An image sensor, a camera assembly, and an electronic device

Abstract

The application provides an image sensor, a camera assembly and an electronic device. The image sensor comprises a photodiode and a microlens. The photodiode has a first surface and a second surface facing away from each other in a first preset direction, and a groove isolation structure is arranged on the outer circumferential side of the photodiode; the microlens is located on the side where the first surface of the photodiode is located, the microlens is convex towards the side facing away from the photodiode, and the optical axis of the microlens does not coincide with the center line of the photodiode in the first preset direction. The structure described above sets the optical axis of the microlens to not coincide with the center line of the photodiode in the first preset direction, so that the groove structure plays a reflection role on the light with a longer wavelength incident on the image sensor, which is beneficial to reducing the light with a longer wavelength passing through the photodiode, thereby improving the light absorption efficiency of the light with a longer wavelength and the quantum efficiency of the optical image sensor.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, and particularly relates to an image sensor, camera assembly, and electronic device. Background Technology

[0002] Back-illuminated complementary metal-oxide-semiconductor (BSI-CMOS) image sensors have become the mainstream in mobile phone cameras, and the demand for near-infrared (NIR) image sensors used for iris verification, facial recognition, and motion capture is increasing daily. Back-illuminated image sensors are more suitable for the near-infrared band. However, due to the long wavelength of near-infrared applications (700–1000 nm), traditional pixel structures have low quantum efficiency in the near-infrared band (around 10% at 850 nm and around 4% at 940 nm). Therefore, enhancing the sensitivity to near-infrared light becomes particularly important. The simplest method is to increase the thickness of the incident photon absorption layer, but process limitations such as high-energy injection make this method difficult to achieve. Summary of the Invention

[0003] According to a first aspect of the present invention, an image sensor is provided, the image sensor comprising:

[0004] A photodiode has a first surface, and a trench isolation structure is provided on the outer peripheral side of the photodiode;

[0005] A microlens is located on one side of the first surface of the photodiode. The microlens protrudes toward the side opposite to the photodiode, and the optical axis of the microlens does not coincide with the center line of the photodiode along a first preset direction.

[0006] In some embodiments, the size of the microlens projected along a first preset direction is the same as the size of the photodiode projected along the first preset direction, the size of the microlens and the photodiode in a second preset direction is D, and the size of the microlens and the photodiode in a third preset direction is T;

[0007] Wherein, the first preset direction is perpendicular to the plane determined by the second preset direction and the third preset direction; the distance between the optical axis of the microlens and the central axis of the photodiode along the first preset direction in the second preset direction is D / 2; and / or the distance between the optical axis of the microlens and the central axis of the photodiode along the first preset direction in the third preset direction is T / 2.

[0008] In some embodiments, the dimensions of the microlens and the photodiode in a second preset direction are equal to the dimensions of the microlens and the photodiode in a third preset direction.

[0009] In some embodiments, an anti-reflective layer is provided between the first surface of the photodiode and the microlens.

[0010] In some embodiments, the antireflective layer includes an isolation structure corresponding to the trench isolation structure.

[0011] In some embodiments, the image sensor is a back-illuminated image sensor.

[0012] In some embodiments, the photodiode has a second surface opposite to the first surface in a first preset direction, and the image sensor includes a transfer gate disposed on the second surface of the photodiode.

[0013] In some embodiments, the image sensor includes a plurality of photodiodes and a plurality of microlenses, wherein the plurality of photodiodes are arranged in an array.

[0014] According to a second aspect of the present invention, a camera assembly is provided, the camera assembly including the image sensor as described above.

[0015] According to a third aspect of the present invention, an electronic device is provided, the electronic device including a housing and a camera assembly as described above, the camera assembly being assembled on the housing.

[0016] Based on the above technical solution, the above structure sets the optical axis of the microlens to not coincide with the center line of the photodiode along the first preset direction, so that the trench structure reflects the longer wavelength light incident on the image sensor, which helps to increase the optical path of longer wavelength light in the photodiode, thereby reducing the amount of longer wavelength light passing through the photodiode, improving the absorption efficiency of longer wavelength light, and improving the quantum efficiency of the optical image sensor. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of an image sensor in related technologies;

[0018] Figure 2 for Figure 1 The image sensor shown is a 3D structural diagram.

[0019] Figure 3 for Figure 1 The image sensor shown is a 3D structural diagram of the photodiode.

