A filling process of micropores in an interconnection structure and a filling apparatus thereof

Abstract

The present application belongs to the field of electronic materials and microelectronic packaging technology, and particularly relates to a filling process and filling equipment for micropores in an interconnection structure, comprising the following steps: A. preparing core-shell microcapsules; wherein the core-shell microcapsules comprise a liquid metal inner core and a conductive outer shell layer arranged in sequence from inside to outside, and the raw material of the liquid metal inner core comprises a liquid metal with a melting point less than 30 DEG C; B. mixing copper nanoparticles, core-shell microcapsules, a dispersing agent and water uniformly to obtain a composite filling slurry; wherein the sintering temperature of the copper nanoparticles is less than the decomposition temperature of the conductive outer shell layer; C. filling the composite filling slurry into micropores in the interconnection structure and calcining under an inert atmosphere. The filling process for micropores in an interconnection structure proposed by the present application can not only effectively fill micropores, but also realize conductive self-repair of microcracks generated in the subsequent use process, thereby improving the long-term reliability of the interconnection structure.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials and microelectronic packaging technology, and particularly relates to a filling process and filling equipment for micropores in interconnect structures. Background Technology

[0002] With the increasing application of electronic products, the demand for interconnect structures such as small-sized and powerful integrated circuits and circuit boards is also increasing. In the manufacturing process of interconnect structures, microvias (including through-holes and / or blind holes) with metallized hole walls are usually set on each layer of the interconnect structure. The interconnection between layers is achieved by filling the holes, thereby reducing latency, reducing power consumption and improving integration. This plays a crucial role in advanced packaging technology fields such as 2.5D / 3D packaging, wafer-level chip-scale packaging and system-in-package.

[0003] Traditional methods for filling micropores mainly rely on copper electroplating. Although the technology is mature, this process has inherent drawbacks such as complex procedures and long processing times. Furthermore, due to uneven convection of the electroplating solution within the micropores, defects such as voids and gaps can easily occur, affecting the conductivity reliability of the product.

[0004] To overcome the aforementioned shortcomings, existing technologies have developed low-temperature sintering filling processes based on nano-metal particles (especially copper nanoparticles). This method involves filling micropores with a slurry of copper nanoparticles and then sintering it. The high surface energy of the copper nanoparticles enables densification, resulting in a filler with excellent electrical conductivity and achieving effective filling of micropores.

[0005] However, both electroplating copper and sintering nanoparticles face significant long-term reliability challenges. The reasons are as follows: Due to the substantial difference in thermal expansion coefficients between the filler and the interconnect matrix material (such as FR-4 and ceramics), cyclic thermal stresses are generated during subsequent use. These stresses can easily lead to delamination and cracking at the interface between the filler and the micropores; furthermore, they can easily induce microcracks within the filler (especially where sintering defects or weak grain boundaries exist). These microcracks will cause a sharp increase in the local resistance of the interconnect structure, unstable signal transmission, and even open circuits, seriously threatening the service life of the interconnect structure.

[0006] To address this challenge, the concept of self-healing has been introduced. Current self-healing technologies mainly include intrinsic and extrinsic self-healing techniques, with extrinsic self-healing technology attracting attention due to its high repair efficiency and minimal impact on the initial properties of the substrate. Its principle involves encapsulating a repair agent within microcapsules, which are then pre-dispersed in a copper nanoparticle slurry to form a composite filling slurry. When microcracks develop in the material, the stress at the crack tip causes the microcapsules to rupture, releasing the repair agent and achieving repair through a curing reaction. However, directly applying existing microcapsule technology to micropore filling faces a series of fundamental technical bottlenecks, as follows: (1) Functional failure: Traditional repair agents (such as monomers and solvents) are mostly insulators. Even if the physical continuity of the crack is successfully repaired, the necessary conductive function cannot be restored. (2) Problem introduced: How to uniformly introduce and stably exist microcapsules in narrow deep pore structures without interfering with the initial filling and densification of copper nanoparticles is a tricky process problem. (3) Process compatibility: The sintering temperature of copper nanoparticles is usually higher than 220℃, which requires the microcapsules to maintain structural integrity and thermal stability at this high temperature to avoid premature rupture or decomposition; (4) Triggering and repair effectiveness: It must be ensured that when microcracks are generated inside the filler, the local stress can effectively trigger the microcapsule rupture, and the released repair agent must be able to wet the metal surface and fill the crack, and rebuild the highly conductive path through a reliable mechanism.

[0007] The existence of the above problems means that even if microcapsules are added to the composite filler slurry, they cannot effectively fill the micropores, and at the same time, they cannot achieve conductive self-repair of microcracks generated during subsequent use, resulting in low reliability of the interconnect structure. Summary of the Invention

[0008] The purpose of this invention is to propose a micro-hole filling process in an interconnect structure, which can not only effectively fill the micro-holes, but also achieve conductive self-repair of micro-cracks generated during subsequent use, thereby improving the long-term reliability of the interconnect structure and overcoming the shortcomings of the prior art.

