Image sensor

Abstract

The present invention provides an image sensor. The image sensor includes a substrate, a plurality of photoelectric conversion structures, a plurality of transmission regions, and a plurality of voltage regulating structures. The image sensor is in corresponding electrical contact with the proximal ends of each of the photoelectric conversion structures through the plurality of transmission regions provided, and the two proximal ends of adjacent photoelectric conversion structures are located on different sides, forming a plurality of built-in electric fields pointing to the transmission regions. Combining with the plurality of voltage regulating structures arranged between adjacent photoelectric conversion structures is conducive to improving the migration rate of photo-generated electrons.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device manufacturing, and particularly to an image sensor. Background Art

[0002] With the wide application of CMOS image sensors in fields such as mobile phones, monitoring, aerospace, etc., the pixel unit area of the photodiodes is getting larger and larger, resulting in an increasingly serious delay in the transfer of photo-generated electrons in the pixel to the floating diode area through the transfer gate, seriously affecting the imaging quality.

[0003] Therefore, it is necessary to develop a new type of image sensor to solve the above problems existing in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide an image sensor to facilitate the improvement of the migration rate of photo-generated electrons.

[0005] To achieve the above purpose, the image sensor of the present invention includes:

[0006] A substrate;

[0007] A plurality of photoelectric conversion structures disposed on the surface of the substrate, each photoelectric conversion structure including a distal end portion and a proximal end portion opposite to each other, the two proximal end portions of adjacent photoelectric conversion structures being located on different sides, and each photoelectric conversion structure having a built-in electric field;

[0008] A plurality of transmission regions disposed on the surface of the substrate and in corresponding electrical contact with the proximal end portion of each photoelectric conversion structure, so that the built-in electric field of each photoelectric conversion structure points away from the transmission region;

[0009] A plurality of voltage regulating structures respectively disposed between adjacent photoelectric conversion structures to regulate the electric potential of the plurality of photoelectric conversion structures.

[0010] The beneficial effect of the image sensor of the present invention is that: the image sensor forms a plurality of built-in electric fields pointing to the transmission region by disposing a plurality of transmission regions in corresponding electrical contact with the proximal end portion of each photoelectric conversion structure, and the two proximal end portions of adjacent photoelectric conversion structures being located on different sides, and in combination with a plurality of voltage regulating structures disposed between adjacent photoelectric conversion structures, which is beneficial to improving the migration rate of photo-generated electrons.

[0011] Preferably, each photoelectric conversion structure is composed of a doped semiconductor material, and the doping concentration of the photoelectric conversion structure increases along the direction pointing to the transmission region in corresponding electrical contact. The beneficial effect thereof is that: a plurality of built-in electric fields are formed to facilitate the acceleration of the migration of photo-generated electrons.

[0012] More preferably, each of the photoelectric conversion structures includes a photosensitive region disposed in the substrate and doped with donor impurities. The photosensitive region includes a photosensitive proximal end close to the correspondingly disposed transmission region and a photosensitive distal end far from the correspondingly disposed transmission region. The doping concentration of the photosensitive region increases in the direction from the photosensitive distal end to the photosensitive proximal end.

[0013] More preferably, each of the photoelectric conversion structures includes a pinning region disposed on the surface of the substrate and doped with acceptor impurities. The pinning region includes a pinning proximal end close to the correspondingly disposed transmission region and a pinning distal end far from the correspondingly disposed transmission region. The doping concentration of the pinning region increases in the direction from the pinning distal end to the pinning proximal end. The beneficial effect is that: the potential difference is increased in the regions of the plurality of photoelectric conversion structures to improve the migration rate of photo-generated electrons.

[0014] Preferably, the voltage regulating structure is inclined to any one of the adjacent photoelectric conversion structures. The beneficial effect is that: the potential difference of the built-in electric field of the photoelectric conversion structure is increased, which is beneficial to improving the migration rate of photo-generated electrons.

[0015] More preferably, one end of the voltage regulating structure is close to the proximal end of one of the adjacent photoelectric conversion structures, and the other end is close to the proximal end of the other adjacent photoelectric conversion structure.

[0016] More preferably, the voltage regulating structure is an equipotential structure.

[0017] More preferably, each of the voltage regulating structures is disposed on the substrate between the adjacent photoelectric conversion structures or in the substrate between the adjacent photoelectric conversion structures.

