Chip bonding method

Abstract

The invention provides a chip bonding method which comprises the following steps: S1, acquiring a base material, and depositing a material on the base material to obtain a plurality of devices; s2, the side, provided with the device, of the base material is subjected to spin coating of photoresist, photoetching, etching and then cutting, a plurality of chips are obtained, the base material of each chip is provided with a pickup part (the pickup part is a chip cutting channel), and the pickup part is sunken in a chip bonding interface; s3, adsorbing the pickup part of each chip through a flip chip suction head, overturning, enabling the bonding interface of the chip to face the wafer, and bonding the chip with the wafer; and S4, after each chip is bonded with the wafer, removing the base material on the chip. According to the invention, the flip chip suction head is adopted to suck the chip by sucking the pick-up part, and is not in direct contact with the chip, so that the problem of scratching a bonding interface of the chip is avoided, and the bonding yield is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chips, and in particular relates to a chip bonding method. Background Art

[0002] Chip bonding is a form of interconnection between a chip and a carrier. The current bonding method is to spin-coat a protective glue on the wafer bonding interface and then cut it to form a chip. The bonding interface of the chip faces upward, and the protective glue is removed and cleaned in sequence. After cleaning, the chip bonding interface is sucked up by the chip bonding machine's suction head and flipped over to bond the chip's bonding surface to the wafer. Since the suction head will directly contact the bonding interface, it will scratch the bonding interface or introduce impurities, resulting in a reduced bonding yield. Summary of the invention

[0003] In view of this, the present invention provides a chip bonding method, which absorbs the chip by sucking the pickup portion (chip cutting path area) without direct contact with the chip, thereby avoiding the problem of scratching the bonding interface of the chip and improving the bonding yield.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a chip bonding method, comprising the following steps:

[0006] S1, obtaining a substrate, and depositing materials on the substrate to obtain a plurality of devices;

[0007] S2, spin-coating photoresist on one side of the substrate where the device is provided, photolithography to expose the cutting road area, and after etching and cutting, obtain a plurality of chips, wherein a pickup portion is provided on the substrate of each chip, and the pickup portion is recessed in the chip bonding interface;

[0008] S3, bonding the chip to the wafer by adsorbing the pick-up portion of each chip and flipping it so that the bonding interface of the chip faces the wafer;

[0009] S4. After each chip is bonded to the wafer, the substrate on the chip is removed.

[0010] Preferably, the pickup portion is arranged around the chip cutting path area. It should be noted that according to the previous device design, the cutting path width can be appropriately adjusted. By adding a photolithography etching process, the cutting path is smoothed, which is conducive to the flip chip suction head to pick up the chip.

[0011] Preferably, in step S3, each chip is adsorbed by a flip chip suction head of a chip bonding machine, and when the suction head adsorbs the chip, the suction head cover is arranged on the outside of the device and adsorbed on the picking part.

[0012] Preferably, the end of the suction head away from the chip is connected to a suction duct, and the end of the suction head close to the chip is provided with at least one first suction hole.

[0013] Preferably, a second suction hole is formed through the side wall of the suction head, and the suction head is connected to the suction duct through the second suction hole.

[0014] Preferably, when the suction head is adsorbed on the picking-up portion, ends of the suction head close to the picking-up portion are both located on the picking-up portion.

[0015] Preferably, in step S2, after etching is completed, a UV film is attached to the side of the substrate where the device is provided, and the substrate is cut. After cutting, the substrate is transferred to the mother-child ring by inverting the mold, and the film is expanded and split to obtain multiple chips.

[0016] Preferably, in step S2, the chip is cleaned to keep its bonding interface clean.

[0017] Preferably, in step S3, before transferring the chip to the wafer, active plasma is used to process the side of the wafer and the chip where the bonding interface is provided, so as to make the chip and the wafer active.

[0018] Preferably, in step S3, after the chip is bonded to the wafer, the bonded chip and the wafer are annealed at 200-300° C. for 2 h to increase the bonding strength.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention provides a pickup portion on the chip, and the chip is sucked by the pickup portion without direct contact with the chip, thereby avoiding scratches on the bonding interface of the chip and improving the bonding yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of a chip provided by an embodiment of the present invention;

[0022] Figure 2 for Figure 1 A side view of a chip;

[0023] Figure 3 A schematic diagram of the structure of a suction head provided by an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the structure of a suction head provided by another embodiment of the present invention;

[0025] Figure 5An assembly diagram of a chip and a pipette tip provided in one embodiment of the present invention;

[0026] Figure 6 A chip bonding flow chart provided in accordance with an embodiment of the present invention.

