Vacuum negative pressure type flux cleaning device and cleaning method

Abstract

The present application relates to the technical field of semiconductor manufacturing, in particular to a vacuum negative pressure type flux cleaning device and a cleaning method. One side of the cavity is provided with a wafer transmission window, the center of the cavity is provided with a rotating mechanism, the lower end of the rotating mechanism is connected with a motor, the upper end of the rotating mechanism is connected with a wafer carrier, the lower end of the wafer carrier is provided with a vibrating device, the upper end of the wafer carrier is provided with an optical fiber sensor and a wafer temperature sensor, the lower end of the cavity is provided with a waste pipe, one side of the waste pipe is provided with an electric conductivity meter and an optical bubble sensor, the upper side of the wafer carrier is provided with a swing arm, the swing arm is provided with a plurality of nozzles, the upper end of the cavity is provided with a vacuum interface, a nitrogen gas interface, a negative pressure sensor and a cavity temperature sensor. Compared with the prior art, the defects of the traditional vacuum negative pressure cleaning in the differential pressure control precision and temperature adaptability are solved; under the premise of ensuring micro-bump zero damage, the flux cleaning efficiency in the narrow gap advanced packaging structure is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, specifically to a vacuum negative pressure flux cleaning device and cleaning method. Background Technology

[0002] As semiconductor packaging technology continues to evolve towards higher density and higher integration, advanced packaging structures such as flip-chip and 2.5D / 3D integration have become key paths to improve system performance. In these structures, micro-bumps are the core for achieving high-density electrical interconnects, and flux is indispensable for ensuring soldering reliability in reflow soldering and thermocompression bonding processes. After soldering, thoroughly removing residual flux is a necessary step to ensure the long-term reliability of devices, as residues can cause a series of serious problems such as electromigration, corrosion, underfill voids, and insulation failure.

[0003] Currently, the mainstream method for flux cleaning in the industry is vacuum negative pressure cleaning technology. Its principle is to create a vacuum environment, reduce the gas pressure within the gap, and use the pressure difference to drive the cleaning fluid to penetrate and expel the gas, achieving comprehensive wetting. However, this technology still has some problems in practical applications. For example, insufficient vacuum (pressure difference) leads to incomplete cleaning. The effectiveness of vacuum negative pressure cleaning is highly dependent on an effective pressure difference; insufficient pressure difference cannot effectively break up "cavitation," and the cleaning fluid cannot fully penetrate deep into the micro-gap. Especially for gaps with complex structures and large depth-to-width ratios, the internal flow and replacement of the cleaning fluid are insufficient, resulting in "dead zones" with low contaminant exchange efficiency. To achieve thorough cleaning, longer circulation times or multiple complex process sequences are often required, increasing process complexity and variability. Furthermore, excessive pressure differential or transient changes can damage the protrusions. Achieving efficient and non-destructive cleaning is extremely dependent on precise control of vacuum. If the vacuum (pressure differential) is too high or the pressure changes too rapidly, it may generate severe fluid impact or "water hammer" effect in the micro gap. The resulting shear force will impose excessive load on the micro protrusions. For micro protrusions that are constantly shrinking in size and have fragile structures, there is a risk of deformation, neck cracking or interface peeling. The process window is extremely narrow, and the requirements for equipment stability and process formula repeatability are extremely high.

[0004] Therefore, there is an urgent need in the field for a cleaning device and method that can more accurately optimize and control the pressure difference to meet the requirements of high yield and high reliability for different microbump sizes in packaging technology. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention provides a vacuum negative pressure flux cleaning device, comprising a cavity, the cavity being hollow inside, a wafer transfer window on one side of the cavity, a rotating mechanism at the center of the cavity, a motor connected to the lower end of the rotating mechanism, a wafer stage connected to the upper end of the rotating mechanism, a vibration device at the lower end of the wafer stage, an optical fiber sensor and a wafer temperature sensor at the upper end of the wafer stage, a waste discharge pipe at the lower end of the cavity, a conductivity meter and an optical bubble sensor on one side of the waste discharge pipe, a swing arm above the wafer stage, a plurality of nozzles on the swing arm, and a vacuum interface, a nitrogen interface, a negative pressure sensor and a cavity temperature sensor at the upper end of the cavity. The vacuum interface is connected to a vacuum pumping device, and the nitrogen interface is connected to a gas supply device.

