Reworking method of packaging structure with wiring layer

Abstract

The application provides a rework method of a packaging structure with a wiring layer. The method comprises the following steps: 1) providing a substrate to be reworked, wherein the substrate comprises a carrier, a wiring layer on the carrier and a photoresist layer on the wiring layer; the wiring layer comprises a dielectric layer and a metal layer, the metal layer comprises a titanium layer and a copper layer, the titanium layer is located in the dielectric layer, the copper layer is located on the upper surface of the titanium layer, and the upper surface of part of the copper layer is exposed to the upper surface of the dielectric layer; 2) removing the photoresist layer; 3) removing the copper layer; 4) removing part of the titanium layer; and 5) sputtering the titanium layer and the copper layer on the surface of the residual titanium layer by using a sputtering process. The improved process design of the application retains part of the titanium layer when the metal layer is removed, the residual titanium layer can form good protection for the dielectric layer, and part of the titanium layer is removed by using dry etching, so that water vapor can be effectively avoided, interlayer bubbles can be avoided, the adhesion between adjacent structure layers can be improved, the alignment accuracy can be improved, and the production yield can be improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging, and in particular relates to a rework method for a packaging structure with a wiring layer. Background Technology

[0002] Wafer-level packaging (WLP) technology uses an entire wafer for packaging and testing, and then dices the wafer into individual finished chips after packaging. This process differs significantly from traditional chip packaging. Chips packaged using WLP can be more than 20% smaller than those packaged using traditional methods. Furthermore, WLP offers advantages such as faster packaging speed and lower costs, making it the mainstream packaging technology in the market.

[0003] In WLP packaging, photoresist patterning is a crucial process that often requires multiple executions. For example, after sequentially forming a metal layer consisting of a titanium layer and a copper layer on top of the titanium layer (the metal layer is formed within a dielectric layer and extends to its surface to form a wiring layer), a photoresist layer is coated onto the metal layer surface. After exposure and development, the desired pattern is defined, and then structures such as conductive pillars electrically connected to the metal layer are formed according to this pattern. However, due to various reasons, such as uneven photoresist coating, poor photoresist curing, or poor exposure alignment accuracy, the pattern after development may not meet process requirements, necessitating rework. Rework requires removing not only the developed photoresist layer but also the metal layer directly connected to the underside of the photoresist layer (in existing technologies, this typically involves removing both the copper layer and the titanium layer beneath it). In existing technologies, the copper and titanium layers are removed during rework using a wet etching process, where the wafer to be reworked is immersed in an etching solution. However, because the metal layer is formed within and extends to the surface of the dielectric layer, openings are created within the dielectric layer during the etching process. The etching solution seeps into these openings and gradually penetrates into the dielectric layer. In subsequent sputtering and photoresist coating processes, this moisture turns into water vapor when heated, causing defects such as bubbles between adjacent structural layers. These defects can have many adverse effects on subsequent processes, such as reduced alignment accuracy and decreased adhesion between different structural layers, ultimately leading to performance degradation or even complete failure of the final product. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a rework method for a package structure with a wiring layer, which solves the problems of using wet etching to remove the copper layer and the titanium layer below the copper layer in the existing photoresist rework process, causing the etching solution to penetrate into the opening of the dielectric layer, resulting in defects such as bubbles in subsequent processes, which bring many adverse effects to subsequent processes and lead to the deterioration of the performance of the final product or even complete failure.

[0005] To achieve the above and other related objectives, the present invention provides a rework method for a package structure with a wiring layer, the rework method comprising the following steps:

[0006] 1) Provide a substrate to be reworked, the substrate including a carrier, a wiring layer on the carrier and a photoresist layer on the wiring layer; the wiring layer includes a dielectric layer and a metal layer, the metal layer including a titanium layer and a copper layer, the titanium layer being located within the dielectric layer, the copper layer being located on the upper surface of the titanium layer, and a portion of the upper surface of the copper layer being exposed on the upper surface of the dielectric layer;

[0007] 2) Remove the photoresist layer;

[0008] 3) Remove the copper layer exposed on the upper surface of the dielectric layer to expose the titanium layer located on the lower surface of the copper layer; 4) Remove part of the titanium layer by dry etching;

[0009] 5) Use a sputtering process to sputter titanium and copper layers onto the surface of the remaining titanium layer.

