Image sensor and preparation method thereof

Abstract

The invention discloses an image sensor and a preparation method thereof, and relates to the technical field of image sensors, a pixel region of the image sensor comprises a plurality of pixel structures, and a first organic layer and an anti-reflection layer stacked above the plurality of pixel structures; the non-pixel area comprises a plurality of bonding pad structures; a first lamination layer composed of the first organic layer and the anti-reflection layer extends from the pixel area to the non-pixel area and exposes the bonding pad structure, and one side close to the bonding pad structure is provided with a first side wall; the second organic layer is arranged on the anti-reflection layer of the non-pixel area, and the second organic layer at least extends from the first side wall to the direction of the pixel area, so that the anti-reflection layer with a certain length from the section of the opening of the bonding pad to the direction of the pixel area is clamped by the second organic layer and the first organic layer to form a sandwich structure; an effect similar to an explosion-proof glass film is generated, the anti-reflection layer at the fracture surface of the bonding pad opening is prevented from being broken and scattered, the defect risk is reduced, and the device yield is improved.

Description

Technical Field

[0001] This application relates to the field of image sensor technology, and in particular to an image sensor and its fabrication method. Background Technology

[0002] An image sensor is a device that uses the photoelectric conversion function of optoelectronic devices to convert a light image on a photosensitive surface into an electrical signal proportional to the light image. An image sensor consists of a pixel area and a non-pixel area. The pixel area is the region of the image sensor used to capture light signals and convert them into electrical signals. The non-pixel area is the part of the image sensor other than the pixel area, mainly including readout circuits, control circuits, power supply circuits, auxiliary circuits, and protection structures. Through complex circuit structures and control logic, the non-pixel area achieves precise control and signal readout of the pixel area.

[0003] Figure 1 A cross-sectional schematic diagram of an existing image sensor is shown. (Reference) Figure 1 As shown, to improve the quantum efficiency of image sensors, microlenses are typically formed on each color filter pixel. These microlenses are usually made of resin-based materials with a refractive index of around 1.6. However, incident light is reflected at the interface between the air and the microlens, which reduces the quantum efficiency of the image sensor. Therefore, a layer of silicon dioxide, called an anti-reflective coating (ARC), is usually formed on the surface of the microlenses as an anti-reflective layer. This ARC has a refractive index of approximately 1.46, and its thickness is about 1 / 4 wavelength of the incident light in silicon dioxide. This creates a 1 / 2 wavelength (180°) phase difference between the reflected light from the upper and lower surfaces of the silicon dioxide anti-reflective layer. The reflected light from the upper and lower surfaces cancels each other out, reducing the amount of reflected light and achieving the anti-reflective effect. In terms of the manufacturing process, after the microlens process is completed, a layer of silicon dioxide is deposited on the entire surface of the wafer using a low-temperature plasma-enhanced chemical vapor deposition (PECVD) process, with the thickness controlled to the designed value to form the anti-reflective layer.

[0004] After the anti-reflective layer of the image sensor is deposited, the pad area needs to be reopened to allow subsequent packaging processes to fabricate wires on the metal pads. Therefore, it is necessary to remove the various organic and anti-reflective layers deposited in the pad area throughout the entire process. This is typically done by performing a photolithography step to expose the pads and surrounding area, protecting the pixel area, followed by a dry etching process. Specifically, the surface silicon dioxide anti-reflective layer is first etched away with a fluorine-containing gas, and then the underlying organic layer is etched away with oxygen. During this process, due to the significant difference in etching rates between oxygen and silicon dioxide and organic materials, the silicon dioxide anti-reflective layer at the pad opening is hollowed out (i.e., an undercut is formed), leaving the silicon dioxide anti-reflective layer suspended at the pad opening with a width of approximately 0.5μm-1μm. Figure 2 The area shown is within the dashed elliptical box.

[0005] We know that there is no need for the silicon dioxide anti-reflective layer in the non-pixel area. On the contrary, due to the presence of the undercut, the suspended anti-reflective layer near the pad opening is easily subjected to physical impact and breaks during subsequent cleaning or chip cutting. The broken fragments may fly into the pixel area, forming pixel defects and causing yield loss. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides an image sensor and its fabrication method to solve the problem of anti-reflective layer breakage and scattering at the cross-section of the image sensor pad opening.

[0007] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0008] An image sensor includes a pixel region and a non-pixel region located around the pixel region;

[0009] The pixel region includes multiple pixel structures, and a first organic layer and an anti-reflective layer sequentially stacked on top of the multiple pixel structures;

[0010] The non-pixel area includes multiple pad structures. The first organic layer and the anti-reflective layer form a first stack. The first stack extends from the pixel area to the non-pixel area and exposes the pad structures. The first stack has a first sidewall on the side close to the pad structures.

[0011] The non-pixel area further includes a second organic layer, which is located on the side of the anti-reflective layer opposite to the first organic layer, and the second organic layer extends at least from the first sidewall toward the pixel area.

[0012] Optionally, the second organic layer also covers the first sidewall and extends from the first sidewall toward the pad structure.

[0013] Optionally, at least one anti-overflow trench is provided between the second organic layer and the pixel area.

[0014] Optionally, the first stack includes a plurality of first protrusions in the non-pixel area, and the anti-overflow groove is formed between adjacent first protrusions.

[0015] Optionally, the first stack near the first sidewall includes at least one second protrusion, with the second organic layer located above the second protrusion.

[0016] Optionally, the second organic layer extends from the first sidewall toward the pixel region for a length of not less than 10 μm.

[0017] Optionally, the distance between the second organic layer and the pixel region is not less than 2 μm, and the distance between the second organic layer and the pad structure is not less than 2 μm.

[0018] A method for fabricating an image sensor, comprising:

[0019] A substrate is provided, the substrate including a pixel region and a non-pixel region, the pixel region including a plurality of pixel structures, and the non-pixel region including a plurality of pad structures;

[0020] A first stack is formed, the first stack comprising a first organic layer and an anti-reflective layer stacked sequentially, the first stack covering the pixel area and the non-pixel area;

[0021] The first stack located in the non-pixel region is etched to form a pad opening that exposes the pad structure; the first stack has a first sidewall on the side near the pad structure; a second organic layer is formed, the second organic layer being located above the first stack in the non-pixel region and extending at least from the first sidewall toward the pixel region.

[0022] Optionally, forming the second organic layer includes: after etching to form the pad openings, forming the second organic layer over the first stack using an inkjet printing process, a screen printing process, or a nanoimprinting process.

[0023] Optionally, forming the second organic layer includes:

[0024] An initial photoresist layer is formed above the anti-reflective layer, and the initial photoresist layer is patterned to form a first opening that exposes the first stack above the pad structure. Simultaneously, a first photoresist layer is formed in the pixel area and a portion of the non-pixel area near the pixel area, and a second photoresist layer is formed in the non-pixel area near the pad structure. The thickness of the second photoresist layer is greater than the thickness of the first photoresist layer.

