A flux cleaning device and cleaning method in an advanced package structure

Abstract

The application relates to the technical field of semiconductor manufacturing, in particular to a flux cleaning device and a cleaning method in an advanced packaging structure. A wafer carrier is arranged in a cavity, a heating device is arranged outside the cavity, a carbon dioxide supply unit, a saponification liquid supply unit, a vacuumizing device and a nitrogen supply device are connected to one side of the cavity, a pressure sensor and a temperature sensor are arranged at the upper end of the cavity, one end of a waste pipe is arranged at the lower end of the cavity, an electric conductivity instrument is arranged on the waste pipe, the other end of the waste pipe is connected to a separation kettle, and the outlet of the separation kettle is connected to a high-pressure circulating pump and the saponification liquid supply unit. Compared with the prior art, the application realizes the limit penetration of micro-nano scale gaps, dissolves the flux and realizes the dead angle-free cleaning, strengthens the efficiency of the cleaning chemical reaction and realizes the lossless drying of the chip structure.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically to a flux cleaning device and cleaning method for advanced packaging structures. Background Technology

[0002] In the field of advanced semiconductor packaging, the rapid development of technologies such as flip-chip and 2.5D / 3D integration has presented unprecedented challenges to the flux cleaning process after micro-bump interconnects. As the bump pitch continues to shrink to below 20 micrometers, the gap between the chip and the substrate or interposer has entered the 10-micrometer or even smaller scale, with a significantly increased aspect ratio. Performing efficient and non-destructive cleaning within such extremely narrow gaps with very high aspect ratios has become a key technological bottleneck restricting the yield and reliability of advanced packaging.

[0003] Currently, vacuum negative pressure cleaning technology has been widely studied and applied, solving the "cavitation" effect caused by liquid surface tension. However, the problems of vacuum negative pressure cleaning are mainly reflected in two aspects: First, insufficient cleaning effectiveness. In extremely narrow and deep gaps, even under negative pressure, the cleaning fluid has extremely high flow resistance due to its inherent surface tension and viscosity, resulting in very low efficiency in the effective replacement and removal of contaminants (such as flux residue), easily forming cleaning dead zones. Second, the process control window is extremely narrow, posing a risk of damage. To facilitate the entry of the cleaning fluid into the gap, a large pressure differential or a rapid rate of pressure change may be required, which can generate significant fluid shear forces on the micro-bumps, posing a potential threat of deformation, cracking, or interface delamination to the fragile micron-scale bump structure.

[0004] Therefore, the industry urgently needs a flux cleaning device and cleaning method for advanced packaging structures to overcome the limitations of liquid physicochemical properties and meet the requirements of high yield and high reliability for different microbump sizes in advanced packaging technologies. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention provides a flux cleaning device in an advanced packaging structure, comprising a cavity, wherein a wafer stage is provided inside the cavity, and a heating device surrounds the outside of the cavity. A carbon dioxide supply unit, a saponification liquid supply unit, a vacuum device, and a nitrogen supply device are respectively connected to one side of the cavity. A pressure sensor and a temperature sensor are provided at the upper end of the cavity, and a waste discharge pipe is provided at the lower end of the cavity. A conductivity meter is provided on the waste discharge pipe, and the other end of the waste discharge pipe is connected to a separation vessel. The outlet of the separation vessel is respectively connected to a high-pressure circulating pump and a saponification liquid supply unit. The high-pressure circulating pump is connected to one end of a first filter, and the other end of the first filter is connected to one end of a secondary filter through a control valve. The other end of the secondary filter is connected to the cavity.

[0006] The carbon dioxide supply unit includes a carbon dioxide cylinder, a cryogenic storage tank, and a high-pressure pump. The carbon dioxide cylinder is connected to one end of the cryogenic storage tank via a control valve, and the other end of the cryogenic storage tank is connected to one end of the high-pressure pump. The other end of the high-pressure pump is connected to the cavity via a control valve.

[0007] The saponification liquid supply unit includes a storage tank, a precision metering pump, and a second filter. The storage tank is connected to one end of the precision metering pump, the other end of the precision metering pump is connected to one end of the second filter, and the other end of the second filter is connected to the cavity through a control valve.