[0009] Another objective of this invention is to provide a device for filling micropores in interconnect structures, which, in conjunction with the micropore filling process in interconnect structures, can effectively improve the technical problem of the inability to effectively fill micropores in the prior art at a lower equipment cost, while also enabling conductive self-repair of microcracks generated during subsequent use, thus helping to ensure filling reliability.

[0010] To achieve this objective, the present invention adopts the following technical solution: A filling process for microvias in an interconnect structure includes the following steps: A. Preparation of core-shell microcapsules; wherein the core-shell microcapsules comprise a liquid metal core and a conductive outer shell layer arranged sequentially from the inside to the outside, and the raw material of the liquid metal core comprises liquid metal with a melting point of less than 30°C; B. After uniformly mixing copper nanoparticles, core-shell microcapsules, dispersant and water, a composite filling slurry is obtained; wherein, the sintering temperature of the copper nanoparticles is lower than the decomposition temperature of the conductive outer shell layer; C. The composite filler slurry is filled into the micropores in the interconnect structure and calcined under an inert atmosphere.

[0011] Furthermore, in step A, the liquid metal includes either gallium or an indium-gallium alloy.

[0012] Further, in step A, the raw materials of the conductive outer shell layer, calculated by mass percentage, include 85-95% conductive material and 5-15% stress-sensitive material; The decomposition temperatures of both the conductive material and the stress-sensitive material are greater than the sintering temperature of the copper nanoparticles.

[0013] Furthermore, the conductive material includes at least two of poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate, polyaniline, polypyrrole, poly(3-alkylthiophene), poly(p-phenylenevinylene), polyfluorene, polycarbazole, polypentaphenylene, and poly(pyrrolethiophene). The stress-sensitive material includes either silica particles or glass powder.

[0014] Further, in step A, the particle size of the core-shell microcapsules is 1–1000 nm.

[0015] Further, in step B, the raw materials of the composite filler slurry, calculated by mass percentage, include 50-60% copper nanoparticles, 2-6% core-shell microcapsules, 1-2% dispersant, and 35-45% water.

[0016] Furthermore, in step B, the particle size of the copper nanoparticles is 5–500 nm.

[0017] Further, in step C, the calcination curve is as follows: the temperature is increased from room temperature to 100-350°C at a heating rate of 1-10°C / min, and then held at that temperature for 0.2-0.5 hours.

[0018] Further, in step C, the filling method is as follows: The initial filling was carried out under a vacuum of -10 to -50 kPa. Deep filling is performed under a vacuum of -80 to -100 kPa; Let it stand for 0.5 to 1 minute under normal pressure.

[0019] A device for filling micropores in an interconnect structure, used to implement the above-mentioned filling process for micropores in an interconnect structure, includes a platform moving device, an optical detection device, a data acquisition and analysis device, a slurry filling device, a pressure regulating device, and a vacuum chamber. The pressure regulating device is connected to the vacuum chamber, and the pressure regulating device is used to adjust the vacuum level of the vacuum chamber; The optical detection device, the slurry filling device, and the platform moving device are all located inside the vacuum cavity. The optical detection device and the slurry filling device are located on opposite sides above the platform moving device, and the platform moving device can move relative to the optical detection device and the slurry filling device in the horizontal and vertical directions. The acquisition and analysis device is installed on the top of the optical detection device, and the acquisition and analysis device is electrically connected to the optical detection device, the slurry filling device and the platform moving device. The platform moving device is used to place the interconnect structure, the optical detection device is used to acquire micro-hole images of the interconnect structure, the acquisition and analysis device is used to analyze the micro-hole images of the interconnect structure, accurately locate the coordinates of all micro-holes, and generate moving path instructions and filling instructions, and the slurry filling device is used to fill the micro-holes of the interconnect structure with composite filling slurry.

[0020] The technical solution provided by this invention may include the following beneficial effects: 1. During calcination, because the decomposition temperature of the conductive outer shell layer in the core-shell microcapsules is higher than the sintering temperature of the copper nanoparticles, the core-shell microcapsules maintain their structural integrity, dispersing and embedding within the filler. The conductive outer shell layer endows the core-shell microcapsules with conductivity, allowing them to function as components of a conductive network. This minimizes the impact on the initial conductivity of the filler, ensuring that the micropores are effectively and highly conductively filled.

[0021] 2. When microcracks develop in the filler during subsequent use, whether they occur inside the filler or at the interface between the filler and the micropores (i.e., the filler interface), as long as the microcrack propagation path passes through or is close to the core-shell microcapsule, and the stress at the microcrack tip reaches the rupture threshold of the conductive outer shell layer of the core-shell microcapsule, the conductive outer shell layer will rupture, releasing liquid metal with a melting point below 30°C from the liquid metal core. This liquid metal has extremely high electrical conductivity and excellent flow wettability, which can quickly fill and bridge the gaps in the microcracks, and even backfill the cavity of the core-shell microcapsule. Simultaneously, the conductive outer shell layer remnants after rupture can still participate in conduction, thus achieving precise and efficient repair of the microcracks. It should be noted that during the sintering and filling process, some core-shell microcapsules will naturally distribute in or near the interface region between the filler and the micropores. Therefore, when microcracks are generated at the interface between the filler and the micropores due to differences in thermal expansion coefficients, their propagation can also trigger the core-shell microcapsules in that region to release liquid metal to effectively repair the interface cracks, thereby restoring the mechanical bonding strength and electrical continuity of the interface. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a micro-hole filling device in an interconnect structure according to the present invention.

