Image sensor and method for manufacturing the same

Abstract

The present invention provides an image sensor and a manufacturing method thereof, comprising: a semiconductor substrate, a photodiode, a deep trench isolation structure, a first P-type deep well and a second P-type deep well. The deep trench isolation structure encloses the photodiode, and the intersection of adjacent sides of the deep trench isolation structure is disconnected. The first P-type deep well comprises a deep well block, and the projection of the deep well block on the semiconductor substrate covers the projection of the disconnected end of the intersection of the deep trench isolation structure on the semiconductor substrate. The structure of the first P-type deep well can be formed by using a photomask, which reduces the cost. The intersection of adjacent sides of the deep trench isolation structure is disconnected, which greatly improves the white pixels; at the same time, the first P-type deep well ion implantation compensates for the plasma damage caused by the etching process of the deep trench isolation structure to form the groove, further reduces the white pixels, and improves the pixel quality; and the deep well block provides electrical isolation of the disconnected area at the intersection of the deep trench isolation structure, avoiding the problem of high light overflow and crosstalk.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to an image sensor and a manufacturing method thereof. Background Art

[0002] CMOS image sensors (CIS) are widely used in digital still cameras, cellular phones, security cameras, and in medical, automotive, and other applications. A typical image sensor operates in response to image light reflected from an external scene being incident on the image sensor. The image sensor includes an array of pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate an image charge immediately after absorbing the image light. The image charge of each of the pixels can be measured as an output voltage of each photosensitive element that varies with the incident image light. In other words, the amount of image charge generated is proportional to the intensity of the image light that is utilized to generate a digital image representing the external scene.

[0003] As the requirements for CIS applications become higher and higher, the corresponding pixel size requirements are getting smaller and smaller, so that more pixels can be obtained in the same area. From the perspective of pixel design, the spacing between adjacent pixels is also reduced. The advantage of small pixels is that more pixels can be obtained in the same area, and higher pixels and clearer images can be obtained; this means that the same full well capacity as large pixels can be obtained in a smaller photosensitive area. To obtain the same full well capacity in a smaller area, it can only be developed in the depth direction of PD (Photodiode). From a process perspective, it means that the N-type ions that form PD and the P-type ions that isolate each PD are implanted deeper. In CIS chips, the P-type deep well (Deep P+Well, DPW) is a process for isolating the photodiode in each pixel, but for these layers that require high-dose ion implantation, a relatively thick photoresist (for example, >2um) is required. Under the condition of the same high aspect ratio of the photoresist, the reduction in the spacing between adjacent pixels means that the process difficulty is doubled, and the corresponding process cost is higher; and the thicker photoresist becomes the source of white pixels in the image sensor, and white pixels affect the pixel quality of the image sensor. Summary of the invention

[0004] The object of the present invention is to provide an image sensor and a manufacturing method thereof, which can reduce process costs, reduce white pixels, improve pixel quality, and avoid highlight overflow and crosstalk problems.

[0005] The present invention provides an image sensor, comprising:

[0006] a semiconductor substrate having opposing first and second sides;

[0007] a photodiode disposed in the semiconductor substrate;

[0008] a deep trench isolation structure enclosing a portion of the photodiode close to the second side, the deep trench isolation structure extending from the second side toward the first side into the semiconductor substrate; the intersection of adjacent sides of the deep trench isolation structure is disconnected;

[0009] a first P-type deep well, comprising a deep well block, wherein a projection of the deep well block on the semiconductor substrate covers a projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate;

[0010] A second P-type deep well encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate.

[0011] Furthermore, the deep trench isolation structure includes a trench isolation lattice structure formed by the intersection of a plurality of first trench isolations along a first direction and a plurality of second trench isolations along a second direction, and a graphic structure obtained by removing a cross portion located at the intersection of the first direction and the second direction.

[0012] Furthermore, the second P-type deep well includes a deep well grid structure formed by the intersection of a plurality of first deep well structures along the first direction and a plurality of second deep well structures along the second direction.

[0013] Furthermore, the second P-type deep well is arranged corresponding to the deep trench isolation structure, and a projection of the second P-type deep well on the semiconductor substrate covers a projection of the deep trench isolation structure on the semiconductor substrate.

[0014] Furthermore, the image sensor includes a plurality of the photodiodes, and a portion of each of the photodiodes close to the first side is surrounded by the deep well grid structure; and a portion of each of the photodiodes close to the second side is surrounded by the trench isolation grid structure.

