Method for forming an infrared cut-off filter film in an optical fingerprint device

Abstract

The present invention provides a method for forming an infrared cut-off filter film in an optical fingerprint device. By covering a part corresponding to the pad area of the image sensor with a jig and forming an infrared cut-off filter film in a part corresponding to the photosensitive area of the image sensor, the purpose of avoiding the pad area of the image sensor by the infrared cut-off filter film is achieved, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the lithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to a method for forming an infrared cut-off filter film in an optical fingerprint device. Background Art

[0002] Current fingerprint recognition solutions include optical technology, silicon technology (capacitive / radio frequency), ultrasonic technology, etc. Among them, optical fingerprint recognition technology has been widely used in portable electronic devices.

[0003] Optical fingerprint recognition technology uses an optical imaging device based on the principle of total internal reflection of light (FTIR). Light shines on the outer surface of a light-transmitting layer (such as organic or inorganic glass) with a fingerprint pressed on it, and the reflected light is obtained by an image sensor. The amount of reflected light depends on the depth of the fingerprint ridges and valleys pressed on the outer surface of the glass, as well as the grease and moisture between the skin and the glass. When the light passes through the glass and reaches the center of the valley, total internal reflection occurs at the interface between the glass and the air, and the light is reflected to the image sensor. The light incident on the ridge does not undergo total internal reflection, but is absorbed by the contact surface between the ridge and the glass or diffusely reflected to other places, thus forming an image of the fingerprint on the image sensor.

[0004] Since a relatively large-sized microlens is required to increase the energy of the incident light and achieve higher image quality, in the prior art, a relatively thick light-transmitting layer (more than 50 μm) is often provided above the pixel unit and a relatively thick light-blocking structure (such as 15 - 50 μm) is provided between the pixel units to solve the problem that the incident light enters adjacent pixel units of the image sensor, resulting in signal crosstalk. The light-blocking structure can be formed by a silicon wafer. In addition, an infrared cut-off filter film needs to be provided above the pixel unit to reduce the infrared light in the incident light from entering the image sensor, causing noise crosstalk and image distortion, and improving the optical performance of the optical fingerprint device. However, it should be noted that the light-transmitting layer, the light-blocking structure, and the infrared cut-off filter film all need to avoid the pad area of the image sensor to prevent affecting the electrical connection performance of the pad area.

[0005] In the prior art, the lift-off process is usually used to avoid forming an infrared cut-off filter film in the pad area, that is, a photoresist is used to cover the part corresponding to the pad area of the image sensor, and an infrared cut-off filter film is formed in the part corresponding to the photosensitive area of the image sensor. However, this method must use a photolithography step, which requires the use of a relatively expensive lithography machine and a large amount of disposable photoresist materials, resulting in limited production efficiency and high manufacturing costs. Summary of the Invention

[0006] The object of the present invention is to provide a method for forming an infrared cut-off filter film in an optical fingerprint device, which can improve production efficiency, increase production capacity, and reduce manufacturing costs.

[0007] Based on the above considerations, the present invention provides a method for forming an infrared cut-off filter film in an optical fingerprint device, comprising the following steps: providing a first wafer formed with a plurality of image sensors; providing a jig, the jig covering a part corresponding to the pad area of the image sensor, and forming an infrared cut-off filter film on a part corresponding to the photosensitive area of the image sensor.

[0008] Preferably, provide a first wafer formed with a plurality of image sensors; provide a jig to cover a part of the first wafer corresponding to the pad area of the image sensor, and form an infrared cut-off filter film on a part of the first wafer corresponding to the photosensitive area of the image sensor.

[0009] Preferably, provide a first wafer formed with a plurality of image sensors; provide a second wafer, and provide a light-blocking structure formed by the second wafer on the first wafer; before or after the step of providing the second wafer, provide a jig to cover a part of the second wafer corresponding to the pad area of the image sensor, and form an infrared cut-off filter film on a part of the second wafer corresponding to the photosensitive area of the image sensor.

[0010] Preferably, provide a first wafer formed with a plurality of image sensors; provide a light-blocking structure on the first wafer; provide a light-transmitting layer on the light-blocking structure; before or after the step of providing the light-transmitting layer, provide a jig to cover a part of the light-transmitting layer corresponding to the pad area of the image sensor, and form an infrared cut-off filter film on a part of the light-transmitting layer corresponding to the photosensitive area of the image sensor.