[0006] The vacuum negative pressure flux cleaning device is connected to a PLC control device, and the PLC control device is connected to a host computer.

[0007] A vacuum negative pressure flux cleaning method, employing the aforementioned vacuum negative pressure flux cleaning device, includes the following steps: S1, a wafer is mounted on a wafer stage; S2, a low-speed vacuum is applied, with the vacuum device evacuating the wafer to a pressure drop rate of 0.5~2 kPa / s within the range of -20kPa~-80kPa; S3, a motor drives the wafer on the wafer stage to rotate at 10~100 r / min, adjusting the temperature-pressure dynamic coupling stage, a nozzle sprays saponifying liquid onto the wafer surface, and a swing arm drives the nozzle to reciprocate, ensuring that the saponifying liquid covers the entire wafer, dynamically monitoring the temperature, saturated vapor pressure, and actual working pressure within the cavity, ensuring that the actual working pressure is always higher than the saturated vapor pressure at the current temperature; S4, an optical bubble sensor on the waste discharge pipe detects the size and number of bubbles in the discharged liquid in real time, determining that the number of bubbles is less than [a certain value] every 10 seconds within a continuous 30 seconds. When there is one bubble and the bubble is less than 10 micrometers, it is considered that the gas in the cavity has been basically eliminated and the next step can be carried out; otherwise, repeat step S3. S5, oscillation and pressure holding: the vibration device provides low-frequency pressure oscillation according to the set period, so that a "pumping effect" is generated in the gap. S6, repeat steps S3-S5. The conductivity meter on the waste discharge pipe detects the ion concentration of the discharged liquid in real time. When the conductivity value does not change for more than 30 seconds, it is determined that the cleaning is completed and the oscillation stops. S7, slow pressure increase: the pressure increase rate is 0.2~1kPa / s, and the gas supply device backfills nitrogen into the cavity to achieve wafer drying without liquid residue. S8, unload the wafer.

[0008] The dynamic coupling stage of adjusting the temperature and pressure of the saponification liquid in S3 specifically includes: S31, setting the outlet temperature of the saponification liquid in the low-temperature stage to 40~60℃ and the corresponding working pressure in the cavity to -80kPa~-50kPa, and the outlet temperature of the saponification liquid in the high-temperature stage to 60~80℃ and the corresponding working pressure in the cavity to -50kPa~-20kPa; S32, adjusting to the low-temperature stage or the high-temperature stage as needed.

[0009] In S3, ensuring that the actual working pressure is always higher than the saturated vapor pressure at the current temperature is specifically defined as P_work > P_sat(T) + ΔP_margin; P_work represents the actual working pressure of the cavity, P_sat(T) represents the saturated vapor pressure of the saponifying liquid at temperature T, and ΔP_margin represents the set pressure safety margin value. The saturated vapor pressure is calculated using the Antoine equation, and the calculation formula includes the following: P_sat(T) = 10 × (AB / (T+C)); P_sat(T) represents the saturated vapor pressure of the saponifying liquid at temperature T, where T represents the temperature of the saponifying liquid; A, B, and C represent Antoine constants, specifically the physical property parameters of the relevant components in the saponifying liquid formula.

[0010] The low-frequency pressure oscillation of S4 has a frequency of 0.1–1 Hz and an oscillation amplitude of 1–5 kPa.

