Fan-out packaging structure and packaging method of thin sensor chip

Abstract

The present invention discloses a fan-out packaging structure for thin sensor chips, comprising a glass carrier assembly, chip-scale packaging, and fan-out packaging. The glass carrier assembly comprises a wafer-level glass carrier and thin glass, with protective tape adhered to the bottom of the thin glass and a metal layer bonded to the surface of the protective tape. This invention relates to the field of semiconductor packaging technology. This fan-out packaging structure for thin sensor chips utilizes a thin package for the image sensor, incorporates an image signal processor within the thin package, and then integrates the two into a single package. Through specialized design and manufacturing methods, the glass, chip, and package are thinned while maintaining sufficient strength to prevent image distortion.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging, and in particular to a fan-out packaging structure of a thin sensor chip and a packaging method thereof, which are applied to image sensors. Background Art

[0002] Currently, there are two main types of image sensor packaging: chip-on-board (COB) and chip-scale packaging (CSP). In COB, the image sensor chip is bonded to an organic substrate surrounded by a molded resin. Wire bonding connects the chip to the substrate, allowing signals to flow from the chip to the substrate. If the image sensor chip does not have an image signal processor (ISP), an ISP (image signal processor) is embedded in the substrate. Glass is bonded to the molded resin, and solder balls are implanted on the back of the substrate. COB packaging is relatively large. If the system requires a smaller footprint, CSP is used. Glass is placed above the chip sensor, and TSVs (through silicon vias) are embedded within the chip to connect the signals between the upper and lower surfaces of the chip. Multiple layers of RDL (redistribution layer) are then fabricated on the back of the chip. Finally, copper bumps are formed at the contact points, and solder balls are implanted on these copper bumps.

[0003] Regardless of whether it is a chip-on-board package or a chip-scale package, the glass thickness is above 250 to 400 microns (um). In some applications, thinner package thickness is required. Current practices make it difficult to further thin the thickness because the thickness and strength of the substrate used in COB (chip on board) and the thickness and strength of the glass used in COB and CSP have limits. If the thickness is too thin, it will easily break during the manufacturing process, and insufficient strength of the package will cause image distortion. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a fan-out packaging structure and packaging method for thin sensor chips. This solves the problems of the thickness and strength of the COB substrate and the thickness and strength of the glass used in COB and CSP, which are limited. Too thin substrates are prone to breakage during the manufacturing process, and insufficient strength of the package body can cause image distortion.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a fan-out packaging structure for a thin sensor chip, including a glass carrier group, a chip-level package and a fan-out package, the glass carrier group including a wafer-level glass carrier and thin glass, the bottom of the thin glass is adhered with a protective tape, and the surface of the protective tape is bonded with a metal layer, the bottom of the thin glass is bonded to the top of the wafer-level glass carrier, the chip-level package is fixed on top of the thin glass by adhesive, the fan-out package is fixed on top of the chip-level package by solder, and the top of the fan-out package is connected with a solder ball.

[0006] As a further solution of the present invention: the thickness of the thin glass is less than 250 microns.

[0007] As a further solution of the present invention: a copper bump is provided on the top of the fan-out package, which is located above the resin package and connected to the solder ball.

[0008] The present invention also discloses a packaging method for a fan-out packaging structure of a thin sensor chip, which specifically includes the following steps:

[0009] Step 1, fan-out packaging: Apply an adhesive layer on the glass carrier, then make the first-side tin-copper contacts and multiple layers of RDL on the adhesive layer, then grow copper pillars on the top layer of RDL, and then adhere the image signal processor (ISP) to the upper RDL. The height of the copper pillars is higher than the thickness of the image signal processor (ISP) chip and the height of the copper bumps on the chip. The copper bumps (cubumps) on the chip surface are facing up, and then the mold is filled with resin. The surface of the mold resin is then ground. Stop grinding when the copper bump-level copper pillars exposed to the resin surface reach the designed thickness, make multiple layers of RDL (redistribution layer), grow copper bumps (second-side contacts) at the contacts of the last layer of RDL, then dissolve the adhesive layer on the glass carrier, remove the glass carrier, and cut the packaged chip into single pieces to obtain a fan-out package;

