A method for printing nano-copper assisted hybrid bonding process

Abstract

A method for printing nano-copper-assisted hybrid bonding technology includes the following steps: S1. Cleaning the surface of the chip to be bonded and pre-treating it in preparation for bonding; S2. Identifying surface defects and positional information of copper bumps on the surface to be bonded; S3. Printing fine-diameter nano-copper particles prepared by an electrospark ablation device onto the surface of the copper bumps to repair dishing defects, achieve surface flattening of the copper bumps, and form a nano-copper film to assist in low-temperature bonding; S4. Using a bonding machine to align and contact the printed chips, micro-heating is performed to achieve pre-bonding for hybrid bonding; S5. Passing in an inert protective gas to heat and perform low-temperature hybrid bonding. The purpose of the present invention is to provide a method for printing nano-copper-assisted hybrid bonding technology to address the current mainstream hybrid bonding problems of copper bumps prone to defects, poor bonding results, and high bonding temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid bonding and nanomaterials, and in particular to a method for printing nano-copper assisted hybrid bonding process. Background Art

[0002] As electronic devices evolve toward higher density, miniaturization, and higher performance, the demands on electronic packaging technology are increasing. Reliable interconnection between the chip and substrate is crucial for electronic packaging, and traditional soldering methods typically rely on tin-based solders. However, tin-based solders have numerous limitations, such as high-temperature operation that can damage sensitive components, thermal fatigue, and electromigration. Furthermore, some solders contain lead, which violates environmental regulations. Hybrid bonding technology, which combines mechanical and chemical bonding to achieve high-strength bonds, holds enormous potential for application. However, in hybrid bonding, the quality of the copper bump surface plays a crucial role in bonding performance. In practical applications, dishing defects, localized depressions on the copper bump surface, often occur. These defects lead to incomplete bonding contact and reduced joint mechanical properties. In recent years, nanometal materials, due to their high surface energy and excellent low-temperature sintering properties, have attracted attention in bonding technology. These particles can be densely sintered at relatively low temperatures, forming a highly conductive and mechanically strong interface. Therefore, developing a method that uses nozzle printing technology to uniformly and accurately coat fine-diameter nano-copper particles onto the surface of copper bumps in hybrid bonding to repair surface defects of copper bumps and form high-quality nano-copper films, thereby improving the bonding quality rate of hybrid bonding and assisting in achieving low-temperature hybrid bonding has become the research focus of many researchers. Summary of the Invention

[0003] In view of the above defects, the purpose of the present invention is to propose a method for printing nano-copper assisted hybrid bonding process to solve the problems of copper bumps prone to defects, poor bonding effect and high bonding temperature in the current mainstream hybrid bonding.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] A method for printing a nano-copper assisted hybrid bonding process comprises the following steps:

[0006] S1. Clean the surface of the chip to be bonded and perform pretreatment to prepare for bonding;

[0007] S2, identifying surface defects and position information of copper bumps on the surface to be bonded;

[0008] S3, printing fine-diameter nano-copper particles prepared by an electrospark ablation device onto the surface of the copper bump to repair the dishing defects, achieve surface flatness of the copper bump, and form a nano-copper film to assist low-temperature bonding;

[0009] S4, aligning and contacting the printed chip with a bonding machine and then performing micro-heating to achieve pre-bonding of hybrid bonding;

[0010] S5. Introduce inert protective gas to heat and perform low-temperature mixed bonding.

[0011] Preferably, in step S1, the chip substrate is made of silicon, glass or organic material, and the chip substrate is cleaned and then pre-treated.

[0012] Preferably, the pretreatment is to perform an acid wash treatment on the chip bonding surface, followed by a surface plasma activation treatment to facilitate the subsequent bonding process;

[0013] The pickling reagent used in the pretreatment is any one or more of formic acid, acetic acid, and citric acid, and the gas used in the plasma activation is one or more of argon and nitrogen.

