Surface modified polyimide film-polyimide film low-temperature direct bonding method
By performing silica sol pretreatment and low-temperature pressure bonding on polyimide films, a high-strength bonding interface is generated, which solves the problems of complex processes and high costs in existing technologies, and achieves high reliability and low cost bonding effect, which is suitable for three-dimensional heterogeneous integration.
Patent Information
- Application Number
- CN202511970794.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-01-23
AI Technical Summary
Existing direct bonding technology for polyimide films suffers from complex processes, high thermal budgets, stringent equipment requirements, and high costs, making it difficult to meet the high cost-effectiveness and high reliability requirements of three-dimensional heterogeneous integration.
Pretreatment of polyimide films with silica sol and heating and pressurizing bonding under low temperature and pressure conditions generate abundant hydroxyl active sites and a uniform nano-silicon layer, which enhances the bonding strength of the bonding interface.
High-strength polyimide film bonding at low temperatures in a nitrogen atmosphere was achieved, meeting the reliability requirements of three-dimensional heterogeneous integration, reducing process difficulty and production costs, and possessing good potential for large-scale industrial production.
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Figure CN121378809A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of three-dimensional packaging, and particularly relates to a surface-modified polyimide film-polyimide film low-temperature direct bonding method. BACKGROUND
[0002] With the continuous reduction of semiconductor manufacturing process nodes and the gradual approach to the physical limit of atomic scale, the path of relying on traditional planar transistor size reduction to improve chip performance and integration is facing unprecedented challenges. In order to ensure the continuous growth of computing density and system computing power, it is urgent to explore new disruptive integration and architecture paradigms that can break through the limitations of classical Moore's Law. In this context, three-dimensional heterogeneous integration technology has emerged as the core solution: by vertically stacking different functional components such as logic, storage, and sensing, higher functional integration can be achieved on a limited chip area, significantly shortening the critical path delay, reducing signal transmission energy consumption, and achieving system-level collaborative optimization, significantly improving system performance.
[0003] In the three-dimensional heterogeneous integration technology system, hybrid bonding technology is the key to realizing high-density interconnection between chips. Although the current mainstream silicon dioxide dielectric-based hybrid bonding can achieve high interconnection density, it has defects such as narrow process window, strict requirements for surface state (such as flatness, cleanliness) and process conditions (such as temperature, pressure), which limit its application scenarios. In contrast, polymer bonding processes have the advantages of low-temperature processing, good surface compatibility, and strong adaptability to existing semiconductor manufacturing processes, and have been widely used in wafer-level packaging and three-dimensional integration. However, traditional polymer materials generally have insufficient high-temperature stability and poor moisture resistance, which can easily lead to degradation of the bonding interface and reduce reliability, making it difficult to meet the needs of high-density and high-reliability three-dimensional integration.
[0004] Polyimide (PI) is considered a potential dielectric material for replacing traditional polymers and achieving high-reliability hybrid bonding due to its excellent thermal stability, chemical inertness, and process compatibility. High-quality PI-PI direct bonding is a fundamental prerequisite for building polyimide-based hybrid bonding structures. Although PI materials have the advantages of lightweight, high flexibility, and excellent heat resistance, etc., due to their molecular structure characteristics, the intrinsic surface energy of the surface is low and the interface chemical reactivity is insufficient, making it difficult to obtain a stable and high-strength bonding interface during direct bonding. To solve this problem, existing technologies often use plasma activation treatment to increase the surface energy of PI, or use high-temperature hot pressing processes to promote interface chain segment migration and rearrangement, thereby enhancing the bonding strength. However, such methods have significant limitations: they need to be implemented in a controlled atmosphere (such as high vacuum, inert gas) or under higher thermal budget conditions, which requires higher sealing and temperature control accuracy of the equipment; at the same time, the process flow is complex, increasing the cost of bonding process, which is not conducive to large-scale industrial application. SUMMARY
[0005] Therefore, the present application aims to overcome the defects of the prior art, such as complicated process, high thermal budget, strict equipment requirements, and high cost, and to provide a surface-modified polyimide film low-temperature direct bonding method.