[0027] Reference numerals: chip 1 , substrate 11 , pickup portion 111 , device 12 , suction head 2 , first suction hole 21 , second suction hole 22 . DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0029] Combination Figure 1-6 The present invention provides a chip 1 bonding method, comprising the following steps:

[0030] S1, obtaining a substrate 11, and depositing materials on the substrate 11 to obtain a plurality of devices 12;

[0031] S2, spin-coating photoresist on the side of the substrate 11 provided with the device 12, photolithography, etching and cutting to obtain a plurality of chips 1, wherein a pickup portion 111 is provided on the substrate 11 of each chip 1, and the pickup portion 111 is recessed in the bonding interface of the chip 1;

[0032] S3, bonding the chip 1 to the wafer by adsorbing the pick-up portion 111 of each chip 1 and flipping it so that the bonding interface of the chip 1 faces the wafer;

[0033] S4. After each chip 1 is bonded to the wafer, the substrate 11 on the chip 1 is removed.

[0034] In the above technical solution, the material of the substrate 11 is not limited, and silicon material is commonly used. In step S2, a photoresist is applied to the surface of the substrate 11 using a coating machine. In some embodiments, in order not to increase the volume of the chip 1, the width of the pickup portion 111 is the width of the cutting path in the original chip 1 design (that is, the pickup portion 111 occupies the width position of the original cutting path). According to the actual size and weight of the chip 1, the width of the cutting path needs to be appropriately increased. In the technical solution of the present invention, the specific structure of the pickup portion 111 is not limited. For example, it can be an annular or rectangular shape surrounding the outside of the substrate 11. For ease of production, in some embodiments, the pickup portion 111 is an annular shape surrounding the outside of the substrate 11. All chips 1 are bonded to one of the wafers through step S3. In step S4, after completing chip bonding, the following processing can be performed according to the chip type: for Si-based chips, the excess Si substrate can be removed through the steps of thinning, polishing, and wet cleaning. Due to their unique structures, some III and IV epitaxial wafers have different selectivity in the wet process. For example, N-InP in the epi InP structure can be dissolved by HCL / H2SO4, thereby removing the InP substrate and leaving only the InP epi layer on the target wafer. For some compound chips, it is impossible to directly remove the substrate by thinning, or when it is difficult to remove the substrate by wet method for homoepitaxial (SiC), the processed device can be ion implanted and then subjected to bonding, annealing activation, and substrate stripping processes to achieve the purpose of substrate removal.

[0035] The present invention provides a pickup portion 111 on the chip 1, and absorbs the chip 1 by absorbing the pickup portion 111 without direct contact with the chip 1, thereby avoiding scratching the bonding interface of the chip 1 and improving the bonding yield.

[0036] Further, in step S3, each chip 1 is adsorbed by the suction head 2 of the chip bonding machine. When the suction head 2 adsorbs the chip 1, the suction head 2 is covered on the outside of the device 12 and adsorbed on the pickup portion 111. The assembly diagram of the suction head 2 and the chip 1 is shown in FIG. Figure 5 As shown, since the suction head 2 does not contact the bonding interface, damage to the bonding interface is reduced.

[0037] like Figure 3 As shown, in some embodiments, the end of the suction head 2 away from the chip 1 is connected to a suction duct (not shown in the figure), and the end of the suction head 2 close to the chip 1 is provided with at least one first suction hole 21. The number of the at least one first suction hole 21 can be two, four, etc. In order to make the force uniform, it is better to arrange multiple first suction holes 21 evenly spaced.

[0038] like Figure 4 As shown, in some embodiments, a second suction hole 22 is penetrated through the side wall of the suction head 2, and the suction head 2 is connected to the suction duct through the second suction hole 22. When the picking part 111 is adsorbed, the second suction hole 22 is located at the upper part of the device 12, and the adsorption pressure is large.

