Light sensor structure and packaging method thereof

Abstract

A photosensor structure and its packaging method are disclosed. The photosensor structure includes a light-emitting element, a photosensitive element, an opaque molding material, an insulating layer, and a connection circuit. The opaque molding material covers the light-emitting element and the photosensitive element, and has a through-hole forming an electrical connection structure. The insulating layer is disposed on the bottom surface of the light-emitting element, and a plurality of connection pads are disposed on the side of the insulating layer away from the light-emitting element and the photosensitive element. The connection pads are electrically connected to the contacts on the bottom surface of the light-emitting element via a connection circuit, and the connection pads are electrically connected to the contacts on the photosensitive surface of the photosensitive element via the connection circuit and the electrical connection structure in the through-hole.

Description

Technical Field

[0001] This invention relates to a photosensitive sensor structure and its packaging method, and more particularly to a method for packaging a photosensitive sensor structure comprising a light-emitting element and a photosensitive element. Prior Technology

[0002] Proximity sensors (PS) and ambient light sensors are widely used in portable mobile devices such as cell phones and other consumer electronic devices. Proximity sensors are used to detect the distance between the user's face or other objects and the electronic device; ambient light sensors are used in electronic devices to sense the intensity of ambient light. Both proximity sensors and ambient light sensors require photosensitive elements, and proximity sensors generally also require light-emitting elements (such as infrared emitters or laser light emitters).

[0003] In existing technologies, to encapsulate a photosensor structure containing a light-emitting element and a photosensitive element, wire-bonded light-emitting and photosensitive elements are typically selected and placed together on a semiconductor substrate. These elements are then sealed within a molded transparent molding material to protect them without affecting light transmission. Further optical structures or light-shielding covers are then added to meet specific product requirements.

[0004] To meet the design trends of full-screen displays in consumer electronics, miniaturization of photosensitive structures is a top priority in product development, and manufacturers are trying every means to reduce the overall size of photosensitive structures. However, in existing technologies, the light-emitting element and photosensitive element that are wire-bonded already occupy a certain amount of space, and the required transparent molding material also takes up space. This limits the extent to which photosensitive structures packaged using existing technologies can be reduced in size.

[0005] Given the aforementioned shortcomings, it is necessary to improve the structure and manufacturing process of the photosensor to achieve overall miniaturization, so as to better meet the needs of practical applications. Summary of the Invention

[0006] One of the main objectives of this invention is to provide a photosensor structure and its packaging method. By improving the structure and manufacturing process of the photosensor, the overall size of the photosensor structure packaged using the embodiments of this invention can be significantly reduced, achieving the goal of overall miniaturization. Moreover, it eliminates the need for transparent molding materials, simplifying the manufacturing process while maintaining good reliability.

[0007] This invention discloses a photosensitive sensor structure, comprising a light-emitting element including a light-emitting surface and a bottom surface, the light-emitting surface and the bottom surface being located on opposite sides of the light-emitting element in a first direction; a photosensitive element including a photosensitive surface; an opaque molding material covering the light-emitting element and the photosensitive element, the opaque molding material having a perforation forming an electrical connection structure therein; an insulating layer disposed on the bottom surface of the light-emitting element, the insulating layer having a plurality of connecting pads disposed on the side away from the light-emitting element and the photosensitive element in the first direction; and a connecting line, the connecting pads being electrically connected to the contacts on the bottom surface of the light-emitting element via the connecting line, and the connecting pads being electrically connected to the contacts on the photosensitive surface of the photosensitive element via the connecting line and the electrical connection structure in the perforation; wherein at least one of the light-emitting element or the photosensitive element is a bare die, such that a bare die interface is formed between the opaque molding material and the light-emitting element or the photosensitive element.