[0011] Preferably, the light-blocking structure is formed by a second wafer.

[0012] Preferably, the first wafer and the jig are closely attached by a clamping structure or a magnetic structure or a temporary bonding adhesive to improve the film-forming quality, and after forming the infrared cut-off filter film, remove the clamping structure or the magnetic structure or the temporary bonding adhesive.

[0013] Preferably, the first wafer is placed on a magnetic substrate, the jig and the substrate adsorb each other to clamp the first wafer in the middle, after forming the infrared cut-off filter film, remove the jig, and after the first wafer and the light-blocking structure are combined with each other, remove the substrate.

[0014] Preferably, the second wafer and the jig are closely attached by a clamping structure or a magnetic structure or a temporary bonding adhesive to improve the film-forming quality, and after forming the infrared cut-off filter film, remove the clamping structure or the magnetic structure or the temporary bonding adhesive.

[0015] Preferably, the second wafer is placed on a magnetic substrate, the jig and the substrate adsorb each other to clamp the second wafer in the middle, after forming the infrared cut-off filter film, remove the jig, and after the first wafer and the second wafer are combined with each other, remove the substrate.

[0016] Preferably, the step of providing the second wafer includes temporarily bonding the second wafer to a support carrier, then thinning the second wafer. After removing the support carrier, an infrared cut-off filter film is formed on the portion of the second wafer corresponding to the photosensitive area of the image sensor. After the first wafer and the second wafer are bonded to each other, the second wafer does not need to be thinned.

[0017] Preferably, the light-transmitting layer is closely attached to the jig through a clamping structure or a magnetic structure or a temporary bonding adhesive to improve the film-forming quality. After the infrared cut-off filter film is formed, the clamping structure or the magnetic structure or the temporary bonding adhesive is removed.

[0018] Preferably, the light-transmitting layer is placed on a magnetic substrate, and the jig and the substrate are adsorbed to each other to clamp the light-transmitting layer in the middle. After the infrared cut-off filter film is formed, the jig is removed. After the light-blocking structure and the light-transmitting layer are bonded to each other, the substrate is removed.

[0019] In the method for forming an infrared cut-off filter film in the optical fingerprint device of the present invention, by covering the portion corresponding to the pad area of the image sensor with a jig and forming an infrared cut-off filter film on the portion corresponding to the photosensitive area of the image sensor, the purpose of avoiding the pad area of the image sensor by the infrared cut-off filter film is achieved, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the photolithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0021] Figures 1-3 is a schematic diagram of the method for forming an infrared cut-off filter film in the optical fingerprint device of the present invention;

[0022] Figures 4-13 is a process schematic diagram of the method for forming an infrared cut-off filter film in the optical fingerprint device according to a preferred embodiment of the present invention;

[0023] Figures 14-23 is a process schematic diagram of the method for forming an infrared cut-off filter film in the optical fingerprint device according to another preferred embodiment of the present invention;

[0024] Figures 24-30 is a process schematic diagram of the method for forming an infrared cut-off filter film in the optical fingerprint device according to still another preferred embodiment of the present invention.

[0025] In the figures, throughout the different views, the same or similar reference numerals denote the same or similar devices (modules) or steps. Detailed implementation mode

[0026] The present invention provides a method for forming an infrared cut-off filter film in an optical fingerprint device. By covering a part corresponding to the pad area of the image sensor with a jig, an infrared cut-off filter film is formed in a part corresponding to the photosensitive area of the image sensor, achieving the purpose of avoiding the pad area of the image sensor for the infrared cut-off filter film, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the photolithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced.

[0027] In the following detailed description of the preferred embodiments, reference will be made to the accompanying drawings that form a part of the present invention. The accompanying drawings illustrate, by way of example, specific embodiments that can implement the present invention. The exemplary embodiments are not intended to exhaust all embodiments according to the present invention. It can be understood that other embodiments can be utilized without departing from the scope of the present invention, and structural or logical modifications can also be made. Therefore, the following detailed description is not restrictive, and the scope of the present invention is defined by the appended claims.