[0023] The components include: platform moving device 1, placement platform 11, moving base 12, optical detection device 2, acquisition camera 21, light source 22, acquisition and analysis device 3, slurry filling device 4, air pressure regulating device 5, slurry conveying device 6, pressurizing pump 61, slurry storage tank 62, and conveying pipe 63. Detailed Implementation

[0024] This technical solution provides a filling process for microvias in an interconnect structure, including the following steps: A. Preparation of core-shell microcapsules; wherein the core-shell microcapsules comprise a liquid metal core and a conductive outer shell layer arranged sequentially from the inside to the outside, and the raw material of the liquid metal core comprises liquid metal with a melting point of less than 30°C; B. After uniformly mixing copper nanoparticles, core-shell microcapsules, dispersant and water, a composite filling slurry is obtained; wherein, the sintering temperature of the copper nanoparticles is lower than the decomposition temperature of the conductive outer shell layer; C. The composite filler slurry is filled into the micropores in the interconnect structure and calcined under an inert atmosphere.

[0025] To address the common problem in existing micropore filling processes that fail to effectively fill micropores while simultaneously enabling conductive self-repair of microcracks generated during subsequent use, this technical solution proposes a micropore filling process for interconnect structures. This process includes A (preparation of core-shell microcapsules), B (preparation of composite filling slurry), and C (filling and calcination). By optimizing the filling process and raw materials, this method not only effectively fills micropores but also enables conductive self-repair of microcracks generated during subsequent use, thereby improving the long-term reliability of the interconnect structure to meet practical application requirements.

[0026] Specifically, the composite filling slurry of this technical solution includes copper nanoparticles, core-shell microcapsules, a dispersant, and water. The composite filling slurry is then filled into the micropores of the interconnect structure and calcined under an inert atmosphere. During this process, the water in the composite filling slurry evaporates, and the copper nanoparticles form a metallurgical bond through atomic diffusion and dynamic recrystallization, constituting a dense filler. Simultaneously, the copper nanoparticles and micropores also form a metallurgical bond through atomic thermal diffusion, thereby establishing a strong and tough metallic bond connection between them, ensuring the interfacial bonding strength and electrical continuity between the filler and the micropores.

[0027] Furthermore, during the calcination process, because the decomposition temperature of the conductive outer shell layer in the core-shell microcapsules is higher than the sintering temperature of the copper nanoparticles, the core-shell microcapsules maintain their structural integrity, dispersing and embedding within the filler. The conductive outer shell layer endows the core-shell microcapsules with conductivity, allowing them to function as components of a conductive network. This minimizes the impact on the initial conductivity of the filler, ensuring that the micropores are effectively and highly conductively filled.

[0028] When microcracks develop in the filler during subsequent use, whether they originate within the filler or at the interface between the filler and the micropores (i.e., the filler interface), as long as the microcrack propagation path passes through or is close to the core-shell microcapsule, and the stress at the microcrack tip reaches the rupture threshold of the conductive outer shell layer of the core-shell microcapsule, the conductive outer shell layer will rupture, releasing liquid metal with a melting point below 30°C from the liquid metal core. This liquid metal possesses extremely high electrical conductivity and excellent flow wettability, allowing it to rapidly fill and bridge the gaps in the microcracks, and even backfill the cavities of the core-shell microcapsule. Simultaneously, the conductive outer shell layer remnants, even after rupture, can still participate in conductivity, thus achieving precise and efficient repair of the microcracks. It should be noted that during the sintering and filling process, some core-shell microcapsules will naturally distribute at or near the interface region between the filler and the micropores. Therefore, when microcracks are generated at the interface between the filler and the micropores due to differences in thermal expansion coefficients, their propagation can also trigger the core-shell microcapsules in that region to release liquid metal to effectively repair the interface cracks, thereby restoring the mechanical bonding strength and electrical continuity of the interface.

[0029] In summary, this approach ensures initial filling quality by utilizing the core-shell microcapsules as a stable conductive dopant phase during sintering; subsequently, they transform into active repair units, releasing liquid metal as needed during use. This dual mechanism synergistically achieves high-quality micropore filling and conductive self-repair during use, thereby enhancing the long-term reliability of the interconnect structure.

[0030] Furthermore, the composite filling slurry based on copper nanoparticles in this technical solution, thanks to its nano-size effect and good rheological properties, can effectively penetrate and initially fill deep pores through capillary action. Secondly, the composite filling slurry in this technical solution can achieve conductive self-healing during later use, fundamentally overcoming the bottleneck of traditional high aspect ratio filling which is prone to defects due to stress concentration and ultimately leads to failure. Thus, even if the aspect ratio of the micropores (the aspect ratio refers to the ratio of depth to pore diameter) is as high as 50:1, it can still ensure the process feasibility and long-term reliability of filling.