[0018] More preferably, the voltage regulating structure includes any one of a semiconductor structure doped with acceptor impurities, an intrinsic semiconductor structure, and a metal structure.

[0019] Preferably, the plurality of photoelectric conversion structures are arranged in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of an image sensor of the prior art;

[0021] Figure 2 is Figure 1 a top view of;

[0022] Figure 3 is a schematic structural diagram of an image sensor according to some embodiments of the present invention;

[0023] Figure 4 is the top view of Figure 3 ;

[0024] Figure 5 is Figure 4 the structural schematic diagram of the second photo - electric conversion structure shown in

[0025] Figure 6 is the structural schematic diagram of a photosensitive region of an embodiment of the present invention;

[0026] Figure 7 is the structural schematic diagram of a pinning region of an embodiment of the present invention. Detailed implementation manners

[0027] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present invention pertains. The words such as "including" used herein mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0028] Figure 1 is the structural schematic diagram of an image sensor of the prior art. Figure 2 is Figure 1 the top view of

[0029] Referring to Figure 1 and Figure 2 , Figure 1 in the prior - art image sensor (not labeled in the figure) shown in , a pixel unit 12 disposed on a substrate 11 is in electrical contact with a transfer tube 13 disposed on the substrate 11. The photo - generated electrons generated by the pixel unit 12 through photo - electric conversion are led out to the outside for amplification and processing by applying a high voltage using the transfer tube 13. When the area of the pixel unit 12 is relatively large, the end far from the transfer tube 13 will be affected by the distance problem, resulting in a transfer delay, which will cause image delay and smear.

[0030] To solve the above - mentioned problems existing in the prior art, an embodiment of the present invention provides an image sensor to facilitate improving and adjusting the migration rate of photo - generated electrons.

[0031] Figure 3 is the structural schematic diagram of an image sensor according to some embodiments of the present invention.Figure 4 is Figure 3 the top view of

[0032] Referring to Figure 3 , Figure 3 the image sensor shown in

[0033] Referring to Figure 3 and Figure 4 , the photoelectric conversion structure 31 includes a plurality of photoelectric conversion structures including a first photoelectric conversion structure 41 and a second photoelectric conversion structure 42. The first side transmission region 32 includes a plurality of transmission regions located on one side of each of the photoelectric conversion structures including a first transmission region 43, and the second side transmission region 33 includes a plurality of transmission regions located on the other side of each of the photoelectric conversion structures including a second transmission region 44.

[0034] In some embodiments, the substrate 11 is a semiconductor substrate.

[0035] In some specific embodiments, the constituent material of the semiconductor substrate is at least one of silicon, germanium, silicon-germanium compound, and silicon-carbon compound.

[0036] In some embodiments, the substrate 11 is a P-type semiconductor substrate.

[0037] In some embodiments, the photoelectric conversion structure generates photoelectrons in response to the incidence of light. Each of the photoelectric conversion structures has a built-in electric field to migrate the generated photoelectrons within the photoelectric conversion structure.

[0038] In some embodiments, adjacent photoelectric conversion structures are separated by an exposed portion of the substrate. Referring to Figure 4 , the region between adjacent first photoelectric conversion structure 41 and second photoelectric conversion structure 42 is an exposed portion of the substrate 11.

[0039] In some embodiments, the plurality of photoelectric conversion structures are arranged in parallel.

[0040] In some embodiments, the transmission region includes a gate dielectric layer provided on the top surface of the substrate 11 and a gate provided on the top surface of the gate dielectric layer. Applying a voltage to the gate opens the transmission region to promote the outward migration of photoelectrons within the photoelectric conversion structure.

[0041] In some embodiments, the gate dielectric layer is a gate oxide layer. In some specific embodiments, the constituent material of the gate oxide layer is silicon dioxide or silicon oxynitride.

[0042] In some embodiments, each of the photoelectric conversion structures includes a distal end portion and a proximal end portion that are opposite to each other. Referring to Figure 4 , taking the first photoelectric conversion structure 41 as an example: the distal end portion of the first photoelectric conversion structure 41 is the distal end portion 411 of the first conversion region, and the proximal end portion is the proximal end portion 412 of the first conversion region; the distal end portion 411 of the first conversion region is opposite to the proximal end portion 412 of the first conversion region.

