Image sensor and electronic device

Abstract

The utility model discloses a kind of image sensor and electronic equipment, image sensor includes mutually laminated semiconductor structure layer and optical structure layer, semiconductor structure layer is equipped with multiple array distribution photosensitive unit and by multiple isolation bar mutually crossing grid-shaped structure's channel isolation structure, optical structure layer includes by multiple grid bar mutually crossing grid-shaped structure's grid structure, the projection of grid structure on semiconductor structure layer completely covers channel isolation structure, and in arbitrary position, the width of grid bar is all greater than the width of isolation bar. One side can make the partial reflected light from the metal layer below photosensitive unit be blocked by grid structure, on the other hand, the large-angle reflected light reflected back from lens group or other optical elements also be blocked by grid structure, and cannot enter photosensitive unit again, so that crosstalk and glare problem caused by near-infrared waveband reflected light can be improved, to improve image contrast.

Description

Technical Field

[0001] This utility model relates to the field of image sensor technology, and in particular to an image sensor and electronic device. Background Technology

[0002] CMOS image sensors (CIS) are ubiquitous in our daily lives, from smartphones to cars, security cameras, robots, and AR / VR entertainment devices. An image sensor is a device that converts light signals into electrical signals. Commercially available image sensor chips typically fall into two main categories: charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensor chips.

[0003] Compared to traditional CCD sensors (charge-coupled devices), CMOS image sensors (CIS) offer advantages such as low power consumption, low cost, and compatibility with CMOS processes, leading to their increasingly widespread application. Currently, CMOS image sensors are used not only in consumer electronics, such as miniature digital cameras (DSCs), mobile phone cameras, camcorders, and digital SLRs (DSLRs), but also in automotive electronics, surveillance, biotechnology, and medicine. The pixel unit of a CMOS image sensor is the core component responsible for light sensing. The most common pixel unit is an active pixel structure containing a photodiode and multiple transistors. In these devices, the photodiode is the photosensitive unit, responsible for collecting and converting light, while the other MOS transistors act as control units, controlling the selection, reset, and signal readout of the photodiode.

[0004] Some CMOS image sensors requiring nighttime imaging also have high requirements for near-infrared imaging quality. CMOS image sensors use silicon as the material for photoelectric conversion. Silicon has good light absorption capabilities in the visible light range. In the near-infrared range, silicon's absorption capability is weak and it cannot absorb all light, which may produce crosstalk or glare. This crosstalk or glare can affect a very large area, reducing image quality and contrast. Utility Model Content

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this utility model is to provide an image sensor and electronic device to solve the problem of serious crosstalk or glare in the existing CMOS image sensor.

[0006] The objective of this utility model is achieved through the following technical solution: This invention provides an image sensor, comprising a semiconductor structure layer and an optical structure layer stacked on top of each other. The semiconductor structure layer contains a plurality of photosensitive units arranged in an array and a channel isolation structure formed by multiple intersecting isolation strips to form a grid structure. The channel isolation structure separates the plurality of photosensitive units from each other. The optical structure layer includes a grid structure formed by multiple intersecting grid strips to form a grid structure. The projection of the grid structure on the semiconductor structure layer completely covers the channel isolation structure, and at any position, the width of the grid strips is greater than the width of the isolation strips.

[0007] Furthermore, the projection of at least one of the opposite edges of the grid strip onto the semiconductor structure layer extends beyond the edge of the isolation strip.

[0008] Furthermore, the projection of any edge of the grid strip onto the semiconductor structure layer extends beyond the edge of the isolation strip.

[0009] Furthermore, the grid structure has multiple arrayed opening regions, each corresponding to a photosensitive unit.

[0010] Furthermore, the area of ​​the opening region is smaller than the area of ​​the photosensitive unit.

[0011] Furthermore, the opening area has a polygonal structure.

[0012] Furthermore, the opening area includes a rectangular structure, a hexagonal structure, or an octagonal structure.

[0013] Furthermore, the opening area has a circular structure.

[0014] Furthermore, the grid structure includes a first anti-reflective layer, a light-shielding layer, and a second anti-reflective layer stacked on top of each other, with the light-shielding layer disposed between the first anti-reflective layer and the second anti-reflective layer.

[0015] Furthermore, a first dielectric layer is provided between the light-shielding layer and the second anti-reflective layer, and the first dielectric layer is in contact with both the light-shielding layer and the second anti-reflective layer, or the first dielectric layer extends to cover the sidewalls of the light-shielding layer and the first anti-reflective layer.

[0016] Furthermore, the second antireflective layer also has a second dielectric layer in contact with it, or the surface of the second antireflective layer also has a protective layer.