[0031] Secondly, the core of this technical solution is liquid metal, which is itself a highly conductive material. After it is released, it can quickly fill and bridge the two ends of the crack, fundamentally ensuring the restoration of conductivity after repair, rather than insulation and sealing, thus avoiding the technical problem of functional failure even after repair.

[0032] Meanwhile, this technical solution utilizes a dispersant to ensure uniform and stable mixing of core-shell microcapsules and copper nanoparticles in the composite filling slurry. This allows the core-shell microcapsules to flow into the micropores along with the composite filling slurry during filling, achieving a natural and uniform distribution without acting as foreign matter and interfering with particle stacking. This avoids interfering with the initial filling and densification of copper nanoparticles, thus solving the problem of introduction.

[0033] In addition, the decomposition temperature of the conductive outer shell layer in this technical solution is higher than the sintering temperature of copper nanoparticles, which ensures that the conductive outer shell layer maintains structural integrity during the sintering process, thereby protecting the liquid metal core and preventing premature cracking or decomposition, thus improving process compatibility.

[0034] Secondly, as described above, after calcination, the conductive outer shell becomes part of the filler. When microcracks are generated and propagate to the core-shell microcapsule, the conductive outer shell will rupture due to localized stress concentration. Liquid metals with a melting point <30℃ remain liquid at room temperature, possessing excellent fluidity and intrinsic wettability to metal surfaces. They can automatically fill capillary cracks and rebuild conductive paths by forming direct metal-to-metal connections, thus overcoming the shortcomings of existing technologies that cannot trigger and effectively repair these cracks.

[0035] It should be noted that the micropores in this technical solution refer to micropores with metallized pore walls. Furthermore, in existing technologies, micropores requiring conductive filling for electrical interconnection all have metallized pore walls. Therefore, the micropores in this technical solution, having metallized pore walls, are well-known in the art. Simultaneously, the micropores include through-holes and / or blind holes. When the micropore is a through-hole, a filter membrane needs to be placed at the bottom of the through-hole, and the pore size of the filter membrane is smaller than the particle size of the copper nanoparticles, thereby preventing copper nanoparticles from falling directly into the through-hole. Additionally, the filter membrane material can be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAC), etc. The specific material type can be selected according to actual needs, and no specific material type is limited here.

[0036] It should be further noted that the core-shell microcapsules of this technical solution are prepared using an in-situ polymerization method commonly used in existing technologies; the specific method will not be described in detail here. The inert atmosphere can be a nitrogen atmosphere or an argon atmosphere, etc., and the specific type is not limited here.

[0037] To further clarify, in step A, the liquid metal includes either gallium or an indium-gallium alloy.

[0038] Both gallium and indium gallium alloys possess high electrical conductivity and low melting points, remaining liquid at room temperature. This allows them to flow, fill, and bridge microcracks during the repair process. Therefore, this technical solution preferably uses either gallium or indium gallium alloys as the liquid metal. This not only improves the conductive self-healing performance but also allows for the selection of a suitable liquid metal based on actual needs, enhancing the flexibility of the solution.

[0039] To further explain, in step A, the raw materials of the conductive outer shell layer, calculated by mass percentage, include 85-95% conductive material and 5-15% stress-sensitive material; The decomposition temperatures of both the conductive material and the stress-sensitive material are greater than the sintering temperature of the copper nanoparticles.

[0040] This technical solution optimizes the raw materials for the conductive outer shell layer, including conductive and stress-sensitive materials. This allows the conductive materials to ensure the conductivity of the outer shell layer, while the stress-sensitive materials, which readily form stress concentration points within the conductive outer shell layer, lower the rupture threshold of the core-shell microcapsules, making them more sensitive to microcracks. Simultaneously, the amounts of conductive and stress-sensitive materials added are limited to ensure that the core-shell microcapsules do not rupture under normal conditions (such as sintering and processing stress), but rupture promptly under microcrack stress (such as 0.2% strain), thereby achieving conductive self-healing.

[0041] Furthermore, this technical solution limits the decomposition temperatures of both the conductive material and the stress-sensitive material to be higher than the sintering temperature of the copper nanoparticles. This double protection ensures that the decomposition temperature of the conductive outer shell is higher than the sintering temperature of the copper nanoparticles. During the sintering process, the conductive outer shell maintains its structural integrity, thus protecting the liquid metal core and preventing premature cracking or decomposition, thereby improving the reliability of the repair effect.

[0042] Further explanation: the conductive material includes at least two of poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate, polyaniline, polypyrrole, poly(3-alkylthiophene), poly(p-phenylenevinylene), polyfluorene, polycarbazole, polypentaphenylene, and poly(pyrrolethiophene). The stress-sensitive material includes either silica particles or glass powder.