[0014] Preferably, after pre-treatment, the surface flatness of the chip substrate is Ra≤0.2 nm, so that the silicon dioxide layer can be pre-bonded.

[0015] Furthermore, the method for repairing dished defects is to identify the morphological information and position information of the concave defect on the surface of the copper bump through the optical detection mechanism in the printing repair device, and then use the nozzle printing technology of the printing device to accurately print the nano-copper particles prepared by the electrospark device to fill the defect, flatten the copper bump to achieve defect repair and form a layer of nano-copper film to assist in low-temperature sintering.

[0016] Furthermore, the voltage adjustment range of the high-voltage electrostatic output device is 0-2KV, the current adjustment range is 0-20mA, and the diameter of the prepared nano-copper particles is 0-10nm;

[0017] The inert gas is one or more of helium, argon, hydrogen and nitrogen. The inert gas is introduced during bonding heating to protect the nano copper from oxidation.

[0018] Preferably, the diameter of the dry aerosol nozzle is 0.01um-10um, and the thickness of the nano copper film that can be printed using the dry aerosol nozzle is 1-100nm;

[0019] The heating method is to heat the back of the upper and lower bonded chips with a heating plate, and the upper and lower heating plates can be heated independently;

[0020] The temperature range of the micro-heating during bonding and sintering is 0-120° C., the temperature range of the heating is 0-200° C., and the maximum heating rate during heating is 10° C. / min.

[0021] Preferably, the method adopts an AOI optical inspection device, including an optical inspection machine, wherein the inner cavity of the AOI optical inspection machine is provided with a positioning mechanism, wherein the positioning mechanism includes a first motor, the first motor is fixedly connected to the AOI optical inspection machine, the output shaft of the first motor is fixedly installed with a one-way threaded rod, the surface of the one-way threaded rod is threadedly connected with an adjusting screw block, the top of the adjusting screw block is fixedly installed with an adjusting plate, one end of the adjusting plate is fixedly installed with a positioning frame, a first electric push rod is fixedly installed on one side of the inner cavity of the positioning frame, the output end of the first electric push rod is fixedly installed with a connecting plate, one side of the connecting plate is rotatably connected to the first clamping plate through a bearing, a rotating box is fixedly installed on the other side of the inner cavity of the positioning frame, a second motor is fixedly installed on the top of one side of the inner cavity of the rotating box, a driving gear is fixedly installed on the output shaft of the second motor, a transmission rod is rotatably connected to the bottom of one side of the inner cavity of the rotating box through a bearing, a driven gear is fixedly installed on the surface of the transmission rod, and a second clamping plate is fixedly installed on one end of the transmission rod;

[0022] A jig mechanism is provided between the first clamping plate and the second clamping plate, the jig mechanism comprising a lower hollow plate, the top of the lower hollow plate being movably connected to the upper hollow plate via a hinge, and the inner cavities of the lower hollow plate and the upper hollow plate are both provided with positioning grooves;

[0023] The inner cavity of the AOI optical inspection machine is provided with a three-axis manipulator, the three-axis manipulator is installed above the positioning frame, and the working end of the three-axis manipulator is installed with a nozzle.

[0024] Preferably, a detection head is provided on the top of the AOI optical inspection machine, and a display is provided on the front of the AOI optical inspection machine;

[0025] A guide slider is fixedly installed at the bottom of the adjusting screw block, and a guide slot is provided in the inner cavity of the AOI optical inspection machine;

[0026] A locating bearing is fixedly installed on one side of the inner cavity of the AOI optical inspection machine, and the locating bearing is rotatably connected to the one-way threaded rod.

