SPAD structure and manufacturing method for the same

Abstract

To provide a SPAD structure and a manufacturing method for the same.SOLUTION: The present invention provides a SPAD structure and a manufacturing method for the same, in which guide walls are formed on the sides of a first impurity-doped region and a second impurity-doped region, so that photo-generated charges are guided to diffuse into an avalanche region (A) located on the PN junction region side between the first and second impurity-doped regions, thereby improving photon detection efficiency (PDE).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a SPAD structure and a method for manufacturing the same, and more particularly to a SPAD structure and a method for manufacturing the same, in which guide walls are formed on sides of a first impurity-doped region and a second impurity-doped region, and photo-generated charges are guided to diffuse to an avalanche region (A) on a PN junction region between the first impurity-doped region and the second impurity-doped region, thereby improving photon detection efficiency (PDE). [Background technology]

[0002] Single-photon avalanche diodes (SPADs) are commonly used as pixel photoelectric conversion elements in imaging devices. These SPADs have a PN junction region for detecting incident radiation and operate in Geiger mode, which is a mode in which they operate at a voltage much higher than the breakdown voltage of the single-photon avalanche diode, also known as the avalanche voltage. Because a voltage exceeding the breakdown voltage is applied to the SPAD, an electron avalanche occurs due to carriers generated by photoelectric conversion, causing the SPAD to enter a breakdown state. This results in carrier amplification due to photoelectric conversion, improving the sensitivity of the imaging device.

[0003] FIG. 1 is a cross-sectional view illustrating a conventional SPAD structure.

[0004] Referring to FIG. 1 , a conventional SPAD structure 9 includes a substrate 910 having a front surface 911 and a back surface 913. A P-type region 930 may be formed within the substrate 910, stacked on an N-type region 950. A PN junction region is formed by the P-type region 930 and the N-type region 950. When a reverse voltage sufficient to cause avalanche breakdown is applied to the PN junction region of the structure 9, electrons generated by a single photon reach the avalanche region A and generate a large current pulse, thereby enabling single photons to be measured. Generally, in the SPAD structure 9, photon detection efficiency (PDE) is calculated based on the number of current pulses generated by photogenerated electrons relative to the number of photons reaching the pixel. Therefore, to achieve a high PDE, photogenerated electrons must reach the avalanche region A as much as possible.

[0005] The existing SPAD structure 9 described above has a problem in that a significant portion of photo-generated electrons diffuse to the side surfaces of the PN junction region rather than the avalanche region A, and do not contribute to photon detection. In particular, electrons generated at the sides of the P-type region 930 and the N-type region 950 do not pass through the avalanche region A but instead flow into the cathode via the side surfaces of the PN junction region PN, which is the shortest distance.

[0006] To solve the above-mentioned problems, the inventors of the present invention present a novel SPAD pixel structure and fabrication method with an improved structure, which will be described in detail below. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 10-2019-0049598 "SPAD Image Sensor and Related Manufacturing Method" Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to provide a SPAD structure and a manufacturing method thereof that improves photon detection efficiency (PDE) by forming guide walls on the sides of a first impurity-doped region and a second impurity-doped region, thereby guiding photo-generated charges to diffuse into an avalanche region on the PN junction region between the first impurity-doped region and the second impurity-doped region.

[0009] Another object of the present invention is to provide a SPAD structure and a manufacturing method thereof that prevents a gap from being formed between the first region and the second region, thereby preventing charges photogenerated on the side of the substrate from diffusing to the side of the PN junction region.

[0010] Another object of the present invention is to provide a SPAD structure and a manufacturing method thereof in which the second region is doped with impurities at a lower concentration than the first region, thereby allowing photogenerated charges on the side of the substrate to diffuse to the avalanche region.

[0011] Another object of the present invention is to provide a SPAD structure and a manufacturing method thereof that reduces the dark count rate by forming a guard ring between the first region and the first impurity-doped region and the second impurity-doped region.