[0043] Poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate, polyaniline, polypyrrole, poly(3-alkylthiophene), poly(p-phenylenevinylene), polyfluorene, polycarbazole, polypentaphenylene, and poly(3-alkylthiophene) all possess good electrical conductivity, thermal stability, and film-forming properties, and can maintain structural integrity during sintering. Therefore, this technical solution preferably uses the above-mentioned types of conductive materials, which is beneficial to ensuring the performance of the conductive materials.

[0044] Furthermore, both silica particles and glass powder possess characteristics of high brittleness, chemical stability, and low cost. They also readily form stress concentration points in the conductive outer shell, lowering the fracture threshold of the core-shell microcapsules and making them more sensitive to microcracks. Therefore, this technical solution preferably uses the aforementioned types of stress-sensitive materials to improve conductive self-healing performance.

[0045] To further explain, in step A, the particle size of the core-shell microcapsules is 1–1000 nm.

[0046] This technical solution limits the particle size of core-shell microcapsules, which not only allows the core-shell microcapsules to be uniformly dispersed in the composite filler slurry and effectively fill the micropores, but also makes their particle size match the microcrack size, especially the microcracks with a length of 3-10000nm. This ensures that the stress at the microcrack tip can effectively trigger rupture and release sufficient liquid metal to repair the microcrack.

[0047] To further explain, in step B, the raw materials of the composite filler slurry, calculated by mass percentage, include 50-60% copper nanoparticles, 2-6% core-shell microcapsules, 1-2% dispersant, and 35-45% water.

[0048] This technical solution optimizes the addition amounts of each raw material in the composite filler slurry, allowing each material to fully utilize its properties. This ensures the performance of the resulting composite filler slurry, thereby guaranteeing both filling and self-healing effects. It should be noted that the dispersant can be ammonium polyacrylate.

[0049] Preferably, the mixing ratio of the core-shell microcapsule to the copper nanoparticle is 1:(10-30) by mass ratio.

[0050] This technical solution, by limiting the mixing ratio of core-shell microcapsules and copper nanoparticles, facilitates the uniform dispersion of core-shell microcapsules in the filler after calcination of the composite filler slurry. This not only helps to effectively repair microcracks but also does not affect the sintering densification and initial conductivity of the copper nanoparticles.

[0051] To further clarify, in step B, the particle size of the copper nanoparticles is 5–500 nm.

[0052] This technical solution improves the flexibility of the solution by allowing the selection of copper nanoparticles with appropriate particle size according to actual needs through the control of the particle size.

[0053] To further explain, in step C, the calcination curve is as follows: the temperature is increased from room temperature to 100-350℃ at a heating rate of 1-10℃ / min, and then held at that temperature for 0.2-0.5h.

[0054] This technical solution limits the calcination curve, allowing copper nanoparticles to diffuse and densify on the surface under this calcination curve, while preventing the conductive outer shell from splitting, thereby avoiding premature failure of the core-shell microcapsule.

[0055] To further explain, in step C, the filling method is as follows: The initial filling was carried out under a vacuum of -10 to -50 kPa. Deep filling is performed under a vacuum of -80 to -100 kPa; Let it stand for 0.5 to 1 minute under normal pressure.

[0056] This technical solution optimizes the filling method. Initial filling introduces the composite filler slurry to the bottom of the micropores and removes most of the residual gas. Then, deep filling is performed under a higher vacuum environment to completely fill the micropores with the composite filler slurry and remove any remaining gas. Finally, the slurry is allowed to stand at atmospheric pressure for 0.5–1 minute, utilizing its surface tension to smooth it and prevent voids at the top. Therefore, this segmented filling method reduces capillary resistance and gas retention, ensuring continuous filling of the composite filler slurry from the bottom to the top of the pore, thereby improving the conductivity of the filler.

[0057] A device for filling micropores in an interconnect structure, used to realize the above-mentioned filling process of micropores in the interconnect structure, includes a platform moving device 1, an optical detection device 2, a data acquisition and analysis device 3, a slurry filling device 4, a pressure regulating device 5, and a vacuum chamber. The air pressure regulating device 5 is interconnected with the vacuum chamber, and the air pressure regulating device 5 is used to regulate the vacuum level of the vacuum chamber; The optical detection device 2, the slurry filling device 4, and the platform moving device 1 are all located inside the vacuum cavity. The optical detection device 2 and the slurry filling device 4 are located on opposite sides above the platform moving device 1, and the platform moving device 1 can move relative to the optical detection device 2 and the slurry filling device 4 in the horizontal and vertical directions. The acquisition and analysis device 3 is installed on the top of the optical detection device 2, and the acquisition and analysis device 3 is electrically connected to the optical detection device 2, the slurry filling device 4 and the platform moving device 1. The platform moving device 1 is used to place the interconnect structure, the optical detection device 2 is used to acquire micro-hole images of the interconnect structure, the acquisition and analysis device 3 is used to analyze the micro-hole images of the interconnect structure, accurately locate the coordinates of all micro-holes, and generate moving path instructions and filling instructions, and the slurry filling device 4 is used to fill the micro-holes of the interconnect structure with composite filling slurry.