[0010] Step 2: Chip-Scale Packaging: First, a chip-scale package is fabricated. The first side of the wafer-level thin glass is covered with protective tape, which contains a metal layer. This metal layer prevents laser light from penetrating the glass and damaging the sensor on the chip during debonding. The thin glass (less than 250 microns thick) with the protective tape on its first side (with the protective film) is bonded to a thick wafer-level glass carrier to create a glass carrier assembly. Adhesive is applied to the sensor surfaces around the image sensor wafer, and the image sensor wafer is flip-chip bonded to the side of the thin glass facing away from the wafer-level glass carrier. The backside of the image sensor wafer is then ground to the designed thickness. This supports the thick glass carrier and prevents the thin glass and wafer from shattering during the manufacturing process. Transistor-saturated voltage (TSV) is fabricated on the backside of the image sensor wafer to connect the signals between the upper and lower surfaces of the chip. Multiple layers of RDL (Redistribution Layer) are then fabricated on the backside of the image sensor wafer. Finally, tin-copper bumps are electroplated at the contacts to create a chip-scale package.

[0011] Step 3: Chip-scale packaging and fan-out packaging integration: The tin-copper contacts on the first side of the fan-out package are connected to the tin-copper bumps of the chip-scale package through soldering to form electrical conduction. The copper bumps of the contacts on the second side of the fan-out package are facing upwards, and the mold is filled with resin to obtain a resin package. The surface of the molded resin package is polished until the copper bumps of the contacts on the second side of the fan-out package are exposed and reach the designed thickness. Multiple layers of RDL are made, and copper bumps are grown at the contacts of the last layer of RDL. Solder balls are planted on the copper bumps, and laser scanning is irradiated through the glass carrier. The image sensor chip and glass are very thin, but they are supported by the molding resin and fan-out package. The strength of the entire package is sufficient to prevent image blur and deformation, which solves the problem that the thickness and strength of the substrate used in COB, the thickness and strength of the glass used in COB and CSP are limited. If it is too thin, it will easily break during the process, and the strength of the package is not enough, which will cause image deformation.

[0012] As a further solution of the present invention: the height of the copper pillar in step 1 is higher than the thickness of the image signal processor chip and the height of the copper bumps on the chip.

[0013] As a further solution of the present invention: the grinding is stopped in the step 1 after the surface of the copper pillar at the copper bump level exposed from the resin reaches a designed thickness.

[0014] As a further solution of the present invention: the glass carrier assembly prepared in step 2 is prepared by gluing the side of the thin glass with the protective tape onto a thick wafer-level glass carrier.

[0015] As a further solution of the present invention, in step three, the glass carrier assembly and the protective tape are removed and the glass carrier assembly is penetrated by laser scanning to separate the adhesive between the glass carrier assembly and the thin glass.

[0016] Compared with the prior art, the present invention has the following advantages: by using a thin package for the image sensor, the image signal processor is also built into the thin package, and then the two are integrated into a package. Through special design and process methods, the glass, chip, and package can be made thinner while having sufficient strength to prevent image distortion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the preparation state of the present invention.

[0018] Figure 2 It is a schematic structural diagram of the fan-out package of the present invention.

[0019] Figure 3 It is a structural schematic diagram of the finished product of the present invention.

[0020] In the figure: 1. Chip-level packaging; 2. Fan-out packaging; 3. Wafer-level glass carrier; 4. Thin glass; 5. Protective tape; 6. Metal layer; 7. Resin packaging; 8. Solder balls; 9. Adhesive; 10. Solder. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0022] See also Figure 1 - Figure 3 The present invention provides a technical solution: a fan-out packaging structure for a thin sensor chip, comprising a glass carrier group, a chip-level package 1 and a fan-out package 2. The glass carrier group comprises a wafer-level glass carrier 3 and thin glass 4. A protective tape 5 is adhered to the bottom of the thin glass 4, and a metal layer 6 is bonded to the surface of the protective tape 5. The purpose of the metal layer 6 is to prevent the laser from penetrating the glass and damaging the sensor on the chip when the laser irradiates the glass carrier and debonds. The bottom of the thin glass 4 is bonded to the top of the wafer-level glass carrier 3. The chip-level package 1 is fixed on top of the thin glass 4 by adhesive 9. The fan-out package 2 is fixed on top of the chip-level package 1 by solder 10. The top of the fan-out package 2 is connected with a solder ball 8. Although the sensor chip and glass are very thin, they are supported by the molded resin and the fan-out package 2. The strength of the entire package is sufficient to prevent image blur and deformation.