[0012] Another object of the present invention is to provide a SPAD structure and a manufacturing method thereof in which the second region is formed to contact the second impurity-doped region, thereby allowing photo-generated charges to diffuse into the avalanche region.

[0013] Another object of the present invention is to provide a SPAD structure and a manufacturing method thereof, in which a second region, which is a first conductivity type impurity doped region, and a second impurity doped region, which is a first conductivity type impurity doped region with a lower concentration than the second region, are formed so as to overlap each other, thereby preventing misalignment between the second impurity doped region and the first impurity doped region. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention can be realized by an embodiment having the following configuration.

[0015] According to one embodiment of the present invention, a SPAD structure according to the present invention is characterized by including a substrate having a front surface and a back surface, a first impurity-doped region in the substrate on the front side of the substrate, a second impurity-doped region on the first impurity-doped region in the substrate, and a guide wall surrounding sidewalls of the first impurity-doped region and the second impurity-doped region in the substrate.

[0016] According to another embodiment of the present invention, the guide wall of the SPAD structure of the present invention is a first conductive type impurity doped region, and the first impurity doped region is a second conductive type impurity doped region.

[0017] According to another embodiment of the present invention, the guide wall of the SPAD structure according to the present invention is characterized in that it comprises a first region extending upward from the front side to the back side of the substrate.

[0018] According to another embodiment of the present invention, the first region of the SPAD structure according to the present invention is characterized in that its upper surface is located higher in the substrate than the upper surface of the second impurity-doped region.

[0019] According to another embodiment of the present invention, the guide wall of the SPAD structure of the present invention further includes a second region extending onto an upper surface of a second impurity-doped region adjacent to the first region.

[0020] According to another embodiment of the present invention, the second region of the SPAD structure according to the present invention is characterized in that it is in contact with the second impurity-doped region.

[0021] According to another embodiment of the present invention, the second region of the SPAD structure of the present invention is formed to have an opening that at least partially exposes an upper surface of the second impurity-doped region.

[0022] According to another embodiment of the present invention, the second region of the SPAD structure according to the present invention is a region doped with impurities of the first conductivity type at a lower concentration than the first region.

[0023] According to another embodiment of the present invention, the SPAD structure according to the present invention is characterized in that it further comprises a first contact region in the first impurity-doped region on the front side of the substrate, and a second contact region spaced apart from the first contact region on the front side of the substrate.

[0024] According to another embodiment of the present invention, the SPAD structure of the present invention further includes a guard ring between the guide wall and the adjacent first and second impurity-doped regions.

[0025] According to another embodiment of the present invention, the guard ring of the SPAD structure of the present invention is a region doped with impurities of the first conductivity type at a lower concentration than the first and second regions.

[0026] According to another embodiment of the present invention, a SPAD structure according to the present invention includes a substrate having a front surface and a back surface, an isolation region on a unit pixel boundary side, a first impurity-doped region in the substrate on the front surface side of the substrate, a second impurity-doped region on the first impurity-doped region in the substrate, a first contact region in the first impurity-doped region, a second contact region between the front surface of the substrate and the isolation region, and a guide wall surrounding sidewalls of the first impurity-doped region and the second impurity-doped region in the substrate, wherein the guide wall includes a first region on the second contact region and a second region extending to contact a sidewall of an adjacent second impurity-doped region on the first region.

[0027] According to another embodiment of the present invention, the first region of the SPAD structure of the present invention is characterized in that it is an impurity-doped region of a first conductivity type that is lightly doped compared to the second contact region and is heavily doped compared to the second region.

[0028] According to another embodiment of the present invention, the SPAD structure of the present invention is characterized in that the first impurity doping concentration is gradually reduced in the second contact region, the first region, and the second region.

[0029] According to another embodiment of the present invention, the second region of the SPAD structure according to the present invention is characterized in that its top surface is located higher than the top surface of the second impurity-doped region with which it is in contact.