[0006] To achieve the above object, the present application adopts the following technical solutions: A surface-modified polyimide film low-temperature direct bonding method, comprising the following steps: First, a clean polyimide film is pretreated with silica sol to obtain a polyimide film to be bonded. Then, the polyimide film to be bonded is pressurized and bonded in a nitrogen atmosphere.
[0007] Preferably, the pretreatment method is as follows: the clean polyimide film is placed on a sample holder, the sample holder is placed in a beaker containing silica sol, and the silica sol liquid is made to cover the polyimide film, and ultrasonic treatment is performed for 10-20 min; then the sample is taken out and the surface is blown dry with nitrogen to obtain the polyimide film to be bonded.
[0008] Preferably, the mass concentration of the silica sol is 1.5-7.5 wt%.
[0009] Preferably, the heating temperature of the heating and pressurized bonding is 240-280℃, the pressure is 640-1080N, and the holding and pressurizing time is 5-20 min.
[0010] Preferably, the method for obtaining the clean polyimide film comprises ultrasonic cleaning of the polyimide film. The ultrasonic cleaning comprises sequentially performing acetone ultrasonic cleaning, anhydrous ethanol ultrasonic cleaning, and deionized water ultrasonic cleaning.
[0011] The present application has the following advantages: The application provides a surface-modified polyimide film-polyimide film low-temperature direct bonding method, which comprises two key steps of silica sol pretreatment and heating and pressure bonding, and is simple and controllable in process. The core advantage is that a high-efficiency bonding interface is constructed through precise interaction between the silica sol and the surface of the polyimide film: on the one hand, the silica sol can react with the surface of the polyimide film to generate a large number of hydroxyl active sites, thereby significantly improving the surface energy and the interface chemical reaction activity of the film, and enhancing the bonding strength of the bonding interface; on the other hand, the presence of the silica sol can form a uniform nanosilicon layer on the surface of the polyimide film, which can serve as an excellent interface transition medium to ensure the stable progress of the bonding process under low-temperature and pressure conditions, and finally realize the high-strength direct bonding of the polyimide film-polyimide film in a nitrogen atmosphere. It has been found through actual measurement that the shear strength of the polyimide film-polyimide film bonding surface obtained by using the bonding method provided by the application can reach 18.8 MPa or more, which fully meets the reliability requirements of three-dimensional heterogeneous integration. In addition, the process of the application does not require complex equipment and strict environmental control, significantly reduces the process difficulty and production cost, has good industrial large-scale production potential, and provides key support for the industrial application of polyimide-based three-dimensional heterogeneous integration technology. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 The figure is a bonding flowchart of the application, in which the number 11 represents a second polyimide film, the number 12 represents a first polyimide film, the number 21 represents a siloxyl layer on the surface of the second polyimide film, and the number 22 represents a siloxyl layer on the surface of the first polyimide film. Figure 2 The figure is a real object picture of the polyimide film before and after the silica sol treatment in Example 1, Figure 2 in which (a) corresponds to before the treatment, Figure 2 and (b) corresponds to after the treatment.
[0013] Figure 3 The figure is an SEM picture of the bonding interface of the polyimide film after the bonding in Example 1.
[0014] Figure 4 The figure is a bonding strength comparison chart of the products after the bonding in Examples 1-4.
[0015] Figure 5 The figure is a bonding strength comparison chart of the products after the bonding in Examples 1, 5-7. DETAILED DESCRIPTION
[0016] As shown in Figure 1 , the application provides a surface-modified polyimide film-polyimide film low-temperature direct bonding method, which comprises the following steps: First, a clean polyimide film is pretreated by using a silica sol to obtain a polyimide film to be bonded; Then, the polyimide film to be bonded is heated and pressure-bonded in a nitrogen atmosphere.
[0017] In a preferred embodiment, the method for pretreatment is as follows: the clean polyimide film is placed on a sample holder, the sample holder is placed in a beaker containing silica sol, and the silica sol liquid is made to cover the polyimide film, and ultrasonic treatment is performed for 10-20 min; then the sample is taken out and the surface is blown dry with nitrogen to obtain the polyimide film to be bonded.
