Backside illuminated photodiode and detector

Abstract

The invention provides a backside illuminated photodiode which can be applied to the technical field of photodiodes. The backside illuminated photodiode includes: a substrate; the first doped region is arranged on the front surface of the substrate; the second doped region is arranged on the front surface of the substrate, the second doped region and the first doped region are arranged at an interval, and the doping type of the second doped region is different from that of the first doped region; the first electrode is electrically connected with the first doped region; the first doped region is electrically connected with the first electrode, the second doped region is electrically connected with the second electrode, the second electrodes are electrically connected with the second doped region, the second electrodes are arranged at intervals along a first direction and a second direction, the first direction is perpendicular to the second direction, and the second electrodes are arranged to surround the first electrode and are separated from the first electrode. The invention also provides a detector.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic technology, and more specifically, to a back-illuminated photodiode and a detector. Background Art

[0002] In traditional X-ray nondestructive testing equipment such as CT, the front-illuminated photodiode (PD) is responsible for converting the photons emitted by the scintillator into current as part of the detector system, and integrating the current through electronics to obtain the X-ray intensity in space. However, since the electrode of the front-illuminated PD is located on the light incident surface, the area of ​​the PD receiving scintillator photons is reduced, and the signal of the electrode needs to be connected to the printed circuit board (PCB) substrate through metal binding wires, which further limits the pixel density. Therefore, the front-illuminated PD array is limited in dense arrangement. In addition, due to the wire bonding connection between the detector and the substrate, the detector cannot be completely tiled side by side in two dimensions. In addition to these limiting factors, if the pixel density of the PD exceeds a certain range, the performance of the detector will begin to decline due to factors such as coverage efficiency, crosstalk, and noise.

[0003] Back-illuminated PD overcomes the limitations of traditional front-illuminated PD. Compared with traditional front-illuminated PD, back-illuminated PD has smaller pixel pitch and higher space utilization efficiency. The electrode of back-illuminated PD is located on the side where PD is coupled with PCB substrate, and is coupled with substrate through flip chip process, so its light incident surface can be fully coupled with scintillator, and the spacing between pixels is not limited by wire bonding factors, so two-dimensional tiling can be achieved.

[0004] When the back-illuminated PD is coupled with the PCB substrate, the accuracy and stability of the flip-chip process determine the quality and cost of the area array PD. When the electrode area of ​​the back-illuminated PD is small, or the distance between the cathode electrode and the anode electrode is small, in order to avoid the problem of short circuit between the cathode electrode and the anode electrode, it is necessary to add a ball planting step during the flip-chip process. The ball planting process is costly and requires high precision. Otherwise, the position of the corresponding contact points between the PD and the substrate may deviate, and there may be a gap between the implanted gold ball and the corresponding contact point of the substrate, resulting in a disconnection between the PD and the substrate, thereby affecting the overall yield of the area array detector. Summary of the invention

[0005] In view of the above problems, the present disclosure provides a back-illuminated photodiode, which is coupled to a PCB substrate through a conductive silver paste, thereby eliminating the ball implantation step in the flip-chip process and reducing the packaging cost of the area array detector.

[0006] According to a first aspect of the present disclosure, there is provided a back-illuminated photodiode, comprising: a substrate; a first doping region, arranged on the front side of the substrate; a second doping region, arranged on the front side of the substrate and spaced apart from the first doping region, the second doping region and the first doping region having a different doping type; a first electrode, electrically connected to the first doping region; and a plurality of second electrodes, electrically connected to the second doping region, the plurality of second electrodes being spaced apart along a first direction and a second direction, wherein the first direction is perpendicular to the second direction, and wherein the plurality of second electrodes are arranged to surround the first electrode and spaced apart from the first electrode.

[0007] According to an embodiment of the present disclosure, a straight line at which the minimum distance between the plurality of second electrodes and the first electrode is located is along a third direction, wherein the third direction intersects with the first direction and the second direction.

[0008] According to an embodiment of the present disclosure, the minimum distance between the plurality of second electrodes and the first electrode is greater than or equal to 0.3 mm.

[0009] According to an embodiment of the present disclosure, the shape of the first electrode is a continuous closed figure.

[0010] According to an embodiment of the present disclosure, each second electrode is L-shaped, and each second electrode includes a first portion extending along the first direction and a second portion extending along the second direction.

[0011] According to an embodiment of the present disclosure, the second electrode includes a first endpoint, a second endpoint and a corner point, the first endpoint is the endpoint of the first portion closest to the first electrode, the second endpoint is the endpoint of the second portion closest to the first electrode, the corner point is located at the intersection of the first portion and the second portion and faces the first electrode; and the minimum distance is the minimum value of the distance between the first endpoint and the first electrode, the distance between the second endpoint and the first electrode, and the distance between the corner point and the first electrode.