[0030] According to another embodiment of the present invention, the first region of the SPAD structure according to the present invention is spaced apart from a sidewall of an adjacent first impurity-doped region.

[0031] According to another embodiment of the present invention, the guide wall of the SPAD structure according to the present invention is an impurity doped region of an opposite type to that of the first impurity doped region.

[0032] According to another embodiment of the present invention, a SPAD structure according to the present invention includes a substrate having a front surface and a back surface; a first impurity-doped region in the substrate on the front surface side of the substrate; a guide wall including a first region in the substrate separated from the first impurity-doped region and a second region crossing a unit pixel on the first region; and a second impurity-doped region in the second region, wherein the second impurity-doped region is a first conductivity type impurity-doped region having a lower concentration than the second region.

[0033] According to another embodiment of the present invention, the second impurity-doped region of the SPAD structure of the present invention is formed by implanting impurities of a second conductivity type into the second region after the formation of the second region. [Effects of the Invention]

[0034] The present invention has the following effects due to the above-described configuration.

[0035] The present invention has an effect of improving photon detection efficiency (PDE) by forming guide walls on the sides of the first impurity doped region and the second impurity doped region, and inducing photo-generated charges to diffuse into an avalanche region on the PN junction region between the first impurity doped region and the second impurity doped region.

[0036] Furthermore, the present invention has the effect of preventing the formation of a gap between the first region and the second region, thereby preventing charges photogenerated on the side of the substrate from diffusing to the side of the PN junction region.

[0037] The present invention also has the advantage that the second region is lightly doped with impurities compared to the first region, thereby allowing charge photogenerated on the side of the substrate to diffuse into the avalanche region.

[0038] Furthermore, the present invention has the effect of reducing the dark count rate by forming guard rings between the first region and the first impurity-doped region and between the first region and the second impurity-doped region.

[0039] Furthermore, the present invention provides an effect that the second region is formed to contact the second impurity-doped region, thereby facilitating the diffusion of photo-generated charges into the avalanche region.

[0040] In addition, the present invention has the effect of preventing misalignment between the second impurity doped region and the first impurity doped region by forming the second region, which is a first conductivity type impurity doped region, and the second impurity doped region, which is a first conductivity type impurity doped region with a lower concentration than the second region, so that they overlap.

[0041] On the other hand, even if the effects are not explicitly mentioned herein, the effects and provisional effects described in the following specification that are expected by the technical features of the present invention shall be treated as described in the specification of the present invention. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is a cross-sectional view illustrating a conventional SPAD pixel structure. [Figure 2] 1 is a cross-sectional view illustrating a SPAD structure according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view illustrating a SPAD structure according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view illustrating a SPAD structure according to a third embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view illustrating a SPAD structure according to a fourth embodiment of the present invention. [Figure 6] 1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. [Figure 7]1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. [Figure 8] 1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. [Figure 9] 1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. [Figure 10] 1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. [Figure 11] 1A to 1C are cross-sectional views illustrating a method for manufacturing a SPAD structure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to these embodiments, but should be construed based on the matters described in the claims. Furthermore, the present embodiments are provided merely as references to more completely explain the present invention to those skilled in the art.

[0044] As used herein, the singular forms "a," "an," and "the" can include the plural forms unless the context clearly dictates otherwise. Also, as used herein, "comprise" and / or "comprising" specify the presence of a stated shape, number, step, operation, member, element, and / or group thereof, but do not exclude the presence or addition of one or more other shapes, numbers, operations, members, elements, and / or groups.

[0045] Hereinafter, when a component (or layer) is described as being disposed on another component (or layer), it should be noted that the component may be disposed directly on the other component, or there may be another component or layer interposed between the components. Also, when a component is described as being disposed directly on another component, there is no other component located between the components. Furthermore, being located "above," "upper," "lower," "upper side," "below," "one side," or "side" of a component refers to a relative positional relationship.