[0015] Furthermore, the first P-type deep well includes an array structure formed by a plurality of the deep well blocks, and the projection of each of the deep well blocks on the semiconductor substrate corresponds to covering an intersection and disconnection point between the first trench isolation and the second trench isolation; at the same time, the projection of each of the deep well blocks on the semiconductor substrate corresponds to covering an intersection between the first deep well structure and the second deep well structure.

[0016] Furthermore, in the thickness direction of the semiconductor substrate, the second P-type deep well contacts or partially overlaps with the deep trench isolation structure.

[0017] Furthermore, in the thickness direction of the semiconductor substrate, the first P-type deep well and the deep trench isolation structure are located within the same depth range in the semiconductor substrate, and the cross-disconnected ends of the trench isolation grid structure are all placed in the first P-type deep well.

[0018] The present invention also provides a method for manufacturing an image sensor, comprising:

[0019] Providing a semiconductor substrate having a first side and a second side opposite to each other; a photodiode is formed in the semiconductor substrate;

[0020] forming a deep trench isolation structure, which encloses a portion of the photodiode close to the second side, wherein the deep trench isolation structure extends from the second side toward the first side into the semiconductor substrate; and the intersection of adjacent sides of the deep trench isolation structure is disconnected;

[0021] Performing a first P-type ion implantation to form a first P-type deep well, which includes a deep well block, wherein a projection of the deep well block on the semiconductor substrate covers a projection of the disconnected end of the intersection of the deep trench isolation structure on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate;

[0022] A second P-type ion implantation is performed to form a second P-type deep well, which encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate.

[0023] Furthermore, the injection energy of the first P-type deep well is greater than the injection energy of the second P-type deep well.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides an image sensor and a manufacturing method thereof, comprising: a semiconductor substrate having a first side and a second side opposite to each other; a photodiode arranged in the semiconductor substrate; a deep trench isolation structure enclosing a portion of the photodiode close to the second side, the deep trench isolation structure extending from the second side toward the first side into the semiconductor substrate; the deep trench isolation structure being disconnected at the intersection of adjacent sides; a second P-type deep well enclosing a portion of the photodiode close to the first side; the second P-type deep well extending from the first side toward the second side into the semiconductor substrate; a first P-type deep well comprising a deep well block, the projection of the deep well block on the semiconductor substrate covering the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate; the first P-type deep well extending from the second side toward the first side into the semiconductor substrate.

[0026] The spacing between adjacent deep well blocks in the first P-type deep well of the present invention is relatively large, and the photoresist can be conformal within the spacing range, and the first P-type deep well can be manufactured by using one photomask and one photolithography process. The structural design of the first P-type deep well of the present invention reduces the process cost and reduces the process time. The adjacent sides of the deep trench isolation structure enclosing the photodiode of the present invention are disconnected at the intersection, so that the white pixels of the image sensor are greatly improved; at the same time, the projection of the deep well block of the first P-type deep well on the semiconductor substrate covers the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate, and the disconnected end of the deep trench isolation structure at the intersection is arranged in the deep well block in the first P-type deep well, and the first P-type deep well is formed by injecting P-type ions, and the ion injection compensates for the plasma damage caused by the dry etching process of the deep trench isolation structure to form the groove, further reducing the white pixels and improving the pixel quality; at the same time, the deep well block of the first P-type deep well provides electrical isolation of the disconnected area at the intersection of the deep trench isolation structure, avoiding the phenomenon that a large number of electrons generated by the photodiode flow to the adjacent photodiode, that is, avoiding the high light overflow problem and crosstalk problem caused by the disconnection at the intersection of the deep trench isolation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a longitudinal section of an image sensor along the Y direction.

[0028] Figure 2 For an image sensor corresponding to Figure 1 Schematic diagram of the cross section at AA'.

[0029] Figure 3 For an image sensor corresponding to Figure 1 Schematic diagram of the cross section at BB'.

[0030] Figure 4It is a schematic diagram of a longitudinal section of an image sensor along the X direction.

[0031] Figure 5 It is a schematic diagram of a longitudinal section of an image sensor along the C direction.

[0032] Figure 6 A schematic cross-sectional view of an improved deep trench isolation for an image sensor.

[0033] Figure 7 FIG. 4 is a cross-sectional schematic diagram of an image sensor including a first P-type deep well and a second P-type deep well according to an embodiment of the present invention.

[0034] Figure 8 It is a cross-sectional schematic diagram of an image sensor including a deep trench isolation structure and a first P-type deep well according to an embodiment of the present invention.

[0035] Fig. 9 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor according to an embodiment of the present invention along the X direction.

[0036] Fig.10 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor according to an embodiment of the present invention along the Y direction.