[0023] The thickness of the thin glass 4 is less than 250 micrometers.

[0024] A copper bump is provided on the top of the fan-out package 2 , which is located above the resin package 7 and connected to the solder ball 8 .

[0025] The present invention also discloses a packaging method for a fan-out packaging structure of a thin sensor chip, which specifically includes the following steps:

[0026] Step 1, Fan-out Package 2: Apply an adhesive layer on the glass carrier, then make the first-side tin-copper contacts and multiple layers of RDL on the adhesive layer, then grow copper pillars on the top layer of the RDL, and then adhere the image signal processor (ISP) chip to the upper RDL layer, with the copper bumps on the chip surface facing up. The height of the copper pillars is higher than the thickness of the image signal processor (ISP) chip and the height of the copper bumps on the chip. Then, mold and pour resin, and then grind the surface of the mold resin. Stop grinding when the copper bump-level copper pillars exposed from the resin reach the designed thickness, and make multiple layers of RDL (redistribution layer). Grow copper bumps (second-side contacts) at the contacts of the last layer of RDL. Then dissolve the adhesive layer on the glass carrier, remove the glass carrier, and cut the packaged chip into individual pieces to obtain Fan-out Package 2.

[0027] Step 2, Chip-Scale Package 1: First, chip-scale package 1 is produced. The first side of wafer-level thin glass 4 is provided with protective tape 5, which has a metal layer 6. The purpose of the metal layer 6 is to prevent laser light from penetrating the glass and damaging the sensor on the chip when the glass carrier is debonded. The thin glass 4 (less than 250 microns thick) with the first side (with protective tape 5) is adhered to a thick wafer-level glass carrier 3 to form a glass carrier assembly. Adhesive 9 is applied to the sensor surface around the image sensor wafer. The image sensor wafer is then flip-chip bonded to the side of the thin glass 4 facing away from the wafer-level glass carrier 3. The back of the image sensor wafer is then ground to the designed thickness. With the thick glass carrier as support, the thin glass 4 and the thin wafer will not break during the manufacturing process. Transistor-saturated voltage (TSV) is formed on the back of the image sensor wafer to connect the upper and lower surface signals of the chip. Then, multiple layers of RDL redistribution layers are formed on the back of the image sensor wafer. Finally, tin-copper bumps are electroplated at the contact points to produce chip-scale package 1.

[0028] Step 3: Integrate the chip-scale package 1 and the fan-out package 2: The tin-copper contacts on the first side of the fan-out package 2 are connected to the tin-copper bumps on the chip-scale package 1 by soldering 10 to form electrical conduction. After welding to form electrical conduction, the copper bumps on the contacts on the second side of the fan-out package 2 are facing upwards, and the resin is molded and poured into the resin package 7. The surface of the molded resin package 7 is ground until the copper bumps on the contacts on the second side of the fan-out package 2 are exposed and reach the designed thickness. Multiple layers of RDL are made, and copper bumps are grown at the contacts of the last layer of RDL. Solder balls 8 are planted on the copper bumps. Laser scanning is performed. The beam penetrates the glass carrier assembly, separating the adhesive 9 between the glass carrier assembly and the thin glass 4. The wafer-level glass carrier 3, protective tape 5, and metal layer 6 are then removed, and the wafer is cut into individual pieces, completing the process. Although the image sensor chip and glass are very thin, they are supported by the molded resin and fan-out package 2. The strength of the entire package is sufficient to prevent image blur and distortion. This solves the problem of the thickness and strength of the COB substrate, the thickness and strength of the glass used in COB and CSP having limits, and the easy breakage during the process due to excessive thinness, and the insufficient strength of the package causing image distortion.

[0029] In step 1, the height of the copper pillar is higher than the thickness of the image signal processor chip and the height of the copper bumps on the chip.

[0030] The grinding is stopped after the copper pillars at the copper bump level in step 1 are exposed from the resin surface and reach the designed thickness.

[0031] The glass carrier assembly in step 2 is prepared by gluing the thin glass 4 with the protective tape 5 on the thick wafer-level glass carrier 3 .

[0032] In step three, the glass carrier set and the protective tape 5 are removed and the glass carrier set is penetrated by laser scanning to separate the adhesive 9 between the glass carrier set and the thin glass 4 .

