active matrix substrate 1 is formed. In the active matrix substrate 1, a gate electrode 5 and a reference potential electrode 7 made of a metal film such as Ta (tantalum), Al (aluminum), and Mo (molybdenum) are formed on the upper surface of the insulating substrate 3. As the insulating substrate 3, for example, Corning # 7059 or # 1737 can be used. In addition, the gate electrode 5 and the reference potential electrode 7 are formed, for example, by sputtering deposition with the metal film having a thickness of about 4000 angstroms.

  Next, the first insulating layer 9 is deposited on the gate electrode 5 and the reference potential electrode 7 described above. The first insulating layer 9 is formed with a thickness of about 3500 angstroms using, for example, SiNx (silicon nitride) or SiOx (silicon oxide) by a CVD (Chemical Vapor Deposition) method. The first insulating layer 9 functions as a gate insulating film and constitutes a pixel array layer 13 having a charge storage capacity in relation to the pixel electrode layer 11 and the reference potential electrode 7.

Next, a channel portion 15 is formed in the first insulating layer 9 on the gate electrode 5. The channel portion 15 is formed by, for example, depositing a-Si (amorphous silicon) with a thickness of about 1000 angstroms by using the CVD method, and then diffusing impurities to form an n ⁺ layer and patterning it in a desired shape. Formed.

  Next, the drain electrode 17 is deposited on the channel portion 15, and the pixel electrode layer 11 is deposited from the channel portion 15 over the first insulating layer 9 on the reference potential electrode 7. The drain electrode 17 and the pixel electrode layer 11 are formed with a metal film of Ta (tantalum), Al (aluminum), Ti (titanium) or the like with a thickness of about 4000 angstroms using, for example, sputter deposition.

  The first insulating layer 9, the pixel electrode layer 11, the gate electrode 5, the drain electrode 17, and the channel portion 15 constitute a switching element 19.

  Next, a second insulating layer 23 is deposited so as to cover the pixel electrode layer 11 corresponding to the reference potential electrode 7. However, the second insulating layer 23 covers a region excluding the opening 21 of the pixel electrode layer 11. The second insulating layer 23 is formed of an insulating film such as SiNx or SiOx with a thickness of about 6000 angstroms using, for example, a CVD method. In addition to the inorganic film, an organic film such as acrylic or polyimide can be used as the second insulating layer 23.

  Further, a filler 24a is deposited so as to cover the pixel array layer 13 and the switching element 19, and a contact hole 24b communicating with the opening 21 is formed in the filler 24a. An insulating film 24c is formed on the upper surface of the filler 24a except for the contact hole 24b. A pixel electrode 25 is formed in the contact hole 24b. The pixel electrode 25 is electrically connected to the pixel electrode layer 11 through the contact hole 24 b and the opening 21. The pixel electrode 25 is formed of a transparent electrode such as ITO (Indium Tin Oxide). The pixel electrode 25 is formed such that the diameter in the direction in which bump electrodes described later are arranged is shorter than the diameter of the bump electrode in the direction in which bump electrodes described later are arranged.

  In the active matrix substrate 1 described above, an inverted staggered type using amorphous silicon is exemplified as the switching element 19. However, for example, polysilicon (p-Si) may be used. Staggered) type may be adopted. Further, in FIG. 1, only a single switching element 19 is illustrated, but a plurality of switching elements 19 are arranged in a lattice shape in plan view.

Second step (FIG. 2)
In the second step, the bump electrode 27 is formed. In the following description, for the sake of illustration, in FIG. 2 to FIG. 7, the above-described filler 24 a, contact hole 24 b, and insulating film 24 c are omitted, and the pixel electrode 25 is disposed in the opening 21. It is drawn in.