[0058] This technical solution also proposes a device for filling micropores in interconnect structures, which, in conjunction with the micropore filling process in interconnect structures, can effectively improve the technical problem of the inability to effectively fill micropores in existing technologies at a lower equipment cost, while also enabling conductive self-repair of microcracks generated during subsequent use, thus helping to ensure filling reliability.

[0059] Specifically, the micropore filling device in the interconnect structure includes a platform moving device 1, an optical detection device 2, an acquisition and analysis device 3, a slurry filling device 4, a pressure regulating device 5, and a vacuum chamber. First, the pressure regulating device 5 evacuates the vacuum chamber to a preset vacuum level to eliminate gas interference. Then, the platform moving device 1 carries the interconnect structure, and the optical detection device 2 scans the interconnect structure and transmits the image to the acquisition and analysis device 3. The acquisition and analysis device 3 analyzes the image transmitted by the optical detection device 2, accurately locates the coordinates of all micropores in the interconnect structure, and generates movement path instructions and filling instructions. Next, the platform moving device moves the micropores in the interconnect structure one by one to below the slurry filling device 4 according to the movement path instructions of the acquisition and analysis device 3. After the movement is completed, the slurry filling device 4 injects a quantitative amount of composite filling slurry into each micropore according to the filling instructions of the acquisition and analysis device 3. This process is repeated until all micropores are filled. Finally, calcination is carried out in an inert environment to achieve high density and defect-free filling of the micropores.

[0060] Preferably, the platform moving device 1 includes a placement platform 11 and a moving base 12 connected sequentially from top to bottom. The placement platform 11 is located below the optical detection device 2 and the slurry filling device 4, and the placement platform 11 can move relative to the optical detection device 2 and the slurry filling device 4 in the horizontal and vertical directions via the moving base 12. The placement platform 11 is used to place interconnection structures.

[0061] This technical solution, through the above-mentioned settings, enables the placement platform 11 to place the interconnect structure, while the movable base 12 can move along the X, Y, and Z axes, ensuring the positioning accuracy and stability of the interconnect structure at the two key work stations of micropore detection and slurry filling, and improving the filling quality.

[0062] Preferably, the optical detection device 2 includes a data acquisition camera 21 and a light source 22 connected sequentially from top to bottom. The light source 22 is located above the platform moving device 1, and the data acquisition camera 21 is electrically connected to the data acquisition and analysis device 3.

[0063] Through the above-mentioned settings, this technical solution enables the light source 22 to uniformly illuminate the surface of the interconnect structure from top to bottom, resulting in clear optical contrast for features such as micropores. The camera 21 acquires high-quality images from an almost coaxial angle, minimizing shadow and reflection interference, thereby providing the acquisition and analysis device 2 with sharp outlines and rich details. This directly improves the system's accuracy and reliability in identifying the position, size, and morphology of micropores, providing a fundamental visual guarantee for subsequent accurate alignment and high-quality filling.

[0064] Preferably, it also includes a slurry conveying device 6, the outlet of which is connected to the inlet of the slurry filling device 4, and the slurry conveying device 6 is used to store the composite filling slurry and convey the composite filling slurry to the slurry filling device 4.

[0065] This technical solution, by setting up a slurry filling device 4, facilitates the centralized storage and stable transportation of composite filling slurry, thereby improving the efficiency of the filling process.

[0066] Preferably, the slurry conveying device 6 includes a pressure pump 61, a slurry storage tank 62, and a conveying pipe 63. The outlet of the slurry storage tank 62 is connected to the inlet of the slurry filling device 4 through the conveying pipe 63. The pressure pump 61 is used to pump the slurry located in the slurry storage tank 62 into the slurry filling device 4.

[0067] Through the above-mentioned settings, the pressure pump 61 plays an auxiliary role in the transportation of composite filler slurry, ensuring that the composite filler slurry can be transported to the end of the delivery pipe 63 (the end near the outlet of the delivery pipe 63) when micropore filling is not performed. At the same time, when micropore filling is performed, the transmission pressure of the composite filler slurry can be adjusted according to different air pressures to achieve segmented filling of the composite filler slurry.

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0069] Performance testing methods: Initial resistance: The sintered and filled sample was cut along a direction perpendicular to the micropore axis using a diamond wire cutter, and the cross-section was polished to expose the complete cross-section of the filler. Under optical microscopy, the probe of a four-probe tester was precisely placed against the center region of the cross-section of a single filler for measurement. Ten fillers were randomly selected from the same batch of samples for testing, and their average resistance was used as the initial resistance reference value (R0).

[0070] Resistance recovery rate: A micro-force testing system is used to apply a preset load (e.g., to generate a controllable microcrack with a length of 3-10000 nm) to the central region of the filler cross-section where the initial resistance has been measured. Subsequently, the repaired resistance value (R0) is measured in situ using a four-probe tester. According to the formula: Resistance recovery rate = (R0 / R) Calculate the resistance recovery rate by multiplying the resistance recovery rate by 100%. If the resistance recovery rate is ≥95%, the conductive path is considered to have been effectively repaired.