[0037] Fig.11 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor along direction C according to an embodiment of the present invention.

[0038] Fig.12 FIG. 4 is a flow chart of a method for manufacturing an image sensor according to an embodiment of the present invention.

[0039] The reference numerals are as follows:

[0040] 001-image sensor; 002-semiconductor substrate; 004-first side; 006-second side; 012-photodiode; 014-P-type deep well; 016-deep trench isolation structure; 018-P-type deeper well; 017-deep trench isolation; a-first side; b-second side; c-third side; d-fourth side;

[0041] 100 - image sensor; 102 - semiconductor substrate; 104 - first side; 106 - second side; 112 - photodiode; 114 - second P-type deep well; 116 - deep trench isolation structure; 118 - first P-type deep well. DETAILED DESCRIPTION

[0042] As described in the background technology, the pixel size requirements corresponding to the image sensor are getting smaller and smaller. In the CIS chip P-type deep well process, thicker photoresist is required, which has high process difficulty and cost. In addition, thicker photoresist becomes the source of white pixels, which affects the pixel quality of the image sensor.

[0043] Figure 1is a schematic diagram of a longitudinal section of an image sensor along the Y direction (perpendicular to the upper and lower surfaces of the semiconductor substrate); Figure 2 For an image sensor corresponding to Figure 1 Schematic diagram of the cross section at AA' (parallel to the upper and lower surfaces of the semiconductor substrate); Figure 3 For an image sensor corresponding to Figure 1 Schematic diagram of the cross section at BB'; Figure 4 is a schematic diagram of a longitudinal section of an image sensor along the X direction; Figure 5 It is a schematic diagram of a longitudinal section of an image sensor along the C direction (diagonal direction).

[0044] like Figures 1 to 5 As shown, the image sensor 001 includes a semiconductor substrate 002 , a photodiode 012 , a P-type deep well (DPW, Deep P Well) 014 , a P-type deeper well (DDPW, Deep Deep P Well) 018 , and a deep trench isolation structure (DTI) 016 .

[0045] The semiconductor substrate 002 has a first side 004 and a second side 006 opposite to each other. A P-type deep well 014 extends from the first side 004 toward the second side 006 into the semiconductor substrate 002. The P-type deep well 014 includes a deep well grid structure formed by the intersection of a plurality of deep wells 1 along a first direction X and a plurality of deep wells 2 along a second direction Y. A deep trench isolation structure 016 extends from the second side 006 toward the first side 004 into the semiconductor substrate 002. The deep trench isolation structure 016 includes a trench isolation grid structure formed by the intersection of a plurality of trench isolations 1 along the first direction X and a plurality of trench isolations 2 along the second direction Y. A P-type deeper well 018 is arranged on the inner annular circumference of each grid of the deep trench isolation structure 016; a P-type deeper well (DDPW) 018 is formed on both sides of each trench isolation edge constituting the grid of the trench isolation grid structure, and the P-type deeper well (DDPW) 018 is a ring structure, which can be arranged in an array. The P-type deeper well (DDPW) 018 extends from the second side 006 toward the first side 004 into the semiconductor substrate 002 .

[0046] The image sensor 001 includes a plurality of photodiodes 012, and a portion of each photodiode 012 close to the first side 004 is surrounded by a deep well grid structure of a P-type deep well 014; a portion of each photodiode close to the second side 006 is surrounded by a P-type deeper well (DDPW) 018. Adjacent photodiodes 012 are spaced apart by two single sides of the P-type deeper well (DDPW) 018, and the P-type deeper well (DDPW) 018 is called a double-spaced structure.

[0047] The production of the P-type deeper well (DDPW) 018 includes: forming a thicker photoresist on the semiconductor substrate 002, forming an opening corresponding to the position of the P-type deeper well (DDPW) 018 on the photoresist by exposure, and then injecting P-type ions from the opening to form the P-type deeper well (DDPW) 018.

[0048] like Figure 3 As shown, the pixel size requirement is getting smaller and smaller, and the spacing between adjacent pixel points is also reduced accordingly, and the corresponding spacing between adjacent photodiodes 012 is also reduced, so the strip width of the P-type deeper well (DDPW) 018 on one side is required to be very narrow, and the strip width of the deep trench isolation structure 016 on one side is also very narrow. The P-type deeper well (DDPW) 018 includes, for example, a first side a, a second side b, a third side c, and a fourth side d. Since the spacing between adjacent photodiodes 012 is very small, the strip width of the P-type deeper well (DDPW) 018 on one side is very narrow, and the spacing between adjacent single sides of the P-type deeper well (DDPW) 018 (i.e., the strip width of the deep trench isolation structure 016 on one side) is also very narrow, it is difficult to form the first side a and the second side b at the same time through a single photolithography process, the strip width of the first side a and the second side b themselves is very narrow, and the spacing between the first side a and the second side b is also very narrow, and the photoresist is difficult to conform to the shape at a small size and is easy to collapse.