[0028] See Figures 1-3 , a plurality of openings 11 are provided on the jig 1 (the jig can be in the shape of a wafer or other shapes, and can be integral or split). Only three openings 11 are shown here as an example rather than a limitation. A plurality of image sensors 21 are provided on the wafer 2. Only three image sensors 21 are shown here as an example rather than a limitation. The state where the jig 1 covers the wafer 2 is as Figure 3 shown. The jig 1 covers a part of the wafer 2 corresponding to the pad area of the image sensor 21, exposing a part of the wafer 2 corresponding to the photosensitive area of the image sensor 21. Thus, an infrared cut-off filter film can be formed only in a part of the wafer 2 corresponding to the photosensitive area of the image sensor 21, achieving the purpose of avoiding the pad area of the image sensor for the infrared cut-off filter film, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the photolithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced.

[0029] Those skilled in the art can understand that it is also possible that the image sensor 21 is not provided on the wafer 2 itself, but on another wafer used for bonding with the wafer 2. As long as the jig 1 covers a part of the wafer 2 corresponding to the pad area of the image sensor 21 and exposes a part of the wafer 2 corresponding to the photosensitive area of the image sensor 21, an infrared cut-off filter film can be formed only in a part of the wafer 2 corresponding to the photosensitive area of the image sensor 21.

[0030] In addition, when setting the light-transmitting layer, a jig can be provided to cover the part of the light-transmitting layer corresponding to the pad area of the image sensor, and expose the part of the light-transmitting layer corresponding to the photosensitive area of the image sensor, so that an infrared cut-off filter film is formed only on the part of the light-transmitting layer corresponding to the photosensitive area of the image sensor.

[0031] Therefore, by covering the part corresponding to the pad area of the image sensor with a jig and forming an infrared cut-off filter film on the part corresponding to the photosensitive area of the image sensor, the purpose of avoiding the pad area of the image sensor by the infrared cut-off filter film can be achieved, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the lithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced.

[0032] The present invention will be elaborated in detail below with reference to specific embodiments.

[0033] Embodiment 1

[0034] Figures 4-13 It is a process schematic diagram of a method for forming an infrared cut-off filter film in an optical fingerprint device according to a preferred embodiment of the present invention.

[0035] Refer to Figure 4 , a first wafer 300 formed with a plurality of image sensors is provided. The image sensor includes a pad area 302 and a photosensitive area 303, and the pad area 302 and the photosensitive area 303 are separated by a dotted line in the figure.

[0036] Refer to Figure 5 , a jig 401 covers the part of the first wafer 300 corresponding to the pad area 302 of the image sensor. Preferably, the first wafer 300 and the jig 401 are closely attached through a clamping structure or a magnetic structure or a temporary bonding adhesive to improve the film-forming quality. After the infrared cut-off filter film is formed, the clamping structure or the magnetic structure or the temporary bonding adhesive is removed. In this embodiment, the magnetic structure is taken as an example. The first wafer 300 is placed on a magnetic substrate 402 (the substrate 402 can be integral or split), and the jig 401 and the substrate 402 are adsorbed to each other to clamp the first wafer 300 in the middle.

[0037] Refer to Figure 6 , an infrared cut-off filter film 403 is formed on the part of the first wafer 300 corresponding to the photosensitive area 303 of the image sensor.

[0038] Refer to Figure 7 , after the infrared cut-off filter film 403 is formed, the jig 401 is removed. For example, a tool with stronger magnetism than the substrate 402 can be used to remove the jig 401.

[0039] Refer to Figures 8-10, a light-shielding structure 404 is disposed on the first wafer 300. Preferably, a second wafer 400 is provided, and the light-shielding structure 404 formed by the second wafer 400 is disposed on the first wafer 300.

[0040] In the present embodiment shown in the figure, the step of disposing the light-shielding structure 404 formed by the second wafer 400 on the first wafer 300 includes: first bonding or oxide layer bonding the second wafer 400 to the first wafer 300, thinning the second wafer 400 and removing the substrate 402, and then etching the second wafer 400 to form the light-shielding structure 404. Preferably, when the second wafer 400 is bonded to the first wafer 300 by oxide layer bonding, a silicon dioxide layer (not shown) is formed on the infrared cut-off filter film 403 to improve the performance of oxide layer bonding.

[0041] In other preferred embodiments not shown, the step of disposing the light-shielding structure 404 formed by the second wafer 400 on the first wafer 300 may also include: first thinning and etching the second wafer 400 to form the light-shielding structure 404, and then bonding the light-shielding structure 404 to the first wafer 300.

[0042] By the above method, the light-shielding structure 404 formed by the second wafer 400 can be disposed on the first wafer 300, thereby reducing the light crosstalk between adjacent pixel units in the photosensitive area.