[0027] One of the above technical solutions includes the following beneficial effects: the present invention uses the nozzle printing technology of the printing device to accurately deposit fine-diameter nano-copper particles into the dish-shaped defect area of ​​the copper bump to repair surface depressions, thereby ensuring the flatness and integrity of the bonding interface and providing a basis for high-quality hybrid bonding; the present invention's method for printing nano-copper-assisted hybrid bonding process is different from the current mainstream hybrid bonding method. Fine-diameter nano-metal particles prepared by electrospark ablation are directly printed onto the surface of the copper bump to form a thin film-assisted sintering bond, which greatly reduces the temperature required for bonding; compared with the mainstream low-temperature hybrid bonding method, the present invention's method for printing nano-copper-assisted hybrid bonding process directly prints nano-copper particles through a nozzle, without the need for additional masks and complex pretreatment steps, reducing process links and significantly reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a workflow diagram for printing nano-copper particles to assist hybrid bonding in the present invention;

[0029] Figure 2 It is a partial structural diagram of the hybrid bonding of the present invention;

[0030] Figure 3 This is a diagram of the pre-bonded bonding structure of the present invention;

[0031] Figure 4 This is a diagram of the bonding structure of the present invention;

[0032] Figure 5 Schematic diagram of the structure of the AOI optical inspection device of the present invention;

[0033] Figure 6 This is a schematic diagram of the left side structure of the positioning mechanism of the AOI optical inspection device of the present invention;

[0034] Figure 7 This is a schematic diagram of the internal structure of the rotating box of the AOI optical inspection device of the present invention;

[0035] Figure 8 Schematic diagram of the new jig structure of the AOI optical inspection device of the present invention

[0036] Figure 9 This is a schematic diagram of the lower hollow plate structure of the AOI optical inspection device of the present invention.

[0037] Among them: optical inspection machine 1, positioning mechanism 4, first motor 401, one-way threaded rod 402, adjusting screw block 403, adjusting plate 404, positioning frame 405, first electric push rod 406, connecting plate 407, first clamping plate 408, second motor 410, driving gear 411, transmission rod 412, driven gear 413, second clamping plate 414, three-axis manipulator 5, and jig mechanism 6. DETAILED DESCRIPTION

[0038] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0039] like Figure 1-4 As shown, a method for printing nano-copper assisted hybrid bonding process includes the following steps:

[0040] S1. Clean the surface of the chip to be bonded and perform pretreatment to prepare for bonding;

[0041] S2, identifying surface defects and position information of copper bumps on the surface to be bonded;

[0042] S3, printing fine-diameter nano-copper particles prepared by an electrospark ablation device onto the surface of the copper bump to repair the dishing defects, achieve surface flatness of the copper bump, and form a nano-copper film to assist low-temperature bonding;

[0043] S4, aligning and contacting the printed chip with a bonding machine and then performing micro-heating to achieve pre-bonding of hybrid bonding;

[0044] S5. Introduce inert protective gas to heat and perform low-temperature mixed bonding.

[0045] The present invention discloses a method for printing a nano-copper-assisted hybrid bonding process. The method uses a nozzle printing technology of a printing device to precisely deposit fine-diameter nano-copper particles onto a dish-shaped defect area of ​​a copper bump to repair surface depressions, thereby ensuring the flatness and integrity of the bonding interface and providing a basis for high-quality hybrid bonding. The present invention discloses a method for printing a nano-copper-assisted hybrid bonding process. Unlike the current mainstream hybrid bonding method, the method uses fine-diameter nano-metal particles prepared by electrospark ablation to be directly printed onto the surface of the copper bump to form a thin film-assisted sintering bond, which greatly reduces the temperature required for bonding. Compared with the mainstream low-temperature hybrid bonding method, the present invention discloses a method for printing a nano-copper-assisted hybrid bonding process. The method directly prints nano-copper particles through a nozzle, without the need for additional mask plates and complex pre-processing steps (such as mask production, material coating adjustment, etc.), thereby reducing process links and significantly reducing processing costs.

[0046] Wherein, in step S1, the chip substrate is made of silicon, glass or organic material, and the chip substrate is cleaned and pre-treated.

[0047] Pretreatment can improve chip bonding strength and reliability, and also enhance the stability of the bonding process.