[0049] The production of the P-type deeper well (DDPW) 018 requires two masks (masks) and two photolithography processes. The first mask, for example, includes the pattern of the first side a and the third side c, and the first photolithography process is performed through the first mask to form the structure of the P-type deeper well (DDPW) 018 including the first side a and the third side c. The second mask includes the pattern of the second side b and the fourth side d, and the second photolithography process is performed through the second mask to form the structure of the P-type deeper well (DDPW) 018 including the second side b and the fourth side d. In this way, the opening interval of the first mask becomes the distance between the first side a and the third side c, the opening interval becomes larger, and the photoresist is easy to maintain its shape.

[0050] The image sensor 001 including this P-type deeper well (DDPW) 018 requires two masks (masks) to perform two photolithography processes to form, which has a high manufacturing process cost, and the thicker photoresist becomes the source of white pixels of the image sensor, which affects the pixel quality of the image sensor.

[0051] In order to improve the pixel performance of the image sensor, reduce the source of white pixels caused by thicker photoresist and reduce process costs, the inventor tried to remove the P-type deeper well (DDPW) 018 structure in the image sensor 001 to optimize the pixels, and found that the white pixels were very serious. The inventor also tried to optimize and improve the deep trench isolation structure 016 and modified the deep trench isolation structure 016.

[0052] like Figure 3As shown, the deep trench isolation structure 016 before improvement includes a trench isolation grid structure formed by a plurality of trench isolations 1 along a first direction X and a plurality of trench isolations 2 along a second direction Y intersecting each other.

[0053] like Figure 3 and Figure 6 As shown, the improved deep trench isolation 017, based on the deep trench isolation 016 before the improvement, removes all the cross positions (cross positions) in the trench isolation grid structure where the first direction and the second direction overlap, that is, the improved deep trench isolation 017 is designed to be unconnected (disconnected at the overlapping cross). It is found that the white pixels of the image sensor are greatly improved by such improvement of the deep trench isolation, but the part of the photodiode 012 near the overlapping cross causes very serious blooming and crosstalk problems due to the lack of physical isolation of the deep trench isolation (DTI). The blooming phenomenon is the phenomenon that a large number of electrons flow to the adjacent pixel photodiodes in the photodiode area under strong light conditions. Crosstalk is an important noise source of the photodiode array. Crosstalk is defined as the activity of injecting noise into adjacent pixels of the image sensor. Its essence is the interference noise generated by the coupling of one signal to another signal. The existence of crosstalk will reduce the clarity of the image and seriously affect the quality of the final output image.

[0054] Based on the above research, in order to take into account the problems of white pixels and highlight overflow at the same time, an embodiment of the present invention provides an image sensor. The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0055] For ease of description, some embodiments of the present application may use spatially relative terms such as "above", "below", "top", "below", etc. to describe the relationship between one element or component and another (or other) elements or components as shown in the various figures of the embodiments. It should be understood that in addition to the orientations described in the drawings, the spatially relative terms are also intended to include different orientations of the device in use or operation. For example, if the device in the drawings is turned over, the elements or components described as being "below" or "below" other elements or components will subsequently be positioned as being "above" or "above" other elements or components. The terms "first", "second", etc. below are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It is to be understood that these terms used in this way are interchangeable where appropriate.

[0056] An embodiment of the present invention provides an image sensor, including:

[0057] a semiconductor substrate having opposing first and second sides;

[0058] a photodiode disposed in the semiconductor substrate;

[0059] a deep trench isolation structure enclosing a portion of the photodiode close to the second side, the deep trench isolation structure extending from the second side toward the first side into the semiconductor substrate; the intersection of adjacent sides of the deep trench isolation structure is disconnected;

[0060] A second P-type deep well encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate;

[0061] A first P-type deep well, comprising a deep well block, the projection of the deep well block on the semiconductor substrate covers the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate.

[0062] Combine the following Figures 7 to 11 An image sensor according to an embodiment of the present invention is described in detail. Figure 7 FIG. 4 is a cross-sectional schematic diagram of an image sensor including a first P-type deep well and a second P-type deep well according to an embodiment of the present invention. Figure 8 It is a cross-sectional schematic diagram of an image sensor including a deep trench isolation structure and a first P-type deep well according to an embodiment of the present invention. Fig. 9 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor according to an embodiment of the present invention along the X direction. Fig.10 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor according to an embodiment of the present invention along the Y direction. Fig.11 FIG. 4 is a schematic longitudinal cross-sectional view of an image sensor according to an embodiment of the present invention along direction C (diagonal direction).

