Preparation method of integrated chip bonding pad and bonding pad thereof
Aluminum pads were prepared by solution immersion and water bath heating, forming a strong, uniform, and dense gold layer. This solved the problem of insufficient reliability of aluminum pads in high-performance integrated circuits and improved the stability and preparation efficiency of the pads.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-13
AI Technical Summary
In the prior art, aluminum pads have insufficient reliability and stability in high-performance, fine-pitch and high-I/O density integrated circuits, especially in humid or high-temperature and high-humidity environments where they are prone to oxidation and corrosion, affecting the reliability of electrical connections.
A combination of solution immersion and water bath heating process is used to form a dense zinc layer through a first zinc immersion, zinc stripping with nitric acid, and a second zinc immersion. Then, nickel and gold immersion are performed to form a gold layer with strong adhesion and uniform density, which inhibits the interdiffusion between aluminum and gold.
It improves the preparation efficiency and stability of the solder pads, enhances the bonding force between the zinc and nickel layers, provides catalytic activity, ensures the stability and corrosion resistance of the gold layer, and improves the reliability of the electrical connection.
Smart Images
Figure CN121666129A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of chip fabrication, and more specifically, to a method for fabricating integrated chip pads and the pads thereof. Background Technology
[0002] In CMOS integrated circuit manufacturing processes, aluminum and its alloys have long been the preferred materials for top-layer metal interconnects and chip pads due to their excellent conductivity, high compatibility with silicon processes, and ease of photolithography and etching. These aluminum pads are key interfaces for the electrical connection between the chip and the external world, such as wire bonding and flip chip bumps. However, as integrated circuits continue to evolve towards higher performance, smaller size, more complex packaging, and more demanding application environments, traditional aluminum pads have gradually revealed limitations in terms of reliability and advanced packaging compatibility: the aluminum surface is prone to oxidation, forming a dense insulating layer, increasing the difficulty and resistance of wire bonding, and may lead to bonding point failure under long-term use or high temperature and humidity environments; or, aluminum is prone to electrochemical corrosion in humid or halogen-containing environments, affecting reliability; in addition, aluminum has poor wettability with commonly used lead-free solders, and the reaction easily forms brittle intermetallic compounds, resulting in insufficient flip chip connection strength and affecting reliability; furthermore, in advanced packaging requiring finer pitch, higher I / O density, or direct deposition of under-bump metallization (UBM), the performance and stability of aluminum pads become bottlenecks.
[0003] Based on this, there are currently methods to prepare aluminum-based composite materials by forming a metal protective layer on the surface of an aluminum-based substrate and then using electroplating to form a metal coating, in order to improve the reliability of aluminum-based composite materials. While electroplating can produce a smooth metal coating, it requires additional voltage and the preparation process is relatively cumbersome. Furthermore, although there are currently methods to obtain a metal layer by solution immersion, the surface roughness of the prepared metal layer is poor and its stability is insufficient. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the solution immersion method for preparing pads in the prior art, which results in unsatisfactory stability. This invention provides a method for preparing integrated chip pads and the pads thereof, which can form a pad structure with strong bonding force, uniformity and density, improve preparation efficiency and improve pad stability.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preparing integrated chip pads is provided, comprising the following steps: S1. Remove the aluminum pad layer and clean it to remove contaminants; S2. The aluminum pad layer is subjected to a solution immersion method to perform a first zinc immersion, nitric acid zinc stripping, and a second zinc immersion in sequence to obtain a zinc layer; S3. The zinc layer is subjected to a solution immersion method and nickel deposition using a water bath heating method to obtain a nickel layer; S4. The nickel layer is subjected to a solution immersion method and then gold deposition using a water bath heating method to obtain a gold layer.
[0006] This invention discloses a method for preparing integrated chip pads. The method utilizes a solution immersion method to improve the efficiency of pad preparation. Through a process involving primary zinc plating, nitric acid stripping, and secondary zinc plating, a dense and uniform zinc layer is obtained, enhancing the adhesion between the zinc layer and the subsequently prepared nickel layer. The nickel layer obtained through water bath heating provides catalytic activity to drive the subsequent preparation of the gold layer. Furthermore, by using a solution immersion method and water bath heating for gold plating, a strong, uniform, and dense gold layer is formed, effectively suppressing the interdiffusion problem between aluminum and gold and improving the stability of the pad.