[0008] The flux cleaning device is connected to the PLC control unit via signal transmission, and the PLC control unit is connected to the host computer via communication.

[0009] A flux cleaning method for an advanced packaging structure, employing the flux cleaning device described in the advanced packaging structure, includes the following steps: S1, a wafer is mounted on a wafer carrier, forming a sealed cavity; S2, a vacuum is drawn into the cavity, and the cavity interior and the wafer are heated to 40-60°C, with real-time monitoring of the pressure and temperature within the cavity; S3, a saponification solution, occupying 1-5% of the cavity volume, is injected using a precision metering pump; S4, liquid carbon dioxide is pumped into the cavity using a high-pressure pump, while simultaneously increasing the temperature and pressure, adjusting the temperature-pressure coupling stage to bring the liquid carbon dioxide into a supercritical state and form a homogeneous supercritical mixture with the saponification solution. S5. Start the high-pressure circulating pump to continuously circulate the supercritical mixed fluid inside and outside the chamber at a flow rate of 1-5 L / min. This allows the supercritical fluid to penetrate into the micro-gap of the chip. The fluid flow generates shear force within the micro-gap, creating a "pumping effect" that continuously peels off and carries away the decomposed flux residue from the chip surface and micro-gap. S6. Supercritical carbon dioxide rich in contaminants enters the separation vessel for separation. The contaminants are precipitated by depressurization and then recycled after purification. S7. Depressurize the chamber to atmospheric pressure, turning the supercritical carbon dioxide into a gaseous state. High-purity nitrogen is then introduced for purging to achieve wafer drying. S8. Remove the cleaned and dried wafer.

[0010] The temperature-pressure coupling adjustment stage in S4 specifically includes: S41, setting the temperature of the normal stage to 45-65℃ and the corresponding internal pressure of the cavity to 20-30MPa, the temperature of the low temperature stage to 40-45℃ and the corresponding internal pressure of the cavity to 15-20MPa, and the temperature of the high temperature stage to 65-75℃ and the corresponding internal pressure of the cavity to 30-50MPa; S42, the default is the normal stage, which can be adjusted to the low temperature stage or the high temperature stage as needed.

[0011] Compared with existing technologies, this invention uses supercritical mixed fluid cleaning technology to solve the problem of ineffective removal of flux residues inside micro-gap spaces of 10 micrometers and below in advanced packaging structures. It achieves ultimate penetration, flux dissolution and thorough cleaning of micro-nano scale gaps, enhances the efficiency of cleaning chemical reactions, utilizes the controllable phase change characteristics of supercritical fluids to achieve non-destructive drying of chip structures, and utilizes the recyclable nature of supercritical carbon dioxide to achieve green manufacturing. Attached Figure Description

[0012] Figure 1 A schematic diagram of the flux cleaning device; Figure 2 Flowchart of flux cleaning method; Figure 3 A graph showing the relationship between temperature and pressure in supercritical carbon dioxide. See Figure 1 1. Cavity; 2. Wafer stage; 3. Heating device; 4. Vacuum device; 5. Nitrogen supply device; 6. Pressure sensor; 7. Temperature sensor; 8. Waste discharge pipe; 9. Conductivity meter; 10. Separation vessel; 11. High-pressure circulating pump; 12. Filter 1; 13. Secondary filter; 14. Carbon dioxide cylinder; 15. Cryogenic storage tank; 16. High-pressure pump; 17. Liquid storage tank; 18. Precision metering pump; 19. Filter 2; 20. PLC control device; 21. Host computer. Detailed Implementation

[0013] The present invention will now be further described with reference to the accompanying drawings.

[0014] like Figure 1 A flux cleaning device in an advanced packaging structure includes a cavity 1. The cavity 1 has a wafer stage 2 inside and a heating device 3 surrounding the outside of the cavity 1. One side of the cavity 1 is connected to a carbon dioxide supply unit, a saponification liquid supply unit, a vacuum device 4, and a nitrogen supply device 5. The upper end of the cavity 1 is equipped with a pressure sensor 6 and a temperature sensor 7. The lower end of the cavity 1 is equipped with a waste discharge pipe 8. A conductivity meter 9 is installed on the waste discharge pipe 8. The other end of the waste discharge pipe 8 is connected to a separation vessel 10. The outlet of the separation vessel 10 is connected to a high-pressure circulating pump 11 and a saponification liquid supply unit. The high-pressure circulating pump 11 is connected to one end of a filter 12. The other end of the filter 12 is connected to one end of a secondary filter 13 through a control valve. The other end of the secondary filter 13 is connected to the cavity 1.

