Method for printing nano-copper to assist mixed bonding process

Abstract

The invention discloses a method for printing nano-copper to assist a hybrid bonding process. The method comprises the following steps: S1, cleaning the surface of a chip to be bonded, and then carrying out pretreatment preparation for bonding; s2, identifying surface defects and position information of the copper bumps on the to-be-bonded surface; s3, printing small-diameter nano-copper particles prepared by an electric spark ablation device to the surface of the copper bump to repair a dish-shaped defect so as to realize surface leveling of the copper bump, and forming a layer of nano-copper film to assist low-temperature bonding; s4, performing alignment matching contact on the printed chip by using a bonding machine, and then performing micro-heating to realize pre-bonding of hybrid bonding; and S5, inert protective gas is introduced for heating, and low-temperature mixed bonding is carried out. The invention aims to provide a method for printing nano-copper to assist a mixed bonding process, and solves the problems of poor bonding effect and high bonding temperature of copper bumps in current mainstream mixed bonding.

Description

Technical Field

[0001] The 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 develop towards high density, miniaturization and high performance, the requirements for electronic packaging technology are increasing. Reliable interconnection between chips and substrates is the key to electronic packaging, and traditional welding methods usually rely on tin-based solders. However, tin-based solders have many limitations, such as high-temperature operation may damage sensitive components, prone to thermal fatigue, electromigration and other problems. In addition, some solders contain lead, which does not meet the requirements of environmental regulations. Hybrid bonding technology achieves high-strength bonding by combining mechanical and chemical bonding, and its application potential is huge. However, in the hybrid bonding process, the quality of the copper bump surface plays a vital role in the bonding performance. In practical applications, there are often local depressions of dish-shaped defects on the surface of copper bumps, which lead to problems such as incomplete bonding contact and reduced mechanical properties of the joints. In recent years, nanometal materials have attracted attention in bonding technology due to their high surface energy and good low-temperature sintering characteristics. These particles can be densely sintered at a lower temperature to form a connection interface with high conductivity and high mechanical strength. 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, comprising the following steps:

[0006] S1, cleaning the surface of the chip to be bonded and pre-treating it to prepare for bonding;

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

[0008] S3, printing the fine-diameter nano-copper particles prepared by the electric spark ablation device onto the surface of the copper bump to repair the dish-shaped defects, achieve surface flatness of the copper bump and form a layer of 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 use an acid wash treatment on the chip bonding surface, followed by a surface plasma activation treatment for the subsequent bonding treatment;

[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 pretreatment, the chip substrate surface flatness Ra≤0.2 nm, so that the silicon dioxide layer can be pre-bonded.

[0015] Furthermore, the method for repairing dish-shaped 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 electric spark device to fill the defect and flatten the copper bump to repair the defect 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, the 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 with a 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 with 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 comprises a lower hollow plate, the top of the lower hollow plate is movably connected to an 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 a nozzle is installed at the working end of the three-axis manipulator.

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

[0025] A guide slide block is fixedly installed at the bottom of the adjusting screw block, and a guide slide groove 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 the surface depression, thereby ensuring the flatness and integrity of the bonding interface and providing a basis for high-quality hybrid bonding; the method of printing nano-copper assisted hybrid bonding process of the present invention is different from the current mainstream hybrid bonding method. The 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 method of printing nano-copper assisted hybrid bonding process of the present invention directly prints nano-copper particles through a nozzle, without the need for additional mask plates and complex pretreatment steps, reducing process links and significantly reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The working flow chart of printing nano copper particles to assist hybrid bonding of the present invention;

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

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

[0031] Figure 4 It is a structural diagram after bonding of the present invention;

[0032] Figure 5 It is a structural schematic diagram of the AOI optical inspection device of the present invention;

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

[0034] Figure 7 It 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] Fig. 9 It 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] Embodiments of the present invention are described in detail below, examples of which 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 only used to explain the present invention, and cannot be understood as limiting the present invention.

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

[0040] S1, cleaning the surface of the chip to be bonded and pre-treating it to prepare for bonding;

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

[0042] S3, printing the fine-diameter nano-copper particles prepared by the electric spark ablation device onto the surface of the copper bump to repair the dish-shaped defects, achieve surface flatness of the copper bump and form a layer of 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 method of printing nano-copper assisted hybrid bonding process of 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 the surface depression, thereby ensuring the flatness and integrity of the bonding interface and providing a basis for high-quality hybrid bonding; the method of printing nano-copper assisted hybrid bonding process of the present invention is different from the current mainstream hybrid bonding method, and the fine-diameter nano-metal particles prepared by electric spark 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 method of printing nano-copper assisted hybrid bonding process of the present invention directly prints nano-copper particles through a nozzle, without the need for additional mask plates and complex pretreatment steps (such as mask production, material coating adjustment, etc.), 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 help improve chip bonding strength and reliability, and also improve 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 for the subsequent bonding treatment;

[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, so that the chip surface has stronger adsorption and wettability to the bonding material, which is beneficial 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 pretreatment, 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 roughness of the silicon oxide layer is reduced (for example, Ra≤0.2nm), so that the two layers of material can be in close contact during the pre-bonding process, reducing interface voids, ensuring the reliability of the initial stage of bonding, and avoiding local stress concentration caused by uneven morphology, thereby improving the long-term reliability of the bonded joint.