[0025] The first stack exposed by the first opening is etched away to form the pad opening. The first photoresist layer and the second photoresist layer are etched simultaneously. The first photoresist layer is completely removed, and the remaining second photoresist layer forms the second organic layer.

[0026] Optionally, the initial photoresist layer is a positive photoresist layer, and patterning the initial photoresist layer includes:

[0027] The initial photoresist layer is exposed and developed using a first photomask. The first photomask includes a first region, a second region, and a third region. The transmittance of the second region is less than that of the first region, and the transmittance of the first region is less than that of the third region. The first region corresponds to the formation of the first photoresist layer, the second region corresponds to the formation of the second photoresist layer, and the third region corresponds to the formation of the first opening.

[0028] Optionally, the initial photoresist layer is a positive photoresist layer, and patterning the initial photoresist layer includes:

[0029] The initial photoresist layer is exposed and developed using a second photomask. The second photomask includes a first pattern, a second pattern, and a third pattern. The duty cycle of the first pattern is smaller than that of the second pattern, and the third pattern is a fully exposed area. The first pattern corresponds to the formation of multiple spaced first photoresist structures, the second pattern corresponds to the formation of multiple spaced second photoresist structures, and the third pattern corresponds to the formation of the first opening.

[0030] Heating causes the first photoresist structure to melt and form the first photoresist layer, and causes the second photoresist structure to melt and form the second photoresist layer.

[0031] Optionally, the distance between adjacent second photoresist structures is less than the distance between adjacent first photoresist structures.

[0032] Optionally, along the direction from the pixel area to the non-pixel area, the width of the second photoresist structure is greater than the width of the second photoresist structure.

[0033] Optionally, the first organic layer located above the pixel area includes a microlens. When etching the first organic layer to form the microlens, the portion of the first organic layer in the non-pixel area is simultaneously etched to form at least one first trench. The first trench after forming the anti-reflective layer constitutes an anti-overflow trench located between the second organic layer and the pixel area.

[0034] Optionally, the first organic layer located above the pixel area includes a microlens. When etching the first organic layer to form the microlens, at least one redundant microlens is formed by simultaneously etching the portion of the first organic layer near the pad structure in the non-pixel area. The second organic layer is formed above the redundant microlens.

[0035] Compared with existing technologies, the above technical solution has the following advantages:

[0036] The image sensor provided in this application embodiment includes a pixel region and a non-pixel region located around the pixel region. The pixel region includes multiple pixel structures, and a first organic layer and an anti-reflective layer are sequentially stacked on top of the multiple pixel structures. The non-pixel region includes multiple pad structures. A first stack composed of the first organic layer and the anti-reflective layer extends from the pixel region to the non-pixel region and exposes the pad structures, i.e., the first stack has pad openings. The side of the first stack near the pad structures, i.e., at the cross-section of the pad opening, has a first sidewall. A second organic layer is provided on the side of the anti-reflective layer in the non-pixel region away from the first organic layer. Furthermore, the second organic layer extends at least from the first sidewall toward the pixel area, such that a section of the anti-reflective layer from the pad opening to the pixel area is sandwiched between the second organic layer and the first organic layer, forming a sandwich structure. This prevents the anti-reflective layer at the pad opening from breaking and scattering. Even if there is a local breakage in the anti-reflective layer at the pad opening, the presence of the second organic layer on the surface of the anti-reflective layer at the pad opening creates an effect similar to a shatterproof glass film, thereby preventing the anti-reflective layer at the pad opening from scattering arbitrarily, reducing defect risk, and improving device yield. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic cross-sectional view of an existing image sensor without pad openings.

[0039] Figure 2 This is a schematic diagram of the cross-sectional structure of an existing image sensor after the pads have been opened.

[0040] Figure 3 This is a schematic cross-sectional view of an image sensor provided in an embodiment of this application.

[0041] Figure 4 This is a cross-sectional structural diagram of another image sensor provided in an embodiment of this application;

[0042] Figures 5a-5e This is a schematic diagram of some process steps in a method for fabricating an image sensor provided in an embodiment of this application.

[0043] Figures 6a-6b This is a schematic diagram of some process steps in another method for fabricating an image sensor provided in this application embodiment.

[0044] Figure 7 This is a schematic diagram of some process steps in a method for fabricating an image sensor according to an embodiment of this application.

[0045] Figures 8a-8b This is a schematic diagram of some process steps in another method for fabricating an image sensor provided in this application embodiment.

[0046] Figure label:

[0047] 100 - Pixel area; 200 - Non-pixel area; 10 - Color filter pixel structure; 11 - Isolation trench; 20 - First organic layer; 21 - Microlens; 22 - Redundant microlens; 30 - Anti-reflection layer; 300 - First stacked layer; 40 - Second organic layer; 210 - Pad area; 211 - Pad structure; 212 - Pad protection layer; 410 - Initial photoresist layer; 41 - Photoresist layer with first opening; 411 - First photoresist layer; 412 - Second photoresist layer; 42 - First photomask; 4 21-First region; 422-Second region; 423-Third region; 43-Second photomask; 431-First pattern; 432-Second pattern; 433-Third pattern; C1-First sidewall; K1-Pad opening; T1-Anti-overflow trench; S1-First trench; Q1-First protrusion; Q2-Second protrusion; Z1-First opening; R1-First photoresist structure; R2-Second photoresist structure; 50-Circuit board; 60-Pixel board; 70-Back metal layer; 80-Light shielding layer. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0050] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0051] As described in the background section, there is no need for the silicon dioxide anti-reflective layer in the non-pixel area. On the contrary, due to the presence of the undercut, the suspended anti-reflective layer near the pad opening is easily subjected to physical impact and breaks during subsequent cleaning or chip cutting. The broken fragments may fly into the pixel area, forming pixel defects and causing yield loss.

[0052] The inventors learned that the industry was fully aware of this risk, and that to completely avoid it, either the anti-reflective layer in the non-pixel areas would be removed in advance, or the cross-section of the pad openings would be sealed again with photoresist. Either approach would require at least one additional photolithography step, thus increasing costs.

[0053] This application aims to solve the problem of anti-reflective layer breakage and scattering at the cross-section of the pad opening of the image sensor, minimizing the risk without significantly increasing the cost.

[0054] Figure 3 and Figure 4 The following are schematic cross-sectional views of two image sensors provided in embodiments of this application, as shown in the figure. Figure 3 and Figure 4 As shown, the image sensor provided in this application embodiment includes a pixel area 100 and a non-pixel area 200 located around the pixel area 100;

[0055] The pixel area 100 includes multiple color filter pixel structures 10, and a first organic layer 20 and an anti-reflection layer 30 are stacked sequentially on top of the multiple color filter pixel structures 10. There may be an isolation groove 11 between adjacent color filter pixel structures 10. The first organic layer 20 includes multiple microlenses 21, and the microlenses 21 correspond one-to-one with the color filter pixel structures 10.