[0015] The carbon dioxide supply unit includes a carbon dioxide cylinder 14, a cryogenic storage tank 15, and a high-pressure pump 16. The carbon dioxide cylinder 14 is connected to one end of the cryogenic storage tank 15 through a control valve. The other end of the cryogenic storage tank 15 is connected to one end of the high-pressure pump 16. The other end of the high-pressure pump 16 is connected to the cavity 1 through a control valve.

[0016] The saponification liquid supply unit includes a storage tank 17, a precision metering pump 18, and a second filter 19. The storage tank 17 is connected to one end of the precision metering pump 18, and the other end of the precision metering pump 18 is connected to one end of the second filter 19. The other end of the second filter 19 is connected to the cavity 1 through a control valve.

[0017] The flux cleaning device is connected to the PLC control device 20 via signal, and the PLC control device 20 is connected to the host computer 21 via communication.

[0018] like Figure 2 A flux cleaning method for an advanced packaging structure, employing the flux cleaning device described in the advanced packaging structure, includes the following steps: S1, the wafer is loaded onto a wafer carrier 2, forming a sealed space with a cavity 1; S2, the cavity 1 is evacuated to remove as much air as possible, preventing oxygen and other gases from affecting the solubility and reaction environment of liquid carbon dioxide. The cavity 1 and the wafer are heated to 40-60°C, and the pressure and temperature inside the cavity 1 are monitored in real time. The temperature must be higher than the critical temperature of carbon dioxide (31.1°C) to prepare it for entering the supercritical state; S3, a saponification solution, accounting for 1-5% of the cavity volume, is injected through a precision metering pump 18. The saponification solution is weakly alkaline and has good compatibility with supercritical carbon dioxide; S4, liquid carbon dioxide is pumped into the cavity using a high-pressure pump 16. The liquid carbon dioxide mixes with the saponification agent to form a synergistic cleaning system. Simultaneously, the temperature and pressure are increased, exceeding the critical pressure of 7.38 MPa. Figure 3In the temperature-pressure coupling adjustment stage, liquid carbon dioxide enters the supercritical state and forms a homogeneous supercritical mixed fluid with the saponification liquid. This supercritical mixed fluid possesses extremely strong penetration and dissolving capabilities. Supercritical carbon dioxide acts as both solvent and carrier, uniformly dispersing and transporting the effective components of the saponification liquid deep into the micro-gap. S5: Start the high-pressure circulating pump 11, continuously circulating the supercritical mixed fluid inside and outside the cavity at a flow rate of 1-5 L / min. This allows the supercritical fluid to penetrate into the chip's micro-gap. The fluid flow generates shear force within the micro-gap, creating a "pumping effect," continuously stripping and carrying away the decomposed flux residue from the chip surface and micro-gap. The fluid continuously flows within the chip gaps, dynamically penetrating, reacting, and extracting contaminants. The cleaning time is controlled according to requirements. S6: Contaminant-rich supercritical carbon dioxide enters separation vessel 10 for separation. Depressurization causes contaminants to precipitate, drastically reducing the solubility of supercritical carbon dioxide. Flux residue precipitates due to the sudden drop in solubility and deposits at the bottom of the separation vessel. The purified supercritical carbon dioxide can then be recompressed and cooled for reuse. S7: Chamber 1 is depressurized to atmospheric pressure, and the system pressure is restored to atmospheric pressure at a controllable rate. Supercritical carbon dioxide transforms from a supercritical fluid into a gas, without liquid phase formation, thus completely eliminating surface tension and capillary forces. During depressurization, high-purity nitrogen can be introduced for purging to help remove residual trace gaseous contaminants, achieving wafer drying. S8: The cleaned and dried wafer is removed.