[0012] According to an embodiment of the present disclosure, each of the second electrodes has the same shape, and the first portion and the second portion of each of the second electrodes have the same shape.

[0013] According to an embodiment of the present disclosure, a line connecting the second endpoints of the plurality of second electrodes extends through the first electrode, and / or a line connecting the first endpoints of the plurality of second electrodes extends through the first electrode.

[0014] According to an embodiment of the present disclosure, the orthographic projections of the plurality of second electrodes on the substrate are spaced apart from the orthographic projections of the first doping region on the substrate.

[0015] According to an embodiment of the present disclosure, the back-illuminated photodiode further includes: a first via hole, through which the first electrode is electrically connected to the first doped region, wherein the ratio of the area of ​​the first via hole to the area of ​​the first electrode is greater than or equal to 0.2.

[0016] According to an embodiment of the present disclosure, the back-illuminated photodiode also includes: a plurality of second vias, the positions of the second vias correspond to the positions of the second electrodes, each of the second electrodes is electrically connected to the second doped region through a corresponding second via, wherein the area of ​​the first via is larger than the area of ​​the second via.

[0017] According to an embodiment of the present disclosure, the area of ​​the first via hole is 5 times greater than the area of ​​the second via hole.

[0018] According to an embodiment of the present disclosure, the orthographic projection of the second via hole on the substrate falls within the range of the orthographic projection of the second electrode on the substrate.

[0019] According to an embodiment of the present disclosure, the first electrode is circular in shape, the first doping region is rectangular in shape, and the first via hole is rectangular in shape.

[0020] According to an embodiment of the present disclosure, the shape of the orthographic projection of the second doping region on the substrate is a ring, or the shape of the orthographic projection of the second doping region on the substrate is the same as the shape of the second electrode, and the width of the second doping region is less than or equal to the width of the second electrode.

[0021] A second aspect of the present disclosure provides a detector, comprising a plurality of back-illuminated photodiodes as described in any one of the above items, wherein the plurality of back-illuminated photodiodes are arranged in an array.

[0022] According to an embodiment of the present disclosure, the detector further includes a conductive silver paste and a substrate, and the first electrodes and the second electrodes of the plurality of back-illuminated photodiodes are coupled to the substrate through the conductive silver paste.

[0023] According to the embodiments of the present disclosure, by reasonably setting the electrode shape of the back-illuminated photodiode and increasing the distance between the cathode electrode (i.e., the second electrode) and the anode electrode (i.e., the first electrode) of the back-illuminated photodiode, the ball implantation step in the flip chip process can be omitted, and the packaging cost of the area array detector can be reduced. In addition, increasing the distance between the cathode electrode and the anode electrode can effectively reduce the risk of short circuit between the cathode electrode and the anode electrode, and improve the packaging yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0025] Figure 1 A schematic diagram schematically shows a planar structure of a back-illuminated photodiode according to an embodiment of the present disclosure;

[0026] Figure 2 A schematic diagram schematically shows the electrode shape of a back-illuminated photodiode according to an embodiment of the present disclosure;

[0027] Figure 3 A schematic diagram schematically shows a first doping region in a back-illuminated photodiode according to an embodiment of the present disclosure;

[0028] Figure 4 A schematic diagram of a first via hole in a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown;

[0029] Figure 5 A schematic diagram of a second doping region in a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown;

[0030] Figure 6 A schematic diagram of a second doping region in a back-illuminated photodiode according to another embodiment of the present disclosure is schematically shown;

[0031] Figure 7 Schematically shows a cross-sectional view of a back-illuminated photodiode according to an embodiment of the present disclosure;

[0032] Figure 8 schematically shows a cross-sectional view of a back-illuminated photodiode according to another embodiment of the present disclosure;

[0033] Fig. 9 schematically shows a cross-sectional view of a back-illuminated photodiode connected to a substrate according to an embodiment of the present disclosure;

[0034] Fig.10 A flowchart schematically shows a method for manufacturing a back-illuminated photodiode according to an embodiment of the present disclosure; and

[0035] Fig.11 A schematic diagram schematically shows an arrangement of back-illuminated photodiodes in a detector according to an embodiment of the present disclosure.

[0036] The reference numerals related to the above drawings are as follows:

[0037] 1. Back-illuminated photodiode; 2. Substrate; 3. First doped region; 4. Second doped region; 5. First electrode; 6. Second electrode; 61. First portion; 62. Second portion; 601. First endpoint; 602. Second endpoint; 603. Corner point; 7. First via hole; 8. Second via hole; 9. Conductive silver paste; 10. PCB substrate; 11. Insulating layer; 12. Detector.