[0011] Compared with existing technologies, the present invention features a temperature-pressure dynamic coupling stage adjustment and intelligent control system, which solves the defects of traditional vacuum negative pressure cleaning in terms of differential pressure control accuracy and temperature adaptability; and improves the flux cleaning efficiency in narrow-gap advanced packaging structures while ensuring zero damage to micro-bumps. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the cleaning device. Figure 2 Here is a flowchart of the cleaning method; Figure 3 Pressure and temperature control diagram for vacuum negative pressure flux cleaning method for 80-micron micro-bumps; Figure 4 Pressure and temperature control diagram for a vacuum negative pressure flux cleaning method for 40-micron micro-bumps; Figure 5 Pressure and temperature control diagram for a vacuum negative pressure flux cleaning method for 20-micron micro-bumps; See Figure 11. Cavity; 2. Wafer transfer window; 3. Rotation mechanism; 4. Motor; 5. Wafer stage; 6. Fiber optic sensor; 7. Wafer temperature sensor; 8. Swing arm; 9. Nozzle; 10. Waste discharge pipe; 11. Conductivity meter; 12. Optical bubble sensor; 13. Vacuum interface; 14. Nitrogen interface; 15. Negative pressure sensor; 16. Cavity temperature sensor; 17. PLC control device; 18. Host computer; 19. Vibration device. Detailed Implementation

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

[0014] like Figure 1 A vacuum negative pressure flux cleaning device includes a cavity 1, which is hollow inside. A wafer transfer window 2 is provided on one side of the cavity 1. A rotating mechanism 3 is provided at the center of the cavity 1. A motor 4 is connected to the lower end of the rotating mechanism 3. A wafer stage 5 is connected to the upper end of the rotating mechanism 3. A vibration device 19 is provided at the lower end of the wafer stage 5. An optical fiber sensor 6 and a wafer temperature sensor 7 are provided at the upper end of the wafer stage 5. A waste discharge pipe 10 is provided at the lower end of the cavity 1. A conductivity meter 11 and an optical bubble sensor 12 are provided on one side of the waste discharge pipe 10. A swing arm 8 is provided above the wafer stage 5. Several nozzles 9 are provided on the swing arm 8. A vacuum interface 13, a nitrogen interface 14, a negative pressure sensor 15, and a cavity temperature sensor 16 are provided at the upper end of the cavity 1. The vacuum interface 13 is connected to a vacuum pumping device, and the nitrogen interface 14 is connected to a gas supply device.

[0015] The vacuum negative pressure flux cleaning device is connected to the PLC control device 17 via signal connection, and the PLC control device 17 is connected to the host computer 18 via communication connection.

[0016] A vacuum negative pressure flux cleaning method, employing a vacuum negative pressure flux cleaning device, includes: S1, loading the wafer onto a wafer carrier 5; S2, low-speed vacuuming, with the vacuuming device operating at 0.5~2... The vacuum is drawn to a pressure drop rate of kPa / s within the range of -20kPa to -80kPa to avoid sudden pressure changes causing impact loads on the micro-bumps; S3, the motor 4 drives the wafer on the wafer stage 5 to rotate at 10~100r / min, adjusting the temperature-pressure dynamic coupling stage. The nozzle 9 sprays saponification liquid onto the wafer surface, and the swing arm 8 drives the nozzle 9 to reciprocate to ensure that the saponification liquid covers the entire wafer. The temperature, saturated vapor pressure and actual working pressure in the cavity 1 are dynamically monitored to ensure that the actual working pressure is always higher than the saturated vapor pressure at the current temperature, preventing the cleaning liquid from boiling and keeping the saponification liquid in a stable liquid state; S4, the optical bubble sensor 12 on the waste discharge pipe 10 detects the size and number of bubbles in the discharged liquid in real time. If the number of bubbles is less than 1 every 10 seconds and the bubbles are smaller than 10 micrometers within 30 seconds, it is considered that the gas in the cavity 1 has been basically eliminated and entered the cavity. Next, repeat step S3 if the condition is reversed; S5, oscillate and maintain pressure. The vibration device 19 provides low-frequency pressure oscillation according to the set period. Through periodic micro-pressure change, a "pumping effect" is generated in the micro gap, which strengthens the stripping and replacement of flux residue by the cleaning fluid; S6, repeat steps S3-S5. The injected fresh saponified liquid uses the concentration difference to "push" the dissolved contaminants out from the depth of the gap and continuously replenishes the active ingredients to ensure the reaction continues. The conductivity meter 11 on the waste discharge pipe 10 detects the ion concentration of the discharged liquid in real time. When the conductivity value does not change for more than 30 seconds, it is determined that the cleaning is completed and the oscillation stops; S7, slowly increase the pressure. The pressure increase rate is 0.2~1kPa / s. The gas supply device backfills nitrogen into the cavity 1. Combined with its inert gas characteristics, it suppresses the "water hammer effect" and achieves wafer drying without liquid residue; S8, unload the wafer.