[0017] Furthermore, the first anti-reflective layer includes a titanium layer, the second anti-reflective layer includes a titanium layer, the light-shielding layer includes a titanium nitride layer and a tungsten layer disposed from bottom to top, and both the first dielectric layer and the second dielectric layer include a silicon oxide layer.

[0018] Furthermore, the thickness of the first dielectric layer is between 100nm and 200nm; and / or, the thickness of the second dielectric layer is between 100nm and 300nm; and / or, the thickness of the second antireflective layer (513) is between 5nm and 30nm.

[0019] Furthermore, the reflectivity of the second anti-reflection layer is lower than that of the upper material layer of the light-shielding layer.

[0020] Furthermore, when a second dielectric layer is present, the second dielectric layer at least covers the sidewall of the second antireflective layer or extends to cover the sidewall of the light-shielding layer and the first antireflective layer.

[0021] Furthermore, the center of the opening area of ​​the grid structure and the center of the corresponding photosensitive unit have a misaligned configuration spacing, and the misaligned configuration spacing is positively correlated with the principal light angle corresponding to the corresponding pixel unit. Alternatively, the center of the opening area of ​​the grid structure coincides with the center of the corresponding photosensitive unit, and the area of ​​the opening area of ​​the grid structure is positively correlated with the principal light angle corresponding to the corresponding pixel unit.

[0022] Furthermore, the second anti-reflective layer at least covers the light-shielding layer.

[0023] Furthermore, the width of the first anti-reflective layer is smaller than the width of the second anti-reflective layer, and both sides of the second anti-reflective layer extend beyond the edge of the first anti-reflective layer at the corresponding positions.

[0024] Furthermore, the thickness of the semiconductor structure layer is between 2.5 μm and 6 μm.

[0025] This utility model also provides a method for fabricating an image sensor, applicable to the image sensor described in any of the above embodiments, wherein the grid structure includes a first anti-reflection layer, a light-shielding layer, and a second anti-reflection layer stacked on top of each other, and the fabrication method includes the following steps: A substrate is provided, and a photosensitive unit is fabricated on a first surface of the substrate; Flipping the substrate and fabricating an optical structure layer on the second surface of the substrate, comprising: The substrate is etched to form patterned trenches, and a channel isolation structure is prepared within the trenches; A first anti-reflective layer and a light-shielding layer are covered on the entire surface of the substrate side forming the channel isolation structure. The first anti-reflective layer and the light-shielding layer are etched to form a pattern corresponding to the grid structure. The first dielectric layer covers an entire surface and forms at least a pattern corresponding to the grid structure; A second antireflective layer is prepared on the first dielectric layer; A second dielectric layer is covered over the entire surface of the structure forming the second anti-reflective layer, and the second dielectric layer is etched to form a pattern corresponding to the grid structure. Wherein, the second dielectric layer and the first dielectric layer form a continuous dielectric layer; Alternatively, the substrate can be flipped over, and an optical structure layer can be fabricated on a second surface of the substrate, including: A first anti-reflective layer, a light-shielding layer, a first dielectric layer, and a second anti-reflective layer are covered on the base side of the channel isolation structure, forming a pattern corresponding to the grid structure. A second dielectric layer is applied to cover the entire surface of the material. The second dielectric layer is etched to form a pattern corresponding to the grid structure. The second dielectric layer at least covers the sidewalls of the second antireflective layer or extends to cover the sidewalls of the light-shielding layer and the first antireflective layer.

[0026] Furthermore, the preparation method further includes the following steps: After the trench isolation structure is prepared in the trench, a flat layer covering the trench isolation structure is also formed on the substrate surface. The first anti-reflective layer, the light-shielding layer, the first dielectric layer, the second anti-reflective layer and the second dielectric layer are all prepared based on the flat layer.

[0027] Furthermore, after forming the second anti-reflective layer, a protective layer is formed on the surface of the second pit reflective layer, and a pattern corresponding to the grid structure is formed based on the protective layer.

[0028] This application also provides an electronic device, including the image sensor described above.

[0029] The beneficial effects of this invention are as follows: by setting the width of the grid strips to be greater than the width of the isolation strips, on the one hand, some of the reflected light from the metal layer below the photosensitive unit can be blocked by the grid structure, and on the other hand, large-angle reflected light reflected back from the lens group or other optical elements can also be blocked by the grid structure and cannot re-enter the photosensitive unit, thereby improving the crosstalk and glare problems caused by near-infrared band reflected light and improving image contrast. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the optical path of an image sensor in the prior art.

[0031] Figure 2 This is a schematic diagram of the planar structure of an image sensor in the prior art.

[0032] Figure 3 This is a schematic diagram of the basic structure of an image sensor system.

[0033] Figure 4 This is a schematic diagram of the pixel circuit of an image sensor.