[0038] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the size of the overall / partial structure or the overall / partial area may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. The provided illustrations are only used to illustrate the basic concept of the present disclosure in a schematic manner, and only the structures related to the present disclosure are shown in the drawings instead of being drawn according to the structures in actual implementation. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0040] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0041] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0042] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0043] In order to improve the performance of back-illuminated photodiode arrays in X-ray non-destructive testing equipment such as CT and reduce the problems of electrode short circuit and open circuit introduced in the packaging process, the present invention discloses a back-illuminated photodiode, which eliminates the ball planting step in the flip-chip process by increasing the distance between the cathode electrode and the anode electrode and increasing the width of the cathode electrode; directly uses conductive silver glue to couple the photodiode electrode to the PCB substrate, thereby reducing the packaging cost and improving the photodiode array processing yield.

[0044] Figure 1The schematic diagram of the planar structure of the back-illuminated photodiode according to the embodiment of the present disclosure is schematically shown. It should be noted that: Figure 1 The examples shown are only examples to which the embodiments of the present disclosure can be applied to help those skilled in the art understand the technical content of the present disclosure, and are not limited to Figure 1 The size, configuration and shape of the back-illuminated photodiode are shown.

[0045] like Figure 1 As shown, the back-illuminated photodiode 1 includes a substrate 2, a first doping region 3, a second doping region 4, a first electrode 5 and a plurality of second electrodes 6. The first doping region 3 is arranged on the front side of the substrate 2, and the second doping region 4 is arranged on the front side of the substrate 2, and is spaced apart from the first doping region 3. The second doping region 4 and the first doping region 3 have different doping types. The first electrode 5 is electrically connected to the first doping region 3. The plurality of second electrodes 6 are electrically connected to the second doping region 4, and the plurality of second electrodes 6 are spaced apart along a first direction D1 and a second direction D2. Exemplarily, the first direction D1 is perpendicular to the second direction D2. In the embodiment of the present disclosure, the first electrode 5 is an anode electrode, and the second electrode 6 is a cathode electrode. The present disclosure does not explicitly limit the first direction and the second direction. The first direction and the second direction may be any directions. Those skilled in the art may set the first direction and the second direction according to actual needs. For example, the first direction may be a horizontal direction, and the second direction may be a vertical direction. Please refer to the following Figure 6 The cross-sectional view of the back-illuminated photodiode shown in Figure 1 shows the Figure 1 The positional relationship between the substrate, doped region and electrodes.

[0046] Exemplarily, the back side of the substrate 2 is a light incident side, and the front side is a device side. The first doping region 3, the second doping region 4, the first electrode 5, and the plurality of second electrodes 6 are arranged on the device side. Figure 1 The schematic diagram of the planar structure of the back-illuminated photodiode 1 shown is a view of the device surface of the substrate 2. The first doping region 3 and the second doping region 4 are both located on the front side of the substrate 2 and are arranged at intervals in the horizontal direction. The doping types can be set for the substrate 2, the first doping region 3 and the second doping region 4. For example, the substrate 2 can be set as an N-type substrate, the first doping region 3 is injected with impurities to form a P+ doping region, and the second doping region 4 is injected with impurities to form an N+ doping region. The doping concentration of the second doping region 4 is greater than the doping concentration of the substrate 2. The anode electrode and the cathode electrode are respectively used to control the potential of the P+ doping region and the N+ doping region, and to lead out holes and electrons respectively. The doping types of the above-mentioned substrate 2, the first doping region 3 and the second doping region 4 are only examples. Those skilled in the art can also set other doping types for them, for example, the first doping region 3 is set as an N+ doping region, the second doping region 4 is set as a P+ doping region, etc., which will not be elaborated in detail here.

[0047] In some embodiments, a plurality of second electrodes 6 are disposed to surround the first electrode 5 and to be spaced apart from the first electrode 5 . Figure 1 4 second electrodes 6 are shown in FIG. 4 . The four second electrodes 6 are distributed in four directions of the first electrode 5 . Each second electrode 6 is spaced apart from the first electrode 5 by a predetermined distance. Figure 1 What is shown are merely examples to which the embodiments of the present disclosure can be applied, in order to help those skilled in the art understand the technical content of the present disclosure. In fact, the number of second electrodes 6 can be other values, such as 2, 3, 5, 6, etc., and multiple second electrodes 6 can be distributed in different directions of the first electrode 5.

[0048] According to an embodiment of the present disclosure, the straight line at which the minimum distance between the multiple second electrodes 6 and the first electrode 5 is located is along the third direction D3, wherein the third direction D3 intersects with the first direction D1 and the second direction D2. The minimum distance between the multiple second electrodes 6 and the first electrode 5 refers to the minimum value of the distance between any point on the second electrode 6 and any point on the first electrode 5. The third direction D3 is a direction different from the first direction D1 and the second direction D2. The third direction D3 may be a direction having an acute angle with the first direction D1. For example, the acute angle may be 30 degrees, 45 degrees, 50 degrees, 60 degrees, etc. The sizes of the acute angles listed here are only examples. The angle between the third direction D3 and the first direction D1 may be any acute angle. For example, Figure 1 In the schematic diagram of the back-illuminated photodiode shown, the angle between the third direction D3 and the first direction D1 is 45 degrees.