[0017] The S3 stage of adjusting the dynamic coupling of saponification liquid temperature and pressure specifically includes: S31, setting the saponification liquid outlet temperature in the low-temperature stage to 40~60℃ and the corresponding working pressure in the cavity to -80kPa~-50kPa. At this time, the chemical activity of the saponification liquid is low, and a higher negative pressure is used. The main advantage is to utilize the huge pressure difference to drive the saponification liquid to penetrate into the micro-gap and break the cavitation. In the high-temperature stage, the saponification liquid outlet temperature is 60~80℃ and the corresponding working pressure in the cavity is -50kPa~-20kPa. The high temperature significantly increases the rate of the saponification reaction. At this time, the negative pressure is appropriately reduced (i.e., the absolute pressure of the cavity is increased) to ensure cleaning efficiency while significantly reducing the risk of saponification liquid boiling due to pressure control deviation. Furthermore, pressure oscillation under lower negative pressure is safer for structural impact. S32, adjust to either the low-temperature stage or the high-temperature stage as needed.

[0018] In S3, ensuring that the actual working pressure is always higher than the saturated vapor pressure at the current temperature is specifically defined as P_work > P_sat(T) + ΔP_margin; P_work represents the actual working pressure of the cavity, P_sat(T) represents the saturated vapor pressure of the saponifying liquid at temperature T, and ΔP_margin represents the set pressure safety margin value. ΔP_margin is used to cope with instantaneous pressure fluctuations, leaving sufficient margin to avoid violent vaporization of the saponifying liquid and ensure cleaning effect. The saturated vapor pressure is calculated using the Antoine equation, and the calculation formula includes the following: P_sat(T) = 10 × (AB / (T+C)); P_sat(T) represents the saturated vapor pressure of the saponifying liquid at temperature T, where T represents the temperature of the saponifying liquid; A, B, and C represent Antoine constants, specifically the physical property parameters of the relevant components in the saponifying liquid formula.

[0019] The low-frequency pressure oscillation of S4 has a frequency of 0.1–1 Hz and an oscillation amplitude of 1–5 kPa.

[0020] S5 ensures that the cleaning fluid in the micro-gap flows slowly and tends to remain still under a stable negative pressure environment, forming a laminar boundary layer. Low-frequency pressure oscillation is applied to enhance fluid exchange, continuously renew the interface and accelerate product removal. At the same time, it enhances the interfacial shear force and inhibits the secondary deposition of flux in the "dead zone". Fresh saponified liquid fills the gap for the first time under negative pressure and capillary action, reacts with the flux to dissolve surface residues and penetrates to the deep layer, breaking down the structure of contaminants.

[0021] The vacuum negative pressure flux cleaning method of the present invention will be explained in detail below with specific examples. Example

[0022] like Figure 3 A 12-inch wafer with 80-micron microbumps and an interposer is placed on the wafer stage through the transfer port, and the transfer port is closed. The cavity is slowly evacuated to -80 kPa at a rate of 2 kPa / s for 1 minute. The wafer is rotated at 100 r / min, and a nozzle is swung to spray a saponifying solution at approximately 40°C onto the wafer surface. This process is continued for 5 minutes to wet the wafer. Simultaneously, the number of bubbles in the waste liquid on the waste discharge pipe is monitored. If the number of bubbles is less than 1 per 10 seconds and there are no bubbles of 10 microns or larger within 30 seconds, then the process continues. While rotating the wafer, oscillating the nozzle, and spraying the saponification liquid, the internal pressure of the cavity is periodically changed, with a single amplitude of 5 kPa for 10 minutes. At the same time, the ion concentration in the waste liquid is detected by a conductivity meter. When the conductivity value no longer changes significantly within 30 seconds, it is determined that the cleaning is complete. The negative pressure cavity is slowly pressurized to atmospheric pressure at a rate of 3 kPa / s. During the pressurization process, nitrogen gas is sprayed into the cavity to dry the internal structure of the chip. After the process is completed, the wafer transfer port is opened, and the wafer interposer is removed from the wafer stage. Example