[0020] Figure 4 A cross-sectional view of an image sensor provided according to an embodiment of the present invention;

[0021] Figure 5 for Figure 4 The image sensor shown is illustrated with schematic diagrams of the incident light rays.

[0022] Figure 6 A three-dimensional structural diagram of an image sensor provided according to an embodiment of the present invention;

[0023] Figure 7 for Figure 6 The image sensor shown is a 3D structural diagram of the photodiode.

[0024] Figure 8 A three-dimensional structural diagram of another image sensor provided according to an embodiment of the present invention;

[0025] Figure 9 A comparative analysis table of quantum efficiency and light transmittance for different image sensors. Detailed Implementation

[0026] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0027] Please refer to Figures 1 to 3 As shown, in related technologies, an image sensor 100' applied to near-infrared radiation includes a photodiode 10' and a microlens 20' located on the light-incident side of the photodiode 10'. The optical axis R' of the microlens 20' coincides with the center line of the photodiode along the thickness direction Z' of the photodiode 10'. Figure 1 The projection of the microlens 20' onto the thickness direction Z' shown is almost completely coincident with the projection of the photodiode 10' onto the thickness direction Z'. However, due to the long wavelength of near-infrared light (700-1000 nm), the near-infrared image sensor 100' has a low quantum efficiency in the near-infrared light band.

[0028] Therefore, embodiments of the present invention provide an image sensor, the image sensor comprising:

[0029] A photodiode has a first surface, and a trench isolation structure is provided on the outer peripheral side of the photodiode;

[0030] A microlens is located on one side of the first surface of the photodiode. The microlens protrudes toward the side opposite to the photodiode, and the optical axis of the microlens does not coincide with the center line of the photodiode along a first preset direction.

[0031] The aforementioned structure, by setting the optical axis of the microlens to be non-coinciding with the center line of the photodiode along a first preset direction, allows the trench structure to reflect longer wavelength light incident on the image sensor. This increases the optical path length of longer wavelength light within the photodiode, thereby reducing the amount of longer wavelength light passing through the photodiode, improving the absorption efficiency of longer wavelength light, and ultimately enhancing the quantum efficiency of the optical image sensor. Furthermore, based on the near-infrared image sensor 100' described above, the image sensor provided by this invention can be fabricated using existing processes without requiring additional steps, thus contributing to cost control.

[0032] The image sensor described in this application can be a near-infrared (NIR) image sensor.

[0033] The following is in conjunction with the appendix Figures 1 to 9 The image sensor provided in this application will be described in detail.

[0034] Please refer to Figure 4 and combine when necessary Figure 6 and Figure 7 As shown, in some embodiments, the image sensor 100 includes a photodiode 10 and a microlens 20. The photodiode 10 has a first surface 1001 and a second surface 1002 that are opposite to each other in a first preset direction, and a trench isolation structure 30 is provided on the outer peripheral side of the photodiode 10. The microlens 20 is located on the side where the first surface 1001 of the photodiode 10 is located, and the microlens 20 protrudes toward the side opposite to the photodiode 10. The optical axis R of the microlens 20 does not coincide with the center line of the photodiode 10 along the first preset direction.

[0035] The trench isolation structure 30 here can reduce crosstalk between different photodiodes 10, and when the microlens 20 is set in the above manner, it can also reflect the light entering the photodiode 10 from the microlens 20.

[0036] In some embodiments, the trench isolation structure 30 can be a deep trench isolation (DTI) structure formed using deep trench isolation technology, which can effectively prevent crosstalk between different photodiodes 10 while improving the absorption efficiency of longer wavelength light and the quantum efficiency of the optical image sensor.

[0037] In some embodiments, the first preset direction can be the thickness direction Z of the image sensor 100. Of course, the first preset direction can also be the length direction or width direction of the sensor, etc.

[0038] In some embodiments, the image sensor 100 includes a plurality of photodiodes 10 and a plurality of microlenses 20, wherein the plurality of photodiodes 10 are arranged in an array. Please refer to Figure 7 As shown, for example, the plurality of photodiodes 10 are arranged in an array on a plane perpendicular to a first preset direction.

[0039] Of course, in some other embodiments, the image sensor may also include only a photodiode 10.