[0010] Alternatively, the copper layer can be removed by dry etching.

[0011] Optionally, the wiring layer is multi-layered, with the multi-layered wiring layers stacked one on top of the other, and the metal layers between different wiring layers are electrically connected.

[0012] Optionally, the carrier includes a glass substrate.

[0013] Optionally, in step 4), the thickness of the removed titanium layer is less than half the thickness of the titanium layer.

[0014] Optionally, the rework method further includes the steps of cleaning and drying the obtained structure after removing the copper layer.

[0015] Optionally, the method for removing the photoresist layer in step 2) includes polishing and stripping.

[0016] As described above, in the rework process of this invention, a portion of the titanium layer is retained when the metal layer is removed. Therefore, the residual titanium layer can provide good protection for the dielectric layer. Furthermore, the dry etching method is used to remove part of the titanium layer, which can effectively prevent the etching solution from penetrating into the dielectric layer, avoid the generation of water vapor, avoid the generation of interlayer bubbles, help improve the adhesion between adjacent structural layers, improve alignment accuracy, and help improve production yield. Attached Figure Description

[0017] Figure 1 The flowchart shown is a rework method for a package structure with a wiring layer according to the present invention.

[0018] Figures 2 to 4 Displayed as Figure 1 The structural diagram showing each step of the rework method.

[0019] Component designation explanation

[0020] 11. Carrier

[0021] 12 Dielectric Layer

[0022] 13 Titanium layers

[0023] 14 Copper Layers

[0024] 15 photoresist layers

[0025] Steps S1 to S5 Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] Please see Figures 1-4 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0028] like Figure 1 As shown, the present invention provides a rework method for a package structure with a wiring layer, the rework method comprising the following steps:

[0029] S1: Provide a substrate to be reworked, the substrate including a carrier 11, a wiring layer on the carrier 11, and a photoresist layer 15 on the wiring layer; the wiring layer includes a dielectric layer 12 and a metal layer, the metal layer including a titanium layer 13 and a copper layer 14, the titanium layer 13 being located within the dielectric layer 12, the copper layer 14 being located on the upper surface of the titanium layer 13, and a portion of the upper surface of the copper layer 14 being exposed on the upper surface of the dielectric layer 12, specifically as follows. Figure 2 As shown;

[0030] S2: Remove the photoresist layer 15 to obtain the structure as shown. Figure 3 As shown;

[0031] S3: Remove the copper layer 14 exposed on the upper surface of the dielectric layer 12 to expose the titanium layer 13 located on the lower surface of the copper layer 14, resulting in the structure shown below. Figure 4 As shown;

[0032] S4: Part of the titanium layer 13 is removed by dry etching;

[0033] S5: A titanium layer and a copper layer are sputtered onto the surface of the remaining titanium layer 13 using a sputtering process.

[0034] In existing technologies, when removing metal layers, including titanium and copper layers, during rework operations, both layers are typically removed entirely. This is usually done using a wet etching process, where the structure after photoresist removal is placed in an etching bath, allowing the metal layer to react with the etching solution until it is completely etched away. Since the metal layer is formed within the dielectric layer, its removal leaves gaps within the dielectric layer. Moisture from the etching solution can easily remain in these gaps and gradually penetrate into the dielectric layer. In subsequent processes, such as after the metal and photoresist layers are reformed, the moisture, when heated, forms water vapor that cannot escape, creating bubbles between adjacent structural layers. This can lead to uneven photoresist surfaces, decreased adhesion between adjacent structural layers, and reduced photolithographic alignment accuracy. Furthermore, the moisture can cause oxidation of the metal layer, resulting in performance degradation or even complete failure of the final product. The improved process design of this application retains part of the titanium layer when removing the metal layer. Therefore, the residual titanium layer can provide good protection for the dielectric layer. Furthermore, the use of dry etching to remove part of the titanium layer can effectively prevent moisture from penetrating into the dielectric layer, avoid the generation of water vapor by subsequent heating, and prevent the formation of interlayer bubbles. This helps to improve the adhesion between adjacent structural layers, improve alignment accuracy, and contribute to the improvement of production yield.