[0008] This invention discloses a method for packaging a photosensitive structure, which can be used to package a photosensitive structure including a light-emitting element and a photosensitive element. The light-emitting element includes a light-emitting surface and a bottom surface, which are located on opposite sides of the light-emitting element in a first direction. The photosensitive element includes a photosensitive surface. The packaging method includes: fixing the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element to a carrier plate along the first direction; covering the light-emitting element and the photosensitive element with an opaque molding material; and removing a portion of the opaque molding material along the first direction to expose the light-emitting element. The bottom surface is exposed; the carrier plate is removed and a perforation is made in the opaque molding material, the perforation penetrating both sides of the opaque molding material in the first direction, and an electrical connection structure is formed in the perforation; a connection line and an insulating layer are made, and a plurality of connection pads are provided on the side of the insulating layer away from the light-emitting element and the photosensitive element in the first direction; wherein, the connection pads are electrically connected to the contacts on the bottom surface of the light-emitting element through the connection line, and the connection pads are electrically connected to the contacts on the photosensitive surface of the photosensitive element through the connection line and the electrical connection structure in the perforation.

[0009] The present invention also discloses a photosensitive sensor structure, which is packaged using the above-described photosensitive sensor structure packaging method. Simple Explanation of the Diagram

[0010] Figure 1A is a schematic diagram of the light-emitting element and the steps for fixing the photosensitive element. Figure 1B is a schematic diagram of the steps involved in making an opaque molding material. Figure 1C is a schematic diagram of the steps for removing the opaque molding material. Figure 1D is a schematic diagram of the removal steps of a carrier plate. Figure 1E is a schematic diagram of the perforation procedure. Figure 1F is a schematic diagram of the steps for fabricating the connecting lines, insulation layer, and connecting pads. Figure 1G is a schematic diagram of the steps involved in making the cover. Figure 2 is a top view of the light sensor structure. Figure 3 is a bottom view of the light sensor structure. Implementation

[0011] Please refer to Figures 1A-1G, which illustrate a photosensor structure packaging method according to an embodiment of the present invention. First, at least one light-emitting element and at least one photosensitive element are prepared. For ease of explanation, this embodiment uses a light-emitting element 1 and at least one photosensitive element 2 as examples. At least one of the light-emitting element 1 and the photosensitive element 2 is a die, and preferably both are dies. A die refers to a component that has only undergone wafer dicing and has not yet undergone wire bonding or other packaging processes. The light-emitting element 1 can be a light-emitting diode (LED) or a laser diode (EEL, VCSEL, etc.), and it has a light-emitting surface 11. The side of the light-emitting element 1 away from the light-emitting surface 11 in a first direction X is a bottom surface 12. Taking a vertical cavity surface-emitting laser (VCSEL) element as an example, the contacts of the light-emitting element 1 are typically located on the light-emitting surface 11 and the bottom surface 12, respectively. Furthermore, in embodiments of the present invention, VSCEL components fabricated using flip-chip technology can be selected.

[0012] The photosensitive element 2 can be integrated into an application-specific integrated circuit (ASIC) so that it can simultaneously include a photodiode and arithmetic circuitry (e.g., analog-to-digital conversion circuitry or other arithmetic circuitry for proximity sensors and / or ambient light sensors). However, if the user has other design considerations, the photosensitive element 2 can also contain only a photodiode. Generally, the photodiode is formed by fabricating a PN junction or PIN diode on a photosensitive surface 21, and the contacts of the photodiode or the aforementioned arithmetic circuitry are usually also located on the photosensitive surface 21. Accordingly, the side of the photosensitive element 2 away from the photosensitive surface 21 in the first direction X is a back surface 22, which is typically the wafer back surface and does not have any contacts.

[0013] As shown in Figure 1A, the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2 are fixed downwards along the first direction X onto a carrier plate 3. The carrier plate 3 can be a film or other removable material. In this embodiment, the carrier plate 3 includes a pyrolytic layer 31 and a carrier layer 32. The pyrolytic layer 31 can be made of thermal release tape and is disposed above the carrier layer 32 along the first direction X. In other words, the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2 are fixed on the pyrolytic layer 31.

