Image sensor integration method

Abstract

The invention provides an image sensor integration method, which comprises the following steps of: providing an image sensor wafer, forming permanent bonding glue on the front surface of the image sensor wafer, fixing a light-transmitting wafer on the permanent bonding glue, and forming a protective layer on the fixed light-transmitting wafer; the back face of the image sensor wafer is thinned through TAIKO grinding, and an upward-protruding TAIKO ring is formed on the edge of the image sensor wafer; forming a back electrode leading-out structure on the back of the image sensor wafer and removing a TAIKO ring; and removing the protective layer, and cutting the image sensor wafer to form a single image sensor. According to the invention, the thickness of the light-transmitting wafer is reduced, and the light transmittance is improved, so that the imaging effect is improved; and meanwhile, the grinding thickness of the image sensor wafer can be thinner. And the final product is smaller in size, lighter and thinner, and higher in overall integration level.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an image sensor integration method. Background Art

[0002] After the wafer of the existing image sensor device is manufactured, it will be packaged on a COB or CSP basis. The overall packaging volume of the image sensor is relatively large. At present, the traditional image sensor integration process generally completes the wafer manufacturing by the wafer factory, and then the packaging and testing factory packages it, and then the final test is performed. The entire production cycle is relatively long. In addition, the volume proportion of the product in the equipment is increasingly miniaturized. The packaging and testing process of the existing technology has been increasingly unable to meet the demand for high integration of image sensors.

[0003] See also Figure 1 , COB (chip on board), after packaging, the finished product is equipped with a shell and lens. COB packaging adopts a single packaging form, which has low production efficiency and requires a thicker glass cover to protect the image sensor to prevent it from being affected by tiny particles and affecting the image quality. Then, a certain thickness of adhesion layer is formed on the frame to bond with the glass;

[0004] The glass is usually 400um thick, and with the packaging shell, the thickness is several millimeters, and the imaging effect will be affected by the thickness of the glass; this method has low production efficiency, and the chip mounting process easily introduces particles to contaminate the microlens on the surface of the sensor, and it cannot meet the current demand for increasingly miniaturized and highly integrated image sensors.

[0005] In order to solve the above problems, a new image sensor integration method needs to be proposed. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an image sensor integration method for solving the problem that the packaging and testing process in the prior art can no longer meet the requirements of high integration of image sensors.

[0007] To achieve the above objectives and other related objectives, the present invention provides an image sensor integration method, comprising:

[0008] Step 1, providing an image sensor wafer, forming a permanent bonding adhesive on the front side of the image sensor wafer, then fixing a light-transmitting wafer on the permanent bonding adhesive, and forming a protective layer on the fixed light-transmitting wafer;

[0009] Step 2: thinning the back side of the image sensor wafer by TAIKO grinding, so that the edge of the image sensor wafer is formed into a convex TAIKO ring;

[0010] Step 3, forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the TAIKO ring;

[0011] Step 4: removing the protective layer and cutting the image sensor wafer into single image sensors.

[0012] Preferably, image sensor devices and microlenses are formed on the front side of the image sensor wafer in step one.

[0013] Preferably, in step 1, the permanent bonding adhesive is applied at a speed of 500 to 5000 rpm.

[0014] Preferably, the thickness of the permanent bonding adhesive in step 1 is 5 to 30 microns.

[0015] Preferably, after forming the permanent bonding adhesive in step 1, the step further includes pre-baking on a hot plate at 70° C. to 150° C. for 5 to 10 minutes.

[0016] Preferably, in step one, an alignment machine is used to align the image sensor wafer and the light-transmitting wafer.

[0017] Preferably, in step one, the aligned image sensor wafer and the transparent wafer are transferred to a bonding machine, and bonding is performed for 10 to 30 minutes under a vacuum of 1 to 10 Pa, a bonding temperature of 50 to 100° C., and a pressure of 50 to 100 kgf.

[0018] Preferably, in step 1, after the image sensor wafer and the light-transmitting wafer are combined, the step further includes baking at a temperature of 100° C. to 200° C. for 30 to 90 minutes in a nitrogen atmosphere.

[0019] Preferably, the thickness of the light-transmitting wafer in step 1 is 50-200 um.

[0020] Preferably, in step 2, the back side of the image sensor wafer is thinned by 5-10 um.

[0021] Preferably, after thinning the image sensor wafer in step 2, the step further includes removing fine lines on the TAIKO polished surface by etching.

[0022] Preferably, in step 2, etching is used to remove 0.5-5 um thickness of the TAIKO polished surface.

[0023] Preferably, the image sensor wafer has a thickness of 50-150 um after thinning in step 2.