[0019] The temperature-pressure coupling adjustment stage in S4 specifically includes: S41, setting the temperature of the normal stage to 45-65℃ and the corresponding internal pressure to 20-30MPa, the temperature of the low-temperature stage to 40-45℃ and the corresponding internal pressure to 15-20MPa, which is suitable for heat-sensitive chip structures, and the temperature of the high-temperature stage to 65-75℃ and the corresponding internal pressure to 30-50MPa, which is suitable for removing extremely stubborn polymer residues, using high temperature to enhance the saponification reaction rate and contaminant vapor pressure, improve the density and solubility of supercritical carbon dioxide, and maintain sufficient density; S42, the default is the normal stage, which can be adjusted to the low-temperature stage or the high-temperature stage as needed.

[0020] Saponification solutions can be water-based, such as those containing organic amines (e.g., monoethanolamine), which are environmentally friendly and suitable for most water-soluble fluxes; semi-aqueous saponification solutions, such as those containing organic solvents (e.g., alcohols) and water, which have better solubility for certain rosin residues; and solvent-based saponification solutions, such as those with organic solvents as the main component, which are used for cleaning specific synthetic fluxes.

[0021] The flux cleaning method in the advanced packaging structure of the present invention will be explained in detail below with specific examples.

[0022] S1. Load the flip-chip wafer with flux residue onto the wafer stage and seal the cavity. S2. Evacuate the cavity to ensure an absolute pressure <5 kPa and preheat to 40°C, monitoring the pressure and temperature in real time. S3. Inject 3% (by volume) of water-based saponification solution into the cavity using a precision metering pump. S4. Pump liquid carbon dioxide into the cavity using a high-pressure pump while simultaneously increasing the temperature and pressure. Temperature-Pressure Coupling Stage: During the normal operation phase, control and monitor the temperature within the range of 45-65°C and the pressure within the range of 20-30 MPa to bring the liquid carbon dioxide into a supercritical state, forming a homogeneous supercritical mixture with the saponification solution. S5. Start the high-pressure circulation pump to continuously circulate the supercritical mixture inside and outside the cavity at a flow rate of 1-5 L / min, maintaining the cleaning time at 20-60 minutes. The supercritical fluid penetrates into the micro-gap of the chip, causing a saponification reaction in the saponification solution, while the supercritical carbon dioxide is responsible for mass transfer and extraction. S6. Supercritical carbon dioxide rich in contaminants is introduced into the separation vessel. The pressure is reduced to 5-10 MPa to allow the contaminants to precipitate. The purified supercritical carbon dioxide can be recycled. S7. The chamber is depressurized to atmospheric pressure at a rate of 0.5-1 MPa / min. The supercritical carbon dioxide is directly vaporized, achieving liquid-free and tension-free drying of the wafer. S8. The wafer is unloaded, and the cleaned and dried wafer is removed.

[0023] This invention employs a supercritical carbon dioxide and saponified liquid mixed fluid cleaning technology to solve the long-standing technical challenge of effectively removing flux residues inside 10-micron and nano-scale micro-gap structures in advanced packaging structures. Utilizing the high diffusion coefficient and low viscosity of supercritical carbon dioxide, the mixed fluid penetrates deep into the micro-nano scale gaps, fundamentally addressing the industry pain point of cleaning media "not being able to penetrate," achieving comprehensive coverage within the micro-gap. Through the shear force generated by the supercritical fluid combined with dynamic circulation, a continuous "pumping effect" is formed, enhancing the bidirectional mass transfer between reactant supply and product discharge, breaking through the mass transfer bottleneck of "slow reaction and inability to discharge products," and significantly improving the efficiency of the cleaning chemical reaction. Furthermore, by utilizing the controllable phase transition characteristic of supercritical fluid directly changing from a supercritical state to a gaseous state during depressurization, non-destructive drying of the chip structure is achieved, avoiding problems such as structural collapse and bridging deformation caused by traditional drying processes. By leveraging the superior solubility of supercritical carbon dioxide for non-polar organic matter, and in conjunction with the chemical decomposition of polar components by saponification liquid, deep purification of all components of complex flux is achieved. Using carbon dioxide as the main cleaning medium, coupled with a recyclable process design, it aligns with the trend of green manufacturing in the semiconductor industry.