[0035] As an example, in step 2), one or a combination of grinding and stripping methods can be used to remove the photoresist layer 15. For example, the photoresist layer 15 can be removed by grinding with a grinding device (if grinding is used, part of the dielectric layer 12 and copper layer 14 can also be removed), or the photoresist can be stripped with a stripping solution.

[0036] As an example, the carrier 11 can be a substrate without device structures, and its material includes, but is not limited to, epoxy resin, silicone, PI, PBO, BCB, silicon oxide, phosphosilicate glass, and fluorinated glass, or a combination of two or more of these. In this case, forming conductive interconnect structures such as wiring layers on the carrier 11 can be used for bonding with a wafer on which a chip is formed to achieve electrical lead-out of the chip. Of course, in other examples, the carrier 11 can also be a substrate with device structures formed, in which case the wiring layers are electrically connected to the devices on the substrate. This embodiment does not strictly limit the form of the carrier. However, regardless of the form of the carrier, the conductive interconnect structures, including the wiring layers, are extremely important and can therefore be improved based on the method of this application.

[0037] Depending on the needs, the wiring layer can be a single layer or multiple layers. In this embodiment, as an example, the wiring layer is multi-layered, such as two or more layers, with multiple wiring layers stacked one on top of the other, and the metal layers between different wiring layers electrically connected to each other. As an example, the material of the dielectric layer 12 includes, but is not limited to, epoxy resin, silicone, PI, PBO, BCB, silicon oxide, phosphosilicate glass, and fluorinated glass, or a combination of two or more of these materials. The method for forming the dielectric layer 12 includes, but is not limited to, chemical vapor deposition or physical vapor deposition. The method for forming the metal layer includes, but is not limited to, physical vapor deposition or electroplating. For example, a pattern corresponding to the metal layer is first formed in the dielectric layer 12 by exposure and development, and then the metal is filled by physical vapor deposition or electroplating to form the metal layer. In this embodiment, the metal layer includes at least a titanium layer 13 and a copper layer 14 located on the upper surface of the titanium layer 13. The titanium layer 13 can enhance the adhesion between the copper layer 14 and the dielectric layer 12, and the thickness of the titanium layer 13 is greater than or equal to 500 nm. The upper surface of the copper layer 14 is exposed to the upper surface of the dielectric layer 12, or may extend to the upper surface of the dielectric layer 12. It should be noted that, due to different screenshot directions, the copper layer shown in the same cross-section may not necessarily be exposed to the surface of the dielectric layer.