[0053] In addition, the method for repairing dish-shaped 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 electric spark device to fill the defect and flatten the copper bump to repair the defect 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 dish-shaped 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 nano copper films can quickly fill surface defects and provide less surface roughness, which is beneficial to the material contact during subsequent bonding and reduces the required bonding temperature; thicker nano copper films provide higher material coverage and filling capacity, effectively eliminating gaps caused by uneven surface morphology, and ensuring the integrity and uniformity of the bonding interface. For thin films, the high surface energy of nano copper particles can be quickly sintered at low temperatures, which is suitable for low-temperature bonding applications of sensitive substrates; thicker copper films have stronger diffusion capabilities, and after sintering, they form a denser metal layer, which improves the mechanical strength and conductivity of the bonding 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 mentioned 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 comprises a first motor 401, wherein the first motor 401 is fixedly connected to the AOI optical inspection machine 1, wherein a one-way threaded rod 402 is fixedly installed on the output shaft of the first motor 401, wherein an adjusting screw block 403 is threadedly connected to the surface of the one-way threaded rod 402, wherein an adjusting plate 404 is fixedly installed on the top of the adjusting screw block 403, wherein a positioning frame 405 is fixedly installed on one end of the adjusting plate 404, wherein a first electric push rod 406 is fixedly installed on one side of the inner cavity of the positioning frame 405 A connecting plate 407 is fixedly installed at the output end of the first electric push rod 406, and a first clamping plate 408 is rotatably connected to one side of the connecting plate 407 through a bearing, and a rotating box 409 is fixedly installed on the other side of the inner cavity of the positioning frame 405, and a second motor 410 is fixedly installed on the top of one side of the inner cavity of the rotating box 409, and a driving gear 411 is fixedly installed on the output shaft of the second motor 410, and a transmission rod 412 is rotatably connected to the bottom of one side of the inner cavity of the rotating box 409 through a bearing, and a driven gear 413 is fixedly installed on the surface of the transmission rod 412, and a second clamping plate 414 is fixedly installed on one end of the transmission rod 412;

[0062] A jig mechanism 6 is disposed between the first clamping plate 408 and the second clamping plate 414, and the jig mechanism 6 includes a lower hollow plate 601, and the top of the lower hollow plate 601 is movably connected to an upper hollow plate 602 through a hinge, and 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 first electric push rod 406 to extend and 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 detection of the other side of the circuit board inside the jig mechanism. After the detection, the nozzle on the three-axis manipulator 5 prints fine-diameter nano-copper particles onto the surface of the copper bump to repair the dish-shaped defect.

[0065] Wherein, a detection head 2 is arranged on the top of the AOI optical detection machine 1, and a display 3 is arranged on the front of the AOI optical detection machine 1;

[0066] A guide slide block is fixedly installed at the bottom of the adjusting screw block 403, and a guide slide groove 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 principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods 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, cleaning the surface of the chip to be bonded and pre-treating it to prepare for bonding; S2, identifying surface defects and position information of copper bumps on the surface to be bonded; S3, printing the fine-diameter nano-copper particles prepared by the electric spark ablation device onto the surface of the copper bump to repair the dish-shaped defects, achieve surface flatness of the copper bump and form a layer of 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. Introduce inert protective gas to heat and perform low-temperature mixed bonding.

2. The method for printing nano-copper assisted hybrid bonding process according to claim 1, characterized in that ,In step S1, the chip substrate is made of silicon, glass or organic material, and ,the chip substrate 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 treatment; 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 chip substrate is Ra≤0.2nm, 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 method for repairing dish-shaped 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 electric spark 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.

6. 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 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.

7. 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; 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.

8. The method for printing nano-copper assisted hybrid bonding process according to claim 5, characterized in that: The method adopts an AOI optical detection device, including an optical detection machine, wherein the inner cavity of the AOI optical detection machine is provided with a positioning mechanism, wherein the positioning mechanism comprises a first motor, wherein the first motor is fixedly connected to the AOI optical detection machine, wherein a one-way threaded rod is fixedly installed on the output shaft of the first motor, an adjusting screw block is threadedly connected on the surface of the one-way threaded rod, an adjusting plate is fixedly installed on the top of the adjusting screw block, a positioning frame is fixedly installed on one end of the adjusting plate, a first electric push rod is fixedly installed on one side of the inner cavity of the positioning frame, a connecting plate is fixedly installed on the output end of the first electric push rod, a first clamping plate is rotatably connected to one side of the connecting 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 comprises a lower hollow plate, the top of the lower hollow plate is movably connected to an 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 a nozzle is installed at the working end of the three-axis manipulator.

9. The method for printing nano-copper assisted hybrid bonding process according to claim 8, 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 slide block is fixedly installed at the bottom of the adjusting screw block, and a guide slide groove 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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