[0039] Furthermore, when the suction head 2 is adsorbed on the picking portion 111, the ends of the suction head 2 close to the picking portion 111 are all located on the picking portion 111. Figure 1 As shown, for example, when the width of the pickup portion 111 is L1, the side wall width of the end of the suction head 2 close to the chip 1 is L2, L2≤L1, that is, the end of the suction head 2 does not protrude from the pickup portion 111, so that the pickup effect is better.

[0040] Furthermore, in step S2, after etching is completed, a UV film is applied to the side of the substrate 11 where the device 12 is provided, and the substrate 11 is cut. After cutting, the substrate 11 is transferred to the mother-child ring by reverse molding, and the film is expanded and split to obtain multiple chips 1. When cutting, the back side hidden cutting process is used to reduce dust and other impurities generated during the chip 1 cutting process.

[0041] Furthermore, in step S2, the chip 1 is cleaned to keep its bonding interface clean. Dry and wet methods are used during cleaning to ensure the cleanliness of the bonding interface.

[0042] Furthermore, in step S3, before transferring the chip 1 to the wafer, the wafer and the side of the chip 1 provided with the bonding interface are processed using active plasma to make the chip 1 and the wafer active.

[0043] Furthermore, in step S3, after the chip 1 is bonded to the wafer, the bonded chip 1 and the wafer are annealed at 200-300°C for 2h to increase the bonding strength so as to meet the subsequent processing requirements of the device 12.

[0044] Example 1

[0045] The present invention provides a chip bonding method comprising the following steps:

[0046] Step 1: Chemically mechanically polish and clean the silicon substrate to ensure that the cleanliness and roughness of the bonding interface are within the target range;

[0047] Step 2: Use a coating machine to coat the photoresist on the surface of the silicon substrate;

[0048] Step 3: According to the previous layout design, the silicon substrate is subjected to photolithography and etching processes to carve out a recess (pickup portion) on the edge of the chip to provide a pick-up position for the suction head. After the etching process is completed, the excess photoresist is removed;

[0049] Step 4: After applying UV film on the front side of the silicon substrate, the wafer is cut using the back side hidden cutting process (the back side hidden cutting process can reduce impurities and tiny particles generated during chip cutting);

[0050] Step 5: Transfer the silicon substrate to the mother-child ring and perform film expansion and splitting;

[0051] Step 6: After the chip is split, dry and wet clean it to ensure the cleanliness of the bonding interface;

[0052] Step 7: Plasma treatment is performed on the chip and target wafer to make its surface active;

[0053] Step 8: Use a customized pipette tip. Figure 3 As shown, there are four first suction holes for picking up chips;

[0054] Step 9: Use a high-precision chip bonder to achieve direct chip-to-wafer bonding;

[0055] Step 10: The pre-bonded product is annealed at 200°C for 2 hours to increase the bonding strength for subsequent device processing requirements.

[0056] Step 11: The Si-based chip can be removed from the Si substrate through thinning, polishing, and wet cleaning.

[0057] Example 2

[0058] The present invention provides a chip bonding method comprising the following steps:

[0059] Step 1: Chemically mechanically polish and clean the silicon substrate to ensure that the cleanliness and roughness of the bonding interface are within the target range;

[0060] Step 2: Use a coating machine to coat the photoresist on the surface of the silicon substrate;

[0061] Step 3: According to the previous layout design, the silicon substrate is subjected to photolithography and etching processes to carve out a recess (pickup portion) on the edge of the chip to provide a pick-up position for the suction head. After the etching process is completed, the excess photoresist is removed;

[0062] Step 4: After applying UV film on the front side of the silicon substrate, the wafer is cut using the back side hidden cutting process (the back side hidden cutting process can reduce the particles generated during the chip cutting process);

[0063] Step 5: Transfer the silicon substrate to the mother-child ring and perform film expansion and splitting;

[0064] Step 6: Dry and wet clean the chip after splitting to ensure the cleanliness of the bonding interface

[0065] Step 7: Plasma treatment is performed on the chip and target wafer to make its surface active;

[0066] Step 8: Use a customized pipette tip. Figure 4 As shown, there is a second suction hole for picking up the chip;

[0067] Step 9: Use a high-precision alignment die bonder to achieve direct chip-to-wafer bonding;

[0068] Step 10: The pre-bonded product is annealed at 200°C for 2 hours to increase the bonding strength for subsequent device processing requirements.