[0043] In some embodiments, the two proximal end portions of adjacent photoelectric conversion structures are located on different sides. Referring to Figure 4 , the distal end portion of the second photoelectric conversion structure 42 is the distal end portion 421 of the second conversion region, and the proximal end portion is the proximal end portion 422 of the second conversion region that is opposite to the distal end portion 421 of the second conversion region. The proximal end portion 412 of the first conversion region and the proximal end portion 422 of the second conversion region are located on different sides.

[0044] In some embodiments, each of the transmission regions is in electrical contact with the proximal end portion of each photoelectric conversion structure. Referring to Figure 4 , taking the first photoelectric conversion structure 41 and the second photoelectric conversion structure 42 as an example: the first transmission region 43 is in electrical contact with the proximal end portion of the first photoelectric conversion structure 41, that is, the proximal end portion 412 of the first conversion region; the second transmission region 44 is in electrical contact with the proximal end portion of the second photoelectric conversion structure 42, that is, the proximal end portion 422 of the second conversion region.

[0045] In some embodiments, the built-in electric field direction of each photoelectric conversion structure points in a direction away from the transmission region. Referring to Figure 4 , the built-in electric field direction of the first photoelectric conversion structure 41 points in a direction away from the first transmission region 43; the built-in electric field direction of the second photoelectric conversion structure 42 points in a direction away from the second transmission region 44.

[0046] In some embodiments, the image sensor further includes a plurality of voltage regulating structures, and each voltage regulating structure is disposed on the substrate between adjacent photoelectric conversion structures or in the substrate between adjacent photoelectric conversion structures. Referring to Figure 4 , a plurality of voltage regulating structures including the first voltage regulating structure 45 are disposed on the top surface of the substrate 11, and the first voltage regulating structure 45 is disposed on the substrate 11 between the first photoelectric conversion structure 41 and the second photoelectric conversion structure 42 for further improving the migration rate of photo-generated electrons.

[0047] In some embodiments, referring to Figure 4, taking the first voltage regulating structure 45 as an example, one end of the first voltage regulating structure 45 is close to the proximal end 412 of the first conversion region and extends toward the proximal end 422 of the second conversion region until the other end is close to the proximal end 422 of the second conversion region.

[0048] In some embodiments, the voltage regulating structure is an equipotential structure, which is beneficial to the potential difference in the plurality of photoelectric conversion structures and further accelerates the migration rate of photo-generated electrons.

[0049] In some embodiments, the voltage regulating structure is a semiconductor structure doped with acceptor impurities. In some embodiments, the doping concentration of acceptor impurities in the voltage regulating structure is uniform.

[0050] In some embodiments, the voltage regulating structure is an intrinsic semiconductor structure.

[0051] In some embodiments, the voltage regulating structure is a metal structure.

[0052] In some embodiments, the shape and size of the metal structure meet the requirements of the channel interconnection level.

[0053] In some embodiments, the metal structure is disposed in the substrate 11 and the top surface is exposed.

[0054] In some embodiments, the metal structure is disposed on the surface of the substrate 11.

[0055] Figure 5 For Figure 4 the structural schematic diagram of the second photoelectric conversion structure shown.

[0056] In some embodiments, each of the photoelectric conversion structures is composed of a doped semiconductor material. Referring to Figure 5 , taking the second photoelectric conversion structure 42 as an example, the second photoelectric conversion structure 42 includes a photosensitive region 51 and a pinning region 52.

[0057] In some embodiments, the photosensitive region 51 is doped with donor impurities and becomes an N-type doped region. The pinning region 52 is doped with acceptor impurities and becomes a P-type doped region. The photosensitive region 51 and the pinning region 52 are in contact to form a PN junction, thereby promoting the migration of photo-generated electrons in the photoelectric conversion structure.

[0058] In some specific embodiments, the donor impurity is a pentavalent element. For example, it is any one of phosphorus, antimony, and arsenic.

[0059] In some specific embodiments, the acceptor impurity is a trivalent element. For example, the trivalent element is any one of boron, indium, gallium, or aluminum.

[0060] Figure 6Schematic diagram of a photosensitive region according to an embodiment of the present invention. Figure 7 Schematic diagram of a pinning region according to an embodiment of the present invention.

[0061] In some embodiments, the doping concentration of the photoelectric conversion structure increases in the direction pointing to the corresponding transmission region of the electrical contact to form a plurality of built-in electric fields to accelerate the migration rate of photo-generated electrons.