[0014] Next, as shown in Figure 1B, an opaque molding material 4 is used to encapsulate the light-emitting element 1 and the photosensitive element 2. In this embodiment, the opaque molding material 4 is selected from materials such as epoxy resin, silicone, a mixture of resin and silicone, or acrylic adhesive. The opaque molding material 4 can be a material that is inherently opaque, such as black epoxy resin, or it can be made opaque by doping with dyes, carbon black, silicon dioxide, or titanium dioxide as fillers. Thus, the opaque molding material 4 has a light-shielding effect and, after curing, can protect the light-emitting element 1 and the photosensitive element 2.

[0015] It should be noted that the "opaque" described in this application specification and the claims does not necessarily mean blocking all light. Any light within the wavelength range that the photosensitive element 2 can receive can be considered opaque.

[0016] As previously explained, the contacts of the light-emitting element 1 can be distributed on its bottom surface 12, while the back surface 22 of the photosensitive element 2 is usually not provided with contacts. Therefore, as shown in Figure 1C, a portion of the opaque molding material 4 can be removed from above along the first direction X by means of grinding or etching to expose the bottom surface 12 of the light-emitting element 1.

[0017] It should be noted that if a grinding method is used to remove the opaque molding material 4, and if the height of the light-emitting element 1 is greater than the height of the photosensitive element 2 in the first direction X, then the above steps as shown in Figure 1C will not affect the photosensitive element 2. Conversely, if a different type of light-emitting element 1 is used, resulting in the height of the light-emitting element 1 being less than the height of the photosensitive element 2 in the first direction X, when the bottom surface 12 of the light-emitting element 1 is exposed during grinding, the photosensitive element 2 may also be thinned. In order to avoid the light signal from directly passing through the back surface 22 of the photosensitive element 2 and causing loss, the technology of the applicant's previous patent application No. 202211459 can be referred to to create an additional reflective layer on the back surface 22. However, the relevant technical content is not within the scope of the invention of this application, so it will not be described in detail.

[0018] As shown in Figure 1D, the carrier plate 3 is removed. Specifically, in this embodiment, the pyrolytic layer 31 of the carrier plate 3 can be made of pyrolytic adhesive, thus the carrier plate 3 can be easily removed by heating. However, if the carrier plate 3 is made of other materials, it may be necessary to use adhesive remover or other methods to completely remove the carrier plate 3.

[0019] As shown in Figure 1E, at least one perforation 41 is formed in the opaque molding material 4, the perforation 41 penetrating both sides of the opaque molding material 4 in the first direction X. An electrical connection structure 42 is formed in the perforation 41, for example, the electrical connection structure 42 can be a through mold via (TMV) formed by laser drilling. Of course, the electrical connection structure 42 in the perforation 41 can also be made using a conventional vertical via (VIA).

[0020] Alternatively, the steps in Figure 1D and Figure 1E can be interchanged. For example, a perforation can be made directly through the carrier plate 3 and the opaque molding material 4, and then the carrier plate 3 can be removed. Alternatively, at least one perforation 41 can be formed on the opaque molding material 4.

[0021] In this embodiment, at least one of the light-emitting element 1 and the photosensitive element 2 is a bare die, and preferably both are bare dies. Therefore, as shown in Figure 1F, connection lines 51 and connection pads 52 need to be fabricated to connect to the contacts of the light-emitting element 1 and the photosensitive element 2. Specifically, the photosensor structure is provided with several connection pads 52 as its input / output interface with the electronic device, and these connection pads 52 need to be individually connected to the contacts of the light-emitting element 1 or the photosensitive element 2. The contacts of the photosensitive element 2 are usually located on the photosensitive surface 21, however, the connection pads 52 are located on different sides of the photosensitive surface 21 in the first direction X. Therefore, the connection lines 51 fabricated by the redistribution layer (RDL) can be used to electrically connect the electrical connection structure 42 located in a through-hole 41 to electrically connect the connection pads 52 located on both sides in the first direction X to the contacts of the photosensitive surface 21. When fabricating the connection line 51 using a redistribution layer, it is typically paired with an insulating layer 6 made of a polyimide dielectric layer (PI) film to form one or more wiring structures. The insulating layer 6 also serves to secure the connection pad 52. Alternatively, the aforementioned connection line 51 and insulating layer 6 can also be fabricated using other methods.