[0056] The non-pixel area 200 includes multiple pad areas 210, each pad area 210 having a pad structure 211. The first organic layer 20 and the anti-reflective layer 30 form a first stack 300. The first stack 300 extends from the pixel area 100 to the non-pixel area 200 and exposes the pad structure 211. That is, the first stack 300 composed of the first organic layer 20 and the anti-reflective layer 30 has a pad opening K1, and the pad opening K1 exposes the pad structure 211. The first stack 300 has a first sidewall C1 on the side near the pad structure 211, i.e. at the cross-section of the pad opening K1.

[0057] The non-pixel area 200 also includes a second organic layer 40 located on the side of the anti-reflective layer 30 away from the first organic layer 20. The second organic layer 40 extends at least a distance from the first sidewall C1 toward the pixel area 100. There is a distance between the second organic layer 40 and the pixel area 100, and between the second organic layer 40 and the pad structure 211.

[0058] Understandably, the pixel structure in pixel area 100 is used to capture light signals and convert them into electrical signals. The non-pixel area 200 contains auxiliary circuits such as readout circuits, control circuits, and power supply circuits. Through complex circuit structures and control logic, precise control and signal readout of the multiple pixel structures in pixel area 100 are achieved. Therefore, the non-pixel area 200 includes a pad area 210, which has pad structures 211 to facilitate electrical connections via wire bonding on the metal pads during the packaging process.

[0059] Optionally, the first organic layer 20 can be an organic resin layer.

[0060] Optionally, the anti-reflective layer 30 can be a silicon dioxide layer.

[0061] Optionally, the second organic layer 40 and the first organic layer 20 can be made of the same material or different materials; for example, the material of the second organic layer 40 can be an organic material such as acrylic resin or epoxy resin.

[0062] In this embodiment, the second organic layer 40 extends at least a distance from the first sidewall C1 toward the pixel region 100, including:

[0063] like Figure 4 As shown, the second organic layer 40 extends only a short distance from the first sidewall C1 toward the pixel region 100;

[0064] Or, such as Figure 3 As shown, the second organic layer 40 not only extends a distance from the first sidewall C1 toward the pixel area 100, but also covers the first sidewall C1 and extends a distance from the first sidewall C1 toward the pad structure 211.

[0065] In this embodiment, the second organic layer 40 is spaced apart from the pixel region 100 to maintain a sufficient safe distance between them. Furthermore, the second organic layer 40 is also spaced apart from the pad structure 211 to maintain a sufficient safe distance between them.

[0066] Therefore, the image sensor provided in this application embodiment, by providing a second organic layer 40 on the side of the anti-reflective layer 30 in the non-pixel area 200 away from the first organic layer 20, and the second organic layer 40 extending at least a distance from the first sidewall C1 toward the pixel area 100, allows the anti-reflective layer 30 of a certain length from the pad opening section toward the pixel area 100 to be sandwiched between the second organic layer 40 and the first organic layer 20, forming a sandwich structure. In this way, the anti-reflective layer 30 at the pad opening section can be prevented from breaking and scattering. Even if there is a local breakage of the anti-reflective layer at the pad opening section, the second organic layer 40 on the surface of the anti-reflective layer 30 at the pad opening section forms an effect similar to an explosion-proof glass film, thereby preventing the anti-reflective layer 30 at the pad opening section from arbitrarily scattering, reducing the risk of defects, and improving the device yield.

[0067] It is understandable that when the second organic layer 40 not only extends a distance from the first sidewall C1 toward the pixel region 100, but also covers the first sidewall C1, and extends a distance from the first sidewall C1 toward the pad structure 211, such as Figure 3 As shown, this not only sandwiches the anti-reflective layer 30, which extends from the pad opening section toward the pixel area 100, with the second organic layer 40 and the first organic layer 20, forming a sandwich structure, but also completely encapsulates the entire pad opening section with the second organic layer 40. This prevents subsequent processes such as water washing from attacking the pad opening section, thus better preventing the anti-reflective layer 30 at the pad opening section from breaking and scattering, further reducing defect risks and improving device yield.

[0068] To form a second organic layer 40 on the side of the anti-reflective layer 30 in the non-pixel region 200 away from the first organic layer 20, and to ensure that the second organic layer 40 not only extends a distance from the first sidewall C1 toward the pixel region 100, but also covers the first sidewall C1, and extends a distance from the first sidewall C1 toward the pad structure 211, one option is to add a photolithography process, although this would increase costs. Another option is to consider that a sufficient safe distance needs to be maintained between the second organic layer 40 and the pixel region 100, and between the second organic layer 40 and the pad structure 211. Therefore, the precision requirements for the location of the second organic layer 40 and the length of its extension toward the pixel region 100 are not so high. For example, the length of the second organic layer 40 extending toward the pixel region 100 can be relatively long. Therefore, a photolithography process can be omitted, and another method can be used, specifically inkjet printing, screen printing, or nanoimprinting to form the second organic layer 40. Inkjet printing, screen printing, and nanoimprinting are all relatively inexpensive.

[0069] It should be noted that when the second organic layer 40 extends only a certain distance from the first sidewall C1 towards the pixel region 100, such as Figure 4 As shown, although the pad opening section is not completely covered by the second organic layer 40, the second organic layer 40 extends a distance from the first sidewall C1 toward the pixel area 100, so that the anti-reflective layer 30 of a certain length from the pad opening section toward the pixel area 100 is sandwiched between the second organic layer 40 and the first organic layer 20, forming a sandwich structure. This produces an effect similar to that of a shatterproof glass film, which can also prevent the anti-reflective layer 30 at the pad opening section from scattering arbitrarily, reducing the risk of defects and improving the device yield.

[0070] In order to form a second organic layer 40 on the side of the anti-reflection layer 30 in the non-pixel area 200 away from the first organic layer 20, and the second organic layer 40 extends only a distance from the first sidewall C1 toward the pixel area 100, one option is to add a photolithography process, but this will increase the cost relatively.

[0071] Alternatively, considering the photolithography process involved in opening the pad area, a photoresist layer is first applied to the entire surface. Then, a photoresist pattern is formed in the pixel area 100 and the non-pixel area 200 near the pixel area 100. This pattern serves as a sacrificial layer for the anti-reflective layer 30 and the first organic layer 20 corresponding to the pad opening during dry etching. This protects the various film layers in the pixel area 100 and the non-pixel area 200 near the pixel area 100 from being eroded by the dry etching process. Finally, the photoresist layer is removed using a solvent-based wet cleaning method. The anti-reflective layer 30 is typically a silicon dioxide layer, dry-etched using a fluorine-containing gas, and the first organic layer 20 is typically an organic resin layer, dry-etched using oxygen. For existing image sensors, silicon dioxide anti-reflective layers are commonly used as the final surface material for the pixel area, providing sufficient tolerance for dry etching using oxygen as the etching gas. In other words, when dry etching is performed on the anti-reflection layer 30 corresponding to the pad opening, the anti-reflection layer 30 outside the pad opening needs to be protected from etching. However, when dry etching is performed on the first organic layer 20 corresponding to the pad opening, the first organic layer 20 outside the pad opening has an anti-reflection layer 30 made of silicon dioxide on its surface. Even if sufficient over-etching is maintained, the anti-reflection layer 30 can ensure that the pixel area structure of the first organic layer 20 and other components is not damaged.