[0023] like Figure 4 A 12-inch wafer with 40-micron microbumps and an interposer is placed on the wafer stage through the transfer port, and the transfer port is closed. The cavity is slowly evacuated to -80 kPa at a rate of 2 kPa / s for 1 minute. The wafer is rotated at 100 r / min, and the nozzle is oscillated to spray a saponification solution at approximately 40°C onto the wafer surface. This process is continued for 5 minutes to wet the wafer. Then, the saponification solution outlet temperature is adjusted to 60°C, and the corresponding working pressure in the cavity is set to -40 kPa. Simultaneously, the number of bubbles in the waste liquid on the waste discharge pipe is monitored. If the number of bubbles is less than 1 per 10 seconds for 30 consecutive seconds, the process is complete. And there are no bubbles of 10 micrometers or larger in size; then, while continuously rotating the wafer, swinging the nozzle and spraying the saponification liquid, the internal pressure of the cavity is periodically changed, and the single amplitude of 3 kPa is oscillated for 10 minutes; at the same time, the ion concentration in the waste liquid is detected by a conductivity meter. When the conductivity value no longer changes significantly within 30 seconds, it is determined to be clean; the negative pressure cavity is slowly pressurized to atmospheric pressure at a rate of 2 kPa / s. During the pressurization process, nitrogen gas is sprayed into the cavity to dry the internal structure of the chip; after the end, the wafer transfer port is opened and the wafer interposer is taken out from the wafer stage. Example

[0024] like Figure 5 A 12-inch wafer with 20-micron microbumps and an interposer is placed on the wafer stage through the transfer port, and the transfer port is closed. The cavity is slowly evacuated to -80 kPa at a rate of 2 kPa / s for 1 minute. The wafer is rotated at 100 r / min, and the nozzle is oscillated to spray a saponification solution at approximately 40°C onto the wafer surface. This process is continued for 5 minutes to wet the wafer. Then, the saponification solution outlet temperature is adjusted to 80°C, and the corresponding working pressure in the cavity is set to -20 kPa. Simultaneously, the number of bubbles in the waste liquid on the waste discharge pipe is monitored. If the number of bubbles is less than 1 per 10 seconds for 30 consecutive seconds, the process is complete. And there are no bubbles of 10 micrometers or larger; while continuously rotating the wafer, oscillating the nozzle and spraying the saponification liquid, the internal pressure of the cavity is periodically changed, and the oscillation amplitude is 1 kPa; this is continued for 10 minutes; at the same time, the ion concentration in the waste liquid is detected by a conductivity meter. When the conductivity value no longer changes significantly within 30 seconds, it is determined to be clean; the negative pressure cavity is slowly pressurized to atmospheric pressure at a rate of 1 kPa / s. During the pressurization process, nitrogen gas is sprayed into the cavity to dry the internal structure of the chip; after the end, the wafer transfer port is opened, and the wafer interposer is taken out from the wafer stage.

Claims

1. A vacuum negative pressure flux cleaning device, comprising a cavity, characterized in that: The cavity (1) is hollow inside. A wafer transfer window (2) is provided on one side of the cavity (1). A rotating mechanism (3) is provided in the center of the cavity (1). A motor (4) is connected to the lower end of the rotating mechanism (3). A wafer stage (5) is connected to the upper end of the rotating mechanism (3). A vibration device (19) is provided at the lower end of the wafer stage (5). An optical fiber sensor (6) and a wafer temperature sensor (7) are provided at the upper end of the wafer stage (5). A waste discharge pipe (10) is provided at the lower end of the cavity (1). A conductivity meter (11) and an optical bubble sensor (12) are provided on one side of the waste discharge pipe (10). A swing arm (8) is provided above the wafer stage (5). Several nozzles (9) are provided on the swing arm (8). A vacuum interface (13), a nitrogen interface (14), a negative pressure sensor (15), and a cavity temperature sensor (16) are provided at the upper end of the cavity (1). The vacuum interface (13) is connected to a vacuum pumping device, and the nitrogen interface (14) is connected to a gas supply device.