[0022] On the other hand, the connecting line 51 also electrically connects to the light-emitting element 1. When the contacts of the light-emitting element 1 are only located on the bottom surface 12, the connecting pad 52 can easily be electrically connected to the contacts on the bottom surface 12 via the connecting line 51. In this case, the number of perforations 41 on the opaque molding material 4 can be a single one. However, as mentioned above, in this embodiment, using a VCSEL element as the light-emitting element 1, the contacts of the light-emitting element 1 are typically located on the light-emitting surface 11 and the bottom surface 12, respectively, while the connecting pad 52 is located on a different side from the light-emitting surface 11 in the first direction X. Therefore, it is necessary to electrically connect the connecting structure 42 located in another perforation 41 via the connecting line 51 to electrically connect the connecting pads 52 located on both sides in the first direction X to the contacts on the light-emitting surface 11.

[0023] In fact, the photosensor structure shown in Figure 1F can be considered a finished product and can be used as a proximity sensor or ambient light sensor. However, in proximity sensor applications, to avoid crosstalk signals affecting the sensing results, it is usually desirable to provide additional structures such as covers to prevent the light emitted by the light-emitting element 1 from being transmitted to the photosensitive element 2 without being reflected by external objects. For this purpose, as shown in Figure 1G, a cover 7 can be additionally provided on the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2. The cover 7 has a first opening 71 and a second opening 72. The first opening 71 connects to the light-emitting surface 11, and the second opening 72 connects to the photosensitive surface 21 to allow light to pass through. In this way, the cover 7, together with the opaque molding material 4, can restrict the light transmission path and effectively reduce crosstalk signal components. In addition, the size of the second opening 72 can also be used to limit the light-receiving angle of the ambient light sensor.

[0024] It is worth noting that the formation and assembly of the cover 7 can take many forms, which cannot all be listed and described. However, as mentioned above, in this embodiment of the invention, a polyimide dielectric layer can be used to fabricate the insulating layer 6. Polyimide is a type of polymer with repeating polyimide units, and depending on its type, it can be transparent or opaque. If the insulating layer 6 is opaque, the photosensor structure packaging method of this embodiment of the invention can directly use the same polyimide dielectric layer to fabricate the cover 7. This can minimize the process difficulty and complexity of the packaging method. The only thing to note is that in Figure 1G, if the photosensor structure is not flipped when fabricating the connecting line 51, the connecting pad 52, and the insulating layer 6, the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2 will remain facing downwards along the first direction X. Therefore, before performing the step of making the cover 7 in Figure 1F, it may be necessary to flip the photosensor structure so that the light-emitting surface 11 of the light-emitting element 1 and the light-sensitive surface 21 of the photosensitive element 2 are facing upward along the first direction X to facilitate the operation.

[0025] The photosensitive sensor structure shown in Figure 1G can also be considered a finished product and can be used as a proximity sensor or ambient light sensor. Furthermore, Figure 2 shows a top view of this photosensitive sensor structure, which reveals that the top view of the photosensitive sensor structure is the cover 7 and the second opening 72 and the first opening 71 for receiving and emitting light. Figure 3 shows a bottom view of this photosensitive sensor structure, which reveals that the bottom view of the photosensitive sensor structure is several connection pads 52 serving as input / output interfaces with electronic devices. Therefore, the photosensitive sensor structure packaged using the embodiments of the present invention can completely replace photosensitive sensor structures manufactured using existing packaging technologies.