[0063] like Figures 7 to 11 As shown, the image sensor 100 according to the embodiment of the present invention includes: a semiconductor substrate 102 , a photodiode 112 , a second P-type deep well 114 , a deep trench isolation structure 116 and a first P-type deep well 118 .

[0064] A semiconductor substrate 102 has a first side 104 and a second side 106 opposite to each other. The first side 104 is, for example, a front side of the semiconductor substrate 102, and the second side 106 is, for example, a back side of the semiconductor substrate 102. The semiconductor substrate 102 may be a bulk silicon substrate, an epitaxial substrate, or a doped silicon substrate (e.g., a P-type doped silicon substrate or an N-type doped silicon substrate), or a silicon-on-insulator (SOI) substrate. In some embodiments, the semiconductor substrate may include one or more of a doped semiconductor region and / or an undoped semiconductor region, a silicon epitaxial layer, and other semiconductor structures formed on the substrate.

[0065] A photodiode 112 is disposed in the semiconductor substrate 102 proximate the first side 104 , wherein the photodiode 112 accumulates image charge generated in the photodiode 112 in response to incident light directed through the second side 106 .

[0066] A second P-type deep well (DPW, Deep P Well) 114 encloses the portion of the photodiode 112 close to the first side 104; the second P-type deep well 114 extends from the first side 104 toward the second side 106 into the semiconductor substrate 102. The second P-type deep well 114 may include a deep well grid structure formed by intersecting a plurality of first deep well structures along the first direction X and a plurality of second deep well structures along the second direction Y. Exemplarily, each of the series of deep well structures of the second P-type deep well 114 may extend into the semiconductor substrate 102 by a distance ranging from 2 μm to 5 μm.

[0067] A deep trench isolation structure 116 encloses a portion of the photodiode 112 near the second side 106, and the deep trench isolation structure 116 extends from the second side 106 toward the first side 104 into the semiconductor substrate 102. The thickness of the deep trench isolation structure 116 is less than the thickness of the semiconductor substrate 102 between the first side 104 and the second side 106. The intersection of adjacent sides of the deep trench isolation structure 116 is disconnected. Specifically, the deep trench isolation structure 116 may include a trench isolation grid structure formed by the intersection of a plurality of first trench isolations along a first direction X and a plurality of second trench isolations along a second direction Y, and a pattern structure obtained by removing a portion of a cross position where the first direction X and the second direction Y intersect. Exemplarily, depending on the thickness of the semiconductor substrate 102, each of a series of trench isolations of the deep trench isolation structure 116 may extend into the semiconductor substrate 102 by a distance ranging from 2 μm to 5 μm.

[0068] The second P-type deep well 114 is arranged corresponding to the deep trench isolation structure 116, and the projection of the second P-type deep well 114 on the semiconductor substrate 102 covers the projection of the deep trench isolation structure 116 on the semiconductor substrate 102. In the thickness direction of the semiconductor substrate 102, the second P-type deep well 114 contacts or partially overlaps with the deep trench isolation structure 116. Exemplarily, the deep trench isolation structure 116 and the second P-type deep well 114 may extend to each other by a small thickness in the longitudinal direction.

[0069] The image sensor 100 includes a plurality of photodiodes 112, wherein the portion of each photodiode 112 close to the first side 104 (upper portion) is surrounded by the deep well grid structure of the second P-type deep well 114; and the portion of each photodiode 112 close to the second side 106 (lower portion) can be surrounded by the trench isolation grid structure of the deep trench isolation structure 116. The deep trench isolation structure 116 is formed by filling a dielectric material in a trench, and the deep trench isolation structure 116 is used to enclose each photodiode to isolate photocarriers. The second P-type deep well 114 and the deep trench isolation structure 116 provide electrical isolation and optical isolation between adjacent photodiodes 112. In the process of forming the deep trench isolation structure 116, since the trench is deeper, there are more defects caused by etching. After the trench is formed, a thinner line oxide layer can be formed in the trench through a short oxidation process to repair the defects caused by etching.

[0070] A first P-type deep well 118 includes a deep well block, the projection of the deep well block on the semiconductor substrate 102 covers the projection of the disconnected end of the deep trench isolation structure 116 at the intersection on the semiconductor substrate 102; the first P-type deep well 118 extends from the second side 106 toward the first side 104 into the semiconductor substrate 102.