[0040] In some embodiments, the image sensor 100 is a back-illuminated image sensor 100. The first surface 1001 of the photodiode 10 is its back side. Light (e.g., near-infrared light) in the image sensor 100 is incident from the side of the microlens 20 away from the photodiode 10, passes through the microlens, and enters the photodiode 10 to achieve photoelectric conversion in the photodiode 10.

[0041] In some embodiments, the size of the microlens 20 projected along a first preset direction is the same as the size of the photodiode 10 projected along the first preset direction. The dimensions of the microlens 20 and the photodiode 10 in a second preset direction are D, and the dimensions of the microlens 20 and the photodiode 10 in a third preset direction are T. The first preset direction is perpendicular to the plane defined by the second and third preset directions.

[0042] The size of the microlens 20 projected along the first preset direction is the same as the size of the photodiode 10 projected along the first preset direction, which can be understood as the shape and size of their projections along the first preset direction being the same.

[0043] Here, the cross-section of the photodiode 10 in the first preset direction can be rectangular, circular, square, or other shapes. The cross-section of the microlens 20 in the first preset direction can also be rectangular, circular, square, or other shapes accordingly.

[0044] In some embodiments, the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along a first preset direction are offset in a second preset direction, and the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction are offset in a third preset direction. For example, the distance between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the second preset direction is D / 2, and the distance between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the third preset direction is T / 2.

[0045] In some embodiments, the second preset direction and the third preset direction can be respectively Figure 7The X and Y directions are shown. Here, the X, Y, and Z directions are all perpendicular to each other, that is, the first preset direction, the second preset direction, and the third preset direction are all perpendicular to each other. Of course, in some other embodiments, the second preset direction and the third preset direction may not be perpendicular, but may form other included angles.

[0046] In some embodiments, the dimensions of the microlens 20 and the photodiode 10 in a second predetermined direction are equal to the dimensions of the microlens 20 and the photodiode 10 in a third predetermined direction. For example... Figure 6 and Figure 7 In the image sensor 100 shown, D and T are equal, and the dimensions of D and T can be understood as the size of a pixel.

[0047] In some embodiments, an anti-reflection layer 40 is provided between the first surface 1001 of the photodiode 10 and the microlens 20.

[0048] In some embodiments, the antireflective layer 40 is provided with an isolation structure 50 corresponding to the trench isolation structure 30. The isolation structure 50 helps to prevent crosstalk between different diodes.

[0049] In some embodiments, the image sensor 100 includes a transfer gate 60 disposed on the second surface 1002 of the photodiode 10.

[0050] It should be noted that in some other embodiments, the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction are offset only in the second preset direction. For example, the distance between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the second preset direction is D / 2. Or, the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction are offset only in the third preset direction. For example, the distance between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the third preset direction is T / 2. Alternatively, the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction are offset in both the second preset direction and the third preset direction, but the amount of offset between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the second or third preset direction is different from the corresponding offset in the image sensor 100.

[0051] For example, in some other embodiments, please refer to Figure 8 As shown, Figure 8This is a three-dimensional structural diagram of image sensor 200. Image sensor 200 has a generally similar structure to image sensor 100 described above; similarities or identicalities can be found in the related descriptions above. The difference lies in that, in image sensor 200, only the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction are offset only in a third preset direction. The distance between the optical axis R of the microlens 20 and the central axis r of the photodiode 10 along the first preset direction in the third preset direction is T / 2.

[0052] Compared to the related art where the optical axis of the microlens coincides with the center line of the photodiode along a first preset direction, the image sensor provided in this application has a preset angle (e.g., within 10°) between the surface of the microlens 20 (i.e., the light incident point) and the optical axis R. This significantly reduces the light transmittance and increases the quantum efficiency.

[0053] Furthermore, in the various embodiments provided in this application, the microlens 20 of the image sensor 100 is offset by half a pixel in both the second preset direction and the third preset direction. Compared with other implementations with offsets (such as the image sensor 200), the image sensor 100 has lower light transmittance and relatively higher quantum efficiency.