[0072] In this way, the photoresist pattern can be controlled to have different thicknesses in the areas where the second organic layer is pre-formed in non-pixel areas and in other protected areas, including the pixel area, based on the first organic layer and anti-reflection layer corresponding to the exposed pad opening. Specifically, the photoresist layer thickness in the areas where the second organic layer is pre-formed in non-pixel areas is greater than the photoresist layer thickness in other protected areas, including the pixel area. Thus, after the dry etching of the pad area is completed, the thinner photoresist layer covering the pixel area and part of the non-pixel area can be completely removed, while a certain thickness of photoresist layer is retained in the areas where the second organic layer is pre-formed in non-pixel areas. This part of the photoresist layer can then serve as the second organic layer. Furthermore, during the process of opening the pad area, even with sufficient over-etching, the anti-reflection layer can ensure that the color filter film and microlens materials in the pixel area are not damaged. In this way, the pad area is fully opened, the photoresist layer on the pixel area is completely removed, and a second organic layer is formed. No new photolithography process is added, and the wet cleaning process of the photoresist layer can be omitted. It is only necessary to select a suitable photoresist material, design a suitable photomask, and adjust the appropriate coating and etching process parameters during the opening of the pad area, without increasing the cost.

[0073] It is understandable that when the second organic layer 40 and the first organic layer 20 are made of the same material, the first organic layer 20 and the second organic layer 40 satisfy the bonding force between the same materials, making the sandwich structure composed of the first organic layer 20-anti-reflective layer 30-second organic layer 40 more reliable.

[0074] Optionally, the second organic layer 40 extends from the first sidewall C1 toward the pixel area 100 for a length of not less than 10 μm. That is, the second organic layer 40 is not limited to the first sidewall C1, but extends a relatively long distance from the first sidewall C1 toward the pixel area 100. This allows the anti-reflective layer 30, which extends a long distance from the first sidewall C1 toward the pixel area 100, to be sandwiched between the first organic layer 20 and the second organic layer 40. In other words, the sandwich structure formed by the first organic layer 20, the anti-reflective layer 30, and the second organic layer 40 is not limited to the pad opening section, but has a relatively large stacked area. This makes the second organic layer 40 on the surface of the anti-reflective layer 30 have a better effect on the anti-reflective layer 30, similar to a shatterproof glass film. This further prevents the anti-reflective layer at the pad opening section from breaking and scattering, reduces the risk of defects, and improves the device yield.

[0075] As previously known, the second organic layer 40 and the pixel region 100 are separated by a distance, ensuring a sufficient safe distance between them. Optionally, the distance between the second organic layer 40 and the pixel region 100 is not less than 2 μm, i.e., greater than or equal to 2 μm. The second organic layer 40 and the pad structure 211 are also separated by a distance, ensuring a sufficient safe distance between them. Optionally, the distance between the second organic layer 40 and the pad region 210 is not less than 2 μm, i.e., greater than or equal to 2 μm.

[0076] To prevent the second organic layer 40 (e.g., during printing or imprinting) from diffusing into the pixel area 100 and affecting the color filter pixel structure 10 of the pixel area 100, optionally, such as Figure 3 and Figure 4 As shown, at least one anti-overflow trench T1 is provided between the second organic layer 40 and the pixel area 100. Thus, during the diffusion of the second organic layer 40 into the pixel area 100, the anti-overflow trench T1 needs to be filled first before it can move closer to the pixel area 100, thereby blocking the diffusion of the second organic layer 40 into the pixel area 100.

[0077] It is understandable that the anti-overflow trench T1 is a groove structure. The greater its depth, the more the anti-overflow trench needs to be filled during the diffusion of the second organic layer 40 to the pixel area 100 before it can get closer to the pixel area. This results in a better effect on blocking the diffusion of the second organic layer 40 to the pixel area 100.

[0078] In addition, the more anti-overflow trenches T1 there are, the more anti-overflow trenches need to be filled during the diffusion of the second organic layer 40 to the pixel area 100 before it can get closer to the pixel area, thus improving the effect of blocking the diffusion of the second organic layer 40 to the pixel area 100.

[0079] Optional, such as Figure 3 and Figure 4 As shown, the first stack 300 composed of the first organic layer 20 and the anti-reflection layer 30 includes multiple first protrusions Q1 in the non-pixel area 200, and anti-overflow trenches T1 are formed between adjacent first protrusions Q1. Specifically, a microlens photolithography mask can be designed. When the first organic layer 20 is etched to form a microlens 21 using the designed microlens photolithography mask, at least one first trench S1 is simultaneously etched in a portion of the first organic layer 20 in the non-pixel area 200. Thus, the first trench S1 after the formation of the anti-reflection layer 30 constitutes the anti-overflow trench T1, and the anti-overflow trench T1 is located between the subsequently formed second organic layer 40 and the pixel area 100.

[0080] Optional, such as Figure 3 and Figure 4 As shown, the first stack 300 near the first sidewall C1 includes at least one second protrusion Q2. A portion of the first organic layer 20 within the second protrusion Q2 is a redundant microlens 22, with a structure similar to the microstructure 21. The second organic layer 40 is located above the second protrusion Q2. It is understood that the uneven surface of the second protrusion Q2 increases the contact area between the first organic layer 20 and the anti-reflective layer 30, and also increases the contact area between the redundant microlens 22 and the anti-reflective layer 30. This enhances the clamping effect of the first organic layer 20 and the second organic layer 40 on the pad opening section and the nearby anti-reflective layer 30, further preventing the anti-reflective layer at the pad opening section from breaking and scattering, reducing defect risk, and improving device yield.

[0081] like Figure 3 and Figure 4 As shown, the image sensor provided in this application embodiment also includes a circuit board 50, a pixel board 60, a back metal layer 70, a light-shielding layer 80, and other structures not shown, which will not be described in detail here.

[0082] Accordingly, this application also provides a method for fabricating an image sensor, the method comprising:

[0083] S100: As Figure 5aAs shown, a substrate is provided, the substrate including a pixel region 100 and a non-pixel region 200 located around the pixel region 100; the pixel region 100 includes a plurality of color filter pixel structures 10, and an isolation trench 11 may be provided between adjacent color filter pixel structures 10; the non-pixel region 200 includes a plurality of pad regions 210, and the pad regions 210 are provided with pad structures 211 and pad protective layers 212 covering the pad structures 211.

[0084] S200: such as Figure 5a As shown, a first stack 300 is formed, which includes a first organic layer 20 and an anti-reflective layer 30 stacked sequentially. The first stack 300 covers the pixel area 100 and the non-pixel area 200.