[0007] Further, step S1 includes the following steps: S11. Adhere the aluminum pad layer to the glass slide; S12. Ultrasonic cleaning of the glass slide with aluminum pads attached; S13. Immerse the glass slide in a sodium hydroxide solution to dissolve the aluminum oxide on the surface of the aluminum pad layer; S14. Immerse the glass slide in nitric acid solution to dissolve the residual metal oxides on the surface of the aluminum pad layer; The aluminum pad layer is rinsed with deionized water before and after step S14.
[0008] Further, step S2 includes the following steps: S21. Immerse the glass slide in the aluminum zinc immersion solution and let it stand, and perform a zinc immersion on the aluminum pad layer; S22. After the first zinc precipitation, the slide is immersed in nitric acid solution and allowed to stand to remove the loose particles from the first zinc precipitation; S23. After zinc removal with nitric acid, the glass slide is immersed in aluminum zinc immersion solution and left to stand. A second zinc immersion is performed on the aluminum pad layer to obtain the zinc layer.
[0009] Furthermore, in step S2, the soaking time for the first zinc immersion is longer than that for the second zinc immersion; after completing the first zinc immersion, nitric acid zinc stripping, and second zinc immersion, deionized water is used for rinsing.
[0010] Further, step S3 includes the following steps: S31. Add the chemical nickel plating solution to a beaker, and then immerse the glass slide in the chemical nickel plating solution; S32. The beaker is heated in a water bath using a container to obtain the nickel layer.
[0011] Further, step S4 includes the following steps: S41. Add the chemical gold immersion solution to a beaker, and then immerse the glass slide in the chemical gold immersion solution; S42. The beaker is heated in a water bath using a container to obtain the gold layer.
[0012] Further, in step S32 or S42, a separator is placed in the container, the beaker is placed on the separator, and then water bath heating is performed.
[0013] Furthermore, the method for preparing the integrated chip pads also includes step S5: immersing a glass slide in a descaling agent solution and sealing it to allow it to stand, thereby separating the glass slide from the aluminum pad layer.
[0014] Furthermore, after completing steps S1, S2, S3, and S4, deionized water is used for rinsing.
[0015] The present invention also provides a pad prepared by the above-described method for preparing integrated chip pads, comprising an aluminum pad layer, a zinc layer, a nickel layer, and a gold layer stacked from bottom to top.
[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a method for preparing integrated chip pads and the pads thereof. The method utilizes a solution immersion method to prepare the metal layer, which improves the preparation efficiency of the pads. Through a first zinc plating, nitric acid stripping, and a second zinc plating process, a dense and uniform zinc layer is obtained, enhancing the adhesion between the zinc layer and the subsequently prepared nickel layer. The nickel layer obtained by water bath heating provides catalytic activity to drive the subsequent preparation of the gold layer. Then, by using a solution immersion method and water bath heating for gold plating, a strong, uniform, and dense gold layer is formed, effectively suppressing the interdiffusion problem between aluminum and gold and improving the stability of the pads. Attached Figure Description
[0017] Figure 1 This is a flowchart of a method for preparing an integrated chip pad according to the present invention; Figure 2 This is a state diagram after step S1 is completed in the method for preparing integrated chip pads according to the present invention. Figure 3 This is a state diagram after step S21 is completed in the method for preparing integrated chip pads according to the present invention. Figure 4 This is a state diagram after step S22 is completed in the method for preparing integrated chip pads according to the present invention. Figure 5 This is a state diagram after step S23 is completed in the method for preparing integrated chip pads according to the present invention. Figure 6This is a state diagram after step S3 is completed in the method for preparing integrated chip pads according to the present invention. Figure 7 This is a state diagram after step S4 is completed in the method for preparing integrated chip pads according to the present invention. Figure 8 This is a schematic diagram of the EDS of the aluminum pad layer of the present invention; Figure 9 This is an EDS schematic diagram of the gold layer of the present invention; Figure 10 This is a schematic diagram of the mean square error of the surface roughness of the gold layer AMF in this invention. Figure 11 This is a structural diagram of a solder pad according to the present invention.