[0034] Figure 5 This is a schematic diagram of the image sensor structure in this utility model.

[0035] Figure 6 This is a schematic diagram of the cross-sectional structure of the grid strip in this utility model.

[0036] Figure 7 This is a schematic diagram of the planar structure of the channel isolation structure in this utility model.

[0037] Figure 8 This is one of the planar structural schematic diagrams of the grid structure in this utility model.

[0038] Figure 9 This is the second schematic diagram of the planar structure of the grid structure in this utility model.

[0039] Figure 10 This is the third schematic diagram of the planar structure of the grid structure in this utility model.

[0040] Figure 11 This is a schematic diagram of the optical path of the image sensor in this utility model.

[0041] Figures 12a-12j This is a structural diagram of the image sensor manufacturing process. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by this utility model to achieve its intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation methods, structures, features, and effects of the image sensor and electronic device proposed according to this utility model: like Figure 1 and Figure 2 As shown, silicon has weak absorption in the near-infrared band and cannot absorb all of it. Therefore, when near-infrared light is incident on the PD (photodiode), it passes through the PD and reaches the metal layer 310 beneath it. After being reflected by the metal layer 310, it passes through the PD again and is transmitted through the surface of the microlens. Since there are lens groups or other optical elements in front of the CMOS image sensor, the light reflected by these metal layers 310 will undergo secondary reflection by the lens group or other optical elements and return to the other PDs of the CMOS image sensor. Figure 1The reflection path ①→② in the middle generates crosstalk or glare. This crosstalk or glare can affect a very large area and reduce image quality and contrast. Moreover, the CMOS image sensor has a grid structure 510 aligned with the channel isolation structure 420. The grid structure 510 is usually composed of metal and oxide layers and has a high reflectivity. That is, the grid structure 510 itself is also a strong reflection source, which will reflect the light that has been reflected twice by the lens group or other optical elements again. Some light will be reflected back and forth multiple times between the lens group or other optical elements and the grid structure 510. Figure 1 The reflection path (①→③→④) allows the light to enter more photodiodes (PDs) of the CMOS image sensor, making crosstalk or glare problems more serious.

[0043] Figure 3 This is a basic circuit diagram of an image sensor. (For example...) Figure 3 As shown, the image sensor 100 includes a readout circuit 104 and a control circuit 108 connected to the pixel array 102. A functional logic circuit 106 is connected to the readout circuit 104 to perform logic control on the reading of the pixel array. The readout circuit 104 and the control circuit 108 are connected to the status register 112 to realize the readout control of the pixel array 102. The pixel array 101 includes multiple pixel units arranged in rows (R1, R2, R3…Ry) and columns (C1, C2, C3…Cx). The pixel signals output by the pixel array 102 are output to the readout circuit 104 via the column lines.

[0044] In one embodiment, after each pixel unit acquires image data, the image data is read out by a readout circuit 104 specifying the readout mode in the status register 112, and then transmitted to the functional logic circuit 106. In specific applications, the readout circuit 104 may include an analog-to-digital converter (ADC) circuit, an amplifier circuit, and others. In some application embodiments, the status register 112 may include a programmed selection system to determine whether the readout system reads out in a rolling shutter mode or a global shutter mode. The functional logic circuit 106 may store only image data or image data applied or processed by image effects. In one application example, the readout circuit 104 may read out one row of image data at a time along the readout column lines, or it may read out image data in various other ways. The operation of the control circuit 108 can be determined by the current setting of the status register 112. For example, the control circuit 108 generates a shutter signal to control image acquisition. In some application examples, this shutter signal may be a global shutter signal that causes all pixels of the pixel array 102 to simultaneously acquire their image data through a single acquisition window. In some other applications, this shutter signal can be a rolling exposure signal, with each pixel row being read continuously through an acquisition window.

[0045] Figure 4 This is a schematic diagram of the pixel circuitry of an image sensor, which can show the connection diagram of a transistor in the image sensor. For example... Figure 4 As shown, each sensor pixel circuit 200 includes a light-sensing element 210 (e.g., a photodiode) and a pixel support circuit 211. The photodiode 210 may be a buried photodiode used in current image sensors. In one application example, the pixel support circuit 211 includes a reset transistor (RST) 220, a source follower (SF) transistor 225, and a row select transistor (RS) 230, connected to a transfer transistor (TX) 215 and the photodiode 210 as shown. In another application example, not shown, the pixel support circuit 211 includes a reset transistor 220, a source follower transistor 225, and a row select transistor 230 disposed on a circuit chip, connected to the photodiode 210 in another chip based on the transfer transistor 215. During operation, the photocharge generated by the light-sensing element 210 responds to incident light during exposure. The transfer transistor 215 is connected to a transfer signal that controls the transfer transistor 215 to transfer the charge accumulated in the photodiode 210 to the floating diffusion region (FD) 217. In one embodiment, the transfer transistor 215 may be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). A reset transistor 220 is connected between VDD and the floating diffusion region 217, responding to a reset signal RST to reset the sensor pixel circuitry 200 (e.g., discharging or charging the floating diffusion region 217 and photodiode 210 to the current voltage). The floating diffusion region 217 is connected to the gate of the source follower transistor 225. The source follower transistor 225 is connected between VDD and the row select transistor 230 to respond to and output the potential of the floating diffusion region FD 217. The row select transistor 230 is connected from the source follower transistor 225 to the pixel circuitry output to the readout column, or bit line 235, in response to a row select control signal.