[0024] Preferably, a step of bonding quality inspection is also included between steps two and three.

[0025] Preferably, the method of forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the convex portion of the edge of the image sensor wafer in step three comprises: first forming the back electrode lead-out structure; and then removing the TAIKO ring.

[0026] Preferably, the method of forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the convex portion of the edge of the image sensor wafer in step three includes: first removing the TAIKO ring; and then forming the back electrode lead-out structure.

[0027] Preferably, the method for forming the back electrode lead-out structure in step three includes: forming a photoresist layer on the back of the image sensor wafer, opening the photoresist layer by photolithography to form a specific pattern, forming a through hole by etching, the etching termination point is the back metal layer of the pad on the image sensor wafer, forming an insulating film layer on the side wall of the through hole, then filling the through hole with metal, then leading the chip input and output pads to the back of the chip to form a new circuit distribution, and then forming external welding points.

[0028] Preferably, in step three, the photoresist layer is formed by a spray coating process.

[0029] Preferably, the thickness of the photoresist layer in step three is 5-15 um.

[0030] Preferably, the aspect ratio of the through hole in step three is greater than or equal to 2:1.

[0031] Preferably, a first insulating film layer with a thickness of 5 to 10K angstroms is formed between the circuit in step three and the contact surface of the image sensor wafer.

[0032] Preferably, a passivation layer with a thickness of 3 to 10 um is formed between the circuit in step three and the contact surface of the image sensor wafer for insulation.

[0033] Preferably, the surface layer of the circuit in step three is covered with a second insulating film layer.

[0034] As described above, the image sensor integration method of the present invention has the following beneficial effects:

[0035] The present invention uses TAIKO grinding technology to make the image sensor wafer have strong mechanical strength, uses high-transmittance permanent bonding glue, and bonds with 50-200um thick high-transmittance glass, which greatly reduces the thickness of the transparent wafer and improves the transmittance, thereby improving the imaging effect; at the same time, the image sensor wafer grinding thickness can be made thinner, making the final product smaller, thinner, and more integrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Shown is a schematic diagram of a COB (chip on board) packaging structure of the prior art;

[0037] Figure 2 Shown is a schematic diagram of an image sensor integration method of the present invention;

[0038] Figure 3 Shown is a schematic diagram of forming a permanent bonding adhesive according to the present invention;

[0039] Figure 4 It is a schematic diagram showing the formation of a fixed light-transmitting wafer according to the present invention;

[0040] Figure 5 Shown is a schematic diagram of forming a protective layer according to the present invention;

[0041] Figure 6 It is a schematic diagram showing a back electrode lead-out structure formed on the back side of an image sensor wafer according to the present invention;

[0042] Figure 7 Display as Figure 6 A schematic diagram of the structure at point A;

[0043] Figure 8 It is a schematic diagram of forming a single image sensor according to the present invention. DETAILED DESCRIPTION

[0044] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] See also Figure 2 The present invention provides an image sensor integration method, comprising:

[0046] Step 1: Provide an image sensor wafer 101, and form a permanent bonding adhesive 102 on the front side of the image sensor wafer 101 to form a Figure 3 The structure shown in FIG. 1 is then fixed on the permanent bonding adhesive 102 to form a transparent wafer 103. Figure 4 The structure shown in FIG. 1 is formed by forming a protective layer 104 on the fixed transparent wafer 103 to form a Figure 5 The structure shown is used to protect the surface of the high-transmittance glass wafer from scratches;

[0047] In some embodiments, image sensor devices and micro lenses 106 are formed on the front side of image sensor wafer 101 in step 1, and permanent bonding adhesive 102 can protect micro lenses 106 .

[0048] In some embodiments, in step 1, the permanent bonding adhesive 102 is coated at a speed of 500 to 5000 rpm to form a permanent bonding adhesive 102 with a thickness of 5 to 30 μm to ensure bonding uniformity.

[0049] In some embodiments, after forming the permanent bonding adhesive 102 in step 1, a pre-baking step is further included on a hot plate at 70° C. to 150° C. for 5 to 10 minutes. Pre-baking helps the initial curing of the permanent bonding adhesive 102 and can remove solvents or moisture.

[0050] In some embodiments, in step 1, an alignment machine is used to align the image sensor wafer 101 and the transparent wafer 103 . Taking a 300 mm wafer as an example, the single-side error after alignment is ≤0.5 mm.

[0051] In some embodiments, in step 1, the aligned image sensor wafer 101 and the transparent wafer 103 are transferred to a bonding machine and bonded for 10 to 30 minutes at a bonding temperature of 50 to 100° C. and a pressure of 50 to 100 kgf under a vacuum of 1 to 10 Pa.