[0048] In addition, the pretreatment is to perform an acid wash treatment on the chip bonding surface, followed by a surface plasma activation treatment to facilitate the subsequent bonding process;

[0049] The pickling reagent used in the pretreatment is any one or more of formic acid, acetic acid, and citric acid, and the gas used in the plasma activation is one or more of argon and nitrogen.

[0050] Surface plasma activation treatment introduces active groups and increases surface energy, thereby making the chip surface have stronger adsorption and wettability to the bonding material, which is conducive to the uniform spreading and good adhesion of the bonding material on the chip surface, thereby improving the bonding quality and reliability.

[0051] In addition, after pre-treatment, the surface flatness of the chip substrate is Ra≤0.2 nm, so that the silicon dioxide layer can be pre-bonded.

[0052] Beneficial effects: The low-roughness copper bump surface can provide a larger actual contact area, reduce interface voids, and enhance the diffusion bonding strength between metals, thereby improving the bonding quality between the copper bump and the docking metal material to improve the mechanical bonding force and bonding uniformity; the reduced roughness of the silicon oxide layer (for example, Ra≤0.2nm) enables the two layers of material to be in close contact during the pre-bonding process, reduces interface voids, ensures reliability in the initial stage of bonding, and avoids local stress concentration caused by uneven morphology, thereby improving the long-term reliability of the bonded joint.

[0053] In addition, the method for repairing dished defects is to identify the morphological information and position information of the concave defect on the surface of the copper bump through the optical detection mechanism in the printing repair device, and then use the nozzle printing technology of the printing device to accurately print the nano-copper particles prepared by the electrospark device to fill the defect, flatten the copper bump to achieve defect repair and form a layer of nano-copper film to assist in low-temperature sintering.

[0054] The repair effects of the repaired copper bump surface defects include: complete filling of dished defects, flattening of concave areas, and elimination of oxidation points, so that the copper bump surface has a structure and performance similar to that of the original copper bump.

[0055] In addition, the voltage adjustment range of the high-voltage electrostatic output device is 0-2KV, the current adjustment range is 0-20mA, and the diameter of the prepared nano-copper particles is 0-10nm;

[0056] The inert gas is one or more of helium, argon, hydrogen and nitrogen. The inert gas is introduced during bonding heating to protect the nano copper from oxidation.

[0057] In addition, the diameter of the dry aerosol nozzle is 0.01um-10um, and the thickness of the nano copper film that can be printed using the dry aerosol nozzle is 1-100nm;

[0058] Thinner nanocopper films can quickly fill surface defects and provide minimal surface roughness, facilitating material contact during subsequent bonding and reducing the required bonding temperature. Thicker nanocopper films offer higher material coverage and filling capacity, effectively eliminating voids caused by uneven surface topography and ensuring the integrity and uniformity of the bonding interface. For thin films, the high surface energy of nanocopper particles allows for rapid sintering at low temperatures, making them suitable for low-temperature bonding applications on sensitive substrates. Thicker copper films have greater diffusion capabilities, forming a denser metal layer after sintering, improving the mechanical strength and electrical conductivity of the bonded joint.

[0059] The heating method is to heat the back of the upper and lower bonded chips with a heating plate, and the upper and lower heating plates can be heated independently;

[0060] The temperature range of the micro-heating during bonding and sintering is 0-120° C., the temperature range of the heating is 0-200° C., and the maximum heating rate during heating is 10° C. / min.