[0046] Figure 5 This is a schematic diagram of the image sensor structure in this utility model. Figure 6 This is a schematic diagram of the cross-sectional structure of the grid strip in this utility model. Figure 7 This is a schematic diagram of the planar structure of the channel isolation structure in this utility model.

[0047] like Figures 5 to 7As shown, the image sensor provided by this utility model includes a semiconductor structure layer 400 and an optical structure layer 500 stacked on top of each other. The semiconductor structure layer 400 contains a plurality of photosensitive units 410 arranged in an array and a channel isolation structure 420 formed by multiple intersecting isolation strips to form a grid structure, which separates the multiple photosensitive units 410 (PDs). The optical structure layer 500 includes a grid structure 510 formed by multiple intersecting grid strips. The projection of the grid structure 510 onto the semiconductor structure layer 400 completely covers the channel isolation structure 420, and at any position, the width of the grid strips is greater than the width of the isolation strips. It should be noted that at any position, the width of the grid strips is greater than the width of the isolation strips; that is, in the longitudinal direction, at any given position, the width of the grid strips is greater than the width of the isolation strips. Figure 5 As shown, the width of the grid strip is 'a', and the width of the isolation strip is 'b', where a > b. For example, the value of b can be between 130nm and 180nm, and the value of a can be set according to the actual situation.

[0048] By setting the width of the grid strips to be greater than the width of the isolation strips, on the one hand, some of the reflected light from the metal layer 310 below the photosensitive unit 410 will be blocked by the grid structure 510. On the other hand, large-angle reflected light from the lens group or other optical elements will also be blocked by the grid structure 510 and will not be able to re-enter the photosensitive unit 410. This can improve the crosstalk and glare problems caused by near-infrared reflected light and improve image contrast.

[0049] In one implementation, such as Figure 6 As shown, the grid structure 510 includes a first anti-reflective layer 511, a light-shielding layer 512, and a second anti-reflective layer 513 stacked on top of each other, with the light-shielding layer 512 disposed between the first anti-reflective layer 511 and the second anti-reflective layer 513. By providing the first anti-reflective layer 511 and the second anti-reflective layer 513 on the upper and lower sides of the light-shielding layer 512 respectively, the reflectivity of light on the grid structure 510 can be reduced, thus meeting the requirement that the grid structure 510 can block reflected light without generating further reflection, thereby further reducing crosstalk and glare problems and improving image contrast. Optionally, the light-shielding layer 512 includes a TiN (titanium nitride) layer 512a and a W (tungsten) layer 512b, thereby having a better light-shielding effect.

[0050] The grid structure 510 includes a dielectric layer 514, wherein a first antireflective layer 511, a light-shielding layer 512, and a second antireflective layer 513 are all disposed within and enclosed by the dielectric layer 514. The second antireflective layer 513 has a certain gap with the light-shielding layer 512 and is filled by the dielectric layer 514. As an example, the reflectivity of the second antireflective layer 513 is lower than the reflectivity of the upper material layer of the light-shielding layer 512.

[0051] As an example, a first dielectric layer 514a is provided between the light-shielding layer 512 and the second anti-reflection layer 513. The first dielectric layer 514a is in contact with both the light-shielding layer 512 and the second anti-reflection layer 513. Furthermore, the first dielectric layer 514a extends to cover the sidewalls of the light-shielding layer 512 and the first anti-reflection layer 511.

[0052] As an example, the second antireflective layer 513 also has a second dielectric layer 514b in contact with it. Furthermore, the surface of the second antireflective layer 513 also has a protective layer (not shown in the figure). Alternatively, when the second dielectric layer 514b is present, the second dielectric layer 514b at least covers the sidewalls of the second antireflective layer 513 or extends to cover the light-shielding layer 512 and the sidewalls of the first antireflective layer 513.

[0053] As an example, the first anti-reflective layer 511 includes a titanium layer, the second anti-reflective layer 513 includes a titanium layer, the light-shielding layer 512 includes a titanium nitride layer and a tungsten layer disposed from bottom to top, and the first dielectric layer 514a and the second dielectric layer 514b both include a silicon oxide layer.