  As shown in FIG. 2A, a metal mask 29 is disposed on the active matrix substrate 1 described above. The metal mask 29 has through holes 31 corresponding to the positions of the pixel electrodes 25 formed on the active matrix substrate 1. However, since manufacturing tolerances exist, even if the metal mask 29 is accurately aligned with respect to the active matrix substrate 1 on one end side, manufacturing tolerances are accumulated on the other end side, and the pixel electrode 25 on the other end side is accumulated. On the other hand, the position of the through hole 31 is shifted.

  The through hole 31 is formed such that the diameter in the direction in which the through holes 31 are arranged is larger than the diameter of the pixel electrode 25 in that direction. In other words, the through hole 31 is formed in a size that completely surrounds the pixel electrode 25 in plan view.

  As shown in FIG. 2B, the squeegee 33 is disposed on one side of the metal mask 29, and the conductive paste 35 is disposed on the contact portion between the squeegee 33 and the metal mask 29. The conductive paste 35 includes, for example, a base material mainly composed of rubber and a conductive material mainly composed of carbon and a binder resin in which an organic substance is gradually volatilized and cured when left at room temperature. It is a thing. About the electroconductive material contained in the electroconductive paste 35, if it has electroconductivity, an appropriate material can be used.

  As shown in FIG. 2C, the squeegee 33 is moved from one side to the other while being pressed against the active matrix substrate 1. Then, the conductive paste 35 is transferred to each pixel electrode 25 through the through hole 31 of the metal mask 29. By moving the squeegee 33 over the entire surface of the metal mask 29, bump electrodes 27 are formed on all the pixel electrodes 25 formed on the active matrix substrate 1.

Third step (FIG. 3)
In the third step, the counter substrate 37 is formed.

  An upper bias electrode 39 is formed on one surface. The upper bias electrode 39 is made of a conductive film such as ITO or Au (gold). However, in the case of a two-dimensional image detector that performs imaging with visible light, the upper bias electrode 39 is made of a transmissive material (for example, ITO).

  Next, the first charge blocking layer 41 is formed on the entire surface of the upper bias electrode 39. Examples of the first charge blocking layer 41 include a p-type semiconductor layer made of ZnTe or the like. Further, the semiconductor layer 43 is formed on the lower surface of the charge blocking layer 41. For example, the semiconductor layer 43 is a divisor of CdTe (Cadmium Telluride) or CdZnTe (Cadmium Zinc Telluride) compound semiconductor using a metal organic chemical vapor deposition (MOCVD) method. It is formed by forming a film with a thickness of 100 μm.

  Then, the second charge blocking layer 45 is formed on the lower surface of the semiconductor layer 43 on the opposite side of the upper bias electrode 39 across the semiconductor layer 43. The second charge blocking layer 45 is composed of an n-type semiconductor layer made of, for example, CdS (Cadmium Sulfide) or ZnS (Zinc Sulfide).

  In the counter substrate 37 described above, a photoconductive i-type semiconductor layer 43 is sandwiched between a first charge blocking layer (p-type semiconductor layer) 41 and a second charge blocking layer (n-type semiconductor layer) 45. A pin photodiode structure. Therefore, dark current when X-rays are not irradiated is suppressed, and sensor characteristics with an excellent S / N ratio can be obtained.

  The structure of the counter substrate 37 is not limited to the pin type described above, and may be a Schottky junction type, a MIS (Metal-Insulator Semiconductor) junction type, or the like. Further, depending on the required specifications, one or both of the first charge blocking layer 41 and the second charge blocking layer 45 may be omitted.

Fourth step (FIG. 4)
In the fourth step, electrical connection is performed by the bump electrode 27.

  The active matrix substrate 1 manufactured as described above and the counter substrate 37 are bonded together. The counter substrate 37 is bonded to the pixel electrode 25 and bump electrode 27 side of the active matrix substrate 1 with the second charge blocking layer 45 side facing. By leaving at room temperature in this state, the active matrix substrate 1 and the counter substrate 37 are electrically and mechanically connected to complete the two-dimensional image detector.

  As described above, the pixel electrode 25 is formed smaller than the bump electrode 27. The advantages will be described with reference to FIG. FIG. 5 is a schematic diagram for explaining the accumulation of pitch deviation due to the tolerance of the metal mask.