[0043] See Figure 11 , in order to further improve the light-shielding effect of the light-shielding structure 404, preferably, a first light-shielding layer 405 formed of, for example, a black glue material may be further disposed on the surface of the light-shielding structure 404 to further reduce the signal interference caused by light crosstalk.

[0044] See Figures 12-13 , a light-transmitting layer 406 is disposed on the light-shielding structure 404, for example, the light-transmitting layer 406 is disposed on the light-shielding structure 404 by bonding or coating or spraying; a plurality of microlenses 407 are formed on the light-transmitting layer 406; the first wafer 300 is thinned; the light-transmitting layer 406 corresponding to the pad area 302 is removed to expose the pad area 302; thereby forming as Figure 13 shown optical fingerprint device.

[0045] Preferably, a second light-shielding layer 408 formed of, for example, a black glue material may be further formed between the microlenses 407 to further reduce the signal interference caused by light crosstalk.

[0046] Embodiment 2

[0047] Figures 14-23 It is a process schematic diagram of a method for forming an infrared cut-off filter film in an optical fingerprint device according to another preferred embodiment of the present invention.

[0048] Refer to Figure 14 , a first wafer 100 formed with a plurality of image sensors is provided. The image sensors include a pad region 102 and a photosensitive region 103, and the pad region 102 and the photosensitive region 103 are spaced apart by a dotted line in the figure.

[0049] Refer to Figure 15 , a second wafer 200 is provided, and a jig 201 covers a portion of the second wafer 200 corresponding to the pad region 102 of the image sensor. Preferably, the second wafer 200 is closely attached to the jig 201 through a clamping structure or a magnetic structure or a temporary bonding adhesive to improve the film forming quality. After forming the infrared cut-off filter film, the clamping structure or the magnetic structure or the temporary bonding adhesive is removed. In this embodiment, a magnetic structure is taken as an example. The second wafer 200 is placed on a magnetic substrate 202 (the substrate 202 can be integral or split), and the jig 201 and the substrate 202 adsorb each other to clamp the second wafer 200 in the middle.

[0050] Refer to Figure 16 , an infrared cut-off filter film 203 is formed on a portion of the second wafer 200 corresponding to the photosensitive region 103 of the image sensor.

[0051] Refer to Figure 17 , after forming the infrared cut-off filter film 203, the jig 201 is removed. For example, a tool with stronger magnetism than the substrate 202 can be used to remove the jig 201.

[0052] Refer to Figures 18-20 , a light shielding structure 204 formed by the second wafer 200 is disposed on the first wafer 100.

[0053] In this embodiment shown in the figure, the step of disposing the light shielding structure 204 formed by the second wafer 200 on the first wafer 100 includes: first bonding or oxide layer bonding the second wafer 200 to the first wafer 100, removing the substrate 202, and then etching the second wafer 200 to form the light shielding structure 204. Preferably, when the second wafer 200 is bonded to the first wafer 100 by oxide layer bonding, a silicon dioxide layer (not shown) is formed on the infrared cut-off filter film 203 to improve the performance of oxide layer bonding.

[0054] In other preferred embodiments not shown, the step of disposing the light shielding structure 204 formed by the second wafer 200 on the first wafer 100 may also include: first etching the second wafer 200 to form the light shielding structure 204, and then bonding the light shielding structure 204 to the first wafer 100.

[0055] Through the above method, the light shielding structure 204 formed by the second wafer 200 can be disposed on the first wafer 100, thereby reducing the light crosstalk between adjacent pixel units in the photosensitive region.

[0056] Different from the first embodiment, in this embodiment, since the second wafer 200 is adsorbed to the substrate 202 through the jig 201 and clamped in the middle, the second wafer 200 can use an ultra-thin wafer (thickness less than 200 μm) that is thinner than a conventional wafer (thickness about 700 μm). For example, first temporarily bond a support carrier to the second wafer 200, then thin the second wafer 200. After removing the support carrier, adsorb the thinned second wafer 200 to the substrate 202 through the jig 201 to clamp the second wafer 200 in the middle. An infrared cut-off filter film 203 is formed on the part of the second wafer 200 corresponding to the photosensitive area 103 of the image sensor. After the first wafer 100 and the second wafer 200 are bonded to each other, there is no need to thin the second wafer 200.