[0049] Exemplarily, the minimum distance between the plurality of second electrodes 6 and the first electrode 5 is greater than or equal to 0.3 mm.

[0050] Traditional back-illuminated photodiodes are coupled to substrates through a flip-chip process. The distance between the cathode electrode and the anode electrode of the back-illuminated photodiode is small. When the traditional back-illuminated photodiode is coupled to the substrate, there is a problem of short circuit between the cathode electrode and the anode electrode. The embodiments of the present disclosure can prevent the cathode electrode from contacting the anode electrode by increasing the distance between the cathode electrode and the anode electrode. Specifically, the minimum distance between the cathode electrode and the anode electrode is set to be greater than or equal to 0.3 mm. When the back-illuminated photodiode is coupled to the substrate, a short circuit between the cathode electrode and the anode electrode can be avoided, thereby improving the performance of the back-illuminated photodiode array in X-ray non-destructive testing equipment such as CT.

[0051] Figure 2 A schematic diagram schematically shows the electrode shape of a back-illuminated photodiode according to an embodiment of the present disclosure.

[0052] According to an embodiment of the present disclosure, the shape of the first electrode 5 is a continuous closed figure. The shape of the first electrode 5 can be a quadrilateral, a regular hexagon, a regular octagon, an ellipse, etc. The present disclosure does not limit the specific shape of the first electrode 5, and those skilled in the art can set the shape of the first electrode 5 according to actual needs.

[0053] Figure 2 The electrode shape shown is only one embodiment of the present disclosure. For example, Figure 2 The shape of the first electrode 5 shown is a circle. In this case, the minimum distance between the first electrode 5 and the second electrode 6 is the distance from a point on the circumference to the second electrode 6. In fact, the direction of the minimum distance is perpendicular to the tangent of the circle.

[0054] In some embodiments, each second electrode 6 is L-shaped, and each second electrode 6 includes a first portion 61 extending along a first direction and a second portion 62 extending along a second direction. Specifically, the first portion 61 may extend in a horizontal direction, and the second portion 62 may extend in a vertical direction. Figure 2 As shown, the second electrode 6 is four L-shaped electrodes distributed around the first electrode 5 , and the L-shaped electrode includes a first portion 61 and a second portion 62 . The first portion 61 of each L-shaped electrode extends in a horizontal direction, and the second portion 62 extends in a vertical direction.

[0055] According to an embodiment of the present disclosure, the second electrode 6 includes a first endpoint 601, a second endpoint 602 and a corner point 603, the first endpoint 601 is the endpoint of the first portion 61 closest to the first electrode 5, the second endpoint 602 is the endpoint of the second portion 62 closest to the first electrode 5, and the corner point 603 is located at the intersection of the first portion 61 and the second portion 62 and faces the first electrode 5; the minimum distance is the minimum value of the distance between the first endpoint 601 and the first electrode 5, the distance between the second endpoint 602 and the first electrode 5, and the distance between the corner point 603 and the first electrode 5. When the second electrode 6 is an L-shaped electrode, the minimum distance between the first electrode 5 and the second electrode 6 can be determined based on the distance between the three intersection points of the L-shaped electrode close to the first electrode 5 and the first electrode 5, for example, Figure 2 In the case of the electrode shape shown, the minimum distance is the distance between the first endpoint 601 or the second endpoint 602 and the first electrode 5, that is, the distance between the first endpoint 601 and the tangent point of the circle, or the distance between the second endpoint 602 and the tangent point of the circle. Further, when the minimum distance is greater than or equal to 0.3 mm, the back-illuminated photodiode 1 is coupled to the substrate to avoid a short circuit between the first electrode 5 and the second electrode 6.

[0056] In some embodiments, when the shape of the second electrode 6 is L-shaped, the minimum distance between the first electrode 5 and the second electrode 6 may also be the distance between the corner point 603 of the second electrode 6 and the first electrode 5. For example, when the distance between the corner point 603 and the first electrode 5 is less than the distance between the first endpoint 601 and the first electrode 5 and the distance between the second endpoint 602 and the first electrode 5, the distance between the corner point 603 of the second electrode 6 and the first electrode 5 is taken as the minimum distance.