[0038] Because the titanium layer 13 protects the dielectric layer 12, the copper layer 14 can be removed using either dry etching or wet etching in this application. However, to minimize moisture generation, dry etching is preferred in this embodiment. It should be noted that when the wiring layer is multi-layered, only the copper layer in the uppermost wiring layer is exposed to the surface of the dielectric layer. In this application, only the copper layer and a portion of the titanium layer in the uppermost wiring layer are removed. To improve cleanliness, the resulting structure can be cleaned and dried after removing the copper layer 14, for example, by introducing dry cleaning gas to purge the structure. After the copper layer 14 is completely removed, openings are formed within the dielectric layer 12, and the titanium layer 13 is exposed within these openings. During the dry removal of copper layer 14, the surface of titanium layer 13 will be oxidized. In fact, to facilitate removal, titanium layer 13 can be partially oxidized first, for example, using thermal oxidation. Therefore, the subsequent dry etching to remove part of the titanium layer 13 is primarily to remove the oxidized surface of titanium layer 13. Through thermal oxidation, a portion of titanium layer 13, for example, less than half its thickness, is oxidized. This oxidized portion is then removed, meaning the thickness of titanium layer 13 removed in step 4) is less than half the total thickness of titanium layer 13. After removing part of titanium layer 13, the resulting structure can be dried and cleaned. Then, metallic titanium is sputtered onto the remaining titanium layer 13 using a sputtering process to achieve a predetermined thickness. A copper layer is then sputtered onto the re-sputtered titanium layer surface. Photoresist is then coated onto the newly formed copper layer surface, and photolithography is used to define the desired pattern. Subsequent processes continue, but will not be elaborated further in this embodiment.

[0039] The inventor conducted multiple experiments with this method in the factory, and the tests showed that the rework yield increased to over 90% after using this rework method. Currently, this method has been fully implemented in the inventor's factory.

[0040] As described above, the present invention provides a rework method for a package structure having a wiring layer. The rework method includes the following steps: 1) providing a substrate to be reworked, the substrate including a carrier, a wiring layer on the carrier, and a photoresist layer on the wiring layer; the wiring layer including a dielectric layer and a metal layer, the metal layer including a titanium layer and a copper layer, the titanium layer being located within the dielectric layer, the copper layer being located on the upper surface of the titanium layer, and a portion of the upper surface of the copper layer being exposed to the upper surface of the dielectric layer; 2) removing the photoresist layer; 3) removing the copper layer whose upper surface is exposed to the upper surface of the dielectric layer to expose the titanium layer located on the lower surface of the copper layer; 4) removing a portion of the titanium layer using dry etching; 5) sputtering a titanium layer and a copper layer onto the surface of the remaining titanium layer using a sputtering process. The improved process design of this application retains a portion of the titanium layer during metal layer removal. This residual titanium layer provides excellent protection for the dielectric layer. Furthermore, the use of dry etching to remove part of the titanium layer effectively avoids moisture generation and interlayer bubbles, improving adhesion between adjacent structural layers, enhancing alignment accuracy, and ultimately increasing production yield. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A rework method for a package structure with a wiring layer, characterized in that, The rework method includes the following steps: 1) Provide a substrate to be reworked, the substrate including a carrier, a wiring layer on the carrier and a photoresist layer on the wiring layer; the wiring layer includes a dielectric layer and a metal layer, the metal layer including a titanium layer and a copper layer, the titanium layer being located within the dielectric layer, the copper layer being located on the upper surface of the titanium layer, and a portion of the upper surface of the copper layer being exposed on the upper surface of the dielectric layer; 2) Remove the photoresist layer; 3) Remove the copper layer on the upper surface exposed to the upper surface of the dielectric layer to expose the titanium layer located on the lower surface of the copper layer; 4) A portion of the titanium layer is removed by dry etching; 5) Use a sputtering process to sputter titanium and copper layers onto the surface of the remaining titanium layer.

2. The rework method according to claim 1, characterized in that: In step 3), the copper layer is removed by dry etching.

3. The rework method according to claim 1, characterized in that: The wiring layer is multi-layered, with the multi-layered wiring layers stacked one on top of the other, and the metal layers between different wiring layers are electrically connected.

4. The rework method according to claim 1, characterized in that: The carrier includes a glass substrate.

5. The rework method according to claim 1, characterized in that: In step 4), the thickness of the removed titanium layer is less than half the thickness of the titanium layer.

6. The rework method according to claim 1, characterized in that: The rework method also includes the steps of cleaning and drying the obtained structure after removing the copper layer.

7. The rework method according to claim 1, characterized in that: The method for removing the photoresist layer in step 2) includes one or both of the following: polishing and stripping.

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