[0026] However, the photosensor structure packaged using the embodiments of the present invention differs significantly from the prior art. Specifically, in this embodiment, at least one of the light-emitting element 1 and the photosensitive element 2 is a bare die, and preferably both are bare dies. Therefore, the photosensor structure of the embodiments of the present invention has at least one bare die interface S. Specifically, referring to Figures 1F and 1G, when both the light-emitting element 1 and the photosensitive element 2 are bare dies, there is one bare die interface S between the light-emitting element 1 and the opaque molding material 4, and another bare die interface S between the photosensitive element 2 and the opaque molding material 4. This means that in the embodiments of the present invention, the bare dies of the light-emitting element 1 and the photosensitive element 2 can directly contact the opaque molding material 4. In contrast, in the prior art, pre-wire-bonded light-emitting elements and photosensitive elements are used for packaging, so the distance between the bare dies of the light-emitting element and the photosensitive element and the external packaging structure is only separated by the space of the wire bonding sealant. Not to mention, as previously described, existing technologies typically seal the light-emitting element and the photosensitive element in a transparent molding material, which further separates the bare die of the light-emitting element and the photosensitive element from the external packaging structure by the space of the transparent molding material.

[0027] Furthermore, in this embodiment, although both the light-emitting element 1 and the photosensitive element 2 can be bare dies, during the packaging process, the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2 are first fixed downwards on the carrier plate 3. Therefore, the opaque molding material 4 subsequently produced will not affect the light-emitting surface 11 of the light-emitting element 1 and the photosensitive surface 21 of the photosensitive element 2, thus ensuring that the optical and electrical characteristics of the packaged photosensor structure are good.

[0028] Therefore, it can be seen that the overall size of the photosensor structure packaged using the embodiments of the present invention can be significantly reduced compared to the prior art. In one practical example, the photosensor structure that originally required approximately 5.5*2.4*1 mm can be miniaturized to approximately 4*2*0.2 mm after being packaged using the embodiments of the present invention, thus achieving miniaturization. Furthermore, the embodiments of the present invention eliminate the need to protect the light-emitting element and the photosensitive element with a transparent molding material, effectively simplifying the manufacturing process and reducing packaging costs. In addition, the photosensor structure packaged using the embodiments of the present invention has good reliability, and the reliability of the wafer-level chip-scale package (WLCSP) can reach Level 1.

[0029] In summary, the embodiments of the photosensitive sensor structure and packaging method of the present invention improve the structure and process of the photosensitive sensor, enabling a significant reduction in the overall size of the photosensitive sensor structure packaged using the embodiments of the present invention, thereby achieving the goal of overall miniaturization. Furthermore, it eliminates the need for transparent molding materials, simplifying the manufacturing process while maintaining good reliability.

[0030] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be covered by the present invention.

[0031] 1: Light-emitting element 11: Illuminating surface 12: Bottom surface 2: Photosensitive element 21: Photosensitive surface 22: Back 3: Carrier board 31: Pyrolysis layer 32: Carrier layer 4: Opaque molding material 41: Perforation 42: Electrical connection construction 51: Connection Line 52: Connecting pad 6: Insulation layer 7: Cover 71: First Opening 72: Second opening X: First direction

Claims

1. A photosensor structure, comprising: a light-emitting element including a light-emitting surface and a bottom surface, the light-emitting surface and the bottom surface being located on opposite sides of the light-emitting element in a first direction; a photosensitive element including a photosensitive surface, the photosensitive surface of the photosensitive element and the light-emitting surface of the light-emitting element being located on the same side of the photosensor structure in the first direction; an opaque molding material covering the light-emitting element and the photosensitive element, and the opaque molding material having a perforation forming an electrical connection structure therein; an insulating layer disposed on the bottom surface of the light-emitting element, and the insulating layer having a plurality of connecting pads disposed on a side of the insulating layer away from the light-emitting element and the photosensitive element in the first direction, the connecting pads being on different sides from the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element; and a connecting line, the connecting pads being electrically connected to contacts on the bottom surface of the light-emitting element via the connecting line, and the connecting pads being electrically connected to contacts on the photosensitive surface of the photosensitive element via the connecting line and the electrical connection structure in the perforation; wherein... At least one of the light-emitting element or the photosensitive element is a bare crystal, such that a bare crystal interface is formed between the opaque molding material and the light-emitting element or the photosensitive element; wherein the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element are not polished and are not covered by the opaque molding material.