2. The vacuum negative pressure flux cleaning device according to claim 1, characterized in that: The vacuum negative pressure flux cleaning device is connected to the PLC control device (17) via signal, and the PLC control device (17) is connected to the host computer (18) via communication.

3. A vacuum negative pressure flux cleaning method, characterized in that, The vacuum negative pressure flux cleaning device as described in any one of claims 1-2 is used. The cleaning method includes: S1, the wafer is loaded onto the wafer stage (5); S2, low-speed vacuuming, the vacuuming device evacuates to the range of -20kPa to -80kPa at a pressure drop rate of 0.5~2 kPa / s; S3, the motor (4) drives the wafer on the wafer stage 5 to rotate at 10~100r / min, adjusts the temperature-pressure dynamic coupling stage, the nozzle (9) sprays saponification liquid onto the wafer surface, the swing arm (8) drives the nozzle (9) to reciprocate, ensuring that the saponification liquid covers the entire wafer, dynamically monitors the temperature, saturated vapor pressure and actual working pressure in the cavity (1), and ensures that the actual working pressure is always higher than the saturated vapor pressure at the current temperature; S4, the optical bubble sensor (12) on the waste discharge pipe (10) detects the size and number of bubbles in the discharged liquid in real time, and determines the number of bubbles every 10 seconds within 30 seconds. When the amount is less than 1 and the bubble is less than 10 micrometers, it is considered that the gas in the cavity (1) has been basically eliminated and the next step is started. Otherwise, step S3 is repeated. S5, oscillation and pressure holding, the vibration device (19) provides low-frequency pressure oscillation according to the set period, so that the gap produces a "pumping effect". S6, repeat steps S3-S5, the conductivity meter (11) on the waste discharge pipe (10) detects the ion concentration of the discharged liquid in real time. When the conductivity value does not change for more than 30 seconds, it is determined that the cleaning is completed and the oscillation is stopped. S7, slow pressure increase, the pressure increase rate is 0.2~1kPa / s, the gas supply device backfills nitrogen into the cavity (1) to achieve wafer drying without liquid residue. S8, unload the wafer.

4. The vacuum negative pressure flux cleaning method according to claim 3, characterized in that: In S3, ensuring that the actual working pressure is always higher than the saturated vapor pressure at the current temperature is specifically defined as P_work > P_sat(T) + ΔP_margin; where P_work represents the actual working pressure of the cavity, P_sat(T) represents the saturated vapor pressure of the saponification liquid at temperature T, and ΔP_margin represents the set pressure safety margin. The saturated vapor pressure is calculated using the Antoine equation, and the calculation formula includes the following: P_sat(T) = 10 × (AB / (T+C)); P_sat(T) represents the saturated vapor pressure of the saponification liquid at temperature T, where T represents the temperature of the saponification liquid; A, B, and C represent Antoine constants, specifically the physical property parameters of the relevant components in the saponification liquid formulation.

5. The vacuum negative pressure flux cleaning method according to claim 3, characterized in that: The dynamic coupling stage of adjusting the temperature and pressure of the saponification liquid in S3 specifically includes: S31, setting the outlet temperature of the saponification liquid in the low-temperature stage to 40~60℃ and the corresponding working pressure in the cavity to -80kPa~-50kPa, and the outlet temperature of the saponification liquid in the high-temperature stage to 60~80℃ and the corresponding working pressure in the cavity to -50kPa~-20kPa; S32, adjusting to the low-temperature stage or the high-temperature stage as needed.

6. The vacuum negative pressure flux cleaning method according to claim 3, characterized in that: The low-frequency pressure oscillation of S4 has a frequency of 0.1–1 Hz and an oscillation amplitude of 1–5 kPa.

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