[0052] In some embodiments, after the image sensor wafer 101 and the transparent wafer 103 are bonded in step 1, baking at 100° C. to 200° C. for 30 to 90 minutes in a nitrogen atmosphere can further strengthen the bonding and ensure that the permanent bonding adhesive 102 is completely cured.

[0053] In some embodiments, the thickness of the transparent wafer 103 (such as glass) in step 1 is 50-200 um, which greatly reduces the thickness of the transparent wafer 103 and increases the transmittance, thereby improving the imaging effect; at the same time, the grinding thickness of the image sensor wafer 101 can be made thinner.

[0054] Step 2: The back side of the image sensor wafer 101 is thinned by TAIKO grinding. The edge of the image sensor wafer 101 is formed into a convex TAIKO ring 1011. The TAIKO ring 1011 can provide better rigidity and anti-warping ability for the two wafers after bonding.

[0055] In some embodiments, in step 2, the back side of image sensor wafer 101 is thinned by 5-10 um.

[0056] In some embodiments, after thinning the image sensor wafer 101 in step 2, a step of removing fine lines on the TAIKO polished surface by etching is further included to further release the stress of the bonded wafer.

[0057] In some embodiments, in step 2, etching is used to remove 0.5-5 um of the TAIKO polished surface.

[0058] In some embodiments, the thickness of the image sensor wafer 101 after thinning in step 2 is 50-150 um.

[0059] In some embodiments, a step of performing a bonding quality inspection is also included between steps two and three, that is, inspecting whether there are any abnormalities in the appearance, such as bubbles, particles, etc.

[0060] Step 3: Form a back electrode lead-out structure on the back side of the image sensor wafer 101 to form Figure 6 The structure shown, and the TAIKO ring 1011 is removed;

[0061] In some embodiments, the method of forming a back electrode lead-out structure on the back side of the image sensor wafer 101 and removing the convex portion of the edge of the image sensor wafer 101 in step three includes: first forming the back electrode lead-out structure; and then removing the TAIKO ring 1011.

[0062] In some embodiments, the method of forming a back electrode lead-out structure on the back side of the image sensor wafer 101 and removing the convex portion of the edge of the image sensor wafer 101 in step three includes: first removing the TAIKO ring 1011; and then forming the back electrode lead-out structure.

[0063] In some embodiments, the method for forming the back electrode lead-out structure in step three includes: forming a photoresist layer on the back of the image sensor wafer 101, photolithography to open the photoresist layer to form a specific pattern, using dry etching or laser to form a through hole 107, the etching stop point is the back metal layer of the pad on the image sensor wafer 101, the side wall of the through hole 107 is formed by CVD / PECVD and other processes. An insulating film layer is then formed on the side wall of the through hole 107, and then the through hole 107 is filled with metal, and then the chip input and output pads 105 are led out to the back of the chip to form a new line 108 distribution, and then an external welding point 110 is formed to form a structure such as Figure 7 The structure shown.

[0064] In some embodiments, the photoresist layer is formed by a spray coating process in step 3. In addition to having a very high photoresist coating efficiency (at least in theory), the spray coating process can solve some applications where uniform photoresist film cannot be obtained on a non-flat sample surface by coating or where high requirements for sample edge coverage are required. For example, using a spray coating process on a non-flat substrate, it is theoretically possible to obtain a uniform resist film thickness at the grooves, sidewalls and edges of the pattern.

[0065] In some embodiments, the thickness of the photoresist layer in step three is 5-15 um.

[0066] In some embodiments, the aspect ratio of the through hole 107 in step three is greater than or equal to 2:1.

[0067] In some embodiments, a first insulating film layer with a thickness of 5-10K angstroms is formed between the contact surface of the circuit 108 and the image sensor wafer 101 in step three.

[0068] In some embodiments, a passivation layer with a thickness of 3-10 um is formed between the circuit 108 in step three and the contact surface of the image sensor wafer 101 for insulation.

[0069] In some embodiments, the surface of the circuit 108 in step three is covered with a second insulating film layer 109 .

[0070] Step 4: remove the protective layer 104, perform laser or mechanical cutting, and cut the image sensor wafer 101 into single image sensors, forming a Figure 8 The structure shown makes the final product smaller, thinner and lighter, and has a higher overall integration.