[0018] In the attached diagram: 100, aluminum pad layer; 200, zinc layer; 300, nickel layer; 400, gold layer. Detailed Implementation
[0019] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0020] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0021] Example 1 like Figure 1 The first embodiment of a method for preparing an integrated chip pad according to the present invention is shown, which includes the following steps: S1. Take 100mm of the aluminum pad layer and clean it to remove dirt; S2. The aluminum pad layer 100 is subjected to a solution immersion method to perform a first zinc immersion, nitric acid zinc stripping, and a second zinc immersion in sequence to obtain the zinc layer 200. S3. Apply a solution immersion method to zinc layer 200 and perform nickel deposition using water bath heating to obtain nickel layer 300; S4. Gold layer 400 is obtained by immersion in solution and heating in a water bath on nickel layer 300.
[0022] Selecting the solution immersion method for metal layer preparation can improve the efficiency of pad preparation. Specifically, through a first zinc immersion, nitric acid zinc stripping, and a second zinc immersion process, a dense and uniform zinc layer can be obtained, which can enhance the adhesion between the zinc layer and the subsequently prepared nickel layer. The nickel layer prepared by water bath heating can provide catalytic activity to drive the preparation of the subsequent gold layer. Then, by using the solution immersion method and water bath heating for gold immersion, a gold layer with strong adhesion and uniform density can be formed, which can effectively suppress the interdiffusion problem between aluminum and gold and improve the stability of the pad.
[0023] Example 2 This embodiment is a second embodiment of a method for preparing integrated chip pads. This embodiment is similar to Embodiment 1, except that, as... Figures 2 to 10 As shown, step S1 includes the following steps: S11. Adhere the aluminum pad layer 100 to the glass slide; Specifically, the aluminum pad layer 100 is adhered to the glass slide by adhesive, and it is ensured that there is no adhesive on the upper surface of the aluminum pad layer 100. In this embodiment, AB glue can be selected as the adhesive. S12. The glass slide with the aluminum pad layer 100 is ultrasonically cleaned; Specifically, acetone, anhydrous ethanol, and deionized water were used to ultrasonically clean the glass slide in sequence, which could remove organic contaminants such as grease and dust from the aluminum pad layer 100 and ensure the hydrophilicity of the aluminum pad layer 100 surface. In this embodiment, the duration of each ultrasonic cleaning was 3 minutes. S13. Immerse the glass slide in sodium hydroxide solution to dissolve the aluminum oxide on the surface of the aluminum pad layer 100. Then, rinse the aluminum pad layer 100 with room temperature deionized water to remove the residual sodium hydroxide solution on the surface. Specifically, immersing a glass slide in a 10% NaOH solution at room temperature dissolves the aluminum oxide on the surface of the aluminum pad layer 100, thereby exposing the active metal surface of the aluminum pad layer 100. In this embodiment, the immersion time of the glass slide in the 10% NaOH solution is 10 seconds, the rinsing time with deionized water is 1 minute, and the rinsing efficiency can be improved by shaking the glass slide when rinsing with deionized water. S14. Immerse the glass slide in nitric acid solution to dissolve the metal oxide residue on the surface of the aluminum pad layer 100. Then, rinse the aluminum pad layer 100 with room temperature deionized water to remove the residual nitric acid solution on the surface. Specifically, immersing the glass slide in a 20% HNO3 solution at room temperature dissolves any residual metal oxides that may be generated from zinc replacement, thereby improving the cleanliness of the aluminum pad layer 100 surface. In this embodiment, the immersion time of the glass slide in the 20% HNO3 solution is 45 seconds, and the rinsing time with deionized water is 1 minute. The glass slide can be agitated during rinsing. After step S14, the following can be obtained: Figure 2 The aluminum pad layer 100 is shown after cleaning.