[0071] Exemplarily, the first P-type deep well 118 includes an array structure formed by a plurality of the deep well blocks. The deep well block is regarded as a point, and the first P-type deep well 118 can also be regarded as a point array structure. The first P-type deep well (DDPW, Deep Deep PWell) is located at a deeper position in the semiconductor substrate than the second P-type deep well. The projection of each of the deep well blocks on the semiconductor substrate 102 corresponds to a cross-disconnection between the first trench isolation and the second trench isolation of the deep trench isolation structure 116; at the same time, the projection of each of the deep well blocks on the semiconductor substrate 102 corresponds to a cross-connection between the first deep well structure and the second deep well structure of the second P-type deep well 114. In the thickness direction of the semiconductor substrate 102, the first P-type deep well 118 and the deep trench isolation structure 116 are located within the same depth range in the semiconductor substrate, and the cross-disconnected ends (e.g., four ends) of the trench isolation grid structure 116 are all placed in the first P-type deep well 118. In one embodiment, the first P-type deep well 118 extends longitudinally to the surface of the second side 106; in another embodiment, the first P-type deep well 118 may not extend longitudinally to the surface of the second side 106, that is, the lower end (the end close to the second side) of the first P-type deep well is still located in the semiconductor substrate. The first P-type deep well 118 may contact or partially overlap with the second P-type deep well 114 in the longitudinal direction.

[0072] Each of the photodiodes 112 has a box-shaped structure. It should be understood by those skilled in the art that each of the photodiodes 112 may include a doped region deeply implanted with a dopant on the first side 104 into the semiconductor substrate 102 by an ion implantation process, the dopant having a conductivity type opposite to that of the semiconductor substrate 102. In one embodiment, the doped region of the photodiode may be formed by implanting n-type dopants of arsenic (As) or phosphorus into the semiconductor substrate 102, which is a p-type doped semiconductor substrate, multiple times with different implantation energies to obtain a desired doping profile in order to achieve a desired full well capacity. However, in another example, the polarity of the layer / region may be reversed, for example, the doped region of the photodiode may be formed by a p-type dopant of boron (B) into the semiconductor substrate 102, which is an n-type semiconductor substrate. According to the teachings of the present invention, the doped region of the photodiode may have a shape (e.g., square, rectangular, circular, or any suitable shape) and a size (e.g., the length and width of the photodiode implantation region) based on the design requirements and pixel size configuration of the corresponding image sensor.

[0073] like Figure 8As shown, in one example, the photodiodes 112 may be arranged in an array having a series of horizontal rows and vertical columns, but the array has one pixel level along the depth. Therefore, in order to isolate any one pixel from the surrounding pixels, the deep trench isolation structure 116 enclosing each pixel may have four sides. In one example, the outer horizontal trenches and outer vertical trenches of the grid may be omitted, so that the pixels on the outer perimeter of the array may have a three-sided isolation structure, except that the pixels on the corners of the array may have a two-sided isolation structure. However, any one pixel in the array may be enclosed on four sides by a series of trenches of the deep trench isolation structure 116. It should be understood that the deep trench isolation structure 116 may refer to the entire grid structure or any portion thereof.

[0074] The present invention will Figure 3 The P-type deeper well (DDPW) 018 in the Figure 8 The first P-type deep well 118 in. Figure 3 The P-type deeper well (DDPW) 018 in the present invention requires two masks. The spacing between adjacent deep well blocks in the first P-type deep well 118 of the present invention is large. The photoresist can be conformal within the spacing range. The first P-type deep well 118 can be made by using one mask and one photolithography process. The structural design of the first P-type deep well 118 of the present invention reduces the process cost and reduces the process time. The adjacent sides of the deep trench isolation structure enclosing the photodiode of the present invention are disconnected at the intersection, so that the white pixels of the image sensor are greatly improved; at the same time, the projection of the deep well block of the first P-type deep well on the semiconductor substrate covers the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate, and the disconnected end of the deep trench isolation structure at the intersection is arranged in the deep well block in the first P-type deep well, and the first P-type deep well is formed by injecting P-type ions, and the ion injection compensates for the plasma damage caused by the dry etching process of the deep trench isolation structure to form the groove, further reducing the white pixels and improving the pixel quality; at the same time, the deep well block of the first P-type deep well provides electrical isolation of the disconnected area at the intersection of the deep trench isolation structure, avoiding the phenomenon that a large number of electrons generated by the photodiode flow to the adjacent photodiode, that is, avoiding the high light overflow problem and crosstalk problem caused by the disconnection at the intersection of the deep trench isolation structure.