[0057] Exemplarily, each second electrode 6 has the same shape, and the first portion 61 and the second portion 62 of each second electrode 6 have the same shape. That is, the shape of the second electrode 6 is an axisymmetric figure, for example, when the first electrode 5 is a circular electrode and the second electrode 6 is four symmetrical L-shaped electrodes evenly distributed around it, the distance between the first endpoint 601 and the first electrode 5 is equal to the distance between the second endpoint 602 and the first electrode 5, and the minimum distance between the second electrode 6 and the first electrode 5 is the distance between the first endpoint 601 and the tangent of the circle.

[0058] In the design of the back-illuminated photodiode 1, the shapes of the plurality of second electrodes 6 may be the same or different, and the plurality of second electrodes 6 may be evenly distributed around the first electrode 5 or unevenly distributed around the first electrode 5. The drawings of the present disclosure are described by taking the plurality of second electrodes 6 having the same shape and evenly distributed around the first electrode 5 as an example to facilitate a better understanding of the solution of the present disclosure.

[0059] In some embodiments, the line connecting the second endpoints 602 of the plurality of second electrodes 6 extends through the first electrode 5, and / or the line connecting the first endpoints 601 of the plurality of second electrodes 6 extends through the first electrode 5. For example, when the plurality of L-shaped second electrodes 6 are located in four directions of the circular first electrode 5, under the condition that the minimum distance between the second electrode 6 and the first electrode 5 is greater than or equal to 0.3 mm, the line connecting the second endpoints 602 may pass through the first electrode 5 in the vertical direction, and / or the line connecting the first endpoints 601 may pass through the first electrode 5 in the horizontal direction.

[0060] Figure 3 A schematic diagram of a first doped region in a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown.

[0061] According to an embodiment of the present disclosure, the orthographic projections of the plurality of second electrodes 6 on the substrate 2 are spaced apart from the orthographic projections of the first doping region 3 on the substrate 2. Specifically, when the orthographic projections of the second electrode 6 on the substrate 2 overlap with the orthographic projections of the first doping region 3 on the substrate 2, parasitic capacitance is easily generated, and the larger the parasitic capacitance, the larger the noise of the diode. In an embodiment of the present disclosure, the back-illuminated photodiode 1 can effectively reduce the generated parasitic capacitance by spacing the orthographic projections of the plurality of second electrodes 6 on the substrate 2 from the orthographic projections of the first doping region 3 on the substrate 2, thereby reducing the noise of the photodiode.

[0062] Because increasing the area of ​​the first doping region 3 (for example, the P+ doping region) is beneficial to the photoresponse and response speed of the photodiode, the present disclosure increases the area of ​​the first doping region 3 as much as possible without increasing the dark current, and does not introduce parasitic capacitance between the first doping region and the cathode electrode. Figure 3 The size and shape of the first doped region 3 shown improve the light response and response speed of the photodiode while not increasing the dark current and not introducing parasitic capacitance between the first doped region 3 and the second electrode 6 .

[0063] Figure 4 A schematic diagram of a first via hole in a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown.

[0064] According to an embodiment of the present disclosure, the back-illuminated photodiode 1 further includes a first via hole 7, and the first electrode 5 is electrically connected to the first doping region 3 through the first via hole 7, wherein the ratio of the area of ​​the first via hole 7 to the area of ​​the first electrode 5 is greater than or equal to 0.2.

[0065] Figure 4 The shape and area of ​​the first via hole 7 shown in the figure are only examples. The first via hole 7 can be of any geometric shape, and the number of the first via holes can also be multiple. The area ratio of the first via hole 7 to the first electrode 5 is greater than or equal to 0.2, which can achieve better contact between the metal electrode and the doped region, reduce the parasitic resistance between the metal electrode and the doped region, and improve the performance of the photodiode. The first via hole 7 is located between the first electrode 5 and the first doped region 3. Figure 6 The cross-sectional view of the back-illuminated photodiode shown in FIG. 1 shows a schematic diagram of the first electrode 5 being electrically connected to the first doped region 3 through the first via hole 7, and Figure 7 The cross-sectional view of the back-illuminated photodiode shown shows a schematic diagram of the electrical connection between the first electrode 5 and the first doping region 3 through a plurality of first via holes 7, which will not be elaborated in detail here.

[0066] In some embodiments, the back-illuminated photodiode further includes a plurality of second via holes 8, the positions of the second via holes 8 correspond to the positions of the second electrodes 6, each second electrode 6 is electrically connected to the second doping region 4 through the corresponding second via hole 8, wherein the area of ​​the first via hole 7 is larger than the area of ​​the second via hole 8. For example, Figure 1 The four second electrodes 5 shown are electrically connected to the second doping region 4 through four second via holes 8. The second via hole 8 is located between the second electrode 6 and the second doping region 4. Figure 6 and Figure 7 The cross-sectional view of the back-illuminated photodiode shown is a schematic diagram showing the electrical connection between the second electrode 6 and the second doping region 4 through the second via hole 8, which will not be described in detail here.