[0085] Specifically, a first organic layer 20 covering multiple color filter pixel structures 10 is first formed, and the first organic layer 20 is etched to make the first organic layer 20 include multiple microlenses 21, with each microlens 21 corresponding to a color filter pixel structure 10; then an anti-reflection layer 30 is formed on the side of the first organic layer 20 away from the multiple color filter pixel structures 10.

[0086] S300: such as Figure 3 and Figure 4 As shown, the first stack 300 located in the non-pixel region 200 is etched to form a pad opening K1 that exposes the pad structure 211; the first stack 300 has a first sidewall C1 on the side near the pad structure 211; a second organic layer 40 is formed, which is located above the first stack 300 in the non-pixel region 200 and extends at least from the first sidewall C1 toward the pixel region 100.

[0087] In other words, the anti-reflective layer 30 and the first organic layer 20 of the non-pixel area 200 are etched so that the first stack 300 composed of the first organic layer 20 and the anti-reflective layer 30 has a pad opening K1, and the pad opening K1 exposes the pad structure 211. The first stack 300 has a first sidewall C1 on the side close to the pad structure 211, that is, at the cross section of the pad opening K1. A second organic layer 40 is formed on the side of the anti-reflective layer 30 away from the first organic layer 20. The second organic layer 40 extends at least a distance from the first sidewall C1 toward the pixel area 100. There is a distance between the second organic layer 40 and the pixel area 100, and between the second organic layer 40 and the pad structure 211.

[0088] Through the above process steps, it is possible to form Figure 3 or Figure 4The image sensor shown is illustrated. As can be seen, the image sensor fabrication method provided in this application involves setting a second organic layer 40 on the side of the anti-reflective layer 30 in the non-pixel area 200 away from the first organic layer 20. The second organic layer 40 extends at least a distance from the first sidewall C1 towards the pixel area 100, such that a length of the anti-reflective layer 30 extending from the pad opening towards the pixel area is sandwiched between the second organic layer 40 and the first organic layer 20, forming a sandwich structure. This prevents the anti-reflective layer 30 at the pad opening from breaking and scattering. Even if there is localized breakage at the pad opening, the presence of the second organic layer 40 on the surface of the anti-reflective layer 30 at the pad opening creates an effect similar to a protective film on explosion-proof glass, thereby preventing the anti-reflective layer 30 at the pad opening from scattering arbitrarily, reducing defect risk, and improving device yield.

[0089] Based on the above embodiments, optionally, in step S300, the second organic layer 40 can be formed after etching the first stacked layer 300 in the non-pixel region 200 to form the pad opening K1. Specifically, in step S300, etching the first stacked layer 300 located in the non-pixel region 200 to form the pad opening K1 exposing the pad structure 211 includes:

[0090] S310: As Figure 5b As shown, an initial photoresist layer 410 is formed on the side of the antireflective layer 30 opposite to the first organic layer 20.

[0091] S311: As Figure 5c As shown, an initial photoresist layer 410 is patterned to form a photoresist layer 41 with a first opening Z1, the first opening Z1 exposing a first stack 300 located above the pad structure 211.

[0092] S312: As Figure 5d As shown, etching removes the first stack 300 exposed by the first opening Z1 to form the pad opening K1 of the exposed pad structure 211.

[0093] Specifically, using the photoresist layer 41 with the first opening Z1 as a mask, the anti-reflective layer 30 exposed by the first opening Z1 is etched to expose the first organic layer 20 located above the pad structure 211. Then, the first organic layer 20 exposed by the first opening Z1 is etched to make the first stack 300 composed of the first organic layer 20 and the anti-reflective layer 30 have a pad opening K1. The pad opening K1 exposes the pad structure 211 of the non-pixel area 200. The first stack 300 composed of the first organic layer 20 and the anti-reflective layer 30 has a first sidewall C1 on the side near the pad structure 211.

[0094] The anti-reflective layer 30 is typically a silicon dioxide layer, and the silicon dioxide anti-reflective layer 30 is dry-etched using a fluorine-containing gas; the first organic layer 20 is typically an organic resin layer, and the first organic layer 20 is dry-etched using oxygen.

[0095] S313: As Figure 5e As shown, the photoresist layer 41 is removed.

[0096] In practical applications, after the dry etching of the open pad area 210 is completed, the photoresist layer 41 can be removed by solvent-based wet cleaning.

[0097] It is understandable that the first opening Z1 of the photoresist layer 41 corresponds to the pad opening K1 of the first stack 300.

[0098] like Figures 5a-5c As shown, the pad structure 211 in the pad area 210 is covered by the pad protection layer 212. After the first stack 300 composed of the first organic layer 20 and the anti-reflection layer 30 has a pad opening K1 and the pad opening K1 exposes the pad area 210 of the non-pixel area 200, the pad protection layer 212 is removed to expose the pad structure 211.

[0099] Furthermore, in step S300, forming the second organic layer 40 includes:

[0100] S314: As Figure 3 As shown, a second organic layer 40 is formed on top of the first stack 300 using inkjet printing, screen printing, or nanoimprinting. The second organic layer 40 extends at least a distance from the first sidewall C1 toward the pixel area 100.

[0101] Considering that sufficient safe distances need to be maintained between the second organic layer 40 and the pixel region 100, and between the second organic layer 40 and the pad structure 211, the precision requirements for the location of the second organic layer 40 and the length of the second organic layer 40 extending into the pixel region 100 are not so high. For example, the length of the second organic layer 40 extending into the pixel region 100 can be relatively long. Therefore, inkjet printing, screen printing, or nanoimprinting can be used to form the second organic layer 40, thus eliminating the need for photolithography and reducing the cost of inkjet printing, screen printing, and nanoimprinting.

[0102] Moreover, steps S310-S314 can, without adding a photolithography process, allow the second organic layer 40 to not only extend a certain distance from the first sidewall C1 toward the pixel area 100, but also cover the first sidewall C1 and extend a certain distance from the first sidewall C1 toward the pad structure 211. In this way, not only is the anti-reflection layer 30 of a certain length from the pad opening section toward the pixel area 100 sandwiched between the second organic layer 40 and the first organic layer 20 to form a sandwich structure, but the entire section of the pad opening is completely wrapped by the second organic layer 40. This makes it impossible for subsequent processes such as water washing to attack the pad opening section, which is more effective in preventing the anti-reflection layer 30 at the pad opening section from breaking and scattering, further reducing the risk of defects and improving the device yield.

[0103] Of course, steps S310-S314 can also be performed without adding a photolithography process, so that the second organic layer 40 extends only a certain distance from the first sidewall C1 toward the pixel area 100.