[0054] As an example, the thickness of the first dielectric layer is between 100nm and 200nm; the thickness of the second dielectric layer is between 100nm and 300nm; and the thickness of the second antireflective layer 513 is between 5nm and 30nm. For example, both the first antireflective layer 511 and the second antireflective layer 513 can be made of Ti (titanium) with low reflectivity, such as with a thickness of 7-10nm; the dielectric layer 514 can be made of SiO2 (silicon dioxide), such as corresponding to a thickness of 100-200nm for the second dielectric layer.

[0055] In the comparative example, the grid structure 510 is composed of metal and oxide layers, exhibiting high reflectivity. This means the grid structure 510 itself is a strong reflection source, reflecting light that has already been reflected twice by the lens assembly or other optical elements. Some light will reflect back and forth multiple times between the lens assembly / other optical elements and the grid structure 510. Based on the above design of this application, it is beneficial to suppress secondary reflection of light on the grid structure 510 and to meet the requirement of blocking reflected light without generating further reflection. For example, inserting a second anti-reflection layer 513, such as a Ti layer, will result in better anti-reflection effects. Through the interference effect of light, the light is strongly absorbed by the upper second anti-reflection layer 513 (Ti layer) and the lower light-shielding layer 512 (W layer), reducing reflection.

[0056] In one embodiment, the projection of at least one edge of the opposite two sides of the grid strip onto the semiconductor structure layer 400 extends beyond the edge of the isolation strip. For example, the projection of at least one edge of the left and right sides of the grid strip onto the semiconductor structure layer 400 extends beyond the edge of the isolation strip. In this embodiment, the projection of any edge of the grid strip onto the semiconductor structure layer 400 extends beyond the edge of the isolation strip, thereby giving the grid structure 510 a better light-shielding effect, better reducing crosstalk and glare problems, and improving image contrast.

[0057] As an example, the second antireflective layer 513 at least covers the light-shielding layer 512, which helps prevent light from above from passing through the second dielectric layer 514b and causing crosstalk. As an example, the width of the first antireflective layer 511 is smaller than the width of the second antireflective layer 513, and both sides of the second antireflective layer 513 extend beyond the edges of the corresponding first antireflective layer 511. Based on this example design, it is beneficial for light reflected from below the substrate to be reflected to the light-shielding layer 512, further improving crosstalk.

[0058] like Figure 7 As shown, the channel isolation structure 420 further has a plurality of arrayed openings 421, each opening 421 corresponding to a photosensitive unit 410. In order to enable the photosensitive unit 410 to have a better photosensitive effect, the openings 421 are formed into a square structure.

[0059] Figure 8 This is one of the planar structural schematic diagrams of the grid structure in this utility model. Figure 9 This is the second schematic diagram of the planar structure of the grid structure in this utility model. Figure 10 This is the third schematic diagram of the planar structure of the grid structure in this utility model. For example... Figures 8-10As shown, in this embodiment, the grid structure 510 has a plurality of arrayed opening areas 510a, each corresponding to a photosensitive unit 410. The area of ​​each opening area 510a is smaller than the area of ​​the photosensitive unit 410, so that the grid structure 510 has a better light-blocking effect. Optionally, the opening area 510a is a polygonal structure. The opening area 510a includes rectangular structures (…). Figure 8 ), hexagonal structure or octagonal structure ( Figure 9 In this design, the rectangular structure of the opening region 510a ensures a large aperture ratio for the pixels of the image sensor, while the hexagonal or octagonal structure of the opening region 510a provides better light-blocking effect for the grid structure 510. Of course, as... Figure 10 As shown, the opening area 510a can also be a circular structure, thereby improving the light-blocking effect of the grid structure 510. Specifically, the opening area 510a can be a hexagonal, octagonal, or circular structure, allowing the corners of the photosensitive unit 410 to be better blocked by the grid structure 510, while also matching the circularly symmetrical structure of the microlens 530.

[0060] In one implementation, the center of the opening area 510a of the grid structure is offset from the center of the corresponding photosensitive unit 410, and the offset distance is positively correlated with the principal angle CRA corresponding to the corresponding pixel unit. In another implementation, the center of the opening area 510a of the grid structure 510 coincides with the center of the corresponding photosensitive unit 410, and the area of ​​the opening area 510a of the grid structure 510 is positively correlated with the principal angle CRA corresponding to the corresponding pixel unit. This can further optimize the imaging effect.