[0046] Furthermore, terms such as first, second, etc. may be used to describe various items such as various elements, regions, and / or portions, but the second configuration does not necessarily presuppose the first configuration.

[0047] Furthermore, the conductivity type or doping region of a component may be defined as "P-type" or "N-type" depending on the predominant carrier characteristics, but this is for convenience of explanation and the technical concept of the present invention is not limited to the illustrated examples. For example, hereinafter, "P-type" or "N-type" will be used as the more general terms "first conductivity type" or "second conductivity type." Hereinafter, the first conductivity type may mean P-type and the second conductivity type may mean N-type, respectively, and conversely, the first conductivity type may mean N-type and the second conductivity type may mean P-type, respectively.

[0048] Also, the terms "high concentration" and "low concentration" used to describe the doping concentration of an impurity region should be understood to refer to the relative doping concentration of one component relative to another.

[0049] Hereinafter, a SPAD (Single Photon Avalanche Diode) structure 1 according to the present invention will be described in detail with reference to the accompanying drawings. The SPAD structure 1 according to the present invention is preferably a SPAD structure in a back-illuminated image sensor, but the scope of the present invention is not limited thereto.

[0050] The present invention relates to a SPAD structure, and more particularly to a SPAD structure that improves photon detection efficiency (PDE) by forming guide walls on the sides of a first impurity-doped region and a second impurity-doped region to guide photo-generated charges to diffuse into an avalanche region (A) on a PN junction region between the first impurity-doped region and the second impurity-doped region.

[0051] FIG. 2 is a cross-sectional view illustrating the SPAD structure according to the first embodiment of the present invention.

[0052] First, a SPAD structure 1 according to a first embodiment of the present invention will be described in detail.

[0053] 2, in the structure 1 according to the first embodiment of the present invention, a substrate 110 is formed having a front surface 111 and a back surface 113. The substrate 110 is a lightly doped region of a first conductivity type impurity and can be formed by epitaxial growth.

[0054] A first impurity-doped region 120 may be formed on the front surface 111 of the substrate 110. The first impurity-doped region 120 may be a second conductivity type lightly doped impurity region formed on the surface side of the substrate 110. The first impurity-doped region 120 forms a PN junction region with the second impurity-doped region 130 above it, and an avalanche region A, which is an avalanche amplification region, may be formed between the two regions 120 and 130. The term "avalanche region (A)" refers to a region of a high electric field in the depletion region (A1, see FIG. 1), and may be formed on the interface between the first impurity-doped region 120 and the second impurity-doped region 130.

[0055] Furthermore, a first contact region 121 may be formed within the first impurity-doped region 120. That is, the first contact region 121 may be formed to be surrounded by the first impurity-doped region 120. The first contact region 121 is a second conductive type impurity-doped region, and preferably has a higher impurity concentration than the first impurity-doped region 120. The first contact region 121 may be electrically or physically connected to a first metal contact region 181 on the front surface 111 of the substrate 110. The first contact region 121 may be formed on the surface side of the front surface 111 of the substrate 110, but the scope of the present invention is not limited thereto. The first contact region 121 may be electrically connected to the cathode electrodes 181, 185.

[0056] A second impurity-doped region 130 may be formed on the first impurity-doped region 120 in the substrate 110. A PN junction region may be formed by the second impurity-doped region 130 and the first impurity-doped region 120. The second impurity-doped region 130 is a first conductivity type impurity-doped region, and is preferably doped with impurities at a higher concentration than the substrate 110 and at a lower concentration than the guide wall 160 described below.

[0057] The second contact region 140 may be formed on the front surface 111 of the substrate 110, spaced apart from the first impurity-doped region 120. The second contact region 140 may be formed spaced apart from the first impurity-doped region 120 and surrounding the sides of the first impurity-doped region 120 at a predetermined height. That is, the second contact region 140 may be formed in a disk shape, for example, but the scope of the present invention is not limited thereto. In the cross-sectional view shown, the second contact region 140 may be formed on the left and right sides of the first contact region 121, spaced apart from the first contact region 120. The second contact region 140 is a first-conductivity-type impurity-doped region, and is preferably doped with a higher concentration of first-conductivity-type impurities than the guide wall 160, which will be described later. The second contact region 140 may be electrically or physically connected to a second metal contact region 183 on the front surface 111 of the substrate 110. The second contact region 140 can be electrically connected to the cathode electrodes 183 and 187 .