[0104] As shown in steps S310-S313, a photolithography process is involved in opening the pad area 210. Specifically, a photoresist layer is first coated across the entire surface. Then, a photoresist pattern is formed in the pixel area 100 and the non-pixel area 200 near the pixel area 100. This pattern serves as a sacrificial layer for the anti-reflective layer 30 and the first organic layer 20 corresponding to the pad opening during dry etching. This protects the various film layers in the pixel area 100 and the non-pixel area 200 near the pixel area 100 from being eroded by the dry etching process. Finally, the photoresist layer is removed using a solvent-based wet cleaning method. The anti-reflective layer 30 is typically a silicon dioxide layer, etched using a fluorine-containing gas during dry etching. The first organic layer 20 is typically an organic resin layer, etched using oxygen during dry etching. For existing image sensors, silicon dioxide anti-reflective layers are commonly used as the final surface material for the pixel area, providing sufficient tolerance for dry etching using oxygen as the etching gas. In other words, when dry etching is performed on the anti-reflection layer 30 corresponding to the pad opening, the anti-reflection layer 30 outside the pad opening needs to be protected from etching. However, when dry etching is performed on the first organic layer 20 corresponding to the pad opening, the first organic layer 20 outside the pad opening has an anti-reflection layer 30 made of silicon dioxide on its surface. Even if sufficient over-etching is maintained, the anti-reflection layer 30 can ensure that the pixel area structure of the first organic layer 20 and other components is not damaged.

[0105] In this way, the photoresist pattern can be controlled to have different thicknesses in the areas where the second organic layer is pre-formed in non-pixel areas and in other protected areas, including the pixel area, based on the first organic layer and anti-reflection layer corresponding to the exposed pad opening. Specifically, the photoresist layer thickness in the areas where the second organic layer is pre-formed in non-pixel areas is greater than the photoresist layer thickness in other protected areas, including the pixel area. Thus, after the dry etching of the pad area is completed, the thinner photoresist layer covering the pixel area and part of the non-pixel area can be completely removed, while a certain thickness of photoresist layer is retained in the areas where the second organic layer is pre-formed in non-pixel areas. This part of the photoresist layer can then serve as the second organic layer. Furthermore, during the process of opening the pad area, even with sufficient over-etching, the anti-reflection layer can ensure that the color filter film and microlens materials in the pixel area are not damaged. In this way, the pad area is fully opened, the photoresist layer on the pixel area is completely removed, and a second organic layer is formed. No new photolithography process is added, and the wet cleaning process of the photoresist layer can be omitted. It is only necessary to select a suitable photoresist material, design a suitable photomask, and adjust the appropriate coating and etching process parameters during the opening of the pad area, without increasing the cost.

[0106] Therefore, in another optional step S300, the etching of the first stacked layer 300 of the non-pixel region 200 to form the pad opening K1 and the formation of the second organic layer 40 are performed simultaneously, that is, the etching of the first stacked layer 300 of the non-pixel region 200 to form the pad opening K1 is completed simultaneously during the formation of the second organic layer 40.

[0107] Specifically, in step S300, forming the second organic layer 40 includes:

[0108] S320: such as Figure 5b As shown, an initial photoresist layer 410 is formed above the antireflective layer 30, and then... Figure 6a As shown, an initial photoresist layer 410 is patterned to form a first opening Z1 of the first stack 300 exposed above the pad structure 211. Simultaneously, a first photoresist layer 411 is formed in the pixel region 100 and a portion of the non-pixel region 200 near the pixel region 100. A second photoresist layer 412 is formed in the non-pixel region 200 near the pad structure 211. The thickness of the second photoresist layer 412 is greater than the thickness of the first photoresist layer 411.

[0109] That is, after patterning the initial photoresist layer 410, a photoresist layer 41 with a first opening Z1 is formed. The photoresist layer 41 includes a portion of the first photoresist layer 411 and a portion of the second photoresist layer 412. The first photoresist layer 411 and the second photoresist layer 412 are actually different portions of a single photoresist layer. The thickness of the portion of the second photoresist layer 412 is greater than the thickness of the portion of the first photoresist layer 411.

[0110] S321: As Figure 6b and Figure 4 As shown, etching removes the first stacked layer 300 exposed by the first opening Z1 to form the pad opening K1. Simultaneously, the first photoresist layer 411 and the second photoresist layer 412 are etched. The first photoresist layer 411 is completely removed, and the remaining second photoresist layer 412 forms the second organic layer 40.

[0111] Specifically, for example Figure 6b As shown, the anti-reflective layer 30 exposed by the first opening Z1 is etched to expose the first organic layer 20 located above the pad structure 211; the first photoresist layer 411 and the second photoresist layer 412 are etched simultaneously, but both the first photoresist layer 411 and the second photoresist layer 412 retain a portion of their thickness.

[0112] It should be noted that while dry etching is performed on the anti-reflective layer 30 exposed by the first opening Z1, the first photoresist layer 411 and the second photoresist layer 412 are also dry etched. The anti-reflective layer 30 is typically a silicon dioxide layer, and fluorine-containing gas is used to etch the silicon dioxide anti-reflective layer 30. To ensure that the anti-reflective layer 30 covered by the first photoresist layer 411 and the second photoresist layer 412 is not etched, the thickness of the first photoresist layer 411 and the second photoresist layer 412 must be sufficient to ensure that etching the anti-reflective layer 30 exposed by the first opening Z1 does not affect the anti-reflective layer 30 covered by the first photoresist layer 411 and the second photoresist layer 412.

[0113] For example Figure 4 As shown, the first organic layer 20 exposed by the first opening Z1 is etched so that the first stack 300 composed of the first organic layer 20 and the anti-reflection layer 30 has a pad opening K1. The pad opening K1 exposes the pad structure 211 of the non-pixel area 200. The side of the first stack 300 near the pad structure 211 has a first sidewall C1. Simultaneously, the first photoresist layer 411 and the second photoresist layer 412 are etched. The first photoresist layer 411 is completely removed. The remaining thickness of the second photoresist layer 412 serves as the second organic layer 40, extending a distance from the first sidewall C1 toward the pixel area 100.

[0114] It is understandable that the pad structure 211 in the pad area 210 is covered by the pad protection layer 212. After the first stack 300 composed of the first organic layer 20 and the anti-reflection layer 30 has a pad opening K1 and the pad opening K1 exposes the pad area 210 of the non-pixel area 200, the pad protection layer 212 is removed to expose the pad structure 211.

[0115] It should be noted that in step S321, while etching the first organic layer 20 exposed by the first opening Z1, the first photoresist layer 411 and the second photoresist layer 412 are also dry etched. The first organic layer 20 is usually an organic resin layer. Oxygen is used to etch the first organic layer 20. Since the anti-reflection layer 30 is usually a silicon dioxide layer, even if the first organic layer 20 exposed by the first opening Z1 is sufficiently over-etched, the silicon dioxide anti-reflection layer 30 has sufficient tolerance to the etching gas oxygen, protecting the film layer under the anti-reflection layer 30 from being affected. In addition, the first photoresist layer 411 is etched clean in this process, and the second photoresist layer 412 retains a portion of its thickness as the second organic layer 40.