[0075] The present invention also provides a method for manufacturing an image sensor, such as Fig.12 As shown, including:

[0076] Providing a semiconductor substrate having a first side and a second side opposite to each other; a photodiode is formed in the semiconductor substrate;

[0077] forming a deep trench isolation structure, which encloses a portion of the photodiode close to the second side, wherein the deep trench isolation structure extends from the second side toward the first side into the semiconductor substrate; and the intersection of adjacent sides of the deep trench isolation structure is disconnected;

[0078] Performing a first P-type ion implantation to form a first P-type deep well, which includes a deep well block, wherein a projection of the deep well block on the semiconductor substrate covers a projection of the disconnected end of the intersection of the deep trench isolation structure on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate;

[0079] A second P-type ion implantation is performed to form a second P-type deep well, which encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate.

[0080] Specifically, Figures 7 to 11 As shown, a semiconductor substrate 102 is provided. The semiconductor substrate 102 may be a silicon substrate, or the material of the semiconductor substrate 100 may also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, etc., which are suitable materials for CMOS image sensors. The semiconductor substrate 102 may also be a silicon substrate on an insulator surface or a germanium substrate on an insulator surface, or a substrate with an epitaxial layer grown. The semiconductor substrate 100 includes a pixel device, and the pixel device may include a photodiode 112. Specifically, the photodiode 102 may generate photogenerated carriers, i.e., electrons, when excited by external light intensity. The photodiode 102 may be formed by an ion implantation process, and by controlling the energy and concentration of the ion implantation, the depth and implantation range of the ion implantation may be controlled, thereby controlling the depth and thickness of the photodiode 102.

[0081] A deep trench isolation structure 116 is formed to enclose a portion of the photodiode 112 close to the second side 106, and the deep trench isolation structure 116 extends from the second side 106 toward the first side 104 into the semiconductor substrate 102; the intersection of adjacent sides of the deep trench isolation structure 116 is disconnected. A deep trench is formed by etching from the second side 106 of the semiconductor substrate 102 toward the first side through a dry etching process, and a dielectric layer is filled in the deep trench to form the deep trench isolation structure 116.

[0082] A first P-type ion implantation is performed to form a first P-type deep well 118, which includes a deep well block, the projection of the deep well block on the semiconductor substrate 102 covers the projection of the disconnected end of the deep trench isolation structure 116 at the intersection on the semiconductor substrate 102; the first P-type deep well 118 extends from the second side toward the first side into the semiconductor substrate 102.

[0083] A second P-type ion implantation is performed to form a second P-type deep well 114 , which encloses a portion of the photodiode 112 close to the first side 104 ; the second P-type deep well 114 extends from the first side 104 toward the second side 106 into the semiconductor substrate 102 .

[0084] The first P-type deep well 118 is located deeper in the semiconductor substrate 102 than the second P-type deep well 114, so the injection energy of the first P-type deep well 118 is greater than the injection energy of the second P-type deep well 114. The ion injection depth of the first P-type deep well 118 is greater than the N-type injection of the photodiode 112 in the pixel area to ensure that electrons do not overflow to adjacent pixels to cause crosstalk. The injection depth is controlled by the injection energy, and its isolation effect also depends on the injection dose.

[0085] Specifically, in the process of performing the first P-type ion implantation to form the first P-type deep well 118, the doping ions of the first P-type deep well 118 may be boron B, the implantation energy may be 800Kev to 1200Kev, and the implantation dose may be, for example, 200E3cm -3 Up to 500E3cm -3 In the process of performing the second P-type ion implantation to form the second P-type deep well 114, the doping ions of the second P-type deep well 114 may be boron B, the implantation energy may be 600Kev to 900Kev, and the implantation dose may be, for example, 200E3cm -3 Up to 500E3cm -3 .

[0086] In summary, the present invention provides an image sensor and a manufacturing method thereof, comprising: a semiconductor substrate having a first side and a second side opposite to each other; a photodiode, which is arranged in the semiconductor substrate; a deep trench isolation structure, which encloses a portion of the photodiode close to the second side, and the deep trench isolation structure extends from the second side toward the first side into the semiconductor substrate; the deep trench isolation structure is disconnected at the intersection of adjacent sides; a second P-type deep well, which encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate; a first P-type deep well, which comprises a deep well block, the projection of the deep well block on the semiconductor substrate covers the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate.