[0061] As a supplement to the above techniques, Figure 2-6The method adopts an AOI optical inspection device, including an optical inspection machine 1, wherein the inner cavity of the AOI optical inspection machine 1 is provided with a positioning mechanism 4, wherein the positioning mechanism 4 includes a first motor 401, wherein the first motor 401 is fixedly connected to the AOI optical inspection machine 1, wherein the output shaft of the first motor 401 is fixedly mounted with a one-way threaded rod 402, wherein the surface of the one-way threaded rod 402 is threadedly connected with an adjusting screw block 403, wherein the top of the adjusting screw block 403 is fixedly mounted with an adjusting plate 404, wherein one end of the adjusting plate 404 is fixedly mounted with a positioning frame 405, and a first electric push rod 406 is fixedly mounted on one side of the inner cavity of the positioning frame 405. , the output end of the first electric push rod 406 is fixedly mounted with a connecting plate 407, one side of the connecting plate 407 is rotatably connected to the first clamping plate 408 through a bearing, the other side of the inner cavity of the positioning frame 405 is fixedly mounted with a rotating box 409, the top of the inner cavity of the rotating box 409 is fixedly mounted with a second motor 410, the output shaft of the second motor 410 is fixedly mounted with a driving gear 411, the bottom of the inner cavity of the rotating box 409 is rotatably connected to a transmission rod 412 through a bearing, a driven gear 413 is fixedly mounted on the surface of the transmission rod 412, and one end of the transmission rod 412 is fixedly mounted with a second clamping plate 414;

[0062] A jig mechanism 6 is provided between the first clamping plate 408 and the second clamping plate 414. The jig mechanism 6 includes a lower hollow plate 601. The top of the lower hollow plate 601 is movably connected to an upper hollow plate 602 via a hinge. The inner cavities of the lower hollow plate 601 and the upper hollow plate 602 are both provided with positioning grooves 603.

[0063] The inner cavity of the AOI optical inspection machine 1 is provided with a three-axis manipulator 5 , which is installed above the positioning frame 405 , and a nozzle is installed at the working end of the three-axis manipulator 5 .

[0064] The device controls the extension of the first electric push rod 406 to push the first clamping plate 408 to move. The first clamping plate 408 and the second clamping plate 414 can be used to clamp the jig mechanism. By turning on the second motor 410, the jig mechanism 6 can be driven to rotate, thereby facilitating the inspection of the other side of the circuit board inside the jig mechanism; after the inspection, the nozzle on the three-axis robot 5 prints fine-diameter nano-copper particles onto the surface of the copper bump to repair the dish-shaped defect.

[0065] The top of the AOI optical inspection machine 1 is provided with a detection head 2, and the front of the AOI optical inspection machine 1 is provided with a display 3;

[0066] A guide slider is fixedly installed at the bottom of the adjusting screw block 403, and a guide slot is provided in the inner cavity of the AOI optical inspection machine 1;

[0067] A positioning bearing is fixedly installed on one side of the inner cavity of the AOI optical inspection machine 1, and the positioning bearing is rotatably connected to the one-way threaded rod 402.

[0068] The guide slider and the guide slot are used together to guide the adjusting screw block 403 so that the adjusting screw block 403 is stable when moving. The positioning bearing positions the one-way threaded rod 402 so that the one-way threaded rod 402 is stable and prevents it from tilting.

[0069] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A method for printing nano-copper assisted hybrid bonding process, characterized in that, The following steps are involved: S1. Clean the surface of the chip to be bonded and perform pretreatment to prepare for bonding; S2, identifying surface defects and position information of copper bumps on the surface to be bonded; S3, printing fine-diameter nano-copper particles prepared by an electrospark ablation device onto the surface of the copper bump to repair the dishing defects, achieve surface flatness of the copper bump, and form a nano-copper film to assist low-temperature bonding; S4, aligning and contacting the printed chip with a bonding machine and then performing micro-heating to achieve pre-bonding of hybrid bonding; S5, introducing inert protective gas to heat and perform low-temperature hybrid bonding; The method for repairing dished defects is to identify the morphological and positional information of the concave defect on the surface of the copper bump through the optical detection mechanism in the printing repair device, and then use the nozzle printing technology of the printing device to accurately print the nano-copper particles prepared by the electrospark device to fill the defect, flatten the copper bump to achieve defect repair and form a layer of nano-copper film to assist in low-temperature sintering.