[0057] In addition, in this embodiment, before the step of setting the second wafer 200, the jig 201 is provided to cover the part of the second wafer 200 corresponding to the pad area 102 of the image sensor, and an infrared cut-off filter film is formed on the part of the second wafer 200 corresponding to the photosensitive area 103 of the image sensor; in other preferred embodiments not shown, it is also possible to provide the jig 201 to cover the part of the second wafer 200 corresponding to the pad area 102 of the image sensor after the step of setting the second wafer 200, and an infrared cut-off filter film is formed on the part of the second wafer 200 corresponding to the photosensitive area 103 of the image sensor, both of which can achieve the purpose of avoiding the pad area of the image sensor for the infrared cut-off filter film.

[0058] See Figure 21 , in order to further improve the light blocking effect of the light blocking structure 204, preferably, a first light blocking layer 205 formed of, for example, a black glue material can be further provided on the surface of the light blocking structure 204 to further reduce the signal interference caused by light crosstalk.

[0059] See Figures 22-23 , a light-transmitting layer 206 is provided on the light blocking structure 204, for example, the light-transmitting layer 206 is provided on the light blocking structure 204 by means of bonding, coating, spraying, etc.; a plurality of microlenses 207 are formed on the light-transmitting layer 206; the first wafer 100 is thinned; the light-transmitting layer 206 corresponding to the pad area 102 is removed to expose the pad area 102; thus, an optical fingerprint device as shown in Figure 23 is formed.

[0060] Preferably, a second light blocking layer 208 formed of, for example, a black glue material can be further formed between the microlenses 207 to further reduce the signal interference caused by light crosstalk.

[0061] Embodiment Three

[0062] Figures 24-30Schematic diagram of the process of forming an infrared cut-off filter film in an optical fingerprint device according to another preferred embodiment of the present invention.

[0063] Refer to Figure 24 , a first wafer 500 formed with a plurality of image sensors is provided. The image sensors include a pad area 502 and a photosensitive area 503, and the pad area 502 and the photosensitive area 503 are spaced apart by a dashed line in the figure.

[0064] Refer to Figures 25-26 , a light-shielding structure 604 is disposed on the first wafer 500. Preferably, a second wafer 600 is provided, and the light-shielding structure 604 formed by the second wafer 600 is disposed on the first wafer 500.

[0065] In the present embodiment shown in the figure, the step of disposing the light-shielding structure 604 formed by the second wafer 600 on the first wafer 500 includes: first bonding or oxide layer bonding the second wafer 600 to the first wafer 500, thinning the second wafer 600, and then etching the second wafer 600 to form the light-shielding structure 604.

[0066] In other preferred embodiments not shown, the step of disposing the light-shielding structure 604 formed by the second wafer 600 on the first wafer 500 may also include: first thinning and etching the second wafer 600 to form the light-shielding structure 604, and then bonding the light-shielding structure 604 to the first wafer 500.

[0067] By the above methods, the light-shielding structure 604 formed by the second wafer 600 can be disposed on the first wafer 500, thereby reducing the light crosstalk between adjacent pixel units in the photosensitive area.

[0068] In order to further improve the light-shielding effect of the light-shielding structure 604, preferably, a first light-shielding layer 605 formed of, for example, a black glue material may be further disposed on the surface of the light-shielding structure 604 to further reduce the signal interference caused by light crosstalk.

[0069] Refer to Figure 27, provide a light-transmitting layer 606, and provide a jig 601 to cover the part of the light-transmitting layer 606 corresponding to the pad area 502 of the image sensor. Preferably, the light-transmitting layer 606 and the jig 601 are closely attached to each other through a clamping structure, a magnetic structure, or a temporary bonding adhesive to improve the film-forming quality. After forming the infrared cut-off filter film, remove the clamping structure, the magnetic structure, or the temporary bonding adhesive. In this embodiment, the magnetic structure is taken as an example. The light-transmitting layer 606 is placed on a magnetic substrate 602 (the substrate 602 can be integral or split). The jig 601 and the substrate 602 adsorb each other, thereby clamping the light-transmitting layer 606 in the middle. After forming the infrared cut-off filter film 603 on the part of the light-transmitting layer 606 corresponding to the photosensitive area 503 of the image sensor, remove the jig 601. For example, a tool with stronger magnetism than the substrate 602 can be used to remove the jig 601.

[0070] See Figure 28 , provide a light-transmitting layer 606 with an infrared cut-off filter film 603 on the light-blocking structure 604. For example, the light-transmitting layer 606 is provided on the light-blocking structure 604 by an adhesive method. After the light-blocking structure 604 and the light-transmitting layer 606 are combined with each other, remove the substrate 602.