[0024] Step S2 includes the following steps: S21. Immerse the glass slide in the aluminum zinc immersion solution and let it stand. Perform a zinc immersion on the aluminum pad layer 100 to provide catalytic active sites for the subsequent nickel immersion operation. Then rinse with room temperature deionized water to remove the residual aluminum zinc immersion solution on the surface. Specifically, the aluminum-zinc precipitate solution is shaken thoroughly before use. The slide is immersed in the solution at room temperature and left to stand without shaking to avoid uneven zinc precipitation. In this embodiment, the slide is immersed in the aluminum-zinc precipitate solution for 45 seconds, and rinsed with deionized water for 1 minute. The slide can be shaken during rinsing. After one zinc precipitation, the slide is... Figure 3 As shown; S22. After the first zinc immersion, the slide is immersed in nitric acid solution and left to stand to remove the loose particles in the first zinc immersion. Then, it is rinsed with room temperature deionized water to remove the residual nitric acid solution on the surface. Specifically, immersing a glass slide in a 20% HNO3 solution at room temperature can remove some of the loose particles from the initial zinc precipitation, resulting in a more uniform surface. In this embodiment, the slide is immersed in the 20% HNO3 solution for 15 seconds, and rinsed with deionized water for 1 minute. The slide can be agitated during rinsing. After zinc removal with nitric acid... Figure 4 As shown; S23. After zinc stripping with nitric acid, the glass slide is immersed in aluminum zinc bath and left to stand. A second zinc bath is performed on the aluminum pad layer 100 to obtain a denser and more uniform zinc layer, which enhances the subsequent bonding force with the nickel layer. Then, the slide is rinsed with room temperature deionized water to remove the residual aluminum zinc bath on the surface, and zinc layer 200 is obtained. Specifically, the glass slide is immersed in the aluminum-zinc immersion solution at room temperature and allowed to stand. In this embodiment, the immersion time for the second zinc immersion is shorter than that for the first zinc immersion. The immersion time of the glass slide in the aluminum-zinc immersion solution is 30 seconds, and the rinsing time with deionized water is 1 minute. The glass slide can be shaken during rinsing. After the second zinc immersion, as shown... Figure 5 As shown.
[0025] Step S3 includes the following steps: S31. Add the chemical nickel plating solution to a beaker, and then immerse the glass slide in the chemical nickel plating solution; Specifically, the chemical nickel precipitate solution is shaken well before being transferred to a beaker; S32. Heat the beaker in a water bath using a container to obtain a nickel layer 300; Specifically, a separator is placed in the container, and the beaker is placed on the separator to prevent the beaker and the glass slide inside from shaking during heating. Then, the container is heated in a water bath to bring the chemical nickel plating solution to 90-100°C for 4 minutes. In this embodiment, the separator can be a mesh structure, and the resulting nickel layer is 300 mm thick. Figure 6 As shown.
[0026] Step S4 includes the following steps: S41. Add the chemical gold immersion solution to a beaker, and then immerse the glass slide in the chemical gold immersion solution; S42. Heat the beaker in a water bath using a container to obtain a gold layer 400; Specifically, a separator was placed in the container, and the beaker was placed on the separator to prevent shaking. Then, the container was heated in a water bath to bring the chemical gold deposition solution to 90-100°C for 6 minutes; the resulting gold layer was 400 μm thick. Figure 7 As shown, the gold layer 400 is extremely stable in air and does not easily oxidize, providing a clean and active surface for wire bonding, greatly improving bonding yield and long-term reliability. Furthermore, the gold layer 400 hardly reacts with common media in the environment and has excellent corrosion resistance. Figure 8 and Figure 9 You can view the difference between aluminum pad layer 100 before and after preparation; such as Figure 10 As shown, Rq represents the root mean square surface roughness error, which indicates that the prepared gold layer 400 has a smooth surface and good stability.
[0027] In this embodiment, after completing steps S1, S2, S3, and S4, the water is rinsed with room temperature deionized water before proceeding to the next step, and each rinsing time is 1 minute.
[0028] In this embodiment, the preparation method further includes step S5: immersing the glass slide in the adhesive solution and sealing it to stand, so that the glass slide is separated from the aluminum pad layer 100; specifically, the adhesive solution is poured into a beaker, then the glass slide is placed in the solution, and the mouth of the beaker is sealed with plastic wrap and left to stand for more than 12 hours, so that the glass slide is separated from the aluminum pad layer 100.