2. The method for printing nano-copper assisted hybrid bonding process according to claim 1, characterized in that In step S1, the substrate of the chip is silicon, glass or organic material, and the substrate of the chip is cleaned and pre-treated.

3. The method for printing nano-copper assisted hybrid bonding process according to claim 2, characterized in that: The pretreatment is to perform an acid wash treatment on the chip bonding surface, followed by a surface plasma activation treatment to facilitate the subsequent bonding process; The pickling reagent used in the pretreatment is any one or more of formic acid, acetic acid, and citric acid, and the gas used in the plasma activation is one or more of argon and nitrogen.

4. The method for printing nano-copper assisted hybrid bonding process according to claim 1, characterized in that: After pretreatment, the surface flatness of the substrate of the chip is Ra≤0.2 nm, so that the silicon dioxide layer can be pre-bonded.

5. The method for printing nano-copper assisted hybrid bonding process according to claim 1, characterized in that: The voltage adjustment range of the high-voltage electrostatic output device is 0-2KV, the current adjustment range is 0-20mA, and the diameter of the prepared nano-copper particles is 0-10nm; The inert protective gas is one or more of helium, argon, hydrogen and nitrogen. The inert gas is introduced during bonding heating to protect the nano-copper from oxidation.

6. The method for printing nano-copper assisted hybrid bonding process according to claim 1, characterized in that: The diameter of the dry aerosol nozzle is 0.01um-10um, and the thickness of the nano copper film that can be printed using the dry aerosol nozzle is 1-100nm; The heating method is to heat the back of the upper and lower bonded chips with a heating plate, and the upper and lower heating plates can be heated independently; During bonding and sintering, the temperature range of the micro-heating is 0-120° C., the temperature range of the heating is 0-200° C., and the maximum heating rate during heating is 10° C. / min.

7. The method for printing nano-copper assisted hybrid bonding process according to claim 6, characterized in that: The method adopts an AOI optical inspection machine, an inner cavity of the AOI optical inspection machine is provided with a positioning mechanism, the positioning mechanism includes a first motor, the first motor is fixedly connected to the AOI optical inspection machine, the output shaft of the first motor is fixedly installed with a one-way threaded rod, the surface of the one-way threaded rod is threadedly connected with an adjusting screw block, the top of the adjusting screw block is fixedly installed with an adjusting plate, one end of the adjusting plate is fixedly installed with a positioning frame, one side of the inner cavity of the positioning frame is fixedly installed with a first electric push rod, the output end of the first electric push rod is fixedly installed with a connecting plate, one side of the connecting plate is rotatably connected to the first clamping plate through a bearing, a rotating box is fixedly installed on the other side of the inner cavity of the positioning frame, a second motor is fixedly installed on the top of one side of the inner cavity of the rotating box, a driving gear is fixedly installed on the output shaft of the second motor, a transmission rod is rotatably connected to the bottom of one side of the inner cavity of the rotating box through a bearing, a driven gear is fixedly installed on the surface of the transmission rod, and a second clamping plate is fixedly installed on one end of the transmission rod; A jig mechanism is provided between the first clamping plate and the second clamping plate, the jig mechanism comprising a lower hollow plate, the top of the lower hollow plate being movably connected to the upper hollow plate via a hinge, and the inner cavities of the lower hollow plate and the upper hollow plate are both provided with positioning grooves; The inner cavity of the AOI optical inspection machine is provided with a three-axis manipulator, the three-axis manipulator is installed above the positioning frame, and the working end of the three-axis manipulator is installed with a nozzle.

8. The method for printing nano-copper assisted hybrid bonding process according to claim 7, characterized in that: The top of the AOI optical inspection machine is provided with a detection head, and the front of the AOI optical inspection machine is provided with a display; A guide slider is fixedly installed at the bottom of the adjusting screw block, and a guide slot is provided in the inner cavity of the AOI optical inspection machine; A locating bearing is fixedly installed on one side of the inner cavity of the AOI optical inspection machine, and the locating bearing is rotatably connected to the one-way threaded rod.

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