[0058] Next, an isolation region 150 may be formed on the boundary side of the unit pixel. For example, the isolation region 150 may extend vertically from the rear surface 113 of the substrate 110 to the second contact region 140 or to the front surface 111. The isolation region 150 may be, for example, a first conductivity type impurity-doped region.

[0059] In addition, a guide wall 160 having a sidewall structure may be formed in the substrate 110, spaced apart from the sidewalls of the first impurity-doped region 120 and the second impurity-doped region 130. The guide wall 160 is a first conductive type impurity-doped region that prevents charges from diffusing to the sides of the PN junction region between the first impurity-doped region 120 and the second impurity-doped region 130 and guides the charge migration to the avalanche region A. In this case, the guide wall 160 should be doped with impurities of the opposite type to that of the first impurity-doped region 120. The guide wall 160 may include a first region 161 and a second region 163.

[0060] The first region 161 is an impurity-doped region that extends to a predetermined depth from the front surface 111 toward the back surface 113 of the substrate 110. Preferably, the first region 161 is doped with the first conductivity type impurity at a higher concentration than the second impurity-doped region 130 and at a lower concentration than the second contact region 140.

[0061] With this configuration, charges generated between the first region 161 and the isolation region 150 can easily move to the second region 163, which will be described later. The top surface of the first region 161 may extend to a position higher than the top surface of the second impurity-doped region 130 (or to a position adjacent to the back surface 113 of the substrate 110), or may be formed at substantially the same height. The first region 161 may be formed in a ring shape surrounding the sidewalls of the first impurity-doped region 120 and the second impurity-doped region 130, but the scope of the present invention is not limited thereto. In this case, the first region 161 is preferably formed so as to be laterally spaced apart from the adjacent first impurity-doped region 120 and second impurity-doped region 130.

[0062] The second region 163 extends a predetermined length from above the first region 161 in the substrate 110 inward (or toward the upper surface of the second impurity-doped region 130). One side of the bottom surface of the second region 163 may contact the upper side of the second impurity-doped region 130 or may be spaced apart by a predetermined distance, with the former being preferred. The second region 163 is preferably formed, for example, in a ring shape, so that the upper surface of the second impurity-doped region 130 has an opening O that opens into the substrate 110. The opening O can guide the diffusion of charges to the avalanche region A.

[0063] In addition, the second region 163 is preferably a region doped with impurities of the first conductivity type at a lower concentration than the first region 161. Therefore, charges generated between the guide wall 160 and the adjacent isolation region 150 can be induced to easily move toward the opening O. More specifically, it is preferable that the doping concentration of the first conductivity type impurities gradually decrease from the second impurity doped region 130 to the first region 161 and the second region 163. Alternatively, the first region 161 and the second region 163 may have substantially the same doping concentration of the first impurity. In addition, it is preferable that the second region 163 and the adjacent first region 161 are physically connected to each other, but the scope of the present invention is not limited thereto.

[0064] A guard ring 170 may be formed between the first region 161 and the adjacent first and second impurity-doped regions 120 and 130. The guard ring 170 is configured to reduce a dark count rate (DCR) and preferably has substantially the same first impurity doping concentration as that of the substrate 110.

[0065] An insulating film layer OX, such as an oxide film layer, may be formed on the front surface 111 of the substrate 110. A first metal contact region 181 connected to the first contact region 121 and a first metal wiring 185 electrically or physically connected to the first metal contact region 181 may be formed in the insulating film layer OX. The first metal wiring 185 may be a metal layer, such as aluminum (Al), and may function as a reflector that reflects light incident from the back surface 113 of the substrate 110 to form an optical path. A second metal contact region 183 connected to the second contact region 140 and a second metal wiring 187 electrically or physically connected to the second metal contact region 183 may be formed in the insulating film layer OX.

