Fingerprint camera module and image sensor thereof

Abstract

The utility model discloses an image sensor, including photosensitive substrate, color filter and microlens array, the color filter is located on the photosensitive surface of photosensitive substrate, microlens array is located on the side surface of color filter away from photosensitive substrate, the color filter is equipped with infrared filter layer on the surface to microlens array one side. This image sensor can reduce the risk of the uniformity of the infrared filter layer appears coating. The utility model discloses a kind of fingerprint camera module, including above-mentioned image sensor.

Description

Technical Field

[0001] This utility model relates to fingerprint recognition technology, and more particularly to a fingerprint camera module and its image sensor. Background Technology

[0002] Smartphones, tablets, and other mobile devices typically include fingerprint camera modules to capture fingerprint images. In a fingerprint camera module, the image sensor converts light signals into electrical signals, and the infrared cut-off filter filters infrared light. Similar to traditional camera modules, the image sensor and infrared cut-off filter in a fingerprint camera module are two separate components. During manufacturing, these two components must be assembled separately, requiring two distinct assembly steps, resulting in numerous steps and low production efficiency.

[0003] To address the aforementioned issues, Chinese Patent Application No. CN201820786750.X discloses an image sensor comprising: a photosensitive substrate including opposing connecting surfaces and a photosensitive surface, the connecting surface for connecting a circuit board of a camera module; a color filter disposed on the photosensitive surface; a macro lens disposed on the surface of the color filter away from the photosensitive substrate; and an infrared filter layer disposed on the side of the macro lens away from the color filter. This image sensor integrates both a color filter and an infrared filter layer. When applied to a camera module, the traditional infrared cut-off filter in a camera module can be omitted, thus eliminating the need for assembling the infrared cut-off filter, simplifying assembly, improving assembly efficiency, and reducing the production cost of the camera module.

[0004] However, the surface of the macro lens is curved, and when the infrared filter layer is integrated on its surface, the infrared filter layer is prone to uneven coating. This not only affects the infrared filtering performance of the infrared filter layer, but also affects the focusing effect of the macro lens. Utility Model Content

[0005] To address the shortcomings of the prior art, this invention provides a fingerprint camera module and its image sensor, which can reduce the risk of uneven coating in the infrared filter layer.

[0006] The technical problem to be solved by this utility model is achieved through the following technical solution:

[0007] An image sensor includes a photosensitive substrate, a color filter, and a microlens array. The color filter is disposed on the photosensitive surface of the photosensitive substrate, and the microlens array is disposed on the side of the color filter away from the photosensitive substrate. An infrared filtering layer is provided on the surface of the color filter facing the microlens array.

[0008] Furthermore, the infrared filter layer adopts a refractive index gradient film structure.

[0009] Furthermore, the infrared filter layer is a tantalum pentoxide-silicon dioxide gradient film with a thickness of 65-130 nm.

[0010] Furthermore, a medium adhesion layer is provided between the infrared filter layer and the color filter.

[0011] Furthermore, the dielectric adhesion layer is a porous silicon dioxide layer with a thickness of 5-10 nm.

[0012] Furthermore, a stress transition layer is provided between the infrared filter layer and the dielectric adhesion layer, and the Young's modulus of the stress transition layer is between that of the infrared filter layer and the dielectric adhesion layer.

[0013] Furthermore, the stress transition layer is a silicon oxynitride layer with a thickness of 15-20 nm.

[0014] Furthermore, the color filter is a Bayer color filter.

[0015] A fingerprint camera module includes the image sensor described above.

[0016] The present invention has the following beneficial effects: The image sensor of the present invention integrates the infrared filter layer on the surface of the color filter. Compared with the microlens array, the surface of the color filter has better flatness and a near-planar structure. During the coating process, it can better form an infrared filter layer with uniform film thickness, thereby ensuring the infrared filtering performance of the infrared filter layer and reducing the coating difficulty. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the stacked structure of the image sensor provided by this utility model.

[0018] Figure 2 This is a schematic diagram of another stacked structure of the image sensor provided by this utility model.

[0019] Figure 3 This is a schematic diagram of the stacked structure of the fingerprint camera module provided by this utility model. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings. Throughout the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this utility model, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0022] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0023] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] Example 1

[0025] like Figure 1 As shown, an image sensor includes a photosensitive substrate 21, a color filter 22, and a microlens array 23. The color filter 22 is disposed on the photosensitive surface of the photosensitive substrate 21, and the microlens array 23 is disposed on the side of the color filter 22 away from the photosensitive substrate 21. The color filter 22 has an infrared filter layer 221 on the surface facing the microlens array 23.

[0026] The image sensor of this invention integrates the infrared filter layer 221 on the surface of the color filter 22. Compared with the microlens array 23, the surface of the color filter 22 has better flatness and a near-planar structure. During the coating process, it can better form an infrared filter layer 221 with uniform film thickness, thereby ensuring the infrared filtering performance of the infrared filter layer 221 and reducing the coating difficulty.