[0061] Furthermore, the optical structure layer 500 includes a color filter 520 and a microlens 530. The color filter 520 covers the grid structure 510, and the microlens 530 covers the color filter 520. The color filter 520 includes green, blue, infrared, cyan, yellow, magenta, or no color, to collect visible light signals. The microlens 530 acts as a light-focusing element, allowing more light to enter the photosensitive unit 410, improving the sensitivity of the photosensitive unit 410 and enhancing the image imaging effect. A planarization layer 501 is also provided between the optical structure layer 500 and the semiconductor structure layer 400 to improve the flatness of the semiconductor structure layer 400, facilitating the fabrication of the grid structure 510, color filter 520, and microlens 530 on the semiconductor structure layer 400.

[0062] Furthermore, the image sensor includes a circuit connection layer 300, which is disposed on the side of the semiconductor structure layer 400 away from the optical structure layer 500. A metal layer 310 is disposed in the circuit connection layer 300. The metal layer 310 includes, for example, interconnection structures of output transistors (MTX), reset transistors (MRS), amplification transistors (MRD), and other circuit elements, which will not be described in detail here.

[0063] Figure 11 This is a schematic diagram of the optical path of the image sensor in this utility model. For example... Figure 11 In this application, the width of the grid strips is set to be greater than the width of the isolation strips, and the grid structure 510 includes a first anti-reflective layer 511, a light-shielding layer 512, and a second anti-reflective layer 513 stacked on top of each other. The wider grid structure 510 can block some reflected light from the metal layer 310 below the photosensitive unit 410, and also blocks large-angle reflected light from the lens assembly or other optical elements, preventing it from re-entering the photosensitive unit 410. This improves crosstalk and glare issues caused by near-infrared reflected light, thereby enhancing image contrast. The grid structure 510 with lower reflectivity suppresses secondary reflections of light on the grid structure 510 and meets the requirement of blocking reflected light without re-reflection, further reducing crosstalk and glare and improving image contrast. As an example, the thickness of the semiconductor structure layer is between 2.5 μm and 6 μm. Based on the design of this application, it is beneficial to improve the influence of near-infrared light in the design of thinner substrate structures.

[0064] Figures 12a-12j This is a structural diagram illustrating the image sensor manufacturing process. (Example) Figures 12a-12j As shown, the image sensor manufacturing process itself is as follows: like Figure 12a As shown, a substrate is provided. Specifically, the substrate can be any structure used in the field of image sensors to fabricate various functional areas of an image sensor, such as the photosensitive element and various control transistors of a CMOS image sensor fabricated on the substrate. The substrate can be a structure composed of a single layer of material, including but not limited to a silicon substrate, in which the components in each area are fabricated. The substrate can be monocrystalline silicon, monocrystalline germanium, polycrystalline silicon, amorphous silicon, or silicon-germanium compounds, etc.

[0065] Alternatively, the substrate can be a stacked structure consisting of two or more material layers, with each region fabricated within any desired layer. For example, the substrate may include a silicon substrate and an epitaxial layer (EPI) formed on the silicon substrate, with photosensitive elements and various control transistors fabricated in the epitaxial layer; a back-illuminated (BSI) image sensor can be fabricated based on this structure. Alternatively, the substrate can be silicon-on-insulator (SOI). Furthermore, the substrate can also have N-type or P-type doping structures to meet the functional requirements of the device.

[0066] In one example, the substrate has a first side and a second side opposite to each other. In an alternative example, the first side and the second side can be formed by opposite front and back sides of the substrate, such as the front and back sides of a silicon substrate. In other examples, the first side can also be formed by one surface of an epitaxial layer formed thereon, and the second side can be formed by another surface away from the epitaxial layer.

[0067] A circuit connection layer 300 is fabricated on the front side of the substrate. A metal layer 310 is disposed in the circuit connection layer 300. The metal layer 310 includes, for example, interconnection structures of input transistors (MTX), reset transistors (MRS), amplifying transistors (MRD), and other circuit elements, which will not be described in detail here. The circuit connection layer 300 can be fabricated using existing structures and processes, and interconnection of various transistors can be achieved based on the circuit connection layer 300.

[0068] Alternatively, the photosensitive unit 410 can be fabricated on the substrate. Specifically, the photosensitive unit 410 can be a pixel in a conventional image sensor chip. The photosensitive unit 410 can receive light signals and generate photoelectrons. In one example, the photosensitive unit 410 is a photodiode (PD), which can be a PPD (Pinned Photodiode Pixel) structure. Of course, the photosensitive unit 410 can also be other structures that can convert light signals into electrical signals.