[0087] The spacing between adjacent deep well blocks in the first P-type deep well of the present invention is relatively large, and the photoresist can be conformal within the spacing range, and the first P-type deep well can be manufactured by using one photomask and one photolithography process. The structural design of the first P-type deep well of the present invention reduces the process cost and reduces the process time. The adjacent sides of the deep trench isolation structure enclosing the photodiode of the present invention are disconnected at the intersection, so that the white pixels of the image sensor are greatly improved; at the same time, the projection of the deep well block of the first P-type deep well on the semiconductor substrate covers the projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate, and the disconnected end of the deep trench isolation structure at the intersection is arranged in the deep well block in the first P-type deep well, and the first P-type deep well is formed by injecting P-type ions, and the ion injection compensates for the plasma damage caused by the dry etching process of the deep trench isolation structure to form the groove, further reducing the white pixels and improving the pixel quality; at the same time, the deep well block of the first P-type deep well provides electrical isolation of the disconnected area at the intersection of the deep trench isolation structure, avoiding the phenomenon that a large number of electrons generated by the photodiode flow to the adjacent photodiode, that is, avoiding the high light overflow problem and crosstalk problem caused by the disconnection at the intersection of the deep trench isolation structure.

[0088] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0089] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. An image sensor, characterized in that: include: a semiconductor substrate having opposing first and second sides; a photodiode disposed in the semiconductor substrate; a deep trench isolation structure enclosing a portion of the photodiode close to the second side, the deep trench isolation structure extending from the second side toward the first side into the semiconductor substrate; The intersections of adjacent sides of the deep trench isolation structure are disconnected; a first P-type deep well, comprising a deep well block, wherein a projection of the deep well block on the semiconductor substrate covers a projection of the disconnected end of the deep trench isolation structure at the intersection on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate; A second P-type deep well encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate.

2. The image sensor according to claim 1, wherein: The deep trench isolation structure comprises a trench isolation grid structure formed by the intersection of a plurality of first trench isolations along a first direction and a plurality of second trench isolations along a second direction, and a graphic structure obtained by removing a cross portion located at the intersection of the first direction and the second direction.

3. The image sensor according to claim 2, wherein: The second P-type deep well comprises a deep well grid structure formed by the intersection of a plurality of first deep well structures along the first direction and a plurality of second deep well structures along the second direction.

4. The image sensor according to claim 3, wherein: The second P-type deep well is arranged corresponding to the deep trench isolation structure, and a projection of the second P-type deep well on the semiconductor substrate covers a projection of the deep trench isolation structure on the semiconductor substrate.

5. The image sensor according to claim 3, wherein: The image sensor includes a plurality of the photodiodes, wherein a portion of each of the photodiodes close to the first side is surrounded by the deep well grid structure; and a portion of each of the photodiodes close to the second side is surrounded by the trench isolation grid structure.

6. The image sensor according to claim 3, wherein: The first P-type deep well includes an array structure formed by a plurality of the deep well blocks, and the projection of each of the deep well blocks on the semiconductor substrate corresponds to covering an intersection and disconnection point between the first trench isolation and the second trench isolation; at the same time, the projection of each of the deep well blocks on the semiconductor substrate corresponds to covering an intersection point between the first deep well structure and the second deep well structure.

7. The image sensor according to claim 1, wherein: In the thickness direction of the semiconductor substrate, the second P-type deep well contacts or partially overlaps with the deep trench isolation structure.

8. The image sensor according to claim 2, wherein: In the thickness direction of the semiconductor substrate, the first P-type deep well and the deep trench isolation structure are located within the same depth range in the semiconductor substrate, and the cross-disconnected ends of the trench isolation grid structure are all placed in the first P-type deep well.

9. A method for manufacturing an image sensor, characterized in that: include: Providing a semiconductor substrate having a first side and a second side opposite to each other; a photodiode is formed in the semiconductor substrate; forming a deep trench isolation structure enclosing a portion of the photodiode close to the second side, the deep trench isolation structure extending from the second side toward the first side into the semiconductor substrate; The intersections of adjacent sides of the deep trench isolation structure are disconnected; Performing a first P-type ion implantation to form a first P-type deep well, which includes a deep well block, wherein a projection of the deep well block on the semiconductor substrate covers a projection of the disconnected end of the intersection of the deep trench isolation structure on the semiconductor substrate; the first P-type deep well extends from the second side toward the first side into the semiconductor substrate; A second P-type ion implantation is performed to form a second P-type deep well, which encloses a portion of the photodiode close to the first side; the second P-type deep well extends from the first side toward the second side into the semiconductor substrate.

10. The method for manufacturing an image sensor according to claim 9, wherein: The injection energy of the first P-type deep well is greater than the injection energy of the second P-type deep well.

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