[0018] In a preferred embodiment, the mass concentration of the silica sol is 1.5-7.5 wt%.
[0019] In a preferred embodiment, the heating temperature of the heating and pressure bonding is 240-280℃, the pressure is 640-1080 N, and the holding time is 5-20 min.
[0020] In a preferred embodiment, the method for obtaining the clean polyimide film comprises ultrasonic cleaning of the polyimide film. The frequency of the ultrasonic cleaning is preferably 20-50 KHz, and more preferably 40 KHz. The ultrasonic cleaning preferably comprises sequential acetone ultrasonic cleaning, anhydrous ethanol ultrasonic cleaning, and deionized water ultrasonic cleaning. The time of the acetone ultrasonic cleaning is preferably 4-6 min, and more preferably 5 min, and the number of times is preferably 2-3 times; the time of the anhydrous ethanol ultrasonic cleaning is preferably 4-6 min, and more preferably 5 min, and the number of times is preferably 2-3 times; and the time of the deionized water ultrasonic cleaning is preferably 4-6 min, and more preferably 5 min, and the number of times is preferably 2-3 times.
[0021] In a preferred embodiment, after the ultrasonic cleaning, the cleaned polyimide film is further blown dry with nitrogen.
[0022] In a preferred embodiment, the heating and pressure bonding is performed in the bonding cavity of a chip bonder.
[0023] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.
[0024] Example 1 In this example, two pieces of polyimide film (the size of the second polyimide film is 6 mm x 6 mm, and the size of the first polyimide film is 10 mm x 10 mm) are bonded as follows: 1. Ultrasonic cleaning Two polyimide films were sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water. The ultrasonic frequency was 40 kHz, each cleaning session lasted 5 minutes, and each solvent was used twice. The cleaned polyimide films were then dried with nitrogen gas.
[0025] 2. Pretreatment A clean polyimide film was placed on a sample holder, which was then placed in a beaker containing 5 wt% silica sol, ensuring the silica sol completely submerged the polyimide film. The sample was then sonicated for 15 minutes. Afterward, the sample was removed and dried with nitrogen gas to obtain the polyimide film to be bonded. The sonication of the silica sol generates abundant hydroxyl active sites on the surface of the polyimide film, increasing the surface energy and interfacial chemical reactivity, thereby enhancing the bonding strength at the bonding interface. Simultaneously, the presence of the silica sol forms a uniform nano-silicon layer on the surface of the polyimide film, which serves as an excellent interfacial transition medium, ensuring the stable progress of the bonding process under low-temperature and high-pressure conditions.
[0026] 3. Heating and pressurizing bonding In a nitrogen atmosphere, the polyimide films to be bonded are heated to a bonding temperature of 280°C, kept at a constant temperature and subjected to a pressure of 1080N for 15 minutes to achieve bonding of the two polyimide films.
[0027] Figure 2 These are actual images of the polyimide film before and after silica sol treatment. Figure 2 (a) in the text corresponds to before processing. Figure 2 (b) corresponds to the post-treatment. The figure shows that silica sol can effectively form a uniform nano-silicon layer on the surface of the polyimide film.
[0028] Figure 3 The SEM image shows the bonding interface of the polyimide film bonded to complete the bonding process. It can be seen from the image that the bonding of the polyimide film is very good, with a continuous bonding interface and almost no pores.
[0029] Example 2 In this embodiment, two polyimide films of the same size as those in Example 1 are bonded using the same method as in Example 1, with the only difference being that the bonding temperature is 220°C.
[0030] Example 3 In this embodiment, two polyimide films of the same size as those in Example 1 are bonded using the same method as in Example 1, with the only difference being that the bonding temperature is 240°C.
[0031] Example 4 This example was bonded two pieces of polyimide film with the same size as Example 1 according to the same method as Example 1, the only difference being that the bonding temperature was 260°C.
[0032] Example 5 This example was bonded two pieces of polyimide film with the same size as Example 1 according to the same method as Example 1, the only difference being that the mass concentration of the silica sol used for pretreatment was 1.5 wt%.