[0069] In addition, the photosensitive unit 410 may also include other transistor structures, such as field-effect transistors electrically connected to the photodiode. For example, the photosensitive unit 410 may also include a transmission transistor TX with a transmission gate. In another example, a floating diffusion node FD is also formed in the photosensitive unit 410. Of course, other field-effect transistors may also be included, such as a reset transistor RST, a source follower transistor SF, and a row select transistor RS, to form pixel structures such as 3T, 4T, and 5T. In this embodiment, all the transistors mentioned above are N-type, but it is understood that they may also be P-type in other implementations. Furthermore, the number of photosensitive elements and the number and arrangement of internal transistors in the photosensitive unit 410 can be designed according to actual needs and are not excessively restricted here.

[0070] like Figures 12b-12j As shown, the substrate is flipped, and an optical structure layer 500 is fabricated on the substrate. The following describes each execution step and the structure obtained in each step: like Figure 12b As shown, the substrate is etched to form patterned trenches 401, the pattern of which corresponds to the pattern of the channel isolation structure 420.

[0071] like Figure 12c As shown, a channel isolation structure 420 is prepared within the trench 401. For example, an isolation material can be applied to an entire surface of the substrate and then ground to retain the isolation material within the trench 401, forming the channel isolation structure 420 (BDTI).

[0072] like Figure 12d As shown, a planarization layer 501 is applied to the entire surface of the substrate. The planarization layer 501 can be an oxide layer. A light-blocking material is applied to the entire surface of the substrate. The light-blocking material is etched to form a grid structure 510. The grid structure 510 includes a first anti-reflective layer 511, a light-blocking layer 512, a second anti-reflective layer 513, and a dielectric layer 514.

[0073] The specific manufacturing process of the grid structure 510 includes: like Figure 12e As shown, a first antireflective layer 511, a TiN (titanium nitride) layer 512a, and a W (tungsten) layer 512b are sequentially covered on the planarization layer 501. The first antireflective layer 511, the TiN (titanium nitride) layer 512a, and the W (tungsten) layer 512b are etched to form a pattern corresponding to the grid structure 510. The first antireflective layer 511, the TiN (titanium nitride) layer 512a, and the W (tungsten) layer 512b can be fabricated individually using a masking process. The first antireflective layer 511 can be made of Ti (titanium), which has a low reflectivity.

[0074] like Figure 12f As shown, a first dielectric layer 514a is covered on the planarization layer 501, and the first dielectric layer 514a is etched to form a pattern corresponding to the grid structure 510. Of course, it is also possible not to etch the first dielectric layer 514a, but this will increase the optical layer thickness of the image sensor.

[0075] like Figure 12g As shown, a second anti-reflective layer 513 is covered on the entire surface of the planarization layer 501, and the second anti-reflective layer 513 is etched to form a pattern corresponding to the grid structure 510. The second anti-reflective layer 513 can be made of Ti (titanium), which has a low reflectivity.

[0076] like Figure 12h As shown, a second dielectric layer 514b is applied across the entire surface of the planarization layer 501. The second dielectric layer 514b is etched to form a pattern corresponding to the grid structure 510. Alternatively, etching the second dielectric layer 514b may not be necessary, but this would increase the optical layer thickness of the image sensor. The first dielectric layer 514a and the second dielectric layer 514b together form the dielectric layer 514.

[0077] like Figures 12i-12j As shown, after the grid structure 510 is fabricated, a color filter 520 and a microlens 530 are then fabricated sequentially on the planarization layer 501. The color filter 520 can be fabricated using existing color filter fabrication processes, and the microlens 530 can be fabricated using existing microlens processes.

[0078] This embodiment also provides another method for fabricating an image sensor. Figure 12c Subsequently, during the formation of the grid structure 510, a first anti-reflective layer 511, a light-shielding layer 512, a first dielectric layer 514a, and a second anti-reflective layer 513 are covered on the substrate side of the channel isolation structure 420, forming a pattern corresponding to the grid structure 420. That is, after the first anti-reflective layer 511, the light-shielding layer 512, the first dielectric layer 514a, and the second anti-reflective layer 513 are formed in sequence, they are etched to form the pattern corresponding to the grid structure 510, and then a second dielectric layer 514b is covered. The second dielectric layer 514b is etched to form a pattern corresponding to the grid structure 510. The second dielectric layer 514b at least covers the sidewalls of the second anti-reflective layer 513, and also extends to cover the sidewalls of the light-shielding layer 512 and the first anti-reflective layer 511, which helps to simplify the process and save costs.

[0079] As an example, after forming the second anti-reflective layer 513, a protective layer is also formed, including but not limited to a titanium nitride layer, thereby etching the protective titanium nitride layer and the corresponding second anti-reflective layer 513, first dielectric layer 514a, light-shielding layer 512, and first anti-reflective layer 511 together to obtain the pattern corresponding to the grid structure 510. Then, the entire second dielectric layer 514b is formed and processed. The setting of the protective layer helps to prevent the second anti-reflective layer 513 from being oxidized.