[0071] Filling integrity: Backscattered electron imaging is performed on the polished cross-section of the filler using a scanning electron microscope. Threshold segmentation is performed on the image by image analysis software to distinguish the filler area from the void area, and the percentage of the filling area in the total pore area is automatically calculated. Meanwhile, the percentage of the filling area in the total pore area of multiple cross-sections such as the pore top, pore middle and pore bottom along the pore depth direction is checked. If the percentage of the filling area of all detected cross-sections is ≥98% and no through voids are found, the filling integrity is determined to be qualified.

[0072] Example 1 A. Prepare core-shell microcapsules with gallium-indium alloy as the liquid metal core and poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate and silica particles as the conductive outer shell layer; the specific preparation method is as follows: mix 0.25 g of sodium dodecyl sulfate with 50 mL of deionized water evenly to obtain a sodium dodecyl sulfate solution; add 5.0 g of gallium-indium alloy into the sodium dodecyl sulfate solution, and conduct ultrasonic treatment for 10 min to obtain an emulsion; sequentially add 0.30 g of 3,4-ethylenedioxythiophene, 0.50 g of sodium polystyrene sulfonate and 0.05 g of silica particles into the emulsion to obtain a mixed solution; mix 0.50 g of ammonium persulfate with 10 mL of deionized water evenly to obtain an ammonium persulfate solution; under a nitrogen atmosphere, dropwise add the ammonium persulfate solution into the mixed solution, control the reaction temperature at 8-12°C, and continue stirring for 18 h to obtain a core-shell microcapsule suspension; centrifuge the core-shell microcapsule suspension at a rotation speed of 8000 r / min for 15 min, discard the supernatant to obtain a first precipitate; wash the first precipitate with a mixed solution of deionized water and absolute ethanol at a volume ratio of 1:1 until the filtrate is colorless and transparent to obtain a second precipitate; dry the second precipitate in a vacuum drying oven at 40°C for 12 h to obtain core-shell microcapsules with a particle size distribution of 30-80 nm; B. Mix 50% copper nanoparticles with a particle size of 50 nm, 5% core-shell microcapsules, 1% ammonium polyacrylate and 44% water calculated by mass percentage evenly to obtain a composite filling slurry; C. Fill the composite filling slurry into micropores with a pore diameter of 10 μm and a depth of 300 μm in the interconnection structure, and calcine under a nitrogen atmosphere; wherein the calcination curve is: heat from room temperature to 240°C at a heating rate of 5°C / min, then hold the temperature for 0.5 h; the filling method is: perform primary filling under a vacuum degree of -20 kPa; perform deep filling under a vacuum degree of -80 kPa; stand at atmospheric pressure for 0.5 min.

[0073] Example 2 A. Preparation of core-shell microcapsules with gallium as the liquid metal core and poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate, and glass powder as the conductive outer shell; the specific preparation method is as follows: 0.25g of sodium dodecyl sulfate is mixed evenly with 50ml of deionized water to obtain a sodium dodecyl sulfate solution; 5.0g of gallium is added to the sodium dodecyl sulfate solution, and ultrasonic treatment is performed for 10min to obtain an emulsion; 0.30g of 3,4-ethylenedioxythiophene, 0.50g of sodium polystyrene sulfonate, and 0.05g of glass powder are added sequentially to the emulsion to obtain a mixed solution; 0.50g of ammonium persulfate is mixed with 10ml of deionized water... After the water was mixed evenly, an ammonium persulfate solution was obtained. Under a nitrogen atmosphere, the ammonium persulfate solution was added dropwise to the mixed solution, the reaction temperature was controlled at 8-12℃, and the mixture was stirred continuously for 18 hours to obtain a core-shell microcapsule suspension. The core-shell microcapsule suspension was centrifuged at 7000 r / min for 18 min, and the supernatant was discarded to obtain the first precipitate. The first precipitate was washed with a 1:1 volume ratio of deionized water and anhydrous ethanol until the filtrate was colorless and transparent to obtain the second precipitate. The second precipitate was dried in a vacuum drying oven at 50℃ for 12 hours to obtain core-shell microcapsules with a particle size distribution of 30-80 nm. B. Mix 55% copper nanoparticles with a particle size of 60nm, 3% core-shell microcapsules, 2% ammonium polyacrylate and 40% water by mass percentage to obtain a composite filler slurry. C. The composite filler slurry is filled into micropores with a diameter of 20 μm and a depth of 30 μm in the interconnect structure and calcined under an argon atmosphere. The calcination curve is as follows: the temperature is increased from room temperature to 250℃ at a heating rate of 3℃ / min and then held at that temperature for 0.3h. The filling method is as follows: initial filling is carried out under a vacuum of -50kPa; deep filling is carried out under a vacuum of -80kPa; and the mixture is allowed to stand for 1min under normal pressure.