  Here, it is assumed that in the second step described above, the through hole 31 of the metal mask 29 and the pixel electrode 25 at the right end of the active matrix substrate 1 are aligned to form the bump electrode 27. Further, in the metal mask 29, it is assumed that pitch deviations of the through holes 41 are accumulated from the right end to the left end due to manufacturing tolerances.

The meanings of the symbols in FIG. 5 are as follows.
P: Accumulation length of pitch deviation at the left end where the deviation of the through hole 31 is accumulated most due to tolerance B: Diameter of the bump electrode 27 in the arrangement direction of the bump electrode 27 D: Size of the pixel electrode 25 in the arrangement direction of the bump electrode 27 Diameter L: Pitch of the pixel electrodes 25 in the arrangement direction of the bump electrodes 27 d: Arrangement interval of the pixel electrodes 25 in the arrangement direction of the bump electrodes 27

  As shown in FIG. 5, the center of the pixel electrode 25 and the bump electrode 27 at the right end coincide with each other. However, in this embodiment, the through hole 31 of the metal mask 29 is formed such that the diameter in the direction in which the through holes 31 are arranged is larger than the diameter of the pixel electrode 25 in that direction. That is, the diameter of the pixel electrode 25 in the direction in which the bump electrodes 27 are arranged is formed to be relatively smaller than the diameter of the bump electrodes 27. In other words, the bump electrode 27 is formed relatively larger than the pixel electrode 25. Therefore, the gap d between the pixel electrodes can be increased, and the tolerance of deviation until the bump electrode 27 comes into contact with the adjacent pixel electrode 25 can be increased. Therefore, it is possible to prevent a pixel defect from occurring due to the positional deviation of the bump electrode 27.

  The area where the bump electrode 27 and the counter substrate 37 are in contact affects the collection efficiency of the charges collected on the counter substrate 37. The pixel electrode 25 is formed to have an area smaller than that of the bump electrode 27. However, if the size of the bump electrode 27 is the same as the conventional one, the contact area between the bump electrode 27 and the counter substrate 37 does not change. The numerical aperture ratio can be made equivalent. As a result, while maintaining the charge collection efficiency, it is possible to prevent problems due to the deviation of the bump electrode 27 due to the manufacturing tolerance of the through hole 31 of the metal mask 29.

  The relationship between the bump electrode 27 and the pixel electrode 25 in the arrangement direction preferably satisfies the following two conditional expressions.

  B / 2 + P <LD-2 (1)

  P−B / 2 <D / 2 (2)

  The above equation (1) will be described with reference to FIG. FIG. 6 is a schematic diagram for explaining conditions for preventing the bump electrode from straddling adjacent pixel electrodes.

  FIG. 6 shows a state in which the bump electrode 27 extends over adjacent pixel electrodes 25. In this state, the sum of B / 2, which is half the diameter of the bump electrode 27, and P, which is the maximum deviation (accumulation length of pitch deviation) of the center position between the pixel electrode 25 and the bump electrode 27, is the pixel electrode. It is equal to the difference between L, which is 25 pitches, and D / 2, which is half the diameter of the pixel electrode 25. Therefore, each pixel electrode 25 is preferably formed such that the difference between the pitch L and the length D / 2 is larger than B / 2 + P. Thereby, the malfunction resulting from the bump electrode 27 straddling the adjacent pixel electrode 25 can be prevented.

  Regarding the above equation (2), FIG. 7 is a schematic diagram for explaining conditions for preventing the bump electrode from being detached from the pixel electrode.