[0071] In addition, in this embodiment, before the step of providing the light-transmitting layer 606, a jig 601 is provided to cover the part of the light-transmitting layer 606 corresponding to the pad area 502 of the image sensor, and an infrared cut-off filter film is formed on the part of the light-transmitting layer 606 corresponding to the photosensitive area 503 of the image sensor; in other preferred embodiments not shown, after the step of providing the light-transmitting layer 606, a jig 601 can also be provided to cover the part of the light-transmitting layer 606 corresponding to the pad area 502 of the image sensor, and an infrared cut-off filter film is formed on the part of the light-transmitting layer 606 corresponding to the photosensitive area 503 of the image sensor, both of which can achieve the purpose of avoiding the pad area of the image sensor for the infrared cut-off filter film.

[0072] See Figure 29 , form a plurality of microlenses 607 on the light-transmitting layer 606; thin the first wafer 500; remove the light-transmitting layer 606 corresponding to the pad area 502 to expose the pad area 502; thus form an Figure 30 optical fingerprint device as shown.

[0073] Preferably, a second light-blocking layer 608 formed of, for example, a black glue material can also be formed between the microlenses 607 to further reduce the signal interference caused by light crosstalk.

[0074] In summary, in the method for forming an infrared cut-off filter film in the optical fingerprint device of the present invention, by covering the part corresponding to the pad area of the image sensor with a jig and forming an infrared cut-off filter film on the part corresponding to the photosensitive area of the image sensor, the purpose of avoiding the pad area of the image sensor by the infrared cut-off filter film is achieved, so as not to affect the electrical connection performance of the pad area. Since the jig can be reused, the process time and material cost required for the lithography step are saved, the production efficiency is improved, the production capacity is increased, and the manufacturing cost is reduced.

[0075] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any case, the embodiments should be regarded as exemplary and non-limiting. In addition, obviously, the word "including" does not exclude other elements and steps, and the term "a" does not exclude a plurality. A plurality of elements stated in the apparatus claims can also be implemented by one element. The words first, second, etc. are used to denote names and do not denote any particular order.

Claims

1. A method for forming an infrared cut-off filter film in an optical fingerprint device, characterized in that, The method includes the following steps: Provide a first wafer formed with a plurality of image sensors. The image sensors include pad regions and photosensitive regions. Provide a light shielding structure formed by a second wafer on the first wafer, and provide a light transmissive layer on the light shielding structure. Provide a fixture. By means of a magnetic structure, the fixture is closely attached to the first wafer, the second wafer or the light transmissive layer. The fixture covers the part of the first wafer, the second wafer or the light transmissive layer corresponding to the pad regions of the image sensors. Form an infrared cut-off filter film on the part of the first wafer, the second wafer or the light transmissive layer corresponding to the photosensitive regions of the image sensors. After forming the infrared cut-off filter film, remove the magnetic structure to remove the fixture.

2. The method for forming an infrared cut-off filter film in the optical fingerprint device according to claim 1, wherein Place the first wafer on a magnetic substrate. The fixture and the substrate adsorb each other to clamp the first wafer in the middle. After forming the infrared cut-off filter film, remove the fixture. After the first wafer and the light shielding structure are combined with each other, remove the substrate.

3. The method for forming an infrared cut-off filter film in the optical fingerprint device according to claim 1, characterized in that, Place the second wafer on a magnetic substrate. The fixture and the substrate adsorb each other to clamp the second wafer in the middle. After forming the infrared cut-off filter film, remove the fixture. After the first wafer and the second wafer are combined with each other, remove the substrate.

4. The method for forming an infrared cut-off filter film in the optical fingerprint device according to claim 3, characterized in that, The step of providing the second wafer includes temporarily bonding the second wafer to a support carrier, then thinning the second wafer, removing the support carrier, forming an infrared cut-off filter film on the part of the second wafer corresponding to the photosensitive regions of the image sensors, and without thinning the second wafer after the first wafer and the second wafer are combined with each other.

5. The method for forming an infrared cut-off filter film in the optical fingerprint device according to claim 1, wherein Place the light transmissive layer on a magnetic substrate. The fixture and the substrate adsorb each other to clamp the light transmissive layer in the middle. After forming the infrared cut-off filter film, remove the fixture. After the light shielding structure and the light transmissive layer are combined with each other, remove the substrate.

Images