Claims

1. A flux cleaning device in an advanced packaging structure, comprising a cavity, characterized in that: The cavity (1) is equipped with a wafer stage (2) inside, and a heating device (3) surrounds the outside of the cavity (1). A carbon dioxide supply unit, a saponification liquid supply unit, a vacuum device (4) and a nitrogen supply device (5) are connected to one side of the cavity (1). A pressure sensor (6) and a temperature sensor (7) are provided at the upper end of the cavity (1). A waste discharge pipe (8) is provided at the lower end of the cavity (1). A conductivity meter (9) is provided on the waste discharge pipe (8). The other end of the waste discharge pipe (8) is connected to a separation vessel (10). The outlet of the separation vessel (10) is connected to a high-pressure circulating pump (11) and a saponification liquid supply unit. The high-pressure circulating pump (11) is connected to one end of a filter (12). The other end of the filter (12) is connected to one end of a secondary filter (13) through a control valve. The other end of the secondary filter (13) is connected to the cavity (1).

2. The flux cleaning device in an advanced packaging structure according to claim 1, characterized in that: The carbon dioxide supply unit includes a carbon dioxide cylinder (14), a cryogenic storage tank (15), and a high-pressure pump (16). The carbon dioxide cylinder (14) is connected to one end of the cryogenic storage tank (15) through a control valve. The other end of the cryogenic storage tank (15) is connected to one end of the high-pressure pump (16). The other end of the high-pressure pump (16) is connected to the cavity (1) through a control valve.

3. The flux cleaning device in an advanced packaging structure according to claim 1, characterized in that: The saponification liquid supply unit includes a storage tank (17), a precision metering pump (18), and a second filter (19). The storage tank (17) is connected to one end of the precision metering pump (18), and the other end of the precision metering pump (18) is connected to one end of the second filter (19). The other end of the second filter (19) is connected to the cavity (1) through a control valve.

4. The flux cleaning device in an advanced packaging structure according to claim 1, characterized in that: The flux cleaning device is connected to the PLC control device (20) via signal, and the PLC control device (20) is connected to the host computer (21) via communication.

5. A flux cleaning method in an advanced packaging structure, characterized in that, The flux cleaning apparatus in the advanced packaging structure as described in any one of claims 1-4 is used. The cleaning method includes: S1, loading the wafer onto the wafer stage (2), and forming a sealed space in the cavity (1); S2, evacuating the cavity (1) and heating the inside of the cavity (1) and the wafer to 40-60°C, while monitoring the pressure and temperature inside the cavity (1) in real time; S3, injecting a saponification liquid accounting for 1-5% of the cavity volume through a precision metering pump (18); S4, using a high-pressure pump (16) to pump liquid carbon dioxide into the cavity, while simultaneously raising the temperature and pressure, adjusting the temperature-pressure coupling stage, so that the liquid carbon dioxide enters the supercritical state and forms a uniform supercritical state with the saponification liquid. S5. Start the high-pressure circulating pump (11) to make the supercritical mixed fluid circulate continuously inside and outside the cavity at a flow rate of 1-5L / min, so that the supercritical fluid penetrates into the chip micro gap. The fluid flow generates shear force in the micro gap, forming a "pump suction effect", which continuously peels off and carries away the decomposed flux residue from the chip surface and micro gap; S6. Supercritical carbon dioxide rich in pollutants enters the separation vessel (10) for separation. The pollutants are precipitated by depressurization and then recycled after purification; S7. Depressurize the cavity (1) to normal pressure, and the supercritical carbon dioxide becomes gaseous. High-purity nitrogen is introduced for purging to achieve wafer drying; S8. Take out the cleaned and dried wafer.

6. The flux cleaning method in an advanced packaging structure according to claim 5, characterized in that: The temperature-pressure coupling adjustment stage in S4 specifically includes: S41, setting the temperature of the normal stage to 45-65℃ and the corresponding internal pressure of the cavity to 20-30MPa, the temperature of the low temperature stage to 40-45℃ and the corresponding internal pressure of the cavity to 15-20MPa, and the temperature of the high temperature stage to 65-75℃ and the corresponding internal pressure of the cavity to 30-50MPa; S42, the default is the normal stage, which can be adjusted to the low temperature stage or the high temperature stage as needed.

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