[0062] In some specific embodiments, referring to Figures 4 to 6 , taking the second photoelectric conversion structure 42 as an example, the photosensitive region 51 includes a photosensitive proximal end portion 62 close to the corresponding second transmission region 44, and a photosensitive distal end portion 61 far from the corresponding second transmission region 44. The doping concentration of the photosensitive region 51 increases in the direction from the photosensitive distal end portion 61 to the photosensitive proximal end portion 62 to strengthen the built-in electric field of the second photoelectric conversion structure 42 in the direction towards the second transmission region 44.

[0063] In some specific embodiments, referring to Figures 4 to 6 , taking the second photoelectric conversion structure 42 as an example, the pinning region 52 includes a pinning proximal end portion 72 close to the corresponding second transmission region 44, and a pinning distal end portion 71 far from the corresponding second transmission region 44. The doping concentration of the pinning region 52 increases in the direction from the pinning distal end portion 71 to the pinning proximal end portion 72 to strengthen the built-in electric field of the second photoelectric conversion structure 42 in the direction towards the second transmission region 44.

[0064] The embodiment of the present invention also provides a method for manufacturing the image sensor, including the following steps:

[0065] S1: Provide a substrate;

[0066] S2: Form a plurality of the transmission regions, a plurality of the photoelectric conversion structures having built-in electric fields, and the plurality of voltage regulating structures on the substrate, such that the two proximal end portions of adjacent photoelectric conversion structures are located on different sides, each transmission region is electrically contacted with the proximal end portion of each photoelectric conversion structure, and the voltage regulating structure is disposed between adjacent photoelectric conversion structures.

[0067] In the step S2 of some embodiments, the step of disposing a plurality of the transmission regions and a plurality of the photoelectric conversion structures having built-in electric fields on the substrate includes:

[0068] S21: Form a plurality of transmission regions on the substrate;

[0069] S22: After defining a plurality of processing regions on the surface of the substrate adjacent to the transmission region using a photoresist material, a doping impurity is implanted into the plurality of processing regions using an ion implantation process to form a plurality of the optoelectronic conversion structures in electrical contact with the transmission region, and then the photoresist material is removed.

[0070] In the step S21 of some embodiments, the step of forming a plurality of transmission regions on the substrate includes:

[0071] S211: After depositing an initial gate dielectric layer on the surface of the substrate using a gate dielectric material, the initial gate dielectric layer is patterned to form a plurality of the gate dielectric layers;

[0072] S212: After depositing an initial gate layer on the top of the substrate using a metal material, the initial gate layer is patterned to form a plurality of gate electrodes respectively covering a plurality of the gate dielectric layers, and the gate dielectric layers and the gate electrodes constitute the transmission region.

[0073] In the step S22 of some embodiments, first, a donor impurity is implanted into the processing region using an ion implantation process to form a photosensitive region, and then an acceptor impurity is implanted into the processing region using an ion implantation process to form a pinning region in contact with the photosensitive region.

[0074] In the step S22 of some embodiments, taking the formation of the photosensitive region as an example, during the process of the ion implantation process, by controlling the implantation angle and implantation energy, a concentration gradient is formed in the photosensitive region.

[0075] In some embodiments, the voltage regulating structure is a semiconductor structure doped with acceptor impurities and having a uniform doping concentration. Specifically, the substrate provided in the step S1 is an intrinsic semiconductor substrate. In the step S2, after a plurality of the transmission regions and a plurality of the optoelectronic conversion structures are fabricated, a processing region located between adjacent optoelectronic conversion structures is defined using a photoresist; an acceptor impurity is implanted into the processing region between adjacent optoelectronic conversion structures using an ion implantation process, and the implantation angle and energy are controlled so that the doping concentration in the formed voltage regulating structure is uniform.

[0076] In some embodiments, the voltage regulating structure is an intrinsic semiconductor structure. Specifically, the substrate provided in the step S1 is an intrinsic semiconductor substrate. In the step S2, after using a photoresist to block the regions on the surface of the substrate for forming a plurality of the voltage regulating structures, the substrate is subjected to ion implantation to form a P-type substrate having a plurality of intrinsic regions, and then a plurality of the transmission regions and a plurality of the optoelectronic conversion structures are fabricated.