[0027] In this embodiment, the color filter 22 is a Bayer color filter, which includes at least three color filter units: RGB. Each color filter unit corresponds to a pixel on the photosensitive substrate 21.

[0028] The light transmission band of the color filter 22 is between 420-650nm. In order to achieve spectral matching with the color filter 22 and avoid interference with the light transmission band of the color filter 22, the infrared filter layer 221 needs to maintain high transmittance in the 400-650nm band, steeply cut off in the 650-720nm band, and deeply cut off above 720nm.

[0029] To avoid interference fringes on the color filter 22 under such narrow bandpass conditions, and to ensure that the thickness of the infrared filter layer 221 meets the requirements, the infrared filter layer 221 preferably adopts a refractive index gradient film structure instead of the traditional high and low refractive index stacked film structure. That is, the refractive index of the infrared filter layer 221 changes continuously from high to low along its thickness direction.

[0030] The infrared filter layer 221 is fabricated using a dual-target co-sputtering process, in which a high-refractive-index target and a low-refractive-index target are simultaneously sputtered onto the surface of the color filter 22. During the sputtering process, the ratio between the high-refractive-index target and the low-refractive-index target is adjusted over time so that the ratio of the high-refractive-index target to the low-refractive-index target in the infrared filter layer 221 changes continuously along its thickness. The higher the proportion of the high-refractive-index target, the higher the refractive index of the corresponding part of the infrared filter layer 221, and the higher the proportion of the low-refractive-index target, the lower the refractive index of the corresponding part of the infrared filter layer 221.

[0031] In this embodiment, the infrared filter layer 221 is a tantalum pentoxide-silicon dioxide gradient film with a thickness of 65-130nm and its refractive index changes between 2 and 3 times.

[0032] Since the color filter 22 is generally made of organic resin, such as acrylic, while the infrared filter layer 221 is made of inorganic oxide, the material properties of the two differ significantly, resulting in lower bonding strength. Therefore, preferably, such as... Figure 2 As shown, a medium adhesion layer 222 is provided between the infrared filter layer 221 and the color filter 22.

[0033] The medium adhesion layer 222 is used to improve the surface adhesion of the color filter 22 to reduce the risk of the infrared filter layer 221 falling off the surface of the color filter 22.

[0034] In this embodiment, the dielectric adhesion layer 222 is a porous silicon dioxide layer with a thickness of 5-10 nm.

[0035] Furthermore, due to the significant difference in the coefficients of thermal expansion between the color filter 22 and the infrared filter layer 221, a stress transition layer 223 is provided between the infrared filter layer 221 and the medium adhesion layer 222 to avoid thermal stress concentration and delamination at the interface edges. The Young's modulus of the stress transition layer 223 is between that of the infrared filter layer 221 and the medium adhesion layer 222, so as to disperse the thermal stress between the interfaces of each layer.

[0036] In this embodiment, the stress transition layer 223 is a silicon oxynitride layer with a thickness of 15-20 nm.

[0037] The color filter 22 and the infrared filter layer 221 are connected by a decreasing stress gradient formed by the porous silica layer and the silicon oxynitride layer in sequence.

[0038] Example 2

[0039] like Figure 3 As shown, a fingerprint camera module includes a circuit board 1, an image sensor 2 as described in Embodiment 1, and an optical lens 3. The image sensor 2 is mounted on the circuit board 1, and the optical lens 3 is disposed on the photosensitive side of the image sensor 2.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and not to limit them. Although the present utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present utility model, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the present utility model.

Claims

1. An image sensor, comprising a photosensitive substrate, a color filter, and a microlens array, wherein the color filter is disposed on the photosensitive surface of the photosensitive substrate, and the microlens array is disposed on the side of the color filter away from the photosensitive substrate; characterized in that, The color filter has an infrared filter layer on the surface facing the microlens array.

2. The image sensor according to claim 1, characterized in that, The infrared filter layer adopts a refractive index gradient film structure.

3. The image sensor according to claim 1 or 2, characterized in that, The infrared filter layer is a tantalum pentoxide-silicon dioxide gradient film with a thickness of 65-130 nm.

4. The image sensor according to claim 1, characterized in that, A medium adhesion layer is provided between the infrared filter layer and the color filter.

5. The image sensor according to claim 4, characterized in that, The medium adhesion layer is a porous silicon dioxide layer with a thickness of 5-10 nm.

6. The image sensor according to claim 4, characterized in that, A stress transition layer is provided between the infrared filter layer and the medium adhesion layer, and the Young's modulus of the stress transition layer is between that of the infrared filter layer and the medium adhesion layer.

7. The image sensor according to claim 6, characterized in that, The stress transition layer is a silicon oxynitride layer with a thickness of 15-20 nm.

8. The image sensor according to claim 1, characterized in that, The color filter is a Bayer color filter.

9. A fingerprint camera module, characterized in that, Includes the image sensor as described in claim 1.

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