[0067] According to an embodiment of the present disclosure, the area of ​​the first via hole 7 is 5 times greater than the area of ​​the second via hole 8. In order to make the contact range between the first electrode 5 and the first doping region 3 larger and reduce the parasitic resistance between the first electrode 5 and the first doping region 3, the area of ​​the first via hole 7 can be set as large as possible, for example, the area of ​​the first via hole 7 is set to be 5 times greater than the area of ​​the second via hole 8.

[0068] Exemplarily, the orthographic projection of the second via hole 8 on the substrate 2 falls within the range of the orthographic projection of the second electrode 6 on the substrate 2. The present disclosure sets the orthographic projection of the second via hole 8 on the substrate 2 to fall within the range of the orthographic projection of the second electrode 6 on the substrate 2, so that the second electrode 6 is electrically connected to the second doping region 4 through the second via hole 8, so that the metal electrode is in better contact with the doping region.

[0069] For example, when the second electrode 6 is L-shaped, the second via hole 8 may also be L-shaped, and the second electrode 6 is in full contact with the second doping region 4 through the second via hole 8. For example, Figure 3 The schematic diagram of the back-illuminated photodiode shown in FIG. 1 shows an L-shaped second via hole 8. The L-shape of the second via hole 8 is only an example, and it can be any shape. The shape of the second via hole 8 can match the shape of the second electrode 6, be the same as the shape of the second electrode 6, or be a shape different from the shape of the second electrode 6. For example, the shape of the second electrode 6 is a rectangular shape, and the shape of the second via hole 8 is a circular shape.

[0070] In addition, since the orthographic projection of the second via hole 8 on the substrate 2 falls within the range of the orthographic projection of the second electrode 6 on the substrate 2 , the size of the second via hole 8 is smaller than or equal to the size of the second electrode 6 .

[0071] Exemplarily, the first electrode 5 is circular in shape, the first doping region 3 is rectangular in shape, and the first via hole 7 is rectangular in shape. Figure 1As shown, the boundary of the first electrode 5 partially overlaps with the boundary of the first doped region 3 , the vertex of the first via hole 7 is adjacent to the side of the first electrode 5 , and the area of ​​the first via hole 7 is greater than 0.2 times the area of ​​the first electrode 5 . Figure 1 The shapes and positions of the first electrode 5 , the first doping region 3 and the first via hole 7 make the areas of the first electrode 5 and the first via hole 7 relatively large.

[0072] Figure 5 A schematic diagram of a second doping region in a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown. Figure 6 A schematic diagram of a second doping region in a back-illuminated photodiode according to another embodiment of the present disclosure is schematically shown.

[0073] In some embodiments, the orthographic projection of the second doping region 4 on the substrate 2 is in the shape of a ring, or the orthographic projection of the second doping region 4 on the substrate 2 is the same as the shape of the second electrode 6, and the width of the second doping region 4 is less than or equal to the width of the second electrode 6. For example, Figure 5 As shown, the second doping region 4 is an annular doping region surrounding the first doping region 3, the second doping region 4 does not overlap with the first doping region 3, and the width of the second doping region 4 is smaller than the width of the second electrode 6. For another example, Figure 6 As shown, the second doping region 4 is an L-shaped doping region surrounding the first doping region 3 , the second doping region 4 does not overlap with the first doping region 3 , and the width of the second doping region 4 is smaller than the width of the second electrode 6 .

[0074] In the existing back-illuminated photodiode, the width of the second electrode (i.e., cathode electrode) is usually smaller than the width of the second doping region. During the ball planting process of the flip-chip process, due to the narrow width of the second electrode, there may be a gap between the planted gold ball and the corresponding contact of the substrate, resulting in a disconnection between the back-illuminated photodiode and the substrate, which may easily cause the second electrode to be suspended and disconnected during the flip-chip process. In the embodiment of the present disclosure, by setting the width of the second electrode 6 to be larger than the width of the second doping region 4, it is equivalent to increasing the width of the second electrode 6, avoiding the disconnection problem between the back-illuminated photodiode and the substrate, eliminating the ball planting process in the flip-chip process, and improving the overall yield of the area array detector.

[0075] Figure 7 Schematically shows a cross-sectional view of a back-illuminated photodiode according to an embodiment of the present disclosure, Figure 7 The cross-section shown is along Figure 1 A cross section taken along the diagonal line AA' in the schematic diagram.

[0076] According to an embodiment of the present disclosure, the back-illuminated photodiode 1 further includes an insulating layer 11, which covers the front surface of the substrate 2. The first via hole 7 is provided at a position of the insulating layer 11 corresponding to the first doping region 3, the second via hole 8 is provided at a position of the insulating layer 11 corresponding to the second doping region 4, the first electrode 5 is electrically connected to the first doping region 3 through the first via hole 7, and the second electrode 6 is electrically connected to the second doping region 4 through the second via hole 8. Figure 7 As shown, the first doping region 3 is spaced apart from the second doping region 4 , and the first electrode 5 is spaced apart from the second electrode 6 .