[0077] In some embodiments, the voltage regulating structure is a metal structure disposed within the substrate and having its top surface exposed. In step S2, during the process of fabricating a plurality of the transmission regions, after step S212 is completed:

[0078] Use a mask to shield the protected regions to expose the regions to be etched for subsequently forming a plurality of the voltage regulating structures, and then etch the regions to be etched to form a plurality of trench structures;

[0079] Deposit a metal material to fill the plurality of trench structures and cover the surface of the regions to be etched;

[0080] Remove the metal material on the surface of the regions to be etched to form a plurality of the metal structures.

[0081] In some embodiments, the voltage regulating structure is a metal structure disposed on the surface of the substrate. In step S2, during the process of fabricating a plurality of the transmission regions, after step S212 is completed:

[0082] Use a mask to shield the protected regions to expose the regions to be etched for subsequently forming a plurality of the voltage regulating structures;

[0083] Deposit a metal material to cover the surface of the regions to be etched, and then remove a part of the metal material to form a plurality of the metal structures disposed on the surface of the substrate.

[0084] In some embodiments, the voltage regulating structure is a metal structure disposed on the surface of the substrate. In step S2, all the gates and all the voltage regulating structures are formed synchronously. Specifically, after step S211 is completed:

[0085] Use a mask to shield the protected regions to expose the plurality of gate dielectric layers and the regions to be etched for subsequently forming a plurality of the voltage regulating structures;

[0086] Deposit a metal material to cover the surface of the regions to be etched and the surface of the plurality of gate dielectric layers, and then remove a part of the metal material to form a plurality of the metal structures disposed on the surface of the substrate and gates respectively covering the top surfaces of each of the gate dielectric layers.

[0087] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes all fall within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. An image sensor, characterized in that, Comprising: A substrate; A plurality of optoelectronic conversion structures disposed on the surface of the substrate, each optoelectronic conversion structure including a distal end portion and a proximal end portion opposite to each other, the two proximal end portions of adjacent optoelectronic conversion structures being located on different sides, and each optoelectronic conversion structure having a built-in electric field; the plurality of optoelectronic conversion structures are arranged parallel to each other; the optoelectronic conversion structures extend in a first direction, and the plurality of optoelectronic conversion structures are arranged in sequence in a second direction; the first direction is perpendicular to the second direction; A plurality of transmission regions disposed on the surface of the substrate and in electrical contact with the proximal end portion of each optoelectronic conversion structure, so that the built-in electric field of each optoelectronic conversion structure points away from the transmission region; A plurality of voltage regulating structures respectively disposed between adjacent optoelectronic conversion structures to regulate the potential difference between the plurality of optoelectronic conversion structures; the voltage regulating structure is inclined to any one of the adjacent optoelectronic conversion structures; one end of the voltage regulating structure is close to the proximal end portion of one of the adjacent optoelectronic conversion structures, and the other end is close to the proximal end portion of the other adjacent optoelectronic conversion structure.

2. The image sensor according to claim 1, wherein Each optoelectronic conversion structure is composed of a doped semiconductor material, and the doping concentration of the optoelectronic conversion structure increases in the direction pointing to the transmission region corresponding to the electrical contact.

3. The image sensor according to claim 2, characterized in that, Each optoelectronic conversion structure includes a photosensitive region doped with donor impurities and disposed in the substrate, the photosensitive region including a photosensitive proximal end portion close to the correspondingly disposed transmission region and a photosensitive distal end portion far from the correspondingly disposed transmission region, and the doping concentration of the photosensitive region increases in the direction from the photosensitive distal end portion to the photosensitive proximal end portion.

4. The image sensor according to claim 2, wherein Each optoelectronic conversion structure includes a pinning region doped with acceptor impurities and disposed on the surface of the substrate, the pinning region including a pinning proximal end portion close to the correspondingly disposed transmission region and a pinning distal end portion far from the correspondingly disposed transmission region, and the doping concentration of the pinning region increases in the direction from the pinning distal end portion to the pinning proximal end portion.

5. The image sensor according to claim 1, wherein Each voltage regulating structure is disposed on the substrate between adjacent optoelectronic conversion structures or in the substrate between adjacent optoelectronic conversion structures.

6. The image sensor according to claim 1, characterized in that, The voltage regulating structure is an equipotential structure.

7. The image sensor according to claim 1, characterized in that, The voltage regulating structure includes any one of a semiconductor structure doped with acceptor impurities, an intrinsic semiconductor structure, and a metal structure.

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