[0054] For example, please refer to Figure 9 As shown, Figure 9 The diagram illustrates the quantum efficiency and light transmittance of image sensors 100', 100, and 200 at angles of 0°, 10°, and -10° between the incident point of their respective microlenses and the optical axis of the microlenses. Figure 9 The infrared light used in the process has a wavelength of 850 nm. The angle between the incident light point and the optical axis of the microlens is 0°, which can be understood as the incident light point being on the optical axis. Combined with... Figure 1 As shown, the angle between the light-incident point of the microlens 20' in the image sensor 100' and the optical axis R' of the microlens 20' is 10°, which can be interpreted as an angle β of 10°. Similarly, the angle between the light-incident point of the microlens 20' in the image sensor 100' and the optical axis R' of the microlens 20' is -10°, which can be interpreted as an angle α of 10°. Accordingly, combined with... Figure 4 As shown, in image sensor 100, the angle between the light-incident point of microlens 20 and the optical axis R of microlens 20 is 10°, which can be represented by angle β being 10°. Similarly, the angle between the light-incident point of microlens 20 and the optical axis R of microlens 20 is -10°, which can be represented by angle α being 10°. The angles in image sensor 200 are similar. Figure 9It can be seen that, for infrared light with a wavelength of 850nm, among these three image sensors, relative to image sensor 100', image sensors 100 and 200 exhibit relatively high quantum efficiencies and significantly lower light transmittance when the angles between the incident light point on their respective microlenses and the optical axis R of the microlens are 0°, 10°, and -10°, respectively. Furthermore, under the same conditions, image sensor 100 has a higher quantum efficiency and lower light transmittance than image sensor 200.

[0055] Furthermore, based on the above description of the image sensor, it can be understood that the incident light can be adjusted by changing the radius of curvature of the microlens 20. For example, for image sensors applied to relatively long optical wavelengths, the radius of curvature of the microlens can be set to a relatively small size. Correspondingly, for image sensors applied to relatively short optical wavelengths, the radius of curvature of the microlens can be set to a relatively large size. The radius of curvature of the microlens in the image sensor can be specifically determined according to the optical wavelength it is used in (e.g., the infrared band).

[0056] The present invention also provides a camera assembly, the camera assembly including the image sensor as described above.

[0057] The present invention also provides an electronic device including a camera assembly as described above. The electronic device includes a housing, and the camera assembly is assembled onto the housing. This electronic device can be a mobile phone, camera, tablet, or other device with a camera assembly.

[0058] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention. The above descriptions are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An image sensor, characterized in that, The image sensor includes: A photodiode has a first surface, and a trench isolation structure is provided on the outer peripheral side of the photodiode; A microlens is located on one side of the first surface of the photodiode. The microlens protrudes toward the side opposite to the photodiode, and the optical axis of the microlens does not coincide with the center line of the photodiode along a first preset direction. The size of the microlens projected along the first preset direction is the same as the size of the photodiode projected along the first preset direction. The size of the microlens and the photodiode in the second preset direction is D, and the size of the microlens and the photodiode in the third preset direction is T. Wherein, the first preset direction is perpendicular to the plane determined by the second preset direction and the third preset direction; the distance between the optical axis of the microlens and the central axis of the photodiode along the first preset direction in the second preset direction is D / 2; and / or the distance between the optical axis of the microlens and the central axis of the photodiode along the first preset direction in the third preset direction is T / 2; The trench isolation structure can also reflect light entering the photodiode from the microlens, increasing the optical path of the light within the photodiode. The light includes near-infrared light with wavelengths from 700 nm to 1000 nm.

2. The image sensor as described in claim 1, characterized in that, The dimensions of the microlens and the photodiode in the second preset direction are equal to the dimensions of the microlens and the photodiode in the third preset direction.

3. The image sensor as described in claim 1, characterized in that, An anti-reflection layer is provided between the first surface of the photodiode and the microlens.

4. The image sensor as described in claim 3, characterized in that, The anti-reflective layer includes an isolation structure corresponding to the trench isolation structure.

5. The image sensor as described in any one of claims 1 to 4, characterized in that, The image sensor is a back-illuminated image sensor.

6. The image sensor as described in claim 5, characterized in that, The photodiode has a second surface that is opposite to the first surface in a first preset direction, and the image sensor includes a transfer gate disposed on the second surface of the photodiode.

7. The image sensor as claimed in claim 1, characterized in that, The image sensor includes multiple photodiodes and multiple microlenses, with the multiple photodiodes arranged in an array.

8. A camera assembly, characterized in that, The camera assembly includes an image sensor as claimed in any one of claims 1 to 7.

9. An electronic device, characterized in that, The electronic device includes a housing and a camera assembly as described in claim 8, the camera assembly being assembled onto the housing.

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