[0080] This utility model also provides an electronic device, wherein the electronic device includes the pixel structure of an image sensor as described in any of the above embodiments. The electronic device may be a security camera device, an automotive electronic camera device, a mobile phone camera device, a drone, a machine vision device, or an existing camera, etc.

[0081] In this document, the directional terms such as up, down, left, right, front, and back are defined according to the position of the structures in the accompanying drawings and the relative positions of the structures, and are only used for clarity and convenience in expressing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application. It should also be understood that the terms "first" and "second," etc., used herein are only used for distinction in name and are not used to limit the number or order.

[0082] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content without departing from the scope of the technical solution of the present utility model. These are equivalent embodiments with equivalent changes. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the technical solution of the present utility model shall still fall within the protection scope of the technical solution of the present utility model.

Claims

1. An image sensor, characterized in that, The device includes a semiconductor structure layer and an optical structure layer stacked on top of each other. The semiconductor structure layer contains a plurality of photosensitive units arranged in an array and a channel isolation structure formed by multiple intersecting isolation strips to form a grid structure. The channel isolation structure separates the plurality of photosensitive units from each other. The optical structure layer includes a grid structure formed by multiple intersecting grid strips to form a grid structure. The projection of the grid structure on the semiconductor structure layer completely covers the channel isolation structure, and the width of the grid strips at any position is greater than the width of the isolation strips at the corresponding positions.

2. The image sensor according to claim 1, characterized in that, The projection of at least one of the opposite edges of the grid strip onto the semiconductor structure layer extends beyond the edge of the isolation strip.

3. The image sensor according to claim 2, characterized in that, The projection of any edge of the grid strip onto the semiconductor structure layer extends beyond the edge of the isolation strip.

4. The image sensor according to claim 1, characterized in that, The grid structure has multiple arrayed opening regions, each corresponding to a photosensitive unit.

5. The image sensor according to claim 4, characterized in that, The area of ​​the opening region is smaller than the area of ​​the photosensitive unit.

6. The image sensor according to claim 4, characterized in that, The opening area is a polygonal structure; and / or, the opening area is a circular structure.

7. The image sensor according to claim 6, characterized in that, When the opening area is a polygonal structure, the opening area includes a rectangular structure, a hexagonal structure, or an octagonal structure.

8. The image sensor according to any one of claims 1-7, characterized in that, The grid structure includes a first anti-reflective layer, a light-shielding layer, and a second anti-reflective layer stacked on top of each other, with the light-shielding layer disposed between the first anti-reflective layer and the second anti-reflective layer.

9. The image sensor according to claim 8, characterized in that, A first dielectric layer is provided between the light-shielding layer and the second anti-reflective layer. The first dielectric layer is in contact with both the light-shielding layer and the second anti-reflective layer, or the first dielectric layer extends to cover the sidewalls of the light-shielding layer and the first anti-reflective layer; and / or, the second anti-reflective layer is further provided with a second dielectric layer in contact with it, or the surface of the second anti-reflective layer is further provided with a protective layer; and / or, the first anti-reflective layer includes a titanium layer, the second anti-reflective layer includes a titanium layer, the light-shielding layer includes a titanium nitride layer and a tungsten layer disposed from bottom to top, and both the first dielectric layer and the second dielectric layer include a silicon oxide layer.

10. The image sensor according to claim 9, characterized in that, The thickness of the first dielectric layer is between 100nm and 200nm; and / or, the thickness of the second dielectric layer is between 100nm and 300nm; and / or, the thickness of the second antireflective layer is between 5nm and 30nm; and / or, the reflectivity of the second antireflective layer is lower than the reflectivity of the upper material layer of the light-shielding layer; and / or, when a second dielectric layer is present, the second dielectric layer at least covers the sidewall of the second antireflective layer or extends to cover the sidewall of the light-shielding layer and the first antireflective layer.

11. The image sensor according to claim 8, characterized in that, The center of the opening area of ​​the grid structure is misaligned with the center of the corresponding photosensitive unit. The misalignment spacing is positively correlated with the principal light angle corresponding to the corresponding pixel unit. Alternatively, the center of the opening area of ​​the grid structure coincides with the center of the corresponding photosensitive unit, and the area of ​​the opening area of ​​the grid structure is positively correlated with the principal light angle corresponding to the corresponding pixel unit.

12. The image sensor according to claim 8, characterized in that, The second antireflective layer at least covers the light-shielding layer; and / or, the width of the first antireflective layer is smaller than the width of the second antireflective layer and both sides of the second antireflective layer extend beyond the edge of the first antireflective layer at the corresponding position; and / or, the thickness of the semiconductor structure layer is between 2.5 μm and 6 μm.

13. An electronic device, characterized in that, Including the image sensor as described in any one of claims 1-12.

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