  FIG. 7 shows a state where the bump electrode 27 is detached from the pixel electrode 25. In this state, the difference between the pitch shift accumulation length P and B / 2 which is half the diameter of the bump electrode 27 is equal to D / 2 which is half the diameter of the pixel electrode 25. Therefore, the electrode pixel 25 is preferably formed such that its length D / 2 is greater than the difference between the pitch shift accumulation length P and the length B / 2. As a result, a problem that the bump electrode 27 is detached from the pixel electrode 25 can be prevented.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In the above-described embodiments, the semiconductor layer 43 is composed of a compound semiconductor of CdTe or CdZnTe. However, the present invention is not limited to the material of the semiconductor layer 43, and can be applied to any two-dimensional image detector that connects the active matrix substrate 1 and the counter substrate 37 using the bump electrodes 37. .

  (2) In the embodiment described above, the pixel electrode 25 is formed so as to satisfy the expressions (1) and (2). However, in the present invention, the pixel electrode 25 is smaller than the bump electrode 27 even if these expressions are not satisfied. If it is formed, it is possible to improve the defect caused by the pitch deviation as compared with the conventional case.

  As described above, the present invention is suitable for a two-dimensional image detector that detects an image and a manufacturing method thereof.

DESCRIPTION OF SYMBOLS 1 ... Active matrix substrate 3 ... Insulating substrate 5 ... Gate electrode 11 ... Pixel electrode layer 19 ... Switching element 25 ... Pixel electrode 27 ... Bump electrode 29 ... Metal mask 31 ... Through-hole 37 ... Opposite substrate 43 ... Semiconductor layer P ... Semiconductor layer P ... Accumulation length B ... Bump electrode diameter D ... Pixel electrode diameter L ... Pixel electrode pitch d ... Pixel electrode arrangement interval

Claims (4)

An active matrix substrate including a plurality of switching elements arranged in a matrix direction, and a pixel array layer connected to each of the switching elements and including a charge storage capacitor including a pixel electrode, and facing the pixel array layer And a counter substrate including a semiconductor layer that is provided between the pixel array layer and the electrode unit and converts light or radiation into an electric signal, and is opposed to the active matrix substrate. In the two-dimensional image detector, wherein the active matrix pixel electrode and the counter substrate are electrically connected to each other by a bump electrode formed by screen printing a conductive paste. ,
The two-dimensional image detector, wherein a diameter of the pixel electrode in the arrangement direction is smaller than a diameter of the bump electrode in the arrangement direction. The two-dimensional image detector according to claim 1,
When the pitch of the through holes for forming the bump electrodes at the time of the screen printing is increased, accumulation of pitch deviation is set as P, the diameter of the bump electrodes in the arrangement direction of the bump electrodes is set as B, and in the arrangement direction of the bump electrodes. When the diameter of the pixel electrode is D and the pitch of the pixel electrodes is L, the diameter of the bump electrode and the diameter of the pixel electrode in the bump electrode arrangement direction are B / 2 + P <LD / 2, and , P−B / 2 <D / 2, and a two-dimensional image detector. The two-dimensional image detector according to claim 1 or 2,
The two-dimensional image detector, wherein the semiconductor layer is a CdTe or CdZnTe compound semiconductor. An active matrix substrate including a plurality of switching elements arranged in a matrix direction, and a pixel array layer connected to each of the switching elements and including a charge storage capacitor including a pixel electrode, and facing the pixel array layer And a counter substrate including a semiconductor layer that converts light or radiation into an electrical signal, and is provided between the pixel array layer and the electrode unit. In the manufacturing method,
A first step of forming an active matrix substrate including the pixel array layer and the switching element;
A second step of forming a bump electrode by screen printing a conductive paste on each pixel electrode of the active matrix substrate;
A third step of forming a counter substrate including the electrode portion and the semiconductor layer;
The pixel array layer and the semiconductor layer of both substrates are electrically connected by the bump electrodes so that the pixel array layer of the active matrix substrate and the semiconductor layer of the counter substrate face each other. And a fourth step of connecting to
2. A two-dimensional image detector according to claim 1, wherein a diameter in the arrangement direction of the pixel electrodes in the first step is formed smaller than a diameter in the arrangement direction of the bump electrodes in the second step. Method.

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