[0066] A planarization layer 191 may be formed on the rear surface 113 of the substrate 110, and a microlens 193 may be formed on the planarization layer 191.

[0067] FIG. 3 is a cross-sectional view illustrating a SPAD structure according to a second embodiment of the present invention.

[0068] A SPAD structure 2 according to a second embodiment of the present invention will be described in detail below. The SPAD structure 2 can be formed substantially identically to the SPAD structure 1 according to the first embodiment except for the guide wall 260, so only the guide wall 260 will be described in detail. Furthermore, for configurations similar to those of the first embodiment, the beginning of the drawing numbers of the first embodiment has been changed from "1" to "2."

[0069] 3, the SPAD structure 2 according to the second embodiment is characterized in that the second region 163 according to the first embodiment is not formed. That is, in the second embodiment, the guide wall 260 includes only a first region 261. The first region 261 extends to a predetermined depth within the substrate 210 from the front surface 211 of the substrate 210 toward the back surface 213 of the substrate 210. Preferably, the top surface of the first region 261 extends to a position higher than the top surface of the adjacent second impurity-doped region 230 (or to a position adjacent to the back surface 213 of the substrate 210). This configuration can maximize the prevention of charge generated between the guide wall 260 and the isolation region 250 from migrating to the side of the PN junction region formed by the first impurity-doped region 220 and the second impurity-doped region 230.

[0070] The guide wall 260 is preferably a first impurity-doped region having a higher concentration than the second impurity-doped region 230, and more preferably, the impurity doping concentration of the guide wall 260 gradually decreases as it extends upward, but there is no particular limitation thereto. Also, the first region 261 is preferably a first impurity-doped region having a lower concentration than the second contact region 240.

[0071] FIG. 4 is a cross-sectional view illustrating a SPAD structure according to a third embodiment of the present invention.

[0072] A SPAD structure 3 according to the third embodiment of the present invention will be described in detail below. The SPAD structure 3 can be formed substantially identically to the SPAD structure 1 according to the first embodiment, except for the guide wall 360, and therefore only the guide wall 360 will be described in detail. Furthermore, for configurations similar to those of the first embodiment, the first digit of the drawing number of the first embodiment has been changed from "1" to "3."

[0073] 4, in the SPAD structure 3 according to the third embodiment, the guide wall 360 may include a first region 361 and a second region 363. The first region 361 is a first conductive type impurity-doped region and may contact the adjacent isolation region 350 or may be spaced apart, similar to the first region 161 according to the first embodiment. The second region 363 may be formed to contact a side of the adjacent second impurity-doped region 330 on the first region 361. In this case, the top surface of the first region 361 may be substantially flush with the top surface of the second impurity-doped region 330 within the substrate 310, or may be formed at a higher position. Preferably, the doping concentration of the first impurity decreases toward the second contact region 340, the first region 361, and the second region 363, and more preferably, the doping concentration decreases gradually.

[0074] FIG. 5 is a cross-sectional view illustrating a SPAD structure according to a fourth embodiment of the present invention.

[0075] The following describes in detail the SPAD structure 4 according to the fourth embodiment of the present invention. The SPAD structure 4 is substantially the same as the SPAD pixel structure 3 according to the third embodiment except for the second region 463 of the guide wall 460, so only the guide wall 460 will be described in detail. Furthermore, for configurations similar to those of the third embodiment, the leading characters of the drawing numbers of the third embodiment have been changed from "3" to "4."