[0074] Example 3 A. Preparation of core-shell microcapsules with a gallium-indium alloy as the liquid metal core and polyaniline, sodium polystyrene sulfonate, and silica particles as the conductive outer shell; the specific preparation method is as follows: 0.25g of sodium dodecyl sulfate is mixed evenly with 50ml of deionized water to obtain a sodium dodecyl sulfate solution; 5.0g of gallium-indium alloy is added to the sodium dodecyl sulfate solution, and ultrasonic treatment is performed for 10min to obtain an emulsion; 0.30g of polyaniline, 0.50g of sodium polystyrene sulfonate, and 0.05g of silica particles are added sequentially to the emulsion to obtain a mixed solution; 0.50g of ammonium persulfate is mixed with 10ml of deionized water. After homogenization, an ammonium persulfate solution was obtained. Under a nitrogen atmosphere, the ammonium persulfate solution was added dropwise to the mixed solution, the reaction temperature was controlled at 8-12℃, and the mixture was stirred continuously for 18 hours to obtain a core-shell microcapsule suspension. The core-shell microcapsule suspension was centrifuged at 8000 r / min for 15 min, and the supernatant was discarded to obtain the first precipitate. The first precipitate was washed with a 1:1 volume ratio of deionized water and anhydrous ethanol until the filtrate was colorless and transparent to obtain the second precipitate. The second precipitate was dried in a vacuum drying oven at 40℃ for 12 hours to obtain core-shell microcapsules with a particle size distribution of 30-80 nm. B. Mix 60% copper nanoparticles with a particle size of 20nm, 4% core-shell microcapsules, 1% ammonium polyacrylate and 35% water by mass percentage to obtain a composite filler slurry. C. The composite filler slurry is filled into micropores with a diameter of 50 μm and a depth of 500 μm in the interconnect structure and calcined under a nitrogen atmosphere. The calcination curve is as follows: the temperature is increased from room temperature to 230℃ at a heating rate of 3℃ / min and then held at that temperature for 0.4h. The filling method is as follows: initial filling is carried out under a vacuum of -10kPa; deep filling is carried out under a vacuum of -90kPa; and the mixture is allowed to stand for 0.8min under normal pressure.

[0075] Comparative Example 1 The preparation method and raw materials of this comparative example are the same as those of Example 2. The difference is that the raw materials of the composite filler slurry in this comparative example do not contain core-shell microcapsules. That is, calculated by mass percentage, the raw materials of the composite filler slurry include 57% copper nanoparticles, 2% ammonium polyacrylate, and 41% water.

[0076] The fillers prepared in the examples and comparative examples were subjected to performance tests, and the results are shown in Table 1 below: Table 1. Test results of relevant performance of the filler

[0077] As can be seen from the test data in Table 1, this technical solution can not only effectively fill micropores and make the filler have good conductivity, but also achieve conductive self-repair of microcracks generated during subsequent use, thereby improving the long-term reliability of the interconnect structure to meet actual use requirements.

[0078] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A filling process for microvias in an interconnect structure, characterized in that, Includes the following steps: A. Preparation of core-shell microcapsules; wherein the core-shell microcapsules comprise a liquid metal core and a conductive outer shell layer arranged sequentially from the inside out, and the raw material of the liquid metal core comprises liquid metal with a melting point of less than 30°C; the raw material of the conductive outer shell layer comprises 85-95% conductive material and 5-15% stress-sensitive material by mass percentage; B. After uniformly mixing copper nanoparticles, core-shell microcapsules, dispersant and water, a composite filling slurry is obtained; wherein, the sintering temperature of the copper nanoparticles is lower than the decomposition temperature of the conductive material, and the sintering temperature of the copper nanoparticles is lower than the decomposition temperature of the stress-sensitive material. C. The composite filler slurry is filled into the micropores in the interconnect structure and calcined under an inert atmosphere.

2. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step A, the liquid metal includes either gallium or an indium gallium alloy.

3. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step A, the conductive material includes at least two of the following: poly(3,4-ethylenedioxythiophene), sodium polystyrene sulfonate, polyaniline, polypyrrole, poly(3-alkylthiophene), poly(p-phenylenevinylene), polyfluorene, polycarbazole, polypentaphenylene, and poly(pyrrolethiophene). The stress-sensitive material includes either silica particles or glass powder.

4. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step A, the particle size of the core-shell microcapsules is 1–1000 nm.

5. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step B, the raw materials of the composite filler slurry, calculated by mass percentage, include 50-60% copper nanoparticles, 2-6% core-shell microcapsules, 1-2% dispersant, and 35-45% water.

6. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step B, the copper nanoparticles have a particle size of 5–500 nm.

7. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step C, the calcination curve is as follows: the temperature is increased from room temperature to 100-350°C at a heating rate of 1-10°C / min, and then held at that temperature for 0.2-0.5 hours.

8. The microvia filling process in an interconnect structure according to claim 1, characterized in that, In step C, the filling method is as follows: The initial filling was carried out under a vacuum of -10 to -50 kPa. Deep filling is performed under a vacuum of -80 to -100 kPa; Let it stand for 0.5 to 1 minute under normal pressure.

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