[0033] Example 6 This example was bonded two pieces of polyimide film with the same size as Example 1 according to the same method as Example 1, the only difference being that the mass concentration of the silica sol used for pretreatment was 3 wt%.
[0034] Example 7 This example was bonded two pieces of polyimide film with the same size as Example 1 according to the same method as Example 1, the only difference being that the mass concentration of the silica sol used for pretreatment was 7.5 wt%.
[0035] The polyimide bonded bodies after bonding of Examples 1-7 were tested for bonding strength (shear strength) using a shear force tester, and the test results are shown in Table 1. Figure 4 and Figure 5 The bonding strength of the product after bonding of Example 1 (bonding temperature 280°C) was 18.8 MPa, the bonding strength of the product after bonding of Example 2 (bonding temperature 220°C) was 2.5 MPa, the bonding strength of the product after bonding of Example 3 (bonding temperature 240°C) was 3.6 MPa, the bonding strength of the product after bonding of Example 4 (bonding temperature 260°C) was 11.3 MPa, the bonding strength of the product after bonding of Example 5 (mass concentration of silica sol for pretreatment 1.5 wt%) was 6.3 MPa, the bonding strength of the product after bonding of Example 6 (mass concentration of silica sol for pretreatment 3 wt%) was 13.6 MPa, and the bonding strength of the product after bonding of Example 7 (mass concentration of silica sol for pretreatment 7.5 wt%) was 12.1 MPa. As the bonding temperature increased, the bonding strength gradually increased. After fixing the temperature at 280°C, the bonding strength gradually increased as the mass concentration of the silica sol for pretreatment increased. However, the bonding strength decreased when the mass concentration of the silica sol for pretreatment exceeded 7.5 wt%. The reason for this is that a high concentration of silica sol, although having a high coverage rate, can result in the formation of a relatively thick nanosilicon layer on the surface. A nanolayer that is too thick can hinder direct contact between the two PI films and limit the crosslinking reaction of the interfacial hydroxyl groups with the PI molecular chains, thereby reducing the bonding strength.
[0036] Note: The bonding strength obtained by the test of the present application is the average value obtained by testing three samples bonded under the same process conditions in each example respectively. In fact, in the shear force test, the direction of the tool applying the pushing force may not be completely parallel to the bonding interface of the sample, so the actual bonding force is greater than the measured shear force.
[0037] The above only describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.
Claims
1. A method for surface-modified polyimide film-polyimide film low-temperature direct bonding, characterized by, The method comprises the following steps: First, a cleaned polyimide film is pretreated by using a silica sol to obtain a bonding polyimide film; Then, the bonding polyimide film is heated and pressurized in a nitrogen atmosphere.
2. The method of claim 1, wherein the surface-modified polyimide film is a polyimide film having a surface modified by a silane coupling agent. The pretreatment method is as follows: the cleaned polyimide film is placed on a sample holder, the sample holder is placed in a beaker containing the silica sol, the silica sol liquid is made to cover the polyimide film, and ultrasonic treatment is performed for 10-20 min; then the sample is taken out and the surface is blown dry with nitrogen to obtain the bonding polyimide film.
3. A method for low temperature direct bonding of surface-modified polyimide films according to claim 1 or 2, characterized in that: The mass concentration of the silica sol is 1.5-7.5 wt%.
4. A method for low-temperature direct bonding of surface-modified polyimide films to polyimide films according to claim 1 or 2, characterized in that: The heating temperature of the heating and pressurization bonding is 240-280 ℃, the pressure is 640-1080 N, and the holding time is 5-20 min.
5. A method for low-temperature direct bonding of surface-modified polyimide films to polyimide films according to claim 1 or 2, characterized in that: The cleaning method of the polyimide film comprises ultrasonic cleaning.
6. A method for surface-modified polyimide film-polyimide film low temperature direct bonding according to claim 5, characterized by: The ultrasonic cleaning comprises sequentially performing acetone ultrasonic cleaning, anhydrous ethanol ultrasonic cleaning and deionized water ultrasonic cleaning.