[0076] 5, the SPAD structure 4 according to the fourth embodiment is characterized in that the second impurity-doped region 430 is formed inside the second region 463. That is, the second region 463 is not a ring or disk type but has a continuous shape without an opening O. For example, the second region 463 may be formed to have a continuous shape that contacts a pair of adjacent isolation regions 450. Therefore, the second region 463 is formed to surround the second impurity-doped region 430. That is, the second impurity-doped region 430 may be doped with the first impurity at a lower concentration than the second region 463. This formation can prevent misalignment between the first impurity-doped region 420 and the second impurity-doped region 430 above it.

[0077] 6 to 11 are cross-sectional views illustrating a method for manufacturing a SPAD pixel structure according to one embodiment of the present invention.

[0078] Hereinafter, a method for manufacturing a SPAD structure according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The method for manufacturing the SPAD structure will be described based on a method for manufacturing a SPAD structure according to a third embodiment of the present invention.

[0079] 6, an isolation region 350 is formed in a substrate 310. The isolation region 350 may be formed by forming a mask pattern (not shown) on a front surface 311 of the substrate 310 and then performing a first impurity ion implantation process. The isolation region 350 may extend a predetermined depth from the front surface 311 of the substrate 310 toward the back surface 313.

[0080] 7, a second region 363 is formed in the substrate 310 in the unit pixel defined by the isolation region 350. The second region 363 is a first impurity lightly doped region, and can be formed by performing an ion implantation process after forming a mask pattern (not shown) on the front surface 311 of the substrate 310. The second region 363 can be formed in a ring or disk shape so that an opening O is formed.

[0081] At this time, the second region 363 may be formed continuously so that no opening O is formed, as in the SPAD pixel structure 4 of the fourth embodiment.

[0082] 8, a second impurity-doped region 330 may be formed inside the second region 363 in the substrate 310, and a first impurity-doped region 320 may be sequentially formed on the front surface 311 of the substrate 310. The second impurity-doped region 330 is preferably a first impurity-doped region having a lower concentration than the second region 363, and the first impurity-doped region 320 is preferably a second impurity-doped region having a lower concentration. In this case, the bottom surface of the second impurity-doped region 330 may be located closer to the front surface 311 of the substrate 310 than the bottom surface of the second region 363, and may be formed to substantially the same depth / height. The second impurity-doped region 330 and the first impurity-doped region 320 may be formed by forming a mask pattern (not shown) on the front surface 311 of the substrate 310 and then performing an ion implantation process, respectively.

[0083] Furthermore, when the second region 363 is formed continuously so that no opening O is formed, as in the SPAD pixel structure 4 of the fourth embodiment, a second impurity-doped region 330 may be formed by doping the second region 363 with second impurity ions, which is doped with a lower concentration of first conductivity type impurities than the second region 363.

[0084] 9, a first contact region 321 is formed in the first impurity-doped region 320, and a first region 361 and a second contact region 340 are formed between the front surface 311 of the substrate 310 and the isolation region 350. Each region may be formed through an ion implantation process using a mask pattern (not shown) formed on the front surface 311 of the substrate 310.

[0085] 10, an insulating film layer OX, metal contact regions 381 and 385, and metal wirings 383 and 387 are formed on the front surface 311 of the substrate 310. Then, referring to FIG.

[0086] Referring to FIG. 11, in a subsequent process, a rear surface 313 of a substrate 310 is ground, and then a planarization layer 391 and a microlens 393 are formed on the rear surface 313 .

[0087] The above detailed description exemplifies the present invention. Furthermore, the above content illustrates and describes preferred embodiments of the present invention, and the present invention can be used in various other combinations, modifications, and environments. That is, changes and modifications are possible within the scope of the inventive concept disclosed herein, the scope equivalent to the disclosed content, and / or the scope of skill or knowledge in the art. The above-described embodiments illustrate the best mode for realizing the technical ideas of the present invention, and various modifications are possible as required for specific application fields and uses of the present invention. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. [Explanation of symbols]