[0033] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A packaging method for a fan-out packaging structure of a thin sensor chip, characterized by: The following steps are involved: Step 1, fan-out package (2) preparation: brush an adhesive layer on the glass carrier, then make the first side tin-copper contacts and multiple layers of RDL on the adhesive layer, then grow copper pillars on the top layer of RDL, then bond the image signal processor to the upper layer of RDL, with the copper bumps on the chip surface facing up, then mold and fill with resin, then grind the surface of the mold resin, make multiple layers of RDL, grow copper bumps at the contacts of the last layer of RDL, then dissolve the adhesive layer on the glass carrier, remove the glass carrier, and cut the packaged chip into single pieces to obtain fan-out package (2); Step 2: Preparation of chip-level package (1): Prepare a glass carrier assembly, apply adhesive (9) on the surface around the image sensor wafer sensor, then flip-chip bond the image sensor wafer to the side of the thin glass (4) facing away from the wafer-level glass carrier (3), grind the back of the image sensor wafer, and make TSV on the back of the image sensor wafer to connect the upper and lower surface signals of the chip, then make multiple layers of RDL redistribution layer on the back of the image sensor wafer, and finally electroplate tin-copper bumps at the contact points to obtain chip-level package (1); Step 3: Integrate the chip-level package (1) and the fan-out package (2): The tin-copper contacts on the first side of the fan-out package (2) are connected to the tin-copper bumps of the chip-level package (1) by soldering (10) to form electrical conduction, the copper bumps of the contacts on the second side of the fan-out package (2) are facing upward, and the resin package (7) is obtained by molding and filling the resin package (7), and the surface of the molded resin package (7) is ground until the copper bumps of the contacts on the second side of the fan-out package (2) are exposed and reach the designed thickness, and multiple layers of RDL are made, and copper bumps are grown at the contacts of the last layer of RDL, and solder balls (8) are planted at the copper bumps, and the wafer-level glass carrier (3), protective tape (5) and metal layer (6) are removed, and the wafer is cut into single pieces to complete the process.

2. A fan-out packaging structure for a thin sensor chip, packaged using the packaging method for a fan-out packaging structure for a thin sensor chip as claimed in claim 1, comprising a glass carrier assembly, a chip-level package (1) and a fan-out package (2), characterized in that: The glass carrier group includes a wafer-level glass carrier (3) and a thin glass (4), the bottom of the thin glass (4) is adhered with a protective tape (5), and the surface of the protective tape (5) is bonded with a metal layer (6), the bottom of the thin glass (4) is bonded to the top of the wafer-level glass carrier (3), the chip-level package (1) is fixed on the top of the thin glass (4) by adhesive (9), the fan-out package (2) is fixed on the top of the chip-level package (1) by solder (10), the top of the fan-out package (2) is connected with a tin ball (8), and the surfaces of the fan-out package (2) and the chip-level package (1) are both molded with a resin package (7).

3. The fan-out packaging structure of a thin sensor chip according to claim 2, wherein: The thickness of the thin glass (4) is less than 250 micrometers.

4. The fan-out packaging structure of a thin sensor chip according to claim 2, wherein: The fan-out package (2) is provided with a copper bump on the top thereof, which is located above the resin package (7) and connected to the solder ball (8).

5. The packaging method of the fan-out packaging structure of the thin sensor chip according to claim 1, characterized in that: In step 1, the height of the copper pillar is higher than the thickness of the image signal processor chip and the height of the copper bumps on the chip.

6. The packaging method of the fan-out packaging structure of the thin sensor chip according to claim 1, characterized in that: The grinding is stopped after the copper bump-level copper pillar in the step 1 is exposed from the resin surface to a designed thickness.

7. The packaging method of the fan-out packaging structure of the thin sensor chip according to claim 1, characterized in that: The glass carrier assembly prepared in step 2 is prepared by gluing the thin glass (4) with the protective tape (5) on one side thereof to the thick wafer-level glass carrier (3).

8. The packaging method of the fan-out packaging structure of the thin sensor chip according to claim 1, characterized in that: In the step three, the glass carrier assembly and the protective tape (5) are removed and the glass carrier assembly is penetrated by laser scanning irradiation to dissociate the adhesive (9) between the glass carrier assembly and the thin glass (4).

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