[0116] This approach does not add any photolithography steps and can also omit the wet cleaning process of the photoresist layer. It only requires selecting a suitable photoresist material, designing a suitable photomask, and adjusting appropriate coating and etching process parameters during the opening of the pad area, without increasing costs.

[0117] It is understandable that the first opening Z1 of the photoresist layer corresponds to the pad opening K1 of the first stack 300.

[0118] Steps S320-S321 allow the second organic layer 40 to extend a certain distance from the first sidewall C1 toward the pixel area 100 without adding a photolithography process or omitting the wet cleaning of the photoresist layer. Although the pad opening section is not completely covered by the second organic layer 40, the extension of the second organic layer 40 from the first sidewall C1 toward the pixel area 100 results in the anti-reflective layer 30 of a certain length from the pad opening section toward the pixel area 100 being sandwiched between the second organic layer 40 and the first organic layer 20, forming a sandwich structure similar to the effect of a protective film on explosion-proof glass. This also prevents the anti-reflective layer 30 at the pad opening section from scattering arbitrarily, reducing defect risks and improving device yield.

[0119] In order to make the patterned photoresist layer 41 include a first photoresist layer 411 portion and a second photoresist layer 412 portion of different thicknesses in a single photolithography process, optionally, the initial photoresist layer 410 is a positive photoresist layer, and the patterned initial photoresist layer 410 includes:

[0120] S10: As Figure 7As shown, the initial photoresist layer 410 is exposed and developed using a first photomask 42. The first photomask 42 includes a first region 421, a second region 422, and a third region 423. The transmittance of the second region 422 is less than that of the first region 421, and the transmittance of the first region 421 is less than that of the third region 423. The first region 421 forms the first photoresist layer 411, the second region 422 forms the second photoresist layer 412, and the third region 423 forms the first opening Z1.

[0121] It is understandable that by designing the light transmittance of the first region 421, the second region 422 and the third region 423 in the first photomask 42, the exposure dose of the photoresist layer to the first region 421, the second region 422 and the third region 423 can be different, thereby forming the first opening Z1, the first photoresist layer 411 and the second photoresist layer 412.

[0122] It is also understandable that, for the positive photoresist layer, the light transmittance of the second region 422 in the first photomask 42 is set to be the lowest, followed by the light transmittance of the first region 421, and the light transmittance of the third region 423 is the highest. This causes the photoresist layer corresponding to the third region 423 to be exposed and developed, forming the first opening Z1. The photoresist layer corresponding to the first region 421 has a smaller thickness, while the photoresist layer corresponding to the second region 422 has a larger thickness. For example, in the first photomask 42, the second region 422 is opaque, the first region 421 is semi-transparent, and the third region 423 is fully transparent.

[0123] Alternatively, the photoresist layer 41 is a positive photoresist layer, and the patterned initial photoresist layer 410 includes:

[0124] S20: As Figure 8a As shown, the initial photoresist layer 410 is exposed and developed using a second photomask 43. The second photomask 43 includes a first pattern 431, a second pattern 432, and a third pattern 433. The duty cycle of the first pattern 431 is smaller than that of the second pattern 432, and the third pattern 433 is a fully exposed area. The first pattern 431 corresponds to the formation of multiple spaced first photoresist structures R1, the second pattern 432 corresponds to the formation of multiple spaced second photoresist structures R2, and the third pattern 433 corresponds to the formation of a first opening Z1.

[0125] S21: As Figure 8b As shown, heating causes the first photoresist structure R1 to melt and form the first photoresist layer 411, and causes the second photoresist structure R2 to melt and form the second photoresist layer 412.

[0126] It is understandable that, for the positive photoresist layer, the patterned portion corresponding to the second photomask 43 is the patterned portion of the photoresist layer, which is the effective portion of the photoresist layer that is retained. The larger the duty cycle of the pattern in the second photomask 43, the more photoresist layer (the effective portion retained) corresponds to this pattern, and the thicker the photoresist layer formed after subsequent heating and baking.

[0127] Optionally, a fixed distance can be set, and the proportion of the pattern width to that fixed distance within each fixed distance is the pattern duty cycle of that fixed distance. Thus, the duty cycle of the first pattern 431 in the second photomask 43 can be set to be less than the duty cycle of the second pattern 432, and the third pattern 433 is a fully exposed area. After development, the first pattern 431 forms multiple spaced first photoresist structures R1, the second pattern 432 forms multiple spaced second photoresist structures R2, and the photoresist layer corresponding to the third pattern 433 is completely developed away, forming the first opening Z1. Then, heating and baking are applied, causing the first photoresist structure R1 to melt and form the first photoresist layer 411, and causing the second photoresist structure R2 to melt and form the second photoresist layer 412.

[0128] Optional, such as Figure 8a As shown, the distance between adjacent second photoresist structures R2 is less than the distance between adjacent first photoresist structures R1. This further ensures that the thickness of the second photoresist layer 412 formed by the melting of the second photoresist structure R2 after heating is greater than the thickness of the first photoresist layer 411 formed by the melting of the first photoresist structure R1.

[0129] Another option, such as Figure 8a As shown, along the direction from pixel region 100 to non-pixel region 200, the width of the second photoresist structure R2 is greater than the width of the first photoresist structure R1. This further ensures that the thickness of the second photoresist layer 412 formed by the melting of the second photoresist structure R2 after heating is greater than the thickness of the first photoresist layer 411 formed by the melting of the first photoresist structure R1.

[0130] Compared to the previous method of using a first photomask 42 with different transmittance in different areas to form a first photoresist layer 411 and a second photoresist layer 412 of different thicknesses, this method uses a second photomask 43 with different pattern duty cycles in different areas to form a first photoresist layer 411 and a second photoresist layer 412 of different thicknesses. The boundaries at the junction of the first photoresist layer 411 and the second photoresist layer 412, as well as the junction between the second photoresist layer 412 and the first opening Z1, may not be very clear. However, as long as there is a sufficient safe distance between the remaining second photoresist layer 412 and the pixel area 100, and between it and the pad structure 211, it is acceptable.

[0131] Further optional, such as Figure 5a As shown, the first organic layer 20 located above the pixel region 100 includes a microlens 21. When etching the first organic layer 20 to form the microlens 21, at least one first trench S1 can be formed simultaneously by etching a portion of the first organic layer 20 in the non-pixel region 200. Specifically, a microlens photolithography mask can be designed. When etching the first organic layer 20 to form the microlens 21 using the designed microlens photolithography mask, at least one first trench S1 can also be formed by etching a portion of the first organic layer 20 in the non-pixel region 200. Furthermore, the first trench S1 after forming the anti-reflective layer 30 constitutes an anti-overflow trench T1 located between the second organic layer 40 and the pixel region 100. That is, the first stack 300 composed of the first organic layer 20 and the anti-reflective layer 30 includes multiple first protrusions Q1 in the non-pixel region 200, and an anti-overflow trench T1 is formed between adjacent first protrusions Q1. Thus, during the diffusion of the second organic layer 40 into the pixel region 100, the anti-overflow trench T1 needs to be filled first before it can get closer to the pixel region 100, thereby blocking the diffusion of the second organic layer 40 into the pixel region 100.