[0077] Figure 8 A cross-sectional view of a back-illuminated photodiode according to another embodiment of the present disclosure is schematically shown.

[0078] like Figure 8 As shown, the back-illuminated photodiode 1 further includes an insulating layer 11 , which covers the front side of the substrate 2 . There are two first via holes 7 at positions of the insulating layer 11 corresponding to the first doped region 3 , and the first electrode 5 is electrically connected to the first doped region 3 through the two first via holes 7 .

[0079] Figure 7 and Figure 8 The cross-sectional view of the back-illuminated photodiode shown is only an example to help those skilled in the art better understand the structure of the back-illuminated photodiode of the present disclosure. The illustration provided only illustrates the basic concept of the present disclosure in a schematic manner, and therefore only the structure related to the present disclosure is shown in the figure rather than being drawn according to the structure during actual implementation.

[0080] The disclosed solution solves the problems of high ball planting cost and possible short circuit or open circuit in the connection between the back-illuminated photodiode and the substrate during the flip-chip process of the back-illuminated photodiode. By reasonably setting the electrode shape of the photodiode and increasing the distance between the cathode electrode and the anode electrode of the photodiode, the ball planting step in the flip-chip process is omitted, and the packaging cost of the area array detector is reduced; increasing the size of the cathode electrode can reduce the risk of open circuit in the packaging process; increasing the distance between the cathode electrode and the anode electrode can effectively reduce the risk of short circuit between the cathode electrode and the anode electrode, and improve the packaging yield.

[0081] The scheme disclosed in the present invention increases the area of ​​the P+ doping region as much as possible without increasing the dark current of the back-illuminated photodiode and without introducing additional parasitic capacitance, thereby ensuring the light response, response speed and other indicators of the back-illuminated photodiode, thereby forming a back-illuminated photodiode with high sensitivity.

[0082] In addition, the solution disclosed in the present invention increases the via size of the back-illuminated photodiode, thereby enabling better contact between the metal electrode and the doped region, reducing the parasitic resistance between the metal electrode and the doped region, and improving the performance of the photodiode.

[0083] Another aspect of the present disclosure provides a method for manufacturing a back-illuminated photodiode.

[0084] Fig. 9 The flowchart of the method for manufacturing a back-illuminated photodiode according to an embodiment of the present disclosure is schematically shown. Fig. 9 As shown, the method may include operations S910 to S930.

[0085] In operation S910 , a substrate is provided, and a doping type of the substrate is a second doping type.

[0086] In operation S920, a first doping type is implanted into the front surface of the substrate to form a first doping region, and a second doping type is implanted to form a second doping region, wherein the first doping type is different from the second doping type, and the first doping region is spaced apart from the second doping region.

[0087] In operation S930, a first electrode electrically connected to the first doping region and a plurality of second electrodes electrically connected to the second doping region are disposed on the front side of the substrate, and the plurality of second electrodes are spaced apart along the first direction and the second direction, wherein the plurality of second electrodes are disposed to surround the first electrode and be spaced apart from the first electrode.

[0088] Another aspect of the present disclosure provides a detector.

[0089] Fig.10 A schematic diagram schematically shows an arrangement of back-illuminated photodiodes in a detector according to an embodiment of the present disclosure.

[0090] According to an embodiment of the present disclosure, a detector 12 is also provided, the detector 12 comprises a plurality of back-illuminated photodiodes 1 as described above, and the plurality of back-illuminated photodiodes 1 are arranged in an array. Fig.10 As shown, the detector 12 includes 20 evenly arranged back-illuminated photodiodes 1. The number and arrangement of the back-illuminated photodiodes 1 in the detector 12 can be set according to the needs of those skilled in the art and are not limited here.

[0091] Fig.11 A cross-sectional view schematically illustrates a back-illuminated photodiode connected to a substrate according to an embodiment of the present disclosure.

[0092] According to an embodiment of the present disclosure, the detector 12 further includes a conductive silver paste 9 and a substrate 10, and the first electrodes 5 and the second electrodes 6 of the plurality of back-illuminated photodiodes 1 are coupled to the substrate 10 through the conductive silver paste 9. Specifically, the electrodes can be led out using a dispensing process so as to be connected to the substrate, such as Fig.11As shown, the first electrode 5 and the second electrode 6 of the back-illuminated photodiode 1 are both connected to the substrate 10 through the conductive silver glue 9. Based on the structural setting of the back-illuminated photodiode disclosed in the present invention, the ball planting step in the flip-chip process can be omitted, and the photodiode electrode can be directly coupled to the printed circuit board substrate using the conductive silver glue, which saves packaging costs, avoids the risks of short circuit and open circuit in the packaging process, and improves the processing yield of the photodiode array.