[0069] Step 11: The Si-based chip can be removed from the Si substrate through thinning, polishing, and wet cleaning.

[0070] Comparative Example 1

[0071] The present invention provides a chip bonding method comprising the following steps:

[0072] Step 1: Chemically mechanically polish and clean the silicon substrate to ensure that the cleanliness and roughness of the bonding interface are within the target range;

[0073] Step 2: Use a coating machine to coat the photoresist on the surface of the silicon substrate;

[0074] Step 3: After applying UV film on the front side of the silicon substrate, the wafer is cut using the back side hidden cutting process (the back side hidden cutting process can reduce the particles generated during the chip cutting process);

[0075] Step 4: Transfer the silicon substrate to the mother-child ring and perform film expansion and splitting;

[0076] Step 5: Dry and wet clean the chip after splitting to ensure the cleanliness of the bonding interface

[0077] Step 6: Plasma treatment is performed on the chip and target wafer to make its surface active;

[0078] Step 7: Use a regular suction head to pick up the chip;

[0079] Step 8: Use a high-precision alignment die bonder to achieve direct chip-to-wafer bonding;

[0080] Step 9: The pre-bonded product is annealed at 200°C for 2 hours to increase the bonding strength for subsequent device processing requirements.

[0081] Step 10: The Si-based chip can be removed from the Si substrate through thinning, polishing, and wet cleaning.

[0082] Performance testing and results

[0083] The steps of Example 1 and Comparative Example 1 were used to bond the chip and the wafer. After 100 repetitions, 100 bonded devices of Example 1 and Comparative Example 1 were obtained respectively. The bonding yields of Example 1 and Comparative Example 1 were tested. The results are shown in Table 1.

[0084] Group Bonding yield Example 1 99.3％ Comparative Example 1 97％

[0085] It can be seen from Table 1 that by adding a pick-up portion, the suction head avoids direct contact with the chip when picking up the chip, which can improve the bonding yield.

[0086] The specific raw materials not described in the present invention are all existing materials and can be directly purchased from the market.

[0087] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A chip bonding method, characterized in that: The following steps are involved: S1, obtaining a substrate, and depositing materials on the substrate to obtain a plurality of devices; S2, spin-coating photoresist on the side of the substrate provided with the device, photolithography, etching and cutting to obtain a plurality of chips, wherein a pickup portion is provided on the substrate of each chip, and the pickup portion is recessed in the chip bonding interface; S3, bonding the chip to the wafer by adsorbing the pick-up portion of each chip and flipping it so that the bonding interface of the chip faces the wafer; S4. After each chip is bonded to the wafer, the substrate on the chip is removed.

2. The method according to claim 1, characterized in that The pickup portion is arranged around the chip cutting path area.

3. The method according to claim 2, characterized in that In step S3, each chip is adsorbed by a flip chip suction head of a chip bonding machine. When the suction head adsorbs the chip, the suction head cover is arranged on the outside of the device and adsorbed on the picking part.

4. The method according to claim 3, characterized in that: The end of the suction head away from the chip is connected with a suction duct, and the end of the suction head close to the chip is provided with at least one first suction hole.

5. The method according to claim 3, characterized in that: A second suction hole is formed through the side wall of the suction head, and the suction head is connected with the suction duct through the second suction hole.

6. The method according to claim 3, characterized in that When the suction head is adsorbed on the picking-up portion, the ends of the suction head close to the picking-up portion are all located on the picking-up portion.

7. The method according to claim 1, characterized in that In step S2, after etching is completed, a UV film is attached to the side of the substrate where the device is provided, and the substrate is cut. After cutting, the substrate is transferred to the mother-child ring by inverting the mold, and the film is expanded and split to obtain multiple chips.

8. The method according to claim 1, characterized in that In step S2, the chip is cleaned to keep its bonding interface clean.

9. The method according to claim 1, characterized in that: In step S3, before transferring the chip to the wafer, active plasma is used to process the side of the wafer and the chip where the bonding interface is provided, so as to make the chip and the wafer active.

10. The method according to claim 1, characterized in that In step S3, after the chip is bonded to the wafer, the bonded chip and the wafer are annealed at 200-300° C. for 2 h to increase the bonding strength.

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