[0132] Optional, such as Figure 5a As shown, the first organic layer 20 located above the pixel area 100 includes a microlens 21. When etching the first organic layer 20 to form the microlens 21, at least one redundant microlens 22 can be formed simultaneously by etching the portion of the first organic layer 20 near the pad structure 211 in the non-pixel area 200. The redundant microlens 22 has a structure similar to the microstructure 21. The redundant microlens 22 and the anti-reflective layer 30 above it constitute a second protrusion Q2, and the second organic layer 40 is located above the second protrusion Q2. It can be understood that the uneven surface of the second protrusion Q2 increases the contact area between the first organic layer 20 and the anti-reflective layer 30, and also increases the contact area between the redundant microlens 22 and the anti-reflective layer 30. This enhances the clamping effect of the first organic layer 20 and the second organic layer 40 on the pad opening section and the nearby anti-reflective layer 30, further preventing the anti-reflective layer at the pad opening section from breaking and scattering, reducing defect risk, and improving device yield.

[0133] like Figure 3 and Figure 4 As shown, the image sensor prepared by the method provided in this application embodiment also includes a circuit board 50, a pixel board 60, a back metal layer 70, a light-shielding layer 80, and other structures not shown, which will not be described in detail here.

[0134] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.

[0135] The features described above regarding the disclosed embodiments can be substituted or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An image sensor, characterized in that, Includes the pixel area and the non-pixel area located around the pixel area; The pixel region includes multiple pixel structures, and a first organic layer and an anti-reflective layer sequentially stacked on top of the multiple pixel structures; The non-pixel area includes multiple pad structures. The first organic layer and the anti-reflective layer form a first stack. The first stack extends from the pixel area to the non-pixel area and exposes the pad structures. The first stack has a first sidewall on the side close to the pad structures. The non-pixel area further includes a second organic layer, which is located on the side of the anti-reflective layer opposite to the first organic layer, and the second organic layer extends at least from the first sidewall toward the pixel area.

2. The image sensor according to claim 1, characterized in that, The second organic layer also covers the first sidewall and extends from the first sidewall toward the pad structure.

3. The image sensor according to claim 1 or 2, characterized in that, At least one anti-overflow trench is provided between the second organic layer and the pixel area.

4. The image sensor according to claim 3, characterized in that, The first stack includes a plurality of first protrusions in the non-pixel area, and the anti-overflow groove is formed between adjacent first protrusions.

5. The image sensor according to claim 1 or 2, characterized in that, The first stack near the first sidewall includes at least one second protrusion, and the second organic layer is located above the second protrusion.

6. The image sensor according to claim 1 or 2, characterized in that, The second organic layer extends from the first sidewall toward the pixel area for a length of not less than 10 μm.

7. The image sensor according to claim 1 or 2, characterized in that, The distance between the second organic layer and the pixel area is not less than 2 μm, and the distance between the second organic layer and the pad structure is not less than 2 μm.

8. A method for fabricating an image sensor, characterized in that, include: A substrate is provided, the substrate including a pixel region and a non-pixel region, the pixel region including a plurality of pixel structures, and the non-pixel region including a plurality of pad structures; A first stack is formed, the first stack comprising a first organic layer and an anti-reflective layer stacked sequentially, the first stack covering the pixel area and the non-pixel area; The first stack located in the non-pixel region is etched to form a pad opening that exposes the pad structure; the first stack has a first sidewall on the side near the pad structure. A second organic layer is formed, which is located above the first stack in the non-pixel area and extends at least from the first sidewall toward the pixel area.

9. The method for fabricating an image sensor according to claim 8, characterized in that, Forming the second organic layer includes: after etching to form the pad openings, forming the second organic layer on top of the first stack using inkjet printing, screen printing, or nanoimprinting.

10. The method for fabricating an image sensor according to claim 8, characterized in that, Forming the second organic layer includes: An initial photoresist layer is formed above the anti-reflective layer, and the initial photoresist layer is patterned to form a first opening that exposes the first stack above the pad structure. Simultaneously, a first photoresist layer is formed in the pixel area and a portion of the non-pixel area near the pixel area, and a second photoresist layer is formed in the non-pixel area near the pad structure. The thickness of the second photoresist layer is greater than the thickness of the first photoresist layer. The first stack exposed by the first opening is etched away to form the pad opening. The first photoresist layer and the second photoresist layer are etched simultaneously. The first photoresist layer is completely removed, and the remaining second photoresist layer forms the second organic layer.

11. The method for fabricating an image sensor according to claim 10, characterized in that, The initial photoresist layer is a positive photoresist layer, and patterning the initial photoresist layer includes: The initial photoresist layer is exposed and developed using a first photomask. The first photomask includes a first region, a second region, and a third region. The transmittance of the second region is less than that of the first region, and the transmittance of the first region is less than that of the third region. The first region corresponds to the formation of the first photoresist layer, the second region corresponds to the formation of the second photoresist layer, and the third region corresponds to the formation of the first opening.

12. The method for fabricating an image sensor according to claim 10, characterized in that, The initial photoresist layer is a positive photoresist layer, and patterning the initial photoresist layer includes: The initial photoresist layer is exposed and developed using a second photomask. The second photomask includes a first pattern, a second pattern, and a third pattern. The duty cycle of the first pattern is smaller than that of the second pattern, and the third pattern is a fully exposed area. The first pattern corresponds to the formation of multiple spaced first photoresist structures, the second pattern corresponds to the formation of multiple spaced second photoresist structures, and the third pattern corresponds to the formation of the first opening. Heating causes the first photoresist structure to melt and form the first photoresist layer, and causes the second photoresist structure to melt and form the second photoresist layer.

13. The method for fabricating an image sensor according to claim 12, characterized in that, The distance between adjacent second photoresist structures is less than the distance between adjacent first photoresist structures.

14. The method for fabricating an image sensor according to claim 13, characterized in that, Along the direction from the pixel area to the non-pixel area, the width of the second photoresist structure is greater than the width of the second photoresist structure.

15. The method for fabricating an image sensor according to any one of claims 8-14, characterized in that, The first organic layer located above the pixel area includes a microlens. When etching the first organic layer to form the microlens, the portion of the first organic layer in the non-pixel area is simultaneously etched to form at least one first trench. The first trench formed after the anti-reflective layer is formed constitutes an anti-overflow trench located between the second organic layer and the pixel area.

16. The method for fabricating an image sensor according to any one of claims 8-14, characterized in that, The first organic layer located above the pixel area includes a microlens. When the first organic layer is etched to form the microlens, at least one redundant microlens is formed by simultaneously etching the portion of the first organic layer near the pad structure in the non-pixel area. The second organic layer is formed above the redundant microlens.

Images