[0029] Example 3 like Figure 11The diagram shows a first embodiment of a solder pad according to the present invention, which is prepared by the integrated chip solder pad preparation method described in Embodiment 1 or 2. The solder pad includes an aluminum solder pad layer 100, a zinc layer 200, a nickel layer 300, and a gold layer 400 stacked from bottom to top. In this embodiment, the prepared solder pad has a rectangular structure with a length of 2μm to 1000μm and a width of 2μm to 1000μm.
[0030] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.
[0031] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing integrated chip pads, characterized in that, Includes the following steps: S1. Take the aluminum pad layer (100) and clean it to remove dirt; S2. The aluminum pad layer (100) is subjected to a solution immersion method to perform a first zinc immersion, nitric acid zinc stripping, and a second zinc immersion in sequence to obtain a zinc layer (200). S3. The zinc layer (200) is subjected to a solution immersion method and nickel deposition using a water bath heating method to obtain a nickel layer (300). S4. The nickel layer (300) is subjected to a solution immersion method and a water bath heating method to deposit gold, thereby obtaining a gold layer (400).
2. The method for preparing integrated chip pads according to claim 1, characterized in that, Step S1 includes the following steps: S11. Adhere the aluminum pad layer (100) to the glass slide; S12. The glass slide with the aluminum pad layer (100) is ultrasonically cleaned; S13. Immerse the glass slide in a sodium hydroxide solution to dissolve the aluminum oxide on the surface of the aluminum pad layer (100); S14. Immerse the glass slide in nitric acid solution to dissolve the residual metal oxides on the surface of the aluminum pad layer (100); Before and after performing step S14, the aluminum pad layer (100) is rinsed with deionized water.
3. The method for preparing integrated chip pads according to claim 1, characterized in that, Step S2 includes the following steps: S21. Immerse the glass slide in the aluminum zinc immersion solution and let it stand, and perform a zinc immersion on the aluminum pad layer (100); S22. After the first zinc precipitation, the slide is immersed in nitric acid solution and allowed to stand to remove the loose particles from the first zinc precipitation; S23. After zinc removal with nitric acid, the glass slide is immersed in aluminum zinc immersion solution and left to stand. A second zinc immersion is performed on the aluminum pad layer (100) to obtain the zinc layer (200).
4. The method for preparing integrated chip pads according to claim 1 or 3, characterized in that, In step S2, the soaking time for the first zinc immersion is longer than that for the second zinc immersion; after the first zinc immersion, nitric acid zinc stripping, and second zinc immersion are completed, deionized water is used for rinsing.
5. The method for preparing integrated chip pads according to claim 1, characterized in that, Step S3 includes the following steps: S31. Add the chemical nickel plating solution to a beaker, and then immerse the glass slide in the chemical nickel plating solution; S32. The beaker is heated in a water bath using a container to obtain the nickel layer (300).
6. The method for preparing integrated chip pads according to claim 1, characterized in that, Step S4 includes the following steps: S41. Add the chemical gold immersion solution to a beaker, and then immerse the glass slide in the chemical gold immersion solution; S42. The beaker is heated in a water bath using a container to obtain the gold layer (400).
7. The method for preparing integrated chip pads according to claim 5 or 6, characterized in that, In step S32 or S42, a separator is placed in the container, the beaker is placed on the separator, and then water bath heating is performed.
8. The method for preparing integrated chip pads according to claim 2, characterized in that, It also includes step S5: immersing the glass slide in the adhesive solution and sealing it to allow it to stand, so that the glass slide is separated from the aluminum pad layer (100).
9. The method for preparing integrated chip pads according to claim 1, characterized in that, After completing steps S1, S2, S3, and S4, each step is rinsed with deionized water.
10. A pad prepared by the method for preparing an integrated chip pad according to any one of claims 1 to 9, characterized in that, It includes an aluminum pad layer (100), a zinc layer (200), a nickel layer (300), and a gold layer (400) stacked from bottom to top.