[0071] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0072] In summary, the present invention uses TAIKO grinding technology to make the image sensor wafer have strong mechanical strength, uses high-transmittance permanent bonding glue, and bonds with 50-200um thick high-transmittance glass, which greatly reduces the thickness of the transparent wafer and improves the transmittance, thereby improving the imaging effect; at the same time, the image sensor wafer grinding thickness can be made thinner. The final product is smaller, thinner, and has a higher overall integration. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An image sensor integration method, characterized in that: At least: Step 1, providing an image sensor wafer, forming a permanent bonding adhesive on the front side of the image sensor wafer, then fixing a light-transmitting wafer on the permanent bonding adhesive, and forming a protective layer on the fixed light-transmitting wafer; Step 2: thinning the back side of the image sensor wafer by TAIKO grinding, so that the edge of the image sensor wafer is formed into a convex TAIKO ring; Step 3, forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the TAIKO ring; Step 4: removing the protective layer and cutting the image sensor wafer into single image sensors.

2. The image sensor integration method according to claim 1, characterized in that: In step 1, an image sensor device and a microlens are formed on the front side of the image sensor wafer.

3. The image sensor integration method according to claim 1, wherein: In step 1, the permanent bonding adhesive is applied at a speed of 500 to 5000 rpm.

4. The image sensor integration method according to claim 1, wherein: The thickness of the permanent bonding adhesive in step 1 is 5 to 30 microns.

5. The image sensor integration method according to claim 1, characterized in that: After forming the permanent bonding adhesive in step 1, the step further includes pre-baking on a hot plate at 70° C. to 150° C. for 5 to 10 minutes.

6. The image sensor integration method according to claim 1, characterized in that: In step one, an alignment machine is used to align the image sensor wafer and the light-transmitting wafer.

7. The image sensor integration method according to claim 6, characterized in that: In step 1, the aligned image sensor wafer and the transparent wafer are transferred to a bonding machine, and bonding is performed for 10 to 30 minutes under a vacuum of 1 to 10 Pa, a bonding temperature of 50 to 100° C., and a pressure of 50 to 100 kgf.

8. The image sensor integration method according to claim 7, characterized in that: In step 1, after the image sensor wafer and the light-transmitting wafer are combined, the process further includes baking the wafers in a nitrogen atmosphere at a temperature of 100° C. to 200° C. for 30 to 90 minutes.

9. The image sensor integration method according to claim 1, characterized in that: The thickness of the light-transmitting wafer in step 1 is 50-200 um.

10. The image sensor integration method according to claim 1, characterized in that: In step 2, the back side of the image sensor wafer is thinned by 5-10 um.

11. The image sensor integration method according to claim 1, characterized in that: After thinning the image sensor wafer, step 2 also includes a step of removing fine lines on the TAIKO polished surface by etching.

12. The image sensor integration method according to claim 9, characterized in that: In step 2, etching is used to remove 0.5 to 5 um of the TAIKO polished surface.

13. The image sensor integration method according to claim 1, characterized in that: The thickness of the image sensor wafer after thinning in step 2 is 50-150 um.

14. The image sensor integration method according to claim 1, characterized in that: A step of bonding quality inspection is also included between steps 2 and 3.

15. The image sensor integration method according to claim 1, characterized in that: The method of forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the convex portion of the edge of the image sensor wafer in step three includes: first forming the back electrode lead-out structure; and then removing the TAIKO ring.

16. The image sensor integration method according to claim 1, characterized in that: The method of forming a back electrode lead-out structure on the back side of the image sensor wafer and removing the convex portion of the edge of the image sensor wafer in step three includes: first removing the TAIKO ring; and then forming the back electrode lead-out structure.

17. The image sensor integration method according to claim 15 or 16, characterized in that: The method for forming the back electrode lead-out structure in step three includes: forming a photoresist layer on the back of the image sensor wafer, opening the photoresist layer by photolithography to form a specific pattern, forming a through hole by etching, the etching termination point is the back metal layer of the pad on the image sensor wafer, forming an insulating film layer on the side wall of the through hole, then filling the through hole with metal, then leading the chip input and output pads to the back of the chip to form a new circuit distribution, and then forming an external welding point.

18. The image sensor integration method according to claim 17, characterized in that: In step three, the photoresist layer is formed by a spray coating process.

19. The image sensor integration method according to claim 18, characterized in that: The thickness of the photoresist layer in step three is 5-15 um.

20. The image sensor integration method according to claim 17, characterized in that: The aspect ratio of the through hole in step three is greater than or equal to 2:

1.

21. The image sensor integration method according to claim 17, wherein: A first insulating film layer with a thickness of 5 to 10K angstroms is formed between the circuit in step three and the contact surface of the image sensor wafer.

22. The image sensor integration method according to claim 17, characterized in that: A passivation layer with a thickness of 3 to 10 um is formed between the contact surface of the circuit and the image sensor wafer in step three for insulation.

23. The image sensor integration method according to claim 17, characterized in that: The surface layer of the circuit in step three is covered with a second insulating film layer.

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