[0093] The first electrode 5 and the second electrode 6 of the back-illuminated photodiode 1 implemented in the embodiment of the present disclosure are coupled to the substrate 10 through the conductive silver glue 9, realizing an easy-to-mount electrode design scheme, which can be used in CT and other X-ray non-destructive testing equipment in conjunction with a scintillator.

[0094] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0095] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure. The embodiments of the present disclosure will be described with reference to the accompanying drawings.

Claims

1. A back-illuminated photodiode, characterized in that: include: substrate; A first doped region, arranged on the front side of the substrate; a second doping region, disposed on the front surface of the substrate and spaced apart from the first doping region, wherein the second doping region and the first doping region have different doping types; a first electrode, electrically connected to the first doped region; as well as a plurality of second electrodes electrically connected to the second doping region, wherein the plurality of second electrodes are arranged at intervals along a first direction and a second direction, wherein the first direction is perpendicular to the second direction, The plurality of second electrodes are arranged to surround the first electrode and are spaced apart from the first electrode.

2. The back-illuminated photodiode according to claim 1, characterized in that: A straight line at which the minimum distance between the plurality of second electrodes and the first electrode is located is along a third direction, wherein the third direction intersects the first direction and the second direction.

3. The back-illuminated photodiode according to claim 2, characterized in that: The minimum distance between the plurality of second electrodes and the first electrode is greater than or equal to 0.3 mm.

4. The back-illuminated photodiode according to claim 2, characterized in that: The first electrode is in the shape of a continuous closed figure.

5. The back-illuminated photodiode according to claim 3, characterized in that: Each second electrode is L-shaped and includes a first portion extending along a first direction and a second portion extending along a second direction.

6. The back-illuminated photodiode according to claim 5, characterized in that: The second electrode comprises a first endpoint, a second endpoint and a corner point, the first endpoint is an endpoint of the first portion closest to the first electrode, the second endpoint is an endpoint of the second portion closest to the first electrode, and the corner point is located at the intersection of the first portion and the second portion and faces the first electrode; as well as The minimum distance is a minimum value of a distance between the first endpoint and the first electrode, a distance between the second endpoint and the first electrode, and a distance between the corner point and the first electrode.

7. The back-illuminated photodiode according to claim 5, characterized in that: The shapes of the second electrodes are the same, and the shapes of the first portion and the second portion of the second electrodes are the same.

8. The back-illuminated photodiode according to claim 1, characterized in that: The connecting line of the second endpoints of the plurality of second electrodes extends through the first electrode, and / or A line connecting the first endpoints of the plurality of second electrodes extends through the first electrode.

9. The back-illuminated photodiode according to claim 1, characterized in that: An orthographic projection of the plurality of second electrodes on the substrate is spaced apart from an orthographic projection of the first doped region on the substrate.

10. The back-illuminated photodiode according to claim 1, characterized in that: The back-illuminated photodiode further comprises: a first via hole, the first electrode being electrically connected to the first doped region through the first via hole, Wherein, the ratio of the area of ​​the first via hole to the area of ​​the first electrode is greater than or equal to 0.

2.

11. The back-illuminated photodiode according to claim 10, characterized in that: The back-illuminated photodiode further comprises: a plurality of second via holes, the positions of the second via holes corresponding to the positions of the second electrodes, each of the second electrodes being electrically connected to the second doped region through a corresponding second via hole, The area of ​​the first via hole is greater than the area of ​​the second via hole.

12. The back-illuminated photodiode according to claim 11, characterized in that: An area of ​​the first via hole is 5 times greater than an area of ​​the second via hole.

13. The back-illuminated photodiode according to claim 12, characterized in that: The orthographic projection of the second via hole on the substrate falls within the range of the orthographic projection of the second electrode on the substrate.

14. The back-illuminated photodiode according to claim 10, characterized in that: The first electrode is circular in shape, the first doping region is rectangular in shape, and the first via hole is rectangular in shape.

15. The back-illuminated photodiode according to claim 1, characterized in that: The orthographic projection of the second doping region on the substrate is in a ring shape, or the orthographic projection of the second doping region on the substrate is the same as the shape of the second electrode, and the width of the second doping region is less than or equal to the width of the second electrode.

16. A detector, characterized in that: The detector comprises a plurality of back-illuminated photodiodes as claimed in any one of claims 1 to 15, wherein the plurality of back-illuminated photodiodes are arranged in an array.

17. The detector according to claim 16, characterized in that The invention also includes a conductive silver paste and a substrate, wherein the first electrodes and the second electrodes of the plurality of back-illuminated photodiodes are coupled to the substrate through the conductive silver paste.

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