[0088] 1 SPAD structure 110 Substrate 111 Front of the board 113 Back of the board 120 first impurity doped region 121 First contact area 130 Second impurity doped region 140 Second Contact Area 150 Isolation Area 160 Guide Wall 161 1st area 163 Second area 170 Guard Ring 181 First metal contact area 183 Second metal contact area 185 First metal wiring 187 Second metal wiring 191 Planarization layer 193 Microlens A. Avalanche region A1 depletion region O Open mouth C Carrier

Claims

1. a substrate having a front surface and a back surface; a first impurity-doped region within the substrate on a front side of the substrate; a second impurity-doped region in the substrate above the first impurity-doped region; a guide wall surrounding sidewalls of the first impurity-doped region and the second impurity-doped region in the substrate.

2. the guide wall is a first conductivity type impurity doped region, 2. The SPAD structure of claim 1, wherein the first impurity-doped region is a second conductivity type impurity-doped region.

3. The SPAD structure according to claim 2 , wherein the guide wall includes a first region extending upward from the front surface to the rear surface of the substrate.

4. 4. The SPAD structure according to claim 3, wherein the first region has an upper surface located higher in the substrate than an upper surface of the second impurity-doped region.

5. The guide wall is 4. The SPAD structure of claim 3, further comprising a second region extending onto an upper surface of the second impurity-doped region adjacent to the first region.

6. The SPAD structure of claim 5 , wherein the second region contacts the second impurity-doped region.

7. The second region is 6. The SPAD structure as set forth in claim 5, wherein the second impurity-doped region has an opening at least partially open at its top surface.

8. The second region is 6. The SPAD structure according to claim 5, wherein the first region is a region doped with impurities of the first conductivity type at a lower concentration than the first region.

9. a first contact region in the first impurity-doped region on the front side of the substrate; The SPAD structure of claim 2 , further comprising: a second contact region spaced apart from the first contact region on the front side of the substrate.

10. 6. The SPAD structure of claim 5, further comprising a guard ring between the guide wall and the adjacent first and second impurity-doped regions.

11. The guard ring is 11. The SPAD structure according to claim 10, wherein the first region is a region doped with impurities of a first conductivity type at a lower concentration than the first and second regions.

12. a substrate having a front surface and a back surface; an isolation region on the unit pixel boundary side; a first impurity-doped region within the substrate on a front side of the substrate; a second impurity-doped region in the substrate above the first impurity-doped region; a first contact region in the first impurity-doped region; a second contact region between the front surface of the substrate and the isolation region; a guide wall surrounding sidewalls of the first impurity-doped region and the second impurity-doped region in the substrate, The guide wall is a first region on the second contact region; and a second region extending to contact a sidewall of an adjacent second impurity-doped region on the first region.

13. The first region is 13. The SPAD structure according to claim 12, wherein the first contact region is a first conductivity type impurity doped region having a lower concentration than the second contact region and a higher concentration than the second region.

14. 13. The SPAD structure of claim 12, wherein the doping concentration of the first conductivity type impurity gradually decreases in the second contact region, the first region, and the second region.

15. The second region is 13. The SPAD structure according to claim 12, wherein the upper surface thereof is located higher than the upper surface of the second impurity-doped region it contacts.

16. The first region is 13. The SPAD structure of claim 12, wherein the sidewalls of the first impurity-doped regions are spaced apart from each other.

17. The guide wall is 13. The SPAD structure of claim 12, wherein the first impurity-doped region is an opposite type impurity-doped region.

18. a substrate having a front surface and a back surface; a first impurity-doped region within the substrate on a front side of the substrate; a guide wall including a first region in the substrate separated from the first impurity-doped region and a second region across a unit pixel on the first region; a second impurity-doped region in the second region; The second impurity-doped region is A SPAD structure, characterized in that the second region is a region doped with impurities of a first conductivity type at a lower concentration than the second region.

19. The second impurity-doped region is 20. The SPAD structure of claim 18, wherein the SPAD structure is formed by implanting impurities of the second conductivity type into the second region after forming the second region.

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