2. The photosensor structure as described in claim 1, wherein the light-emitting element and the photosensitive element are each a bare die, such that the opaque molding material forms two bare die interfaces with the light-emitting element and the photosensitive element, respectively.

3. The photosensor structure as claimed in claim 1, wherein the opaque molding material has another perforation, in which another electrical connection structure is formed, and the connecting pad is electrically connected to the contact of the light-emitting surface of the light-emitting element via the connecting line and the other electrical connection structure in the other perforation.

4. The photosensor structure as described in claim 1, wherein, It also includes a cover disposed in the first direction on the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element, and the cover is provided with a first opening and a second opening, the first opening communicating with the light-emitting surface and the second opening communicating with the photosensitive surface. .

5. The photosensor structure as described in claim 1, wherein the connection line is composed of a redistribution layer and the insulating layer is composed of a polyimide dielectric layer.

6. The photosensor structure as described in claim 1, wherein the light-emitting element is a vertical cavity surface-emitting laser element.

7. The photosensitive sensor structure as described in claim 1, wherein the photosensitive element includes a back surface, the photosensitive surface and the back surface are located on both sides of the light-emitting element in the first direction, and the back surface is not provided with contacts.

8. A method for packaging a photosensitive structure, for packaging a photosensitive structure including a light-emitting element and a photosensitive element, wherein at least one of the light-emitting element and the photosensitive element is a bare die, the light-emitting element includes a light-emitting surface and a bottom surface, the light-emitting surface and the bottom surface are located on both sides of the light-emitting element in a first direction, and the photosensitive element includes a photosensitive surface, the packaging method comprising: fixing the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element to a carrier plate along the first direction; covering the light-emitting element and the photosensitive element with an opaque molding material; removing a portion of the opaque molding material along the first direction to expose the bottom surface of the light-emitting element; removing the carrier plate and forming a through hole in the opaque molding material, the through hole penetrating the opaque molding material on both sides in the first direction, and forming an electrical connection structure in the through hole; fabricating a connection line and an insulating layer, wherein a plurality of connection pads are disposed on the side of the insulating layer away from the light-emitting element and the photosensitive element in the first direction; wherein... The connecting pad is electrically connected to the contact point on the bottom surface of the light-emitting element via the connecting line, and the connecting pad is electrically connected to the contact point on the photosensitive surface of the photosensitive element via the connecting line and the electrical connection structure in the through hole.

9. The method for packaging a photosensor structure as described in claim 8, wherein the light-emitting element and the photosensitive element are each a bare die.

10. The method for packaging a photosensitive structure as claimed in claim 8, wherein another through-hole is formed in the opaque molding material, and another electrical connection structure is formed in the through-hole, and the connection pad is electrically connected to the contact of the light-emitting surface of the light-emitting element via the connection line and the other electrical connection structure in the other through-hole.

11. The method for packaging a photosensitive structure as described in claim 10, wherein the through-hole is formed by laser drilling and the electrical connection configuration is a conductor through-mold through-hole.

12. The photosensor structure packaging method as described in claim 8, wherein the connection lines are fabricated with a redistribution layer and the insulating layer is fabricated with a polyimide dielectric layer.

13. The photosensor structure packaging method as described in claim 8, further comprising: providing a cover on the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element in the first direction, wherein the cover has a first opening and a second opening, the first opening communicating with the light-emitting surface and the second opening communicating with the photosensitive surface.

14. The photosensor structure packaging method as described in claim 13, wherein the connection lines are fabricated with a redistribution layer, and the insulating layer and the cover are fabricated with a polyimide dielectric layer.

15. The photosensor structure packaging method as described in claim 8, wherein a portion of the opaque molding material is removed by grinding.

16. The photosensor structure packaging method as described in claim 8, wherein the carrier plate includes a pyrolytic layer and a support layer, the pyrolytic layer is disposed on the support layer along the first direction, and the light-emitting surface of the light-emitting element and the photosensitive surface of the photosensitive element are fixed on the pyrolytic layer.

17. A light sensor structure packaged using the light sensor structure packaging method described in claim 8.

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